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diff --git a/doc/sphinx/_static/CoqNotations.ttf b/doc/sphinx/_static/CoqNotations.ttf Binary files differnew file mode 100644 index 0000000000..da8f2850df --- /dev/null +++ b/doc/sphinx/_static/CoqNotations.ttf diff --git a/doc/sphinx/_static/UbuntuMono-Square.ttf b/doc/sphinx/_static/UbuntuMono-Square.ttf Binary files differdeleted file mode 100644 index 12b7c6d51a..0000000000 --- a/doc/sphinx/_static/UbuntuMono-Square.ttf +++ /dev/null diff --git a/doc/sphinx/_static/notations.css b/doc/sphinx/_static/notations.css index 9b7b826d58..f899945a35 100644 --- a/doc/sphinx/_static/notations.css +++ b/doc/sphinx/_static/notations.css @@ -22,10 +22,10 @@ } @font-face { /* This font has been edited to center all characters */ - font-family: 'UbuntuMono-Square'; + font-family: 'CoqNotations'; font-style: normal; font-weight: 800; - src: local('UbuntuMono-Square'), url(./UbuntuMono-Square.ttf) format('truetype'); + src: local('CoqNotations'), url(./CoqNotations.ttf) format('truetype'); } .notation .notation-sup, .notation .notation-sub { @@ -34,15 +34,15 @@ color: black; /* cursor: help; */ display: inline-block; - font-size: 0.5em; + font-size: 0.45em; font-weight: bolder; - font-family: UbuntuMono-Square, monospace; - height: 2em; + font-family: CoqNotations, monospace; + height: 2.2em; line-height: 1.6em; position: absolute; right: -1em; /* half of the width */ text-align: center; - width: 2em; + width: 2.2em; } .notation .repeat { diff --git a/doc/sphinx/addendum/extended-pattern-matching.rst b/doc/sphinx/addendum/extended-pattern-matching.rst index 64d4eddf04..1d3b661732 100644 --- a/doc/sphinx/addendum/extended-pattern-matching.rst +++ b/doc/sphinx/addendum/extended-pattern-matching.rst @@ -305,6 +305,8 @@ explicitations (as for terms 2.7.11). end). +.. _matching-dependent: + Matching objects of dependent types ----------------------------------- @@ -414,6 +416,7 @@ length, by writing I have a copy of :g:`b` in type :g:`listn 0` resp :g:`listn (S n')`. +.. _match-in-patterns: Patterns in ``in`` ~~~~~~~~~~~~~~~~~~ diff --git a/doc/sphinx/addendum/extraction.rst b/doc/sphinx/addendum/extraction.rst new file mode 100644 index 0000000000..38365e4035 --- /dev/null +++ b/doc/sphinx/addendum/extraction.rst @@ -0,0 +1,585 @@ +.. include:: ../replaces.rst + +.. _extraction: + +Extraction of programs in |OCaml| and Haskell +============================================= + +:Authors: Jean-Christophe Filliâtre and Pierre Letouzey + +We present here the |Coq| extraction commands, used to build certified +and relatively efficient functional programs, extracting them from +either |Coq| functions or |Coq| proofs of specifications. The +functional languages available as output are currently |OCaml|, Haskell +and Scheme. In the following, "ML" will be used (abusively) to refer +to any of the three. + +Before using any of the commands or options described in this chapter, +the extraction framework should first be loaded explicitly +via ``Require Extraction``, or via the more robust +``From Coq Require Extraction``. +Note that in earlier versions of Coq, these commands and options were +directly available without any preliminary ``Require``. + +.. coqtop:: in + + Require Extraction. + +Generating ML Code +------------------- + +.. note:: + + In the following, a qualified identifier `qualid` + can be used to refer to any kind of |Coq| global "object" : constant, + inductive type, inductive constructor or module name. + +The next two commands are meant to be used for rapid preview of +extraction. They both display extracted term(s) inside |Coq|. + +.. cmd:: Extraction @qualid. + + Extraction of the mentioned object in the |Coq| toplevel. + +.. cmd:: Recursive Extraction @qualid ... @qualid. + + Recursive extraction of all the mentioned objects and + all their dependencies in the |Coq| toplevel. + +All the following commands produce real ML files. User can choose to +produce one monolithic file or one file per |Coq| library. + +.. cmd:: Extraction "@file" @qualid ... @qualid. + + Recursive extraction of all the mentioned objects and all + their dependencies in one monolithic `file`. + Global and local identifiers are renamed according to the chosen ML + language to fulfill its syntactic conventions, keeping original + names as much as possible. + +.. cmd:: Extraction Library @ident. + + Extraction of the whole |Coq| library ``ident.v`` to an ML module + ``ident.ml``. In case of name clash, identifiers are here renamed + using prefixes ``coq_`` or ``Coq_`` to ensure a session-independent + renaming. + +.. cmd:: Recursive Extraction Library @ident. + + Extraction of the |Coq| library ``ident.v`` and all other modules + ``ident.v`` depends on. + +.. cmd:: Separate Extraction @qualid ... @qualid. + + Recursive extraction of all the mentioned objects and all + their dependencies, just as ``Extraction "file"``, + but instead of producing one monolithic file, this command splits + the produced code in separate ML files, one per corresponding Coq + ``.v`` file. This command is hence quite similar to + ``Recursive Extraction Library``, except that only the needed + parts of Coq libraries are extracted instead of the whole. + The naming convention in case of name clash is the same one as + ``Extraction Library``: identifiers are here renamed using prefixes + ``coq_`` or ``Coq_``. + +The following command is meant to help automatic testing of +the extraction, see for instance the ``test-suite`` directory +in the |Coq| sources. + +.. cmd:: Extraction TestCompile @qualid ... @qualid. + + All the mentioned objects and all their dependencies are extracted + to a temporary |OCaml| file, just as in ``Extraction "file"``. Then + this temporary file and its signature are compiled with the same + |OCaml| compiler used to built |Coq|. This command succeeds only + if the extraction and the |OCaml| compilation succeed. It fails + if the current target language of the extraction is not |OCaml|. + +Extraction Options +------------------- + +Setting the target language +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The ability to fix target language is the first and more important +of the extraction options. Default is ``OCaml``. + +.. cmd:: Extraction Language OCaml. +.. cmd:: Extraction Language Haskell. +.. cmd:: Extraction Language Scheme. + +Inlining and optimizations +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Since |OCaml| is a strict language, the extracted code has to +be optimized in order to be efficient (for instance, when using +induction principles we do not want to compute all the recursive calls +but only the needed ones). So the extraction mechanism provides an +automatic optimization routine that will be called each time the user +want to generate |OCaml| programs. The optimizations can be split in two +groups: the type-preserving ones (essentially constant inlining and +reductions) and the non type-preserving ones (some function +abstractions of dummy types are removed when it is deemed safe in order +to have more elegant types). Therefore some constants may not appear in the +resulting monolithic |OCaml| program. In the case of modular extraction, +even if some inlining is done, the inlined constant are nevertheless +printed, to ensure session-independent programs. + +Concerning Haskell, type-preserving optimizations are less useful +because of laziness. We still make some optimizations, for example in +order to produce more readable code. + +The type-preserving optimizations are controlled by the following |Coq| options: + +.. opt:: Extraction Optimize. + + Default is on. This controls all type-preserving optimizations made on + the ML terms (mostly reduction of dummy beta/iota redexes, but also + simplifications on Cases, etc). Turn this option off if you want a + ML term as close as possible to the Coq term. + +.. opt:: Extraction Conservative Types. + + Default is off. This controls the non type-preserving optimizations + made on ML terms (which try to avoid function abstraction of dummy + types). Turn this option on to make sure that ``e:t`` + implies that ``e':t'`` where ``e'`` and ``t'`` are the extracted + code of ``e`` and ``t`` respectively. + +.. opt:: Extraction KeepSingleton. + + Default is off. Normally, when the extraction of an inductive type + produces a singleton type (i.e. a type with only one constructor, and + only one argument to this constructor), the inductive structure is + removed and this type is seen as an alias to the inner type. + The typical example is ``sig``. This option allows disabling this + optimization when one wishes to preserve the inductive structure of types. + +.. opt:: Extraction AutoInline. + + Default is on. The extraction mechanism inlines the bodies of + some defined constants, according to some heuristics + like size of bodies, uselessness of some arguments, etc. + Those heuristics are not always perfect; if you want to disable + this feature, turn this option off. + +.. cmd:: Extraction Inline @qualid ... @qualid. + + In addition to the automatic inline feature, the constants + mentionned by this command will always be inlined during extraction. + +.. cmd:: Extraction NoInline @qualid ... @qualid. + + Conversely, the constants mentionned by this command will + never be inlined during extraction. + +.. cmd:: Print Extraction Inline. + + Prints the current state of the table recording the custom inlinings + declared by the two previous commands. + +.. cmd:: Reset Extraction Inline. + + Empties the table recording the custom inlinings (see the + previous commands). + +**Inlining and printing of a constant declaration:** + +A user can explicitly ask for a constant to be extracted by two means: + + * by mentioning it on the extraction command line + + * by extracting the whole |Coq| module of this constant. + +In both cases, the declaration of this constant will be present in the +produced file. But this same constant may or may not be inlined in +the following terms, depending on the automatic/custom inlining mechanism. + +For the constants non-explicitly required but needed for dependency +reasons, there are two cases: + + * If an inlining decision is taken, whether automatically or not, + all occurrences of this constant are replaced by its extracted body, + and this constant is not declared in the generated file. + + * If no inlining decision is taken, the constant is normally + declared in the produced file. + +Extra elimination of useless arguments +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The following command provides some extra manual control on the +code elimination performed during extraction, in a way which +is independent but complementary to the main elimination +principles of extraction (logical parts and types). + +.. cmd:: Extraction Implicit @qualid [ @ident ... @ident ]. + + This experimental command allows declaring some arguments of + `qualid` as implicit, i.e. useless in extracted code and hence to + be removed by extraction. Here `qualid` can be any function or + inductive constructor, and the given `ident` are the names of + the concerned arguments. In fact, an argument can also be referred + by a number indicating its position, starting from 1. + +When an actual extraction takes place, an error is normally raised if the +``Extraction Implicit`` declarations cannot be honored, that is +if any of the implicited variables still occurs in the final code. +This behavior can be relaxed via the following option: + +.. opt:: Extraction SafeImplicits. + + Default is on. When this option is off, a warning is emitted + instead of an error if some implicited variables still occur in the + final code of an extraction. This way, the extracted code may be + obtained nonetheless and reviewed manually to locate the source of the issue + (in the code, some comments mark the location of these remaining + implicited variables). + Note that this extracted code might not compile or run properly, + depending of the use of these remaining implicited variables. + +Realizing axioms +~~~~~~~~~~~~~~~~ + +Extraction will fail if it encounters an informative axiom not realized. +A warning will be issued if it encounters a logical axiom, to remind the +user that inconsistent logical axioms may lead to incorrect or +non-terminating extracted terms. + +It is possible to assume some axioms while developing a proof. Since +these axioms can be any kind of proposition or object or type, they may +perfectly well have some computational content. But a program must be +a closed term, and of course the system cannot guess the program which +realizes an axiom. Therefore, it is possible to tell the system +what ML term corresponds to a given axiom. + +.. cmd:: Extract Constant @qualid => @string. + + Give an ML extraction for the given constant. + The `string` may be an identifier or a quoted string. + +.. cmd:: Extract Inlined Constant @qualid => @string. + + Same as the previous one, except that the given ML terms will + be inlined everywhere instead of being declared via a ``let``. + + .. note:: + This command is sugar for an ``Extract Constant`` followed + by a ``Extraction Inline``. Hence a ``Reset Extraction Inline`` + will have an effect on the realized and inlined axiom. + +.. caution:: It is the responsibility of the user to ensure that the ML + terms given to realize the axioms do have the expected types. In + fact, the strings containing realizing code are just copied to the + extracted files. The extraction recognizes whether the realized axiom + should become a ML type constant or a ML object declaration. For example: + +.. coqtop:: in + + Axiom X:Set. + Axiom x:X. + Extract Constant X => "int". + Extract Constant x => "0". + +Notice that in the case of type scheme axiom (i.e. whose type is an +arity, that is a sequence of product finished by a sort), then some type +variables have to be given (as quoted strings). The syntax is then: + +.. cmdv:: Extract Constant @qualid @string ... @string => @string. + +The number of type variables is checked by the system. For example: + +.. coqtop:: in + + Axiom Y : Set -> Set -> Set. + Extract Constant Y "'a" "'b" => " 'a * 'b ". + +Realizing an axiom via ``Extract Constant`` is only useful in the +case of an informative axiom (of sort ``Type`` or ``Set``). A logical axiom +have no computational content and hence will not appears in extracted +terms. But a warning is nonetheless issued if extraction encounters a +logical axiom. This warning reminds user that inconsistent logical +axioms may lead to incorrect or non-terminating extracted terms. + +If an informative axiom has not been realized before an extraction, a +warning is also issued and the definition of the axiom is filled with +an exception labeled ``AXIOM TO BE REALIZED``. The user must then +search these exceptions inside the extracted file and replace them by +real code. + +Realizing inductive types +~~~~~~~~~~~~~~~~~~~~~~~~~ + +The system also provides a mechanism to specify ML terms for inductive +types and constructors. For instance, the user may want to use the ML +native boolean type instead of |Coq| one. The syntax is the following: + +.. cmd:: Extract Inductive @qualid => @string [ @string ... @string ]. + + Give an ML extraction for the given inductive type. You must specify + extractions for the type itself (first `string`) and all its + constructors (all the `string` between square brackets). In this form, + the ML extraction must be an ML inductive datatype, and the native + pattern-matching of the language will be used. + +.. cmdv:: Extract Inductive @qualid => @string [ @string ... @string ] @string. + + Same as before, with a final extra `string` that indicates how to + perform pattern-matching over this inductive type. In this form, + the ML extraction could be an arbitrary type. + For an inductive type with `k` constructors, the function used to + emulate the pattern-matching should expect `(k+1)` arguments, first the `k` + branches in functional form, and then the inductive element to + destruct. For instance, the match branch ``| S n => foo`` gives the + functional form ``(fun n -> foo)``. Note that a constructor with no + argument is considered to have one unit argument, in order to block + early evaluation of the branch: ``| O => bar`` leads to the functional + form ``(fun () -> bar)``. For instance, when extracting ``nat`` + into |OCaml| ``int``, the code to provide has type: + ``(unit->'a)->(int->'a)->int->'a``. + +.. caution:: As for ``Extract Constant``, this command should be used with care: + + * The ML code provided by the user is currently **not** checked at all by + extraction, even for syntax errors. + + * Extracting an inductive type to a pre-existing ML inductive type + is quite sound. But extracting to a general type (by providing an + ad-hoc pattern-matching) will often **not** be fully rigorously + correct. For instance, when extracting ``nat`` to |OCaml| ``int``, + it is theoretically possible to build ``nat`` values that are + larger than |OCaml| ``max_int``. It is the user's responsibility to + be sure that no overflow or other bad events occur in practice. + + * Translating an inductive type to an arbitrary ML type does **not** + magically improve the asymptotic complexity of functions, even if the + ML type is an efficient representation. For instance, when extracting + ``nat`` to |OCaml| ``int``, the function ``Nat.mul`` stays quadratic. + It might be interesting to associate this translation with + some specific ``Extract Constant`` when primitive counterparts exist. + +Typical examples are the following: + +.. coqtop:: in + + Extract Inductive unit => "unit" [ "()" ]. + Extract Inductive bool => "bool" [ "true" "false" ]. + Extract Inductive sumbool => "bool" [ "true" "false" ]. + +.. note:: + + When extracting to |OCaml|, if an inductive constructor or type has arity 2 and + the corresponding string is enclosed by parentheses, and the string meets + |OCaml|'s lexical criteria for an infix symbol, then the rest of the string is + used as infix constructor or type. + +.. coqtop:: in + + Extract Inductive list => "list" [ "[]" "(::)" ]. + Extract Inductive prod => "(*)" [ "(,)" ]. + +As an example of translation to a non-inductive datatype, let's turn +``nat`` into |OCaml| ``int`` (see caveat above): + +.. coqtop:: in + + Extract Inductive nat => int [ "0" "succ" ] "(fun fO fS n -> if n=0 then fO () else fS (n-1))". + +Avoiding conflicts with existing filenames +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +When using ``Extraction Library``, the names of the extracted files +directly depends from the names of the |Coq| files. It may happen that +these filenames are in conflict with already existing files, +either in the standard library of the target language or in other +code that is meant to be linked with the extracted code. +For instance the module ``List`` exists both in |Coq| and in |OCaml|. +It is possible to instruct the extraction not to use particular filenames. + +.. cmd:: Extraction Blacklist @ident ... @ident. + + Instruct the extraction to avoid using these names as filenames + for extracted code. + +.. cmd:: Print Extraction Blacklist. + + Show the current list of filenames the extraction should avoid. + +.. cmd:: Reset Extraction Blacklist. + + Allow the extraction to use any filename. + +For |OCaml|, a typical use of these commands is +``Extraction Blacklist String List``. + +Differences between |Coq| and ML type systems +---------------------------------------------- + +Due to differences between |Coq| and ML type systems, +some extracted programs are not directly typable in ML. +We now solve this problem (at least in |OCaml|) by adding +when needed some unsafe casting ``Obj.magic``, which give +a generic type ``'a`` to any term. + +First, if some part of the program is *very* polymorphic, there +may be no ML type for it. In that case the extraction to ML works +alright but the generated code may be refused by the ML +type-checker. A very well known example is the ``distr-pair`` +function: + +.. coqtop:: in + + Definition dp {A B:Type}(x:A)(y:B)(f:forall C:Type, C->C) := (f A x, f B y). + +In |OCaml|, for instance, the direct extracted term would be:: + + let dp x y f = Pair((f () x),(f () y)) + +and would have type:: + + dp : 'a -> 'a -> (unit -> 'a -> 'b) -> ('b,'b) prod + +which is not its original type, but a restriction. + +We now produce the following correct version:: + + let dp x y f = Pair ((Obj.magic f () x), (Obj.magic f () y)) + +Secondly, some |Coq| definitions may have no counterpart in ML. This +happens when there is a quantification over types inside the type +of a constructor; for example: + +.. coqtop:: in + + Inductive anything : Type := dummy : forall A:Set, A -> anything. + +which corresponds to the definition of an ML dynamic type. +In |OCaml|, we must cast any argument of the constructor dummy +(no GADT are produced yet by the extraction). + +Even with those unsafe castings, you should never get error like +``segmentation fault``. In fact even if your program may seem +ill-typed to the |OCaml| type-checker, it can't go wrong : it comes +from a Coq well-typed terms, so for example inductive types will always +have the correct number of arguments, etc. Of course, when launching +manually some extracted function, you should apply it to arguments +of the right shape (from the |Coq| point-of-view). + +More details about the correctness of the extracted programs can be +found in :cite:`Let02`. + +We have to say, though, that in most "realistic" programs, these problems do not +occur. For example all the programs of Coq library are accepted by the |OCaml| +type-checker without any ``Obj.magic`` (see examples below). + +Some examples +------------- + +We present here two examples of extractions, taken from the +|Coq| Standard Library. We choose |OCaml| as target language, +but all can be done in the other dialects with slight modifications. +We then indicate where to find other examples and tests of extraction. + +A detailed example: Euclidean division +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The file ``Euclid`` contains the proof of Euclidean division. +The natural numbers used there are unary integers of type ``nat``, +defined by two constructors ``O`` and ``S``. +This module contains a theorem ``eucl_dev``, whose type is:: + + forall b:nat, b > 0 -> forall a:nat, diveucl a b + +where ``diveucl`` is a type for the pair of the quotient and the +modulo, plus some logical assertions that disappear during extraction. +We can now extract this program to |OCaml|: + +.. coqtop:: none + + Reset Initial. + +.. coqtop:: all + + Require Extraction. + Require Import Euclid Wf_nat. + Extraction Inline gt_wf_rec lt_wf_rec induction_ltof2. + Recursive Extraction eucl_dev. + +The inlining of ``gt_wf_rec`` and others is not +mandatory. It only enhances readability of extracted code. +You can then copy-paste the output to a file ``euclid.ml`` or let +|Coq| do it for you with the following command:: + + Extraction "euclid" eucl_dev. + +Let us play the resulting program (in an |OCaml| toplevel):: + + #use "euclid.ml";; + type nat = O | S of nat + type sumbool = Left | Right + val sub : nat -> nat -> nat = <fun> + val le_lt_dec : nat -> nat -> sumbool = <fun> + val le_gt_dec : nat -> nat -> sumbool = <fun> + type diveucl = Divex of nat * nat + val eucl_dev : nat -> nat -> diveucl = <fun> + + # eucl_dev (S (S O)) (S (S (S (S (S O)))));; + - : diveucl = Divex (S (S O), S O) + +It is easier to test on |OCaml| integers:: + + # let rec nat_of_int = function 0 -> O | n -> S (nat_of_int (n-1));; + val nat_of_int : int -> nat = <fun> + + # let rec int_of_nat = function O -> 0 | S p -> 1+(int_of_nat p);; + val int_of_nat : nat -> int = <fun> + + # let div a b = + let Divex (q,r) = eucl_dev (nat_of_int b) (nat_of_int a) + in (int_of_nat q, int_of_nat r);; + val div : int -> int -> int * int = <fun> + + # div 173 15;; + - : int * int = (11, 8) + +Note that these ``nat_of_int`` and ``int_of_nat`` are now +available via a mere ``Require Import ExtrOcamlIntConv`` and then +adding these functions to the list of functions to extract. This file +``ExtrOcamlIntConv.v`` and some others in ``plugins/extraction/`` +are meant to help building concrete program via extraction. + +Extraction's horror museum +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Some pathological examples of extraction are grouped in the file +``test-suite/success/extraction.v`` of the sources of |Coq|. + +Users' Contributions +~~~~~~~~~~~~~~~~~~~~ + +Several of the |Coq| Users' Contributions use extraction to produce +certified programs. In particular the following ones have an automatic +extraction test: + + * ``additions`` : https://github.com/coq-contribs/additions + * ``bdds`` : https://github.com/coq-contribs/bdds + * ``canon-bdds`` : https://github.com/coq-contribs/canon-bdds + * ``chinese`` : https://github.com/coq-contribs/chinese + * ``continuations`` : https://github.com/coq-contribs/continuations + * ``coq-in-coq`` : https://github.com/coq-contribs/coq-in-coq + * ``exceptions`` : https://github.com/coq-contribs/exceptions + * ``firing-squad`` : https://github.com/coq-contribs/firing-squad + * ``founify`` : https://github.com/coq-contribs/founify + * ``graphs`` : https://github.com/coq-contribs/graphs + * ``higman-cf`` : https://github.com/coq-contribs/higman-cf + * ``higman-nw`` : https://github.com/coq-contribs/higman-nw + * ``hardware`` : https://github.com/coq-contribs/hardware + * ``multiplier`` : https://github.com/coq-contribs/multiplier + * ``search-trees`` : https://github.com/coq-contribs/search-trees + * ``stalmarck`` : https://github.com/coq-contribs/stalmarck + +Note that ``continuations`` and ``multiplier`` are a bit particular. They are +examples of developments where ``Obj.magic`` are needed. This is +probably due to an heavy use of impredicativity. After compilation, those +two examples run nonetheless, thanks to the correction of the +extraction :cite:`Let02`. diff --git a/doc/sphinx/addendum/generalized-rewriting.rst b/doc/sphinx/addendum/generalized-rewriting.rst new file mode 100644 index 0000000000..e4dea34874 --- /dev/null +++ b/doc/sphinx/addendum/generalized-rewriting.rst @@ -0,0 +1,847 @@ +.. include:: ../preamble.rst +.. include:: ../replaces.rst + +.. _generalizedrewriting: + +Generalized rewriting +===================== + +:Author: Matthieu Sozeau + +This chapter presents the extension of several equality related +tactics to work over user-defined structures (called setoids) that are +equipped with ad-hoc equivalence relations meant to behave as +equalities. Actually, the tactics have also been generalized to +relations weaker then equivalences (e.g. rewriting systems). The +toolbox also extends the automatic rewriting capabilities of the +system, allowing the specification of custom strategies for rewriting. + +This documentation is adapted from the previous setoid documentation +by Claudio Sacerdoti Coen (based on previous work by Clément Renard). +The new implementation is a drop-in replacement for the old one +[#tabareau]_, hence most of the documentation still applies. + +The work is a complete rewrite of the previous implementation, based +on the type class infrastructure. It also improves on and generalizes +the previous implementation in several ways: + + ++ User-extensible algorithm. The algorithm is separated in two parts: + generations of the rewriting constraints (done in ML) and solving of + these constraints using type class resolution. As type class + resolution is extensible using tactics, this allows users to define + general ways to solve morphism constraints. ++ Sub-relations. An example extension to the base algorithm is the + ability to define one relation as a subrelation of another so that + morphism declarations on one relation can be used automatically for + the other. This is done purely using tactics and type class search. ++ Rewriting under binders. It is possible to rewrite under binders in + the new implementation, if one provides the proper morphisms. Again, + most of the work is handled in the tactics. ++ First-class morphisms and signatures. Signatures and morphisms are + ordinary Coq terms, hence they can be manipulated inside Coq, put + inside structures and lemmas about them can be proved inside the + system. Higher-order morphisms are also allowed. ++ Performance. The implementation is based on a depth-first search for + the first solution to a set of constraints which can be as fast as + linear in the size of the term, and the size of the proof term is + linear in the size of the original term. Besides, the extensibility + allows the user to customize the proof search if necessary. + +.. [#tabareau] Nicolas Tabareau helped with the gluing. + +Introduction to generalized rewriting +------------------------------------- + + +Relations and morphisms +~~~~~~~~~~~~~~~~~~~~~~~ + +A parametric *relation* ``R`` is any term of type +``forall (x1 :T1 ) ... (xn :Tn ), relation A``. +The expression ``A``, which depends on ``x1 ... xn`` , is called the *carrier* +of the relation and ``R`` is said to be a relation over ``A``; the list +``x1,...,xn`` is the (possibly empty) list of parameters of the relation. + +**Example 1 (Parametric relation):** + +It is possible to implement finite sets of elements of type ``A`` as +unordered list of elements of type ``A``. +The function ``set_eq: forall (A: Type), relation (list A)`` +satisfied by two lists with the same elements is a parametric relation +over ``(list A)`` with one parameter ``A``. The type of ``set_eq`` +is convertible with ``forall (A: Type), list A -> list A -> Prop.`` + +An *instance* of a parametric relation ``R`` with n parameters is any term +``(R t1 ... tn )``. + +Let ``R`` be a relation over ``A`` with ``n`` parameters. A term is a parametric +proof of reflexivity for ``R`` if it has type +``forall (x1 :T1 ) ... (xn :Tn), reflexive (R x1 ... xn )``. +Similar definitions are given for parametric proofs of symmetry and transitivity. + +**Example 2 (Parametric relation (cont.)):** + +The ``set_eq`` relation of the previous example can be proved to be +reflexive, symmetric and transitive. A parametric unary function ``f`` of type +``forall (x1 :T1 ) ... (xn :Tn ), A1 -> A2`` covariantly respects two parametric relation instances +``R1`` and ``R2`` if, whenever ``x``, ``y`` satisfy ``R1 x y``, their images (``f x``) and (``f y``) +satisfy ``R2 (f x) (f y)``. An ``f`` that respects its input and output +relations will be called a unary covariant *morphism*. We can also say +that ``f`` is a monotone function with respect to ``R1`` and ``R2`` . The +sequence ``x1 ... xn`` represents the parameters of the morphism. + +Let ``R1`` and ``R2`` be two parametric relations. The *signature* of a +parametric morphism of type ``forall (x1 :T1 ) ... (xn :Tn ), A1 -> A2`` +that covariantly respects two instances :math:`I_{R_1}` and :math:`I_{R_2}` of ``R1`` and ``R2`` +is written :math:`I_{R_1} ++> I_{R_2}`. Notice that the special arrow ++>, which +reminds the reader of covariance, is placed between the two relation +instances, not between the two carriers. The signature relation +instances and morphism will be typed in a context introducing +variables for the parameters. + +The previous definitions are extended straightforwardly to n-ary +morphisms, that are required to be simultaneously monotone on every +argument. + +Morphisms can also be contravariant in one or more of their arguments. +A morphism is contravariant on an argument associated to the relation +instance :math`R` if it is covariant on the same argument when the inverse +relation :math:`R^{−1}` (``inverse R`` in Coq) is considered. The special arrow ``-->`` +is used in signatures for contravariant morphisms. + +Functions having arguments related by symmetric relations instances +are both covariant and contravariant in those arguments. The special +arrow ``==>`` is used in signatures for morphisms that are both +covariant and contravariant. + +An instance of a parametric morphism :math:`f` with :math:`n` +parameters is any term :math:`f \, t_1 \ldots t_n`. + +**Example 3 (Morphisms):** + +Continuing the previous example, let ``union: forall (A: Type), list A -> list A -> list A`` +perform the union of two sets by appending one list to the other. ``union` is a binary +morphism parametric over ``A`` that respects the relation instance +``(set_eq A)``. The latter condition is proved by showing: + +.. coqtop:: in + + forall (A: Type) (S1 S1’ S2 S2’: list A), + set_eq A S1 S1’ -> + set_eq A S2 S2’ -> + set_eq A (union A S1 S2) (union A S1’ S2’). + +The signature of the function ``union A`` is ``set_eq A ==> set_eq A ==> set_eq A`` +for all ``A``. + +**Example 4 (Contravariant morphism):** + +The division function ``Rdiv: R -> R -> R`` is a morphism of signature +``le ++> le --> le`` where ``le`` is the usual order relation over +real numbers. Notice that division is covariant in its first argument +and contravariant in its second argument. + +Leibniz equality is a relation and every function is a morphism that +respects Leibniz equality. Unfortunately, Leibniz equality is not +always the intended equality for a given structure. + +In the next section we will describe the commands to register terms as +parametric relations and morphisms. Several tactics that deal with +equality in Coq can also work with the registered relations. The exact +list of tactic will be given :ref:`in this section <tactics-enabled-on-user-provided-relations>`. +For instance, the tactic reflexivity can be used to close a goal ``R n n`` whenever ``R`` +is an instance of a registered reflexive relation. However, the +tactics that replace in a context ``C[]`` one term with another one +related by ``R`` must verify that ``C[]`` is a morphism that respects the +intended relation. Currently the verification consists in checking +whether ``C[]`` is a syntactic composition of morphism instances that respects some obvious +compatibility constraints. + + +**Example 5 (Rewriting):** + +Continuing the previous examples, suppose that the user must prove +``set_eq int (union int (union int S1 S2) S2) (f S1 S2)`` under the +hypothesis ``H: set_eq int S2 (@nil int)``. It +is possible to use the ``rewrite`` tactic to replace the first two +occurrences of ``S2`` with ``@nil int`` in the goal since the +context ``set_eq int (union int (union int S1 nil) nil) (f S1 S2)``, +being a composition of morphisms instances, is a morphism. However the +tactic will fail replacing the third occurrence of ``S2`` unless ``f`` +has also been declared as a morphism. + + +Adding new relations and morphisms +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +A parametric relation :g:`Aeq: forall (y1 : β1 ... ym : βm )`, +:g:`relation (A t1 ... tn)` over :g:`(A : αi -> ... αn -> Type)` can be +declared with the following command: + +.. cmd:: Add Parametric Relation (x1 : T1) ... (xn : Tk) : (A t1 ... tn) (Aeq t′1 ... t′m ) {? reflexivity proved by refl} {? symmetry proved by sym} {? transitivity proved by trans} as @ident. + +after having required the ``Setoid`` module with the ``Require Setoid`` +command. + +The :g:`@ident` gives a unique name to the morphism and it is used +by the command to generate fresh names for automatically provided +lemmas used internally. + +Notice that the carrier and relation parameters may refer to the +context of variables introduced at the beginning of the declaration, +but the instances need not be made only of variables. Also notice that +``A`` is *not* required to be a term having the same parameters as ``Aeq``, +although that is often the case in practice (this departs from the +previous implementation). + + +.. cmd:: Add Relation + +In case the carrier and relations are not parametric, one can use this command +instead, whose syntax is the same except there is no local context. + +The proofs of reflexivity, symmetry and transitivity can be omitted if +the relation is not an equivalence relation. The proofs must be +instances of the corresponding relation definitions: e.g. the proof of +reflexivity must have a type convertible to +:g:`reflexive (A t1 ... tn) (Aeq t′ 1 …t′ n )`. +Each proof may refer to the introduced variables as well. + +**Example 6 (Parametric relation):** + +For Leibniz equality, we may declare: + +.. coqtop:: in + + Add Parametric Relation (A : Type) : A (@eq A) + [reflexivity proved by @refl_equal A] + ... + +Some tactics (``reflexivity``, ``symmetry``, ``transitivity``) work only on +relations that respect the expected properties. The remaining tactics +(``replace``, ``rewrite`` and derived tactics such as ``autorewrite``) do not +require any properties over the relation. However, they are able to +replace terms with related ones only in contexts that are syntactic +compositions of parametric morphism instances declared with the +following command. + +.. cmd:: Add Parametric Morphism (x1 : T1 ) ... (xk : Tk ) : (f t1 ... tn ) with signature sig as @ident. + +The command declares ``f`` as a parametric morphism of signature ``sig``. The +identifier ``id`` gives a unique name to the morphism and it is used as +the base name of the type class instance definition and as the name of +the lemma that proves the well-definedness of the morphism. The +parameters of the morphism as well as the signature may refer to the +context of variables. The command asks the user to prove interactively +that ``f`` respects the relations identified from the signature. + +**Example 7:** + +We start the example by assuming a small theory over +homogeneous sets and we declare set equality as a parametric +equivalence relation and union of two sets as a parametric morphism. + +.. coqtop:: in + + Require Export Setoid. + Require Export Relation_Definitions. + + Set Implicit Arguments. + + Parameter set: Type -> Type. + Parameter empty: forall A, set A. + Parameter eq_set: forall A, set A -> set A -> Prop. + Parameter union: forall A, set A -> set A -> set A. + + Axiom eq_set_refl: forall A, reflexive _ (eq_set (A:=A)). + Axiom eq_set_sym: forall A, symmetric _ (eq_set (A:=A)). + Axiom eq_set_trans: forall A, transitive _ (eq_set (A:=A)). + Axiom empty_neutral: forall A (S: set A), eq_set (union S (empty A)) S. + + Axiom union_compat: forall (A : Type), + forall x x' : set A, eq_set x x' -> + forall y y' : set A, eq_set y y' -> + eq_set (union x y) (union x' y'). + + Add Parametric Relation A : (set A) (@eq_set A) + reflexivity proved by (eq_set_refl (A:=A)) + symmetry proved by (eq_set_sym (A:=A)) + transitivity proved by (eq_set_trans (A:=A)) + as eq_set_rel. + + Add Parametric Morphism A : (@union A) with + signature (@eq_set A) ==> (@eq_set A) ==> (@eq_set A) as union_mor. + Proof. + exact (@union_compat A). + Qed. + +It is possible to reduce the burden of specifying parameters using +(maximally inserted) implicit arguments. If ``A`` is always set as +maximally implicit in the previous example, one can write: + +.. coqtop:: in + + Add Parametric Relation A : (set A) eq_set + reflexivity proved by eq_set_refl + symmetry proved by eq_set_sym + transitivity proved by eq_set_trans + as eq_set_rel. + +.. coqtop:: in + + Add Parametric Morphism A : (@union A) with + signature eq_set ==> eq_set ==> eq_set as union_mor. + +.. coqtop:: in + + Proof. exact (@union_compat A). Qed. + +We proceed now by proving a simple lemma performing a rewrite step and +then applying reflexivity, as we would do working with Leibniz +equality. Both tactic applications are accepted since the required +properties over ``eq_set`` and ``union`` can be established from the two +declarations above. + +.. coqtop:: in + + Goal forall (S: set nat), + eq_set (union (union S empty) S) (union S S). + +.. coqtop:: in + + Proof. intros. rewrite empty_neutral. reflexivity. Qed. + +The tables of relations and morphisms are managed by the type class +instance mechanism. The behavior on section close is to generalize the +instances by the variables of the section (and possibly hypotheses +used in the proofs of instance declarations) but not to export them in +the rest of the development for proof search. One can use the +``Existing Instance`` command to do so outside the section, using the name of the +declared morphism suffixed by ``_Morphism``, or use the ``Global`` modifier +for the corresponding class instance declaration +(see :ref:`First Class Setoids and Morphisms <first-class-setoids-and-morphisms>`) at +definition time. When loading a compiled file or importing a module, +all the declarations of this module will be loaded. + + +Rewriting and non reflexive relations +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To replace only one argument of an n-ary morphism it is necessary to +prove that all the other arguments are related to themselves by the +respective relation instances. + +**Example 8:** + +To replace ``(union S empty)`` with ``S`` in ``(union (union S empty) S) (union S S)`` +the rewrite tactic must exploit the monotony of ``union`` (axiom ``union_compat`` +in the previous example). Applying ``union_compat`` by hand we are left with the +goal ``eq_set (union S S) (union S S)``. + +When the relations associated to some arguments are not reflexive, the +tactic cannot automatically prove the reflexivity goals, that are left +to the user. + +Setoids whose relation are partial equivalence relations (PER) are +useful to deal with partial functions. Let ``R`` be a PER. We say that an +element ``x`` is defined if ``R x x``. A partial function whose domain +comprises all the defined elements only is declared as a morphism that +respects ``R``. Every time a rewriting step is performed the user must +prove that the argument of the morphism is defined. + +**Example 9:** + +Let ``eqO`` be ``fun x y => x = y /\ x <> 0`` (the +smaller PER over non zero elements). Division can be declared as a +morphism of signature ``eq ==> eq0 ==> eq``. Replace ``x`` with +``y`` in ``div x n = div y n`` opens the additional goal ``eq0 n n`` +that is equivalent to ``n = n /\ n <> 0``. + + +Rewriting and non symmetric relations +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +When the user works up to relations that are not symmetric, it is no +longer the case that any covariant morphism argument is also +contravariant. As a result it is no longer possible to replace a term +with a related one in every context, since the obtained goal implies +the previous one if and only if the replacement has been performed in +a contravariant position. In a similar way, replacement in an +hypothesis can be performed only if the replaced term occurs in a +covariant position. + +**Example 10 (Covariance and contravariance):** + +Suppose that division over real numbers has been defined as a morphism of signature +``Z.div: Z.lt ++> Z.lt --> Z.lt`` (i.e. ``Z.div`` is increasing in +its first argument, but decreasing on the second one). Let ``<`` +denotes ``Z.lt``. Under the hypothesis ``H: x < y`` we have +``k < x / y -> k < x / x``, but not ``k < y / x -> k < x / x``. Dually, +under the same hypothesis ``k < x / y -> k < y / y`` holds, but +``k < y / x -> k < y / y`` does not. Thus, if the current goal is +``k < x / x``, it is possible to replace only the second occurrence of +``x`` (in contravariant position) with ``y`` since the obtained goal +must imply the current one. On the contrary, if ``k < x / x`` is an +hypothesis, it is possible to replace only the first occurrence of +``x`` (in covariant position) with ``y`` since the current +hypothesis must imply the obtained one. + +Contrary to the previous implementation, no specific error message +will be raised when trying to replace a term that occurs in the wrong +position. It will only fail because the rewriting constraints are not +satisfiable. However it is possible to use the at modifier to specify +which occurrences should be rewritten. + +As expected, composing morphisms together propagates the variance +annotations by switching the variance every time a contravariant +position is traversed. + +**Example 11:** + +Let us continue the previous example and let us consider +the goal ``x / (x / x) < k``. The first and third occurrences of +``x`` are in a contravariant position, while the second one is in +covariant position. More in detail, the second occurrence of ``x`` +occurs covariantly in ``(x / x)`` (since division is covariant in +its first argument), and thus contravariantly in ``x / (x / x)`` +(since division is contravariant in its second argument), and finally +covariantly in ``x / (x / x) < k`` (since ``<``, as every +transitive relation, is contravariant in its first argument with +respect to the relation itself). + + +Rewriting in ambiguous setoid contexts +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +One function can respect several different relations and thus it can +be declared as a morphism having multiple signatures. + +**Example 12:** + + +Union over homogeneous lists can be given all the +following signatures: ``eq ==> eq ==> eq`` (``eq`` being the +equality over ordered lists) ``set_eq ==> set_eq ==> set_eq`` +(``set_eq`` being the equality over unordered lists up to duplicates), +``multiset_eq ==> multiset_eq ==> multiset_eq`` (``multiset_eq`` +being the equality over unordered lists). + +To declare multiple signatures for a morphism, repeat the ``Add Morphism`` +command. + +When morphisms have multiple signatures it can be the case that a +rewrite request is ambiguous, since it is unclear what relations +should be used to perform the rewriting. Contrary to the previous +implementation, the tactic will always choose the first possible +solution to the set of constraints generated by a rewrite and will not +try to find *all* possible solutions to warn the user about. + + +Commands and tactics +-------------------- + + +.. _first-class-setoids-and-morphisms: + +First class setoids and morphisms +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + + + +The implementation is based on a first-class representation of +properties of relations and morphisms as type classes. That is, the +various combinations of properties on relations and morphisms are +represented as records and instances of theses classes are put in a +hint database. For example, the declaration: + +.. coqtop:: in + + Add Parametric Relation (x1 : T1) ... (xn : Tk) : (A t1 ... tn) (Aeq t′1 ... t′m) + [reflexivity proved by refl] + [symmetry proved by sym] + [transitivity proved by trans] + as id. + + +is equivalent to an instance declaration: + +.. coqtop:: in + + Instance (x1 : T1) ... (xn : Tk) => id : @Equivalence (A t1 ... tn) (Aeq t′1 ... t′m) := + [Equivalence_Reflexive := refl] + [Equivalence_Symmetric := sym] + [Equivalence_Transitive := trans]. + +The declaration itself amounts to the definition of an object of the +record type ``Coq.Classes.RelationClasses.Equivalence`` and a hint added +to the ``typeclass_instances`` hint database. Morphism declarations are +also instances of a type class defined in ``Classes.Morphisms``. See the +documentation on type classes :ref:`typeclasses` +and the theories files in Classes for further explanations. + +One can inform the rewrite tactic about morphisms and relations just +by using the typeclass mechanism to declare them using Instance and +Context vernacular commands. Any object of type Proper (the type of +morphism declarations) in the local context will also be automatically +used by the rewriting tactic to solve constraints. + +Other representations of first class setoids and morphisms can also be +handled by encoding them as records. In the following example, the +projections of the setoid relation and of the morphism function can be +registered as parametric relations and morphisms. + +**Example 13 (First class setoids):** + +.. coqtop:: in + + Require Import Relation_Definitions Setoid. + + Record Setoid: Type := + { car: Type; + eq: car -> car -> Prop; + refl: reflexive _ eq; + sym: symmetric _ eq; + trans: transitive _ eq + }. + + Add Parametric Relation (s : Setoid) : (@car s) (@eq s) + reflexivity proved by (refl s) + symmetry proved by (sym s) + transitivity proved by (trans s) as eq_rel. + + Record Morphism (S1 S2:Setoid): Type := + { f: car S1 -> car S2; + compat: forall (x1 x2: car S1), eq S1 x1 x2 -> eq S2 (f x1) (f x2) + }. + + Add Parametric Morphism (S1 S2 : Setoid) (M : Morphism S1 S2) : + (@f S1 S2 M) with signature (@eq S1 ==> @eq S2) as apply_mor. + Proof. apply (compat S1 S2 M). Qed. + + Lemma test: forall (S1 S2:Setoid) (m: Morphism S1 S2) + (x y: car S1), eq S1 x y -> eq S2 (f _ _ m x) (f _ _ m y). + Proof. intros. rewrite H. reflexivity. Qed. + +.. _tactics-enabled-on-user-provided-relations: + +Tactics enabled on user provided relations +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The following tactics, all prefixed by ``setoid_``, deal with arbitrary +registered relations and morphisms. Moreover, all the corresponding +unprefixed tactics (i.e. ``reflexivity``, ``symmetry``, ``transitivity``, +``replace``, ``rewrite``) have been extended to fall back to their prefixed +counterparts when the relation involved is not Leibniz equality. +Notice, however, that using the prefixed tactics it is possible to +pass additional arguments such as ``using relation``. + +.. tacv:: setoid_reflexivity + :name: setoid_reflexivity + +.. tacv:: setoid_symmetry [in @ident] + :name: setoid_symmetry + +.. tacv:: setoid_transitivity + :name: setoid_transitivity + +.. tacv:: setoid_rewrite [@orientation] @term [at @occs] [in @ident] + :name: setoid_rewrite + +.. tacv:: setoid_replace @term with @term [in @ident] [using relation @term] [by @tactic] + :name: setoid_replace + + +The ``using relation`` arguments cannot be passed to the unprefixed form. +The latter argument tells the tactic what parametric relation should +be used to replace the first tactic argument with the second one. If +omitted, it defaults to the ``DefaultRelation`` instance on the type of +the objects. By default, it means the most recent ``Equivalence`` instance +in the environment, but it can be customized by declaring +new ``DefaultRelation`` instances. As Leibniz equality is a declared +equivalence, it will fall back to it if no other relation is declared +on a given type. + +Every derived tactic that is based on the unprefixed forms of the +tactics considered above will also work up to user defined relations. +For instance, it is possible to register hints for ``autorewrite`` that +are not proof of Leibniz equalities. In particular it is possible to +exploit ``autorewrite`` to simulate normalization in a term rewriting +system up to user defined equalities. + + +Printing relations and morphisms +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The ``Print Instances`` command can be used to show the list of currently +registered ``Reflexive`` (using ``Print Instances Reflexive``), ``Symmetric`` +or ``Transitive`` relations, Equivalences, PreOrders, PERs, and Morphisms +(implemented as ``Proper`` instances). When the rewriting tactics refuse +to replace a term in a context because the latter is not a composition +of morphisms, the ``Print Instances`` commands can be useful to understand +what additional morphisms should be registered. + + +Deprecated syntax and backward incompatibilities +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Due to backward compatibility reasons, the following syntax for the +declaration of setoids and morphisms is also accepted. + +.. cmd:: Add Setoid @A @Aeq @ST as @ident + +where ``Aeq`` is a congruence relation without parameters, ``A`` is its carrier +and ``ST`` is an object of type (``Setoid_Theory A Aeq``) (i.e. a record +packing together the reflexivity, symmetry and transitivity lemmas). +Notice that the syntax is not completely backward compatible since the +identifier was not required. + +.. cmd:: Add Morphism f : @ident. + +The latter command also is restricted to the declaration of morphisms +without parameters. It is not fully backward compatible since the +property the user is asked to prove is slightly different: for n-ary +morphisms the hypotheses of the property are permuted; moreover, when +the morphism returns a proposition, the property is now stated using a +bi-implication in place of a simple implication. In practice, porting +an old development to the new semantics is usually quite simple. + +Notice that several limitations of the old implementation have been +lifted. In particular, it is now possible to declare several relations +with the same carrier and several signatures for the same morphism. +Moreover, it is now also possible to declare several morphisms having +the same signature. Finally, the replace and rewrite tactics can be +used to replace terms in contexts that were refused by the old +implementation. As discussed in the next section, the semantics of the +new ``setoid_rewrite`` command differs slightly from the old one and +``rewrite``. + + +Extensions +---------- + + +Rewriting under binders +~~~~~~~~~~~~~~~~~~~~~~~ + +warning:: Due to compatibility issues, this feature is enabled only +when calling the ``setoid_rewrite`` tactics directly and not ``rewrite``. + +To be able to rewrite under binding constructs, one must declare +morphisms with respect to pointwise (setoid) equivalence of functions. +Example of such morphisms are the standard ``all`` and ``ex`` combinators for +universal and existential quantification respectively. They are +declared as morphisms in the ``Classes.Morphisms_Prop`` module. For +example, to declare that universal quantification is a morphism for +logical equivalence: + +.. coqtop:: in + + Instance all_iff_morphism (A : Type) : + Proper (pointwise_relation A iff ==> iff) (@all A). + +.. coqtop:: all + + Proof. simpl_relation. + +One then has to show that if two predicates are equivalent at every +point, their universal quantifications are equivalent. Once we have +declared such a morphism, it will be used by the setoid rewriting +tactic each time we try to rewrite under an ``all`` application (products +in ``Prop`` are implicitly translated to such applications). + +Indeed, when rewriting under a lambda, binding variable ``x``, say from ``P x`` +to ``Q x`` using the relation iff, the tactic will generate a proof of +``pointwise_relation A iff (fun x => P x) (fun x => Q x)`` from the proof +of ``iff (P x) (Q x)`` and a constraint of the form Proper +``(pointwise_relation A iff ==> ?) m`` will be generated for the +surrounding morphism ``m``. + +Hence, one can add higher-order combinators as morphisms by providing +signatures using pointwise extension for the relations on the +functional arguments (or whatever subrelation of the pointwise +extension). For example, one could declare the ``map`` combinator on lists +as a morphism: + +.. coqtop:: in + + Instance map_morphism `{Equivalence A eqA, Equivalence B eqB} : + Proper ((eqA ==> eqB) ==> list_equiv eqA ==> list_equiv eqB) (@map A B). + +where ``list_equiv`` implements an equivalence on lists parameterized by +an equivalence on the elements. + +Note that when one does rewriting with a lemma under a binder using +``setoid_rewrite``, the application of the lemma may capture the bound +variable, as the semantics are different from rewrite where the lemma +is first matched on the whole term. With the new ``setoid_rewrite``, +matching is done on each subterm separately and in its local +environment, and all matches are rewritten *simultaneously* by +default. The semantics of the previous ``setoid_rewrite`` implementation +can almost be recovered using the ``at 1`` modifier. + + +Sub-relations +~~~~~~~~~~~~~ + +Sub-relations can be used to specify that one relation is included in +another, so that morphisms signatures for one can be used for the +other. If a signature mentions a relation ``R`` on the left of an +arrow ``==>``, then the signature also applies for any relation ``S`` that is +smaller than ``R``, and the inverse applies on the right of an arrow. One +can then declare only a few morphisms instances that generate the +complete set of signatures for a particular constant. By default, the +only declared subrelation is ``iff``, which is a subrelation of ``impl`` and +``inverse impl`` (the dual of implication). That’s why we can declare only +two morphisms for conjunction: ``Proper (impl ==> impl ==> impl) and`` and +``Proper (iff ==> iff ==> iff) and``. This is sufficient to satisfy any +rewriting constraints arising from a rewrite using ``iff``, ``impl`` or +``inverse impl`` through ``and``. + +Sub-relations are implemented in ``Classes.Morphisms`` and are a prime +example of a mostly user-space extension of the algorithm. + + +Constant unfolding +~~~~~~~~~~~~~~~~~~ + +The resolution tactic is based on type classes and hence regards user- +defined constants as transparent by default. This may slow down the +resolution due to a lot of unifications (all the declared ``Proper`` +instances are tried at each node of the search tree). To speed it up, +declare your constant as rigid for proof search using the command +``Typeclasses Opaque`` (see :ref:`TypeclassesTransparent`). + +Strategies for rewriting +------------------------ + +Definitions +~~~~~~~~~~~ + +The generalized rewriting tactic is based on a set of strategies that can be +combined to obtain custom rewriting procedures. Its set of strategies is based +on Elan’s rewriting strategies :cite:`Luttik97specificationof`. Rewriting +strategies are applied using the tactic ``rewrite_strat s`` where ``s`` is a +strategy expression. Strategies are defined inductively as described by the +following grammar: + +.. productionlist:: rewriting + s, t, u : `strategy` + : | `lemma` + : | `lemma_right_to_left` + : | `failure` + : | `identity` + : | `reflexivity` + : | `progress` + : | `failure_catch` + : | `composition` + : | `left_biased_choice` + : | `iteration_one_or_more` + : | `iteration_zero_or_more` + : | `one_subterm` + : | `all_subterms` + : | `innermost_first` + : | `outermost_first` + : | `bottom_up` + : | `top_down` + : | `apply_hint` + : | `any_of_the_terms` + : | `apply_reduction` + : | `fold_expression` + +.. productionlist:: rewriting + strategy : "(" `s` ")" + lemma : `c` + lemma_right_to_left : "<-" `c` + failure : `fail` + identity : `id` + reflexivity : `refl` + progress : `progress` `s` + failure_catch : `try` `s` + composition : `s` ";" `u` + left_biased_choice : choice `s` `t` + iteration_one_or_more : `repeat` `s` + iteration_zero_or_more : `any` `s` + one_subterm : subterm `s` + all_subterms : subterms `s` + innermost_first : `innermost` `s` + outermost_first : `outermost` `s` + bottom_up : `bottomup` `s` + top_down : `topdown` `s` + apply_hint : hints `hintdb` + any_of_the_terms : terms (`c`)+ + apply_reduction : eval `redexpr` + fold_expression : fold `c` + + +Actually a few of these are defined in term of the others using a +primitive fixpoint operator: + +.. productionlist:: rewriting + try `s` : choice `s` `id` + any `s` : fix `u`. try (`s` ; `u`) + repeat `s` : `s` ; `any` `s` + bottomup s : fix `bu`. (choice (progress (subterms bu)) s) ; try bu + topdown s : fix `td`. (choice s (progress (subterms td))) ; try td + innermost s : fix `i`. (choice (subterm i) s) + outermost s : fix `o`. (choice s (subterm o)) + +The basic control strategy semantics are straightforward: strategies +are applied to subterms of the term to rewrite, starting from the root +of the term. The lemma strategies unify the left-hand-side of the +lemma with the current subterm and on success rewrite it to the right- +hand-side. Composition can be used to continue rewriting on the +current subterm. The fail strategy always fails while the identity +strategy succeeds without making progress. The reflexivity strategy +succeeds, making progress using a reflexivity proof of rewriting. +Progress tests progress of the argument strategy and fails if no +progress was made, while ``try`` always succeeds, catching failures. +Choice is left-biased: it will launch the first strategy and fall back +on the second one in case of failure. One can iterate a strategy at +least 1 time using ``repeat`` and at least 0 times using ``any``. + +The ``subterm`` and ``subterms`` strategies apply their argument strategy ``s`` to +respectively one or all subterms of the current term under +consideration, left-to-right. ``subterm`` stops at the first subterm for +which ``s`` made progress. The composite strategies ``innermost`` and ``outermost`` +perform a single innermost or outermost rewrite using their argument +strategy. Their counterparts ``bottomup`` and ``topdown`` perform as many +rewritings as possible, starting from the bottom or the top of the +term. + +Hint databases created for ``autorewrite`` can also be used +by ``rewrite_strat`` using the ``hints`` strategy that applies any of the +lemmas at the current subterm. The ``terms`` strategy takes the lemma +names directly as arguments. The ``eval`` strategy expects a reduction +expression (see :ref:`performingcomputations`) and succeeds +if it reduces the subterm under consideration. The ``fold`` strategy takes +a term ``c`` and tries to *unify* it to the current subterm, converting it to ``c`` +on success, it is stronger than the tactic ``fold``. + + +Usage +~~~~~ + + +.. tacn:: rewrite_strat @s [in @ident] + :name: rewrite_strat + + Rewrite using the strategy s in hypothesis ident or the conclusion. + + .. exn:: Nothing to rewrite. + + If the strategy failed. + + .. exn:: No progress made. + + If the strategy succeeded but made no progress. + + .. exn:: Unable to satisfy the rewriting constraints. + + If the strategy succeeded and made progress but the + corresponding rewriting constraints are not satisfied. + + + The ``setoid_rewrite c`` tactic is basically equivalent to + ``rewrite_strat (outermost c)``. + diff --git a/doc/sphinx/addendum/implicit-coercions.rst b/doc/sphinx/addendum/implicit-coercions.rst new file mode 100644 index 0000000000..c48c2d7ce1 --- /dev/null +++ b/doc/sphinx/addendum/implicit-coercions.rst @@ -0,0 +1,464 @@ +.. include:: ../replaces.rst + +.. _implicitcoercions: + +Implicit Coercions +==================== + +:Author: Amokrane Saïbi + +General Presentation +--------------------- + +This section describes the inheritance mechanism of |Coq|. In |Coq| with +inheritance, we are not interested in adding any expressive power to +our theory, but only convenience. Given a term, possibly not typable, +we are interested in the problem of determining if it can be well +typed modulo insertion of appropriate coercions. We allow to write: + + * :g:`f a` where :g:`f:(forall x:A,B)` and :g:`a:A'` when ``A'`` can + be seen in some sense as a subtype of ``A``. + * :g:`x:A` when ``A`` is not a type, but can be seen in + a certain sense as a type: set, group, category etc. + * :g:`f a` when ``f`` is not a function, but can be seen in a certain sense + as a function: bijection, functor, any structure morphism etc. + + +Classes +------- + +A class with `n` parameters is any defined name with a type +:g:`forall (x₁:A₁)..(xₙ:Aₙ),s` where ``s`` is a sort. Thus a class with +parameters is considered as a single class and not as a family of +classes. An object of a class ``C`` is any term of type :g:`C t₁ .. tₙ`. +In addition to these user-classes, we have two abstract classes: + + + * ``Sortclass``, the class of sorts; its objects are the terms whose type is a + sort (e.g. :g:`Prop` or :g:`Type`). + * ``Funclass``, the class of functions; its objects are all the terms with a functional + type, i.e. of form :g:`forall x:A,B`. + +Formally, the syntax of a classes is defined as: + +.. productionlist:: + class: qualid + : | `Sortclass` + : | `Funclass` + + +Coercions +--------- + +A name ``f`` can be declared as a coercion between a source user-class +``C`` with `n` parameters and a target class ``D`` if one of these +conditions holds: + + * ``D`` is a user-class, then the type of ``f`` must have the form + :g:`forall (x₁:A₁)..(xₙ:Aₙ)(y:C x₁..xₙ), D u₁..uₘ` where `m` + is the number of parameters of ``D``. + * ``D`` is ``Funclass``, then the type of ``f`` must have the form + :g:`forall (x₁:A₁)..(xₙ:Aₙ)(y:C x₁..xₙ)(x:A), B`. + * ``D`` is ``Sortclass``, then the type of ``f`` must have the form + :g:`forall (x₁:A₁)..(xₙ:Aₙ)(y:C x₁..xₙ), s` with ``s`` a sort. + +We then write :g:`f : C >-> D`. The restriction on the type +of coercions is called *the uniform inheritance condition*. + +.. note:: The abstract classe ``Sortclass`` can be used as a source class, but + the abstract class ``Funclass`` cannot. + +To coerce an object :g:`t:C t₁..tₙ` of ``C`` towards ``D``, we have to +apply the coercion ``f`` to it; the obtained term :g:`f t₁..tₙ t` is +then an object of ``D``. + + +Identity Coercions +------------------- + +Identity coercions are special cases of coercions used to go around +the uniform inheritance condition. Let ``C`` and ``D`` be two classes +with respectively `n` and `m` parameters and +:g:`f:forall (x₁:T₁)..(xₖ:Tₖ)(y:C u₁..uₙ), D v₁..vₘ` a function which +does not verify the uniform inheritance condition. To declare ``f`` as +coercion, one has first to declare a subclass ``C'`` of ``C``: + + :g:`C' := fun (x₁:T₁)..(xₖ:Tₖ) => C u₁..uₙ` + +We then define an *identity coercion* between ``C'`` and ``C``: + + :g:`Id_C'_C := fun (x₁:T₁)..(xₖ:Tₖ)(y:C' x₁..xₖ) => (y:C u₁..uₙ)` + +We can now declare ``f`` as coercion from ``C'`` to ``D``, since we can +"cast" its type as +:g:`forall (x₁:T₁)..(xₖ:Tₖ)(y:C' x₁..xₖ),D v₁..vₘ`. + +The identity coercions have a special status: to coerce an object +:g:`t:C' t₁..tₖ` +of ``C'`` towards ``C``, we does not have to insert explicitly ``Id_C'_C`` +since :g:`Id_C'_C t₁..tₖ t` is convertible with ``t``. However we +"rewrite" the type of ``t`` to become an object of ``C``; in this case, +it becomes :g:`C uₙ'..uₖ'` where each ``uᵢ'`` is the result of the +substitution in ``uᵢ`` of the variables ``xⱼ`` by ``tⱼ``. + +Inheritance Graph +------------------ + +Coercions form an inheritance graph with classes as nodes. We call +*coercion path* an ordered list of coercions between two nodes of +the graph. A class ``C`` is said to be a subclass of ``D`` if there is a +coercion path in the graph from ``C`` to ``D``; we also say that ``C`` +inherits from ``D``. Our mechanism supports multiple inheritance since a +class may inherit from several classes, contrary to simple inheritance +where a class inherits from at most one class. However there must be +at most one path between two classes. If this is not the case, only +the *oldest* one is valid and the others are ignored. So the order +of declaration of coercions is important. + +We extend notations for coercions to coercion paths. For instance +:g:`[f₁;..;fₖ] : C >-> D` is the coercion path composed +by the coercions ``f₁..fₖ``. The application of a coercion path to a +term consists of the successive application of its coercions. + + +Declaration of Coercions +------------------------- + +.. cmd:: Coercion @qualid : @class >-> @class. + + Declares the construction denoted by `qualid` as a coercion between + the two given classes. + + .. exn:: @qualid not declared + .. exn:: @qualid is already a coercion + .. exn:: Funclass cannot be a source class + .. exn:: @qualid is not a function + .. exn:: Cannot find the source class of @qualid + .. exn:: Cannot recognize @class as a source class of @qualid + .. exn:: @qualid does not respect the uniform inheritance condition + .. exn:: Found target class ... instead of ... + + .. warn:: Ambiguous path + + When the coercion `qualid` is added to the inheritance graph, non + valid coercion paths are ignored; they are signaled by a warning + displaying these paths of the form :g:`[f₁;..;fₙ] : C >-> D`. + + .. cmdv:: Local Coercion @qualid : @class >-> @class. + + Declares the construction denoted by `qualid` as a coercion local to + the current section. + + .. cmdv:: Coercion @ident := @term. + + This defines `ident` just like ``Definition`` `ident` ``:=`` `term`, + and then declares `ident` as a coercion between it source and its target. + + .. cmdv:: Coercion @ident := @term : @type. + + This defines `ident` just like ``Definition`` `ident` : `type` ``:=`` `term`, + and then declares `ident` as a coercion between it source and its target. + + .. cmdv:: Local Coercion @ident := @term. + + This defines `ident` just like ``Let`` `ident` ``:=`` `term`, + and then declares `ident` as a coercion between it source and its target. + +Assumptions can be declared as coercions at declaration time. +This extends the grammar of assumptions from +Figure :ref:`vernacular` as follows: + +.. + FIXME: + \comindex{Variable \mbox{\rm (and coercions)}} + \comindex{Axiom \mbox{\rm (and coercions)}} + \comindex{Parameter \mbox{\rm (and coercions)}} + \comindex{Hypothesis \mbox{\rm (and coercions)}} + +.. productionlist:: + assumption : assumption_keyword assums . + assums : simple_assums + : | (simple_assums) ... (simple_assums) + simple_assums : ident ... ident :[>] term + +If the extra ``>`` is present before the type of some assumptions, these +assumptions are declared as coercions. + +Similarly, constructors of inductive types can be declared as coercions at +definition time of the inductive type. This extends and modifies the +grammar of inductive types from Figure :ref:`vernacular` as follows: + +.. + FIXME: + \comindex{Inductive \mbox{\rm (and coercions)}} + \comindex{CoInductive \mbox{\rm (and coercions)}} + +.. productionlist:: + inductive : `Inductive` ind_body `with` ... `with` ind_body + : | `CoInductive` ind_body `with` ... `with` ind_body + ind_body : ident [binders] : term := [[|] constructor | ... | constructor] + constructor : ident [binders] [:[>] term] + +Especially, if the extra ``>`` is present in a constructor +declaration, this constructor is declared as a coercion. + +.. cmd:: Identity Coercion @ident : @class >-> @class. + + If ``C`` is the source `class` and ``D`` the destination, we check + that ``C`` is a constant with a body of the form + :g:`fun (x₁:T₁)..(xₙ:Tₙ) => D t₁..tₘ` where `m` is the + number of parameters of ``D``. Then we define an identity + function with type :g:`forall (x₁:T₁)..(xₙ:Tₙ)(y:C x₁..xₙ),D t₁..tₘ`, + and we declare it as an identity coercion between ``C`` and ``D``. + + .. exn:: @class must be a transparent constant + + .. cmdv:: Local Identity Coercion @ident : @ident >-> @ident. + + Idem but locally to the current section. + + .. cmdv:: SubClass @ident := @type. + :name: SubClass + + If `type` is a class `ident'` applied to some arguments then + `ident` is defined and an identity coercion of name + `Id_ident_ident'` is + declared. Otherwise said, this is an abbreviation for + + ``Definition`` `ident` ``:=`` `type`. + + ``Identity Coercion`` `Id_ident_ident'` : `ident` ``>->`` `ident'`. + + .. cmdv:: Local SubClass @ident := @type. + + Same as before but locally to the current section. + + +Displaying Available Coercions +------------------------------- + +.. cmd:: Print Classes. + + Print the list of declared classes in the current context. + +.. cmd:: Print Coercions. + + Print the list of declared coercions in the current context. + +.. cmd:: Print Graph. + + Print the list of valid coercion paths in the current context. + +.. cmd:: Print Coercion Paths @class @class. + + Print the list of valid coercion paths between the two given classes. + +Activating the Printing of Coercions +------------------------------------- + +.. opt:: Printing Coercions + + When on, this option forces all the coercions to be printed. + By default, coercions are not printed. + +.. cmd:: Add Printing Coercion @qualid + + This command forces coercion denoted by :n:`@qualid` to be printed. To skip + the printing of coercion :n:`@qualid`, use :cmd:`Remove Printing Coercion`. By + default, a coercion is never printed. + +.. _coercions-classes-as-records: + +Classes as Records +------------------ + +We allow the definition of *Structures with Inheritance* (or classes as records) +by extending the existing :cmd:`Record` macro. Its new syntax is: + +.. cmdv:: Record {? >} @ident {? @binders} : @sort := {? @ident} { {+; @ident :{? >} @term } }. + + The first identifier `ident` is the name of the defined record and + `sort` is its type. The optional identifier after ``:=`` is the name + of the constuctor (it will be ``Build_``\ `ident` if not given). + The other identifiers are the names of the fields, and the `term` + are their respective types. If ``:>`` is used instead of ``:`` in + the declaration of a field, then the name of this field is automatically + declared as a coercion from the record name to the class of this + field type. Remark that the fields always verify the uniform + inheritance condition. If the optional ``>`` is given before the + record name, then the constructor name is automatically declared as + a coercion from the class of the last field type to the record name + (this may fail if the uniform inheritance condition is not + satisfied). + +.. cmdv:: Structure {? >} @ident {? @binders} : @sort := {? @ident} { {+; @ident :{? >} @term } }. + :name: Structure + + This is a synonym of :cmd:`Record`. + + +Coercions and Sections +---------------------- + +The inheritance mechanism is compatible with the section +mechanism. The global classes and coercions defined inside a section +are redefined after its closing, using their new value and new +type. The classes and coercions which are local to the section are +simply forgotten. +Coercions with a local source class or a local target class, and +coercions which do not verify the uniform inheritance condition any longer +are also forgotten. + +Coercions and Modules +--------------------- + +.. opt:: Automatic Coercions Import + + Since |Coq| version 8.3, the coercions present in a module are activated + only when the module is explicitly imported. Formerly, the coercions + were activated as soon as the module was required, whatever it was + imported or not. + + This option makes it possible to recover the behavior of the versions of + |Coq| prior to 8.3. + +Examples +-------- + +There are three situations: + +Coercion at function application +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:g:`f a` is ill-typed where :g:`f:forall x:A,B` and :g:`a:A'`. If there is a +coercion path between ``A'`` and ``A``, then :g:`f a` is transformed into +:g:`f a'` where ``a'`` is the result of the application of this +coercion path to ``a``. + +We first give an example of coercion between atomic inductive types + +.. coqtop:: all + + Definition bool_in_nat (b:bool) := if b then 0 else 1. + Coercion bool_in_nat : bool >-> nat. + Check (0 = true). + Set Printing Coercions. + Check (0 = true). + Unset Printing Coercions. + + +.. warning:: + + Note that ``Check true=O`` would fail. This is "normal" behaviour of + coercions. To validate ``true=O``, the coercion is searched from + ``nat`` to ``bool``. There is none. + +We give an example of coercion between classes with parameters. + +.. coqtop:: all + + Parameters (C : nat -> Set) (D : nat -> bool -> Set) (E : bool -> Set). + Parameter f : forall n:nat, C n -> D (S n) true. + Coercion f : C >-> D. + Parameter g : forall (n:nat) (b:bool), D n b -> E b. + Coercion g : D >-> E. + Parameter c : C 0. + Parameter T : E true -> nat. + Check (T c). + Set Printing Coercions. + Check (T c). + Unset Printing Coercions. + +We give now an example using identity coercions. + +.. coqtop:: all + + Definition D' (b:bool) := D 1 b. + Identity Coercion IdD'D : D' >-> D. + Print IdD'D. + Parameter d' : D' true. + Check (T d'). + Set Printing Coercions. + Check (T d'). + Unset Printing Coercions. + + +In the case of functional arguments, we use the monotonic rule of +sub-typing. Approximatively, to coerce :g:`t:forall x:A,B` towards +:g:`forall x:A',B'`, one have to coerce ``A'`` towards ``A`` and ``B`` +towards ``B'``. An example is given below: + +.. coqtop:: all + + Parameters (A B : Set) (h : A -> B). + Coercion h : A >-> B. + Parameter U : (A -> E true) -> nat. + Parameter t : B -> C 0. + Check (U t). + Set Printing Coercions. + Check (U t). + Unset Printing Coercions. + +Remark the changes in the result following the modification of the +previous example. + +.. coqtop:: all + + Parameter U' : (C 0 -> B) -> nat. + Parameter t' : E true -> A. + Check (U' t'). + Set Printing Coercions. + Check (U' t'). + Unset Printing Coercions. + + +Coercion to a type +~~~~~~~~~~~~~~~~~~ + +An assumption ``x:A`` when ``A`` is not a type, is ill-typed. It is +replaced by ``x:A'`` where ``A'`` is the result of the application to +``A`` of the coercion path between the class of ``A`` and +``Sortclass`` if it exists. This case occurs in the abstraction +:g:`fun x:A => t`, universal quantification :g:`forall x:A,B`, global +variables and parameters of (co-)inductive definitions and +functions. In :g:`forall x:A,B`, such a coercion path may be applied +to ``B`` also if necessary. + +.. coqtop:: all + + Parameter Graph : Type. + Parameter Node : Graph -> Type. + Coercion Node : Graph >-> Sortclass. + Parameter G : Graph. + Parameter Arrows : G -> G -> Type. + Check Arrows. + Parameter fg : G -> G. + Check fg. + Set Printing Coercions. + Check fg. + Unset Printing Coercions. + + +Coercion to a function +~~~~~~~~~~~~~~~~~~~~~~ + +``f a`` is ill-typed because ``f:A`` is not a function. The term +``f`` is replaced by the term obtained by applying to ``f`` the +coercion path between ``A`` and ``Funclass`` if it exists. + +.. coqtop:: all + + Parameter bij : Set -> Set -> Set. + Parameter ap : forall A B:Set, bij A B -> A -> B. + Coercion ap : bij >-> Funclass. + Parameter b : bij nat nat. + Check (b 0). + Set Printing Coercions. + Check (b 0). + Unset Printing Coercions. + +Let us see the resulting graph after all these examples. + +.. coqtop:: all + + Print Graph. diff --git a/doc/sphinx/addendum/micromega.rst b/doc/sphinx/addendum/micromega.rst index e850587c8a..4f8cc34d4a 100644 --- a/doc/sphinx/addendum/micromega.rst +++ b/doc/sphinx/addendum/micromega.rst @@ -13,20 +13,19 @@ tactics for solving arithmetic goals over :math:`\mathbb{Z}`, :math:`\mathbb{Q}` It also possible to get the tactics for integers by a ``Require Import Lia``, rationals ``Require Import Lqa`` and reals ``Require Import Lra``. -+ ``lia`` is a decision procedure for linear integer arithmetic (see Section :ref:`lia <lia>`); -+ ``nia`` is an incomplete proof procedure for integer non-linear - arithmetic (see Section :ref:`nia <nia>`); -+ ``lra`` is a decision procedure for linear (real or rational) arithmetic - (see Section :ref:`lra <lra>`); -+ ``nra`` is an incomplete proof procedure for non-linear (real or - rational) arithmetic (see Section :ref:`nra <nra>`); -+ ``psatz D n`` where ``D`` is :math:`\mathbb{Z}` or :math:`\mathbb{Q}` or :math:`\mathbb{R}`, and ++ :tacn:`lia` is a decision procedure for linear integer arithmetic; ++ :tacn:`nia` is an incomplete proof procedure for integer non-linear + arithmetic; ++ :tacn:`lra` is a decision procedure for linear (real or rational) arithmetic; ++ :tacn:`nra` is an incomplete proof procedure for non-linear (real or + rational) arithmetic; ++ :tacn:`psatz` ``D n`` where ``D`` is :math:`\mathbb{Z}` or :math:`\mathbb{Q}` or :math:`\mathbb{R}`, and ``n`` is an optional integer limiting the proof search depth is an incomplete proof procedure for non-linear arithmetic. It is based on John Harrison’s HOL Light driver to the external prover `csdp` [#]_. Note that the `csdp` driver is generating a *proof cache* which makes it possible to rerun scripts - even without `csdp` (see Section :ref:`psatz <psatz>`). + even without `csdp`. The tactics solve propositional formulas parameterized by atomic arithmetic expressions interpreted over a domain :math:`D` ∈ {ℤ, ℚ, ℝ}. @@ -91,12 +90,13 @@ For each conjunct :math:`C_i`, the tactic calls a oracle which searches for expression* that is normalized by the ring tactic (see :ref:`theringandfieldtacticfamilies`) and checked to be :math:`-1`. -.. _lra: - `lra`: a decision procedure for linear real and rational arithmetic ------------------------------------------------------------------- -The `lra` tactic is searching for *linear* refutations using Fourier +.. tacn:: lra + :name: lra + +This tactic is searching for *linear* refutations using Fourier elimination [#]_. As a result, this tactic explores a subset of the *Cone* defined as @@ -107,16 +107,17 @@ The deductive power of `lra` is the combined deductive power of tactic *e.g.*, :math:`x = 10 * x / 10` is solved by `lra`. -.. _lia: - `lia`: a tactic for linear integer arithmetic --------------------------------------------- -The tactic lia offers an alternative to the omega and romega tactic -(see :ref:`omega`). Roughly speaking, the deductive power of lia is -the combined deductive power of `ring_simplify` and `omega`. However, it -solves linear goals that `omega` and `romega` do not solve, such as the -following so-called *omega nightmare* :cite:`TheOmegaPaper`. +.. tacn:: lia + :name: lia + +This tactic offers an alternative to the :tacn:`omega` and :tac:`romega` +tactics. Roughly speaking, the deductive power of lia is the combined deductive +power of :tacn:`ring_simplify` and :tacn:`omega`. However, it solves linear +goals that :tacn:`omega` and :tacn:`romega` do not solve, such as the following +so-called *omega nightmare* :cite:`TheOmegaPaper`. .. coqtop:: in @@ -124,8 +125,8 @@ following so-called *omega nightmare* :cite:`TheOmegaPaper`. 27 <= 11 * x + 13 * y <= 45 -> -10 <= 7 * x - 9 * y <= 4 -> False. -The estimation of the relative efficiency of `lia` *vs* `omega` and `romega` -is under evaluation. +The estimation of the relative efficiency of :tacn:`lia` *vs* :tacn:`omega` and +:tacn:`romega` is under evaluation. High level view of `lia` ~~~~~~~~~~~~~~~~~~~~~~~~ @@ -182,12 +183,13 @@ Our current oracle tries to find an expression :math:`e` with a small range with an equation :math:`e = i` for :math:`i \in [c_1,c_2]` and recursively search for a proof. -.. _nra: - `nra`: a proof procedure for non-linear arithmetic -------------------------------------------------- -The `nra` tactic is an *experimental* proof procedure for non-linear +.. tacn:: nra + :name: nra + +This tactic is an *experimental* proof procedure for non-linear arithmetic. The tactic performs a limited amount of non-linear reasoning before running the linear prover of `lra`. This pre-processing does the following: @@ -202,21 +204,23 @@ does the following: After this pre-processing, the linear prover of `lra` searches for a proof by abstracting monomials by variables. -.. _nia: - `nia`: a proof procedure for non-linear integer arithmetic ---------------------------------------------------------- -The `nia` tactic is a proof procedure for non-linear integer arithmetic. +.. tacn:: nia + :name: nia + +This tactic is a proof procedure for non-linear integer arithmetic. It performs a pre-processing similar to `nra`. The obtained goal is solved using the linear integer prover `lia`. -.. _psatz: - `psatz`: a proof procedure for non-linear arithmetic ---------------------------------------------------- -The `psatz` tactic explores the :math:`\mathit{Cone}` by increasing degrees – hence the +.. tacn:: psatz + :name: psatz + +This tactic explores the :math:`\mathit{Cone}` by increasing degrees – hence the depth parameter :math:`n`. In theory, such a proof search is complete – if the goal is provable the search eventually stops. Unfortunately, the external oracle is using numeric (approximate) optimization techniques diff --git a/doc/sphinx/addendum/miscellaneous-extensions.rst b/doc/sphinx/addendum/miscellaneous-extensions.rst new file mode 100644 index 0000000000..80ea8a1166 --- /dev/null +++ b/doc/sphinx/addendum/miscellaneous-extensions.rst @@ -0,0 +1,59 @@ +.. include:: ../replaces.rst + +.. _miscellaneousextensions: + +Miscellaneous extensions +======================== + +Program derivation +------------------ + +|Coq| comes with an extension called ``Derive``, which supports program +derivation. Typically in the style of Bird and Meertens or derivations +of program refinements. To use the Derive extension it must first be +required with ``Require Coq.Derive.Derive``. When the extension is loaded, +it provides the following command: + +.. cmd:: Derive @ident SuchThat @term As @ident + +The first `ident` can appear in `term`. This command opens a new proof +presenting the user with a goal for term in which the name `ident` is +bound to an existential variable `?x` (formally, there are other goals +standing for the existential variables but they are shelved, as +described in :tacn:`shelve`). + +When the proof ends two constants are defined: + ++ The first one is named using the first `ident` and is defined as the proof of the + shelved goal (which is also the value of `?x`). It is always + transparent. ++ The second one is named using the second `ident`. It has type `term`, and its body is + the proof of the initially visible goal. It is opaque if the proof + ends with ``Qed``, and transparent if the proof ends with ``Defined``. + +.. example:: + .. coqtop:: all + + Require Coq.derive.Derive. + Require Import Coq.Numbers.Natural.Peano.NPeano. + + Section P. + + Variables (n m k:nat). + + Derive p SuchThat ((k*n)+(k*m) = p) As h. + Proof. + rewrite <- Nat.mul_add_distr_l. + subst p. + reflexivity. + Qed. + + End P. + + Print p. + Check h. + +Any property can be used as `term`, not only an equation. In particular, +it could be an order relation specifying some form of program +refinement or a non-executable property from which deriving a program +is convenient. diff --git a/doc/sphinx/addendum/nsatz.rst b/doc/sphinx/addendum/nsatz.rst new file mode 100644 index 0000000000..387d614956 --- /dev/null +++ b/doc/sphinx/addendum/nsatz.rst @@ -0,0 +1,101 @@ +.. include:: ../preamble.rst + +.. _nsatz: + +Nsatz: tactics for proving equalities in integral domains +=========================================================== + +:Author: Loïc Pottier + +The tactic `nsatz` proves goals of the form + +:math:`\begin{array}{l} +\forall X_1,\ldots,X_n \in A,\\ +P_1(X_1,\ldots,X_n) = Q_1(X_1,\ldots,X_n) , \ldots , P_s(X_1,\ldots,X_n) =Q_s(X_1,\ldots,X_n)\\ +\vdash P(X_1,\ldots,X_n) = Q(X_1,\ldots,X_n)\\ +\end{array}` + +where :math:`P, Q, P₁,Q₁,\ldots,Pₛ, Qₛ` are polynomials and :math:`A` is an integral +domain, i.e. a commutative ring with no zero divisor. For example, :math:`A` +can be :math:`\mathbb{R}`, :math:`\mathbb{Z}`, or :math:`\mathbb{Q}`. +Note that the equality :math:`=` used in these goals can be +any setoid equality (see :ref:`tactics-enabled-on-user-provided-relations`) , not only Leibnitz equality. + +It also proves formulas + +:math:`\begin{array}{l} +\forall X_1,\ldots,X_n \in A,\\ +P_1(X_1,\ldots,X_n) = Q_1(X_1,\ldots,X_n) \wedge \ldots \wedge P_s(X_1,\ldots,X_n) =Q_s(X_1,\ldots,X_n)\\ +\rightarrow P(X_1,\ldots,X_n) = Q(X_1,\ldots,X_n)\\ +\end{array}` + +doing automatic introductions. + + +Using the basic tactic `nsatz` +------------------------------ + + +Load the Nsatz module: + +.. coqtop:: all + + Require Import Nsatz. + +and use the tactic `nsatz`. + +More about `nsatz` +--------------------- + +Hilbert’s Nullstellensatz theorem shows how to reduce proofs of +equalities on polynomials on a commutative ring :math:`A` with no zero divisor +to algebraic computations: it is easy to see that if a polynomial :math:`P` in +:math:`A[X_1,\ldots,X_n]` verifies :math:`c P^r = \sum_{i=1}^{s} S_i P_i`, with +:math:`c \in A`, :math:`c \not = 0`, +:math:`r` a positive integer, and the :math:`S_i` s in :math:`A[X_1,\ldots,X_n ]`, +then :math:`P` is zero whenever polynomials :math:`P_1,\ldots,P_s` are zero +(the converse is also true when :math:`A` is an algebraic closed field: the method is +complete). + +So, proving our initial problem can reduce into finding :math:`S_1,\ldots,S_s`, +:math:`c` and :math:`r` such that :math:`c (P-Q)^r = \sum_{i} S_i (P_i-Q_i)`, +which will be proved by the tactic ring. + +This is achieved by the computation of a Gröbner basis of the ideal +generated by :math:`P_1-Q_1,...,P_s-Q_s`, with an adapted version of the +Buchberger algorithm. + +This computation is done after a step of *reification*, which is +performed using :ref:`typeclasses`. + +The ``Nsatz`` module defines the tactic `nsatz`, which can be used without +arguments, or with the syntax: + +| nsatz with radicalmax:=num%N strategy:=num%Z parameters:= :n:`{* var}` variables:= :n:`{* var}` + +where: + +* `radicalmax` is a bound when for searching r s.t. + :math:`c (P−Q) r = \sum_{i=1..s} S_i (P i − Q i)` + +* `strategy` gives the order on variables :math:`X_1,\ldots,X_n` and the strategy + used in Buchberger algorithm (see :cite:`sugar` for details): + + * strategy = 0: reverse lexicographic order and newest s-polynomial. + * strategy = 1: reverse lexicographic order and sugar strategy. + * strategy = 2: pure lexicographic order and newest s-polynomial. + * strategy = 3: pure lexicographic order and sugar strategy. + +* `parameters` is the list of variables :math:`X_{i_1},\ldots,X_{i_k}` among + :math:`X_1,\ldots,X_n` which are considered as parameters: computation will be performed with + rational fractions in these variables, i.e. polynomials are considered + with coefficients in :math:`R(X_{i_1},\ldots,X_{i_k})`. In this case, the coefficient + :math:`c` can be a non constant polynomial in :math:`X_{i_1},\ldots,X_{i_k}`, and the tactic + produces a goal which states that :math:`c` is not zero. + +* `variables` is the list of the variables in the decreasing order in + which they will be used in Buchberger algorithm. If `variables` = `(@nil R)`, + then `lvar` is replaced by all the variables which are not in + `parameters`. + +See file `Nsatz.v` for many examples, especially in geometry. diff --git a/doc/sphinx/addendum/parallel-proof-processing.rst b/doc/sphinx/addendum/parallel-proof-processing.rst new file mode 100644 index 0000000000..edb8676a5b --- /dev/null +++ b/doc/sphinx/addendum/parallel-proof-processing.rst @@ -0,0 +1,229 @@ +.. include:: ../replaces.rst + +.. _asynchronousandparallelproofprocessing: + +Asynchronous and Parallel Proof Processing +========================================== + +:Author: Enrico Tassi + +This chapter explains how proofs can be asynchronously processed by +|Coq|. This feature improves the reactivity of the system when used in +interactive mode via |CoqIDE|. In addition, it allows |Coq| to take +advantage of parallel hardware when used as a batch compiler by +decoupling the checking of statements and definitions from the +construction and checking of proofs objects. + +This feature is designed to help dealing with huge libraries of +theorems characterized by long proofs. In the current state, it may +not be beneficial on small sets of short files. + +This feature has some technical limitations that may make it +unsuitable for some use cases. + +For example, in interactive mode, some errors coming from the kernel +of |Coq| are signaled late. The type of errors belonging to this +category are universe inconsistencies. + +At the time of writing, only opaque proofs (ending with ``Qed`` or +``Admitted``) can be processed asynchronously. + +Finally, asynchronous processing is disabled when running |CoqIDE| in +Windows. The current implementation of the feature is not stable on +Windows. It can be enabled, as described below at :ref:`interactive-mode`, +though doing so is not recommended. + +Proof annotations +---------------------- + +To process a proof asynchronously |Coq| needs to know the precise +statement of the theorem without looking at the proof. This requires +some annotations if the theorem is proved inside a Section (see +Section :ref:`section-mechanism`). + +When a section ends, |Coq| looks at the proof object to decide which +section variables are actually used and hence have to be quantified in +the statement of the theorem. To avoid making the construction of +proofs mandatory when ending a section, one can start each proof with +the ``Proof using`` command (Section :ref:`proof-editing-mode`) that +declares which section variables the theorem uses. + +The presence of ``Proof`` using is needed to process proofs asynchronously +in interactive mode. + +It is not strictly mandatory in batch mode if it is not the first time +the file is compiled and if the file itself did not change. When the +proof does not begin with Proof using, the system records in an +auxiliary file, produced along with the `.vo` file, the list of section +variables used. + +Automatic suggestion of proof annotations +````````````````````````````````````````` + +The command ``Set Suggest Proof Using`` makes |Coq| suggest, when a ``Qed`` +command is processed, a correct proof annotation. It is up to the user +to modify the proof script accordingly. + + +Proof blocks and error resilience +-------------------------------------- + +|Coq| 8.6 introduced a mechanism for error resiliency: in interactive +mode |Coq| is able to completely check a document containing errors +instead of bailing out at the first failure. + +Two kind of errors are supported: errors occurring in vernacular +commands and errors occurring in proofs. + +To properly recover from a failing tactic, |Coq| needs to recognize the +structure of the proof in order to confine the error to a sub proof. +Proof block detection is performed by looking at the syntax of the +proof script (i.e. also looking at indentation). |Coq| comes with four +kind of proof blocks, and an ML API to add new ones. + +:curly: blocks are delimited by { and }, see Chapter :ref:`proofhandling` +:par: blocks are atomic, i.e. just one tactic introduced by the `par:` + goal selector +:indent: blocks end with a tactic indented less than the previous one +:bullet: blocks are delimited by two equal bullet signs at the same + indentation level + +Caveats +```````` + +When a vernacular command fails the subsequent error messages may be +bogus, i.e. caused by the first error. Error resiliency for vernacular +commands can be switched off by passing ``-async-proofs-command-error-resilience off`` +to |CoqIDE|. + +An incorrect proof block detection can result into an incorrect error +recovery and hence in bogus errors. Proof block detection cannot be +precise for bullets or any other non well parenthesized proof +structure. Error resiliency can be turned off or selectively activated +for any set of block kind passing to |CoqIDE| one of the following +options: + +- ``-async-proofs-tactic-error-resilience off`` +- ``-async-proofs-tactic-error-resilience all`` +- ``-async-proofs-tactic-error-resilience`` :n:`{*, blocktype}` + +Valid proof block types are: “curly”, “par”, “indent”, and “bullet”. + +.. _interactive-mode: + +Interactive mode +--------------------- + +At the time of writing the only user interface supporting asynchronous +proof processing is |CoqIDE|. + +When |CoqIDE| is started, two |Coq| processes are created. The master one +follows the user, giving feedback as soon as possible by skipping +proofs, which are delegated to the worker process. The worker process, +whose state can be seen by clicking on the button in the lower right +corner of the main |CoqIDE| window, asynchronously processes the proofs. +If a proof contains an error, it is reported in red in the label of +the very same button, that can also be used to see the list of errors +and jump to the corresponding line. + +If a proof is processed asynchronously the corresponding Qed command +is colored using a lighter color that usual. This signals that the +proof has been delegated to a worker process (or will be processed +lazily if the ``-async-proofs lazy`` option is used). Once finished, the +worker process will provide the proof object, but this will not be +automatically checked by the kernel of the main process. To force the +kernel to check all the proof objects, one has to click the button +with the gears. Only then are all the universe constraints checked. + +Caveats +``````` + +The number of worker processes can be increased by passing |CoqIDE| +the ``-async-proofs-j n`` flag. Note that the memory consumption increases too, +since each worker requires the same amount of memory as the master +process. Also note that increasing the number of workers may reduce +the reactivity of the master process to user commands. + +To disable this feature, one can pass the ``-async-proofs off`` flag to +|CoqIDE|. Conversely, on Windows, where the feature is disabled by +default, pass the ``-async-proofs on`` flag to enable it. + +Proofs that are known to take little time to process are not delegated +to a worker process. The threshold can be configure with +``-async-proofs-delegation-threshold``. Default is 0.03 seconds. + +Batch mode +--------------- + +When |Coq| is used as a batch compiler by running `coqc` or `coqtop` +-compile, it produces a `.vo` file for each `.v` file. A `.vo` file contains, +among other things, theorems statements and proofs. Hence to produce a +.vo |Coq| need to process all the proofs of the `.v` file. + +The asynchronous processing of proofs can decouple the generation of a +compiled file (like the `.vo` one) that can be loaded by ``Require`` from the +generation and checking of the proof objects. The ``-quick`` flag can be +passed to `coqc` or `coqtop` to produce, quickly, `.vio` files. +Alternatively, when using a Makefile produced by `coq_makefile`, +the ``quick`` target can be used to compile all files using the ``-quick`` flag. + +A `.vio` file can be loaded using ``Require`` exactly as a `.vo` file but +proofs will not be available (the Print command produces an error). +Moreover, some universe constraints might be missing, so universes +inconsistencies might go unnoticed. A `.vio` file does not contain proof +objects, but proof tasks, i.e. what a worker process can transform +into a proof object. + +Compiling a set of files with the ``-quick`` flag allows one to work, +interactively, on any file without waiting for all the proofs to be +checked. + +When working interactively, one can fully check all the `.v` files by +running `coqc` as usual. + +Alternatively one can turn each `.vio` into the corresponding `.vo`. All +.vio files can be processed in parallel, hence this alternative might +be faster. The command ``coqtop -schedule-vio2vo 2 a b c`` can be used to +obtain a good scheduling for two workers to produce `a.vo`, `b.vo`, and +`c.vo`. When using a Makefile produced by `coq_makefile`, the ``vio2vo`` target +can be used for that purpose. Variable `J` should be set to the number +of workers, e.g. ``make vio2vo J=2``. The only caveat is that, while the +.vo files obtained from `.vio` files are complete (they contain all proof +terms and universe constraints), the satisfiability of all universe +constraints has not been checked globally (they are checked to be +consistent for every single proof). Constraints will be checked when +these `.vo` files are (recursively) loaded with ``Require``. + +There is an extra, possibly even faster, alternative: just check the +proof tasks stored in `.vio` files without producing the `.vo` files. This +is possibly faster because all the proof tasks are independent, hence +one can further partition the job to be done between workers. The +``coqtop -schedule-vio-checking 6 a b c`` command can be used to obtain a +good scheduling for 6 workers to check all the proof tasks of `a.vio`, +`b.vio`, and `c.vio`. Auxiliary files are used to predict how long a proof +task will take, assuming it will take the same amount of time it took +last time. When using a Makefile produced by coq_makefile, the +``checkproofs`` target can be used to check all `.vio` files. Variable `J` +should be set to the number of workers, e.g. ``make checkproofs J=6``. As +when converting `.vio` files to `.vo` files, universe constraints are not +checked to be globally consistent. Hence this compilation mode is only +useful for quick regression testing and on developments not making +heavy use of the `Type` hierarchy. + +Limiting the number of parallel workers +-------------------------------------------- + +Many |Coq| processes may run on the same computer, and each of them may +start many additional worker processes. The `coqworkmgr` utility lets +one limit the number of workers, globally. + +The utility accepts the ``-j`` argument to specify the maximum number of +workers (defaults to 2). `coqworkmgr` automatically starts in the +background and prints an environment variable assignment +like ``COQWORKMGR_SOCKET=localhost:45634``. The user must set this variable +in all the shells from which |Coq| processes will be started. If one +uses just one terminal running the bash shell, then +``export ‘coqworkmgr -j 4‘`` will do the job. + +After that, all |Coq| processes, e.g. `coqide` and `coqc`, will honor the +limit, globally. diff --git a/doc/sphinx/addendum/program.rst b/doc/sphinx/addendum/program.rst new file mode 100644 index 0000000000..be30d1bc4a --- /dev/null +++ b/doc/sphinx/addendum/program.rst @@ -0,0 +1,382 @@ +.. include:: ../preamble.rst +.. include:: ../replaces.rst + +.. this should be just "_program", but refs to it don't work + +.. _programs: + +Program +======== + +:Author: Matthieu Sozeau + +We present here the |Program| tactic commands, used to build +certified |Coq| programs, elaborating them from their algorithmic +skeleton and a rich specification :cite:`sozeau06`. It can be thought of as a +dual of :ref:`Extraction <extraction>`. The goal of |Program| is to +program as in a regular functional programming language whilst using +as rich a specification as desired and proving that the code meets the +specification using the whole |Coq| proof apparatus. This is done using +a technique originating from the “Predicate subtyping” mechanism of +PVS :cite:`Rushby98`, which generates type-checking conditions while typing a +term constrained to a particular type. Here we insert existential +variables in the term, which must be filled with proofs to get a +complete |Coq| term. |Program| replaces the |Program| tactic by Catherine +Parent :cite:`Parent95b` which had a similar goal but is no longer maintained. + +The languages available as input are currently restricted to |Coq|’s +term language, but may be extended to OCaml, Haskell and +others in the future. We use the same syntax as |Coq| and permit to use +implicit arguments and the existing coercion mechanism. Input terms +and types are typed in an extended system (Russell) and interpreted +into |Coq| terms. The interpretation process may produce some proof +obligations which need to be resolved to create the final term. + + +.. _elaborating-programs: + +Elaborating programs +--------------------- + +The main difference from |Coq| is that an object in a type T : Set can +be considered as an object of type { x : T | P} for any wellformed P : +Prop. If we go from T to the subset of T verifying property P, we must +prove that the object under consideration verifies it. Russell will +generate an obligation for every such coercion. In the other +direction, Russell will automatically insert a projection. + +Another distinction is the treatment of pattern-matching. Apart from +the following differences, it is equivalent to the standard match +operation (see :ref:`extendedpatternmatching`). + + ++ Generation of equalities. A match expression is always generalized + by the corresponding equality. As an example, the expression: + + :: + + match x with + | 0 => t + | S n => u + end. + + will be first rewritten to: + + :: + + (match x as y return (x = y -> _) with + | 0 => fun H : x = 0 -> t + | S n => fun H : x = S n -> u + end) (eq_refl n). + + This permits to get the proper equalities in the context of proof + obligations inside clauses, without which reasoning is very limited. + ++ Generation of inequalities. If a pattern intersects with a previous + one, an inequality is added in the context of the second branch. See + for example the definition of div2 below, where the second branch is + typed in a context where ∀ p, _ <> S (S p). ++ Coercion. If the object being matched is coercible to an inductive + type, the corresponding coercion will be automatically inserted. This + also works with the previous mechanism. + + +There are options to control the generation of equalities and +coercions. + +.. opt:: Program Cases + + This controls the special treatment of pattern-matching generating equalities + and inequalities when using |Program| (it is on by default). All + pattern-matchings and let-patterns are handled using the standard algorithm + of |Coq| (see :ref:`extendedpatternmatching`) when this option is + deactivated. + +.. opt:: Program Generalized Coercion + + This controls the coercion of general inductive types when using |Program| + (the option is on by default). Coercion of subset types and pairs is still + active in this case. + +.. _syntactic_control: + +Syntactic control over equalities +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To give more control over the generation of equalities, the +typechecker will fall back directly to |Coq|’s usual typing of dependent +pattern-matching if a return or in clause is specified. Likewise, the +if construct is not treated specially by |Program| so boolean tests in +the code are not automatically reflected in the obligations. One can +use the dec combinator to get the correct hypotheses as in: + +.. coqtop:: none + + Require Import Program Arith. + +.. coqtop:: all + + Program Definition id (n : nat) : { x : nat | x = n } := + if dec (leb n 0) then 0 + else S (pred n). + +The let tupling construct :g:`let (x1, ..., xn) := t in b` does not +produce an equality, contrary to the let pattern construct :g:`let ’(x1, +..., xn) := t in b`. Also, :g:`term :>` explicitly asks the system to +coerce term to its support type. It can be useful in notations, for +example: + +.. coqtop:: all + + Notation " x `= y " := (@eq _ (x :>) (y :>)) (only parsing). + +This notation denotes equality on subset types using equality on their +support types, avoiding uses of proof-irrelevance that would come up +when reasoning with equality on the subset types themselves. + +The next two commands are similar to their standard counterparts +:cmd:`Definition` and :cmd:`Fixpoint` +in that they define constants. However, they may require the user to +prove some goals to construct the final definitions. + + +.. _program_definition: + +Program Definition +~~~~~~~~~~~~~~~~~~ + +.. cmd:: Program Definition @ident := @term. + + This command types the value term in Russell and generates proof + obligations. Once solved using the commands shown below, it binds the + final |Coq| term to the name ``ident`` in the environment. + + .. exn:: @ident already exists (Program Definition) + + .. cmdv:: Program Definition @ident : @type := @term + + It interprets the type ``type``, potentially generating proof + obligations to be resolved. Once done with them, we have a |Coq| + type |type_0|. It then elaborates the preterm ``term`` into a |Coq| + term |term_0|, checking that the type of |term_0| is coercible to + |type_0|, and registers ``ident`` as being of type |type_0| once the + set of obligations generated during the interpretation of |term_0| + and the aforementioned coercion derivation are solved. + + .. exn:: In environment … the term: @term does not have type @type. Actually, it has type ... + + + .. cmdv:: Program Definition @ident @binders : @type := @term. + + This is equivalent to: + + :g:`Program Definition ident : forall binders, type := fun binders => term`. + + .. TODO refer to production in alias + +See also: Sections :ref:`vernac-controlling-the-reduction-strategies`, :tacn:`unfold` + +.. _program_fixpoint: + +Program Fixpoint +~~~~~~~~~~~~~~~~ + +.. cmd:: Program Fixpoint @ident @params {? {@order}} : @type := @term. + +The optional order annotation follows the grammar: + +.. productionlist:: orderannot + order : measure `term` (`term`)? | wf `term` `term` + ++ :g:`measure f ( R )` where :g:`f` is a value of type :g:`X` computed on + any subset of the arguments and the optional (parenthesised) term + ``(R)`` is a relation on ``X``. By default ``X`` defaults to ``nat`` and ``R`` + to ``lt``. + ++ :g:`wf R x` which is equivalent to :g:`measure x (R)`. + +The structural fixpoint operator behaves just like the one of |Coq| (see +:cmd:`Fixpoint`), except it may also generate obligations. It works +with mutually recursive definitions too. + +.. coqtop:: reset none + + Require Import Program Arith. + +.. coqtop:: all + + Program Fixpoint div2 (n : nat) : { x : nat | n = 2 * x \/ n = 2 * x + 1 } := + match n with + | S (S p) => S (div2 p) + | _ => O + end. + +Here we have one obligation for each branch (branches for :g:`0` and +``(S 0)`` are automatically generated by the pattern-matching +compilation algorithm). + +.. coqtop:: all + + Obligation 1. + +.. coqtop:: reset none + + Require Import Program Arith. + +One can use a well-founded order or a measure as termination orders +using the syntax: + +.. coqtop:: in + + Program Fixpoint div2 (n : nat) {measure n} : { x : nat | n = 2 * x \/ n = 2 * x + 1 } := + match n with + | S (S p) => S (div2 p) + | _ => O + end. + + + +.. caution:: When defining structurally recursive functions, the generated + obligations should have the prototype of the currently defined + functional in their context. In this case, the obligations should be + transparent (e.g. defined using :g:`Defined`) so that the guardedness + condition on recursive calls can be checked by the kernel’s type- + checker. There is an optimization in the generation of obligations + which gets rid of the hypothesis corresponding to the functional when + it is not necessary, so that the obligation can be declared opaque + (e.g. using :g:`Qed`). However, as soon as it appears in the context, the + proof of the obligation is *required* to be declared transparent. + + No such problems arise when using measures or well-founded recursion. + +.. _program_lemma: + +Program Lemma +~~~~~~~~~~~~~ + +.. cmd:: Program Lemma @ident : @type. + + The Russell language can also be used to type statements of logical + properties. It will generate obligations, try to solve them + automatically and fail if some unsolved obligations remain. In this + case, one can first define the lemma’s statement using :g:`Program + Definition` and use it as the goal afterwards. Otherwise the proof + will be started with the elaborated version as a goal. The + :g:`Program` prefix can similarly be used as a prefix for + :g:`Variable`, :g:`Hypothesis`, :g:`Axiom` etc... + +.. _solving_obligations: + +Solving obligations +-------------------- + +The following commands are available to manipulate obligations. The +optional identifier is used when multiple functions have unsolved +obligations (e.g. when defining mutually recursive blocks). The +optional tactic is replaced by the default one if not specified. + +.. cmd:: {? Local|Global} Obligation Tactic := @tactic + :name: Obligation Tactic + + Sets the default obligation solving tactic applied to all obligations + automatically, whether to solve them or when starting to prove one, + e.g. using :g:`Next`. :g:`Local` makes the setting last only for the current + module. Inside sections, local is the default. + +.. cmd:: Show Obligation Tactic + + Displays the current default tactic. + +.. cmd:: Obligations {? of @ident} + + Displays all remaining obligations. + +.. cmd:: Obligation num {? of @ident} + + Start the proof of obligation num. + +.. cmd:: Next Obligation {? of @ident} + + Start the proof of the next unsolved obligation. + +.. cmd:: Solve Obligations {? of @ident} {? with @tactic} + + Tries to solve each obligation of ``ident`` using the given ``tactic`` or the default one. + +.. cmd:: Solve All Obligations {? with @tactic} + + Tries to solve each obligation of every program using the given + tactic or the default one (useful for mutually recursive definitions). + +.. cmd:: Admit Obligations {? of @ident} + + Admits all obligations (of ``ident``). + + .. note:: Does not work with structurally recursive programs. + +.. cmd:: Preterm {? of @ident} + + Shows the term that will be fed to the kernel once the obligations + are solved. Useful for debugging. + +.. opt:: Transparent Obligations + + Control whether all obligations should be declared as transparent + (the default), or if the system should infer which obligations can be + declared opaque. + +.. opt:: Hide Obligations + + Control whether obligations appearing in the + term should be hidden as implicit arguments of the special + constantProgram.Tactics.obligation. + +.. opt:: Shrink Obligations + + *Deprecated since 8.7* + + This option (on by default) controls whether obligations should have + their context minimized to the set of variables used in the proof of + the obligation, to avoid unnecessary dependencies. + +The module :g:`Coq.Program.Tactics` defines the default tactic for solving +obligations called :g:`program_simpl`. Importing :g:`Coq.Program.Program` also +adds some useful notations, as documented in the file itself. + +.. _program-faq: + +Frequently Asked Questions +--------------------------- + + +.. exn:: Ill-formed recursive definition + + This error can happen when one tries to define a function by structural + recursion on a subset object, which means the |Coq| function looks like: + + :: + + Program Fixpoint f (x : A | P) := match x with A b => f b end. + + Supposing ``b : A``, the argument at the recursive call to ``f`` is not a + direct subterm of ``x`` as ``b`` is wrapped inside an ``exist`` constructor to + build an object of type ``{x : A | P}``. Hence the definition is + rejected by the guardedness condition checker. However one can use + wellfounded recursion on subset objects like this: + + :: + + Program Fixpoint f (x : A | P) { measure (size x) } := + match x with A b => f b end. + + One will then just have to prove that the measure decreases at each + recursive call. There are three drawbacks though: + + #. A measure function has to be defined; + #. The reduction is a little more involved, although it works well + using lazy evaluation; + #. Mutual recursion on the underlying inductive type isn’t possible + anymore, but nested mutual recursion is always possible. + +.. bibliography:: ../biblio.bib + :keyprefix: p- diff --git a/doc/sphinx/addendum/ring.rst b/doc/sphinx/addendum/ring.rst new file mode 100644 index 0000000000..ae666a0d45 --- /dev/null +++ b/doc/sphinx/addendum/ring.rst @@ -0,0 +1,770 @@ +.. include:: ../replaces.rst +.. |ra| replace:: :math:`\rightarrow_{\beta\delta\iota}` +.. |la| replace:: :math:`\leftarrow_{\beta\delta\iota}` +.. |eq| replace:: `=`:sub:`(by the main correctness theorem)` +.. |re| replace:: ``(PEeval`` `v` `ap`\ ``)`` +.. |le| replace:: ``(Pphi_dev`` `v` ``(norm`` `ap`\ ``))`` + + +.. _theringandfieldtacticfamilies: + +The ring and field tactic families +==================================== + +:Author: Bruno Barras, Benjamin Grégoire, Assia Mahboubi, Laurent Théry [#f1]_ + +This chapter presents the tactics dedicated to deal with ring and +field equations. + +What does this tactic do? +------------------------------ + +``ring`` does associative-commutative rewriting in ring and semi-ring +structures. Assume you have two binary functions :math:`\oplus` and +:math:`\otimes` that are associative and commutative, with :math:`\oplus` +distributive on :math:`\otimes`, and two constants 0 and 1 that are unities for +:math:`\oplus` and :math:`\otimes`. A polynomial is an expression built on +variables :math:`V_0`, :math:`V_1`, :math:`\dots` and constants by application +of :math:`\oplus` and :math:`\otimes`. + +Let an ordered product be a product of variables :math:`V_{i_1} \otimes \dots +\otimes V_{i_n}` verifying :math:`i_1 ≤ i_2 ≤ \dots ≤ i_n` . Let a monomial be +the product of a constant and an ordered product. We can order the monomials by +the lexicographic order on products of variables. Let a canonical sum be an +ordered sum of monomials that are all different, i.e. each monomial in the sum +is strictly less than the following monomial according to the lexicographic +order. It is an easy theorem to show that every polynomial is equivalent (modulo +the ring properties) to exactly one canonical sum. This canonical sum is called +the normal form of the polynomial. In fact, the actual representation shares +monomials with same prefixes. So what does ring? It normalizes polynomials over +any ring or semi-ring structure. The basic use of ``ring`` is to simplify ring +expressions, so that the user does not have to deal manually with the theorems +of associativity and commutativity. + + +.. example:: + + In the ring of integers, the normal form of + :math:`x (3 + yx + 25(1 − z)) + zx` + is + :math:`28x + (−24)xz + xxy`. + + +``ring`` is also able to compute a normal form modulo monomial equalities. +For example, under the hypothesis that :math:`2x^2 = yz+1`, the normal form of +:math:`2(x + 1)x − x − zy` is :math:`x+1`. + +The variables map +---------------------- + +It is frequent to have an expression built with :math:`+` and :math:`\times`, +but rarely on variables only. Let us associate a number to each subterm of a +ring expression in the Gallina language. For example in the ring |nat|, consider +the expression: + + +:: + + (plus (mult (plus (f (5)) x) x) + (mult (if b then (4) else (f (3))) (2))) + + +As a ring expression, it has 3 subterms. Give each subterm a number in +an arbitrary order: + +===== =============== ========================= +0 :math:`\mapsto` if b then (4) else (f (3)) +1 :math:`\mapsto` (f (5)) +2 :math:`\mapsto` x +===== =============== ========================= + +Then normalize the “abstract” polynomial +:math:`((V_1 \otimes V_2 ) \oplus V_2) \oplus (V_0 \otimes 2)` +In our example the normal form is: +:math:`(2 \otimes V_0 ) \oplus (V_1 \otimes V_2) \oplus (V_2 \otimes V_2 )`. +Then substitute the variables by their values in the variables map to +get the concrete normal polynomial: + +:: + + (plus (mult (2) (if b then (4) else (f (3)))) + (plus (mult (f (5)) x) (mult x x))) + + +Is it automatic? +--------------------- + +Yes, building the variables map and doing the substitution after +normalizing is automatically done by the tactic. So you can just +forget this paragraph and use the tactic according to your intuition. + +Concrete usage in Coq +-------------------------- + +.. tacn:: ring + +The ``ring`` tactic solves equations upon polynomial expressions of a ring +(or semi-ring) structure. It proceeds by normalizing both hand sides +of the equation (w.r.t. associativity, commutativity and +distributivity, constant propagation, rewriting of monomials) and +comparing syntactically the results. + +.. tacn:: ring_simplify + +``ring_simplify`` applies the normalization procedure described above to +the terms given. The tactic then replaces all occurrences of the terms +given in the conclusion of the goal by their normal forms. If no term +is given, then the conclusion should be an equation and both hand +sides are normalized. The tactic can also be applied in a hypothesis. + +The tactic must be loaded by ``Require Import Ring``. The ring structures +must be declared with the ``Add Ring`` command (see below). The ring of +booleans is predefined; if one wants to use the tactic on |nat| one must +first require the module ``ArithRing`` exported by ``Arith``); for |Z|, do +``Require Import ZArithRing`` or simply ``Require Import ZArith``; for |N|, do +``Require Import NArithRing`` or ``Require Import NArith``. + + +.. example:: + + .. coqtop:: all + + Require Import ZArith. + Open Scope Z_scope. + Goal forall a b c:Z, + (a + b + c) ^ 2 = + a * a + b ^ 2 + c * c + 2 * a * b + 2 * a * c + 2 * b * c. + intros; ring. + Abort. + Goal forall a b:Z, + 2 * a * b = 30 -> (a + b) ^ 2 = a ^ 2 + b ^ 2 + 30. + intros a b H; ring [H]. + Abort. + + +.. tacv:: ring [{* @term }] + +decides the equality of two terms modulo ring operations and +the equalities defined by the :n:`@term`\ s. +Each :n:`@term` has to be a proof of some equality `m = p`, where `m` is a monomial (after “abstraction”), `p` a polynomial and `=` the corresponding equality of the ring structure. + +.. tacv:: ring_simplify [{* @term }] {* @term } in @ident + +performs the simplification in the hypothesis named :n:`@ident`. + + +.. note:: + + .. tacn:: ring_simplify @term1; ring_simplify @term2 + + is not equivalent to + + .. tacn:: ring_simplify @term1 @term2 + + In the latter case the variables map + is shared between the two terms, and common subterm `t` of :n:`@term1` and :n:`@term2` + will have the same associated variable number. So the first + alternative should be avoided for terms belonging to the same ring + theory. + + +Error messages: + + +.. exn:: not a valid ring equation + + The conclusion of the goal is not provable in the corresponding ring theory. + +.. exn:: arguments of ring_simplify do not have all the same type + + ``ring_simplify`` cannot simplify terms of several rings at the same + time. Invoke the tactic once per ring structure. + +.. exn:: cannot find a declared ring structure over @term + + No ring has been declared for the type of the terms to be simplified. + Use ``Add Ring`` first. + +.. exn:: cannot find a declared ring structure for equality @term + + Same as above is the case of the ``ring`` tactic. + + +Adding a ring structure +---------------------------- + +Declaring a new ring consists in proving that a ring signature (a +carrier set, an equality, and ring operations: ``Ring_theory.ring_theory`` +and ``Ring_theory.semi_ring_theory``) satisfies the ring axioms. Semi- +rings (rings without + inverse) are also supported. The equality can +be either Leibniz equality, or any relation declared as a setoid (see +:ref:`tactics-enabled-on-user-provided-relations`). The definition of ring and semi-rings (see module +``Ring_theory``) is: + +.. coqtop:: in + + Record ring_theory : Prop := mk_rt { + Radd_0_l : forall x, 0 + x == x; + Radd_sym : forall x y, x + y == y + x; + Radd_assoc : forall x y z, x + (y + z) == (x + y) + z; + Rmul_1_l : forall x, 1 * x == x; + Rmul_sym : forall x y, x * y == y * x; + Rmul_assoc : forall x y z, x * (y * z) == (x * y) * z; + Rdistr_l : forall x y z, (x + y) * z == (x * z) + (y * z); + Rsub_def : forall x y, x - y == x + -y; + Ropp_def : forall x, x + (- x) == 0 + }. + + Record semi_ring_theory : Prop := mk_srt { + SRadd_0_l : forall n, 0 + n == n; + SRadd_sym : forall n m, n + m == m + n ; + SRadd_assoc : forall n m p, n + (m + p) == (n + m) + p; + SRmul_1_l : forall n, 1*n == n; + SRmul_0_l : forall n, 0*n == 0; + SRmul_sym : forall n m, n*m == m*n; + SRmul_assoc : forall n m p, n*(m*p) == (n*m)*p; + SRdistr_l : forall n m p, (n + m)*p == n*p + m*p + }. + + +This implementation of ``ring`` also features a notion of constant that +can be parameterized. This can be used to improve the handling of +closed expressions when operations are effective. It consists in +introducing a type of *coefficients* and an implementation of the ring +operations, and a morphism from the coefficient type to the ring +carrier type. The morphism needs not be injective, nor surjective. + +As an example, one can consider the real numbers. The set of +coefficients could be the rational numbers, upon which the ring +operations can be implemented. The fact that there exists a morphism +is defined by the following properties: + +.. coqtop:: in + + Record ring_morph : Prop := mkmorph { + morph0 : [cO] == 0; + morph1 : [cI] == 1; + morph_add : forall x y, [x +! y] == [x]+[y]; + morph_sub : forall x y, [x -! y] == [x]-[y]; + morph_mul : forall x y, [x *! y] == [x]*[y]; + morph_opp : forall x, [-!x] == -[x]; + morph_eq : forall x y, x?=!y = true -> [x] == [y] + }. + + Record semi_morph : Prop := mkRmorph { + Smorph0 : [cO] == 0; + Smorph1 : [cI] == 1; + Smorph_add : forall x y, [x +! y] == [x]+[y]; + Smorph_mul : forall x y, [x *! y] == [x]*[y]; + Smorph_eq : forall x y, x?=!y = true -> [x] == [y] + }. + + +where ``c0`` and ``cI`` denote the 0 and 1 of the coefficient set, ``+!``, ``*!``, ``-!`` +are the implementations of the ring operations, ``==`` is the equality of +the coefficients, ``?+!`` is an implementation of this equality, and ``[x]`` +is a notation for the image of ``x`` by the ring morphism. + +Since |Z| is an initial ring (and |N| is an initial semi-ring), it can +always be considered as a set of coefficients. There are basically +three kinds of (semi-)rings: + +abstract rings + to be used when operations are not effective. The set + of coefficients is |Z| (or |N| for semi-rings). + +computational rings + to be used when operations are effective. The + set of coefficients is the ring itself. The user only has to provide + an implementation for the equality. + +customized ring + for other cases. The user has to provide the + coefficient set and the morphism. + + +This implementation of ring can also recognize simple power +expressions as ring expressions. A power function is specified by the +following property: + +.. coqtop:: in + + Section POWER. + Variable Cpow : Set. + Variable Cp_phi : N -> Cpow. + Variable rpow : R -> Cpow -> R. + + Record power_theory : Prop := mkpow_th { + rpow_pow_N : forall r n, req (rpow r (Cp_phi n)) (pow_N rI rmul r n) + }. + + End POWER. + + +The syntax for adding a new ring is + +.. cmd:: Add Ring @ident : @term {? ( @ring_mod {* , @ring_mod } )}. + +The :n:`@ident` is not relevant. It is just used for error messages. The +:n:`@term` is a proof that the ring signature satisfies the (semi-)ring +axioms. The optional list of modifiers is used to tailor the behavior +of the tactic. The following list describes their syntax and effects: + +.. prodn:: + ring_mod ::= abstract %| decidable @term %| morphism @term + %| setoid @term @term + %| constants [@ltac] + %| preprocess [@ltac] + %| postprocess [@ltac] + %| power_tac @term [@ltac] + %| sign @term + %| div @term + + +abstract + declares the ring as abstract. This is the default. + +decidable :n:`@term` + declares the ring as computational. The expression + :n:`@term` is the correctness proof of an equality test ``?=!`` + (which hould be evaluable). Its type should be of the form + ``forall x y, x ?=! y = true → x == y``. + +morphism :n:`@term` + declares the ring as a customized one. The expression + :n:`@term` is a proof that there exists a morphism between a set of + coefficient and the ring carrier (see ``Ring_theory.ring_morph`` and + ``Ring_theory.semi_morph``). + +setoid :n:`@term` :n:`@term` + forces the use of given setoid. The first + :n:`@term` is a proof that the equality is indeed a setoid (see + ``Setoid.Setoid_Theory``), and the second :n:`@term` a proof that the + ring operations are morphisms (see ``Ring_theory.ring_eq_ext`` and + ``Ring_theory.sring_eq_ext``). + This modifier needs not be used if the setoid and morphisms have been + declared. + +constants [:n:`@ltac`] + specifies a tactic expression :n:`@ltac` that, given a + term, returns either an object of the coefficient set that is mapped + to the expression via the morphism, or returns + ``InitialRing.NotConstant``. The default behavior is to map only 0 and 1 + to their counterpart in the coefficient set. This is generally not + desirable for non trivial computational rings. + +preprocess [:n:`@ltac`] + specifies a tactic :n:`@ltac` that is applied as a + preliminary step for ``ring`` and ``ring_simplify``. It can be used to + transform a goal so that it is better recognized. For instance, ``S n`` + can be changed to ``plus 1 n``. + +postprocess [:n:`@ltac`] + specifies a tactic :n:`@ltac` that is applied as a final + step for ``ring_simplify``. For instance, it can be used to undo + modifications of the preprocessor. + +power_tac :n:`@term` [:n:`@ltac`] + allows ``ring`` and ``ring_simplify`` to recognize + power expressions with a constant positive integer exponent (example: + ::math:`x^2` ). The term :n:`@term` is a proof that a given power function satisfies + the specification of a power function (term has to be a proof of + ``Ring_theory.power_theory``) and :n:`@ltac` specifies a tactic expression + that, given a term, “abstracts” it into an object of type |N| whose + interpretation via ``Cp_phi`` (the evaluation function of power + coefficient) is the original term, or returns ``InitialRing.NotConstant`` + if not a constant coefficient (i.e. |L_tac| is the inverse function of + ``Cp_phi``). See files ``plugins/setoid_ring/ZArithRing.v`` + and ``plugins/setoid_ring/RealField.v`` for examples. By default the tactic + does not recognize power expressions as ring expressions. + +sign :n:`@term` + allows ``ring_simplify`` to use a minus operation when + outputting its normal form, i.e writing ``x − y`` instead of ``x + (− y)``. The + term `:n:`@term` is a proof that a given sign function indicates expressions + that are signed (`term` has to be a proof of ``Ring_theory.get_sign``). See + ``plugins/setoid_ring/InitialRing.v`` for examples of sign function. + +div :n:`@term` + allows ``ring`` and ``ring_simplify`` to use monomials with + coefficient other than 1 in the rewriting. The term :n:`@term` is a proof + that a given division function satisfies the specification of an + euclidean division function (:n:`@term` has to be a proof of + ``Ring_theory.div_theory``). For example, this function is called when + trying to rewrite :math:`7x` by :math:`2x = z` to tell that :math:`7 = 3 \times 2 + 1`. See + ``plugins/setoid_ring/InitialRing.v`` for examples of div function. + +Error messages: + +.. exn:: bad ring structure + + The proof of the ring structure provided is not + of the expected type. + +.. exn:: bad lemma for decidability of equality + + The equality function + provided in the case of a computational ring has not the expected + type. + +.. exn:: ring operation should be declared as a morphism + + A setoid associated to the carrier of the ring structure has been found, + but the ring operation should be declared as morphism. See :ref:`tactics-enabled-on-user-provided-relations`. + +How does it work? +---------------------- + +The code of ring is a good example of tactic written using *reflection*. +What is reflection? Basically, it is writing |Coq| tactics in |Coq|, rather +than in |OCaml|. From the philosophical point of view, it is +using the ability of the Calculus of Constructions to speak and reason +about itself. For the ring tactic we used Coq as a programming +language and also as a proof environment to build a tactic and to +prove it correctness. + +The interested reader is strongly advised to have a look at the +file ``Ring_polynom.v``. Here a type for polynomials is defined: + + +.. coqtop:: in + + Inductive PExpr : Type := + | PEc : C -> PExpr + | PEX : positive -> PExpr + | PEadd : PExpr -> PExpr -> PExpr + | PEsub : PExpr -> PExpr -> PExpr + | PEmul : PExpr -> PExpr -> PExpr + | PEopp : PExpr -> PExpr + | PEpow : PExpr -> N -> PExpr. + + +Polynomials in normal form are defined as: + + +.. coqtop:: in + + Inductive Pol : Type := + | Pc : C -> Pol + | Pinj : positive -> Pol -> Pol + | PX : Pol -> positive -> Pol -> Pol. + + +where ``Pinj n P`` denotes ``P`` in which :math:`V_i` is replaced by :math:`V_{i+n}` , +and ``PX P n Q`` denotes :math:`P \otimes V_1^n \oplus Q'`, `Q'` being `Q` where :math:`V_i` is replaced by :math:`V_{i+1}`. + +Variables maps are represented by list of ring elements, and two +interpretation functions, one that maps a variables map and a +polynomial to an element of the concrete ring, and the second one that +does the same for normal forms: + + +.. coqtop:: in + + + Definition PEeval : list R -> PExpr -> R := [...]. + Definition Pphi_dev : list R -> Pol -> R := [...]. + + +A function to normalize polynomials is defined, and the big theorem is +its correctness w.r.t interpretation, that is: + + +.. coqtop:: in + + Definition norm : PExpr -> Pol := [...]. + Lemma Pphi_dev_ok : + forall l pe npe, norm pe = npe -> PEeval l pe == Pphi_dev l npe. + + +So now, what is the scheme for a normalization proof? Let p be the +polynomial expression that the user wants to normalize. First a little +piece of |ML| code guesses the type of `p`, the ring theory `T` to use, an +abstract polynomial `ap` and a variables map `v` such that `p` is |bdi|- +equivalent to ``(PEeval`` `v` `ap`\ ``)``. Then we replace it by ``(Pphi_dev`` `v` +``(norm`` `ap`\ ``))``, using the main correctness theorem and we reduce it to a +concrete expression `p’`, which is the concrete normal form of `p`. This is summarized in this diagram: + +========= ====== ==== +`p` |ra| |re| +\ |eq| \ +`p’` |la| |le| +========= ====== ==== + +The user do not see the right part of the diagram. From outside, the +tactic behaves like a |bdi| simplification extended with AC rewriting +rules. Basically, the proof is only the application of the main +correctness theorem to well-chosen arguments. + +Dealing with fields +------------------------ + +.. tacn:: field + +The ``field`` tactic is an extension of the ``ring`` to deal with rational +expression. Given a rational expression :math:`F = 0`. It first reduces the +expression `F` to a common denominator :math:`N/D = 0` where `N` and `D` +are two ring expressions. For example, if we take :math:`F = (1 − 1/x) x − x + 1`, this +gives :math:`N = (x − 1) x − x^2 + x` and :math:`D = x`. It then calls ring to solve +:math:`N = 0`. +Note that ``field`` also generates non-zero conditions for all the +denominators it encounters in the reduction. In our example, it +generates the condition :math:`x \neq 0`. These conditions appear as one subgoal +which is a conjunction if there are several denominators. Non-zero +conditions are always polynomial expressions. For example when +reducing the expression :math:`1/(1 + 1/x)`, two side conditions are +generated: :math:`x \neq 0` and :math:`x + 1 \neq 0`. Factorized expressions are broken since +a field is an integral domain, and when the equality test on +coefficients is complete w.r.t. the equality of the target field, +constants can be proven different from zero automatically. + +The tactic must be loaded by ``Require Import Field``. New field +structures can be declared to the system with the ``Add Field`` command +(see below). The field of real numbers is defined in module ``RealField`` +(in ``plugins/setoid_ring``). It is exported by module ``Rbase``, so +that requiring ``Rbase`` or ``Reals`` is enough to use the field tactics on +real numbers. Rational numbers in canonical form are also declared as +a field in module ``Qcanon``. + + +.. example:: + + .. coqtop:: all + + Require Import Reals. + Open Scope R_scope. + Goal forall x, + x <> 0 -> (1 - 1 / x) * x - x + 1 = 0. + intros; field; auto. + Abort. + Goal forall x y, + y <> 0 -> y = x -> x / y = 1. + intros x y H H1; field [H1]; auto. + Abort. + +.. tacv:: field [{* @term}] + + decides the equality of two terms modulo + field operations and the equalities defined + by the :n:`@term`\ s. Each :n:`@term` has to be a proof of some equality + `m` ``=`` `p`, where `m` is a monomial (after “abstraction”), `p` a polynomial + and ``=`` the corresponding equality of the field structure. + +.. note:: + + rewriting works with the equality `m` ``=`` `p` only if `p` is a polynomial since + rewriting is handled by the underlying ring tactic. + +.. tacv:: field_simplify + + performs the simplification in the conclusion of the + goal, :math:`F_1 = F_2` becomes :math:`N_1 / D_1 = N_2 / D_2`. A normalization step + (the same as the one for rings) is then applied to :math:`N_1`, :math:`D_1`, + :math:`N_2` and :math:`D_2`. This way, polynomials remain in factorized form during the + fraction simplifications. This yields smaller expressions when + reducing to the same denominator since common factors can be canceled. + +.. tacv:: field_simplify [{* @term }] + + performs the simplification in the conclusion of the goal using the equalities + defined by the :n:`@term`\ s. + +.. tacv:: field_simplify [{* @term }] {* @term } + + performs the simplification in the terms :n:`@terms` of the conclusion of the goal + using the equalities defined by :n:`@term`\ s inside the brackets. + +.. tacv :: field_simplify in @ident + + performs the simplification in the assumption :n:`@ident`. + +.. tacv :: field_simplify [{* @term }] in @ident + + performs the simplification + in the assumption :n:`@ident` using the equalities defined by the :n:`@term`\ s. + +.. tacv:: field_simplify [{* @term }] {* @term } in @ident + + performs the simplification in the :n:`@term`\ s of the assumption :n:`@ident` using the + equalities defined by the :n:`@term`\ s inside the brackets. + +.. tacv:: field_simplify_eq + + performs the simplification in the conclusion of + the goal removing the denominator. :math:`F_1 = F_2` becomes :math:`N_1 D_2 = N_2 D_1`. + +.. tacv:: field_simplify_eq [ {* @term }] + + performs the simplification in + the conclusion of the goal using the equalities defined by + :n:`@term`\ s. + +.. tacv:: field_simplify_eq in @ident + + performs the simplification in the assumption :n:`@ident`. + +.. tacv:: field_simplify_eq [{* @term}] in @ident + + performs the simplification in the assumption :n:`@ident` using the equalities defined by + :n:`@terms`\ s and removing the denominator. + + +Adding a new field structure +--------------------------------- + +Declaring a new field consists in proving that a field signature (a +carrier set, an equality, and field operations: +``Field_theory.field_theory`` and ``Field_theory.semi_field_theory``) +satisfies the field axioms. Semi-fields (fields without + inverse) are +also supported. The equality can be either Leibniz equality, or any +relation declared as a setoid (see :ref:`tactics-enabled-on-user-provided-relations`). The definition of +fields and semi-fields is: + +.. coqtop:: in + + Record field_theory : Prop := mk_field { + F_R : ring_theory rO rI radd rmul rsub ropp req; + F_1_neq_0 : ~ 1 == 0; + Fdiv_def : forall p q, p / q == p * / q; + Finv_l : forall p, ~ p == 0 -> / p * p == 1 + }. + + Record semi_field_theory : Prop := mk_sfield { + SF_SR : semi_ring_theory rO rI radd rmul req; + SF_1_neq_0 : ~ 1 == 0; + SFdiv_def : forall p q, p / q == p * / q; + SFinv_l : forall p, ~ p == 0 -> / p * p == 1 + }. + + +The result of the normalization process is a fraction represented by +the following type: + +.. coqtop:: in + + Record linear : Type := mk_linear { + num : PExpr C; + denum : PExpr C; + condition : list (PExpr C) + }. + + +where ``num`` and ``denum`` are the numerator and denominator; ``condition`` is a +list of expressions that have appeared as a denominator during the +normalization process. These expressions must be proven different from +zero for the correctness of the algorithm. + +The syntax for adding a new field is + +.. cmd:: Add Field @ident : @term {? ( @field_mod {* , @field_mod } )}. + +The :n:`@ident` is not relevant. It is just used for error +messages. :n:`@term` is a proof that the field signature satisfies the +(semi-)field axioms. The optional list of modifiers is used to tailor +the behavior of the tactic. + +.. prodn:: + field_mod := @ring_mod %| completeness @term + +Since field tactics are built upon ``ring`` +tactics, all modifiers of the ``Add Ring`` apply. There is only one +specific modifier: + +completeness :n:`@term` + allows the field tactic to prove automatically + that the image of non-zero coefficients are mapped to non-zero + elements of the field. :n:`@term` is a proof of + + ``forall x y, [x] == [y] -> x ?=! y = true``, + + which is the completeness of equality on coefficients + w.r.t. the field equality. + + +History of ring +-------------------- + +First Samuel Boutin designed the tactic ``ACDSimpl``. This tactic did lot +of rewriting. But the proofs terms generated by rewriting were too big +for |Coq|’s type-checker. Let us see why: + +.. coqtop:: all + + Require Import ZArith. + Open Scope Z_scope. + Goal forall x y z : Z, + x + 3 + y + y * z = x + 3 + y + z * y. + intros; rewrite (Zmult_comm y z); reflexivity. + Save foo. + Print foo. + +At each step of rewriting, the whole context is duplicated in the +proof term. Then, a tactic that does hundreds of rewriting generates +huge proof terms. Since ``ACDSimpl`` was too slow, Samuel Boutin rewrote +it using reflection (see :cite:`Bou97`). Later, it +was rewritten by Patrick Loiseleur: the new tactic does not any +more require ``ACDSimpl`` to compile and it makes use of |bdi|-reduction not +only to replace the rewriting steps, but also to achieve the +interleaving of computation and reasoning (see :ref:`discussion_reflection`). He also wrote a +few |ML| code for the ``Add Ring`` command, that allow to register new rings +dynamically. + +Proofs terms generated by ring are quite small, they are linear in the +number of :math:`\oplus` and :math:`\otimes` operations in the normalized terms. Type-checking +those terms requires some time because it makes a large use of the +conversion rule, but memory requirements are much smaller. + + +.. _discussion_reflection: + + +Discussion +---------------- + + +Efficiency is not the only motivation to use reflection here. ``ring`` +also deals with constants, it rewrites for example the expression +``34 + 2 * x − x + 12`` to the expected result ``x + 46``. +For the tactic ``ACDSimpl``, the only constants were 0 and 1. +So the expression ``34 + 2 * (x − 1) + 12`` +is interpreted as :math:`V_0 \oplus V_1 \otimes (V_2 \ominus 1) \oplus V_3`\ , +with the variables mapping +:math:`\{V_0 \mapsto 34; V_1 \mapsto 2; V_2 \mapsto x; V_3 \mapsto 12\}`\ . +Then it is rewritten to ``34 − x + 2 * x + 12``, very far from the expected result. +Here rewriting is not sufficient: you have to do some kind of reduction +(some kind of computation) to achieve the normalization. + +The tactic ``ring`` is not only faster than a classical one: using +reflection, we get for free integration of computation and reasoning +that would be very complex to implement in the classic fashion. + +Is it the ultimate way to write tactics? The answer is: yes and no. +The ``ring`` tactic uses intensively the conversion rule of |Cic|, that is +replaces proof by computation the most as it is possible. It can be +useful in all situations where a classical tactic generates huge proof +terms. Symbolic Processing and Tautologies are in that case. But there +are also tactics like ``auto`` or ``linear`` that do many complex computations, +using side-effects and backtracking, and generate a small proof term. +Clearly, it would be significantly less efficient to replace them by +tactics using reflection. + +Another idea suggested by Benjamin Werner: reflection could be used to +couple an external tool (a rewriting program or a model checker) +with |Coq|. We define (in |Coq|) a type of terms, a type of *traces*, and +prove a correction theorem that states that *replaying traces* is safe +w.r.t some interpretation. Then we let the external tool do every +computation (using side-effects, backtracking, exception, or others +features that are not available in pure lambda calculus) to produce +the trace: now we can check in |Coq| that the trace has the expected +semantic by applying the correction lemma. + + + + + + +.. rubric:: Footnotes +.. [#f1] based on previous work from Patrick Loiseleur and Samuel Boutin + + + diff --git a/doc/sphinx/addendum/type-classes.rst b/doc/sphinx/addendum/type-classes.rst new file mode 100644 index 0000000000..3e95bd8c45 --- /dev/null +++ b/doc/sphinx/addendum/type-classes.rst @@ -0,0 +1,571 @@ +.. include:: ../replaces.rst + +.. _typeclasses: + +Type Classes +============ + +This chapter presents a quick reference of the commands related to type +classes. For an actual introduction to type classes, there is a +description of the system :cite:`sozeau08` and the literature on type +classes in Haskell which also applies. + + +Class and Instance declarations +------------------------------- + +The syntax for class and instance declarations is the same as the record +syntax of Coq: + +``Class Id (`` |p_1| ``:`` |t_1| ``) ⋯ (`` |p_n| ``:`` |t_n| ``) [: +sort] := {`` |f_1| ``:`` |u_1| ``; ⋮`` |f_m| ``:`` |u_m| ``}.`` + +``Instance ident : Id`` |p_1| ``⋯`` |p_n| ``:= {`` |f_1| ``:=`` |t_1| ``; ⋮`` |f_m| ``:=`` |t_m| ``}.`` + +The |p_i| ``:`` |t_i| variables are called the *parameters* of the class and +the |f_i| ``:`` |t_i| are called the *methods*. Each class definition gives +rise to a corresponding record declaration and each instance is a +regular definition whose name is given by ident and type is an +instantiation of the record type. + +We’ll use the following example class in the rest of the chapter: + +.. coqtop:: in + + Class EqDec (A : Type) := { + eqb : A -> A -> bool ; + eqb_leibniz : forall x y, eqb x y = true -> x = y }. + +This class implements a boolean equality test which is compatible with +Leibniz equality on some type. An example implementation is: + +.. coqtop:: in + + Instance unit_EqDec : EqDec unit := + { eqb x y := true ; + eqb_leibniz x y H := + match x, y return x = y with tt, tt => eq_refl tt end }. + +If one does not give all the members in the Instance declaration, Coq +enters the proof-mode and the user is asked to build inhabitants of +the remaining fields, e.g.: + +.. coqtop:: in + + Instance eq_bool : EqDec bool := + { eqb x y := if x then y else negb y }. + +.. coqtop:: all + + Proof. intros x y H. + +.. coqtop:: all + + destruct x ; destruct y ; (discriminate || reflexivity). + +.. coqtop:: all + + Defined. + +One has to take care that the transparency of every field is +determined by the transparency of the ``Instance`` proof. One can use +alternatively the ``Program Instance`` variant which has richer facilities +for dealing with obligations. + + +Binding classes +--------------- + +Once a type class is declared, one can use it in class binders: + +.. coqtop:: all + + Definition neqb {A} {eqa : EqDec A} (x y : A) := negb (eqb x y). + +When one calls a class method, a constraint is generated that is +satisfied only in contexts where the appropriate instances can be +found. In the example above, a constraint ``EqDec A`` is generated and +satisfied by ``eqa : EqDec A``. In case no satisfying constraint can be +found, an error is raised: + +.. coqtop:: all + + Fail Definition neqb' (A : Type) (x y : A) := negb (eqb x y). + +The algorithm used to solve constraints is a variant of the eauto +tactic that does proof search with a set of lemmas (the instances). It +will use local hypotheses as well as declared lemmas in +the ``typeclass_instances`` database. Hence the example can also be +written: + +.. coqtop:: all + + Definition neqb' A (eqa : EqDec A) (x y : A) := negb (eqb x y). + +However, the generalizing binders should be used instead as they have +particular support for type classes: + ++ They automatically set the maximally implicit status for type class + arguments, making derived functions as easy to use as class methods. + In the example above, ``A`` and ``eqa`` should be set maximally implicit. ++ They support implicit quantification on partially applied type + classes (:ref:`implicit-generalization`). Any argument not given as part of a type class + binder will be automatically generalized. ++ They also support implicit quantification on :ref:`superclasses`. + + +Following the previous example, one can write: + +.. coqtop:: all + + Generalizable Variables A B C. + + Definition neqb_impl `{eqa : EqDec A} (x y : A) := negb (eqb x y). + +Here ``A`` is implicitly generalized, and the resulting function is +equivalent to the one above. + +Parameterized Instances +----------------------- + +One can declare parameterized instances as in Haskell simply by giving +the constraints as a binding context before the instance, e.g.: + +.. coqtop:: in + + Instance prod_eqb `(EA : EqDec A, EB : EqDec B) : EqDec (A * B) := + { eqb x y := match x, y with + | (la, ra), (lb, rb) => andb (eqb la lb) (eqb ra rb) + end }. + +.. coqtop:: none + + Abort. + +These instances are used just as well as lemmas in the instance hint +database. + +Sections and contexts +--------------------- + +To ease the parametrization of developments by type classes, we provide a new +way to introduce variables into section contexts, compatible with the implicit +argument mechanism. The new command works similarly to the :cmd:`Variables` +vernacular, except it accepts any binding context as argument. For example: + +.. coqtop:: all + + Section EqDec_defs. + + Context `{EA : EqDec A}. + + Global Instance option_eqb : EqDec (option A) := + { eqb x y := match x, y with + | Some x, Some y => eqb x y + | None, None => true + | _, _ => false + end }. + Admitted. + + End EqDec_defs. + + About option_eqb. + +Here the Global modifier redeclares the instance at the end of the +section, once it has been generalized by the context variables it +uses. + + +Building hierarchies +-------------------- + +.. _superclasses: + +Superclasses +~~~~~~~~~~~~ + +One can also parameterize classes by other classes, generating a +hierarchy of classes and superclasses. In the same way, we give the +superclasses as a binding context: + +.. coqtop:: all + + Class Ord `(E : EqDec A) := { le : A -> A -> bool }. + +Contrary to Haskell, we have no special syntax for superclasses, but +this declaration is morally equivalent to: + +:: + + Class `(E : EqDec A) => Ord A := + { le : A -> A -> bool }. + + +This declaration means that any instance of the ``Ord`` class must have +an instance of ``EqDec``. The parameters of the subclass contain at +least all the parameters of its superclasses in their order of +appearance (here A is the only one). As we have seen, ``Ord`` is encoded +as a record type with two parameters: a type ``A`` and an ``E`` of type +``EqDec A``. However, one can still use it as if it had a single +parameter inside generalizing binders: the generalization of +superclasses will be done automatically. + +.. coqtop:: all + + Definition le_eqb `{Ord A} (x y : A) := andb (le x y) (le y x). + +In some cases, to be able to specify sharing of structures, one may +want to give explicitly the superclasses. It is is possible to do it +directly in regular binders, and using the ``!`` modifier in class +binders. For example: + +.. coqtop:: all + + Definition lt `{eqa : EqDec A, ! Ord eqa} (x y : A) := andb (le x y) (neqb x y). + +The ``!`` modifier switches the way a binder is parsed back to the regular +interpretation of Coq. In particular, it uses the implicit arguments +mechanism if available, as shown in the example. + +Substructures +~~~~~~~~~~~~~ + +Substructures are components of a class which are instances of a class +themselves. They often arise when using classes for logical +properties, e.g.: + +.. coqtop:: none + + Require Import Relation_Definitions. + +.. coqtop:: in + + Class Reflexive (A : Type) (R : relation A) := + reflexivity : forall x, R x x. + + Class Transitive (A : Type) (R : relation A) := + transitivity : forall x y z, R x y -> R y z -> R x z. + +This declares singleton classes for reflexive and transitive relations, +(see the :ref:`singleton class <singleton-class>` variant for an +explanation). These may be used as part of other classes: + +.. coqtop:: all + + Class PreOrder (A : Type) (R : relation A) := + { PreOrder_Reflexive :> Reflexive A R ; + PreOrder_Transitive :> Transitive A R }. + +The syntax ``:>`` indicates that each ``PreOrder`` can be seen as a +``Reflexive`` relation. So each time a reflexive relation is needed, a +preorder can be used instead. This is very similar to the coercion +mechanism of ``Structure`` declarations. The implementation simply +declares each projection as an instance. + +One can also declare existing objects or structure projections using +the Existing Instance command to achieve the same effect. + + +Summary of the commands +----------------------- + + +.. _Class: + +.. cmd:: Class @ident {? @binders} : {? @sort} := {? @ident} { {+; @ident :{? >} @term } }. + + The ``Class`` command is used to declare a type class with parameters + ``binders`` and fields the declared record fields. + +Variants: + +.. _singleton-class: + +.. cmd:: Class @ident {? @binders} : {? @sort} := @ident : @term + + This variant declares a *singleton* class with a single method. This + singleton class is a so-called definitional class, represented simply + as a definition ``ident binders := term`` and whose instances are + themselves objects of this type. Definitional classes are not wrapped + inside records, and the trivial projection of an instance of such a + class is convertible to the instance itself. This can be useful to + make instances of existing objects easily and to reduce proof size by + not inserting useless projections. The class constant itself is + declared rigid during resolution so that the class abstraction is + maintained. + +.. cmd:: Existing Class @ident + + This variant declares a class a posteriori from a constant or + inductive definition. No methods or instances are defined. + +.. _Instance: + +.. cmd:: Instance @ident {? @binders} : Class t1 … tn [| priority] := { field1 := b1 ; …; fieldi := bi } + +The ``Instance`` command is used to declare a type class instance named +``ident`` of the class ``Class`` with parameters ``t1`` to ``tn`` and +fields ``b1`` to ``bi``, where each field must be a declared field of +the class. Missing fields must be filled in interactive proof mode. + +An arbitrary context of ``binders`` can be put after the name of the +instance and before the colon to declare a parameterized instance. An +optional priority can be declared, 0 being the highest priority as for +auto hints. If the priority is not specified, it defaults to the number +of non-dependent binders of the instance. + +..cmdv:: Instance @ident {? @binders} : forall {? @binders}, Class t1 … tn [| priority] := @term + + This syntax is used for declaration of singleton class instances or + for directly giving an explicit term of type ``forall binders, Class + t1 … tn``. One need not even mention the unique field name for + singleton classes. + +..cmdv:: Global Instance + + One can use the ``Global`` modifier on instances declared in a + section so that their generalization is automatically redeclared + after the section is closed. + +..cmdv:: Program Instance + + Switches the type-checking to Program (chapter :ref:`programs`) and + uses the obligation mechanism to manage missing fields. + +..cmdv:: Declare Instance + + In a Module Type, this command states that a corresponding concrete + instance should exist in any implementation of thisModule Type. This + is similar to the distinction betweenParameter vs. Definition, or + between Declare Module and Module. + + +Besides the ``Class`` and ``Instance`` vernacular commands, there are a +few other commands related to type classes. + +.. _ExistingInstance: + +Existing Instance +~~~~~~~~~~~~~~~~~ + +.. cmd:: Existing Instance {+ @ident} [| priority] + +This commands adds an arbitrary list of constants whose type ends with +an applied type class to the instance database with an optional +priority. It can be used for redeclaring instances at the end of +sections, or declaring structure projections as instances. This is +equivalent to ``Hint Resolve ident : typeclass_instances``, except it +registers instances for ``Print Instances``. + +.. _Context: + +Context +~~~~~~~ + +.. cmd:: Context @binders + +Declares variables according to the given binding context, which might +use :ref:`implicit-generalization`. + +.. tacn:: typeclasses eauto + +This tactic uses a different resolution engine than :tacn:`eauto` and +:tacn:`auto`. The main differences are the following: + ++ Contrary to ``eauto`` and ``auto``, the resolution is done entirely in + the new proof engine (as of Coq v8.6), meaning that backtracking is + available among dependent subgoals, and shelving goals is supported. + typeclasses eauto is a multi-goal tactic. It analyses the dependencies + between subgoals to avoid backtracking on subgoals that are entirely + independent. + ++ When called with no arguments, typeclasses eauto uses + thetypeclass_instances database by default (instead of core). + Dependent subgoals are automatically shelved, and shelved goals can + remain after resolution ends (following the behavior ofCoq 8.5). + *Note: * As of Coq 8.6, all:once (typeclasses eauto) faithfully + mimicks what happens during typeclass resolution when it is called + during refinement/type-inference, except that *only* declared class + subgoals are considered at the start of resolution during type + inference, while “all” can select non-class subgoals as well. It might + move to ``all:typeclasses eauto`` in future versions when the + refinement engine will be able to backtrack. + ++ When called with specific databases (e.g. with), typeclasses eauto + allows shelved goals to remain at any point during search and treat + typeclasses goals like any other. + ++ The transparency information of databases is used consistently for + all hints declared in them. It is always used when calling the + unifier. When considering the local hypotheses, we use the transparent + state of the first hint database given. Using an empty database + (created with Create HintDb for example) with unfoldable variables and + constants as the first argument of typeclasses eauto hence makes + resolution with the local hypotheses use full conversion during + unification. + + +Variants: + +#. ``typeclasses eauto [num]`` + + *Warning:* The semantics for the limit num + is different than for auto. By default, if no limit is given the + search is unbounded. Contrary to auto, introduction steps (intro) are + counted, which might result in larger limits being necessary when + searching with typeclasses eauto than auto. + +#. ``typeclasses eauto with {+ @ident}`` + + This variant runs resolution with the given hint databases. It treats + typeclass subgoals the same as other subgoals (no shelving of + non-typeclass goals in particular). + +.. tacn:: autoapply @term with @ident + :name: autoapply + + The tactic autoapply applies a term using the transparency information + of the hint database ident, and does *no* typeclass resolution. This can + be used in :cmd:`Hint Extern`’s for typeclass instances (in the hint + database ``typeclass_instances``) to allow backtracking on the typeclass + subgoals created by the lemma application, rather than doing type class + resolution locally at the hint application time. + +.. _TypeclassesTransparent: + +Typeclasses Transparent, Typclasses Opaque +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. cmd:: Typeclasses Transparent {+ @ident} + + This command defines makes the identifiers transparent during type class + resolution. + + .. cmdv:: Typeclasses Opaque {+ @ident} + :name: Typeclasses Opaque + + Make the identifiers opaque for typeclass search. It is useful when some + constants prevent some unifications and make resolution fail. It is also + useful to declare constants which should never be unfolded during + proof-search, like fixpoints or anything which does not look like an + abbreviation. This can additionally speed up proof search as the typeclass + map can be indexed by such rigid constants (see + :ref:`thehintsdatabasesforautoandeauto`). + + By default, all constants and local variables are considered transparent. One + should take care not to make opaque any constant that is used to abbreviate a + type, like: + + :: + + relation A := A -> A -> Prop. + + This is equivalent to ``Hint Transparent, Opaque ident : typeclass_instances``. + + +.. opt:: Typeclasses Dependency Order + + This option (on by default since 8.6) respects the dependency order + between subgoals, meaning that subgoals which are depended on by other + subgoals come first, while the non-dependent subgoals were put before + the dependent ones previously (Coq v8.5 and below). This can result in + quite different performance behaviors of proof search. + + +.. opt:: Typeclasses Filtered Unification + + This option, available since Coq 8.6 and off by default, switches the + hint application procedure to a filter-then-unify strategy. To apply a + hint, we first check that the goal *matches* syntactically the + inferred or specified pattern of the hint, and only then try to + *unify* the goal with the conclusion of the hint. This can drastically + improve performance by calling unification less often, matching + syntactic patterns being very quick. This also provides more control + on the triggering of instances. For example, forcing a constant to + explicitely appear in the pattern will make it never apply on a goal + where there is a hole in that place. + + +.. opt:: Typeclasses Limit Intros + + This option (on by default) controls the ability to apply hints while + avoiding (functional) eta-expansions in the generated proof term. It + does so by allowing hints that conclude in a product to apply to a + goal with a matching product directly, avoiding an introduction. + *Warning:* this can be expensive as it requires rebuilding hint + clauses dynamically, and does not benefit from the invertibility + status of the product introduction rule, resulting in potentially more + expensive proof-search (i.e. more useless backtracking). + + +.. opt:: Typeclass Resolution For Conversion + + This option (on by default) controls the use of typeclass resolution + when a unification problem cannot be solved during elaboration/type- + inference. With this option on, when a unification fails, typeclass + resolution is tried before launching unification once again. + + +.. opt:: Typeclasses Strict Resolution + + Typeclass declarations introduced when this option is set have a + stricter resolution behavior (the option is off by default). When + looking for unifications of a goal with an instance of this class, we + “freeze” all the existentials appearing in the goals, meaning that + they are considered rigid during unification and cannot be + instantiated. + + +.. opt:: Typeclasses Unique Solutions + + When a typeclass resolution is launched we ensure that it has a single + solution or fail. This ensures that the resolution is canonical, but + can make proof search much more expensive. + + +.. opt:: Typeclasses Unique Instances + + Typeclass declarations introduced when this option is set have a more + efficient resolution behavior (the option is off by default). When a + solution to the typeclass goal of this class is found, we never + backtrack on it, assuming that it is canonical. + + +Typeclasses eauto `:=` +~~~~~~~~~~~~~~~~~~~~~~ + +.. cmd:: Typeclasses eauto := {? debug} {? {dfs | bfs}} depth + + This command allows more global customization of the type class + resolution tactic. The semantics of the options are: + + + ``debug`` In debug mode, the trace of successfully applied tactics is + printed. + + + ``dfs, bfs`` This sets the search strategy to depth-first search (the + default) or breadth-first search. + + + ``depth`` This sets the depth limit of the search. + + +Set Typeclasses Debug +~~~~~~~~~~~~~~~~~~~~~ + +.. opt:: Typeclasses Debug {? Verbosity @num} + +These options allow to see the resolution steps of typeclasses that are +performed during search. The ``Debug`` option is synonymous to ``Debug +Verbosity 1``, and ``Debug Verbosity 2`` provides more information +(tried tactics, shelving of goals, etc…). + + +.. opt:: Refine Instance Mode + +This options allows to switch the behavior of instance declarations made through +the Instance command. + ++ When it is on (the default), instances that have unsolved holes in + their proof-term silently open the proof mode with the remaining + obligations to prove. + ++ When it is off, they fail with an error instead. diff --git a/doc/sphinx/addendum/universe-polymorphism.rst b/doc/sphinx/addendum/universe-polymorphism.rst new file mode 100644 index 0000000000..c791fc906b --- /dev/null +++ b/doc/sphinx/addendum/universe-polymorphism.rst @@ -0,0 +1,445 @@ +.. include:: ../replaces.rst + +.. _polymorphicuniverses: + +Polymorphic Universes +====================== + +:Author: Matthieu Sozeau + +General Presentation +--------------------- + +.. warning:: + + The status of Universe Polymorphism is experimental. + +This section describes the universe polymorphic extension of |Coq|. +Universe polymorphism makes it possible to write generic definitions +making use of universes and reuse them at different and sometimes +incompatible universe levels. + +A standard example of the difference between universe *polymorphic* +and *monomorphic* definitions is given by the identity function: + +.. coqtop:: in + + Definition identity {A : Type} (a : A) := a. + +By default, constant declarations are monomorphic, hence the identity +function declares a global universe (say ``Top.1``) for its domain. +Subsequently, if we try to self-apply the identity, we will get an +error: + +.. coqtop:: all + + Fail Definition selfid := identity (@identity). + +Indeed, the global level ``Top.1`` would have to be strictly smaller than +itself for this self-application to typecheck, as the type of +:g:`(@identity)` is :g:`forall (A : Type@{Top.1}), A -> A` whose type is itself +:g:`Type@{Top.1+1}`. + +A universe polymorphic identity function binds its domain universe +level at the definition level instead of making it global. + +.. coqtop:: in + + Polymorphic Definition pidentity {A : Type} (a : A) := a. + +.. coqtop:: all + + About pidentity. + +It is then possible to reuse the constant at different levels, like +so: + +.. coqtop:: in + + Definition selfpid := pidentity (@pidentity). + +Of course, the two instances of :g:`pidentity` in this definition are +different. This can be seen when the :opt:`Printing Universes` option is on: + +.. coqtop:: none + + Set Printing Universes. + +.. coqtop:: all + + Print selfpid. + +Now :g:`pidentity` is used at two different levels: at the head of the +application it is instantiated at ``Top.3`` while in the argument position +it is instantiated at ``Top.4``. This definition is only valid as long as +``Top.4`` is strictly smaller than ``Top.3``, as show by the constraints. Note +that this definition is monomorphic (not universe polymorphic), so the +two universes (in this case ``Top.3`` and ``Top.4``) are actually global +levels. + +When printing :g:`pidentity`, we can see the universes it binds in +the annotation :g:`@{Top.2}`. Additionally, when +:g:`Set Printing Universes` is on we print the "universe context" of +:g:`pidentity` consisting of the bound universes and the +constraints they must verify (for :g:`pidentity` there are no constraints). + +Inductive types can also be declared universes polymorphic on +universes appearing in their parameters or fields. A typical example +is given by monoids: + +.. coqtop:: in + + Polymorphic Record Monoid := { mon_car :> Type; mon_unit : mon_car; + mon_op : mon_car -> mon_car -> mon_car }. + +.. coqtop:: in + + Print Monoid. + +The Monoid's carrier universe is polymorphic, hence it is possible to +instantiate it for example with :g:`Monoid` itself. First we build the +trivial unit monoid in :g:`Set`: + +.. coqtop:: in + + Definition unit_monoid : Monoid := + {| mon_car := unit; mon_unit := tt; mon_op x y := tt |}. + +From this we can build a definition for the monoid of :g:`Set`\-monoids +(where multiplication would be given by the product of monoids). + +.. coqtop:: in + + Polymorphic Definition monoid_monoid : Monoid. + refine (@Build_Monoid Monoid unit_monoid (fun x y => x)). + Defined. + +.. coqtop:: all + + Print monoid_monoid. + +As one can see from the constraints, this monoid is “large”, it lives +in a universe strictly higher than :g:`Set`. + +Polymorphic, Monomorphic +------------------------- + +.. cmd:: Polymorphic @definition + + As shown in the examples, polymorphic definitions and inductives can be + declared using the ``Polymorphic`` prefix. + +.. opt:: Universe Polymorphism + + Once enabled, this option will implicitly prepend ``Polymorphic`` to any + definition of the user. + +.. cmd:: Monomorphic @definition + + When the :opt:`Universe Polymorphism` option is set, to make a definition + producing global universe constraints, one can use the ``Monomorphic`` prefix. + +Many other commands support the ``Polymorphic`` flag, including: + +.. TODO add links on each of these? + +- ``Lemma``, ``Axiom``, and all the other “definition” keywords support + polymorphism. + +- ``Variables``, ``Context``, ``Universe`` and ``Constraint`` in a section support + polymorphism. This means that the universe variables (and associated + constraints) are discharged polymorphically over definitions that use + them. In other words, two definitions in the section sharing a common + variable will both get parameterized by the universes produced by the + variable declaration. This is in contrast to a “mononorphic” variable + which introduces global universes and constraints, making the two + definitions depend on the *same* global universes associated to the + variable. + +- :cmd:`Hint Resolve` and :cmd:`Hint Rewrite` will use the auto/rewrite hint + polymorphically, not at a single instance. + +Cumulative, NonCumulative +------------------------- + +Polymorphic inductive types, coinductive types, variants and records can be +declared cumulative using the :g:`Cumulative` prefix. + +.. cmd:: Cumulative @inductive + + Declares the inductive as cumulative + +Alternatively, there is an option :g:`Set Polymorphic Inductive +Cumulativity` which when set, makes all subsequent *polymorphic* +inductive definitions cumulative. When set, inductive types and the +like can be enforced to be non-cumulative using the :g:`NonCumulative` +prefix. + +.. cmd:: NonCumulative @inductive + + Declares the inductive as non-cumulative + +.. opt:: Polymorphic Inductive Cumulativity + + When this option is on, it sets all following polymorphic inductive + types as cumulative (it is off by default). + +Consider the examples below. + +.. coqtop:: in + + Polymorphic Cumulative Inductive list {A : Type} := + | nil : list + | cons : A -> list -> list. + +.. coqtop:: all + + Print list. + +When printing :g:`list`, the universe context indicates the subtyping +constraints by prefixing the level names with symbols. + +Because inductive subtypings are only produced by comparing inductives +to themselves with universes changed, they amount to variance +information: each universe is either invariant, covariant or +irrelevant (there are no contravariant subtypings in Coq), +respectively represented by the symbols `=`, `+` and `*`. + +Here we see that :g:`list` binds an irrelevant universe, so any two +instances of :g:`list` are convertible: :math:`E[Γ] ⊢ \mathsf{list}@\{i\}~A +=_{βδιζη} \mathsf{list}@\{j\}~B` whenever :math:`E[Γ] ⊢ A =_{βδιζη} B` and +this applies also to their corresponding constructors, when +they are comparable at the same type. + +See :ref:`Conversion-rules` for more details on convertibility and subtyping. +The following is an example of a record with non-trivial subtyping relation: + +.. coqtop:: all + + Polymorphic Cumulative Record packType := {pk : Type}. + +:g:`packType` binds a covariant universe, i.e. + +.. math:: + + E[Γ] ⊢ \mathsf{packType}@\{i\} =_{βδιζη} + \mathsf{packType}@\{j\}~\mbox{ whenever }~i ≤ j + +Cumulative inductive types, coninductive types, variants and records +only make sense when they are universe polymorphic. Therefore, an +error is issued whenever the user uses the :g:`Cumulative` or +:g:`NonCumulative` prefix in a monomorphic context. +Notice that this is not the case for the option :g:`Set Polymorphic Inductive Cumulativity`. +That is, this option, when set, makes all subsequent *polymorphic* +inductive declarations cumulative (unless, of course the :g:`NonCumulative` prefix is used) +but has no effect on *monomorphic* inductive declarations. + +Consider the following examples. + +.. coqtop:: all reset + + Monomorphic Cumulative Inductive Unit := unit. + +.. coqtop:: all reset + + Monomorphic NonCumulative Inductive Unit := unit. + +.. coqtop:: all reset + + Set Polymorphic Inductive Cumulativity. + Inductive Unit := unit. + +An example of a proof using cumulativity +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. coqtop:: in + + Set Universe Polymorphism. + Set Polymorphic Inductive Cumulativity. + + Inductive eq@{i} {A : Type@{i}} (x : A) : A -> Type@{i} := eq_refl : eq x x. + + Definition funext_type@{a b e} (A : Type@{a}) (B : A -> Type@{b}) + := forall f g : (forall a, B a), + (forall x, eq@{e} (f x) (g x)) + -> eq@{e} f g. + + Section down. + Universes a b e e'. + Constraint e' < e. + Lemma funext_down {A B} + (H : @funext_type@{a b e} A B) : @funext_type@{a b e'} A B. + Proof. + exact H. + Defined. + End down. + +Cumulativity Weak Constraints +----------------------------- + +.. opt:: Cumulativity Weak Constraints + +This option, on by default, causes "weak" constraints to be produced +when comparing universes in an irrelevant position. Processing weak +constraints is delayed until minimization time. A weak constraint +between `u` and `v` when neither is smaller than the other and +one is flexible causes them to be unified. Otherwise the constraint is +silently discarded. + +This heuristic is experimental and may change in future versions. +Disabling weak constraints is more predictable but may produce +arbitrary numbers of universes. + + +Global and local universes +--------------------------- + +Each universe is declared in a global or local environment before it +can be used. To ensure compatibility, every *global* universe is set +to be strictly greater than :g:`Set` when it is introduced, while every +*local* (i.e. polymorphically quantified) universe is introduced as +greater or equal to :g:`Set`. + + +Conversion and unification +--------------------------- + +The semantics of conversion and unification have to be modified a +little to account for the new universe instance arguments to +polymorphic references. The semantics respect the fact that +definitions are transparent, so indistinguishable from their bodies +during conversion. + +This is accomplished by changing one rule of unification, the first- +order approximation rule, which applies when two applicative terms +with the same head are compared. It tries to short-cut unfolding by +comparing the arguments directly. In case the constant is universe +polymorphic, we allow this rule to fire only when unifying the +universes results in instantiating a so-called flexible universe +variables (not given by the user). Similarly for conversion, if such +an equation of applicative terms fail due to a universe comparison not +being satisfied, the terms are unfolded. This change implies that +conversion and unification can have different unfolding behaviors on +the same development with universe polymorphism switched on or off. + + +Minimization +------------- + +Universe polymorphism with cumulativity tends to generate many useless +inclusion constraints in general. Typically at each application of a +polymorphic constant :g:`f`, if an argument has expected type :g:`Type@{i}` +and is given a term of type :g:`Type@{j}`, a :math:`j ≤ i` constraint will be +generated. It is however often the case that an equation :math:`j = i` would +be more appropriate, when :g:`f`\'s universes are fresh for example. +Consider the following example: + +.. coqtop:: none + + Polymorphic Definition pidentity {A : Type} (a : A) := a. + Set Printing Universes. + +.. coqtop:: in + + Definition id0 := @pidentity nat 0. + +.. coqtop:: all + + Print id0. + +This definition is elaborated by minimizing the universe of :g:`id0` to +level :g:`Set` while the more general definition would keep the fresh level +:g:`i` generated at the application of :g:`id` and a constraint that :g:`Set` :math:`≤ i`. +This minimization process is applied only to fresh universe variables. +It simply adds an equation between the variable and its lower bound if +it is an atomic universe (i.e. not an algebraic max() universe). + +.. opt:: Universe Minimization ToSet + + Turning this option off (it is on by default) disallows minimization + to the sort :g:`Set` and only collapses floating universes between + themselves. + + +Explicit Universes +------------------- + +The syntax has been extended to allow users to explicitly bind names +to universes and explicitly instantiate polymorphic definitions. + +.. cmd:: Universe @ident. + + In the monorphic case, this command declares a new global universe + named :g:`ident`, which can be referred to using its qualified name + as well. Global universe names live in a separate namespace. The + command supports the polymorphic flag only in sections, meaning the + universe quantification will be discharged on each section definition + independently. One cannot mix polymorphic and monomorphic + declarations in the same section. + + +.. cmd:: Constraint @ident @ord @ident. + + This command declares a new constraint between named universes. The + order relation :n:`@ord` can be one of :math:`<`, :math:`≤` or :math:`=`. If consistent, the constraint + is then enforced in the global environment. Like ``Universe``, it can be + used with the ``Polymorphic`` prefix in sections only to declare + constraints discharged at section closing time. One cannot declare a + global constraint on polymorphic universes. + + .. exn:: Undeclared universe @ident. + + .. exn:: Universe inconsistency. + + +Polymorphic definitions +~~~~~~~~~~~~~~~~~~~~~~~ + +For polymorphic definitions, the declaration of (all) universe levels +introduced by a definition uses the following syntax: + +.. coqtop:: in + + Polymorphic Definition le@{i j} (A : Type@{i}) : Type@{j} := A. + +.. coqtop:: all + + Print le. + +During refinement we find that :g:`j` must be larger or equal than :g:`i`, as we +are using :g:`A : Type@{i} <= Type@{j}`, hence the generated constraint. At the +end of a definition or proof, we check that the only remaining +universes are the ones declared. In the term and in general in proof +mode, introduced universe names can be referred to in terms. Note that +local universe names shadow global universe names. During a proof, one +can use :ref:`Show Universes <ShowUniverses>` to display the current context of universes. + +Definitions can also be instantiated explicitly, giving their full +instance: + +.. coqtop:: all + + Check (pidentity@{Set}). + Monomorphic Universes k l. + Check (le@{k l}). + +User-named universes and the anonymous universe implicitly attached to +an explicit :g:`Type` are considered rigid for unification and are never +minimized. Flexible anonymous universes can be produced with an +underscore or by omitting the annotation to a polymorphic definition. + +.. coqtop:: all + + Check (fun x => x) : Type -> Type. + Check (fun x => x) : Type -> Type@{_}. + + Check le@{k _}. + Check le. + +.. opt:: Strict Universe Declaration. + + The command ``Unset Strict Universe Declaration`` allows one to freely use + identifiers for universes without declaring them first, with the + semantics that the first use declares it. In this mode, the universe + names are not associated with the definition or proof once it has been + defined. This is meant mainly for debugging purposes. diff --git a/doc/sphinx/biblio.bib b/doc/sphinx/biblio.bib index 247f32103c..97231c9ecf 100644 --- a/doc/sphinx/biblio.bib +++ b/doc/sphinx/biblio.bib @@ -675,7 +675,6 @@ s}, author = {G. Huet}, booktitle = {A perspective in Theoretical Computer Science. Commemorative Volume for Gift Siromoney}, editor = {R. Narasimhan}, - note = {Also in~\cite{CoC89}}, publisher = {World Scientific Publishing}, title = {{The Constructive Engine}}, year = {1989} @@ -791,8 +790,7 @@ Matching and Term Rewriting}, @TechReport{Leroy90, author = {X. Leroy}, - title = {The {ZINC} experiment: an economical implementation -of the {ML} language}, + title = {The {ZINC} experiment: an economical implementation of the {ML} language}, institution = {INRIA}, number = {117}, year = {1990} @@ -815,11 +813,12 @@ of the {ML} language}, } @inproceedings{Luttik97specificationof, - Author = {Sebastiaan P. Luttik and Eelco Visser}, - Booktitle = {2nd International Workshop on the Theory and Practice of Algebraic Specifications (ASF+SDF'97), Electronic Workshops in Computing}, - Publisher = {Springer-Verlag}, - Title = {Specification of Rewriting Strategies}, - Year = {1997}} + author = {Sebastiaan P. Luttik and Eelco Visser}, + booktitle = {2nd International Workshop on the Theory and Practice of Algebraic Specifications (ASF+SDF'97), Electronic Workshops in Computing}, + publisher = {Springer-Verlag}, + title = {Specification of Rewriting Strategies}, + year = {1997} +} @Book{MaL84, author = {{P. Martin-L\"of}}, diff --git a/doc/sphinx/credits.rst b/doc/sphinx/credits.rst index a60f326454..a756597986 100644 --- a/doc/sphinx/credits.rst +++ b/doc/sphinx/credits.rst @@ -376,7 +376,7 @@ contributed by Jean Goubault was integrated in the basic theories. Pierre Courtieu developed a command and a tactic to reason on the inductive structure of recursively defined functions. -Jacek Chrzszcz designed and implemented the module system of |Coq| whose +Jacek Chrząszcz designed and implemented the module system of |Coq| whose foundations are in Judicaël Courant’s PhD thesis. The development was coordinated by C. Paulin. @@ -478,7 +478,7 @@ Marché and Bruno Barras. Claude Marché coordinated the edition of the Reference Manual for |Coq| V8.0. -Pierre Letouzey and Jacek Chrzszcz respectively maintained the +Pierre Letouzey and Jacek Chrząszcz respectively maintained the extraction tool and module system of |Coq|. Jean-Christophe Filliâtre, Pierre Letouzey, Hugo Herbelin and other @@ -1307,9 +1307,9 @@ features and deprecations, cleanups of the internals of the system along with a few new features. The main user visible changes are: - Kernel: fix a subject reduction failure due to allowing fixpoints - on non-recursive values, which allows to recover full parametricity - for CIC, by Matthieu Sozeau. Handling of evars in the VM (the kernel - still does not accept evars) by Pierre-Marie Pédrot. + on non-recursive values, by Matthieu Sozeau. + Handling of evars in the VM (the kernel still does not accept evars) + by Pierre-Marie Pédrot. - Notations: many improvements on recursive notations and support for destructuring patterns in the syntax of notations by Hugo Herbelin. @@ -1338,7 +1338,14 @@ with a few new features. The main user visible changes are: - Documentation: a large community effort resulted in the migration of the reference manual to the Sphinx documentation tool. The result - is this manual. + is this manual. The new documentation infrastructure (based on Sphinx) + is by Clément Pit-Claudel. The migration was coordinated by Maxime Dénès + and Paul Steckler, with some help of Théo Zimmermann during the + final integration phase. The 14 people who ported the manual are + Calvin Beck, Heiko Becker, Yves Bertot, Maxime Dénès, Richard Ford, + Pierre Letouzey, Assia Mahboubi, Clément Pit-Claudel, + Laurence Rideau, Matthieu Sozeau, Paul Steckler, Enrico Tassi, + Laurent Théry, Nikita Zyuzin. - Tools: experimental ``-mangle-names`` option to coqtop/coqc for linting proof scripts, by Jasper Hugunin. @@ -1366,17 +1373,16 @@ The OPAM repository for |Coq| packages has been maintained by Guillaume Melquiond, Matthieu Sozeau, Enrico Tassi with contributions from many users. A list of packages is available at https://coq.inria.fr/opam/www. -The 40 contributors for this version are Yves Bertot, Joachim -Breitner, Tej Chajed, Arthur Charguéraud, Jacques-Pascal Deplaix, Maxime -Dénès, Jim Fehrle, Yannick Forster, Gaëtan Gilbert, Jason Gross, Samuel -Gruetter, Thomas Hebb, Hugo Herbelin, Jasper Hugunin, Emilio Jesus -Gallego Arias, Ralf Jung, Johannes Kloos, Matej Košík, Robbert Krebbers, -Tony Beta Lambda, Vincent Laporte, Pierre Letouzey, Farzon Lotfi, -Cyprien Mangin, Guillaume Melquiond, Raphaël Monat, Carl Patenaude -Poulin, Pierre-Marie Pédrot, Matthew Ryan, Matt Quinn, Sigurd Schneider, -Bernhard Schommer, Matthieu Sozeau, Arnaud Spiwack, Paul Steckler, -Enrico Tassi, Anton Trunov, Martin Vassor, Vadim Zaliva and Théo -Zimmermann. +The 44 contributors for this version are Yves Bertot, Joachim Breitner, Tej +Chajed, Arthur Charguéraud, Jacques-Pascal Deplaix, Maxime Dénès, Jim Fehrle, +Julien Forest, Yannick Forster, Gaëtan Gilbert, Jason Gross, Samuel Gruetter, +Thomas Hebb, Hugo Herbelin, Jasper Hugunin, Emilio Jesus Gallego Arias, Ralf +Jung, Johannes Kloos, Matej Košík, Robbert Krebbers, Tony Beta Lambda, Vincent +Laporte, Peter LeFanu Lumsdaine, Pierre Letouzey, Farzon Lotfi, Cyprien Mangin, +Guillaume Melquiond, Raphaël Monat, Carl Patenaude Poulin, Pierre-Marie Pédrot, +Clément Pit-Claudel, Matthew Ryan, Matt Quinn, Sigurd Schneider, Bernhard +Schommer, Michael Soegtrop, Matthieu Sozeau, Arnaud Spiwack, Paul Steckler, +Enrico Tassi, Anton Trunov, Martin Vassor, Vadim Zaliva and Théo Zimmermann. Version 8.8 is the third release of |Coq| developed on a time-based development cycle. Its development spanned 6 months from the release of diff --git a/doc/sphinx/index.rst b/doc/sphinx/index.rst index c5d4936b18..2963306075 100644 --- a/doc/sphinx/index.rst +++ b/doc/sphinx/index.rst @@ -16,6 +16,7 @@ Table of contents .. toctree:: :caption: The language + language/gallina-specification-language language/gallina-extensions language/coq-library language/cic @@ -24,7 +25,10 @@ Table of contents .. toctree:: :caption: The proof engine + proof-engine/vernacular-commands + proof-engine/proof-handling proof-engine/tactics + proof-engine/ltac proof-engine/detailed-tactic-examples proof-engine/ssreflect-proof-language @@ -38,15 +42,26 @@ Table of contents :caption: Practical tools practical-tools/coq-commands + practical-tools/utilities practical-tools/coqide .. toctree:: :caption: Addendum addendum/extended-pattern-matching + addendum/implicit-coercions addendum/canonical-structures + addendum/type-classes addendum/omega addendum/micromega + addendum/extraction + addendum/program + addendum/ring + addendum/nsatz + addendum/generalized-rewriting + addendum/parallel-proof-processing + addendum/miscellaneous-extensions + addendum/universe-polymorphism .. toctree:: :caption: Reference diff --git a/doc/sphinx/introduction.rst b/doc/sphinx/introduction.rst index 514745c1bf..4a313df0ce 100644 --- a/doc/sphinx/introduction.rst +++ b/doc/sphinx/introduction.rst @@ -2,7 +2,7 @@ Introduction ------------------------ -This document is the Reference Manual of version of the |Coq| proof +This document is the Reference Manual of the |Coq| proof assistant. A companion volume, the |Coq| Tutorial, is provided for the beginners. It is advised to read the Tutorial first. A book :cite:`CoqArt` on practical uses of the |Coq| system was @@ -60,7 +60,7 @@ continuous reading. However, it has some structure that is explained below. - The first part describes the specification language, |Gallina|. - Chapters :ref:`thegallinaspecificationlanguage` and :ref:`extensionsofgallina` describe the concrete + Chapters :ref:`gallinaspecificationlanguage` and :ref:`extensionsofgallina` describe the concrete syntax as well as the meaning of programs, theorems and proofs in the Calculus of Inductive Constructions. Chapter :ref:`thecoqlibrary` describes the standard library of |Coq|. Chapter :ref:`calculusofinductiveconstructions` is a mathematical description @@ -76,7 +76,7 @@ below. Chapter :ref:`proofhandling`. In Chapter :ref:`tactics`, all commands that realize one or more steps of the proof are presented: we call them *tactics*. The language to combine these tactics into complex proof - strategies is given in Chapter :ref:`thetacticlanguage`. Examples of tactics + strategies is given in Chapter :ref:`ltac`. Examples of tactics are described in Chapter :ref:`detailedexamplesoftactics`. - The third part describes how to extend the syntax of |Coq|. It diff --git a/doc/sphinx/language/cic.rst b/doc/sphinx/language/cic.rst index 7ed6524095..5a2aa0a1f8 100644 --- a/doc/sphinx/language/cic.rst +++ b/doc/sphinx/language/cic.rst @@ -97,7 +97,7 @@ ensure the existence of a mapping of the universes to the positive integers, the graph of constraints must remain acyclic. Typing expressions that violate the acyclicity of the graph of constraints results in a Universe inconsistency error (see also Section -:ref:`TODO-2.10`). +:ref:`printing-universes`). .. _Terms: @@ -373,19 +373,22 @@ following rules. -**Remark**: **Prod-Prop** and **Prod-Set** typing-rules make sense if we consider the -semantic difference between :math:`\Prop` and :math:`\Set`: +.. note:: + **Prod-Prop** and **Prod-Set** typing-rules make sense if we consider the + semantic difference between :math:`\Prop` and :math:`\Set`: -+ All values of a type that has a sort :math:`\Set` are extractable. -+ No values of a type that has a sort :math:`\Prop` are extractable. + + All values of a type that has a sort :math:`\Set` are extractable. + + No values of a type that has a sort :math:`\Prop` are extractable. -**Remark**: We may have :math:`\letin{x}{t:T}{u}` well-typed without having -:math:`((λ x:T.u) t)` well-typed (where :math:`T` is a type of -:math:`t`). This is because the value :math:`t` associated to -:math:`x` may be used in a conversion rule (see Section :ref:`Conversion-rules`). +.. note:: + We may have :math:`\letin{x}{t:T}{u}` well-typed without having + :math:`((λ x:T.u) t)` well-typed (where :math:`T` is a type of + :math:`t`). This is because the value :math:`t` associated to + :math:`x` may be used in a conversion rule + (see Section :ref:`Conversion-rules`). .. _Conversion-rules: @@ -398,9 +401,11 @@ can decide if two programs are *intentionally* equal (one says *convertible*). Convertibility is described in this section. -.. _β-reduction: +.. _beta-reduction: + +β-reduction +~~~~~~~~~~~ -**β-reduction.** We want to be able to identify some terms as we can identify the application of a function to a given argument with its result. For instance the identity function over a given type T can be written @@ -424,9 +429,11 @@ theoretically of great importance but we will not detail them here and refer the interested reader to :cite:`Coq85`. -.. _ι-reduction: +.. _iota-reduction: + +ι-reduction +~~~~~~~~~~~ -**ι-reduction.** A specific conversion rule is associated to the inductive objects in the global environment. We shall give later on (see Section :ref:`Well-formed-inductive-definitions`) the precise rules but it @@ -435,9 +442,11 @@ constructor behaves as expected. This reduction is called ι-reduction and is more precisely studied in :cite:`Moh93,Wer94`. -.. _δ-reduction: +.. _delta-reduction: + +δ-reduction +~~~~~~~~~~~ -**δ-reduction.** We may have variables defined in local contexts or constants defined in the global environment. It is legal to identify such a reference with its value, that is to expand (or unfold) it into its value. This @@ -458,9 +467,11 @@ reduction is called δ-reduction and shows as follows. E[Γ] ⊢ c~\triangleright_δ~t -.. _ζ-reduction: +.. _zeta-reduction: + +ζ-reduction +~~~~~~~~~~~ -**ζ-reduction.** |Coq| allows also to remove local definitions occurring in terms by replacing the defined variable by its value. The declaration being destroyed, this reduction differs from δ-reduction. It is called @@ -475,9 +486,11 @@ destroyed, this reduction differs from δ-reduction. It is called E[Γ] ⊢ \letin{x}{u}{t}~\triangleright_ζ~\subst{t}{x}{u} -.. _η-expansion: +.. _eta-expansion: + +η-expansion +~~~~~~~~~~~ -**η-expansion.** Another important concept is η-expansion. It is legal to identify any term :math:`t` of functional type :math:`∀ x:T, U` with its so-called η-expansion @@ -487,34 +500,38 @@ term :math:`t` of functional type :math:`∀ x:T, U` with its so-called η-expan for :math:`x` an arbitrary variable name fresh in :math:`t`. -**Remark**: We deliberately do not define η-reduction: +.. note:: -.. math:: - λ x:T. (t~x) \not\triangleright_η t + We deliberately do not define η-reduction: -This is because, in general, the type of :math:`t` need not to be convertible -to the type of :math:`λ x:T. (t~x)`. E.g., if we take :math:`f` such that: + .. math:: + λ x:T. (t~x) \not\triangleright_η t -.. math:: - f : ∀ x:\Type(2),\Type(1) + This is because, in general, the type of :math:`t` need not to be convertible + to the type of :math:`λ x:T. (t~x)`. E.g., if we take :math:`f` such that: + + .. math:: + f : ∀ x:\Type(2),\Type(1) -then + then -.. math:: - λ x:\Type(1),(f~x) : ∀ x:\Type(1),\Type(1) + .. math:: + λ x:\Type(1),(f~x) : ∀ x:\Type(1),\Type(1) -We could not allow + We could not allow -.. math:: - λ x:Type(1),(f x) \triangleright_η f + .. math:: + λ x:Type(1),(f x) \triangleright_η f -because the type of the reduced term :math:`∀ x:\Type(2),\Type(1)` would not be -convertible to the type of the original term :math:`∀ x:\Type(1),\Type(1).` + because the type of the reduced term :math:`∀ x:\Type(2),\Type(1)` would not be + convertible to the type of the original term :math:`∀ x:\Type(1),\Type(1).` -.. _Convertibility: +.. _convertibility: + +Convertibility +~~~~~~~~~~~~~~ -**Convertibility.** Let us write :math:`E[Γ] ⊢ t \triangleright u` for the contextual closure of the relation :math:`t` reduces to :math:`u` in the global environment :math:`E` and local context :math:`Γ` with one of the previous @@ -704,8 +721,6 @@ called the *context of parameters*. Furthermore, we must have that each :math:`T` in :math:`(t:T)∈Γ_I` can be written as: :math:`∀Γ_P,∀Γ_{\mathit{Arr}(t)}, S` where :math:`Γ_{\mathit{Arr}(t)}` is called the *Arity* of the inductive type t and :math:`S` is called the sort of the inductive type t (not to be confused with :math:`\Sort` which is the set of sorts). - - ** Examples** The declaration for parameterized lists is: .. math:: @@ -794,18 +809,18 @@ contains an inductive declaration. --------------------- E[Γ] ⊢ c : C -**Example.** -Provided that our environment :math:`E` contains inductive definitions we showed before, -these two inference rules above enable us to conclude that: +.. example:: + Provided that our environment :math:`E` contains inductive definitions we showed before, + these two inference rules above enable us to conclude that: -.. math:: - \begin{array}{l} + .. math:: + \begin{array}{l} E[Γ] ⊢ \even : \nat→\Prop\\ E[Γ] ⊢ \odd : \nat→\Prop\\ E[Γ] ⊢ \even\_O : \even~O\\ E[Γ] ⊢ \even\_S : \forall~n:\nat, \odd~n → \even~(S~n)\\ E[Γ] ⊢ \odd\_S : \forall~n:\nat, \even~n → \odd~(S~n) - \end{array} + \end{array} @@ -820,8 +835,9 @@ to inconsistent systems. We restrict ourselves to definitions which satisfy a syntactic criterion of positivity. Before giving the formal rules, we need a few definitions: +Arity of a given sort ++++++++++++++++++++++ -**Type is an Arity of Sort S.** A type :math:`T` is an *arity of sort s* if it converts to the sort s or to a product :math:`∀ x:T,U` with :math:`U` an arity of sort s. @@ -831,7 +847,8 @@ product :math:`∀ x:T,U` with :math:`U` an arity of sort s. :math:`\Prop`. -**Type is an Arity.** +Arity ++++++ A type :math:`T` is an *arity* if there is a :math:`s∈ \Sort` such that :math:`T` is an arity of sort s. @@ -841,32 +858,34 @@ sort s. :math:`A→ Set` and :math:`∀ A:\Prop,A→ \Prop` are arities. -**Type of Constructor of I.** +Type constructor +++++++++++++++++ We say that T is a *type of constructor of I* in one of the following two cases: - + :math:`T` is :math:`(I~t_1 … t_n )` + :math:`T` is :math:`∀ x:U,T'` where :math:`T'` is also a type of constructor of :math:`I` - - .. example:: :math:`\nat` and :math:`\nat→\nat` are types of constructor of :math:`\nat`. :math:`∀ A:Type,\List~A` and :math:`∀ A:Type,A→\List~A→\List~A` are types of constructor of :math:`\List`. -**Positivity Condition.** +.. _positivity: + +Positivity Condition +++++++++++++++++++++ + The type of constructor :math:`T` will be said to *satisfy the positivity condition* for a constant :math:`X` in the following cases: - + :math:`T=(X~t_1 … t_n )` and :math:`X` does not occur free in any :math:`t_i` + :math:`T=∀ x:U,V` and :math:`X` occurs only strictly positively in :math:`U` and the type :math:`V` satisfies the positivity condition for :math:`X`. - -**Occurs Strictly Positively.** +Strict positivity ++++++++++++++++++ + The constant :math:`X` *occurs strictly positively* in :math:`T` in the following cases: @@ -886,11 +905,12 @@ cases: any of the :math:`t_i`, and the (instantiated) types of constructor :math:`\subst{C_i}{p_j}{a_j}_{j=1… m}` of :math:`I` satisfy the nested positivity condition for :math:`X` -**Nested Positivity Condition.** +Nested Positivity ++++++++++++++++++ + The type of constructor :math:`T` of :math:`I` *satisfies the nested positivity condition* for a constant :math:`X` in the following cases: - + :math:`T=(I~b_1 … b_m~u_1 … u_p)`, :math:`I` is an inductive definition with :math:`m` parameters and :math:`X` does not occur in any :math:`u_i` + :math:`T=∀ x:U,V` and :math:`X` occurs only strictly positively in :math:`U` and the type :math:`V` @@ -937,12 +957,11 @@ For instance, if one considers the type │ ╰─ list satisfies the positivity condition for list A ... (bullet 1) - - - .. _Correctness-rules: -**Correctness rules.** +Correctness rules ++++++++++++++++++ + We shall now describe the rules allowing the introduction of a new inductive definition. @@ -1009,7 +1028,9 @@ has type :math:`\Type(k)` with :math:`k<j` and :math:`k≤ i`. .. _Template-polymorphism: -**Template polymorphism.** +Template polymorphism ++++++++++++++++++++++ + Inductive types declared in Type are polymorphic over their arguments in Type. If :math:`A` is an arity of some sort and s is a sort, we write :math:`A_{/s}` for the arity obtained from :math:`A` by replacing its sort with s. @@ -1053,7 +1074,7 @@ provided that the following side conditions hold: we have :math:`(E[Γ_{I′} ;Γ_{P′}] ⊢ C_i : s_{q_i})_{i=1… n}` ; + the sorts :math:`s_i` are such that all eliminations, to :math:`\Prop`, :math:`\Set` and :math:`\Type(j)`, are allowed - (see Section Destructors_). + (see Section :ref:`Destructors`). @@ -1083,14 +1104,14 @@ The sorts :math:`s_j` are chosen canonically so that each :math:`s_j` is minimal respect to the hierarchy :math:`\Prop ⊂ \Set_p ⊂ \Type` where :math:`\Set_p` is predicative :math:`\Set`. More precisely, an empty or small singleton inductive definition (i.e. an inductive definition of which all inductive types are -singleton – see paragraph Destructors_) is set in :math:`\Prop`, a small non-singleton +singleton – see Section :ref:`Destructors`) is set in :math:`\Prop`, a small non-singleton inductive type is set in :math:`\Set` (even in case :math:`\Set` is impredicative – see Section The-Calculus-of-Inductive-Construction-with-impredicative-Set_), and otherwise in the Type hierarchy. Note that the side-condition about allowed elimination sorts in the rule **Ind-Family** is just to avoid to recompute the allowed elimination -sorts at each instance of a pattern-matching (see section Destructors_). As +sorts at each instance of a pattern-matching (see Section :ref:`Destructors`). As an example, let us consider the following definition: .. example:: @@ -1106,7 +1127,7 @@ in the Type hierarchy. Here, the parameter :math:`A` has this property, hence, if :g:`option` is applied to a type in :math:`\Set`, the result is in :math:`\Set`. Note that if :g:`option` is applied to a type in :math:`\Prop`, then, the result is not set in :math:`\Prop` but in :math:`\Set` still. This is because :g:`option` is not a singleton type -(see section Destructors_) and it would lose the elimination to :math:`\Set` and :math:`\Type` +(see Section :ref:`Destructors`) and it would lose the elimination to :math:`\Set` and :math:`\Type` if set in :math:`\Prop`. .. example:: @@ -1135,9 +1156,10 @@ eliminations schemes are allowed. Check (fun (A:Prop) (B:Set) => prod A B). Check (fun (A:Type) (B:Prop) => prod A B). -Remark: Template polymorphism used to be called “sort-polymorphism of -inductive types” before universe polymorphism (see Chapter :ref:`polymorphicuniverses`) was -introduced. +.. note:: + Template polymorphism used to be called “sort-polymorphism of + inductive types” before universe polymorphism + (see Chapter :ref:`polymorphicuniverses`) was introduced. .. _Destructors: @@ -1213,9 +1235,11 @@ Coquand in :cite:`Coq92`. One is the definition by pattern-matching. The second one is a definition by guarded fixpoints. -.. _The-match…with-end-construction: +.. _match-construction: + +The match ... with ... end construction ++++++++++++++++++++++++++++++++++++++++ -**The match…with …end construction** The basic idea of this operator is that we have an object :math:`m` in an inductive type :math:`I` and we want to prove a property which possibly depends on :math:`m`. For this, it is enough to prove the property for @@ -1272,7 +1296,7 @@ and :math:`I:A` and :math:`λ a x . P : B` then by :math:`[I:A|B]` we mean that :math:`λ a x . P` with :math:`m` in the above match-construct. -.. _Notations: +.. _cic_notations: **Notations.** The :math:`[I:A|B]` is defined as the smallest relation satisfying the following rules: We write :math:`[I|B]` for :math:`[I:A|B]` where :math:`A` is the type of :math:`I`. @@ -1473,20 +1497,20 @@ definition :math:`\ind{r}{Γ_I}{Γ_C}` with :math:`Γ_C = [c_1 :C_1 ;…;c_n :C_ -**Example.** -Below is a typing rule for the term shown in the previous example: +.. example:: + Below is a typing rule for the term shown in the previous example: -.. inference:: list example + .. inference:: list example - \begin{array}{l} - E[Γ] ⊢ t : (\List ~\nat) \\ - E[Γ] ⊢ P : B \\ - [(\List ~\nat)|B] \\ - E[Γ] ⊢ f_1 : {(\kw{nil} ~\nat)}^P \\ - E[Γ] ⊢ f_2 : {(\kw{cons} ~\nat)}^P - \end{array} - ------------------------------------------------ - E[Γ] ⊢ \case(t,P,f_1 |f_2 ) : (P~t) + \begin{array}{l} + E[Γ] ⊢ t : (\List ~\nat) \\ + E[Γ] ⊢ P : B \\ + [(\List ~\nat)|B] \\ + E[Γ] ⊢ f_1 : {(\kw{nil} ~\nat)}^P \\ + E[Γ] ⊢ f_2 : {(\kw{cons} ~\nat)}^P + \end{array} + ------------------------------------------------ + E[Γ] ⊢ \case(t,P,f_1 |f_2 ) : (P~t) .. _Definition-of-ι-reduction: @@ -1619,9 +1643,8 @@ Given a variable :math:`y` of type an inductive definition in a declaration ones in which one of the :math:`I_l` occurs) are structurally smaller than y. -The following definitions are correct, we enter them using the ``Fixpoint`` -command as described in Section :ref:`TODO-1.3.4` and show the internal -representation. +The following definitions are correct, we enter them using the :cmd:`Fixpoint` +command and show the internal representation. .. example:: .. coqtop:: all @@ -1678,7 +1701,7 @@ possible: **Mutual induction** The principles of mutual induction can be automatically generated -using the Scheme command described in Section :ref:`TODO-13.1`. +using the Scheme command described in Section :ref:`proofschemes-induction-principles`. .. _Admissible-rules-for-global-environments: diff --git a/doc/sphinx/language/coq-library.rst b/doc/sphinx/language/coq-library.rst index 29053d6a57..6af6e78972 100644 --- a/doc/sphinx/language/coq-library.rst +++ b/doc/sphinx/language/coq-library.rst @@ -5,9 +5,6 @@ The |Coq| library ================= -:Source: https://coq.inria.fr/distrib/current/refman/stdlib.html -:Converted by: Pierre Letouzey - .. index:: single: Theories @@ -22,7 +19,7 @@ The |Coq| library is structured into two parts: developments of |Coq| axiomatizations about sets, lists, sorting, arithmetic, etc. This library comes with the system and its modules are directly accessible through the ``Require`` command (see - Section :ref:`TODO-6.5.1-Require`); + Section :ref:`compiled-files`); In addition, user-provided libraries or developments are provided by |Coq| users' community. These libraries and developments are available @@ -51,6 +48,7 @@ at the |Coq| root directory; this includes the modules ``Tactics``. Module ``Logic_Type`` also makes it in the initial state. +.. _init-notations: Notations ~~~~~~~~~ @@ -93,6 +91,8 @@ Notation Precedence Associativity ``_ ^ _`` 30 right ================ ============ =============== +.. _coq-library-logic: + Logic ~~~~~ @@ -524,7 +524,7 @@ provides a scope ``nat_scope`` gathering standard notations for common operations (``+``, ``*``) and a decimal notation for numbers, allowing for instance to write ``3`` for :g:`S (S (S O)))`. This also works on the left hand side of a ``match`` expression (see for example -section :ref:`TODO-refine-example`). This scope is opened by default. +section :tacn:`refine`). This scope is opened by default. .. example:: @@ -756,7 +756,7 @@ subdirectories: These directories belong to the initial load path of the system, and the modules they provide are compiled at installation time. So they are directly accessible with the command ``Require`` (see -Section :ref:`TODO-6.5.1-Require`). +Section :ref:`compiled-files`). The different modules of the |Coq| standard library are documented online at http://coq.inria.fr/stdlib. @@ -930,9 +930,8 @@ tactics (see Chapter :ref:`tactics`), there are also: Goal forall x y z:R, x * y * z <> 0. intros; split_Rmult. -These tactics has been written with the tactic language Ltac -described in Chapter :ref:`thetacticlanguage`. - +These tactics has been written with the tactic language |Ltac| +described in Chapter :ref:`ltac`. List library ~~~~~~~~~~~~ diff --git a/doc/sphinx/language/gallina-extensions.rst b/doc/sphinx/language/gallina-extensions.rst index d618d90ad2..1a7628d893 100644 --- a/doc/sphinx/language/gallina-extensions.rst +++ b/doc/sphinx/language/gallina-extensions.rst @@ -41,7 +41,9 @@ Remark that the type of a particular identifier may depend on a previously-given order of the fields is important. Finally, each `param` is a parameter of the record. More generally, a record may have explicitly defined (a.k.a. manifest) -fields. For instance, we might have:: +fields. For instance, we might have: + +.. coqtop:: in Record ident param : sort := { ident₁ : type₁ ; ident₂ := term₂ ; ident₃ : type₃ }. @@ -50,6 +52,8 @@ may depend on |ident_1|. .. example:: + The set of rational numbers may be defined as: + .. coqtop:: reset all Record Rat : Set := mkRat @@ -144,7 +148,7 @@ available: It can be activated for printing with -.. cmd:: Set Printing Projections. +.. opt:: Printing Projections .. example:: @@ -169,7 +173,7 @@ and the syntax `term.(@qualid` |term_1| |term_n| `)` to `@qualid` |term_1| `…` In each case, `term` is the object projected and the other arguments are the parameters of the inductive type. -.. note::. Records defined with the ``Record`` keyword are not allowed to be +.. note:: Records defined with the ``Record`` keyword are not allowed to be recursive (references to the record's name in the type of its field raises an error). To define recursive records, one can use the ``Inductive`` and ``CoInductive`` keywords, resulting in an inductive or co-inductive record. @@ -179,9 +183,9 @@ other arguments are the parameters of the inductive type. .. note:: Induction schemes are automatically generated for inductive records. Automatic generation of induction schemes for non-recursive records defined with the ``Record`` keyword can be activated with the - ``Nonrecursive Elimination Schemes`` option (see :ref:`TODO-13.1.1-nonrecursive-elimination-schemes`). + ``Nonrecursive Elimination Schemes`` option (see :ref:`proofschemes-induction-principles`). -.. note::``Structure`` is a synonym of the keyword ``Record``. +.. note:: ``Structure`` is a synonym of the keyword ``Record``. .. warn:: @ident cannot be defined. @@ -189,9 +193,9 @@ other arguments are the parameters of the inductive type. This message is followed by an explanation of this impossibility. There may be three reasons: - #. The name `ident` already exists in the environment (see Section :ref:`TODO-1.3.1-axioms`). + #. The name `ident` already exists in the environment (see :cmd:`Axiom`). #. The body of `ident` uses an incorrect elimination for - `ident` (see Sections :ref:`TODO-1.3.4-fixpoint` and :ref:`TODO-4.5.3-case-expr`). + `ident` (see :cmd:`Fixpoint` and :ref:`Destructors`). #. The type of the projections `ident` depends on previous projections which themselves could not be defined. @@ -208,16 +212,18 @@ other arguments are the parameters of the inductive type. During the definition of the one-constructor inductive definition, all the errors of inductive definitions, as described in Section -:ref:`TODO-1.3.3-inductive-definitions`, may also occur. +:ref:`gallina-inductive-definitions`, may also occur. -**See also** Coercions and records in Section :ref:`TODO-18.9-coercions-and-records` of the chapter devoted to coercions. +**See also** Coercions and records in Section :ref:`coercions-classes-as-records` of the chapter devoted to coercions. .. _primitive_projections: Primitive Projections ~~~~~~~~~~~~~~~~~~~~~ -The option ``Set Primitive Projections`` turns on the use of primitive +.. opt:: Primitive Projections + +Turns on the use of primitive projections when defining subsequent records (even through the ``Inductive`` and ``CoInductive`` commands). Primitive projections extended the Calculus of Inductive Constructions with a new binary @@ -229,21 +235,27 @@ terms when manipulating parameterized records and typechecking time. On the user level, primitive projections can be used as a replacement for the usual defined ones, although there are a few notable differences. -The internally omitted parameters can be reconstructed at printing time -even though they are absent in the actual AST manipulated by the kernel. This -can be obtained by setting the ``Printing Primitive Projection Parameters`` -flag. Another compatibility printing can be activated thanks to the -``Printing Primitive Projection Compatibility`` option which governs the +.. opt:: Printing Primitive Projection Parameters + +This compatibility option reconstructs internally omitted parameters at +printing time (even though they are absent in the actual AST manipulated +by the kernel). + +.. opt:: Printing Primitive Projection Compatibility + +This compatibility option (on by default) governs the printing of pattern-matching over primitive records. Primitive Record Types ++++++++++++++++++++++ -When the ``Set Primitive Projections`` option is on, definitions of +When the :opt:`Primitive Projections` option is on, definitions of record types change meaning. When a type is declared with primitive projections, its :g:`match` construct is disabled (see :ref:`primitive_projections` though). To eliminate the (co-)inductive type, one must use its defined primitive projections. +.. The following paragraph is quite redundant with what is above + For compatibility, the parameters still appear to the user when printing terms even though they are absent in the actual AST manipulated by the kernel. This can be changed by unsetting the @@ -304,7 +316,7 @@ printed back as :g:`match` constructs. Variants and extensions of :g:`match` ------------------------------------- -.. _extended pattern-matching: +.. _mult-match: Multiple and nested pattern-matching ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -316,10 +328,11 @@ patterns are allowed, as in ML-like languages. The extension just acts as a macro that is expanded during parsing into a sequence of match on simple patterns. Especially, a construction defined using the extended match is generally printed -under its expanded form (see ``Set Printing Matching`` in :ref:`controlling-match-pp`). +under its expanded form (see :opt:`Printing Matching`). -See also: :ref:`extended pattern-matching`. +See also: :ref:`extendedpatternmatching`. +.. _if-then-else: Pattern-matching on boolean values: the if expression ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -462,116 +475,63 @@ of :g:`match` expressions. Printing nested patterns +++++++++++++++++++++++++ +.. opt:: Printing Matching. + The Calculus of Inductive Constructions knows pattern-matching only over simple patterns. It is however convenient to re-factorize nested pattern-matching into a single pattern-matching over a nested -pattern. |Coq|’s printer tries to do such limited re-factorization. - -.. cmd:: Set Printing Matching. - -This tells |Coq| to try to use nested patterns. This is the default -behavior. +pattern. -.. cmd:: Unset Printing Matching. +When this option is on (default), |Coq|’s printer tries to do such +limited re-factorization. +Turning it off tells |Coq| to print only simple pattern-matching problems +in the same way as the |Coq| kernel handles them. -This tells |Coq| to print only simple pattern-matching problems in the -same way as the |Coq| kernel handles them. - -.. cmd:: Test Printing Matching. - -This tells if the printing matching mode is on or off. The default is -on. Factorization of clauses with same right-hand side ++++++++++++++++++++++++++++++++++++++++++++++++++ +.. opt:: Printing Factorizable Match Patterns. + When several patterns share the same right-hand side, it is additionally possible to share the clauses using disjunctive patterns. Assuming that the -printing matching mode is on, whether |Coq|'s printer shall try to do this kind -of factorization is governed by the following commands: - -.. cmd:: Set Printing Factorizable Match Patterns. - -This tells |Coq|'s printer to try to use disjunctive patterns. This is the -default behavior. - -.. cmd:: Unset Printing Factorizable Match Patterns. - -This tells |Coq|'s printer not to try to use disjunctive patterns. - -.. cmd:: Test Printing Factorizable Match Patterns. - -This tells if the factorization of clauses with same right-hand side is on or -off. +printing matching mode is on, this option (on by default) tells |Coq|'s +printer to try to do this kind of factorization. Use of a default clause +++++++++++++++++++++++ +.. opt:: Printing Allow Default Clause. + When several patterns share the same right-hand side which do not depend on the arguments of the patterns, yet an extra factorization is possible: the disjunction of patterns can be replaced with a `_` default clause. Assuming that -the printing matching mode and the factorization mode are on, whether |Coq|'s -printer shall try to use a default clause is governed by the following commands: - -.. cmd:: Set Printing Allow Default Clause. - -This tells |Coq|'s printer to use a default clause when relevant. This is the -default behavior. - -.. cmd:: Unset Printing Allow Default Clause. - -This tells |Coq|'s printer not to use a default clause. - -.. cmd:: Test Printing Allow Default Clause. - -This tells if the use of a default clause is allowed. +the printing matching mode and the factorization mode are on, this option (on by +default) tells |Coq|'s printer to use a default clause when relevant. Printing of wildcard patterns ++++++++++++++++++++++++++++++ -Some variables in a pattern may not occur in the right-hand side of -the pattern-matching clause. There are options to control the display -of these variables. - -.. cmd:: Set Printing Wildcard. +.. opt:: Printing Wildcard. -The variables having no occurrences in the right-hand side of the +Some variables in a pattern may not occur in the right-hand side of +the pattern-matching clause. When this option is on (default), the +variables having no occurrences in the right-hand side of the pattern-matching clause are just printed using the wildcard symbol “_”. -.. cmd:: Unset Printing Wildcard. - -The variables, even useless, are printed using their usual name. But -some non-dependent variables have no name. These ones are still -printed using a “_”. - -.. cmd:: Test Printing Wildcard. - -This tells if the wildcard printing mode is on or off. The default is -to print wildcard for useless variables. - Printing of the elimination predicate +++++++++++++++++++++++++++++++++++++ +.. opt:: Printing Synth. + In most of the cases, the type of the result of a matched term is mechanically synthesizable. Especially, if the result type does not -depend of the matched term. - -.. cmd:: Set Printing Synth. - -The result type is not printed when |Coq| knows that it can re- +depend of the matched term. When this option is on (default), +the result type is not printed when |Coq| knows that it can re- synthesize it. -.. cmd:: Unset Printing Synth. - -This forces the result type to be always printed. - -.. cmd:: Test Printing Synth. - -This tells if the non-printing of synthesizable types is on or off. -The default is to not print synthesizable types. - Printing matching on irrefutable patterns ++++++++++++++++++++++++++++++++++++++++++ @@ -667,7 +627,7 @@ The following experimental command is available when the ``FunInd`` library has This command can be seen as a generalization of ``Fixpoint``. It is actually a wrapper for several ways of defining a function *and other useful related objects*, namely: an induction principle that reflects the recursive -structure of the function (see Section :ref:`TODO-8.5.5-functional-induction`) and its fixpoint equality. +structure of the function (see :tacn:`function induction`) and its fixpoint equality. The meaning of this declaration is to define a function ident, similarly to ``Fixpoint`. Like in ``Fixpoint``, the decreasing argument must be given (unless the function is not recursive), but it might not @@ -680,8 +640,8 @@ The ``Function`` construction also enjoys the ``with`` extension to define mutually recursive definitions. However, this feature does not work for non structurally recursive functions. -See the documentation of functional induction (:ref:`TODO-8.5.5-functional-induction`) -and ``Functional Scheme`` (:ref:`TODO-13.2-functional-scheme`) for how to use +See the documentation of functional induction (:tacn:`function induction`) +and ``Functional Scheme`` (:ref:`functional-scheme`) for how to use the induction principle to easily reason about the function. Remark: To obtain the right principle, it is better to put rigid @@ -752,7 +712,7 @@ terminating functions. `functional inversion` will not be available for the function. -See also: :ref:`TODO-13.2-generating-ind-principles` and ref:`TODO-8.5.5-functional-induction` +See also: :ref:`functional-scheme` and :tacn:`function induction` Depending on the ``{…}`` annotation, different definition mechanisms are used by ``Function``. A more precise description is given below. @@ -763,7 +723,7 @@ used by ``Function``. A more precise description is given below. the following are defined: + `ident_rect`, `ident_rec` and `ident_ind`, which reflect the pattern - matching structure of `term` (see the documentation of :ref:`TODO-1.3.3-Inductive`); + matching structure of `term` (see :cmd:`Inductive`); + The inductive `R_ident` corresponding to the graph of `ident` (silently); + `ident_complete` and `ident_correct` which are inversion information linking the function and its graph. @@ -812,13 +772,14 @@ used by ``Function``. A more precise description is given below. hand. Remark: Proof obligations are presented as several subgoals belonging to a Lemma `ident`\ :math:`_{\sf tcc}`. +.. _section-mechanism: Section mechanism ----------------- The sectioning mechanism can be used to to organize a proof in structured sections. Then local declarations become available (see -Section :ref:`TODO-1.3.2-Definitions`). +Section :ref:`gallina-definitions`). .. cmd:: Section @ident. @@ -888,7 +849,7 @@ together, as well as a means of massive abstraction. In the syntax of module application, the ! prefix indicates that any `Inline` directive in the type of the functor arguments will be ignored -(see :ref:`named_module_type` below). +(see the ``Module Type`` command below). .. cmd:: Module @ident. @@ -974,8 +935,6 @@ Reserved commands inside an interactive module is equivalent to an interactive module where each `module_expression` is included. -.. _named_module_type: - .. cmd:: Module Type @ident. This command is used to start an interactive module type `ident`. @@ -996,7 +955,8 @@ Reserved commands inside an interactive module type: is a shortcut for the command ``Include`` `module` for each `module`. -.. cmd:: @assumption_keyword Inline @assums. +.. cmd:: @assumption_keyword Inline @assums + :name: Inline The instance of this assumption will be automatically expanded at functor application, except when this functor application is prefixed by a ``!`` annotation. @@ -1188,24 +1148,24 @@ some of the fields and give one of its possible implementations: Notice that ``M`` is a correct body for the component ``M2`` since its ``T`` component is equal ``nat`` and hence ``M1.T`` as specified. -**Remarks:** +.. note:: -#. Modules and module types can be nested components of each other. -#. One can have sections inside a module or a module type, but not a - module or a module type inside a section. -#. Commands like ``Hint`` or ``Notation`` can also appear inside modules and - module types. Note that in case of a module definition like: + #. Modules and module types can be nested components of each other. + #. One can have sections inside a module or a module type, but not a + module or a module type inside a section. + #. Commands like ``Hint`` or ``Notation`` can also appear inside modules and + module types. Note that in case of a module definition like: -:: + :: - Module N : SIG := M. + Module N : SIG := M. -or:: + or:: - Module N : SIG. … End N. + Module N : SIG. … End N. -hints and the like valid for ``N`` are not those defined in ``M`` (or the module body) but the ones defined -in ``SIG``. + hints and the like valid for ``N`` are not those defined in ``M`` + (or the module body) but the ones defined in ``SIG``. .. _import_qualid: @@ -1236,7 +1196,7 @@ in ``SIG``. Check T. Some features defined in modules are activated only when a module is -imported. This is for instance the case of notations (see :ref:`TODO-12.1-Notations`). +imported. This is for instance the case of notations (see :ref:`Notations`). Declarations made with the Local flag are never imported by theImport command. Such declarations are only accessible through their fully @@ -1282,13 +1242,11 @@ qualified name. This option (off by default) disables the printing of the types of fields, leaving only their names, for the commands ``Print Module`` and ``Print Module Type``. -.. cmd:: Locate Module @qualid. - - Prints the full name of the module `qualid`. - Libraries and qualified names --------------------------------- +.. _names-of-libraries: + Names of libraries ~~~~~~~~~~~~~~~~~~ @@ -1296,15 +1254,16 @@ The theories developed in |Coq| are stored in *library files* which are hierarchically classified into *libraries* and *sublibraries*. To express this hierarchy, library names are represented by qualified identifiers qualid, i.e. as list of identifiers separated by dots (see -:ref:`TODO-1.2.3-identifiers`). For instance, the library file ``Mult`` of the standard +:ref:`gallina-identifiers`). For instance, the library file ``Mult`` of the standard |Coq| library ``Arith`` is named ``Coq.Arith.Mult``. The identifier that starts the name of a library is called a *library root*. All library files of the standard library of |Coq| have the reserved root |Coq| but library file names based on other roots can be obtained by using |Coq| commands -(coqc, coqtop, coqdep, …) options ``-Q`` or ``-R`` (see :ref:`TODO-14.3.3-command-line-options`). +(coqc, coqtop, coqdep, …) options ``-Q`` or ``-R`` (see :ref:`command-line-options`). Also, when an interactive |Coq| session starts, a library of root ``Top`` is -started, unless option ``-top`` or ``-notop`` is set (see :ref:`TODO-14.3.3-command-line-options`). +started, unless option ``-top`` or ``-notop`` is set (see :ref:`command-line-options`). +.. _qualified-names: Qualified names ~~~~~~~~~~~~~~~ @@ -1339,13 +1298,13 @@ names also applies to library file names. |Coq| maintains a table called the name table which maps partially qualified names of constructions to absolute names. This table is updated by the -commands ``Require`` (see :ref:`TODO-6.5.1-Require`), Import and Export (see :ref:`import_qualid`) and +commands :cmd:`Require`, :cmd:`Import` and :cmd:`Export` and also each time a new declaration is added to the context. An absolute name is called visible from a given short or partially qualified name when this latter name is enough to denote it. This means that the short or partially qualified name is mapped to the absolute name in |Coq| name table. Definitions flagged as Local are only accessible with -their fully qualified name (see :ref:`TODO-1.3.2-definitions`). +their fully qualified name (see :ref:`gallina-definitions`). It may happen that a visible name is hidden by the short name or a qualified name of another construction. In this case, the name that @@ -1367,16 +1326,15 @@ accessible, absolute names can never be hidden. Locate nat. -See also: Command Locate in :ref:`TODO-6.3.10-locate-qualid` and Locate Library in -:ref:`TODO-6.6.11-locate-library`. +See also: Commands :cmd:`Locate` and :cmd:`Locate Library`. +.. _libraries-and-filesystem: Libraries and filesystem ~~~~~~~~~~~~~~~~~~~~~~~~ -Please note that the questions described here have been subject to -redesign in |Coq| v8.5. Former versions of |Coq| use the same terminology -to describe slightly different things. +.. note:: The questions described here have been subject to redesign in |Coq| 8.5. + Former versions of |Coq| use the same terminology to describe slightly different things. Compiled files (``.vo`` and ``.vio``) store sub-libraries. In order to refer to them inside |Coq|, a translation from file-system names to |Coq| names @@ -1412,7 +1370,7 @@ translation and with an empty logical prefix. The command line option ``-R`` is a variant of ``-Q`` which has the strictly same behavior regarding loadpaths, but which also makes the corresponding ``.vo`` files available through their short names in a way -not unlike the ``Import`` command (see :ref:`import_qualid`). For instance, ``-R`` `path` ``Lib`` +not unlike the ``Import`` command (see :ref:`here <import_qualid>`). For instance, ``-R`` `path` ``Lib`` associates to the ``filepath/fOO/Bar/File.vo`` the logical name ``Lib.fOO.Bar.File``, but allows this file to be accessed through the short names ``fOO.Bar.File,Bar.File`` and ``File``. If several files with @@ -1420,7 +1378,7 @@ identical base name are present in different subdirectories of a recursive loadpath, which of these files is found first may be system- dependent and explicit qualification is recommended. The ``From`` argument of the ``Require`` command can be used to bypass the implicit shortening -by providing an absolute root to the required file (see :ref:`TODO-6.5.1-require-qualid`). +by providing an absolute root to the required file (see :ref:`compiled-files`). There also exists another independent loadpath mechanism attached to OCaml object files (``.cmo`` or ``.cmxs``) rather than |Coq| object @@ -1428,11 +1386,12 @@ files as described above. The OCaml loadpath is managed using the option ``-I`` `path` (in the OCaml world, there is neither a notion of logical name prefix nor a way to access files in subdirectories of path). See the command ``Declare`` ``ML`` ``Module`` in -:ref:`TODO-6.5-compiled-files` to understand the need of the OCaml loadpath. +:ref:`compiled-files` to understand the need of the OCaml loadpath. -See :ref:`TODO-14.3.3-command-line-options` for a more general view over the |Coq| command +See :ref:`command-line-options` for a more general view over the |Coq| command line options. +.. _ImplicitArguments: Implicit arguments ------------------ @@ -1548,10 +1507,10 @@ inserted. In the second case, the function is considered to be implicitly applied to the implicit arguments it is waiting for: one says that the implicit argument is maximally inserted. -Each implicit argument can be declared to have to be inserted -maximally or non maximally. This can be governed argument per argument -by the command ``Implicit Arguments`` (see Section :ref:`declare-implicit-args`) or globally by the -command ``Set Maximal Implicit Insertion`` (see Section :ref:`controlling-insertion-implicit-args`). +Each implicit argument can be declared to have to be inserted maximally or non +maximally. This can be governed argument per argument by the command ``Implicit +Arguments`` (see Section :ref:`declare-implicit-args`) or globally by the +:opt:`Maximal Implicit Insertion` option. See also :ref:`displaying-implicit-args`. @@ -1627,6 +1586,7 @@ Declaring Implicit Arguments To set implicit arguments *a posteriori*, one can use the command: .. cmd:: Arguments @qualid {* @possibly_bracketed_ident }. + :name: Arguments (implicits) where the list of `possibly_bracketed_ident` is a prefix of the list of arguments of `qualid` where the ones to be declared implicit are @@ -1780,14 +1740,10 @@ appear strictly in the body of the type, they are implicit. Mode for automatic declaration of implicit arguments ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -In case one wants to systematically declare implicit the arguments -detectable as such, one may switch to the automatic declaration of -implicit arguments mode by using the command: - -.. cmd:: Set Implicit Arguments. +.. opt:: Implicit Arguments. -Conversely, one may unset the mode by using ``Unset Implicit Arguments``. -The mode is off by default. Auto-detection of implicit arguments is +This option (off by default) allows to systematically declare implicit +the arguments detectable as such. Auto-detection of implicit arguments is governed by options controlling whether strict and contextual implicit arguments have to be considered or not. @@ -1796,76 +1752,55 @@ arguments have to be considered or not. Controlling strict implicit arguments ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +.. opt:: Strict Implicit. + When the mode for automatic declaration of implicit arguments is on, the default is to automatically set implicit only the strict implicit arguments plus, for historical reasons, a small subset of the non-strict implicit arguments. To relax this constraint and to set -implicit all non strict implicit arguments by default, use the command: - -.. cmd:: Unset Strict Implicit. +implicit all non strict implicit arguments by default, you can turn this +option off. -Conversely, use the command ``Set Strict Implicit`` to restore the -original mode that declares implicit only the strict implicit -arguments plus a small subset of the non strict implicit arguments. +.. opt:: Strongly Strict Implicit. -In the other way round, to capture exactly the strict implicit -arguments and no more than the strict implicit arguments, use the -command - -.. cmd:: Set Strongly Strict Implicit. - -Conversely, use the command ``Unset Strongly Strict Implicit`` to let the -option “Strict Implicit” decide what to do. - -Remark: In versions of |Coq| prior to version 8.0, the default was to -declare the strict implicit arguments as implicit. +Use this option (off by default) to capture exactly the strict implicit +arguments and no more than the strict implicit arguments. .. _controlling-contextual-implicit-args: Controlling contextual implicit arguments ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -By default, |Coq| does not automatically set implicit the contextual -implicit arguments. To tell |Coq| to infer also contextual implicit -argument, use command - -.. cmd:: Set Contextual Implicit. +.. opt:: Contextual Implicit. -Conversely, use command ``Unset Contextual Implicit`` to unset the -contextual implicit mode. +By default, |Coq| does not automatically set implicit the contextual +implicit arguments. You can turn this option on to tell |Coq| to also +infer contextual implicit argument. .. _controlling-rev-pattern-implicit-args: Controlling reversible-pattern implicit arguments ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -By default, |Coq| does not automatically set implicit the reversible-pattern -implicit arguments. To tell |Coq| to infer also reversible- -pattern implicit argument, use command - -.. cmd:: Set Reversible Pattern Implicit. +.. opt:: Reversible Pattern Implicit. -Conversely, use command ``Unset Reversible Pattern Implicit`` to unset the -reversible-pattern implicit mode. +By default, |Coq| does not automatically set implicit the reversible-pattern +implicit arguments. You can turn this option on to tell |Coq| to also infer +reversible-pattern implicit argument. .. _controlling-insertion-implicit-args: Controlling the insertion of implicit arguments not followed by explicit arguments ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Implicit arguments can be declared to be automatically inserted when a -function is partially applied and the next argument of the function is -an implicit one. In case the implicit arguments are automatically -declared (with the command ``Set Implicit Arguments``), the command - -.. cmd:: Set Maximal Implicit Insertion. +.. opt:: Maximal Implicit Insertion. -is used to tell to declare the implicit arguments with a maximal -insertion status. By default, automatically declared implicit -arguments are not declared to be insertable maximally. To restore the -default mode for maximal insertion, use the command +Assuming the implicit argument mode is on, this option (off by default) +declares implicit arguments to be automatically inserted when a +function is partially applied and the next argument of the function is +an implicit one. -.. cmd:: Unset Maximal Implicit Insertion. +.. _explicit-applications: Explicit applications ~~~~~~~~~~~~~~~~~~~~~ @@ -1935,28 +1870,20 @@ if each of them is to be used maximally or not, use the command Explicit displaying of implicit arguments for pretty-printing ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -By default the basic pretty-printing rules hide the inferable implicit -arguments of an application. To force printing all implicit arguments, -use command +.. opt:: Printing Implicit. -.. cmd:: Set Printing Implicit. - -Conversely, to restore the hiding of implicit arguments, use command +By default, the basic pretty-printing rules hide the inferable implicit +arguments of an application. Turn this option on to force printing all +implicit arguments. -.. cmd:: Unset Printing Implicit. +.. opt:: Printing Implicit Defensive. -By default the basic pretty-printing rules display the implicit +By default, the basic pretty-printing rules display the implicit arguments that are not detected as strict implicit arguments. This “defensive” mode can quickly make the display cumbersome so this can -be deactivated by using the command +be deactivated by turning this option off. -.. cmd:: Unset Printing Implicit Defensive. - -Conversely, to force the display of non strict arguments, use command - -.. cmd:: Set Printing Implicit Defensive. - -See also: ``Set Printing All`` in :ref:`printing_constructions_full`. +See also: :opt:`Printing All`. Interaction with subtyping ~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -1981,17 +1908,14 @@ but succeeds in Deactivation of implicit arguments for parsing ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Use of implicit arguments can be deactivated by issuing the command: +.. opt:: Parsing Explicit. -.. cmd:: Set Parsing Explicit. +Turning this option on, deactivates the use of implicit arguments. In this case, all arguments of constants, inductive types, constructors, etc, including the arguments declared as implicit, have -to be given as if none arguments were implicit. By symmetry, this also -affects printing. To restore parsing and normal printing of implicit -arguments, use: - -.. cmd:: Unset Parsing Explicit. +to be given as if no arguments were implicit. By symmetry, this also +affects printing. Canonical structures ~~~~~~~~~~~~~~~~~~~~ @@ -2109,6 +2033,8 @@ case, this latter type is considered). Adds blocks of implicit types with different specifications. +.. _implicit-generalization: + Implicit generalization ~~~~~~~~~~~~~~~~~~~~~~~ @@ -2175,6 +2101,7 @@ implicitly, as maximally-inserted arguments. In these binders, the binding name for the bound object is optional, whereas the type is mandatory, dually to regular binders. +.. _Coercions: Coercions --------- @@ -2189,12 +2116,7 @@ an inductive type or any constant with a type of the form Then the user is able to apply an object that is not a function, but can be coerced to a function, and more generally to consider that a term of type ``A`` is of type ``B`` provided that there is a declared coercion -between ``A`` and ``B``. The main command is - -.. cmd:: Coercion @qualid : @class >-> @class. - -which declares the construction denoted by qualid as a coercion -between the two given classes. +between ``A`` and ``B``. More details and examples, and a description of the commands related to coercions are provided in :ref:`implicitcoercions`. @@ -2204,43 +2126,38 @@ to coercions are provided in :ref:`implicitcoercions`. Printing constructions in full ------------------------------ +.. opt:: Printing All. + Coercions, implicit arguments, the type of pattern-matching, but also notations (see :ref:`syntaxextensionsandinterpretationscopes`) can obfuscate the behavior of some tactics (typically the tactics applying to occurrences of subterms are -sensitive to the implicit arguments). The command - -.. cmd:: Set Printing All. - +sensitive to the implicit arguments). Turning this option on deactivates all high-level printing features such as coercions, implicit arguments, returned type of pattern-matching, notations and various syntactic sugar for pattern-matching or record projections. -Otherwise said, ``Set Printing All`` includes the effects of the commands -``Set Printing Implicit``, ``Set Printing Coercions``, ``Set Printing Synth``, -``Unset Printing Projections``, and ``Unset Printing Notations``. To reactivate -the high-level printing features, use the command +Otherwise said, :opt:`Printing All` includes the effects of the options +:opt:`Printing Implicit`, :opt:`Printing Coercions`, :opt:`Printing Synth`, +:opt:`Printing Projections`, and :opt:`Printing Notations`. To reactivate +the high-level printing features, use the command ``Unset Printing All``. -.. cmd:: Unset Printing All. +.. _printing-universes: Printing universes ------------------ -The following command: +.. opt:: Printing Universes. -.. cmd:: Set Printing Universes. - -activates the display of the actual level of each occurrence of ``Type``. -See :ref:`TODO-4.1.1-sorts` for details. This wizard option, in combination -with ``Set Printing All`` (see :ref:`printing_constructions_full`) can help to diagnose failures -to unify terms apparently identical but internally different in the -Calculus of Inductive Constructions. To reactivate the display of the -actual level of the occurrences of Type, use - -.. cmd:: Unset Printing Universes. +Turn this option on to activate the display of the actual level of each +occurrence of :g:`Type`. See :ref:`Sorts` for details. This wizard option, in +combination with :opt:`Printing All` can help to diagnose failures to unify +terms apparently identical but internally different in the Calculus of Inductive +Constructions. The constraints on the internal level of the occurrences of Type -(see :ref:`TODO-4.1.1-sorts`) can be printed using the command +(see :ref:`Sorts`) can be printed using the command .. cmd:: Print {? Sorted} Universes. + :name: Print Universes If the optional ``Sorted`` option is given, each universe will be made equivalent to a numbered label reflecting its level (with a linear @@ -2248,12 +2165,13 @@ ordering) in the universe hierarchy. This command also accepts an optional output filename: -.. cmd:: Print {? Sorted} Universes @string. +.. cmdv:: Print {? Sorted} Universes @string. If `string` ends in ``.dot`` or ``.gv``, the constraints are printed in the DOT language, and can be processed by Graphviz tools. The format is unspecified if `string` doesn’t end in ``.dot`` or ``.gv``. +.. _existential-variables: Existential variables --------------------- @@ -2263,9 +2181,9 @@ subterms to eventually be replaced by actual subterms. Existential variables are generated in place of unsolvable implicit arguments or “_” placeholders when using commands such as ``Check`` (see -Section :ref:`TODO-6.3.1-check`) or when using tactics such as ``refine`` (see Section -:ref:`TODO-8.2.3-refine`), as well as in place of unsolvable instances when using -tactics such that ``eapply`` (see Section :ref:`TODO-8.2.4-apply`). An existential +Section :ref:`requests-to-the-environment`) or when using tactics such as +:tacn:`refine`, as well as in place of unsolvable instances when using +tactics such that :tacn:`eapply`. An existential variable is defined in a context, which is the context of variables of the placeholder which generated the existential variable, and a type, which is the expected type of the placeholder. @@ -2310,25 +2228,19 @@ existential variable used in the same context as its context of definition is wr Existential variables can be named by the user upon creation using the syntax ``?``\ `ident`. This is useful when the existential variable needs to be explicitly handled later in the script (e.g. -with a named-goal selector, see :ref:`TODO-9.2-goal-selectors`). +with a named-goal selector, see :ref:`goal-selectors`). .. _explicit-display-existentials: Explicit displaying of existential instances for pretty-printing ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -The command: - -.. cmd:: Set Printing Existential Instances. - -activates the full display of how the context of an existential -variable is instantiated at each of the occurrences of the existential -variable. +.. opt:: Printing Existential Instances. -To deactivate the full display of the instances of existential -variables, use +This option (off by default) activates the full display of how the +context of an existential variable is instantiated at each of the +occurrences of the existential variable. -.. cmd:: Unset Printing Existential Instances. Solving existential variables using tactics ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -2341,7 +2253,7 @@ is not specified and is implementation-dependent. The inner tactic may use any variable defined in its scope, including repeated alternations between variables introduced by term binding as well as those introduced by tactic binding. The expression `tacexpr` can be any tactic -expression as described in :ref:`thetacticlanguage`. +expression as described in :ref:`ltac`. .. coqtop:: all @@ -2352,5 +2264,5 @@ using highly automated tactics without resorting to writing the proof-term by means of the interactive proof engine. This mechanism is comparable to the ``Declare Implicit Tactic`` command -defined at :ref:`TODO-8.9.7-implicit-automation`, except that the used +defined at :ref:`tactics-implicit-automation`, except that the used tactic is local to each hole instead of being declared globally. diff --git a/doc/sphinx/language/gallina-specification-language.rst b/doc/sphinx/language/gallina-specification-language.rst new file mode 100644 index 0000000000..a9c4dd7588 --- /dev/null +++ b/doc/sphinx/language/gallina-specification-language.rst @@ -0,0 +1,1376 @@ +.. _gallinaspecificationlanguage: + +------------------------------------ + The Gallina specification language +------------------------------------ + +This chapter describes Gallina, the specification language of Coq. It allows +developing mathematical theories and to prove specifications of programs. The +theories are built from axioms, hypotheses, parameters, lemmas, theorems and +definitions of constants, functions, predicates and sets. The syntax of logical +objects involved in theories is described in Section :ref:`term`. The +language of commands, called *The Vernacular* is described in Section +:ref:`vernacular`. + +In Coq, logical objects are typed to ensure their logical correctness. The +rules implemented by the typing algorithm are described in Chapter :ref:`calculusofinductiveconstructions`. + + +About the grammars in the manual +================================ + +Grammars are presented in Backus-Naur form (BNF). Terminal symbols are +set in black ``typewriter font``. In addition, there are special notations for +regular expressions. + +An expression enclosed in square brackets ``[…]`` means at most one +occurrence of this expression (this corresponds to an optional +component). + +The notation “``entry sep … sep entry``” stands for a non empty sequence +of expressions parsed by entry and separated by the literal “``sep``” [1]_. + +Similarly, the notation “``entry … entry``” stands for a non empty +sequence of expressions parsed by the “``entry``” entry, without any +separator between. + +At the end, the notation “``[entry sep … sep entry]``” stands for a +possibly empty sequence of expressions parsed by the “``entry``” entry, +separated by the literal “``sep``”. + + +Lexical conventions +=================== + +Blanks + Space, newline and horizontal tabulation are considered as blanks. + Blanks are ignored but they separate tokens. + +Comments + Comments in Coq are enclosed between ``(*`` and ``*)``, and can be nested. + They can contain any character. However, string literals must be + correctly closed. Comments are treated as blanks. + +Identifiers and access identifiers + Identifiers, written ident, are sequences of letters, digits, ``_`` and + ``'``, that do not start with a digit or ``'``. That is, they are + recognized by the following lexical class: + + .. productionlist:: coq + first_letter : a..z ∣ A..Z ∣ _ ∣ unicode-letter + subsequent_letter : a..z ∣ A..Z ∣ 0..9 ∣ _ ∣ ' ∣ unicode-letter ∣ unicode-id-part + ident : `first_letter` [`subsequent_letter` … `subsequent_letter`] + access_ident : . `ident` + + All characters are meaningful. In particular, identifiers are case- + sensitive. The entry ``unicode-letter`` non-exhaustively includes Latin, + Greek, Gothic, Cyrillic, Arabic, Hebrew, Georgian, Hangul, Hiragana + and Katakana characters, CJK ideographs, mathematical letter-like + symbols, hyphens, non-breaking space, … The entry ``unicode-id-part`` non- + exhaustively includes symbols for prime letters and subscripts. + + Access identifiers, written :token:`access_ident`, are identifiers prefixed by + `.` (dot) without blank. They are used in the syntax of qualified + identifiers. + +Natural numbers and integers + Numerals are sequences of digits. Integers are numerals optionally + preceded by a minus sign. + + .. productionlist:: coq + digit : 0..9 + num : `digit` … `digit` + integer : [-] `num` + +Strings + Strings are delimited by ``"`` (double quote), and enclose a sequence of + any characters different from ``"`` or the sequence ``""`` to denote the + double quote character. In grammars, the entry for quoted strings is + :production:`string`. + +Keywords + The following identifiers are reserved keywords, and cannot be + employed otherwise:: + + _ as at cofix else end exists exists2 fix for + forall fun if IF in let match mod Prop return + Set then Type using where with + +Special tokens + The following sequences of characters are special tokens:: + + ! % & && ( () ) * + ++ , - -> . .( .. + / /\ : :: :< := :> ; < <- <-> <: <= <> = + => =_D > >-> >= ? ?= @ [ \/ ] ^ { | |- + || } ~ + + Lexical ambiguities are resolved according to the “longest match” + rule: when a sequence of non alphanumerical characters can be + decomposed into several different ways, then the first token is the + longest possible one (among all tokens defined at this moment), and so + on. + +.. _term: + +Terms +===== + +Syntax of terms +--------------- + +The following grammars describe the basic syntax of the terms of the +*Calculus of Inductive Constructions* (also called Cic). The formal +presentation of Cic is given in Chapter :ref:`calculusofinductiveconstructions`. Extensions of this syntax +are given in Chapter :ref:`extensionsofgallina`. How to customize the syntax +is described in Chapter :ref:`syntaxextensionsandinterpretationscopes`. + +.. productionlist:: coq + term : forall `binders` , `term` + : | fun `binders` => `term` + : | fix `fix_bodies` + : | cofix `cofix_bodies` + : | let `ident` [`binders`] [: `term`] := `term` in `term` + : | let fix `fix_body` in `term` + : | let cofix `cofix_body` in `term` + : | let ( [`name` , … , `name`] ) [`dep_ret_type`] := `term` in `term` + : | let ' `pattern` [in `term`] := `term` [`return_type`] in `term` + : | if `term` [`dep_ret_type`] then `term` else `term` + : | `term` : `term` + : | `term` <: `term` + : | `term` :> + : | `term` -> `term` + : | `term` arg … arg + : | @ `qualid` [`term` … `term`] + : | `term` % `ident` + : | match `match_item` , … , `match_item` [`return_type`] with + : [[|] `equation` | … | `equation`] end + : | `qualid` + : | `sort` + : | num + : | _ + : | ( `term` ) + arg : `term` + : | ( `ident` := `term` ) + binders : `binder` … `binder` + binder : `name` + : | ( `name` … `name` : `term` ) + : | ( `name` [: `term`] := `term` ) + name : `ident` | _ + qualid : `ident` | `qualid` `access_ident` + sort : Prop | Set | Type + fix_bodies : `fix_body` + : | `fix_body` with `fix_body` with … with `fix_body` for `ident` + cofix_bodies : `cofix_body` + : | `cofix_body` with `cofix_body` with … with `cofix_body` for `ident` + fix_body : `ident` `binders` [annotation] [: `term`] := `term` + cofix_body : `ident` [`binders`] [: `term`] := `term` + annotation : { struct `ident` } + match_item : `term` [as `name`] [in `qualid` [`pattern` … `pattern`]] + dep_ret_type : [as `name`] `return_type` + return_type : return `term` + equation : `mult_pattern` | … | `mult_pattern` => `term` + mult_pattern : `pattern` , … , `pattern` + pattern : `qualid` `pattern` … `pattern` + : | @ `qualid` `pattern` … `pattern` + : | `pattern` as `ident` + : | `pattern` % `ident` + : | `qualid` + : | _ + : | num + : | ( `or_pattern` , … , `or_pattern` ) + or_pattern : `pattern` | … | `pattern` + + +Types +----- + +Coq terms are typed. Coq types are recognized by the same syntactic +class as :token`term`. We denote by :token:`type` the semantic subclass +of types inside the syntactic class :token:`term`. + +.. _gallina-identifiers: + +Qualified identifiers and simple identifiers +-------------------------------------------- + +*Qualified identifiers* (:token:`qualid`) denote *global constants* +(definitions, lemmas, theorems, remarks or facts), *global variables* +(parameters or axioms), *inductive types* or *constructors of inductive +types*. *Simple identifiers* (or shortly :token:`ident`) are a syntactic subset +of qualified identifiers. Identifiers may also denote local *variables*, +what qualified identifiers do not. + +Numerals +-------- + +Numerals have no definite semantics in the calculus. They are mere +notations that can be bound to objects through the notation mechanism +(see Chapter :ref:`syntaxextensionsandinterpretationscopes` for details). +Initially, numerals are bound to Peano’s representation of natural +numbers (see :ref:`datatypes`). + +.. note:: + + negative integers are not at the same level as :token:`num`, for this + would make precedence unnatural. + +Sorts +----- + +There are three sorts :g:`Set`, :g:`Prop` and :g:`Type`. + +- :g:`Prop` is the universe of *logical propositions*. The logical propositions + themselves are typing the proofs. We denote propositions by *form*. + This constitutes a semantic subclass of the syntactic class :token:`term`. + +- :g:`Set` is is the universe of *program types* or *specifications*. The + specifications themselves are typing the programs. We denote + specifications by *specif*. This constitutes a semantic subclass of + the syntactic class :token:`term`. + +- :g:`Type` is the type of :g:`Prop` and :g:`Set` + +More on sorts can be found in Section :ref:`sorts`. + +.. _binders: + +Binders +------- + +Various constructions such as :g:`fun`, :g:`forall`, :g:`fix` and :g:`cofix` +*bind* variables. A binding is represented by an identifier. If the binding +variable is not used in the expression, the identifier can be replaced by the +symbol :g:`_`. When the type of a bound variable cannot be synthesized by the +system, it can be specified with the notation ``(ident : type)``. There is also +a notation for a sequence of binding variables sharing the same type: +``(``:token:`ident`:math:`_1`…:token:`ident`:math:`_n` : :token:`type```)``. A +binder can also be any pattern prefixed by a quote, e.g. :g:`'(x,y)`. + +Some constructions allow the binding of a variable to value. This is +called a “let-binder”. The entry :token:`binder` of the grammar accepts +either an assumption binder as defined above or a let-binder. The notation in +the latter case is ``(ident := term)``. In a let-binder, only one +variable can be introduced at the same time. It is also possible to give +the type of the variable as follows: +``(ident : term := term)``. + +Lists of :token:`binder` are allowed. In the case of :g:`fun` and :g:`forall`, +it is intended that at least one binder of the list is an assumption otherwise +fun and forall gets identical. Moreover, parentheses can be omitted in +the case of a single sequence of bindings sharing the same type (e.g.: +:g:`fun (x y z : A) => t` can be shortened in :g:`fun x y z : A => t`). + +Abstractions +------------ + +The expression ``fun ident : type => term`` defines the +*abstraction* of the variable :token:`ident`, of type :token:`type`, over the term +:token:`term`. It denotes a function of the variable :token:`ident` that evaluates to +the expression :token:`term` (e.g. :g:`fun x : A => x` denotes the identity +function on type :g:`A`). The keyword :g:`fun` can be followed by several +binders as given in Section :ref:`binders`. Functions over +several variables are equivalent to an iteration of one-variable +functions. For instance the expression +“fun :token:`ident`\ :math:`_{1}` … :token:`ident`\ :math:`_{n}` +: :token:`type` => :token:`term`” +denotes the same function as “ fun :token:`ident`\ +:math:`_{1}` : :token:`type` => … +fun :token:`ident`\ :math:`_{n}` : :token:`type` => :token:`term`”. If +a let-binder occurs in +the list of binders, it is expanded to a let-in definition (see +Section :ref:`let-in`). + +Products +-------- + +The expression :g:`forall ident : type, term` denotes the +*product* of the variable :token:`ident` of type :token:`type`, over the term :token:`term`. +As for abstractions, :g:`forall` is followed by a binder list, and products +over several variables are equivalent to an iteration of one-variable +products. Note that :token:`term` is intended to be a type. + +If the variable :token:`ident` occurs in :token:`term`, the product is called +*dependent product*. The intention behind a dependent product +:g:`forall x : A, B` is twofold. It denotes either +the universal quantification of the variable :g:`x` of type :g:`A` +in the proposition :g:`B` or the functional dependent product from +:g:`A` to :g:`B` (a construction usually written +:math:`\Pi_{x:A}.B` in set theory). + +Non dependent product types have a special notation: :g:`A -> B` stands for +:g:`forall _ : A, B`. The *non dependent product* is used both to denote +the propositional implication and function types. + +Applications +------------ + +The expression :token:`term`\ :math:`_0` :token:`term`\ :math:`_1` denotes the +application of :token:`term`\ :math:`_0` to :token:`term`\ :math:`_1`. + +The expression :token:`term`\ :math:`_0` :token:`term`\ :math:`_1` ... +:token:`term`\ :math:`_n` denotes the application of the term +:token:`term`\ :math:`_0` to the arguments :token:`term`\ :math:`_1` ... then +:token:`term`\ :math:`_n`. It is equivalent to ( … ( :token:`term`\ :math:`_0` +:token:`term`\ :math:`_1` ) … ) :token:`term`\ :math:`_n` : associativity is to the +left. + +The notation ``(ident := term)`` for arguments is used for making +explicit the value of implicit arguments (see +Section :ref:`explicit-applications`). + +Type cast +--------- + +The expression ``term : type`` is a type cast expression. It enforces +the type of :token:`term` to be :token:`type`. + +``term <: type`` locally sets up the virtual machine for checking that +:token:`term` has type :token:`type`. + +Inferable subterms +------------------ + +Expressions often contain redundant pieces of information. Subterms that can be +automatically inferred by Coq can be replaced by the symbol ``_`` and Coq will +guess the missing piece of information. + +.. _let-in: + +Let-in definitions +------------------ + +``let`` :token:`ident` := :token:`term`:math:`_1` in :token:`term`:math:`_2` +denotes the local binding of :token:`term`:math:`_1` to the variable +:token:`ident` in :token:`term`:math:`_2`. There is a syntactic sugar for let-in +definition of functions: ``let`` :token:`ident` :token:`binder`:math:`_1` … +:token:`binder`:math:`_n` := :token:`term`:math:`_1` in :token:`term`:math:`_2` +stands for ``let`` :token:`ident` := ``fun`` :token:`binder`:math:`_1` … +:token:`binder`:math:`_n` => :token:`term`:math:`_1` in :token:`term`:math:`_2`. + +Definition by case analysis +--------------------------- + +Objects of inductive types can be destructurated by a case-analysis +construction called *pattern-matching* expression. A pattern-matching +expression is used to analyze the structure of an inductive objects and +to apply specific treatments accordingly. + +This paragraph describes the basic form of pattern-matching. See +Section :ref:`Mult-match` and Chapter :ref:`extendedpatternmatching` for the description +of the general form. The basic form of pattern-matching is characterized +by a single :token:`match_item` expression, a :token:`mult_pattern` restricted to a +single :token:`pattern` and :token:`pattern` restricted to the form +:token:`qualid` :token:`ident`. + +The expression match :token:`term`:math:`_0` :token:`return_type` with +:token:`pattern`:math:`_1` => :token:`term`:math:`_1` :math:`|` … :math:`|` +:token:`pattern`:math:`_n` => :token:`term`:math:`_n` end, denotes a +:token:`pattern-matching` over the term :token:`term`:math:`_0` (expected to be +of an inductive type :math:`I`). The terms :token:`term`:math:`_1`\ …\ +:token:`term`:math:`_n` are the :token:`branches` of the pattern-matching +expression. Each of :token:`pattern`:math:`_i` has a form :token:`qualid` +:token:`ident` where :token:`qualid` must denote a constructor. There should be +exactly one branch for every constructor of :math:`I`. + +The :token:`return_type` expresses the type returned by the whole match +expression. There are several cases. In the *non dependent* case, all +branches have the same type, and the :token:`return_type` is the common type of +branches. In this case, :token:`return_type` can usually be omitted as it can be +inferred from the type of the branches [2]_. + +In the *dependent* case, there are three subcases. In the first subcase, +the type in each branch may depend on the exact value being matched in +the branch. In this case, the whole pattern-matching itself depends on +the term being matched. This dependency of the term being matched in the +return type is expressed with an “as :token:`ident`” clause where :token:`ident` +is dependent in the return type. For instance, in the following example: + +.. coqtop:: in + + Inductive bool : Type := true : bool | false : bool. + Inductive eq (A:Type) (x:A) : A -> Prop := eq_refl : eq A x x. + Inductive or (A:Prop) (B:Prop) : Prop := + | or_introl : A -> or A B + | or_intror : B -> or A B. + + Definition bool_case (b:bool) : or (eq bool b true) (eq bool b false) := + match b as x return or (eq bool x true) (eq bool x false) with + | true => or_introl (eq bool true true) (eq bool true false) + (eq_refl bool true) + | false => or_intror (eq bool false true) (eq bool false false) + (eq_refl bool false) + end. + +the branches have respective types or :g:`eq bool true true :g:`eq bool true +false` and or :g:`eq bool false true` :g:`eq bool false false` while the whole +pattern-matching expression has type or :g:`eq bool b true` :g:`eq bool b +false`, the identifier :g:`x` being used to represent the dependency. Remark +that when the term being matched is a variable, the as clause can be +omitted and the term being matched can serve itself as binding name in +the return type. For instance, the following alternative definition is +accepted and has the same meaning as the previous one. + +.. coqtop:: in + + Definition bool_case (b:bool) : or (eq bool b true) (eq bool b false) := + match b return or (eq bool b true) (eq bool b false) with + | true => or_introl (eq bool true true) (eq bool true false) + (eq_refl bool true) + | false => or_intror (eq bool false true) (eq bool false false) + (eq_refl bool false) + end. + +The second subcase is only relevant for annotated inductive types such +as the equality predicate (see Section :ref:`Equality`), +the order predicate on natural numbers or the type of lists of a given +length (see Section :ref:`matching-dependent`). In this configuration, the +type of each branch can depend on the type dependencies specific to the +branch and the whole pattern-matching expression has a type determined +by the specific dependencies in the type of the term being matched. This +dependency of the return type in the annotations of the inductive type +is expressed using a “in I _ ... _ :token:`pattern`:math:`_1` ... +:token:`pattern`:math:`_n`” clause, where + +- :math:`I` is the inductive type of the term being matched; + +- the :g:`_` are matching the parameters of the inductive type: the + return type is not dependent on them. + +- the :token:`pattern`:math:`_i` are matching the annotations of the + inductive type: the return type is dependent on them + +- in the basic case which we describe below, each :token:`pattern`:math:`_i` + is a name :token:`ident`:math:`_i`; see :ref:`match-in-patterns` for the + general case + +For instance, in the following example: + +.. coqtop:: in + + Definition eq_sym (A:Type) (x y:A) (H:eq A x y) : eq A y x := + match H in eq _ _ z return eq A z x with + | eq_refl _ => eq_refl A x + end. + +the type of the branch has type :g:`eq A x x` because the third argument of +g:`eq` is g:`x` in the type of the pattern :g:`refl_equal`. On the contrary, the +type of the whole pattern-matching expression has type :g:`eq A y x` because the +third argument of eq is y in the type of H. This dependency of the case analysis +in the third argument of :g:`eq` is expressed by the identifier g:`z` in the +return type. + +Finally, the third subcase is a combination of the first and second +subcase. In particular, it only applies to pattern-matching on terms in +a type with annotations. For this third subcase, both the clauses as and +in are available. + +There are specific notations for case analysis on types with one or two +constructors: “if … then … else …” and “let (…, ” (see +Sections :ref:`if-then-else` and :ref:`let-in`). + +Recursive functions +------------------- + +The expression “fix :token:`ident`:math:`_1` :token:`binder`:math:`_1` : +:token:`type`:math:`_1` ``:=`` :token:`term`:math:`_1` with … with +:token:`ident`:math:`_n` :token:`binder`:math:`_n` : :token:`type`:math:`_n` +``:=`` :token:`term`:math:`_n` for :token:`ident`:math:`_i`” denotes the +:math:`i`\ component of a block of functions defined by mutual well-founded +recursion. It is the local counterpart of the :cmd:`Fixpoint` command. When +:math:`n=1`, the “for :token:`ident`:math:`_i`” clause is omitted. + +The expression “cofix :token:`ident`:math:`_1` :token:`binder`:math:`_1` : +:token:`type`:math:`_1` with … with :token:`ident`:math:`_n` :token:`binder`:math:`_n` +: :token:`type`:math:`_n` for :token:`ident`:math:`_i`” denotes the +:math:`i`\ component of a block of terms defined by a mutual guarded +co-recursion. It is the local counterpart of the ``CoFixpoint`` command. See +Section :ref:`CoFixpoint` for more details. When +:math:`n=1`, the “ for :token:`ident`:math:`_i`” clause is omitted. + +The association of a single fixpoint and a local definition have a special +syntax: “let fix f … := … in …” stands for “let f := fix f … := … in …”. The +same applies for co-fixpoints. + +.. _vernacular: + +The Vernacular +============== + +.. productionlist:: coq + sentence : `assumption` + : | `definition` + : | `inductive` + : | `fixpoint` + : | `assertion` `proof` + assumption : `assumption_keyword` `assums`. + assumption_keyword : Axiom | Conjecture + : | Parameter | Parameters + : | Variable | Variables + : | Hypothesis | Hypotheses + assums : `ident` … `ident` : `term` + : | ( `ident` … `ident` : `term` ) … ( `ident` … `ident` : `term` ) + definition : [Local] Definition `ident` [`binders`] [: `term`] := `term` . + : | Let `ident` [`binders`] [: `term`] := `term` . + inductive : Inductive `ind_body` with … with `ind_body` . + : | CoInductive `ind_body` with … with `ind_body` . + ind_body : `ident` [`binders`] : `term` := + : [[|] `ident` [`binders`] [:`term`] | … | `ident` [`binders`] [:`term`]] + fixpoint : Fixpoint `fix_body` with … with `fix_body` . + : | CoFixpoint `cofix_body` with … with `cofix_body` . + assertion : `assertion_keyword` `ident` [`binders`] : `term` . + assertion_keyword : Theorem | Lemma + : | Remark | Fact + : | Corollary | Proposition + : | Definition | Example + proof : Proof . … Qed . + : | Proof . … Defined . + : | Proof . … Admitted . + +.. todo:: This use of … in this grammar is inconsistent + +This grammar describes *The Vernacular* which is the language of +commands of Gallina. A sentence of the vernacular language, like in +many natural languages, begins with a capital letter and ends with a +dot. + +The different kinds of command are described hereafter. They all suppose +that the terms occurring in the sentences are well-typed. + +.. _gallina-assumptions: + +Assumptions +----------- + +Assumptions extend the environment with axioms, parameters, hypotheses +or variables. An assumption binds an :token:`ident` to a :token:`type`. It is accepted +by Coq if and only if this :token:`type` is a correct type in the environment +preexisting the declaration and if :token:`ident` was not previously defined in +the same module. This :token:`type` is considered to be the type (or +specification, or statement) assumed by :token:`ident` and we say that :token:`ident` +has type :token:`type`. + +.. _Axiom: + +.. cmd:: Axiom @ident : @term. + + This command links *term* to the name *ident* as its specification in + the global context. The fact asserted by *term* is thus assumed as a + postulate. + +.. exn:: @ident already exists (Axiom) + +.. cmdv:: Parameter @ident : @term. + :name: Parameter + + Is equivalent to ``Axiom`` :token:`ident` : :token:`term` + +.. cmdv:: Parameter {+ @ident } : @term. + + Adds parameters with specification :token:`term` + +.. cmdv:: Parameter {+ ( {+ @ident } : @term ) }. + + Adds blocks of parameters with different specifications. + +.. cmdv:: Parameters {+ ( {+ @ident } : @term ) }. + + Synonym of ``Parameter``. + +.. cmdv:: Local Axiom @ident : @term. + + Such axioms are never made accessible through their unqualified name by + :cmd:`Import` and its variants. You have to explicitly give their fully + qualified name to refer to them. + +.. cmdv:: Conjecture @ident : @term + :name: Conjecture + + Is equivalent to ``Axiom`` :token:`ident` : :token:`term`. + +.. cmd:: Variable @ident : @term. + +This command links :token:`term` to the name :token:`ident` in the context of +the current section (see Section :ref:`section-mechanism` for a description of +the section mechanism). When the current section is closed, name :token:`ident` +will be unknown and every object using this variable will be explicitly +parametrized (the variable is *discharged*). Using the ``Variable`` command out +of any section is equivalent to using ``Local Parameter``. + +.. exn:: @ident already exists (Variable) + +.. cmdv:: Variable {+ @ident } : @term. + + Links :token:`term` to each :token:`ident`. + +.. cmdv:: Variable {+ ( {+ @ident } : @term) }. + + Adds blocks of variables with different specifications. + +.. cmdv:: Variables {+ ( {+ @ident } : @term) }. + +.. cmdv:: Hypothesis {+ ( {+ @ident } : @term) }. + :name: Hypothesis + +.. cmdv:: Hypotheses {+ ( {+ @ident } : @term) }. + +Synonyms of ``Variable``. + +It is advised to use the keywords ``Axiom`` and ``Hypothesis`` for +logical postulates (i.e. when the assertion *term* is of sort ``Prop``), +and to use the keywords ``Parameter`` and ``Variable`` in other cases +(corresponding to the declaration of an abstract mathematical entity). + +.. _gallina-definitions: + +Definitions +----------- + +Definitions extend the environment with associations of names to terms. +A definition can be seen as a way to give a meaning to a name or as a +way to abbreviate a term. In any case, the name can later be replaced at +any time by its definition. + +The operation of unfolding a name into its definition is called +:math:`\delta`-conversion (see Section :ref:`delta-reduction`). A +definition is accepted by the system if and only if the defined term is +well-typed in the current context of the definition and if the name is +not already used. The name defined by the definition is called a +*constant* and the term it refers to is its *body*. A definition has a +type which is the type of its body. + +A formal presentation of constants and environments is given in +Section :ref:`typing-rules`. + +.. cmd:: Definition @ident := @term. + + This command binds :token:`term` to the name :token:`ident` in the environment, + provided that :token:`term` is well-typed. + +.. exn:: @ident already exists (Definition) + +.. cmdv:: Definition @ident : @term := @term. + + It checks that the type of :token:`term`:math:`_2` is definitionally equal to + :token:`term`:math:`_1`, and registers :token:`ident` as being of type + :token:`term`:math:`_1`, and bound to value :token:`term`:math:`_2`. + + +.. cmdv:: Definition @ident {* @binder } : @term := @term. + + This is equivalent to ``Definition`` :token:`ident` : :g:`forall` + :token:`binder`:math:`_1` … :token:`binder`:math:`_n`, :token:`term`:math:`_1` := + fun :token:`binder`:math:`_1` … + :token:`binder`:math:`_n` => :token:`term`:math:`_2`. + +.. cmdv:: Local Definition @ident := @term. + + Such definitions are never made accessible through their + unqualified name by :cmd:`Import` and its variants. + You have to explicitly give their fully qualified name to refer to them. + +.. cmdv:: Example @ident := @term. + +.. cmdv:: Example @ident : @term := @term. + +.. cmdv:: Example @ident {* @binder } : @term := @term. + +These are synonyms of the Definition forms. + +.. exn:: The term @term has type @type while it is expected to have type @type + +See also :cmd:`Opaque`, :cmd:`Transparent`, :tac:`unfold`. + +.. cmd:: Let @ident := @term. + +This command binds the value :token:`term` to the name :token:`ident` in the +environment of the current section. The name :token:`ident` disappears when the +current section is eventually closed, and, all persistent objects (such +as theorems) defined within the section and depending on :token:`ident` are +prefixed by the let-in definition ``let`` :token:`ident` ``:=`` :token:`term` +``in``. Using the ``Let`` command out of any section is equivalent to using +``Local Definition``. + +.. exn:: @ident already exists (Let) + +.. cmdv:: Let @ident : @term := @term. + +.. cmdv:: Let Fixpoint @ident @fix_body {* with @fix_body}. + +.. cmdv:: Let CoFixpoint @ident @cofix_body {* with @cofix_body}. + +See also Sections :ref:`section-mechanism`, commands :cmd:`Opaque`, +:cmd:`Transparent`, and tactic :tacn:`unfold`. + +.. _gallina-inductive-definitions: + +Inductive definitions +--------------------- + +We gradually explain simple inductive types, simple annotated inductive +types, simple parametric inductive types, mutually inductive types. We +explain also co-inductive types. + +Simple inductive types +~~~~~~~~~~~~~~~~~~~~~~ + +The definition of a simple inductive type has the following form: + +.. cmd:: Inductive @ident : @sort := {? | } @ident : @type {* | @ident : @type } + +The name :token:`ident` is the name of the inductively defined type and +:token:`sort` is the universes where it lives. The :token:`ident` are the names +of its constructors and :token:`type` their respective types. The types of the +constructors have to satisfy a *positivity condition* (see Section +:ref:`positivity`) for :token:`ident`. This condition ensures the soundness of +the inductive definition. If this is the case, the :token:`ident` are added to +the environment with their respective types. Accordingly to the universe where +the inductive type lives (e.g. its type :token:`sort`), Coq provides a number of +destructors for :token:`ident`. Destructors are named ``ident_ind``, +``ident_rec`` or ``ident_rect`` which respectively correspond to +elimination principles on :g:`Prop`, :g:`Set` and :g:`Type`. The type of the +destructors expresses structural induction/recursion principles over objects of +:token:`ident`. We give below two examples of the use of the Inductive +definitions. + +The set of natural numbers is defined as: + +.. coqtop:: all + + Inductive nat : Set := + | O : nat + | S : nat -> nat. + +The type nat is defined as the least :g:`Set` containing :g:`O` and closed by +the :g:`S` constructor. The names :g:`nat`, :g:`O` and :g:`S` are added to the +environment. + +Now let us have a look at the elimination principles. They are three of them: +:g:`nat_ind`, :g:`nat_rec` and :g:`nat_rect`. The type of :g:`nat_ind` is: + +.. coqtop:: all + + Check nat_ind. + +This is the well known structural induction principle over natural +numbers, i.e. the second-order form of Peano’s induction principle. It +allows proving some universal property of natural numbers (:g:`forall +n:nat, P n`) by induction on :g:`n`. + +The types of :g:`nat_rec` and :g:`nat_rect` are similar, except that they pertain +to :g:`(P:nat->Set)` and :g:`(P:nat->Type)` respectively. They correspond to +primitive induction principles (allowing dependent types) respectively +over sorts ``Set`` and ``Type``. The constant ``ident_ind`` is always +provided, whereas ``ident_rec`` and ``ident_rect`` can be impossible +to derive (for example, when :token:`ident` is a proposition). + +.. coqtop:: in + + Inductive nat : Set := O | S (_:nat). + +In the case where inductive types have no annotations (next section +gives an example of such annotations), a constructor can be defined +by only giving the type of its arguments. + +Simple annotated inductive types +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In an annotated inductive types, the universe where the inductive type +is defined is no longer a simple sort, but what is called an arity, +which is a type whose conclusion is a sort. + +As an example of annotated inductive types, let us define the +:g:`even` predicate: + +.. coqtop:: all + + Inductive even : nat -> Prop := + | even_0 : even O + | even_SS : forall n:nat, even n -> even (S (S n)). + +The type :g:`nat->Prop` means that even is a unary predicate (inductively +defined) over natural numbers. The type of its two constructors are the +defining clauses of the predicate even. The type of :g:`even_ind` is: + +.. coqtop:: all + + Check even_ind. + +From a mathematical point of view it asserts that the natural numbers satisfying +the predicate even are exactly in the smallest set of naturals satisfying the +clauses :g:`even_0` or :g:`even_SS`. This is why, when we want to prove any +predicate :g:`P` over elements of :g:`even`, it is enough to prove it for :g:`O` +and to prove that if any natural number :g:`n` satisfies :g:`P` its double +successor :g:`(S (S n))` satisfies also :g:`P`. This is indeed analogous to the +structural induction principle we got for :g:`nat`. + +.. exn:: Non strictly positive occurrence of @ident in @type + +.. exn:: The conclusion of @type is not valid; it must be built from @ident + +Parametrized inductive types +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In the previous example, each constructor introduces a different +instance of the predicate even. In some cases, all the constructors +introduces the same generic instance of the inductive definition, in +which case, instead of an annotation, we use a context of parameters +which are binders shared by all the constructors of the definition. + +The general scheme is: + +.. cmdv:: Inductive @ident {+ @binder} : @term := {? | } @ident : @type {* | @ident : @type} + +Parameters differ from inductive type annotations in the fact that the +conclusion of each type of constructor :g:`term` invoke the inductive type with +the same values of parameters as its specification. + +A typical example is the definition of polymorphic lists: + +.. coqtop:: in + + Inductive list (A:Set) : Set := + | nil : list A + | cons : A -> list A -> list A. + +.. note:: + + In the type of :g:`nil` and :g:`cons`, we write :g:`(list A)` and not + just :g:`list`. The constructors :g:`nil` and :g:`cons` will have respectively + types: + + .. coqtop:: all + + Check nil. + Check cons. + + Types of destructors are also quantified with :g:`(A:Set)`. + +Variants +++++++++ + +.. coqtop:: in + + Inductive list (A:Set) : Set := nil | cons (_:A) (_:list A). + +This is an alternative definition of lists where we specify the +arguments of the constructors rather than their full type. + +.. coqtop:: in + + Variant sum (A B:Set) : Set := left : A -> sum A B | right : B -> sum A B. + +The ``Variant`` keyword is identical to the ``Inductive`` keyword, except +that it disallows recursive definition of types (in particular lists cannot +be defined with the Variant keyword). No induction scheme is generated for +this variant, unless :opt:`Nonrecursive Elimination Schemes` is set. + +.. exn:: The @num th argument of @ident must be @ident in @type + +New from Coq V8.1 ++++++++++++++++++ + +The condition on parameters for inductive definitions has been relaxed +since Coq V8.1. It is now possible in the type of a constructor, to +invoke recursively the inductive definition on an argument which is not +the parameter itself. + +One can define : + +.. coqtop:: all + + Inductive list2 (A:Set) : Set := + | nil2 : list2 A + | cons2 : A -> list2 (A*A) -> list2 A. + +that can also be written by specifying only the type of the arguments: + +.. coqtop:: all reset + + Inductive list2 (A:Set) : Set := nil2 | cons2 (_:A) (_:list2 (A*A)). + +But the following definition will give an error: + +.. coqtop:: all + + Fail Inductive listw (A:Set) : Set := + | nilw : listw (A*A) + | consw : A -> listw (A*A) -> listw (A*A). + +Because the conclusion of the type of constructors should be :g:`listw A` in +both cases. + +A parametrized inductive definition can be defined using annotations +instead of parameters but it will sometimes give a different (bigger) +sort for the inductive definition and will produce a less convenient +rule for case elimination. + +See also Section :ref:`inductive-definitions` and the :tacn:`induction` +tactic. + +Mutually defined inductive types +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The definition of a block of mutually inductive types has the form: + +.. cmdv:: Inductive @ident : @term := {? | } @ident : @type {* | @ident : @type } {* with @ident : @term := {? | } @ident : @type {* | @ident : @type }}. + +It has the same semantics as the above ``Inductive`` definition for each +:token:`ident` All :token:`ident` are simultaneously added to the environment. +Then well-typing of constructors can be checked. Each one of the :token:`ident` +can be used on its own. + +It is also possible to parametrize these inductive definitions. However, +parameters correspond to a local context in which the whole set of +inductive declarations is done. For this reason, the parameters must be +strictly the same for each inductive types The extended syntax is: + +.. cmdv:: Inductive @ident {+ @binder} : @term := {? | } @ident : @type {* | @ident : @type } {* with @ident {+ @binder} : @term := {? | } @ident : @type {* | @ident : @type }}. + +The typical example of a mutual inductive data type is the one for trees and +forests. We assume given two types :g:`A` and :g:`B` as variables. It can +be declared the following way. + +.. coqtop:: in + + Variables A B : Set. + + Inductive tree : Set := + node : A -> forest -> tree + + with forest : Set := + | leaf : B -> forest + | cons : tree -> forest -> forest. + +This declaration generates automatically six induction principles. They are +respectively called :g:`tree_rec`, :g:`tree_ind`, :g:`tree_rect`, +:g:`forest_rec`, :g:`forest_ind`, :g:`forest_rect`. These ones are not the most +general ones but are just the induction principles corresponding to each +inductive part seen as a single inductive definition. + +To illustrate this point on our example, we give the types of :g:`tree_rec` +and :g:`forest_rec`. + +.. coqtop:: all + + Check tree_rec. + + Check forest_rec. + +Assume we want to parametrize our mutual inductive definitions with the +two type variables :g:`A` and :g:`B`, the declaration should be +done the following way: + +.. coqtop:: in + + Inductive tree (A B:Set) : Set := + node : A -> forest A B -> tree A B + + with forest (A B:Set) : Set := + | leaf : B -> forest A B + | cons : tree A B -> forest A B -> forest A B. + +Assume we define an inductive definition inside a section. When the +section is closed, the variables declared in the section and occurring +free in the declaration are added as parameters to the inductive +definition. + +See also Section :ref:`section-mechanism`. + +.. _coinductive-types: + +Co-inductive types +~~~~~~~~~~~~~~~~~~ + +The objects of an inductive type are well-founded with respect to the +constructors of the type. In other words, such objects contain only a +*finite* number of constructors. Co-inductive types arise from relaxing +this condition, and admitting types whose objects contain an infinity of +constructors. Infinite objects are introduced by a non-ending (but +effective) process of construction, defined in terms of the constructors +of the type. + +An example of a co-inductive type is the type of infinite sequences of +natural numbers, usually called streams. It can be introduced in +Coq using the ``CoInductive`` command: + +.. coqtop:: all + + CoInductive Stream : Set := + Seq : nat -> Stream -> Stream. + +The syntax of this command is the same as the command :cmd:`Inductive`. Notice +that no principle of induction is derived from the definition of a co-inductive +type, since such principles only make sense for inductive ones. For co-inductive +ones, the only elimination principle is case analysis. For example, the usual +destructors on streams :g:`hd:Stream->nat` and :g:`tl:Str->Str` can be defined +as follows: + +.. coqtop:: all + + Definition hd (x:Stream) := let (a,s) := x in a. + Definition tl (x:Stream) := let (a,s) := x in s. + +Definition of co-inductive predicates and blocks of mutually +co-inductive definitions are also allowed. An example of a co-inductive +predicate is the extensional equality on streams: + +.. coqtop:: all + + CoInductive EqSt : Stream -> Stream -> Prop := + eqst : forall s1 s2:Stream, + hd s1 = hd s2 -> EqSt (tl s1) (tl s2) -> EqSt s1 s2. + +In order to prove the extensionally equality of two streams :g:`s1` and :g:`s2` +we have to construct an infinite proof of equality, that is, an infinite object +of type :g:`(EqSt s1 s2)`. We will see how to introduce infinite objects in +Section :ref:`cofixpoint`. + +Definition of recursive functions +--------------------------------- + +Definition of functions by recursion over inductive objects +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +This section describes the primitive form of definition by recursion over +inductive objects. See the :cmd:`Function` command for more advanced +constructions. + +.. _Fixpoint: + +.. cmd:: Fixpoint @ident @params {struct @ident} : @type := @term. + +This command allows defining functions by pattern-matching over inductive objects +using a fixed point construction. The meaning of this declaration is to +define :token:`ident` a recursive function with arguments specified by the +binders in :token:`params` such that :token:`ident` applied to arguments corresponding +to these binders has type :token:`type`:math:`_0`, and is equivalent to the +expression :token:`term`:math:`_0`. The type of the :token:`ident` is consequently +:g:`forall` :token:`params`, :token:`type`:math:`_0` and the value is equivalent to +:g:`fun` :token:`params` :g:`=>` :token:`term`:math:`_0`. + +To be accepted, a ``Fixpoint`` definition has to satisfy some syntactical +constraints on a special argument called the decreasing argument. They +are needed to ensure that the Fixpoint definition always terminates. The +point of the {struct :token:`ident`} annotation is to let the user tell the +system which argument decreases along the recursive calls. For instance, +one can define the addition function as : + +.. coqtop:: all + + Fixpoint add (n m:nat) {struct n} : nat := + match n with + | O => m + | S p => S (add p m) + end. + +The ``{struct`` :token:`ident```}`` annotation may be left implicit, in this case the +system try successively arguments from left to right until it finds one that +satisfies the decreasing condition. + +.. note:: + + Some fixpoints may have several arguments that fit as decreasing + arguments, and this choice influences the reduction of the fixpoint. Hence an + explicit annotation must be used if the leftmost decreasing argument is not the + desired one. Writing explicit annotations can also speed up type-checking of + large mutual fixpoints. + +The match operator matches a value (here :g:`n`) with the various +constructors of its (inductive) type. The remaining arguments give the +respective values to be returned, as functions of the parameters of the +corresponding constructor. Thus here when :g:`n` equals :g:`O` we return +:g:`m`, and when :g:`n` equals :g:`(S p)` we return :g:`(S (add p m))`. + +The match operator is formally described in detail in Section +:ref:`match-construction`. +The system recognizes that in the inductive call :g:`(add p m)` the first +argument actually decreases because it is a *pattern variable* coming from +:g:`match n with`. + +.. example:: + + The following definition is not correct and generates an error message: + + .. coqtop:: all + + Fail Fixpoint wrongplus (n m:nat) {struct n} : nat := + match m with + | O => n + | S p => S (wrongplus n p) + end. + + because the declared decreasing argument n actually does not decrease in + the recursive call. The function computing the addition over the second + argument should rather be written: + + .. coqtop:: all + + Fixpoint plus (n m:nat) {struct m} : nat := + match m with + | O => n + | S p => S (plus n p) + end. + +.. example:: + + The ordinary match operation on natural numbers can be mimicked in the + following way. + + .. coqtop:: all + + Fixpoint nat_match + (C:Set) (f0:C) (fS:nat -> C -> C) (n:nat) {struct n} : C := + match n with + | O => f0 + | S p => fS p (nat_match C f0 fS p) + end. + +.. example:: + + The recursive call may not only be on direct subterms of the recursive + variable n but also on a deeper subterm and we can directly write the + function mod2 which gives the remainder modulo 2 of a natural number. + + .. coqtop:: all + + Fixpoint mod2 (n:nat) : nat := + match n with + | O => O + | S p => match p with + | O => S O + | S q => mod2 q + end + end. + +In order to keep the strong normalization property, the fixed point +reduction will only be performed when the argument in position of the +decreasing argument (which type should be in an inductive definition) +starts with a constructor. + +The ``Fixpoint`` construction enjoys also the with extension to define functions +over mutually defined inductive types or more generally any mutually recursive +definitions. + +.. cmdv:: Fixpoint @ident @params {struct @ident} : @type := @term {* with @ident {+ @params} : @type := @term}. + +allows to define simultaneously fixpoints. + +The size of trees and forests can be defined the following way: + +.. coqtop:: all + + Fixpoint tree_size (t:tree) : nat := + match t with + | node a f => S (forest_size f) + end + with forest_size (f:forest) : nat := + match f with + | leaf b => 1 + | cons t f' => (tree_size t + forest_size f') + end. + +A generic command Scheme is useful to build automatically various mutual +induction principles. It is described in Section +:ref:`proofschemes-induction-principles`. + +.. _cofixpoint: + +Definitions of recursive objects in co-inductive types +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. cmd:: CoFixpoint @ident : @type := @term. + +introduces a method for constructing an infinite object of a coinductive +type. For example, the stream containing all natural numbers can be +introduced applying the following method to the number :g:`O` (see +Section :ref:`coinductive-types` for the definition of :g:`Stream`, :g:`hd` and +:g:`tl`): + +.. coqtop:: all + + CoFixpoint from (n:nat) : Stream := Seq n (from (S n)). + +Oppositely to recursive ones, there is no decreasing argument in a +co-recursive definition. To be admissible, a method of construction must +provide at least one extra constructor of the infinite object for each +iteration. A syntactical guard condition is imposed on co-recursive +definitions in order to ensure this: each recursive call in the +definition must be protected by at least one constructor, and only by +constructors. That is the case in the former definition, where the +single recursive call of :g:`from` is guarded by an application of +:g:`Seq`. On the contrary, the following recursive function does not +satisfy the guard condition: + +.. coqtop:: all + + Fail CoFixpoint filter (p:nat -> bool) (s:Stream) : Stream := + if p (hd s) then Seq (hd s) (filter p (tl s)) else filter p (tl s). + +The elimination of co-recursive definition is done lazily, i.e. the +definition is expanded only when it occurs at the head of an application +which is the argument of a case analysis expression. In any other +context, it is considered as a canonical expression which is completely +evaluated. We can test this using the command ``Eval``, which computes +the normal forms of a term: + +.. coqtop:: all + + Eval compute in (from 0). + Eval compute in (hd (from 0)). + Eval compute in (tl (from 0)). + +.. cmdv:: CoFixpoint @ident @params : @type := @term + + As for most constructions, arguments of co-fixpoints expressions + can be introduced before the :g:`:=` sign. + +.. cmdv:: CoFixpoint @ident : @type := @term {+ with @ident : @type := @term } + + As in the :cmd:`Fixpoint` command, it is possible to introduce a block of + mutually dependent methods. + +.. _Assertions: + +Assertions and proofs +--------------------- + +An assertion states a proposition (or a type) of which the proof (or an +inhabitant of the type) is interactively built using tactics. The interactive +proof mode is described in Chapter :ref:`proofhandling` and the tactics in +Chapter :ref:`Tactics`. The basic assertion command is: + +.. cmd:: Theorem @ident : @type. + +After the statement is asserted, Coq needs a proof. Once a proof of +:token:`type` under the assumptions represented by :token:`binders` is given and +validated, the proof is generalized into a proof of forall , :token:`type` and +the theorem is bound to the name :token:`ident` in the environment. + +.. exn:: The term @term has type @type which should be Set, Prop or Type + +.. exn:: @ident already exists (Theorem) + + The name you provided is already defined. You have then to choose + another name. + +.. cmdv:: Lemma @ident : @type. + :name: Lemma + +.. cmdv:: Remark @ident : @type. + :name: Remark + +.. cmdv:: Fact @ident : @type. + :name: Fact + +.. cmdv:: Corollary @ident : @type. + :name: Corollary + +.. cmdv:: Proposition @ident : @type. + :name: Proposition + + These commands are synonyms of ``Theorem`` :token:`ident` : :token:`type`. + +.. cmdv:: Theorem @ident : @type {* with @ident : @type}. + + This command is useful for theorems that are proved by simultaneous induction + over a mutually inductive assumption, or that assert mutually dependent + statements in some mutual co-inductive type. It is equivalent to + :cmd:`Fixpoint` or :cmd:`CoFixpoint` but using tactics to build the proof of + the statements (or the body of the specification, depending on the point of + view). The inductive or co-inductive types on which the induction or + coinduction has to be done is assumed to be non ambiguous and is guessed by + the system. + + Like in a :cmd:`Fixpoint` or :cmd:`CoFixpoint` definition, the induction hypotheses + have to be used on *structurally smaller* arguments (for a :cmd:`Fixpoint`) or + be *guarded by a constructor* (for a :cmd:`CoFixpoint`). The verification that + recursive proof arguments are correct is done only at the time of registering + the lemma in the environment. To know if the use of induction hypotheses is + correct at some time of the interactive development of a proof, use the + command :cmd:`Guarded`. + + The command can be used also with :cmd:`Lemma`, :cmd:`Remark`, etc. instead of + :cmd:`Theorem`. + +.. cmdv:: Definition @ident : @type. + + This allows defining a term of type :token:`type` using the proof editing + mode. It behaves as Theorem but is intended to be used in conjunction with + :cmd:`Defined` in order to define a constant of which the computational + behavior is relevant. + + The command can be used also with :cmd:`Example` instead of :cmd:`Definition`. + + See also :cmd:`Opaque`, :cmd:`Transparent`, :tacn:`unfold`. + +.. cmdv:: Let @ident : @type. + + Like Definition :token:`ident` : :token:`type`. except that the definition is + turned into a let-in definition generalized over the declarations depending + on it after closing the current section. + +.. cmdv:: Fixpoint @ident @binders with . + + This generalizes the syntax of Fixpoint so that one or more bodies + can be defined interactively using the proof editing mode (when a + body is omitted, its type is mandatory in the syntax). When the block + of proofs is completed, it is intended to be ended by Defined. + +.. cmdv:: CoFixpoint @ident with. + + This generalizes the syntax of CoFixpoint so that one or more bodies + can be defined interactively using the proof editing mode. + +.. cmd:: Proof + + A proof starts by the keyword Proof. Then Coq enters the proof editing mode + until the proof is completed. The proof editing mode essentially contains + tactics that are described in chapter :ref:`Tactics`. Besides tactics, there + are commands to manage the proof editing mode. They are described in Chapter + :ref:`proofhandling`. + +.. cmd:: Qed + + When the proof is completed it should be validated and put in the environment + using the keyword Qed. + +.. exn:: @ident already exists (Qed) + +.. note:: + + #. Several statements can be simultaneously asserted. + + #. Not only other assertions but any vernacular command can be given + while in the process of proving a given assertion. In this case, the + command is understood as if it would have been given before the + statements still to be proved. + + #. Proof is recommended but can currently be omitted. On the opposite + side, Qed (or Defined, see below) is mandatory to validate a proof. + + #. Proofs ended by Qed are declared opaque. Their content cannot be + unfolded (see :ref:`performingcomputations`), thus + realizing some form of *proof-irrelevance*. To be able to unfold a + proof, the proof should be ended by Defined (see below). + +.. cmdv:: Defined + :name: Defined + + Same as :cmd:`Qed` but the proof is then declared transparent, which means + that its content can be explicitly used for type-checking and that it can be + unfolded in conversion tactics (see :ref:`performingcomputations`, + :cmd:`Opaque`, :cmd:`Transparent`). + +.. cmdv:: Admitted. + :name: Admitted + + Turns the current asserted statement into an axiom and exits the proof mode. + +.. [1] + This is similar to the expression “*entry* :math:`\{` sep *entry* + :math:`\}`” in standard BNF, or “*entry* :math:`(` sep *entry* + :math:`)`\ \*” in the syntax of regular expressions. + +.. [2] + Except if the inductive type is empty in which case there is no + equation that can be used to infer the return type. diff --git a/doc/sphinx/practical-tools/coq-commands.rst b/doc/sphinx/practical-tools/coq-commands.rst index 1ff808894a..93dcfca4bf 100644 --- a/doc/sphinx/practical-tools/coq-commands.rst +++ b/doc/sphinx/practical-tools/coq-commands.rst @@ -16,6 +16,8 @@ The options are (basically) the same for the first two commands, and roughly described below. You can also look at the ``man`` pages of ``coqtop`` and ``coqc`` for more details. +.. _interactive-use: + Interactive use (coqtop) ------------------------ @@ -39,10 +41,12 @@ Batch compilation (coqc) The ``coqc`` command takes a name *file* as argument. Then it looks for a vernacular file named *file*.v, and tries to compile it into a -*file*.vo file (See :ref:`TODO-6.5`). Warning: The name *file* should be a -regular |Coq| identifier, as defined in Section :ref:'TODO-1.1'. It should contain -only letters, digits or underscores (_). For instance, ``/bar/foo/toto.v`` is valid, but -``/bar/foo/to-to.v`` is invalid. +*file*.vo file (See :ref:`compiled-files`). + +.. caution:: The name *file* should be a + regular |Coq| identifier, as defined in Section :ref:'TODO-1.1'. It should contain + only letters, digits or underscores (_). For instance, ``/bar/foo/toto.v`` is valid, but + ``/bar/foo/to-to.v`` is invalid. Customization at launch time @@ -63,6 +67,7 @@ This file may contain, for instance, ``Add LoadPath`` commands to add directories to the load path of |Coq|. It is possible to skip the loading of the resource file with the option ``-q``. +.. _customization-by-environment-variables: By environment variables ~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -70,7 +75,7 @@ By environment variables Load path can be specified to the |Coq| system by setting up ``$COQPATH`` environment variable. It is a list of directories separated by ``:`` (``;`` on Windows). |Coq| will also honor ``$XDG_DATA_HOME`` and -``$XDG_DATA_DIRS`` (see Section :ref:`TODO-2.6.3`). +``$XDG_DATA_DIRS`` (see Section :ref:`libraries-and-filesystem`). Some |Coq| commands call other |Coq| commands. In this case, they look for the commands in directory specified by ``$COQBIN``. If this variable is @@ -84,6 +89,8 @@ list of assignments of the form ``name=``:n:``{*; attr}`` where ANSI escape code. The list of highlight tags can be retrieved with the ``-list-tags`` command-line option of ``coqtop``. +.. _command-line-options: + By command line options ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -91,25 +98,25 @@ The following command-line options are recognized by the commands ``coqc`` and ``coqtop``, unless stated otherwise: :-I *directory*, -include *directory*: Add physical path *directory* - to the OCaml loadpath. See also: :ref:`TODO-2.6.1` and the - command Declare ML Module Section :ref:`TODO-6.5`. + to the OCaml loadpath. See also: :ref:`names-of-libraries` and the + command Declare ML Module Section :ref:`compiled-files`. :-Q *directory* dirpath: Add physical path *directory* to the list of directories where |Coq| looks for a file and bind it to the the logical directory *dirpath*. The subdirectory structure of *directory* is recursively available from |Coq| using absolute names (extending the - dirpath prefix) (see Section :ref:`TODO-2.6.2`).Note that only those + dirpath prefix) (see Section :ref:`qualified-names`).Note that only those subdirectories and files which obey the lexical conventions of what is - an ident (see Section :ref:`TODO-1.1`) are taken into account. Conversely, the + an :n:`@ident` are taken into account. Conversely, the underlying file systems or operating systems may be more restrictive than |Coq|. While Linux’s ext4 file system supports any |Coq| recursive layout (within the limit of 255 bytes per file name), the default on NTFS (Windows) or HFS+ (MacOS X) file systems is on the contrary to disallow two files differing only in the case in the same directory. - See also: Section :ref:`TODO-2.6.1`. + See also: Section :ref:`names-of-libraries`. :-R *directory* dirpath: Do as -Q *directory* dirpath but make the subdirectory structure of *directory* recursively visible so that the recursive contents of physical *directory* is available from |Coq| using - short or partially qualified names. See also: Section :ref:`TODO-2.6.1`. + short or partially qualified names. See also: Section :ref:`names-of-libraries`. :-top dirpath: Set the toplevel module name to dirpath instead of Top. Not valid for `coqc` as the toplevel module name is inferred from the name of the output file. @@ -145,7 +152,7 @@ and ``coqtop``, unless stated otherwise: -compile-verbose. :-w (all|none|w₁,…,wₙ): Configure the display of warnings. This option expects all, none or a comma-separated list of warning names or - categories (see Section :ref:`TODO-6.9.3`). + categories (see Section :ref:`controlling-display`). :-color (on|off|auto): Enable or not the coloring of output of `coqtop`. Default is auto, meaning that `coqtop` dynamically decides, depending on whether the output channel supports ANSI escape sequences. @@ -170,7 +177,7 @@ and ``coqtop``, unless stated otherwise: :-compat *version*: Attempt to maintain some backward-compatibility with a previous version. :-dump-glob *file*: Dump references for global names in file *file* - (to be used by coqdoc, see :ref:`TODO-15.4`). By default, if *file.v* is being + (to be used by coqdoc, see :ref:`coqdoc`). By default, if *file.v* is being compiled, *file.glob* is used. :-no-glob: Disable the dumping of references for global names. :-image *file*: Set the binary image to be used by `coqc` to be *file* diff --git a/doc/sphinx/practical-tools/coqide.rst b/doc/sphinx/practical-tools/coqide.rst index 1fcfc665be..f9903e6104 100644 --- a/doc/sphinx/practical-tools/coqide.rst +++ b/doc/sphinx/practical-tools/coqide.rst @@ -10,7 +10,7 @@ used as a user-friendly replacement to `coqtop`. Its main purpose is to allow the user to navigate forward and backward into a Coq vernacular file, executing corresponding commands or undoing them respectively. -CoqIDE is run by typing the command `coqide` on the command line. +|CoqIDE| is run by typing the command `coqide` on the command line. Without argument, the main screen is displayed with an “unnamed buffer”, and with a file name as argument, another buffer displaying the contents of that file. Additionally, `coqide` accepts the same @@ -43,7 +43,7 @@ is the one where Coq commands are currently executed. Buffers may be edited as in any text editor, and classical basic editing commands (Copy/Paste, …) are available in the *Edit* menu. -CoqIDE offers only basic editing commands, so if you need more complex +|CoqIDE| offers only basic editing commands, so if you need more complex editing commands, you may launch your favorite text editor on the current buffer, using the *Edit/External Editor* menu. @@ -75,7 +75,7 @@ There are two additional buttons for navigation within the running buffer. The "down" button with a line goes directly to the end; the "up" button with a line goes back to the beginning. The handling of errors when using the go-to-the-end button depends on whether |Coq| is running in asynchronous mode or not (see -Chapter :ref:`Asyncprocessing`). If it is not running in that mode, execution +Chapter :ref:`asynchronousandparallelproofprocessing`). If it is not running in that mode, execution stops as soon as an error is found. Otherwise, execution continues, and the error is marked with an underline in the error foreground color, with a background in the error background color (pink by default). The same @@ -86,14 +86,14 @@ If you ever try to execute a command which happens to run during a long time, and would like to abort it before its termination, you may use the interrupt button (the white cross on a red circle). -There are other buttons on the CoqIDE toolbar: a button to save the running +There are other buttons on the |CoqIDE| toolbar: a button to save the running buffer; a button to close the current buffer (an "X"); buttons to switch among buffers (left and right arrows); an "information" button; and a "gears" button. -The "information" button is described in Section :ref:`sec:trytactics`. +The "information" button is described in Section :ref:`try-tactics-automatically`. The "gears" button submits proof terms to the |Coq| kernel for type-checking. -When |Coq| uses asynchronous processing (see Chapter :ref:`Asyncprocessing`), +When |Coq| uses asynchronous processing (see Chapter :ref:`asynchronousandparallelproofprocessing`), proofs may have been completed without kernel-checking of generated proof terms. The presence of unchecked proof terms is indicated by ``Qed`` statements that have a subdued *being-processed* color (light blue by default), rather than the @@ -150,18 +150,16 @@ arguments. Queries ------------ -.. _coqide_queryselected: - .. image:: ../_static/coqide-queries.png :alt: |CoqIDE| queries We call *query* any vernacular command that does not change the current state, such as ``Check``, ``Search``, etc. To run such commands interactively, without -writing them in scripts, CoqIDE offers a *query pane*. The query pane can be +writing them in scripts, |CoqIDE| offers a *query pane*. The query pane can be displayed on demand by using the ``View`` menu, or using the shortcut ``F1``. Queries can also be performed by selecting a particular phrase, then choosing an item from the ``Queries`` menu. The response then appears in the message window. -Figure :ref:`fig:queryselected` shows the result after selecting of the phrase +The image above shows the result after selecting of the phrase ``Nat.mul`` in the script window, and choosing ``Print`` from the ``Queries`` menu. @@ -221,7 +219,7 @@ still edit this configuration file by hand, but this is more involved. Using Unicode symbols -------------------------- -CoqIDE is based on GTK+ and inherits from it support for Unicode in +|CoqIDE| is based on GTK+ and inherits from it support for Unicode in its text windows. Consequently a large set of symbols is available for notations. diff --git a/doc/sphinx/practical-tools/utilities.rst b/doc/sphinx/practical-tools/utilities.rst new file mode 100644 index 0000000000..59867988a4 --- /dev/null +++ b/doc/sphinx/practical-tools/utilities.rst @@ -0,0 +1,1008 @@ +.. include:: ../replaces.rst + +.. _utilities: + +--------------------- + Utilities +--------------------- + +The distribution provides utilities to simplify some tedious works +beside proof development, tactics writing or documentation. + + +Using Coq as a library +---------------------- + +In previous versions, ``coqmktop`` was used to build custom +toplevels - for example for better debugging or custom static +linking. Nowadays, the preferred method is to use ``ocamlfind``. + +The most basic custom toplevel is built using: + +:: + + % ocamlfind ocamlopt -thread -rectypes -linkall -linkpkg \ + -package coq.toplevel \ + toplevel/coqtop\_bin.ml -o my\_toplevel.native + + +For example, to statically link |L_tac|, you can just do: + +:: + + % ocamlfind ocamlopt -thread -rectypes -linkall -linkpkg \ + -package coq.toplevel -package coq.ltac \ + toplevel/coqtop\_bin.ml -o my\_toplevel.native + +and similarly for other plugins. + + +Building a |Coq| project with coq_makefile +------------------------------------------ + +The majority of |Coq| projects are very similar: a collection of ``.v`` +files and eventually some ``.ml`` ones (a |Coq| plugin). The main piece of +metadata needed in order to build the project are the command line +options to ``coqc`` (e.g. ``-R``, ``-I``, see also: Section +:ref:`command-line-options`). Collecting the list of files and options is the job +of the ``_CoqProject`` file. + +A simple example of a ``_CoqProject`` file follows: + +:: + + -R theories/ MyCode + theories/foo.v + theories/bar.v + -I src/ + src/baz.ml4 + src/bazaux.ml + src/qux_plugin.mlpack + + +Currently, both |CoqIDE| and Proof-General (version ≥ ``4.3pre``) +understand ``_CoqProject`` files and invoke |Coq| with the desired options. + +The ``coq_makefile`` utility can be used to set up a build infrastructure +for the |Coq| project based on makefiles. The recommended way of +invoking ``coq_makefile`` is the following one: + +:: + + coq_makefile -f _CoqProject -o CoqMakefile + + +Such command generates the following files: + +CoqMakefile + is a generic makefile for ``GNU Make`` that provides + targets to build the project (both ``.v`` and ``.ml*`` files), to install it + system-wide in the ``coq-contrib`` directory (i.e. where |Coq| is installed) + as well as to invoke coqdoc to generate HTML documentation. + +CoqMakefile.conf + contains make variables assignments that reflect + the contents of the ``_CoqProject`` file as well as the path relevant to + |Coq|. + + +An optional file ``CoqMakefile.local`` can be provided by the user in order to +extend ``CoqMakefile``. In particular one can declare custom actions to be +performed before or after the build process. Similarly one can customize the +install target or even provide new targets. Extension points are documented in +paragraph :ref:`coqmakefilelocal`. + +The extensions of the files listed in ``_CoqProject`` is used in order to +decide how to build them. In particular: + + ++ |Coq| files must use the ``.v`` extension ++ |OCaml| files must use the ``.ml`` or ``.mli`` extension ++ |OCaml| files that require pre processing for syntax + extensions (like ``VERNAC EXTEND``) must use the ``.ml4`` extension ++ In order to generate a plugin one has to list all |OCaml| + modules (i.e. ``Baz`` for ``baz.ml``) in a ``.mlpack`` file (or ``.mllib`` + file). + + +The use of ``.mlpack`` files has to be preferred over ``.mllib`` files, +since it results in a “packed” plugin: All auxiliary modules (as +``Baz`` and ``Bazaux``) are hidden inside the plugin’s “name space” +(``Qux_plugin``). This reduces the chances of begin unable to load two +distinct plugins because of a clash in their auxiliary module names. + +.. _coqmakefilelocal: + +CoqMakefile.local +~~~~~~~~~~~~~~~~~ + +The optional file ``CoqMakefile.local`` is included by the generated +file ``CoqMakefile``. It can contain two kinds of directives. + +**Variable assignment** + +The variable must belong to the variables listed in the ``Parameters`` +section of the generated makefile. +Here we describe only few of them. + +:CAMLPKGS: + can be used to specify third party findlib packages, and is + passed to the OCaml compiler on building or linking of modules. Eg: + ``-package yojson``. +:CAMLFLAGS: + can be used to specify additional flags to the |OCaml| + compiler, like ``-bin-annot`` or ``-w``.... +:COQC, COQDEP, COQDOC: + can be set in order to use alternative binaries + (e.g. wrappers) +:COQ_SRC_SUBDIRS: + can be extended by including other paths in which ``*.cm*`` files + are searched. For example ``COQ\_SRC\_SUBDIRS+=user-contrib/Unicoq`` + lets you build a plugin containing OCaml code that depends on the + OCaml code of ``Unicoq``. + +**Rule extension** + +The following makefile rules can be extended. + +.. example:: + + :: + + pre-all:: + echo "This line is print before making the all target" + install-extra:: + cp ThisExtraFile /there/it/goes + +``pre-all::`` + run before the ``all`` target. One can use this to configure + the project, or initialize sub modules or check dependencies are met. + +``post-all::`` + run after the ``all`` target. One can use this to run a test + suite, or compile extracted code. + +``install-extra::`` + run after ``install``. One can use this to install extra files. + +``install-doc::`` + One can use this to install extra doc. + +``uninstall::`` + \ + +``uninstall-doc::`` + \ + +``clean::`` + \ + +``cleanall::`` + \ + +``archclean::`` + \ + +``merlin-hook::`` + One can append lines to the generated ``.merlin`` file extending this + target. + +Timing targets and performance testing +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The generated ``Makefile`` supports the generation of two kinds of timing +data: per-file build-times, and per-line times for an individual file. + +The following targets and Makefile variables allow collection of per- +file timing data: + + ++ ``TIMED=1`` + passing this variable will cause ``make`` to emit a line + describing the user-space build-time and peak memory usage for each + file built. + + .. note:: + On ``Mac OS``, this works best if you’ve installed ``gnu-time``. + + .. example:: + For example, the output of ``make TIMED=1`` may look like + this: + + :: + + COQDEP Fast.v + COQDEP Slow.v + COQC Slow.v + Slow (user: 0.34 mem: 395448 ko) + COQC Fast.v + Fast (user: 0.01 mem: 45184 ko) + ++ ``pretty-timed`` + this target stores the output of ``make TIMED=1`` into + ``time-of-build.log``, and displays a table of the times, sorted from + slowest to fastest, which is also stored in ``time-of-build-pretty.log``. + If you want to construct the ``log`` for targets other than the default + one, you can pass them via the variable ``TGTS``, e.g., ``make pretty-timed + TGTS="a.vo b.vo"``. + + .. :: + This target requires ``python`` to build the table. + + .. note:: + This target will *append* to the timing log; if you want a + fresh start, you must remove the ``filetime-of-build.log`` or + ``run make cleanall``. + + .. example:: + + For example, the output of ``make pretty-timed`` may look like this: + + :: + + COQDEP Fast.v + COQDEP Slow.v + COQC Slow.v + Slow (user: 0.36 mem: 393912 ko) + COQC Fast.v + Fast (user: 0.05 mem: 45992 ko) + Time | File Name + -------------------- + 0m00.41s | Total + -------------------- + 0m00.36s | Slow + 0m00.05s | Fast + + ++ ``print-pretty-timed-diff`` + this target builds a table of timing + changes between two compilations; run ``make make-pretty-timed-before`` to + build the log of the “before” times, and run ``make make-pretty-timed- + after`` to build the log of the “after” times. The table is printed on + the command line, and stored in ``time-of-build-both.log``. This target is + most useful for profiling the difference between two commits to a + repo. + + .. note:: + This target requires ``python`` to build the table. + + .. note:: + The ``make-pretty-timed-before`` and ``make-pretty-timed-after`` targets will + *append* to the timing log; if you want a fresh start, you must remove + the files ``time-of-build-before.log`` and ``time-of-build-after.log`` or run + ``make cleanall`` *before* building either the “before” or “after” + targets. + + .. note:: + The table will be sorted first by absolute time + differences rounded towards zero to a whole-number of seconds, then by + times in the “after” column, and finally lexicographically by file + name. This will put the biggest changes in either direction first, and + will prefer sorting by build-time over subsecond changes in build time + (which are frequently noise); lexicographic sorting forces an order on + files which take effectively no time to compile. + + .. example:: + For example, the output table from + ``make print-pretty-timed-diff`` may look like this: + + :: + + After | File Name | Before || Change | % Change + -------------------------------------------------------- + 0m00.39s | Total | 0m00.35s || +0m00.03s | +11.42% + -------------------------------------------------------- + 0m00.37s | Slow | 0m00.01s || +0m00.36s | +3600.00% + 0m00.02s | Fast | 0m00.34s || -0m00.32s | -94.11% + + +The following targets and ``Makefile`` variables allow collection of per- +line timing data: + + ++ ``TIMING=1`` + passing this variable will cause ``make`` to use ``coqc -time`` to + write to a ``.v.timing`` file for each ``.v`` file compiled, which contains + line-by-line timing information. + + .. example:: + For example, running ``make all TIMING=1`` may result in a file like this: + + :: + + Chars 0 - 26 [Require~Coq.ZArith.BinInt.] 0.157 secs (0.128u,0.028s) + Chars 27 - 68 [Declare~Reduction~comp~:=~vm_c...] 0. secs (0.u,0.s) + Chars 69 - 162 [Definition~foo0~:=~Eval~comp~i...] 0.153 secs (0.136u,0.019s) + Chars 163 - 208 [Definition~foo1~:=~Eval~comp~i...] 0.239 secs (0.236u,0.s) + ++ ``print-pretty-single-time-diff`` + :: + print-pretty-single-time-diff BEFORE=path/to/file.v.before-timing AFTER=path/to/file.v.after-timing + + this target will make a sorted table of the per-line timing differences + between the timing logs in the ``BEFORE`` and ``AFTER`` files, display it, and + save it to the file specified by the ``TIME_OF_PRETTY_BUILD_FILE`` variable, + which defaults to ``time-of-build-pretty.log``. + To generate the ``.v.before-timing`` or ``.v.after-timing`` files, you should + pass ``TIMING=before`` or ``TIMING=after`` rather than ``TIMING=1``. + + .. note:: + The sorting used here is the same as in the ``print-pretty-timed -diff`` target. + + .. note:: + This target requires python to build the table. + + .. example:: + For example, running ``print-pretty-single-time-diff`` might give a table like this: + + :: + + After | Code | Before || Change | % Change + --------------------------------------------------------------------------------------------------- + 0m00.50s | Total | 0m04.17s || -0m03.66s | -87.96% + --------------------------------------------------------------------------------------------------- + 0m00.145s | Chars 069 - 162 [Definition~foo0~:=~Eval~comp~i...] | 0m00.192s || -0m00.04s | -24.47% + 0m00.126s | Chars 000 - 026 [Require~Coq.ZArith.BinInt.] | 0m00.143s || -0m00.01s | -11.88% + N/A | Chars 027 - 068 [Declare~Reduction~comp~:=~nati...] | 0m00.s || +0m00.00s | N/A + 0m00.s | Chars 027 - 068 [Declare~Reduction~comp~:=~vm_c...] | N/A || +0m00.00s | N/A + 0m00.231s | Chars 163 - 208 [Definition~foo1~:=~Eval~comp~i...] | 0m03.836s || -0m03.60s | -93.97% + + ++ ``all.timing.diff``, ``path/to/file.v.timing.diff`` + The ``path/to/file.v.timing.diff`` target will make a ``.v.timing.diff`` file for + the corresponding ``.v`` file, with a table as would be generated by + the ``print-pretty-single-time-diff`` target; it depends on having already + made the corresponding ``.v.before-timing`` and ``.v.after-timing`` files, + which can be made by passing ``TIMING=before`` and ``TIMING=after``. + The ``all.timing.diff`` target will make such timing difference files for + all of the ``.v`` files that the ``Makefile`` knows about. It will fail if + some ``.v.before-timing`` or ``.v.after-timing`` files don’t exist. + + .. note:: + This target requires python to build the table. + + +Reusing/extending the generated Makefile +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Including the generated makefile with an include directive is +discouraged. The contents of this file, including variable names and +status of rules shall change in the future. Users are advised to +include ``Makefile.conf`` or call a target of the generated Makefile as in +``make -f Makefile target`` from another Makefile. + +One way to get access to all targets of the generated ``CoqMakefile`` is to +have a generic target for invoking unknown targets. + +.. example:: + + :: + + # KNOWNTARGETS will not be passed along to CoqMakefile + KNOWNTARGETS := CoqMakefile extra-stuff extra-stuff2 + # KNOWNFILES will not get implicit targets from the final rule, and so + # depending on them won't invoke the submake + # Warning: These files get declared as PHONY, so any targets depending + # on them always get rebuilt + KNOWNFILES := Makefile _CoqProject + + .DEFAULT_GOAL := invoke-coqmakefile + + CoqMakefile: Makefile _CoqProject + $(COQBIN)coq_makefile -f _CoqProject -o CoqMakefile + + invoke-coqmakefile: CoqMakefile + $(MAKE) --no-print-directory -f CoqMakefile $(filter-out $(KNOWNTARGETS),$(MAKECMDGOALS)) + + .PHONY: invoke-coqmakefile $(KNOWNFILES) + + #################################################################### + ## Your targets here ## + #################################################################### + + # This should be the last rule, to handle any targets not declared above + %: invoke-coqmakefile + @true + + + +Building a subset of the targets with ``-j`` +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To build, say, two targets foo.vo and bar.vo in parallel one can use +``make only TGTS="foo.vo bar.vo" -j``. + +.. note:: + + ``make foo.vo bar.vo -j`` has a different meaning for the make + utility, in particular it may build a shared prerequisite twice. + + +.. note:: + + For users of coq_makefile with version < 8.7 + + + Support for “sub-directory” is deprecated. To perform actions before + or after the build (like invoking ``make`` on a subdirectory) one can hook + in pre-all and post-all extension points. + + ``-extra-phony`` and ``-extra`` are deprecated. To provide additional target + (``.PHONY`` or not) please use ``CoqMakefile.local``. + + + +Modules dependencies +-------------------- + +In order to compute modules dependencies (so to use ``make``), |Coq| comes +with an appropriate tool, ``coqdep``. + +``coqdep`` computes inter-module dependencies for |Coq| and |OCaml| +programs, and prints the dependencies on the standard output in a +format readable by make. When a directory is given as argument, it is +recursively looked at. + +Dependencies of |Coq| modules are computed by looking at ``Require`` +commands (``Require``, ``Require Export``, ``Require Import``), but also at the +command ``Declare ML Module``. + +Dependencies of |OCaml| modules are computed by looking at +`open` commands and the dot notation *module.value*. However, this is +done approximately and you are advised to use ``ocamldep`` instead for the +|OCaml| modules dependencies. + +See the man page of ``coqdep`` for more details and options. + +The build infrastructure generated by ``coq_makefile`` uses ``coqdep`` to +automatically compute the dependencies among the files part of the +project. + + +.. _coqdoc: + +Documenting |Coq| files with coqdoc +----------------------------------- + +coqdoc is a documentation tool for the proof assistant |Coq|, similar to +``javadoc`` or ``ocamldoc``. The task of coqdoc is + + +#. to produce a nice |Latex| and/or HTML document from the |Coq| + sources, readable for a human and not only for the proof assistant; +#. to help the user navigating in his own (or third-party) sources. + + + +Principles +~~~~~~~~~~ + +Documentation is inserted into |Coq| files as *special comments*. Thus +your files will compile as usual, whether you use coqdoc or not. coqdoc +presupposes that the given |Coq| files are well-formed (at least +lexically). Documentation starts with ``(**``, followed by a space, and +ends with the pending ``*)``. The documentation format is inspired by Todd +A. Coram’s *Almost Free Text (AFT)* tool: it is mainly ``ASCII`` text with +some syntax-light controls, described below. coqdoc is robust: it +shouldn’t fail, whatever the input is. But remember: “garbage in, +garbage out”. + + +|Coq| material inside documentation. +++++++++++++++++++++++++++++++++++++ + +|Coq| material is quoted between the delimiters ``[`` and ``]``. Square brackets +may be nested, the inner ones being understood as being part of the +quoted code (thus you can quote a term like ``fun x => u`` by writing ``[fun +x => u]``). Inside quotations, the code is pretty-printed in the same +way as it is in code parts. + +Pre-formatted vernacular is enclosed by ``[[`` and ``]]``. The former must be +followed by a newline and the latter must follow a newline. + + +Pretty-printing. +++++++++++++++++ + +coqdoc uses different faces for identifiers and keywords. The pretty- +printing of |Coq| tokens (identifiers or symbols) can be controlled +using one of the following commands: + +:: + + + (** printing *token* %...LATEX...% #...html...# *) + + +or + +:: + + + (** printing *token* $...LATEX math...$ #...html...# *) + + +It gives the |Latex| and HTML texts to be produced for the given |Coq| +token. One of the |Latex| or HTML text may be omitted, causing the +default pretty-printing to be used for this token. + +The printing for one token can be removed with + +:: + + + (** remove printing *token* *) + + +Initially, the pretty-printing table contains the following mapping: + +==== === ==== ===== === ==== ==== === +`->` → `<-` ← `*` × +`<=` ≤ `>=` ≥ `=>` ⇒ +`<>` ≠ `<->` ↔ `|-` ⊢ +`\/` ∨ `/\\` ∧ `~` ¬ +==== === ==== ===== === ==== ==== === + +Any of these can be overwritten or suppressed using the printing +commands. + +.. note:: + + The recognition of tokens is done by a (``ocaml``) lex + automaton and thus applies the longest-match rule. For instance, `->~` + is recognized as a single token, where |Coq| sees two tokens. It is the + responsibility of the user to insert space between tokens *or* to give + pretty-printing rules for the possible combinations, e.g. + + :: + + (** printing ->~ %\ensuremath{\rightarrow\lnot}% *) + + + +Sections +++++++++ + +Sections are introduced by 1 to 4 leading stars (i.e. at the beginning +of the line) followed by a space. One star is a section, two stars a +sub-section, etc. The section title is given on the remaining of the +line. + +.. example:: + + :: + + (** * Well-founded relations + + In this section, we introduce... *) + + +Lists. +++++++ + +List items are introduced by a leading dash. coqdoc uses whitespace to +determine the depth of a new list item and which text belongs in which +list items. A list ends when a line of text starts at or before the +level of indenting of the list’s dash. A list item’s dash must always +be the first non-space character on its line (so, in particular, a +list can not begin on the first line of a comment - start it on the +second line instead). + +.. example:: + + :: + + We go by induction on [n]: + - If [n] is 0... + - If [n] is [S n'] we require... + + two paragraphs of reasoning, and two subcases: + + - In the first case... + - In the second case... + + So the theorem holds. + + + +Rules. +++++++ + +More than 4 leading dashes produce a horizontal rule. + + +Emphasis. ++++++++++ + +Text can be italicized by placing it in underscores. A non-identifier +character must precede the leading underscore and follow the trailing +underscore, so that uses of underscores in names aren’t mistaken for +emphasis. Usually, these are spaces or punctuation. + +:: + + This sentence contains some _emphasized text_. + + + +Escaping to |Latex| and HTML. ++++++++++++++++++++++++++++++++ + +Pure |Latex| or HTML material can be inserted using the following +escape sequences: + + ++ ``$...LATEX stuff...$`` inserts some |Latex| material in math mode. + Simply discarded in HTML output. ++ ``%...LATEX stuff...%`` inserts some |Latex| material. Simply + discarded in HTML output. ++ ``#...HTML stuff...#`` inserts some HTML material. Simply discarded in + |Latex| output. + +.. note:: + to simply output the characters ``$``, ``%`` and ``#`` and escaping + their escaping role, these characters must be doubled. + + +Verbatim +++++++++ + +Verbatim material is introduced by a leading ``<<`` and closed by ``>>`` +at the beginning of a line. + +.. example:: + + :: + + Here is the corresponding caml code: + << + let rec fact n = + if n <= 1 then 1 else n * fact (n-1) + >> + + + +Hyperlinks +++++++++++ + +Hyperlinks can be inserted into the HTML output, so that any +identifier is linked to the place of its definition. + +``coqc file.v`` automatically dumps localization information in +``file.glob`` or appends it to a file specified using option ``--dump-glob +file``. Take care of erasing this global file, if any, when starting +the whole compilation process. + +Then invoke coqdoc or ``coqdoc --glob-from file`` to tell coqdoc to look +for name resolutions into the file ``file`` (it will look in ``file.glob`` +by default). + +Identifiers from the |Coq| standard library are linked to the Coq web +site at `<http://coq.inria.fr/library/>`_. This behavior can be changed +using command line options ``--no-externals`` and ``--coqlib``; see below. + + +Hiding / Showing parts of the source. ++++++++++++++++++++++++++++++++++++++ + +Some parts of the source can be hidden using command line options ``-g`` +and ``-l`` (see below), or using such comments: + +:: + + + (* begin hide *) + *some Coq material* + (* end hide *) + + +Conversely, some parts of the source which would be hidden can be +shown using such comments: + +:: + + + (* begin show *) + *some Coq material* + (* end show *) + + +The latter cannot be used around some inner parts of a proof, but can +be used around a whole proof. + + +Usage +~~~~~ + +coqdoc is invoked on a shell command line as follows: +``coqdoc <options and files>``. +Any command line argument which is not an option is considered to be a +file (even if it starts with a ``-``). |Coq| files are identified by the +suffixes ``.v`` and ``.g`` and |Latex| files by the suffix ``.tex``. + + +:HTML output: This is the default output. One HTML file is created for + each |Coq| file given on the command line, together with a file + ``index.html`` (unless ``option-no-index is passed``). The HTML pages use a + style sheet named ``style.css``. Such a file is distributed with coqdoc. +:|Latex| output: A single |Latex| file is created, on standard + output. It can be redirected to a file with option ``-o``. The order of + files on the command line is kept in the final document. |Latex| + files given on the command line are copied ‘as is’ in the final + document . DVI and PostScript can be produced directly with the + options ``-dvi`` and ``-ps`` respectively. +:TEXmacs output: To translate the input files to TEXmacs format, + to be used by the TEXmacs |Coq| interface. + + + +Command line options +++++++++++++++++++++ + + +**Overall options** + + + :--HTML: Select a HTML output. + :--|Latex|: Select a |Latex| output. + :--dvi: Select a DVI output. + :--ps: Select a PostScript output. + :--texmacs: Select a TEXmacs output. + :--stdout: Write output to stdout. + :-o file, --output file: Redirect the output into the file ‘file’ + (meaningless with ``-html``). + :-d dir, --directory dir: Output files into directory ‘dir’ instead of + current directory (option ``-d`` does not change the filename specified + with option ``-o``, if any). + :--body-only: Suppress the header and trailer of the final document. + Thus, you can insert the resulting document into a larger one. + :-p string, --preamble string: Insert some material in the |Latex| + preamble, right before ``\begin{document}`` (meaningless with ``-html``). + :--vernac-file file,--tex-file file: Considers the file ‘file’ + respectively as a ``.v`` (or ``.g``) file or a ``.tex`` file. + :--files-from file: Read file names to process in file ‘file’ as if + they were given on the command line. Useful for program sources split + up into several directories. + :-q, --quiet: Be quiet. Do not print anything except errors. + :-h, --help: Give a short summary of the options and exit. + :-v, --version: Print the version and exit. + + + +**Index options** + + Default behavior is to build an index, for the HTML output only, + into ``index.html``. + + :--no-index: Do not output the index. + :--multi-index: Generate one page for each category and each letter in + the index, together with a top page ``index.html``. + :--index string: Make the filename of the index string instead of + “index”. Useful since “index.html” is special. + + + +**Table of contents option** + + :-toc, --table-of-contents: Insert a table of contents. For a |Latex| + output, it inserts a ``\tableofcontents`` at the beginning of the + document. For a HTML output, it builds a table of contents into + ``toc.html``. + :--toc-depth int: Only include headers up to depth ``int`` in the table of + contents. + + +**Hyperlinks options** + + :--glob-from file: Make references using |Coq| globalizations from file + file. (Such globalizations are obtained with Coq option ``-dump-glob``). + :--no-externals: Do not insert links to the |Coq| standard library. + :--external url coqdir: Use given URL for linking references whose + name starts with prefix ``coqdir``. + :--coqlib url: Set base URL for the Coq standard library (default is + `<http://coq.inria.fr/library/>`_). This is equivalent to ``--external url + Coq``. + :-R dir coqdir: Map physical directory dir to |Coq| logical + directory ``coqdir`` (similarly to |Coq| option ``-R``). + + .. note:: + + option ``-R`` only has + effect on the files *following* it on the command line, so you will + probably need to put this option first. + + +**Title options** + + :-s , --short: Do not insert titles for the files. The default + behavior is to insert a title like “Library Foo” for each file. + :--lib-name string: Print “string Foo” instead of “Library Foo” in + titles. For example “Chapter” and “Module” are reasonable choices. + :--no-lib-name: Print just “Foo” instead of “Library Foo” in titles. + :--lib-subtitles: Look for library subtitles. When enabled, the + beginning of each file is checked for a comment of the form: + + :: + + (** * ModuleName : text *) + + where ``ModuleName`` must be the name of the file. If it is present, the + text is used as a subtitle for the module in appropriate places. + :-t string, --title string: Set the document title. + + +**Contents options** + + :-g, --gallina: Do not print proofs. + :-l, --light: Light mode. Suppress proofs (as with ``-g``) and the following commands: + + + [Recursive] Tactic Definition + + Hint / Hints + + Require + + Transparent / Opaque + + Implicit Argument / Implicits + + Section / Variable / Hypothesis / End + + + + The behavior of options ``-g`` and ``-l`` can be locally overridden using the + ``(* begin show *) … (* end show *)`` environment (see above). + + There are a few options to drive the parsing of comments: + + :--parse-comments: Parses regular comments delimited by ``(*`` and ``*)`` as + well. They are typeset inline. + :--plain-comments: Do not interpret comments, simply copy them as + plain-text. + :--interpolate: Use the globalization information to typeset + identifiers appearing in |Coq| escapings inside comments. + +**Language options** + + + Default behavior is to assume ASCII 7 bits input files. + + :-latin1, --latin1: Select ISO-8859-1 input files. It is equivalent to + --inputenc latin1 --charset iso-8859-1. + :-utf8, --utf8: Set --inputenc utf8x for |Latex| output and--charset + utf-8 for HTML output. Also use Unicode replacements for a couple of + standard plain ASCII notations such as → for ``->`` and ∀ for ``forall``. |Latex| + UTF-8 support can be found + at `<http://www.ctan.org/pkg/unicode>`_. For the interpretation of Unicode + characters by |Latex|, extra packages which coqdoc does not provide + by default might be required, such as textgreek for some Greek letters + or ``stmaryrd`` for some mathematical symbols. If a Unicode character is + missing an interpretation in the utf8x input encoding, add + ``\DeclareUnicodeCharacter{code}{LATEX-interpretation}``. Packages + and declarations can be added with option ``-p``. + :--inputenc string: Give a |Latex| input encoding, as an option to |Latex| + package ``inputenc``. + :--charset string: Specify the HTML character set, to be inserted in + the HTML header. + + + +The coqdoc |Latex| style file +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In case you choose to produce a document without the default |Latex| +preamble (by using option ``--no-preamble``), then you must insert into +your own preamble the command + +:: + + \usepackage{coqdoc} + +The package optionally takes the argument ``[color]`` to typeset +identifiers with colors (this requires the ``xcolor`` package). + +Then you may alter the rendering of the document by redefining some +macros: + +:coqdockw, coqdocid, …: The one-argument macros for typesetting + keywords and identifiers. Defaults are sans-serif for keywords and + italic for identifiers.For example, if you would like a slanted font + for keywords, you may insert + + :: + + \renewcommand{\coqdockw}[1]{\textsl{#1}} + + + anywhere between ``\usepackage{coqdoc}`` and ``\begin{document}``. + + +:coqdocmodule: + One-argument macro for typesetting the title of a ``.v`` + file. Default is + + :: + + \newcommand{\coqdocmodule}[1]{\section*{Module #1}} + + and you may redefine it using ``\renewcommand``. + +Embedded Coq phrases inside |Latex| documents +--------------------------------------------- + +When writing a documentation about a proof development, one may want +to insert |Coq| phrases inside a |Latex| document, possibly together +with the corresponding answers of the system. We provide a mechanical +way to process such |Coq| phrases embedded in |Latex| files: the ``coq-tex`` +filter. This filter extracts |Coq| phrases embedded in |Latex| files, +evaluates them, and insert the outcome of the evaluation after each +phrase. + +Starting with a file ``file.tex`` containing |Coq| phrases, the ``coq-tex`` +filter produces a file named ``file.v.tex`` with the Coq outcome. + +There are options to produce the |Coq| parts in smaller font, italic, +between horizontal rules, etc. See the man page of ``coq-tex`` for more +details. + +|Coq| and GNU Emacs +----------------------- + + +The |Coq| Emacs mode +~~~~~~~~~~~~~~~~~~~~~~~~~ + +|Coq| comes with a Major mode for GNU Emacs, ``gallina.el``. This mode +provides syntax highlighting and also a rudimentary indentation +facility in the style of the ``Caml`` GNU Emacs mode. + +Add the following lines to your ``.emacs`` file: + +:: + + (setq auto-mode-alist (cons '("\\.v$" . coq-mode) auto-mode-alist)) + (autoload 'coq-mode "gallina" "Major mode for editing Coq vernacular." t) + + +The |Coq| major mode is triggered by visiting a file with extension ``.v``, +or manually with the command ``M-x coq-mode``. It gives you the correct +syntax table for the |Coq| language, and also a rudimentary indentation +facility: + + ++ pressing ``Tab`` at the beginning of a line indents the line like the + line above; ++ extra tabulations increase the indentation level (by 2 spaces by default); ++ ``M-Tab`` decreases the indentation level. + + +An inferior mode to run |Coq| under Emacs, by Marco Maggesi, is also +included in the distribution, in file ``inferior-coq.el``. Instructions to +use it are contained in this file. + + +Proof-General +~~~~~~~~~~~~~ + +Proof-General is a generic interface for proof assistants based on +Emacs. The main idea is that the |Coq| commands you are editing are sent +to a |Coq| toplevel running behind Emacs and the answers of the system +automatically inserted into other Emacs buffers. Thus you don’t need +to copy-paste the |Coq| material from your files to the |Coq| toplevel or +conversely from the |Coq| toplevel to some files. + +Proof-General is developed and distributed independently of the system +|Coq|. It is freely available at `<https://proofgeneral.github.io/>`_. + + +Module specification +-------------------- + +Given a |Coq| vernacular file, the gallina filter extracts its +specification (inductive types declarations, definitions, type of +lemmas and theorems), removing the proofs parts of the file. The |Coq| +file ``file.v`` gives birth to the specification file ``file.g`` (where +the suffix ``.g`` stands for |Gallina|). + +See the man page of ``gallina`` for more details and options. + + +Man pages +--------- + +There are man pages for the commands ``coqdep``, ``gallina`` and ``coq-tex``. Man +pages are installed at installation time (see installation +instructions in file ``INSTALL``, step 6). diff --git a/doc/sphinx/proof-engine/detailed-tactic-examples.rst b/doc/sphinx/proof-engine/detailed-tactic-examples.rst index 932f967881..84810ddba5 100644 --- a/doc/sphinx/proof-engine/detailed-tactic-examples.rst +++ b/doc/sphinx/proof-engine/detailed-tactic-examples.rst @@ -6,6 +6,8 @@ Detailed examples of tactics This chapter presents detailed examples of certain tactics, to illustrate their behavior. +.. _dependent-induction: + dependent induction ------------------- @@ -316,7 +318,7 @@ explicit proof terms: This concludes our example. -See also: The ``induction`` :ref:`TODO-9-induction`, ``case`` :ref:`TODO-9-induction` and ``inversion`` :ref:`TODO-8.14-inversion` tactics. +See also: The :tacn:`induction`, :tacn:`case`, and :tacn:`inversion` tactics. autorewrite @@ -403,6 +405,8 @@ Example 2: Mac Carthy function autorewrite with base1 using reflexivity || simpl. +.. _quote: + quote ----- @@ -544,8 +548,7 @@ Combining variables and constants ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ One can have both variables and constants in abstracts terms; for -example, this is the case for the ``ring`` tactic -:ref:`TODO-25-ringandfieldtacticfamilies`. Then one must provide to +example, this is the case for the :tacn:`ring` tactic. Then one must provide to ``quote`` a list of *constructors of constants*. For example, if the list is ``[O S]`` then closed natural numbers will be considered as constants and other terms as variables. @@ -606,7 +609,7 @@ don’t expect miracles from it! See also: comments of source file ``plugins/quote/quote.ml`` -See also: the ``ring`` tactic :ref:`TODO-25-ringandfieldtacticfamilies` +See also: the :tacn:`ring` tactic. Using the tactical language @@ -733,7 +736,7 @@ and this length is decremented for each rotation down to, but not including, 1 because for a list of length ``n``, we can make exactly ``n−1`` rotations to generate at most ``n`` distinct lists. Here, it must be noticed that we use the natural numbers of Coq for the -rotation counter. On Figure :ref:`TODO-9.1-tactic-language`, we can +rotation counter. In :ref:`ltac-syntax`, we can see that it is possible to use usual natural numbers but they are only used as arguments for primitive tactics and they cannot be handled, in particular, we cannot make computations with them. So, a natural @@ -830,7 +833,7 @@ The pattern matching on goals allows a complete and so a powerful backtracking when returning tactic values. An interesting application is the problem of deciding intuitionistic propositional logic. Considering the contraction-free sequent calculi LJT* of Roy Dyckhoff -:ref:`TODO-56-biblio`, it is quite natural to code such a tactic +:cite:`Dyc92`, it is quite natural to code such a tactic using the tactic language as shown on figures: :ref:`Deciding intuitionistic propositions (1) <decidingintuitionistic1>` and :ref:`Deciding intuitionistic propositions (2) @@ -868,7 +871,7 @@ Deciding type isomorphisms A more tricky problem is to decide equalities between types and modulo isomorphisms. Here, we choose to use the isomorphisms of the simply typed λ-calculus with Cartesian product and unit type (see, for -example, [:ref:`TODO-45`]). The axioms of this λ-calculus are given below. +example, :cite:`RC95`). The axioms of this λ-calculus are given below. .. coqtop:: in reset diff --git a/doc/sphinx/proof-engine/ltac.rst b/doc/sphinx/proof-engine/ltac.rst new file mode 100644 index 0000000000..009758319b --- /dev/null +++ b/doc/sphinx/proof-engine/ltac.rst @@ -0,0 +1,1300 @@ +.. include:: ../preamble.rst +.. include:: ../replaces.rst + +.. _ltac: + +The tactic language +=================== + +This chapter gives a compact documentation of |Ltac|, the tactic language +available in |Coq|. We start by giving the syntax, and next, we present the +informal semantics. If you want to know more regarding this language and +especially about its foundations, you can refer to :cite:`Del00`. Chapter +:ref:`detailedexamplesoftactics` is devoted to giving examples of use of this +language on small but also with non-trivial problems. + +.. _ltac-syntax: + +Syntax +------ + +The syntax of the tactic language is given below. See Chapter +:ref:`gallinaspecificationlanguage` for a description of the BNF metasyntax used +in these grammar rules. Various already defined entries will be used in this +chapter: entries :token:`natural`, :token:`integer`, :token:`ident`, +:token:`qualid`, :token:`term`, :token:`cpattern` and :token:`atomic_tactic` +represent respectively the natural and integer numbers, the authorized +identificators and qualified names, Coq terms and patterns and all the atomic +tactics described in Chapter :ref:`tactics`. The syntax of :token:`cpattern` is +the same as that of terms, but it is extended with pattern matching +metavariables. In :token:`cpattern`, a pattern-matching metavariable is +represented with the syntax :g:`?id` where :g:`id` is an :token:`ident`. The +notation :g:`_` can also be used to denote metavariable whose instance is +irrelevant. In the notation :g:`?id`, the identifier allows us to keep +instantiations and to make constraints whereas :g:`_` shows that we are not +interested in what will be matched. On the right hand side of pattern-matching +clauses, the named metavariable are used without the question mark prefix. There +is also a special notation for second-order pattern-matching problems: in an +applicative pattern of the form :g:`@?id id1 … idn`, the variable id matches any +complex expression with (possible) dependencies in the variables :g:`id1 … idn` +and returns a functional term of the form :g:`fun id1 … idn => term`. + +The main entry of the grammar is :n:`@expr`. This language is used in proof +mode but it can also be used in toplevel definitions as shown below. + +.. note:: + + - The infix tacticals “… \|\| …”, “… + …”, and “… ; …” are associative. + + - In :token:`tacarg`, there is an overlap between qualid as a direct tactic + argument and :token:`qualid` as a particular case of term. The resolution is + done by first looking for a reference of the tactic language and if + it fails, for a reference to a term. To force the resolution as a + reference of the tactic language, use the form :g:`ltac:(@qualid)`. To + force the resolution as a reference to a term, use the syntax + :g:`(@qualid)`. + + - As shown by the figure, tactical ``\|\|`` binds more than the prefix + tacticals try, repeat, do and abstract which themselves bind more + than the postfix tactical “… ;[ … ]” which binds more than “… ; …”. + + For instance + + .. coqtop:: in + + try repeat tac1 || tac2; tac3; [tac31 | ... | tac3n]; tac4. + + is understood as + + .. coqtop:: in + + try (repeat (tac1 || tac2)); + ((tac3; [tac31 | ... | tac3n]); tac4). + +.. productionlist:: coq + expr : `expr` ; `expr` + : | [> `expr` | ... | `expr` ] + : | `expr` ; [ `expr` | ... | `expr` ] + : | `tacexpr3` + tacexpr3 : do (`natural` | `ident`) tacexpr3 + : | progress `tacexpr3` + : | repeat `tacexpr3` + : | try `tacexpr3` + : | once `tacexpr3` + : | exactly_once `tacexpr3` + : | timeout (`natural` | `ident`) `tacexpr3` + : | time [`string`] `tacexpr3` + : | only `selector`: `tacexpr3` + : | `tacexpr2` + tacexpr2 : `tacexpr1` || `tacexpr3` + : | `tacexpr1` + `tacexpr3` + : | tryif `tacexpr1` then `tacexpr1` else `tacexpr1` + : | `tacexpr1` + tacexpr1 : fun `name` ... `name` => `atom` + : | let [rec] `let_clause` with ... with `let_clause` in `atom` + : | match goal with `context_rule` | ... | `context_rule` end + : | match reverse goal with `context_rule` | ... | `context_rule` end + : | match `expr` with `match_rule` | ... | `match_rule` end + : | lazymatch goal with `context_rule` | ... | `context_rule` end + : | lazymatch reverse goal with `context_rule` | ... | `context_rule` end + : | lazymatch `expr` with `match_rule` | ... | `match_rule` end + : | multimatch goal with `context_rule` | ... | `context_rule` end + : | multimatch reverse goal with `context_rule` | ... | `context_rule` end + : | multimatch `expr` with `match_rule` | ... | `match_rule` end + : | abstract `atom` + : | abstract `atom` using `ident` + : | first [ `expr` | ... | `expr` ] + : | solve [ `expr` | ... | `expr` ] + : | idtac [ `message_token` ... `message_token`] + : | fail [`natural`] [`message_token` ... `message_token`] + : | fresh | fresh `string` | fresh `qualid` + : | context `ident` [`term`] + : | eval `redexpr` in `term` + : | type of `term` + : | constr : `term` + : | uconstr : `term` + : | type_term `term` + : | numgoals + : | guard `test` + : | assert_fails `tacexpr3` + : | assert_suceeds `tacexpr3` + : | `atomic_tactic` + : | `qualid` `tacarg` ... `tacarg` + : | `atom` + atom : `qualid` + : | () + : | `integer` + : | ( `expr` ) + message_token : `string` | `ident` | `integer` + tacarg : `qualid` + : | () + : | ltac : `atom` + : | `term` + let_clause : `ident` [`name` ... `name`] := `expr` + context_rule : `context_hyp`, ..., `context_hyp` |- `cpattern` => `expr` + : | `cpattern` => `expr` + : | |- `cpattern` => `expr` + : | _ => `expr` + context_hyp : `name` : `cpattern` + : | `name` := `cpattern` [: `cpattern`] + match_rule : `cpattern` => `expr` + : | context [ident] [ `cpattern` ] => `expr` + : | _ => `expr` + test : `integer` = `integer` + : | `integer` (< | <= | > | >=) `integer` + selector : [`ident`] + : | `integer` + : (`integer` | `integer` - `integer`), ..., (`integer` | `integer` - `integer`) + toplevel_selector : `selector` + : | `all` + : | `par` + +.. productionlist:: coq + top : [Local] Ltac `ltac_def` with ... with `ltac_def` + ltac_def : `ident` [`ident` ... `ident`] := `expr` + : | `qualid` [`ident` ... `ident`] ::= `expr` + +.. _ltac-semantics: + +Semantics +--------- + +Tactic expressions can only be applied in the context of a proof. The +evaluation yields either a term, an integer or a tactic. Intermediary +results can be terms or integers but the final result must be a tactic +which is then applied to the focused goals. + +There is a special case for ``match goal`` expressions of which the clauses +evaluate to tactics. Such expressions can only be used as end result of +a tactic expression (never as argument of a non recursive local +definition or of an application). + +The rest of this section explains the semantics of every construction of +|Ltac|. + +Sequence +~~~~~~~~ + +A sequence is an expression of the following form: + +.. tacn:: @expr ; @expr + :name: ; + + The expression :n:`@expr__1` is evaluated to :n:`v__1`, which must be + a tactic value. The tactic :n:`v__1` is applied to the current goal, + possibly producing more goals. Then :n:`@expr__2` is evaluated to + produce :n:`v__2`, which must be a tactic value. The tactic + :n:`v__2` is applied to all the goals produced by the prior + application. Sequence is associative. + +Local application of tactics +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Different tactics can be applied to the different goals using the +following form: + +.. tacn:: [> {*| @expr }] + :name: [> ... | ... | ... ] (dispatch) + + The expressions :n:`@expr__i` are evaluated to :n:`v__i`, for + i=0,...,n and all have to be tactics. The :n:`v__i` is applied to the + i-th goal, for =1,...,n. It fails if the number of focused goals is not + exactly n. + + .. note:: + + If no tactic is given for the i-th goal, it behaves as if the tactic idtac + were given. For instance, ``[> | auto]`` is a shortcut for ``[> idtac | auto + ]``. + + .. tacv:: [> {*| @expr} | @expr .. | {*| @expr}] + + In this variant, token:`expr` is used for each goal coming after those + covered by the first list of :n:`@expr` but before those coevered by the + last list of :n:`@expr`. + + .. tacv:: [> {*| @expr} | .. | {*| @expr}] + + In this variant, idtac is used for the goals not covered by the two lists of + :n:`@expr`. + + .. tacv:: [> @expr .. ] + + In this variant, the tactic :n:`@expr` is applied independently to each of + the goals, rather than globally. In particular, if there are no goal, the + tactic is not run at all. A tactic which expects multiple goals, such as + ``swap``, would act as if a single goal is focused. + + .. tacv:: expr ; [{*| @expr}] + + This variant of local tactic application is paired with a sequence. In this + variant, there must be as many :n:`@expr` in the list as goals generated + by the application of the first :n:`@expr` to each of the individual goals + independently. All the above variants work in this form too. + Formally, :n:`@expr ; [ ... ]` is equivalent to :n:`[> @expr ; [> ... ] .. ]`. + +.. _goal-selectors: + +Goal selectors +~~~~~~~~~~~~~~ + +We can restrict the application of a tactic to a subset of the currently +focused goals with: + +.. tacn:: @toplevel_selector : @expr + :name: ... : ... (goal selector) + + We can also use selectors as a tactical, which allows to use them nested + in a tactic expression, by using the keyword ``only``: + + .. tacv:: only selector : expr + + When selecting several goals, the tactic expr is applied globally to all + selected goals. + + .. tacv:: [@ident] : @expr + + In this variant, :n:`@expr` is applied locally to a goal previously named + by the user (see :ref:`existential-variables`). + + .. tacv:: @num : @expr + + In this variant, :n:`@expr` is applied locally to the :token:`num`-th goal. + + .. tacv:: {+, @num-@num} : @expr + + In this variant, :n:`@expr` is applied globally to the subset of goals + described by the given ranges. You can write a single ``n`` as a shortcut + for ``n-n`` when specifying multiple ranges. + + .. tacv:: all: @expr + + In this variant, :n:`@expr` is applied to all focused goals. ``all:`` can only + be used at the toplevel of a tactic expression. + + .. tacv:: par: @expr + + In this variant, :n:`@expr` is applied to all focused goals in parallel. + The number of workers can be controlled via the command line option + ``-async-proofs-tac-j`` taking as argument the desired number of workers. + Limitations: ``par:`` only works on goals containing no existential + variables and :n:`@expr` must either solve the goal completely or do + nothing (i.e. it cannot make some progress). ``par:`` can only be used at + the toplevel of a tactic expression. + + .. exn:: No such goal + :name: No such goal (goal selector) + + .. TODO change error message index entry + +For loop +~~~~~~~~ + +There is a for loop that repeats a tactic :token:`num` times: + +.. tacn:: do @num @expr + :name: do + + :n:`@expr` is evaluated to ``v`` which must be a tactic value. This tactic + value ``v`` is applied :token:`num` times. Supposing :token:`num` > 1, after the + first application of ``v``, ``v`` is applied, at least once, to the generated + subgoals and so on. It fails if the application of ``v`` fails before the num + applications have been completed. + +Repeat loop +~~~~~~~~~~~ + +We have a repeat loop with: + +.. tacn:: repeat @expr + :name: repeat + + :n:`@expr` is evaluated to ``v``. If ``v`` denotes a tactic, this tactic is + applied to each focused goal independently. If the application succeeds, the + tactic is applied recursively to all the generated subgoals until it eventually + fails. The recursion stops in a subgoal when the tactic has failed *to make + progress*. The tactic :n:`repeat @expr` itself never fails. + +Error catching +~~~~~~~~~~~~~~ + +We can catch the tactic errors with: + +.. tacn:: try @expr + :name: try + + :n:`@expr` is evaluated to ``v`` which must be a tactic value. The tactic + value ``v`` is applied to each focused goal independently. If the application of + ``v`` fails in a goal, it catches the error and leaves the goal unchanged. If the + level of the exception is positive, then the exception is re-raised with its + level decremented. + +Detecting progress +~~~~~~~~~~~~~~~~~~ + +We can check if a tactic made progress with: + +.. tacn:: progress expr + :name: progress + + :n:`@expr` is evaluated to v which must be a tactic value. The tactic value ``v`` + is applied to each focued subgoal independently. If the application of ``v`` + to one of the focused subgoal produced subgoals equal to the initial + goals (up to syntactical equality), then an error of level 0 is raised. + + .. exn:: Failed to progress + +Backtracking branching +~~~~~~~~~~~~~~~~~~~~~~ + +We can branch with the following structure: + +.. tacn:: @expr__1 + @expr__2 + :name: + (backtracking branching) + + :n:`@expr__1` and :n:`@expr__2` are evaluated respectively to :n:`v__1` and + :n:`v__2` which must be tactic values. The tactic value :n:`v__1` is applied to + each focused goal independently and if it fails or a later tactic fails, then + the proof backtracks to the current goal and :n:`v__2` is applied. + + Tactics can be seen as having several successes. When a tactic fails it + asks for more successes of the prior tactics. + :n:`@expr__1 + @expr__2` has all the successes of :n:`v__1` followed by all the + successes of :n:`v__2`. Algebraically, + :n:`(@expr__1 + @expr__2); @expr__3 = (@expr__1; @expr__3) + (@expr__2; @expr__3)`. + + Branching is left-associative. + +First tactic to work +~~~~~~~~~~~~~~~~~~~~ + +Backtracking branching may be too expensive. In this case we may +restrict to a local, left biased, branching and consider the first +tactic to work (i.e. which does not fail) among a panel of tactics: + +.. tacn:: first [{*| @expr}] + :name: first + + The :n:`@expr__i` are evaluated to :n:`v__i` and :n:`v__i` must be + tactic values, for i=1,...,n. Supposing n>1, it applies, in each focused + goal independently, :n:`v__1`, if it works, it stops otherwise it + tries to apply :n:`v__2` and so on. It fails when there is no + applicable tactic. In other words, + :n:`first [:@expr__1 | ... | @expr__n]` behaves, in each goal, as the the first + :n:`v__i` to have *at least* one success. + + .. exn:: Error message: No applicable tactic + + .. tacv:: first @expr + + This is an |Ltac| alias that gives a primitive access to the first + tactical as a |Ltac| definition without going through a parsing rule. It + expects to be given a list of tactics through a ``Tactic Notation``, + allowing to write notations of the following form: + + .. example:: + + .. coqtop:: in + + Tactic Notation "foo" tactic_list(tacs) := first tacs. + +Left-biased branching +~~~~~~~~~~~~~~~~~~~~~ + +Yet another way of branching without backtracking is the following +structure: + +.. tacn:: @expr__1 || @expr__2 + :name: || (left-biased branching) + + :n:`@expr__1` and :n:`@expr__2` are evaluated respectively to :n:`v__1` and + :n:`v__2` which must be tactic values. The tactic value :n:`v__1` is + applied in each subgoal independently and if it fails *to progress* then + :n:`v__2` is applied. :n:`@expr__1 || @expr__2` is + equivalent to :n:`first [ progress @expr__1 | @expr__2 ]` (except that + if it fails, it fails like :n:`v__2`). Branching is left-associative. + +Generalized biased branching +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The tactic + +.. tacn:: tryif @expr__1 then @expr__2 else @expr__3 + :name: tryif + + is a generalization of the biased-branching tactics above. The + expression :n:`@expr__1` is evaluated to :n:`v__1`, which is then + applied to each subgoal independently. For each goal where :n:`v__1` + succeeds at least once, :n:`@expr__2` is evaluated to :n:`v__2` which + is then applied collectively to the generated subgoals. The :n:`v__2` + tactic can trigger backtracking points in :n:`v__1`: where :n:`v__1` + succeeds at least once, + :n:`tryif @expr__1 then @expr__2 else @expr__3` is equivalent to + :n:`v__1; v__2`. In each of the goals where :n:`v__1` does not succeed at least + once, :n:`@expr__3` is evaluated in :n:`v__3` which is is then applied to the + goal. + +Soft cut +~~~~~~~~ + +Another way of restricting backtracking is to restrict a tactic to a +single success *a posteriori*: + +.. tacn:: once @expr + :name: once + + :n:`@expr` is evaluated to ``v`` which must be a tactic value. The tactic value + ``v`` is applied but only its first success is used. If ``v`` fails, + :n:`once @expr` fails like ``v``. If ``v`` has a least one success, + :n:`once @expr` succeeds once, but cannot produce more successes. + +Checking the successes +~~~~~~~~~~~~~~~~~~~~~~ + +Coq provides an experimental way to check that a tactic has *exactly +one* success: + +.. tacn:: exactly_once @expr + :name: exactly_once + + :n:`@expr` is evaluated to ``v`` which must be a tactic value. The tactic value + ``v`` is applied if it has at most one success. If ``v`` fails, + :n:`exactly_once @expr` fails like ``v``. If ``v`` has a exactly one success, + :n:`exactly_once @expr` succeeds like ``v``. If ``v`` has two or more + successes, exactly_once expr fails. + + .. warning:: + + The experimental status of this tactic pertains to the fact if ``v`` + performs side effects, they may occur in a unpredictable way. Indeed, + normally ``v`` would only be executed up to the first success until + backtracking is needed, however exactly_once needs to look ahead to see + whether a second success exists, and may run further effects + immediately. + + .. exn:: This tactic has more than one success + +Checking the failure +~~~~~~~~~~~~~~~~~~~~ + +Coq provides a derived tactic to check that a tactic *fails*: + +.. tacn:: assert_fails @expr + :name: assert_fails + + This behaves like :n:`tryif @expr then fail 0 tac "succeeds" else idtac`. + +Checking the success +~~~~~~~~~~~~~~~~~~~~ + +Coq provides a derived tactic to check that a tactic has *at least one* +success: + +.. tacn:: assert_succeeds @expr + :name: assert_suceeds + + This behaves like + :n:`tryif (assert_fails tac) then fail 0 tac "fails" else idtac`. + +Solving +~~~~~~~ + +We may consider the first to solve (i.e. which generates no subgoal) +among a panel of tactics: + +.. tacn:: solve [{*| @expr}] + :name: solve + + The :n:`@expr__i` are evaluated to :n:`v__i` and :n:`v__i` must be + tactic values, for i=1,...,n. Supposing n>1, it applies :n:`v__1` to + each goal independently, if it doesn’t solve the goal then it tries to + apply :n:`v__2` and so on. It fails if there is no solving tactic. + + .. exn:: Cannot solve the goal + + .. tacv:: solve @expr + + This is an |Ltac| alias that gives a primitive access to the :n:`solve:` + tactical. See the :n:`first` tactical for more information. + +Identity +~~~~~~~~ + +The constant :n:`idtac` is the identity tactic: it leaves any goal unchanged but +it appears in the proof script. + +.. tacn:: idtac {* message_token} + :name: idtac + + This prints the given tokens. Strings and integers are printed + literally. If a (term) variable is given, its contents are printed. + +Failing +~~~~~~~ + +.. tacn:: fail + :name: fail + + This is the always-failing tactic: it does not solve any + goal. It is useful for defining other tacticals since it can be caught by + :tacn:`try`, :tacn:`repeat`, :tacn:`match goal`, or the branching tacticals. The + :tacn:`fail` tactic will, however, succeed if all the goals have already been + solved. + + .. tacv:: fail @natural + + The number is the failure level. If no level is specified, it defaults to 0. + The level is used by :tacn:`try`, :tacn:`repeat`, :tacn:`match goal` and the branching + tacticals. If 0, it makes :tacn:`match goal` considering the next clause + (backtracking). If non zero, the current :tacn:`match goal` block, :tacn:`try`, + :tacn:`repeat`, or branching command is aborted and the level is decremented. In + the case of :n:`+`, a non-zero level skips the first backtrack point, even if + the call to :n:`fail @natural` is not enclosed in a :n:`+` command, + respecting the algebraic identity. + + .. tacv:: fail {* message_token} + + The given tokens are used for printing the failure message. + + .. tacv:: fail @natural {* message_token} + + This is a combination of the previous variants. + + .. tacv:: gfail + :name: gfail + + This variant fails even if there are no goals left. + + .. tacv:: gfail {* message_token} + + .. tacv:: gfail @natural {* message_token} + + These variants fail with an error message or an error level even if + there are no goals left. Be careful however if Coq terms have to be + printed as part of the failure: term construction always forces the + tactic into the goals, meaning that if there are no goals when it is + evaluated, a tactic call like :n:`let x:=H in fail 0 x` will succeed. + + .. exn:: Tactic Failure message (level @natural). + +Timeout +~~~~~~~ + +We can force a tactic to stop if it has not finished after a certain +amount of time: + +.. tacn:: timeout @num @expr + :name: timeout + + :n:`@expr` is evaluated to ``v`` which must be a tactic value. The tactic value + ``v`` is applied normally, except that it is interrupted after :n:`@num` seconds + if it is still running. In this case the outcome is a failure. + + .. warning:: + + For the moment, timeout is based on elapsed time in seconds, + which is very machine-dependent: a script that works on a quick machine + may fail on a slow one. The converse is even possible if you combine a + timeout with some other tacticals. This tactical is hence proposed only + for convenience during debug or other development phases, we strongly + advise you to not leave any timeout in final scripts. Note also that + this tactical isn’t available on the native Windows port of Coq. + +Timing a tactic +~~~~~~~~~~~~~~~ + +A tactic execution can be timed: + +.. tacn:: time @string @expr + :name: time + + evaluates :n:`@expr` and displays the time the tactic expression ran, whether it + fails or successes. In case of several successes, the time for each successive + runs is displayed. Time is in seconds and is machine-dependent. The :n:`@string` + argument is optional. When provided, it is used to identify this particular + occurrence of time. + +Timing a tactic that evaluates to a term +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Tactic expressions that produce terms can be timed with the experimental +tactic + +.. tacn:: time_constr expr + :name: time_constr + + which evaluates :n:`@expr ()` and displays the time the tactic expression + evaluated, assuming successful evaluation. Time is in seconds and is + machine-dependent. + + This tactic currently does not support nesting, and will report times + based on the innermost execution. This is due to the fact that it is + implemented using the tactics + + .. tacn:: restart_timer @string + :name: restart_timer + + and + + .. tacn:: finish_timing {? @string} @string + :name: finish_timing + + which (re)set and display an optionally named timer, respectively. The + parenthesized string argument to :n:`finish_timing` is also optional, and + determines the label associated with the timer for printing. + + By copying the definition of :n:`time_constr` from the standard library, + users can achive support for a fixed pattern of nesting by passing + different :n:`@string` parameters to :n:`restart_timer` and :n:`finish_timing` + at each level of nesting. + + .. example:: + + .. coqtop:: all + + Ltac time_constr1 tac := + let eval_early := match goal with _ => restart_timer "(depth 1)" end in + let ret := tac () in + let eval_early := match goal with _ => finish_timing ( "Tactic evaluation" ) "(depth 1)" end in + ret. + + Goal True. + let v := time_constr + ltac:(fun _ => + let x := time_constr1 ltac:(fun _ => constr:(10 * 10)) in + let y := time_constr1 ltac:(fun _ => eval compute in x) in + y) in + pose v. + Abort. + +Local definitions +~~~~~~~~~~~~~~~~~ + +Local definitions can be done as follows: + +.. tacn:: let @ident__1 := @expr__1 {* with @ident__i := @expr__i} in @expr + + each :n:`@expr__i` is evaluated to :n:`v__i`, then, :n:`@expr` is evaluated + by substituting :n:`v__i` to each occurrence of :n:`@ident__i`, for + i=1,...,n. There is no dependencies between the :n:`@expr__i` and the + :n:`@ident__i`. + + Local definitions can be recursive by using :n:`let rec` instead of :n:`let`. + In this latter case, the definitions are evaluated lazily so that the rec + keyword can be used also in non recursive cases so as to avoid the eager + evaluation of local definitions. + + .. but rec changes the binding!! + +Application +~~~~~~~~~~~ + +An application is an expression of the following form: + +.. tacn:: @qualid {+ @tacarg} + + The reference :n:`@qualid` must be bound to some defined tactic definition + expecting at least as many arguments as the provided :n:`tacarg`. The + expressions :n:`@expr__i` are evaluated to :n:`v__i`, for i=1,...,n. + + .. what expressions ?? + +Function construction +~~~~~~~~~~~~~~~~~~~~~ + +A parameterized tactic can be built anonymously (without resorting to +local definitions) with: + +.. tacn:: fun {+ @ident} => @expr + + Indeed, local definitions of functions are a syntactic sugar for binding + a :n:`fun` tactic to an identifier. + +Pattern matching on terms +~~~~~~~~~~~~~~~~~~~~~~~~~ + +We can carry out pattern matching on terms with: + +.. tacn:: match @expr with {+| @cpattern__i => @expr__i} end + + The expression :n:`@expr` is evaluated and should yield a term which is + matched against :n:`cpattern__1`. The matching is non-linear: if a + metavariable occurs more than once, it should match the same expression + every time. It is first-order except on the variables of the form :n:`@?id` + that occur in head position of an application. For these variables, the + matching is second-order and returns a functional term. + + Alternatively, when a metavariable of the form :n:`?id` occurs under binders, + say :n:`x__1, …, x__n` and the expression matches, the + metavariable is instantiated by a term which can then be used in any + context which also binds the variables :n:`x__1, …, x__n` with + same types. This provides with a primitive form of matching under + context which does not require manipulating a functional term. + + If the matching with :n:`@cpattern__1` succeeds, then :n:`@expr__1` is + evaluated into some value by substituting the pattern matching + instantiations to the metavariables. If :n:`@expr__1` evaluates to a + tactic and the match expression is in position to be applied to a goal + (e.g. it is not bound to a variable by a :n:`let in`), then this tactic is + applied. If the tactic succeeds, the list of resulting subgoals is the + result of the match expression. If :n:`@expr__1` does not evaluate to a + tactic or if the match expression is not in position to be applied to a + goal, then the result of the evaluation of :n:`@expr__1` is the result + of the match expression. + + If the matching with :n:`@cpattern__1` fails, or if it succeeds but the + evaluation of :n:`@expr__1` fails, or if the evaluation of + :n:`@expr__1` succeeds but returns a tactic in execution position whose + execution fails, then :n:`cpattern__2` is used and so on. The pattern + :n:`_` matches any term and shunts all remaining patterns if any. If all + clauses fail (in particular, there is no pattern :n:`_`) then a + no-matching-clause error is raised. + + Failures in subsequent tactics do not cause backtracking to select new + branches or inside the right-hand side of the selected branch even if it + has backtracking points. + + .. exn:: No matching clauses for match + + No pattern can be used and, in particular, there is no :n:`_` pattern. + + .. exn:: Argument of match does not evaluate to a term + + This happens when :n:`@expr` does not denote a term. + + .. tacv:: multimatch @expr with {+| @cpattern__i => @expr__i} end + + Using multimatch instead of match will allow subsequent tactics to + backtrack into a right-hand side tactic which has backtracking points + left and trigger the selection of a new matching branch when all the + backtracking points of the right-hand side have been consumed. + + The syntax :n:`match …` is, in fact, a shorthand for :n:`once multimatch …`. + + .. tacv:: lazymatch @expr with {+| @cpattern__i => @expr__i} end + + Using lazymatch instead of match will perform the same pattern + matching procedure but will commit to the first matching branch + rather than trying a new matching if the right-hand side fails. If + the right-hand side of the selected branch is a tactic with + backtracking points, then subsequent failures cause this tactic to + backtrack. + + .. tacv:: context @ident [@cpattern] + + This special form of patterns matches any term with a subterm matching + cpattern. If there is a match, the optional :n:`@ident` is assigned the "matched + context", i.e. the initial term where the matched subterm is replaced by a + hole. The example below will show how to use such term contexts. + + If the evaluation of the right-hand-side of a valid match fails, the next + matching subterm is tried. If no further subterm matches, the next clause + is tried. Matching subterms are considered top-bottom and from left to + right (with respect to the raw printing obtained by setting option + :opt:`Printing All`). + + .. example:: + + .. coqtop:: all + + Ltac f x := + match x with + context f [S ?X] => + idtac X; (* To display the evaluation order *) + assert (p := eq_refl 1 : X=1); (* To filter the case X=1 *) + let x:= context f[O] in assert (x=O) (* To observe the context *) + end. + Goal True. + f (3+4). + +.. _ltac-match-goal: + +Pattern matching on goals +~~~~~~~~~~~~~~~~~~~~~~~~~ + +We can make pattern matching on goals using the following expression: + +.. we should provide the full grammar here + +.. tacn:: match goal with {+| {+ hyp} |- @cpattern => @expr } | _ => @expr end + + If each hypothesis pattern :n:`hyp`\ :sub:`1,i`, with i=1,...,m\ :sub:`1` is + matched (non-linear first-order unification) by an hypothesis of the + goal and if :n:`cpattern_1` is matched by the conclusion of the goal, + then :n:`@expr__1` is evaluated to :n:`v__1` by substituting the + pattern matching to the metavariables and the real hypothesis names + bound to the possible hypothesis names occurring in the hypothesis + patterns. If :n:`v__1` is a tactic value, then it is applied to the + goal. If this application fails, then another combination of hypotheses + is tried with the same proof context pattern. If there is no other + combination of hypotheses then the second proof context pattern is tried + and so on. If the next to last proof context pattern fails then + the last :n:`@expr` is evaluated to :n:`v` and :n:`v` is + applied. Note also that matching against subterms (using the :n:`context + @ident [ @cpattern ]`) is available and is also subject to yielding several + matchings. + + Failures in subsequent tactics do not cause backtracking to select new + branches or combinations of hypotheses, or inside the right-hand side of + the selected branch even if it has backtracking points. + + .. exn:: No matching clauses for match goal + + No clause succeeds, i.e. all matching patterns, if any, fail at the + application of the right-hand-side. + + .. note:: + + It is important to know that each hypothesis of the goal can be matched + by at most one hypothesis pattern. The order of matching is the + following: hypothesis patterns are examined from the right to the left + (i.e. hyp\ :sub:`i,m`\ :sub:`i`` before hyp\ :sub:`i,1`). For each + hypothesis pattern, the goal hypothesis are matched in order (fresher + hypothesis first), but it possible to reverse this order (older first) + with the :n:`match reverse goal with` variant. + + .. tacv:: multimatch goal with {+| {+ hyp} |- @cpattern => @expr } | _ => @expr end + + Using :n:`multimatch` instead of :n:`match` will allow subsequent tactics + to backtrack into a right-hand side tactic which has backtracking points + left and trigger the selection of a new matching branch or combination of + hypotheses when all the backtracking points of the right-hand side have + been consumed. + + The syntax :n:`match [reverse] goal …` is, in fact, a shorthand for + :n:`once multimatch [reverse] goal …`. + + .. tacv:: lazymatch goal with {+| {+ hyp} |- @cpattern => @expr } | _ => @expr end + + Using lazymatch instead of match will perform the same pattern matching + procedure but will commit to the first matching branch with the first + matching combination of hypotheses rather than trying a new matching if + the right-hand side fails. If the right-hand side of the selected branch + is a tactic with backtracking points, then subsequent failures cause + this tactic to backtrack. + +Filling a term context +~~~~~~~~~~~~~~~~~~~~~~ + +The following expression is not a tactic in the sense that it does not +produce subgoals but generates a term to be used in tactic expressions: + +.. tacn:: context @ident [@expr] + + :n:`@ident` must denote a context variable bound by a context pattern of a + match expression. This expression evaluates replaces the hole of the + value of :n:`@ident` by the value of :n:`@expr`. + + .. exn:: not a context variable + +Generating fresh hypothesis names +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Tactics sometimes have to generate new names for hypothesis. Letting the +system decide a name with the intro tactic is not so good since it is +very awkward to retrieve the name the system gave. The following +expression returns an identifier: + +.. tacn:: fresh {* component} + + It evaluates to an identifier unbound in the goal. This fresh identifier + is obtained by concatenating the value of the :n:`@component`s (each of them + is, either a :n:`@qualid` which has to refer to a (unqualified) name, or + directly a name denoted by a :n:`@string`). + + .. I don't understand this component thing. Couldn't we give the grammar? + + If the resulting name is already used, it is padded with a number so that it + becomes fresh. If no component is given, the name is a fresh derivative of + the name ``H``. + +Computing in a constr +~~~~~~~~~~~~~~~~~~~~~ + +Evaluation of a term can be performed with: + +.. tacn:: eval @redexpr in @term + + where :n:`@redexpr` is a reduction tactic among :tacn:`red`, :tacn:`hnf`, + :tacn:`compute`, :tacn:`simpl`, :tacn:`cbv`, :tacn:`lazy`, :tacn:`unfold`, + :tacn:`fold`, :tacn:`pattern`. + +Recovering the type of a term +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The following returns the type of term: + +.. tacn:: type of @term + +Manipulating untyped terms +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. tacn:: uconstr : @term + + The terms built in |Ltac| are well-typed by default. It may not be + appropriate for building large terms using a recursive |Ltac| function: the + term has to be entirely type checked at each step, resulting in potentially + very slow behavior. It is possible to build untyped terms using |Ltac| with + the :n:`uconstr : @term` syntax. + +.. tacn:: type_term @term + + An untyped term, in |Ltac|, can contain references to hypotheses or to + |Ltac| variables containing typed or untyped terms. An untyped term can be + type-checked using the function type_term whose argument is parsed as an + untyped term and returns a well-typed term which can be used in tactics. + +Untyped terms built using :n:`uconstr :` can also be used as arguments to the +:tacn:`refine` tactic. In that case the untyped term is type +checked against the conclusion of the goal, and the holes which are not solved +by the typing procedure are turned into new subgoals. + +Counting the goals +~~~~~~~~~~~~~~~~~~ + +.. tacn:: numgoals + + The number of goals under focus can be recovered using the :n:`numgoals` + function. Combined with the guard command below, it can be used to + branch over the number of goals produced by previous tactics. + + .. example:: + + .. coqtop:: in + + Ltac pr_numgoals := let n := numgoals in idtac "There are" n "goals". + + Goal True /\ True /\ True. + split;[|split]. + + .. coqtop:: all + + all:pr_numgoals. + +Testing boolean expressions +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. tacn:: guard @test + :name: guard + + The :tacn:`guard` tactic tests a boolean expression, and fails if the expression + evaluates to false. If the expression evaluates to true, it succeeds + without affecting the proof. + + The accepted tests are simple integer comparisons. + + .. example:: + + .. coqtop:: in + + Goal True /\ True /\ True. + split;[|split]. + + .. coqtop:: all + + all:let n:= numgoals in guard n<4. + Fail all:let n:= numgoals in guard n=2. + + .. exn:: Condition not satisfied + +Proving a subgoal as a separate lemma +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. tacn:: abstract @expr + :name: abstract + + From the outside, :n:`abstract @expr` is the same as :n:`solve @expr`. + Internally it saves an auxiliary lemma called ``ident_subproofn`` where + ``ident`` is the name of the current goal and ``n`` is chosen so that this is + a fresh name. Such an auxiliary lemma is inlined in the final proof term. + + This tactical is useful with tactics such as :tacn:`omega` or + :tacn:`discriminate` that generate huge proof terms. With that tool the user + can avoid the explosion at time of the Save command without having to cut + manually the proof in smaller lemmas. + + It may be useful to generate lemmas minimal w.r.t. the assumptions they + depend on. This can be obtained thanks to the option below. + + .. tacv:: abstract @expr using @ident + + Give explicitly the name of the auxiliary lemma. + + .. warning:: + + Use this feature at your own risk; explicitly named and reused subterms + don’t play well with asynchronous proofs. + + .. tacv:: transparent_abstract @expr + :name: transparent_abstract + + Save the subproof in a transparent lemma rather than an opaque one. + + .. warning:: + + Use this feature at your own risk; building computationally relevant + terms with tactics is fragile. + + .. tacv:: transparent_abstract @expr using @ident + + Give explicitly the name of the auxiliary transparent lemma. + + .. warning:: + + Use this feature at your own risk; building computationally relevant terms + with tactics is fragile, and explicitly named and reused subterms + don’t play well with asynchronous proofs. + + .. exn:: Proof is not complete + :name: Proof is not complete (abstract) + +Tactic toplevel definitions +--------------------------- + +Defining |Ltac| functions +~~~~~~~~~~~~~~~~~~~~~~~~~ + +Basically, |Ltac| toplevel definitions are made as follows: + +.. cmd:: Ltac @ident {* @ident} := @expr + + This defines a new |Ltac| function that can be used in any tactic + script or new |Ltac| toplevel definition. + + .. note:: + + The preceding definition can equivalently be written: + + :n:`Ltac @ident := fun {+ @ident} => @expr` + + Recursive and mutual recursive function definitions are also possible + with the syntax: + + .. cmdv:: Ltac @ident {* @ident} {* with @ident {* @ident}} := @expr + + It is also possible to *redefine* an existing user-defined tactic using the syntax: + + .. cmdv:: Ltac @qualid {* @ident} ::= @expr + + A previous definition of qualid must exist in the environment. The new + definition will always be used instead of the old one and it goes across + module boundaries. + + If preceded by the keyword Local the tactic definition will not be + exported outside the current module. + +Printing |Ltac| tactics +~~~~~~~~~~~~~~~~~~~~~~~ + +.. cmd:: Print Ltac @qualid. + + Defined |Ltac| functions can be displayed using this command. + +.. cmd:: Print Ltac Signatures + + This command displays a list of all user-defined tactics, with their arguments. + +Debugging |Ltac| tactics +------------------------ + +Info trace +~~~~~~~~~~ + +.. cmd:: Info @num @expr + + This command can be used to print the trace of the path eventually taken by an + |Ltac| script. That is, the list of executed tactics, discarding + all the branches which have failed. To that end the Info command can be + used with the following syntax. + + + The number :n:`@num` is the unfolding level of tactics in the trace. At level + 0, the trace contains a sequence of tactics in the actual script, at level 1, + the trace will be the concatenation of the traces of these tactics, etc… + + .. example:: + + .. coqtop:: in reset + + Ltac t x := exists x; reflexivity. + Goal exists n, n=0. + + .. coqtop:: all + + Info 0 t 1||t 0. + + .. coqtop:: in + + Undo. + + .. coqtop:: all + + Info 1 t 1||t 0. + + The trace produced by ``Info`` tries its best to be a reparsable + |Ltac| script, but this goal is not achievable in all generality. + So some of the output traces will contain oddities. + + As an additional help for debugging, the trace produced by ``Info`` contains + (in comments) the messages produced by the idtac + tacticals \ `4.2 <#ltac%3Aidtac>`__ at the right possition in the + script. In particular, the calls to idtac in branches which failed are + not printed. + + .. opt:: Info Level @num. + + This option is an alternative to the ``Info`` command. + + This will automatically print the same trace as :n:`Info @num` at each + tactic call. The unfolding level can be overridden by a call to the + ``Info`` command. + +Interactive debugger +~~~~~~~~~~~~~~~~~~~~ + +.. opt:: Ltac Debug + + This option governs the step-by-step debugger that comes with the |Ltac| interpreter + +When the debugger is activated, it stops at every step of the evaluation of +the current |Ltac| expression and it prints information on what it is doing. +The debugger stops, prompting for a command which can be one of the +following: + ++-----------------+-----------------------------------------------+ +| simple newline: | go to the next step | ++-----------------+-----------------------------------------------+ +| h: | get help | ++-----------------+-----------------------------------------------+ +| x: | exit current evaluation | ++-----------------+-----------------------------------------------+ +| s: | continue current evaluation without stopping | ++-----------------+-----------------------------------------------+ +| r n: | advance n steps further | ++-----------------+-----------------------------------------------+ +| r string: | advance up to the next call to “idtac string” | ++-----------------+-----------------------------------------------+ + +A non-interactive mode for the debugger is available via the option: + +.. opt:: Ltac Batch Debug + + This option has the effect of presenting a newline at every prompt, when + the debugger is on. The debug log thus created, which does not require + user input to generate when this option is set, can then be run through + external tools such as diff. + +Profiling |Ltac| tactics +~~~~~~~~~~~~~~~~~~~~~~~~ + +It is possible to measure the time spent in invocations of primitive +tactics as well as tactics defined in |Ltac| and their inner +invocations. The primary use is the development of complex tactics, +which can sometimes be so slow as to impede interactive usage. The +reasons for the performence degradation can be intricate, like a slowly +performing |Ltac| match or a sub-tactic whose performance only +degrades in certain situations. The profiler generates a call tree and +indicates the time spent in a tactic depending its calling context. Thus +it allows to locate the part of a tactic definition that contains the +performance bug. + +.. opt:: Ltac Profiling + + This option enables and disables the profiler. + +.. cmd:: Show Ltac Profile + + Prints the profile + + .. cmdv:: Show Ltac Profile @string + + Prints a profile for all tactics that start with :n:`@string`. Append a period + (.) to the string if you only want exactly that name. + +.. cmd:: Reset Ltac Profile + + Resets the profile, that is, deletes all accumulated information. + + .. warning:: + + Backtracking across a Reset Ltac Profile will not restore the information. + +.. coqtop:: reset in + + Require Import Coq.omega.Omega. + + Ltac mytauto := tauto. + Ltac tac := intros; repeat split; omega || mytauto. + + Notation max x y := (x + (y - x)) (only parsing). + + Goal forall x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z, + max x (max y z) = max (max x y) z /\ max x (max y z) = max (max x y) z + /\ (A /\ B /\ C /\ D /\ E /\ F /\ G /\ H /\ I /\ J /\ K /\ L /\ M /\ N /\ O /\ P /\ Q /\ R /\ S /\ T /\ U /\ V /\ W /\ X /\ Y /\ Z + -> Z /\ Y /\ X /\ W /\ V /\ U /\ T /\ S /\ R /\ Q /\ P /\ O /\ N /\ M /\ L /\ K /\ J /\ I /\ H /\ G /\ F /\ E /\ D /\ C /\ B /\ A). + Proof. + +.. coqtop:: all + + Set Ltac Profiling. + tac. + Show Ltac Profile. + Show Ltac Profile "omega". + +.. coqtop:: in + + Abort. + Unset Ltac Profiling. + +.. tacn:: start ltac profiling + :name: start ltac profiling + + This tactic behaves like :tacn:`idtac` but enables the profiler. + +.. tacn:: stop ltac profiling + :name: stop ltac profiling + + Similarly to :tacn:`start ltac profiling`, this tactic behaves like + :tacn:`idtac`. Together, they allow you to exclude parts of a proof script + from profiling. + +.. tacn:: reset ltac profile + :name: reset ltac profile + + This tactic behaves like the corresponding vernacular command + and allow displaying and resetting the profile from tactic scripts for + benchmarking purposes. + +.. tacn:: show ltac profile + :name: show ltac profile + + This tactic behaves like the corresponding vernacular command + and allow displaying and resetting the profile from tactic scripts for + benchmarking purposes. + +.. tacn:: show ltac profile @string + :name: show ltac profile + + This tactic behaves like the corresponding vernacular command + and allow displaying and resetting the profile from tactic scripts for + benchmarking purposes. + +You can also pass the ``-profile-ltac`` command line option to ``coqc``, which +performs a ``Set Ltac Profiling`` at the beginning of each document, and a +``Show Ltac Profile`` at the end. + +.. warning:: + + Note that the profiler currently does not handle backtracking into + multi-success tactics, and issues a warning to this effect in many cases + when such backtracking occurs. + +Run-time optimization tactic +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. tacn:: optimize_heap + :name: optimize_heap + +This tactic behaves like :n:`idtac`, except that running it compacts the +heap in the OCaml run-time system. It is analogous to the Vernacular +command :cmd:`Optimize Heap`. diff --git a/doc/sphinx/proof-engine/proof-handling.rst b/doc/sphinx/proof-engine/proof-handling.rst new file mode 100644 index 0000000000..86c94bab36 --- /dev/null +++ b/doc/sphinx/proof-engine/proof-handling.rst @@ -0,0 +1,600 @@ +.. include:: ../replaces.rst +.. _proofhandling: + +------------------- + Proof handling +------------------- + +In |Coq|’s proof editing mode all top-level commands documented in +Chapter :ref:`vernacularcommands` remain available and the user has access to specialized +commands dealing with proof development pragmas documented in this +section. He can also use some other specialized commands called +*tactics*. They are the very tools allowing the user to deal with +logical reasoning. They are documented in Chapter :ref:`tactics`. +When switching in editing proof mode, the prompt ``Coq <`` is changed into +``ident <`` where ``ident`` is the declared name of the theorem currently +edited. + +At each stage of a proof development, one has a list of goals to +prove. Initially, the list consists only in the theorem itself. After +having applied some tactics, the list of goals contains the subgoals +generated by the tactics. + +To each subgoal is associated a number of hypotheses called the *local context* +of the goal. Initially, the local context contains the local variables and +hypotheses of the current section (see Section :ref:`gallina-assumptions`) and +the local variables and hypotheses of the theorem statement. It is enriched by +the use of certain tactics (see e.g. :tacn:`intro`). + +When a proof is completed, the message ``Proof completed`` is displayed. +One can then register this proof as a defined constant in the +environment. Because there exists a correspondence between proofs and +terms of λ-calculus, known as the *Curry-Howard isomorphism* +:cite:`How80,Bar81,Gir89,Hue88`, |Coq| stores proofs as terms of |Cic|. Those +terms are called *proof terms*. + + +.. exn:: No focused proof + +Coq raises this error message when one attempts to use a proof editing command +out of the proof editing mode. + +.. _proof-editing-mode: + +Switching on/off the proof editing mode +------------------------------------------- + +The proof editing mode is entered by asserting a statement, which typically is +the assertion of a theorem using an assertion command like :cmd:`Theorem`. The +list of assertion commands is given in Section :ref:`Assertions`. The command +:cmd:`Goal` can also be used. + +.. cmd:: Goal @form. + +This is intended for quick assertion of statements, without knowing in +advance which name to give to the assertion, typically for quick +testing of the provability of a statement. If the proof of the +statement is eventually completed and validated, the statement is then +bound to the name ``Unnamed_thm`` (or a variant of this name not already +used for another statement). + +.. cmd:: Qed + :name: Qed (interactive proof) + +This command is available in interactive editing proof mode when the +proof is completed. Then ``Qed`` extracts a proof term from the proof +script, switches back to Coq top-level and attaches the extracted +proof term to the declared name of the original goal. This name is +added to the environment as an opaque constant. + + +.. exn:: Attempt to save an incomplete proof + +.. note:: + + Sometimes an error occurs when building the proof term, because + tactics do not enforce completely the term construction + constraints. + +The user should also be aware of the fact that since the +proof term is completely rechecked at this point, one may have to wait +a while when the proof is large. In some exceptional cases one may +even incur a memory overflow. + +.. cmdv:: Defined. + :name: Defined (interactive proof) + +Defines the proved term as a transparent constant. + +.. cmdv:: Save @ident. + +Forces the name of the original goal to be :n:`@ident`. This +command (and the following ones) can only be used if the original goal +has been opened using the ``Goal`` command. + +.. cmd:: Admitted. + :name: Admitted (interactive proof) + +This command is available in interactive editing proof mode to give up +the current proof and declare the initial goal as an axiom. + +.. cmd:: Proof @term. + :name: Proof `term` + +This command applies in proof editing mode. It is equivalent to + +.. cmd:: exact @term. Qed. + +That is, you have to give the full proof in one gulp, as a +proof term (see Section :ref:`applyingtheorems`). + +.. cmdv:: Proof. + :name: Proof (interactive proof) + +Is a noop which is useful to delimit the sequence of tactic commands +which start a proof, after a ``Theorem`` command. It is a good practice to +use ``Proof``. as an opening parenthesis, closed in the script with a +closing ``Qed``. + + +See also: ``Proof with tactic.`` in Section +:ref:`tactics-implicit-automation`. + + +.. cmd:: Proof using @ident1 ... @identn. + +This command applies in proof editing mode. It declares the set of +section variables (see :ref:`gallina-assumptions`) used by the proof. At ``Qed`` time, the +system will assert that the set of section variables actually used in +the proof is a subset of the declared one. + +The set of declared variables is closed under type dependency. For +example if ``T`` is variable and a is a variable of type ``T``, the commands +``Proof using a`` and ``Proof using T a``` are actually equivalent. + + +.. cmdv:: Proof using @ident1 ... @identn with @tactic. + +in Section :ref:`tactics-implicit-automation`. + +.. cmdv:: Proof using All. + +Use all section variables. + + +.. cmdv:: Proof using Type. + +.. cmdv:: Proof using. + +Use only section variables occurring in the statement. + + +.. cmdv:: Proof using Type*. + +The ``*`` operator computes the forward transitive closure. E.g. if the +variable ``H`` has type ``p < 5`` then ``H`` is in ``p*`` since ``p`` occurs in the type +of ``H``. ``Type*`` is the forward transitive closure of the entire set of +section variables occurring in the statement. + + +.. cmdv:: Proof using -(@ident1 ... @identn). + +Use all section variables except :n:`@ident1` ... :n:`@identn`. + + +.. cmdv:: Proof using @collection1 + @collection2 . + + +.. cmdv:: Proof using @collection1 - @collection2 . + + +.. cmdv:: Proof using @collection - ( @ident1 ... @identn ). + + +.. cmdv:: Proof using @collection * . + +Use section variables being, respectively, in the set union, set +difference, set complement, set forward transitive closure. See +Section :ref:`nameaset` to know how to form a named collection. The ``*`` operator +binds stronger than ``+`` and ``-``. + + +Proof using options +``````````````````` + +The following options modify the behavior of ``Proof using``. + + +.. opt:: Default Proof Using "@expression". + + Use :n:`@expression` as the default ``Proof``` using value. E.g. ``Set Default + Proof Using "a b"``. will complete all ``Proof`` commands not followed by a + using part with using ``a`` ``b``. + + +.. opt:: Suggest Proof Using. + + When ``Qed`` is performed, suggest a using annotation if the user did not + provide one. + +.. _`nameaset`: + +Name a set of section hypotheses for ``Proof using`` +```````````````````````````````````````````````````` + +.. cmd:: Collection @ident := @section_subset_expr + +The command ``Collection`` can be used to name a set of section +hypotheses, with the purpose of making ``Proof using`` annotations more +compact. + + +.. cmdv:: Collection Some := x y z + +Define the collection named "Some" containing ``x``, ``y`` and ``z``. + + +.. cmdv:: Collection Fewer := Some - z + +Define the collection named "Fewer" containing only ``x`` and ``y``. + + +.. cmdv:: Collection Many := Fewer + Some +.. cmdv:: Collection Many := Fewer - Some + +Define the collection named "Many" containing the set union or set +difference of "Fewer" and "Some". + + +.. cmdv:: Collection Many := Fewer - (x y) + +Define the collection named "Many" containing the set difference of +"Fewer" and the unnamed collection ``x`` ``y`` + + +.. cmd:: Abort. + +This command cancels the current proof development, switching back to +the previous proof development, or to the |Coq| toplevel if no other +proof was edited. + + +.. exn:: No focused proof (No proof-editing in progress) + + + +.. cmdv:: Abort @ident. + +Aborts the editing of the proof named :n:`@ident`. + +.. cmdv:: Abort All. + +Aborts all current goals, switching back to the |Coq| +toplevel. + + + +.. cmd:: Existential @num := @term. + +This command instantiates an existential variable. :n:`@num` is an index in +the list of uninstantiated existential variables displayed by ``Show +Existentials`` (described in Section :ref:`requestinginformation`). + +This command is intended to be used to instantiate existential +variables when the proof is completed but some uninstantiated +existential variables remain. To instantiate existential variables +during proof edition, you should use the tactic :tacn:`instantiate`. + + +See also: ``instantiate (num:= term).`` in Section +:ref:`controllingtheproofflow`. +See also: ``Grab Existential Variables.`` below. + + +.. cmd:: Grab Existential Variables. + +This command can be run when a proof has no more goal to be solved but +has remaining uninstantiated existential variables. It takes every +uninstantiated existential variable and turns it into a goal. + + +Navigation in the proof tree +-------------------------------- + + +.. cmd:: Undo. + +This command cancels the effect of the last command. Thus, it +backtracks one step. + + +.. cmdv:: Undo @num. + +Repeats Undo :n:`@num` times. + +.. cmdv:: Restart. + :name: Restart + +This command restores the proof editing process to the original goal. + + +.. exn:: No focused proof to restart + + +.. cmd:: Focus. + +This focuses the attention on the first subgoal to prove and the +printing of the other subgoals is suspended until the focused subgoal +is solved or unfocused. This is useful when there are many current +subgoals which clutter your screen. + + +.. cmdv:: Focus @num. + +This focuses the attention on the :n:`@num` th subgoal to +prove. + +*This command is deprecated since 8.8*: prefer the use of bullets or +focusing brackets instead, including :n:`@num : %{` + +.. cmd:: Unfocus. + +This command restores to focus the goal that were suspended by the +last ``Focus`` command. + +*This command is deprecated since 8.8.* + +.. cmd:: Unfocused. + +Succeeds if the proof is fully unfocused, fails is there are some +goals out of focus. + +.. _curly-braces: + +.. cmd:: %{ %| %} + +The command ``{`` (without a terminating period) focuses on the first +goal, much like ``Focus.`` does, however, the subproof can only be +unfocused when it has been fully solved ( *i.e.* when there is no +focused goal left). Unfocusing is then handled by ``}`` (again, without a +terminating period). See also example in next section. + +Note that when a focused goal is proved a message is displayed +together with a suggestion about the right bullet or ``}`` to unfocus it +or focus the next one. + +.. cmdv:: @num: %{ + +This focuses on the :n:`@num` th subgoal to prove. + +Error messages: + +.. exn:: This proof is focused, but cannot be unfocused this way + +You are trying to use ``}`` but the current subproof has not been fully solved. + +.. exn:: No such goal + :name: No such goal (focusing) + +.. exn:: Brackets only support the single numbered goal selector + +See also error messages about bullets below. + +.. _bullets: + +Bullets +``````` + +Alternatively to ``{`` and ``}``, proofs can be structured with bullets. The +use of a bullet ``b`` for the first time focuses on the first goal ``g``, the +same bullet cannot be used again until the proof of ``g`` is completed, +then it is mandatory to focus the next goal with ``b``. The consequence is +that ``g`` and all goals present when ``g`` was focused are focused with the +same bullet ``b``. See the example below. + +Different bullets can be used to nest levels. The scope of bullet does +not go beyond enclosing ``{`` and ``}``, so bullets can be reused as further +nesting levels provided they are delimited by these. Available bullets +are ``-``, ``+``, ``*``, ``--``, ``++``, ``**``, ``---``, ``+++``, ``***``, ... (without a terminating period). + +Note again that when a focused goal is proved a message is displayed +together with a suggestion about the right bullet or ``}`` to unfocus it +or focus the next one. + +.. note:: + + In Proof General (``Emacs`` interface to |Coq|), you must use + bullets with the priority ordering shown above to have a correct + indentation. For example ``-`` must be the outer bullet and ``**`` the inner + one in the example below. + +The following example script illustrates all these features: + +.. example:: + .. coqtop:: all + + Goal (((True /\ True) /\ True) /\ True) /\ True. + Proof. + split. + - split. + + split. + ** { split. + - trivial. + - trivial. + } + ** trivial. + + trivial. + - assert True. + { trivial. } + assumption. + + +.. exn:: Wrong bullet @bullet1 : Current bullet @bullet2 is not finished. + +Before using bullet :n:`@bullet1` again, you should first finish proving the current focused goal. Note that :n:`@bullet1` and :n:`@bullet2` may be the same. + +.. exn:: Wrong bullet @bullet1 : Bullet @bullet2 is mandatory here. + +You must put :n:`@bullet2` to focus next goal. No other bullet is allowed here. + +.. exn:: No such goal. Focus next goal with bullet @bullet. + +You tried to applied a tactic but no goal where under focus. Using :n:`@bullet` is mandatory here. + +.. exn:: No such goal. Try unfocusing with %{. + +You just finished a goal focused by ``{``, you must unfocus it with ``}``. + +Set Bullet Behavior +``````````````````` + +The bullet behavior can be controlled by the following commands. + +.. opt:: Bullet Behavior "None" + +This makes bullets inactive. + +.. opt:: Bullet Behavior "Strict Subproofs" + +This makes bullets active (this is the default behavior). + + +.. _requestinginformation: + +Requesting information +---------------------- + + +.. cmd:: Show. + +This command displays the current goals. + + +.. cmdv:: Show @num + +Displays only the :n:`@num`-th subgoal. + +.. exn:: No such goal +.. exn:: No focused proof + +.. cmdv:: Show @ident. + +Displays the named goal :n:`@ident`. This is useful in +particular to display a shelved goal but only works if the +corresponding existential variable has been named by the user +(see :ref:`existential-variables`) as in the following example. + +.. example:: + + .. coqtop:: all + + Goal exists n, n = 0. + eexists ?[n]. + Show n. + +.. cmdv:: Show Script. + +Displays the whole list of tactics applied from the +beginning of the current proof. This tactics script may contain some +holes (subgoals not yet proved). They are printed under the form + +``<Your Tactic Text here>``. + +.. cmdv:: Show Proof. + +It displays the proof term generated by the tactics +that have been applied. If the proof is not completed, this term +contain holes, which correspond to the sub-terms which are still to be +constructed. These holes appear as a question mark indexed by an +integer, and applied to the list of variables in the context, since it +may depend on them. The types obtained by abstracting away the context +from the type of each hole-placer are also printed. + +.. cmdv:: Show Conjectures. + +It prints the list of the names of all the +theorems that are currently being proved. As it is possible to start +proving a previous lemma during the proof of a theorem, this list may +contain several names. + +.. cmdv:: Show Intro. + +If the current goal begins by at least one product, +this command prints the name of the first product, as it would be +generated by an anonymous ``intro``. The aim of this command is to ease +the writing of more robust scripts. For example, with an appropriate +Proof General macro, it is possible to transform any anonymous ``intro`` +into a qualified one such as ``intro y13``. In the case of a non-product +goal, it prints nothing. + +.. cmdv:: Show Intros. + +This command is similar to the previous one, it +simulates the naming process of an intros. + +.. cmdv:: Show Existentials. + +It displays the set of all uninstantiated +existential variables in the current proof tree, along with the type +and the context of each variable. + +.. cmdv:: Show Match @ident. + +This variant displays a template of the Gallina +``match`` construct with a branch for each constructor of the type +:n:`@ident` + +.. example:: + .. coqtop:: all + + Show Match nat. + +.. exn:: Unknown inductive type + +.. _ShowUniverses: + +.. cmdv:: Show Universes. + +It displays the set of all universe constraints and +its normalized form at the current stage of the proof, useful for +debugging universe inconsistencies. + + +.. cmd:: Guarded. + +Some tactics (e.g. :tacn:`refine` :ref:`applyingtheorems`) allow to build proofs using +fixpoint or co-fixpoint constructions. Due to the incremental nature +of interactive proof construction, the check of the termination (or +guardedness) of the recursive calls in the fixpoint or cofixpoint +constructions is postponed to the time of the completion of the proof. + +The command ``Guarded`` allows checking if the guard condition for +fixpoint and cofixpoint is violated at some time of the construction +of the proof without having to wait the completion of the proof. + + +Controlling the effect of proof editing commands +------------------------------------------------ + + +.. opt:: Hyps Limit @num + +This option controls the maximum number of hypotheses displayed in goals +after the application of a tactic. All the hypotheses remain usable +in the proof development. +When unset, it goes back to the default mode which is to print all +available hypotheses. + + +.. opt:: Automatic Introduction + +This option controls the way binders are handled +in assertion commands such as ``Theorem ident [binders] : form``. When the +option is set, which is the default, binders are automatically put in +the local context of the goal to prove. + +The option can be unset by issuing ``Unset Automatic Introduction``. When +the option is unset, binders are discharged on the statement to be +proved and a tactic such as intro (see Section :ref:`managingthelocalcontext`) has to be +used to move the assumptions to the local context. + + +Controlling memory usage +------------------------ + +When experiencing high memory usage the following commands can be used +to force |Coq| to optimize some of its internal data structures. + + +.. cmd:: Optimize Proof. + +This command forces |Coq| to shrink the data structure used to represent +the ongoing proof. + + +.. cmd:: Optimize Heap. + +This command forces the |OCaml| runtime to perform a heap compaction. +This is in general an expensive operation. +See: `OCaml Gc <http://caml.inria.fr/pub/docs/manual-ocaml/libref/Gc.html#VALcompact>`_ +There is also an analogous tactic :tac:`optimize_heap`. diff --git a/doc/sphinx/proof-engine/ssreflect-proof-language.rst b/doc/sphinx/proof-engine/ssreflect-proof-language.rst index 61dffa0243..977a5b8fad 100644 --- a/doc/sphinx/proof-engine/ssreflect-proof-language.rst +++ b/doc/sphinx/proof-engine/ssreflect-proof-language.rst @@ -6,10 +6,7 @@ The |SSR| proof language ------------------------------ -:Source: https://coq.inria.fr/distrib/current/refman/ssreflect.html -:Converted by: Enrico Tassi - -Author: Georges Gonthier, Assia Mahboubi, Enrico Tassi +:Authors: Georges Gonthier, Assia Mahboubi, Enrico Tassi Introduction @@ -451,7 +448,7 @@ Anonymous arguments ~~~~~~~~~~~~~~~~~~~ When in a definition, the type of a certain argument is mandatory, but -not its name, one usually use “arrow” abstractions for prenex +not its name, one usually uses “arrow” abstractions for prenex arguments, or the ``(_ : term)`` syntax for inner arguments. In |SSR|, the latter can be replaced by the open syntax ``of term`` or (equivalently) ``& term``, which are both syntactically equivalent to a @@ -496,7 +493,10 @@ inferred from the whole context of the goal (see for example section Definitions ~~~~~~~~~~~ -The pose tactic allows to add a defined constant to a proof context. +.. tacn:: pose + :name: pose (ssreflect) + +This tactic allows to add a defined constant to a proof context. |SSR| generalizes this tactic in several ways. In particular, the |SSR| pose tactic supports *open syntax*: the body of the definition does not need surrounding parentheses. For instance: @@ -518,7 +518,7 @@ is a valid tactic expression. The pose tactic is also improved for the local definition of higher order terms. Local definitions of functions can use the same syntax as -global ones. For example the tactic ``pose`` supoprts parameters: +global ones. For example, the tactic ``pose`` supoprts parameters: .. example:: @@ -1295,7 +1295,7 @@ is a synonym for: intro top; first [refine top | refine (top _) | refine (top _ _) | …]; clear top. -where ``top`` is fresh name, and the sequence of refine tactics tries to +where ``top`` is a fresh name, and the sequence of refine tactics tries to catch the appropriate number of wildcards to be inserted. Note that this use of the refine tactic implies that the tactic tries to match the goal up to expansion of constants and evaluation of subterms. @@ -1352,6 +1352,7 @@ Discharge The general syntax of the discharging tactical ``:`` is: .. tacn:: @tactic {? @ident } : {+ @d_item } {? @clear_switch } + :name: ... : ... (ssreflect) .. prodn:: d_item ::= {? @occ_switch %| @clear_switch } @term @@ -1503,9 +1504,11 @@ side of an equation. The abstract tactic ``````````````````` -The ``abstract`` tactic assigns an ``abstract`` constant previously -introduced with the ``[: name ]`` intro pattern -(see section :ref:`introduction_ssr`). +.. tacn:: abstract: {+ d_item} + :name abstract (ssreflect) + +This tactic assigns an abstract constant previously introduced with the ``[: +name ]`` intro pattern (see section :ref:`introduction_ssr`). In a goal like the following:: @@ -1573,7 +1576,7 @@ The :token:`i_pattern` s can be seen as a variant of *intro patterns* :ref:`tactics`: each performs an introduction operation, i.e., pops some variables or assumptions from the goal. -An :token:`s_item` can simplify the set of subgoals or the subgoal themselves: +An :token:`s_item` can simplify the set of subgoals or the subgoals themselves: + ``//`` removes all the “trivial” subgoals that can be resolved by the |SSR| tactic ``done`` described in :ref:`terminators_ssr`, i.e., @@ -1812,6 +1815,8 @@ of a :token:`d_item` immediately following this ``/`` switch, using the syntax: .. tacv:: case: {+ @d_item } / {+ @d_item } + :name: case (ssreflect) + .. tacv:: elim: {+ @d_item } / {+ @d_item } The :token:`d_item` on the right side of the ``/`` switch are discharged as @@ -1831,7 +1836,7 @@ compact syntax: case: {2}_ / eqP. -were ``_`` is interpreted as ``(_ == _)`` since +where ``_`` is interpreted as ``(_ == _)`` since ``eqP T a b : reflect (a = b) (a == b)`` and reflect is a type family with one index. @@ -2074,7 +2079,7 @@ is equivalent to: do [done | by move=> top; apply top]. -where top is a fresh name affected to the top assumption of the goal. +where ``top`` is a fresh name assigned to the top assumption of the goal. This applied form is supported by the : discharge tactical, and the tactic: @@ -2090,7 +2095,7 @@ is equivalent to: (see section :ref:`discharge_ssr` for the documentation of the apply: combination). -Warning The list of tactics, possibly chained by semi-columns, that +Warning The list of tactics, possibly chained by semicolons, that follows a by keyword is considered as a parenthesized block applied to the current goal. Hence for example if the tactic: @@ -2123,7 +2128,7 @@ generated by the previous tactic. This covers the frequent cases where a tactic generates two subgoals one of which can be easily disposed of. -This is an other powerful way of linearization of scripts, since it +This is another powerful way of linearization of scripts, since it happens very often that a trivial subgoal can be solved in a less than one line tactic. For instance, the tactic: @@ -2131,14 +2136,14 @@ one line tactic. For instance, the tactic: :name: last tries to solve the last subgoal generated by the first -tactic using the given second tactic , and fails if it does not succeeds. -Its analogous +tactic using the given second tactic, and fails if it does not succeed. +Its analogue .. tacn:: @tactic ; first by @tactic - :name: first + :name: first (ssreflect) tries to solve the first subgoal generated by the first tactic using the -second given tactic, and fails if it does not succeeds. +second given tactic, and fails if it does not succeed. |SSR| also offers an extension of this facility, by supplying tactics to *permute* the subgoals generated by a tactic. The tactic: @@ -2215,7 +2220,7 @@ Iteration thanks to the do tactical, whose general syntax is: .. tacn:: do {? @mult } ( @tactic | [ {+| @tactic } ] ) - :name: do + :name: do (ssreflect) where :token:`mult` is a *multiplier*. @@ -2259,14 +2264,14 @@ For instance, the tactic: tactic; do 1? rewrite mult_comm. -rewrites at most one time the lemma ``mult_com`` in all the subgoals +rewrites at most one time the lemma ``mult_comm`` in all the subgoals generated by tactic , whereas the tactic: .. coqtop:: in tactic; do 2! rewrite mult_comm. -rewrites exactly two times the lemma ``mult_com`` in all the subgoals +rewrites exactly two times the lemma ``mult_comm`` in all the subgoals generated by tactic, and fails if this rewrite is not possible in some subgoal. @@ -2335,10 +2340,10 @@ to the following one: .. tacv:: @tactic in {+ @clear_switch | {? @ } @ident | ( @ident ) | ( {? @ } @ident := @c_pattern ) } {? * } In its simplest form the last option lets one rename hypotheses that -can’t be cleared (like section variables). For example ``(y := x)`` +can’t be cleared (like section variables). For example, ``(y := x)`` generalizes over ``x`` and reintroduces the generalized variable under the name ``y`` (and does not clear ``x``). -For a more precise description this form of localization refer +For a more precise description of this form of localization refer to :ref:`advanced_generalization_ssr`. @@ -2351,7 +2356,7 @@ Forward reasoning structures the script by explicitly specifying some assumptions to be added to the proof context. It is closely associated with the declarative style of proof, since an extensive use of these highlighted statements make the script closer to a (very detailed) -text book proof. +textbook proof. Forward chaining tactics allow to state an intermediate lemma and start a piece of script dedicated to the proof of this statement. The use of closing @@ -2492,7 +2497,7 @@ also supported (assuming x occurs in the goal only): have {x} -> : x = y. -An other frequent use of the intro patterns combined with ``have`` is the +Another frequent use of the intro patterns combined with ``have`` is the destruction of existential assumptions like in the tactic: .. example:: @@ -2752,12 +2757,9 @@ type classes inference. No inference for ``t``. Unresolved instances are quantified in the (inferred) type of ``t`` and abstracted in ``t``. +.. opt:: SsrHave NoTCResolution -The behavior of |SSR| 1.4 and below (never resolve type classes) -can be restored with the option - -.. cmd:: Set SsrHave NoTCResolution. - + This option restores the behavior of |SSR| 1.4 and below (never resolve type classes). Variants: the suff and wlog tactics ``````````````````````````````````` @@ -2845,8 +2847,8 @@ term -> G. If the optional list of :token:`itent` is present on the left side of ``/``, these constants are generalized in the -premise (term -> G) of the first subgoal. By default the body of local -definitions is erased. This behavior can be inhibited prefixing the +premise (term -> G) of the first subgoal. By default bodies of local +definitions are erased. This behavior can be inhibited by prefixing the name of the local definition with the ``@`` character. In the second subgoal, the tactic: @@ -2936,7 +2938,7 @@ renaming does not require the original variable to be cleared. The syntax ``(@x := y)`` generates a let-in abstraction but with the following caveat: ``x`` will not bind ``y``, but its body, whenever ``y`` can be -unfolded. This cover the case of both local and global definitions, as +unfolded. This covers the case of both local and global definitions, as illustrated in the following example. .. example:: @@ -3035,7 +3037,7 @@ operation should be performed: specifies if and how the rewrite operation should be repeated. + A rewrite operation matches the occurrences of a *rewrite pattern*, - and replaces these occurrences by an other term, according to the + and replaces these occurrences by another term, according to the given :token:`r_item`. The optional *redex switch* ``[r_pattern]``, which should always be surrounded by brackets, gives explicitly this rewrite @@ -3329,7 +3331,7 @@ The rewrite tactic can be provided a *tuple* of rewrite rules, or more generally a tree of such rules, since this tuple can feature arbitrary inner parentheses. We call *multirule* such a generalized rewrite rule. This feature is of special interest when it is combined with -multiplier switches, which makes the rewrite tactic iterates the +multiplier switches, which makes the rewrite tactic iterate the rewrite operations prescribed by the rules on the current goal. @@ -3473,7 +3475,7 @@ efficient ones, e.g. for the purpose of a correctness proof. Wildcards vs abstractions ````````````````````````` -The rewrite tactic supports :token:`r_items` containing holes. For example in +The rewrite tactic supports :token:`r_items` containing holes. For example, in the tactic ``rewrite (_ : _ * 0 = 0).`` the term ``_ * 0 = 0`` is interpreted as ``forall n : nat, n * 0 = 0.`` Anyway this tactic is *not* equivalent to @@ -3730,14 +3732,15 @@ We provide a special tactic unlock for unfolding such definitions while removing “locks”, e.g., the tactic: .. tacn:: unlock {? @occ_switch } @ident + :name: unlock replaces the occurrence(s) of :token:`ident` coded by the :token:`occ_switch` with the corresponding body. We found that it was usually preferable to prevent the expansion of some functions by the partial evaluation switch ``/=``, unless this -allowed the evaluation of a condition. This is possible thanks to an -other mechanism of term tagging, resting on the following *Notation*: +allowed the evaluation of a condition. This is possible thanks to another +mechanism of term tagging, resting on the following *Notation*: .. coqtop:: in @@ -3781,7 +3784,7 @@ arithmetic operations. We define for instance: The operation ``addn`` behaves exactly like ``plus``, except that ``(addn (S n) m)`` will not simplify spontaneously to -``(S (addn n m))`` (the two terms, however, are inter-convertible). +``(S (addn n m))`` (the two terms, however, are convertible). In addition, the unfolding step: ``rewrite /addn`` will replace ``addn`` directly with ``plus``, so the ``nosimpl`` form is essentially invisible. @@ -3792,7 +3795,7 @@ essentially invisible. Congruence ~~~~~~~~~~ -Because of the way matching interferes with type families parameters, +Because of the way matching interferes with parameters of type families, the tactic: .. coqtop:: in @@ -3912,8 +3915,8 @@ The simple form of patterns used so far, terms possibly containing wild cards, often require an additional :token:`occ_switch` to be specified. While this may work pretty fine for small goals, the use of polymorphic functions and dependent types may lead to an invisible -duplication of functions arguments. These copies usually end up in -types hidden by the implicit arguments machinery or by user defined +duplication of function arguments. These copies usually end up in +types hidden by the implicit arguments machinery or by user-defined notations. In these situations computing the right occurrence numbers is very tedious because they must be counted on the goal as printed after setting the Printing All flag. Moreover the resulting script is @@ -3981,7 +3984,7 @@ pattern for the redex looking at the rule used for rewriting. The first :token:`c_pattern` is the simplest form matching any context but selecting a specific redex and has been described in the previous sections. We have seen so far that the possibility of selecting a -redex using a term with holes is already a powerful mean of redex +redex using a term with holes is already a powerful means of redex selection. Similarly, any terms provided by the user in the more complex forms of :token:`c_patterns` presented in the tables above can contain @@ -4064,7 +4067,7 @@ Contextual pattern in set and the : tactical As already mentioned in section :ref:`abbreviations_ssr` the ``set`` tactic takes as an argument a term in open syntax. This term is interpreted as the -simplest for of :token:`c_pattern`. To void confusion in the grammar, open +simplest form of :token:`c_pattern`. To avoid confusion in the grammar, open syntax is supported only for the simplest form of patterns, while parentheses are required around more complex patterns. @@ -4086,17 +4089,17 @@ parentheses are required around more complex patterns. set t := (a + _ in X in _ = X). -Since the user may define an infix notation for ``in`` the former tactic -may result ambiguous. The disambiguation rule implemented is to prefer +Since the user may define an infix notation for ``in`` the result of the former +tactic may be ambiguous. The disambiguation rule implemented is to prefer patterns over simple terms, but to interpret a pattern with double -parentheses as a simple term. For example the following tactic would +parentheses as a simple term. For example, the following tactic would capture any occurrence of the term ``a in A``. .. coqtop:: in set t := ((a in A)). -Contextual pattern can also be used as arguments of the ``:`` tactical. +Contextual patterns can also be used as arguments of the ``:`` tactical. For example: .. coqtop:: in @@ -4139,7 +4142,7 @@ Contextual patterns in rewrite Note that the right hand side of ``addn0`` is undetermined, but the rewrite pattern specifies the redex explicitly. The right hand side - of ``addn0`` is unified with the term identified by ``X``, ``0`` here. + of ``addn0`` is unified with the term identified by ``X``, here ``0``. The following pattern does not specify a redex, since it identifies an @@ -4269,7 +4272,7 @@ generation (see section :ref:`generation_of_equations_ssr`). .. example:: - The following script illustrate a toy example of this feature. Let us + The following script illustrates a toy example of this feature. Let us define a function adding an element at the end of a list: .. coqtop:: reset @@ -4283,7 +4286,7 @@ generation (see section :ref:`generation_of_equations_ssr`). .. coqtop:: all Variable d : Type. - Fixpoint add_last(s : list d) (z : d) {struct s} : list d := + Fixpoint add_last (s : list d) (z : d) {struct s} : list d := if s is cons x s' then cons x (add_last s' z) else z :: nil. One can define an alternative, reversed, induction principle on @@ -4296,7 +4299,7 @@ generation (see section :ref:`generation_of_equations_ssr`). forall s : list d, P s. Then the combination of elimination views with equation names result - in a concise syntax for reasoning inductively using the user defined + in a concise syntax for reasoning inductively using the user-defined elimination scheme. .. coqtop:: all @@ -4305,8 +4308,8 @@ generation (see section :ref:`generation_of_equations_ssr`). elim/last_ind_list E : l=> [| u v]; last first. -User provided eliminators (potentially generated with the ``Function`` -|Coq|’s command) can be combined with the type family switches described +User-provided eliminators (potentially generated with |Coq|’s ``Function`` +command) can be combined with the type family switches described in section :ref:`type_families_ssr`. Consider an eliminator ``foo_ind`` of type: @@ -4341,7 +4344,7 @@ The ``elim/`` tactic distinguishes two cases: As explained in section :ref:`type_families_ssr`, the initial prefix of ``ei`` can be omitted. -Here an example of a regular, but non trivial, eliminator. +Here is an example of a regular, but nontrivial, eliminator. .. example:: @@ -4423,7 +4426,7 @@ Here an example of a regular, but non trivial, eliminator. ``P`` should be the same as the second argument of ``plus``, in the second argument of ``P``, but ``y`` and ``z`` do no unify. -Here an example of a truncated eliminator: +Here is an example of a truncated eliminator: .. example:: @@ -4481,7 +4484,7 @@ Interpreting assumptions ~~~~~~~~~~~~~~~~~~~~~~~~ Interpreting an assumption in the context of a proof consists in -applying it a lemma before generalizing, and/or decomposing this +applying to it a lemma before generalizing, and/or decomposing this assumption. For instance, with the extensive use of boolean reflection (see section :ref:`views_and_reflection_ssr`.4), it is quite frequent to need to decompose the logical interpretation of (the boolean @@ -4689,7 +4692,7 @@ the bookkeeping tactical ``=>`` since this would be redundant with the Boolean reflection ~~~~~~~~~~~~~~~~~~ -In the Calculus of Inductive Construction, there is an obvious +In the Calculus of Inductive Constructions, there is an obvious distinction between logical propositions and boolean values. On the one hand, logical propositions are objects of *sort* ``Prop`` which is the carrier of intuitionistic reasoning. Logical connectives in @@ -5002,7 +5005,7 @@ but they also allow complex transformation, involving negations. Note that views, being part of :token:`i_pattern`, can be used to interpret assertions too. For example the following script asserts ``a && b`` but -actually used its propositional interpretation. +actually uses its propositional interpretation. .. example:: @@ -5038,7 +5041,7 @@ applied to a goal ``top`` is interpreted in the following way: Like assumption interpretation view hints, goal interpretation ones -are user defined lemmas stored (see section :ref:`views_and_reflection_ssr`) in the ``Hint View`` +are user-defined lemmas stored (see section :ref:`views_and_reflection_ssr`) in the ``Hint View`` database bridging the possible gap between the type of ``term`` and the type of the goal. @@ -5132,7 +5135,7 @@ See the files ``ssreflect.v`` and ``ssrbool.v`` for examples. Multiple views ~~~~~~~~~~~~~~ -The hypotheses and the goal can be interpreted applying multiple views +The hypotheses and the goal can be interpreted by applying multiple views in sequence. Both move and apply can be followed by an arbitrary number of ``/term``. The main difference between the following two tactics @@ -5188,8 +5191,9 @@ equivalences are indeed taken into account, otherwise only single |SSR| proposes an extension of the Search command. Its syntax is: .. cmd:: Search {? @pattern } {* {? - } %( @string %| @pattern %) {? % @ident} } {? in {+ {? - } @qualid } } + :name: Search (ssreflect) -where :token:`qualid` is the name of an open module. This command search returns +where :token:`qualid` is the name of an open module. This command returns the list of lemmas: @@ -5214,7 +5218,7 @@ Note that: + As for regular terms, patterns can feature scope indications. For instance, the command: ``Search _ (_ + _)%N.`` lists all the lemmas whose - statement (conclusion or hypotheses) involve an application of the + statement (conclusion or hypotheses) involves an application of the binary operation denoted by the infix ``+`` symbol in the ``N`` scope (which is |SSR| scope for natural numbers). + Patterns with holes should be surrounded by parentheses. @@ -5491,7 +5495,7 @@ prenex implicits declaration see :ref:`parametric_polymorphism_ssr` used for such generated names. .. [#7] More precisely, it should have a quantified inductive type with a assumptions and m − a constructors. -.. [#8] This is an implementation feature: there is not such obstruction +.. [#8] This is an implementation feature: there is no such obstruction in the metatheory .. [#9] The current state of the proof shall be displayed by the Show Proof command of |Coq| proof mode. diff --git a/doc/sphinx/proof-engine/tactics.rst b/doc/sphinx/proof-engine/tactics.rst index da34e3b55b..7a45272f25 100644 --- a/doc/sphinx/proof-engine/tactics.rst +++ b/doc/sphinx/proof-engine/tactics.rst @@ -24,7 +24,7 @@ Each (sub)goal is denoted with a number. The current goal is numbered 1. By default, a tactic is applied to the current goal, but one can address a particular goal in the list by writing n:tactic which means “apply tactic tactic to goal number n”. We can show the list of -subgoals by typing Show (see Section :ref:`TODO-7.3.1-Show`). +subgoals by typing Show (see Section :ref:`requestinginformation`). Since not every rule applies to a given statement, every tactic cannot be used to reduce any goal. In other words, before applying a tactic @@ -34,15 +34,16 @@ satisfied. If it is not the case, the tactic raises an error message. Tactics are built from atomic tactics and tactic expressions (which extends the folklore notion of tactical) to combine those atomic tactics. This chapter is devoted to atomic tactics. The tactic -language will be described in Chapter :ref:`TODO-9-Thetacticlanguage`. +language will be described in Chapter :ref:`ltac`. + +.. _invocation-of-tactics: Invocation of tactics ------------------------- A tactic is applied as an ordinary command. It may be preceded by a -goal selector (see Section :ref:`TODO-9.2-Semantics`). If no selector is -specified, the default selector (see Section -:ref:`TODO-8.1.1-Setdefaultgoalselector`) is used. +goal selector (see Section :ref:`ltac-semantics`). If no selector is +specified, the default selector is used. .. _tactic_invocation_grammar: @@ -50,20 +51,15 @@ specified, the default selector (see Section tactic_invocation : toplevel_selector : tactic. : |tactic . -.. cmd:: Set Default Goal Selector @toplevel_selector. - -After using this command, the default selector – used when no selector -is specified when applying a tactic – is set to the chosen value. The -initial value is 1, hence the tactics are, by default, applied to the -first goal. Using Set Default Goal Selector ‘‘all’’ will make is so -that tactics are, by default, applied to every goal simultaneously. -Then, to apply a tactic tac to the first goal only, you can write -1:tac. Although more selectors are available, only ‘‘all’’ or a single -natural number are valid default goal selectors. - -.. cmd:: Test Default Goal Selector. +.. opt:: Default Goal Selector @toplevel_selector -This command displays the current default selector. + This option controls the default selector – used when no selector is + specified when applying a tactic – is set to the chosen value. The initial + value is 1, hence the tactics are, by default, applied to the first goal. + Using value ``all`` will make is so that tactics are, by default, applied to + every goal simultaneously. Then, to apply a tactic tac to the first goal + only, you can write ``1:tac``. Although more selectors are available, only + ``all`` or a single natural number are valid default goal selectors. .. _bindingslist: @@ -94,7 +90,7 @@ bindings_list`` where ``bindings_list`` may be of two different forms: + A bindings list can also be a simple list of terms :n:`{* term}`. In that case the references to which these terms correspond are determined by the tactic. In case of ``induction``, ``destruct``, ``elim`` - and ``case`` (see :ref:`TODO-9-Thetacticlanguage`) the terms have to + and ``case`` (see :ref:`ltac`) the terms have to provide instances for all the dependent products in the type of term while in the case of ``apply``, or of ``constructor`` and its variants, only instances for the dependent products that are not bound in the conclusion of the type @@ -122,14 +118,12 @@ following syntax: The role of an occurrence clause is to select a set of occurrences of a term in a goal. In the first case, the :n:`@ident {? at {* num}}` parts indicate that -occurrences have to be selected in the hypotheses named :n:`@ident`. If no numbers -are given for hypothesis :n:`@ident`, then all the occurrences of `term` in the -hypothesis are selected. If numbers are given, they refer to occurrences of -`term` when the term is printed using option ``Set Printing All`` (see -:ref:`TODO-2.9-Printingconstructionsinfull`), counting from left to right. In -particular, occurrences of `term` in implicit arguments (see -:ref:`TODO-2.7-Implicitarguments`) or coercions (see :ref:`TODO-2.8-Coercions`) -are counted. +occurrences have to be selected in the hypotheses named :n:`@ident`. If no +numbers are given for hypothesis :n:`@ident`, then all the occurrences of `term` +in the hypothesis are selected. If numbers are given, they refer to occurrences +of `term` when the term is printed using option :opt:`Printing All`, counting +from left to right. In particular, occurrences of `term` in implicit arguments +(see :ref:`ImplicitArguments`) or coercions (see :ref:`Coercions`) are counted. If a minus sign is given between at and the list of occurrences, it negates the condition so that the clause denotes all the occurrences @@ -154,10 +148,11 @@ Here are some tactics that understand occurrences clauses: ``set``, ``remember`` , ``induction``, ``destruct``. -See also: :ref:`TODO-8.3.7-Managingthelocalcontext`, -:ref:`TODO-8.5.2-Caseanalysisandinduction`, -:ref:`TODO-2.9-Printingconstructionsinfull`. +See also: :ref:`Managingthelocalcontext`, +:ref:`caseanalysisandinduction`, +:ref:`printing_constructions_full`. +.. _applyingtheorems: Applying theorems --------------------- @@ -168,11 +163,12 @@ Applying theorems This tactic applies to any goal. It gives directly the exact proof term of the goal. Let ``T`` be our goal, let ``p`` be a term of type ``U`` then ``exact p`` succeeds iff ``T`` and ``U`` are convertible (see -:ref:`TODO-4.3-Conversionrules`). +:ref:`Conversion-rules`). .. exn:: Not an exact proof. .. tacv:: eexact @term. + :name: eexact This tactic behaves like exact but is able to handle terms and goals with meta-variables. @@ -186,6 +182,7 @@ the goal. If it is the case, the subgoal is proved. Otherwise, it fails. .. exn:: No such assumption. .. tacv:: eassumption + :name: eassumption This tactic behaves like assumption but is able to handle goals with meta-variables. @@ -238,6 +235,7 @@ useful to advanced users. cast around it. .. tacv:: simple refine @term + :name: simple refine This tactic behaves like refine, but it does not shelve any subgoal. It does not perform any beta-reduction either. @@ -248,6 +246,7 @@ useful to advanced users. resolution of typeclasses. .. tacv:: simple notypeclasses refine @term + :name: simple notypeclasses refine This tactic behaves like ``simple refine`` except it performs typechecking without resolution of typeclasses. @@ -277,7 +276,7 @@ gets the form :g:`(fun x => Q) u`:sub:`1` :g:`...` :g:`u`:sub:`n`. The apply tactic failed to match the conclusion of term and the current goal. You can help the apply tactic by transforming your goal with the -:ref:`change <change_term>` or :tacn:`pattern` tactics. +:tacn:`change` or :tacn:`pattern` tactics. .. exn:: Unable to find an instance for the variables {+ @ident}. @@ -285,7 +284,7 @@ This occurs when some instantiations of the premises of term are not deducible from the unification. This is the case, for instance, when you want to apply a transitivity property. In this case, you have to use one of the variants below: -.. cmd:: apply @term with {+ @term} +.. tacv:: apply @term with {+ @term} Provides apply with explicit instantiations for all dependent premises of the type of term that do not occur in the conclusion and consequently cannot be @@ -314,10 +313,11 @@ generated by ``apply term``:sub:`i` , starting from the application of The tactic ``eapply`` behaves like ``apply`` but it does not fail when no instantiations are deducible for some variables in the premises. Rather, it turns these variables into existential variables which are variables still to -instantiate (see :ref:`TODO-2.11-ExistentialVariables`). The instantiation is +instantiate (see :ref:`Existential-Variables`). The instantiation is intended to be found later in the proof. .. tacv:: simple apply @term. + :name: simple apply This behaves like ``apply`` but it reasons modulo conversion only on subterms that contain no variables to instantiate. For instance, the following example @@ -340,11 +340,12 @@ does. .. tacv:: {? simple} apply {+, @term {? with @bindings_list}} .. tacv:: {? simple} eapply {+, @term {? with @bindings_list}} + :name: simple eapply This summarizes the different syntaxes for ``apply`` and ``eapply``. .. tacv:: lapply @term - :name: `lapply + :name: lapply This tactic applies to any goal, say :g:`G`. The argument term has to be well-formed in the current context, its type being reducible to a non-dependent @@ -435,7 +436,7 @@ sequence ``cut B. 2:apply H.`` where ``cut`` is described below. ``forall A, ... -> A``. Excluding this kind of lemma can be avoided by setting the following option: -.. opt:: Set Universal Lemma Under Conjunction. +.. opt:: Universal Lemma Under Conjunction This option, which preserves compatibility with versions of Coq prior to 8.4 is also available for :n:`apply @term in @ident` (see :tacn:`apply ... in`). @@ -520,8 +521,8 @@ sequence ``cut B. 2:apply H.`` where ``cut`` is described below. constructor of :g:`I`, then ``constructor i`` is equivalent to ``intros; apply c``:sub:`i`. -.. exn:: Not an inductive product. -.. exn:: Not enough constructors. +.. exn:: Not an inductive product +.. exn:: Not enough constructors .. tacv:: constructor @@ -539,34 +540,39 @@ sequence ``cut B. 2:apply H.`` where ``cut`` is described below. The terms in the @bindings_list are checked in the context where constructor is executed and not in the context where @apply is executed (the introductions are not taken into account). .. tacv:: split + :name: split This applies only if :g:`I` has a single constructor. It is then equivalent to :n:`constructor 1.`. It is typically used in the case of a conjunction :g:`A` :math:`\wedge` :g:`B`. -.. exn:: Not an inductive goal with 1 constructor. +.. exn:: Not an inductive goal with 1 constructor .. tacv:: exists @val + :name: exists This applies only if :g:`I` has a single constructor. It is then equivalent to :n:`intros; constructor 1 with @bindings_list.` It is typically used in the case of an existential quantification :math:`\exists`:g:`x, P(x).` -.. exn:: Not an inductive goal with 1 constructor. +.. exn:: Not an inductive goal with 1 constructor .. tacv:: exists @bindings_list This iteratively applies :n:`exists @bindings_list`. .. tacv:: left + :name: left + .. tacv:: right + :name: right These tactics apply only if :g:`I` has two constructors, for instance in the case of a disjunction :g:`A` :math:`\vee` :g:`B`. Then, they are respectively equivalent to ``constructor 1`` and ``constructor 2``. -.. exn:: Not an inductive goal with 2 constructors. +.. exn:: Not an inductive goal with 2 constructors .. tacv:: left with @bindings_list .. tacv:: right with @bindings_list @@ -577,15 +583,25 @@ sequence ``cut B. 2:apply H.`` where ``cut`` is described below. for the appropriate ``i``. .. tacv:: econstructor + :name: econstructor + .. tacv:: eexists + :name: eexists + .. tacv:: esplit + :name: esplit + .. tacv:: eleft + :name: eleft + .. tacv:: eright + :name: eright - These tactics and their variants behave like ``constructor``, ``exists``, - ``split``, ``left``, ``right`` and their variants but they introduce - existential variables instead of failing when the instantiation of a - variable cannot be found (cf. :tacn:`eapply` and :tacn:`apply`). + These tactics and their variants behave like :tacn:`constructor`, + :tacn:`exists`, :tacn:`split`, :tacn:`left`, :tacn:`right` and their variants + but they introduce existential variables instead of failing when the + instantiation of a variable cannot be found (cf. :tacn:`eapply` and + :tacn:`apply`). .. _managingthelocalcontext: @@ -598,7 +614,7 @@ Managing the local context This tactic applies to a goal that is either a product or starts with a let binder. If the goal is a product, the tactic implements the "Lam" rule given in -:ref:`TODO-4.2-Typing-rules` [1]_. If the goal starts with a let binder, then the +:ref:`Typing-rules` [1]_. If the goal starts with a let binder, then the tactic implements a mix of the "Let" and "Conv". If the current goal is a dependent product :math:`\forall` :g:`x:T, U` (resp @@ -616,7 +632,7 @@ the tactic ``intro`` applies the tactic ``hnf`` until the tactic ``intro`` can be applied or the goal is not head-reducible. .. exn:: No product even after head-reduction. -.. exn:: ident is already used. +.. exn:: @ident is already used. .. tacv:: intros @@ -632,14 +648,14 @@ be applied or the goal is not head-reducible. .. note:: If a name used by intro hides the base name of a global constant then the latter can still be referred to by a qualified name - (see :ref:`TODO-2.6.2-Qualified-names`). + (see :ref:`Qualified-names`). .. tacv:: intros {+ @ident}. This is equivalent to the composed tactic :n:`intro @ident; ... ; intro @ident`. More generally, the ``intros`` tactic takes a pattern as argument in order to introduce names for components of an inductive definition or to clear introduced hypotheses. This is - explained in :ref:`TODO-8.3.2`. + explained in :ref:`Managingthelocalcontext`. .. tacv:: intros until @ident @@ -827,15 +843,10 @@ quantification or an implication. so that all the arguments of the i-th constructors of the corresponding inductive type are introduced can be controlled with the following option: - .. cmd:: Set Bracketing Last Introduction Pattern. + .. opt:: Bracketing Last Introduction Pattern - Force completion, if needed, when the last introduction pattern is a - disjunctive or conjunctive pattern (this is the default). - - .. cmd:: Unset Bracketing Last Introduction Pattern. - - Deactivate completion when the last introduction pattern is a disjunctive or - conjunctive pattern. + Force completion, if needed, when the last introduction pattern is a + disjunctive or conjunctive pattern (on by default). .. tacn:: clear @ident :name: clear @@ -855,6 +866,7 @@ quantification or an implication. This is equivalent to :n:`clear @ident. ... clear @ident.` .. tacv:: clearbody @ident + :name: clearbody This tactic expects :n:`@ident` to be a local definition then clears its body. Otherwise said, this tactic turns a definition into an assumption. @@ -876,7 +888,7 @@ quantification or an implication. it. .. tacn:: revert {+ @ident} - :name: revert ... + :name: revert This applies to any goal with variables :n:`{+ @ident}`. It moves the hypotheses (possibly defined) to the goal, if this respects dependencies. This tactic is @@ -992,6 +1004,7 @@ The name of the hypothesis in the proof-term, however, is left unchanged. .. tacv:: eset (@ident {+ @binder} := @term ) in @goal_occurrences .. tacv:: eset @term in @goal_occurrences + :name: eset While the different variants of :tacn:`set` expect that no existential variables are generated by the tactic, :n:`eset` removes this constraint. In @@ -999,6 +1012,7 @@ The name of the hypothesis in the proof-term, however, is left unchanged. :tacn:`epose`, i.e. when the :`@term` does not occur in the goal. .. tacv:: remember @term as @ident + :name: remember This behaves as :n:`set (@ident:= @term ) in *` and using a logical (Leibniz’s) equality instead of a local definition. @@ -1016,6 +1030,8 @@ The name of the hypothesis in the proof-term, however, is left unchanged. .. tacv:: eremember @term as @ident .. tacv:: eremember @term as @ident in @goal_occurrences .. tacv:: eremember @term as @ident eqn:@ident + :name: eremember + While the different variants of :n:`remember` expect that no existential variables are generated by the tactic, :n:`eremember` removes this constraint. @@ -1067,7 +1083,7 @@ The name of the hypothesis in the proof-term, however, is left unchanged. This decomposes record types (inductive types with one constructor, like "and" and "exists" and those defined with the Record macro, see - :ref:`TODO-2.1`). + :ref:`record-types`). .. _controllingtheproofflow: @@ -1089,7 +1105,7 @@ Controlling the proof flow .. tacv:: assert form - This behaves as :n:`assert (@ident : form ) but :n:`@ident` is generated by + This behaves as :n:`assert (@ident : form)` but :n:`@ident` is generated by Coq. .. tacv:: assert form by tactic @@ -1098,6 +1114,7 @@ Controlling the proof flow generated by assert. .. exn:: Proof is not complete + :name: Proof is not complete (assert) .. tacv:: assert form as intro_pattern @@ -1121,6 +1138,7 @@ Controlling the proof flow .. exn:: Variable @ident is already declared .. tacv:: eassert form as intro_pattern by tactic + :name: eassert .. tacv:: assert (@ident := @term) @@ -1130,6 +1148,7 @@ Controlling the proof flow to prove it. .. tacv:: pose proof @term {? as intro_pattern} + :name: pose proof This tactic behaves like :n:`assert T {? as intro_pattern} by exact @term` where :g:`T` is the type of :g:`term`. In particular, @@ -1143,6 +1162,7 @@ Controlling the proof flow the tactic, :n:`epose proof` removes this constraint. .. tacv:: enough (@ident : form) + :name: enough This adds a new hypothesis of name :n:`@ident` asserting :n:`form` to the goal the tactic :n:`enough` is applied to. A new subgoal stating :n:`form` is @@ -1168,22 +1188,27 @@ Controlling the proof flow applied to all of them. .. tacv:: eenough (@ident : form) by tactic + :name: eenough + .. tacv:: eenough form by tactic + .. tacv:: eenough form as intro_pattern by tactic While the different variants of :n:`enough` expect that no existential variables are generated by the tactic, :n:`eenough` removes this constraint. -.. tacv:: cut form +.. tacv:: cut @form + :name: cut This tactic applies to any goal. It implements the non-dependent case of - the “App” rule given in :ref:`TODO-4.2`. (This is Modus Ponens inference + the “App” rule given in :ref:`typing-rules`. (This is Modus Ponens inference rule.) :n:`cut U` transforms the current goal :g:`T` into the two following subgoals: :g:`U -> T` and :g:`U`. The subgoal :g:`U -> T` comes first in the list of remaining subgoal to prove. .. tacv:: specialize (ident {* @term}) {? as intro_pattern} .. tacv:: specialize ident with @bindings_list {? as intro_pattern} + :name: specialize The tactic :n:`specialize` works on local hypothesis :n:`@ident`. The premises of this hypothesis (either universal quantifications or @@ -1236,7 +1261,7 @@ name of the variable (here :g:`n`) is chosen based on :g:`T`. This is equivalent to :n:`generalize @term` but it generalizes only over the specified occurrences of :n:`@term` (counting from left to right on the - expression printed using option :g:`Set Printing All`). + expression printed using option :opt:`Printing All`). .. tacv:: generalize @term as @ident @@ -1268,7 +1293,7 @@ name of the variable (here :g:`n`) is chosen based on :g:`T`. :n:`refine @term` (preferred alternative). .. note:: To be able to refer to an existential variable by name, the user - must have given the name explicitly (see :ref:`TODO-2.11`). + must have given the name explicitly (see :ref:`Existential-Variables`). .. note:: When you are referring to hypotheses which you did not name explicitly, be aware that Coq may make a different decision on how to @@ -1353,11 +1378,13 @@ goals cannot be closed with :g:`Qed` but only with :g:`Admitted`. then required to prove that False is indeed provable in the current context. This tactic is a macro for :n:`elimtype False`. +.. _CaseAnalysisAndInduction: + Case analysis and induction ------------------------------- The tactics presented in this section implement induction or case -analysis on inductive or co-inductive objects (see :ref:`TODO-4.5`). +analysis on inductive or co-inductive objects (see :ref:`inductive-definitions`). .. tacn:: destruct @term :name: destruct @@ -1423,6 +1450,7 @@ analysis on inductive or co-inductive objects (see :ref:`TODO-4.5`). dependent premises of the type of :n:`@term` (see :ref:`syntax of bindings <bindingslist>`). .. tacv:: edestruct @term + :name: edestruct This tactic behaves like :n:`destruct @term` except that it does not fail if the instance of a dependent premises of the type of :n:`@term` is not @@ -1449,6 +1477,7 @@ analysis on inductive or co-inductive objects (see :ref:`TODO-4.5`). the effects of the `with`, `as`, `eqn:`, `using`, and `in` clauses. .. tacv:: case term + :name: case The tactic :n:`case` is a more basic tactic to perform case analysis without recursion. It behaves as :n:`elim @term` but using a case-analysis @@ -1458,14 +1487,15 @@ analysis on inductive or co-inductive objects (see :ref:`TODO-4.5`). Analogous to :n:`elim @term with @bindings_list` above. -.. tacv:: ecase @term -.. tacv:: ecase @term with @bindings_list +.. tacv:: ecase @term {? with @bindings_list } + :name: ecase In case the type of :n:`@term` has dependent premises, or dependent premises whose values are not inferable from the :n:`with @bindings_list` clause, :n:`ecase` turns them into existential variables to be resolved later on. .. tacv:: simple destruct @ident + :name: simple destruct This tactic behaves as :n:`intros until @ident; case @ident` when :n:`@ident` is a quantified variable of the goal. @@ -1556,6 +1586,7 @@ analysis on inductive or co-inductive objects (see :ref:`TODO-4.5`). premises of the type of :n:`term` (see :ref:`bindings list <bindingslist>`). .. tacv:: einduction @term + :name: einduction This tactic behaves like :tacn:`induction` except that it does not fail if some dependent premise of the type of :n:`@term` is not inferable. Instead, @@ -1628,6 +1659,7 @@ analysis on inductive or co-inductive objects (see :ref:`TODO-4.5`). (see :ref:`bindings list <bindingslist>`). .. tacv:: eelim @term + :name: eelim In case the type of :n:`@term` has dependent premises, this turns them into existential variables to be resolved later on. @@ -1635,7 +1667,7 @@ analysis on inductive or co-inductive objects (see :ref:`TODO-4.5`). .. tacv:: elim @term using @term .. tacv:: elim @term using @term with @bindings_list - Allows the user to give explicitly an elimination predicate :n:`@term` that + Allows the user to give explicitly an induction principle :n:`@term` that is not the standard one for the underlying inductive type of :n:`@term`. The :n:`@bindings_list` clause allows instantiating premises of the type of :n:`@term`. @@ -1646,7 +1678,8 @@ analysis on inductive or co-inductive objects (see :ref:`TODO-4.5`). These are the most general forms of ``elim`` and ``eelim``. It combines the effects of the ``using`` clause and of the two uses of the ``with`` clause. -.. tacv:: elimtype form +.. tacv:: elimtype @form + :name: elimtype The argument :n:`form` must be inductively defined. :n:`elimtype I` is equivalent to :n:`cut I. intro Hn; elim Hn; clear Hn.` Therefore the @@ -1656,6 +1689,7 @@ analysis on inductive or co-inductive objects (see :ref:`TODO-4.5`). :n:`elimtype I; 2:exact t.` .. tacv:: simple induction @ident + :name: simple induction This tactic behaves as :n:`intros until @ident; elim @ident` when :n:`@ident` is a quantified variable of the goal. @@ -1740,13 +1774,14 @@ analysis on inductive or co-inductive objects (see :ref:`TODO-4.5`). other ones need not be further generalized. .. tacv:: dependent destruction @ident + :name: dependent destruction This performs the generalization of the instance :n:`@ident` but uses ``destruct`` instead of induction on the generalized hypothesis. This gives results equivalent to ``inversion`` or ``dependent inversion`` if the hypothesis is dependent. -See also :ref:`TODO-10.1-dependentinduction` for a larger example of ``dependent induction`` +See also the larger example of :tacn:`dependent induction` and an explanation of the underlying technique. .. tacn:: function induction (@qualid {+ @term}) @@ -1754,8 +1789,8 @@ and an explanation of the underlying technique. The tactic functional induction performs case analysis and induction following the definition of a function. It makes use of a principle - generated by ``Function`` (see :ref:`TODO-2.3-Advancedrecursivefunctions`) or - ``Functional Scheme`` (see :ref:`TODO-13.2-Generationofinductionschemeswithfunctionalscheme`). + generated by ``Function`` (see :ref:`advanced-recursive-functions`) or + ``Functional Scheme`` (see :ref:`functional-scheme`). Note that this tactic is only available after a .. example:: @@ -1781,22 +1816,22 @@ and an explanation of the underlying technique. :n:`functional induction (f x1 x2 x3)` is actually a wrapper for :n:`induction x1, x2, x3, (f x1 x2 x3) using @qualid` followed by a cleaning phase, where :n:`@qualid` is the induction principle registered for :g:`f` - (by the ``Function`` (see :ref:`TODO-2.3-Advancedrecursivefunctions`) or - ``Functional Scheme`` (see :ref:`TODO-13.2-Generationofinductionschemeswithfunctionalscheme`) + (by the ``Function`` (see :ref:`advanced-recursive-functions`) or + ``Functional Scheme`` (see :ref:`functional-scheme`) command) corresponding to the sort of the goal. Therefore ``functional induction`` may fail if the induction scheme :n:`@qualid` is not - defined. See also :ref:`TODO-2.3-Advancedrecursivefunctions` for the function + defined. See also :ref:`advanced-recursive-functions` for the function terms accepted by ``Function``. .. note:: There is a difference between obtaining an induction scheme - for a function by using :g:`Function` (see :ref:`TODO-2.3-Advancedrecursivefunctions`) + for a function by using :g:`Function` (see :ref:`advanced-recursive-functions`) and by using :g:`Functional Scheme` after a normal definition using - :g:`Fixpoint` or :g:`Definition`. See :ref:`TODO-2.3-Advancedrecursivefunctions` + :g:`Fixpoint` or :g:`Definition`. See :ref:`advanced-recursive-functions` for details. -See also: :ref:`TODO-2.3-Advancedrecursivefunctions` - :ref:`TODO-13.2-Generationofinductionschemeswithfunctionalscheme` +See also: :ref:`advanced-recursive-functions` + :ref:`functional-scheme` :tacn:`inversion` .. exn:: Cannot find induction information on @qualid @@ -1849,6 +1884,7 @@ See also: :ref:`TODO-2.3-Advancedrecursivefunctions` .. tacv:: ediscriminate @num .. tacv:: ediscriminate @term {? with @bindings_list} + :name: ediscriminate This works the same as ``discriminate`` but if the type of :n:`@term`, or the type of the hypothesis referred to by :n:`@num`, has uninstantiated @@ -1902,7 +1938,7 @@ injected object has a dependent type :g:`P` with its two instances in different types :g:`(P t`:sub:`1` :g:`... t`:sub:`n` :g:`)` and :g:`(P u`:sub:`1` :g:`... u`:sub:`n` :sub:`)`. If :g:`t`:sub:`1` and :g:`u`:sub:`1` are the same and have for type an inductive type for which a decidable -equality has been declared using the command ``Scheme Equality`` (see :ref:`TODO-13.1-GenerationofinductionprincipleswithScheme`), +equality has been declared using the command ``Scheme Equality`` (see :ref:`proofschemes-induction-principles`), the use of a sigma type is avoided. .. note:: @@ -1928,6 +1964,7 @@ the use of a sigma type is avoided. .. tacv:: einjection @num .. tacv:: einjection @term {? with @bindings_list} + :name: einjection This works the same as :n:`injection` but if the type of :n:`@term`, or the type of the hypothesis referred to by :n:`@num`, has uninstantiated @@ -1955,17 +1992,19 @@ the use of a sigma type is avoided. to the number of new equalities. The original equality is erased if it corresponds to an hypothesis. -It is possible to ensure that :n:`injection @term` erases the original -hypothesis and leaves the generated equalities in the context rather -than putting them as antecedents of the current goal, as if giving -:n:`injection @term as` (with an empty list of names). To obtain this -behavior, the option ``Set Structural Injection`` must be activated. This -option is off by default. +.. opt:: Structural Injection -By default, ``injection`` only creates new equalities between :n:`@terms` whose -type is in sort :g:`Type` or :g:`Set`, thus implementing a special behavior for -objects that are proofs of a statement in :g:`Prop`. This behavior can be -turned off by setting the option ``Set Keep Proof Equalities``. + This option ensure that :n:`injection @term` erases the original hypothesis + and leaves the generated equalities in the context rather than putting them + as antecedents of the current goal, as if giving :n:`injection @term as` + (with an empty list of names). This option is off by default. + +.. opt:: Keep Proof Equalities + + By default, :tacn:`injection` only creates new equalities between :n:`@terms` + whose type is in sort :g:`Type` or :g:`Set`, thus implementing a special + behavior for objects that are proofs of a statement in :g:`Prop`. This option + controls this behavior. .. tacn:: inversion @ident :name: inversion @@ -1984,15 +2023,15 @@ turned off by setting the option ``Set Keep Proof Equalities``. .. note:: As ``inversion`` proofs may be large in size, we recommend the user to stock the lemmas whenever the same instance needs to be - inverted several times. See :ref:`TODO-13.3-Generationofinversionprincipleswithderiveinversion`. + inverted several times. See :ref:`derive-inversion`. .. note:: Part of the behavior of the ``inversion`` tactic is to generate equalities between expressions that appeared in the hypothesis that is being processed. By default, no equalities are generated if they relate two proofs (i.e. equalities between :n:`@terms` whose type is in sort - :g:`Prop`). This behavior can be turned off by using the option ``Set Keep - Proof Equalities``. + :g:`Prop`). This behavior can be turned off by using the option + :opt`Keep Proof Equalities`. .. tacv:: inversion @num @@ -2117,6 +2156,7 @@ turned off by setting the option ``Set Keep Proof Equalities``. :n:`dependent inversion_clear @ident with @term`. .. tacv:: simple inversion @ident + :name: simple inversion It is a very primitive inversion tactic that derives all the necessary equalities but it does not simplify the constraints as ``inversion`` does. @@ -2300,7 +2340,7 @@ turned off by setting the option ``Set Keep Proof Equalities``. arguments are correct is done only at the time of registering the lemma in the environment. To know if the use of induction hypotheses is correct at some time of the interactive development of a proof, use - the command ``Guarded`` (see :ref:`TODO-7.3.2-Guarded`). + the command ``Guarded`` (see Section :ref:`requestinginformation`). .. tacv:: fix @ident @num with {+ (ident {+ @binder} [{struct @ident}] : @type)} @@ -2321,7 +2361,7 @@ turned off by setting the option ``Set Keep Proof Equalities``. done only at the time of registering the lemma in the environment. To know if the use of coinduction hypotheses is correct at some time of the interactive development of a proof, use the command ``Guarded`` - (see :ref:`TODO-7.3.2-Guarded`). + (see Section :ref:`requestinginformation`). .. tacv:: cofix @ident with {+ (@ident {+ @binder} : @type)} @@ -2335,7 +2375,7 @@ Rewriting expressions --------------------- These tactics use the equality :g:`eq:forall A:Type, A->A->Prop` defined in -file ``Logic.v`` (see :ref:`TODO-3.1.2-Logic`). The notation for :g:`eq T t u` is +file ``Logic.v`` (see :ref:`coq-library-logic`). The notation for :g:`eq T t u` is simply :g:`t=u` dropping the implicit type of :g:`t` and :g:`u`. .. tacn:: rewrite @term @@ -2417,6 +2457,7 @@ subgoals. leading to failure if these n rewrites are not possible. .. tacv:: erewrite @term + :name: erewrite This tactic works as :n:`rewrite @term` but turning unresolved bindings into existential variables, if any, instead of @@ -2463,6 +2504,7 @@ subgoals. clause argument must not contain any type of nor value of. .. tacv:: cutrewrite <- (@term = @term) + :cutrewrite: This tactic is deprecated. It acts like :n:`replace @term with @term`, or, equivalently as :n:`enough (@term = @term) as <-`. @@ -2506,30 +2548,30 @@ unfolded and cleared. context for which an equality of the form :n:`@ident = t` or :n:`t = @ident` or :n:`@ident := t` exists, with :n:`@ident` not occurring in `t`. - .. note:: - The behavior of subst can be controlled using option ``Set Regular Subst - Tactic.`` When this option is activated, subst also deals with the - following corner cases: + .. opt:: Regular Subst Tactic + + This option controls the behavior of :tacn:`subst`. When it is + activated, :tacn:`subst` also deals with the following corner cases: - + A context with ordered hypotheses :n:`@ident`:sub:`1` :n:`= @ident`:sub:`2` - and :n:`@ident`:sub:`1` :n:`= t`, or :n:`t′ = @ident`:sub:`1`` with `t′` not - a variable, and no other hypotheses of the form :n:`@ident`:sub:`2` :n:`= u` - or :n:`u = @ident`:sub:`2`; without the option, a second call to - subst would be necessary to replace :n:`@ident`:sub:`2` by `t` or - `t′` respectively. - + The presence of a recursive equation which without the option would - be a cause of failure of :tacn:`subst`. - + A context with cyclic dependencies as with hypotheses :n:`@ident`:sub:`1` :n:`= f @ident`:sub:`2` - and :n:`@ident`:sub:`2` :n:`= g @ident`:sub:`1` which without the - option would be a cause of failure of :tacn:`subst`. + + A context with ordered hypotheses :n:`@ident`:sub:`1` :n:`= @ident`:sub:`2` + and :n:`@ident`:sub:`1` :n:`= t`, or :n:`t′ = @ident`:sub:`1`` with `t′` not + a variable, and no other hypotheses of the form :n:`@ident`:sub:`2` :n:`= u` + or :n:`u = @ident`:sub:`2`; without the option, a second call to + subst would be necessary to replace :n:`@ident`:sub:`2` by `t` or + `t′` respectively. + + The presence of a recursive equation which without the option would + be a cause of failure of :tacn:`subst`. + + A context with cyclic dependencies as with hypotheses :n:`@ident`:sub:`1` :n:`= f @ident`:sub:`2` + and :n:`@ident`:sub:`2` :n:`= g @ident`:sub:`1` which without the + option would be a cause of failure of :tacn:`subst`. - Additionally, it prevents a local definition such as :n:`@ident := t` to be - unfolded which otherwise it would exceptionally unfold in configurations - containing hypotheses of the form :n:`@ident = u`, or :n:`u′ = @ident` - with `u′` not a variable. Finally, it preserves the initial order of - hypotheses, which without the option it may break. The option is on by - default. + Additionally, it prevents a local definition such as :n:`@ident := t` to be + unfolded which otherwise it would exceptionally unfold in configurations + containing hypotheses of the form :n:`@ident = u`, or :n:`u′ = @ident` + with `u′` not a variable. Finally, it preserves the initial order of + hypotheses, which without the option it may break. The option is on by + default. .. tacn:: stepl @term @@ -2543,30 +2585,37 @@ where `eq` is typically a setoid equality. The application of :n:`stepl @term` then replaces the goal by :n:`R @term @term` and adds a new goal stating :n:`eq @term @term`. -Lemmas are added to the database using the command ``Declare Left Step @term.`` +.. cmd:: Declare Left Step @term + + Adds :n:`@term` to the database used by :tacn:`stepl`. + The tactic is especially useful for parametric setoids which are not accepted as regular setoids for :tacn:`rewrite` and :tacn:`setoid_replace` (see -:ref:`TODO-27-Generalizedrewriting`). +:ref:`Generalizedrewriting`). .. tacv:: stepl @term by tactic - This applies :n:`stepl @term` then applies tactic to the second goal. + This applies :n:`stepl @term` then applies tactic to the second goal. .. tacv:: stepr @term stepr @term by tactic + :name: stepr + + This behaves as :tacn:`stepl` but on the right-hand-side of the binary + relation. Lemmas are expected to be of the form :g:`forall x y z, R x y -> eq + y z -> R x z`. - This behaves as :tacn:`stepl` but on the right-hand-side of the binary - relation. Lemmas are expected to be of the form :g:`forall x y z, R x y -> eq - y z -> R x z` and are registered using the command ``Declare Right Step - @term.`` + .. cmd:: Declare Right Step @term + + Adds :n:`@term` to the database used by :tacn:`stepr`. .. tacn:: change @term :name: change - This tactic applies to any goal. It implements the rule ``Conv`` given in - :ref:`TODO-4.4-Subtypingrules`. :g:`change U` replaces the current goal `T` - with `U` providing that `U` is well-formed and that `T` and `U` are - convertible. + This tactic applies to any goal. It implements the rule ``Conv`` given in + :ref:`subtyping-rules`. :g:`change U` replaces the current goal `T` + with `U` providing that `U` is well-formed and that `T` and `U` are + convertible. .. exn:: Not convertible @@ -2637,7 +2686,7 @@ the conversion in hypotheses :n:`{+ @ident}`. the normalization of the goal according to the specified flags. In correspondence with the kinds of reduction considered in Coq namely :math:`\beta` (reduction of functional application), :math:`\delta` - (unfolding of transparent constants, see :ref:`TODO-6.10.2-Transparent`), + (unfolding of transparent constants, see :ref:`vernac-controlling-the-reduction-strategies`), :math:`\iota` (reduction of pattern-matching over a constructed term, and unfolding of :g:`fix` and :g:`cofix` expressions) and :math:`\zeta` (contraction of local definitions), the @@ -2649,7 +2698,7 @@ the conversion in hypotheses :n:`{+ @ident}`. second case the constant to unfold to all but the ones explicitly mentioned. Notice that the ``delta`` flag does not apply to variables bound by a let-in construction inside the :n:`@term` itself (use here the ``zeta`` flag). In - any cases, opaque constants are not unfolded (see :ref:`TODO-6.10.1-Opaque`). + any cases, opaque constants are not unfolded (see :ref:`vernac-controlling-the-reduction-strategies`). Normalization according to the flags is done by first evaluating the head of the expression into a *weak-head* normal form, i.e. until the @@ -2704,6 +2753,7 @@ the conversion in hypotheses :n:`{+ @ident}`. and :n:`lazy beta delta -{+ @qualid} iota zeta`. .. tacv:: vm_compute + :name: vm_compute This tactic evaluates the goal using the optimized call-by-value evaluation bytecode-based virtual machine described in :cite:`CompiledStrongReduction`. @@ -2713,6 +2763,7 @@ the conversion in hypotheses :n:`{+ @ident}`. reflection-based tactics. .. tacv:: native_compute + :name: native_compute This tactic evaluates the goal by compilation to Objective Caml as described in :cite:`FullReduction`. If Coq is running in native code, it can be @@ -2768,7 +2819,7 @@ the conversion in hypotheses :n:`{+ @ident}`. :n:`hnf`. .. note:: - The :math:`\delta` rule only applies to transparent constants (see :ref:`TODO-6.10.1-Opaque` + The :math:`\delta` rule only applies to transparent constants (see :ref:`vernac-controlling-the-reduction-strategies` on transparency and opacity). .. tacn:: cbn @@ -2906,7 +2957,7 @@ the conversion in hypotheses :n:`{+ @ident}`. This tactic applies to any goal. The argument qualid must denote a defined transparent constant or local definition (see - :ref:`TODO-1.3.2-Definitions` and :ref:`TODO-6.10.2-Transparent`). The tactic + :ref:`gallina-definitions` and :ref:`vernac-controlling-the-reduction-strategies`). The tactic ``unfold`` applies the :math:`\delta` rule to each occurrence of the constant to which :n:`@qualid` refers in the current goal and then replaces it with its :math:`\beta`:math:`\iota`-normal form. @@ -2942,7 +2993,7 @@ the conversion in hypotheses :n:`{+ @ident}`. This is variant of :n:`unfold @string` where :n:`@string` gets its interpretation from the scope bound to the delimiting key :n:`key` - instead of its default interpretation (see :ref:`TODO-12.2.2-Localinterpretationrulesfornotations`). + instead of its default interpretation (see :ref:`Localinterpretationrulesfornotations`). .. tacv:: unfold {+, qualid_or_string at {+, @num}} This is the most general form, where :n:`qualid_or_string` is either a @@ -3103,7 +3154,7 @@ the :tacn:`auto` and :tacn:`trivial` tactics: .. opt:: Info Auto .. opt:: Debug Auto .. opt:: Info Trivial -.. opt:: Info Trivial +.. opt:: Debug Trivial See also: :ref:`The Hints Databases for auto and eauto <thehintsdatabasesforautoandeauto>` @@ -3258,188 +3309,203 @@ observationally different from the legacy one. The general command to add a hint to some databases :n:`{+ @ident}` is -.. cmd:: Hint hint_definition : {+ @ident} +.. cmd:: Hint @hint_definition : {+ @ident} -**Variants:** + .. cmdv:: Hint @hint_definition -.. cmd:: Hint hint_definition + No database name is given: the hint is registered in the core database. - No database name is given: the hint is registered in the core database. + .. cmdv:: Local Hint @hint_definition : {+ @ident} -.. cmd:: Local Hint hint_definition : {+ @ident} + This is used to declare hints that must not be exported to the other modules + that require and import the current module. Inside a section, the option + Local is useless since hints do not survive anyway to the closure of + sections. - This is used to declare hints that must not be exported to the other modules - that require and import the current module. Inside a section, the option - Local is useless since hints do not survive anyway to the closure of - sections. + .. cmdv:: Local Hint @hint_definition -.. cmd:: Local Hint hint_definition + Idem for the core database. - Idem for the core database. + .. cmdv:: Hint Resolve @term {? | {? @num} {? @pattern}} + :name: Hint Resolve -The ``hint_definition`` is one of the following expressions: + This command adds :n:`simple apply @term` to the hint list with the head + symbol of the type of :n:`@term`. The cost of that hint is the number of + subgoals generated by :n:`simple apply @term` or :n:`@num` if specified. The + associated :n:`@pattern` is inferred from the conclusion of the type of + :n:`@term` or the given :n:`@pattern` if specified. In case the inferred type + of :n:`@term` does not start with a product the tactic added in the hint list + is :n:`exact @term`. In case this type can however be reduced to a type + starting with a product, the tactic :n:`simple apply @term` is also stored in + the hints list. If the inferred type of :n:`@term` contains a dependent + quantification on a variable which occurs only in the premisses of the type + and not in its conclusion, no instance could be inferred for the variable by + unification with the goal. In this case, the hint is added to the hint list + of :tacn:`eauto` instead of the hint list of auto and a warning is printed. A + typical example of a hint that is used only by :tacn:`eauto` is a transitivity + lemma. -+ :n:`Resolve @term {? | {? @num} {? @pattern}}` - This command adds :n:`simple apply @term` to the hint list with the head symbol of the type of - :n:`@term`. The cost of that hint is the number of subgoals generated by - :n:`simple apply @term` or :n:`@num` if specified. The associated :n:`@pattern` - is inferred from the conclusion of the type of :n:`@term` or the given - :n:`@pattern` if specified. In case the inferred type of :n:`@term` does not - start with a product the tactic added in the hint list is :n:`exact @term`. - In case this type can however be reduced to a type starting with a product, - the tactic :n:`simple apply @term` is also stored in the hints list. If the - inferred type of :n:`@term` contains a dependent quantification on a variable - which occurs only in the premisses of the type and not in its conclusion, no - instance could be inferred for the variable by unification with the goal. In - this case, the hint is added to the hint list of :tacn:`eauto` instead of the - hint list of auto and a warning is printed. A typical example of a hint that - is used only by ``eauto`` is a transitivity lemma. + .. exn:: @term cannot be used as a hint - .. exn:: @term cannot be used as a hint + The head symbol of the type of :n:`@term` is a bound variable such that + this tactic cannot be associated to a constant. - The head symbol of the type of :n:`@term` is a bound variable such that - this tactic cannot be associated to a constant. + .. cmdv:: Hint Resolve {+ @term} - **Variants:** + Adds each :n:`Hint Resolve @term`. - + :n:`Resolve {+ @term}` - Adds each :n:`Resolve @term`. + .. cmdv:: Hint Resolve -> @term - + :n:`Resolve -> @term` - Adds the left-to-right implication of an equivalence as a hint (informally - the hint will be used as :n:`apply <- @term`, although as mentionned - before, the tactic actually used is a restricted version of ``apply``). + Adds the left-to-right implication of an equivalence as a hint (informally + the hint will be used as :n:`apply <- @term`, although as mentionned + before, the tactic actually used is a restricted version of + :tacn:`apply`). - + :n:`Resolve <- @term` - Adds the right-to-left implication of an equivalence as a hint. + .. cmdv:: Resolve <- @term -+ :n:`Immediate @term` - This command adds :n:`simple apply @term; trivial` to the hint list associated - with the head symbol of the type of :n:`@ident` in the given database. This - tactic will fail if all the subgoals generated by :n:`simple apply @term` are - not solved immediately by the ``trivial`` tactic (which only tries tactics - with cost 0).This command is useful for theorems such as the symmetry of - equality or :g:`n+1=m+1 -> n=m` that we may like to introduce with a limited - use in order to avoid useless proof-search.The cost of this tactic (which - never generates subgoals) is always 1, so that it is not used by ``trivial`` - itself. + Adds the right-to-left implication of an equivalence as a hint. - .. exn:: @term cannot be used as a hint + .. cmdv:: Hint Immediate @term + :name: Hint Immediate - **Variants:** + This command adds :n:`simple apply @term; trivial` to the hint list associated + with the head symbol of the type of :n:`@ident` in the given database. This + tactic will fail if all the subgoals generated by :n:`simple apply @term` are + not solved immediately by the ``trivial`` tactic (which only tries tactics + with cost 0).This command is useful for theorems such as the symmetry of + equality or :g:`n+1=m+1 -> n=m` that we may like to introduce with a limited + use in order to avoid useless proof-search. The cost of this tactic (which + never generates subgoals) is always 1, so that it is not used by :tacn:`trivial` + itself. - + :n:`Immediate {+ @term}` - Adds each :n:`Immediate @term`. + .. exn:: @term cannot be used as a hint -+ :n:`Constructors @ident` - If :n:`@ident` is an inductive type, this command adds all its constructors as - hints of type Resolve. Then, when the conclusion of current goal has the form - :n:`(@ident ...)`, ``auto`` will try to apply each constructor. + .. cmdv:: Immediate {+ @term} - .. exn:: @ident is not an inductive type + Adds each :n:`Hint Immediate @term`. - **Variants:** + .. cmdv:: Hint Constructors @ident + :name: Hint Constructors - + :n:`Constructors {+ @ident}` - Adds each :n:`Constructors @ident`. + If :n:`@ident` is an inductive type, this command adds all its constructors as + hints of type ``Resolve``. Then, when the conclusion of current goal has the form + :n:`(@ident ...)`, :tacn:`auto` will try to apply each constructor. -+ :n:`Unfold @qualid` - This adds the tactic :n:`unfold @qualid` to the hint list that will only be - used when the head constant of the goal is :n:`@ident`. - Its cost is 4. + .. exn:: @ident is not an inductive type - **Variants:** + .. cmdv:: Hint Constructors {+ @ident} - + :n:`Unfold {+ @ident}` - Adds each :n:`Unfold @ident`. + Adds each :n:`Hint Constructors @ident`. -+ :n:`Transparent`, :n:`Opaque @qualid` - This adds a transparency hint to the database, making :n:`@qualid` a - transparent or opaque constant during resolution. This information is used - during unification of the goal with any lemma in the database and inside the - discrimination network to relax or constrain it in the case of discriminated - databases. + .. cmdv:: Hint Unfold @qualid + :name: Hint Unfold - **Variants:** + This adds the tactic :n:`unfold @qualid` to the hint list that will only be + used when the head constant of the goal is :n:`@ident`. + Its cost is 4. - + :n:`Transparent`, :n:`Opaque {+ @ident}` - Declares each :n:`@ident` as a transparent or opaque constant. + .. cmdv:: Hint Unfold {+ @ident} -+ :n:`Extern @num {? @pattern} => tactic` - This hint type is to extend ``auto`` with tactics other than ``apply`` and - ``unfold``. For that, we must specify a cost, an optional :n:`@pattern` and a - :n:`tactic` to execute. Here is an example:: - - Hint Extern 4 (~(_ = _)) => discriminate. - - Now, when the head of the goal is a disequality, ``auto`` will try - discriminate if it does not manage to solve the goal with hints with a - cost less than 4. One can even use some sub-patterns of the pattern in - the tactic script. A sub-pattern is a question mark followed by an - identifier, like ``?X1`` or ``?X2``. Here is an example: - - .. example:: - .. coqtop:: reset all - - Require Import List. - Hint Extern 5 ({?X1 = ?X2} + {?X1 <> ?X2}) => generalize X1, X2; decide equality : eqdec. - Goal forall a b:list (nat * nat), {a = b} + {a <> b}. - Info 1 auto with eqdec. - -+ :n:`Cut @regexp` - - .. warning:: these hints currently only apply to typeclass - proof search and the ``typeclasses eauto`` tactic (:ref:`TODO-20.6.5-typeclasseseauto`). - - This command can be used to cut the proof-search tree according to a regular - expression matching paths to be cut. The grammar for regular expressions is - the following. Beware, there is no operator precedence during parsing, one can - check with ``Print HintDb`` to verify the current cut expression: - - .. productionlist:: `regexp` - e : ident hint or instance identifier - :|_ any hint - :| e\|e′ disjunction - :| e e′ sequence - :| e * Kleene star - :| emp empty - :| eps epsilon - :| ( e ) - - The `emp` regexp does not match any search path while `eps` - matches the empty path. During proof search, the path of - successive successful hints on a search branch is recorded, as a - list of identifiers for the hints (note Hint Extern’s do not have - an associated identifier). - Before applying any hint :n:`@ident` the current path `p` extended with - :n:`@ident` is matched against the current cut expression `c` associated to - the hint database. If matching succeeds, the hint is *not* applied. The - semantics of ``Hint Cut e`` is to set the cut expression to ``c | e``, the - initial cut expression being `emp`. - -+ :n:`Mode @qualid {* (+ | ! | -)}` - This sets an optional mode of use of the identifier :n:`@qualid`. When - proof-search faces a goal that ends in an application of :n:`@qualid` to - arguments :n:`@term ... @term`, the mode tells if the hints associated to - :n:`@qualid` can be applied or not. A mode specification is a list of n ``+``, - ``!`` or ``-`` items that specify if an argument of the identifier is to be - treated as an input (``+``), if its head only is an input (``!``) or an output - (``-``) of the identifier. For a mode to match a list of arguments, input - terms and input heads *must not* contain existential variables or be - existential variables respectively, while outputs can be any term. Multiple - modes can be declared for a single identifier, in that case only one mode - needs to match the arguments for the hints to be applied.The head of a term - is understood here as the applicative head, or the match or projection - scrutinee’s head, recursively, casts being ignored. ``Hint Mode`` is - especially useful for typeclasses, when one does not want to support default - instances and avoid ambiguity in general. Setting a parameter of a class as an - input forces proof-search to be driven by that index of the class, with ``!`` - giving more flexibility by allowing existentials to still appear deeper in the - index but not at its head. + Adds each :n:`Hint Unfold @ident`. -.. note:: - One can use an ``Extern`` hint with no pattern to do pattern-matching on - hypotheses using ``match goal`` with inside the tactic. + .. cmdv:: Hint %( Transparent %| Opaque %) @qualid + :name: Hint ( Transparent | Opaque ) + + This adds a transparency hint to the database, making :n:`@qualid` a + transparent or opaque constant during resolution. This information is used + during unification of the goal with any lemma in the database and inside the + discrimination network to relax or constrain it in the case of discriminated + databases. + + .. cmdv:: Hint %(Transparent | Opaque) {+ @ident} + + Declares each :n:`@ident` as a transparent or opaque constant. + + .. cmdv:: Hint Extern @num {? @pattern} => tactic + + This hint type is to extend :tacn:`auto` with tactics other than :tacn:`apply` and + :tacn:`unfold`. For that, we must specify a cost, an optional :n:`@pattern` and a + :n:`@tactic` to execute. + + .. example:: + + .. coqtop:: in + + Hint Extern 4 (~(_ = _)) => discriminate. + + Now, when the head of the goal is a disequality, ``auto`` will try + discriminate if it does not manage to solve the goal with hints with a + cost less than 4. One can even use some sub-patterns of the pattern in + the tactic script. A sub-pattern is a question mark followed by an + identifier, like ``?X1`` or ``?X2``. Here is an example: + + .. example:: + + .. coqtop:: reset all + + Require Import List. + Hint Extern 5 ({?X1 = ?X2} + {?X1 <> ?X2}) => generalize X1, X2; decide equality : eqdec. + Goal forall a b:list (nat * nat), {a = b} + {a <> b}. + Info 1 auto with eqdec. + + .. cmdv:: Hint Cut @regexp + + .. warning:: + + These hints currently only apply to typeclass proof search and the + :tacn:`typeclasses eauto` tactic. + + This command can be used to cut the proof-search tree according to a regular + expression matching paths to be cut. The grammar for regular expressions is + the following. Beware, there is no operator precedence during parsing, one can + check with :cmd:`Print HintDb` to verify the current cut expression: + + .. productionlist:: `regexp` + e : ident hint or instance identifier + :|_ any hint + :| e\|e′ disjunction + :| e e′ sequence + :| e * Kleene star + :| emp empty + :| eps epsilon + :| ( e ) + + The `emp` regexp does not match any search path while `eps` + matches the empty path. During proof search, the path of + successive successful hints on a search branch is recorded, as a + list of identifiers for the hints (note Hint Extern’s do not have + an associated identifier). + Before applying any hint :n:`@ident` the current path `p` extended with + :n:`@ident` is matched against the current cut expression `c` associated to + the hint database. If matching succeeds, the hint is *not* applied. The + semantics of ``Hint Cut e`` is to set the cut expression to ``c | e``, the + initial cut expression being `emp`. + + .. cmdv:: Hint Mode @qualid {* (+ | ! | -)} + + This sets an optional mode of use of the identifier :n:`@qualid`. When + proof-search faces a goal that ends in an application of :n:`@qualid` to + arguments :n:`@term ... @term`, the mode tells if the hints associated to + :n:`@qualid` can be applied or not. A mode specification is a list of n ``+``, + ``!`` or ``-`` items that specify if an argument of the identifier is to be + treated as an input (``+``), if its head only is an input (``!``) or an output + (``-``) of the identifier. For a mode to match a list of arguments, input + terms and input heads *must not* contain existential variables or be + existential variables respectively, while outputs can be any term. Multiple + modes can be declared for a single identifier, in that case only one mode + needs to match the arguments for the hints to be applied.The head of a term + is understood here as the applicative head, or the match or projection + scrutinee’s head, recursively, casts being ignored. ``Hint Mode`` is + especially useful for typeclasses, when one does not want to support default + instances and avoid ambiguity in general. Setting a parameter of a class as an + input forces proof-search to be driven by that index of the class, with ``!`` + giving more flexibility by allowing existentials to still appear deeper in the + index but not at its head. + + .. note:: + + One can use an ``Extern`` hint with no pattern to do pattern-matching on + hypotheses using ``match goal`` with inside the tactic. Hint databases defined in the Coq standard library @@ -3521,7 +3587,7 @@ at every moment. (left to right). Notice that the rewriting bases are distinct from the ``auto`` hint bases and thatauto does not take them into account. - This command is synchronous with the section mechanism (see :ref:`TODO-2.4-Sectionmechanism`): + This command is synchronous with the section mechanism (see :ref:`section-mechanism`): when closing a section, all aliases created by ``Hint Rewrite`` in that section are lost. Conversely, when loading a module, all ``Hint Rewrite`` declarations at the global level of that module are loaded. @@ -3573,69 +3639,65 @@ We propose a smooth transitional path by providing the ``Loose Hint Behavior`` option which accepts three flags allowing for a fine-grained handling of non-imported hints. -**Variants:** +.. opt:: Loose Hint Behavior %( "Lax" %| "Warn" %| "Strict" %) -.. cmd:: Set Loose Hint Behavior "Lax" + This option accepts three values, which control the behavior of hints w.r.t. + :cmd:`Import`: - This is the default, and corresponds to the historical behavior, that - is, hints defined outside of a section have a global scope. + - "Lax": this is the default, and corresponds to the historical behavior, + that is, hints defined outside of a section have a global scope. -.. cmd:: Set Loose Hint Behavior "Warn" + - "Warn": outputs a warning when a non-imported hint is used. Note that this + is an over-approximation, because a hint may be triggered by a run that + will eventually fail and backtrack, resulting in the hint not being + actually useful for the proof. - When set, it outputs a warning when a non-imported hint is used. Note that - this is an over-approximation, because a hint may be triggered by a run that - will eventually fail and backtrack, resulting in the hint not being actually - useful for the proof. + - "Strict": changes the behavior of an unloaded hint to a immediate fail + tactic, allowing to emulate an import-scoped hint mechanism. -.. cmd:: Set Loose Hint Behavior "Strict" - - When set, it changes the behavior of an unloaded hint to a immediate fail - tactic, allowing to emulate an import-scoped hint mechanism. +.. _tactics-implicit-automation: Setting implicit automation tactics ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -.. cmd:: Proof with tactic +.. cmd:: Proof with @tactic This command may be used to start a proof. It defines a default tactic to be used each time a tactic command ``tactic``:sub:`1` is ended by ``...``. In this case the tactic command typed by the user is equivalent to ``tactic``:sub:`1` ``;tactic``. -See also: Proof. in :ref:`TODO-7.1.4-Proofterm`. - -**Variants:** + See also: ``Proof.`` in :ref:`proof-editing-mode`. -.. cmd:: Proof with tactic using {+ @ident} - Combines in a single line ``Proof with`` and ``Proof using``, see :ref:`TODO-7.1.5-Proofusing` + .. cmdv:: Proof with tactic using {+ @ident} -.. cmd:: Proof using {+ @ident} with tactic + Combines in a single line ``Proof with`` and ``Proof using``, see :ref:`proof-editing-mode` - Combines in a single line ``Proof with`` and ``Proof using``, see :ref:`TODO-7.1.5-Proofusing` + .. cmdv:: Proof using {+ @ident} with @tactic -.. cmd:: Declare Implicit Tactic tactic + Combines in a single line ``Proof with`` and ``Proof using``, see :ref:`proof-editing-mode` - This command declares a tactic to be used to solve implicit arguments - that Coq does not know how to solve by unification. It is used every - time the term argument of a tactic has one of its holes not fully - resolved. + .. cmd:: Declare Implicit Tactic @tactic -Here is an example: + This command declares a tactic to be used to solve implicit arguments + that Coq does not know how to solve by unification. It is used every + time the term argument of a tactic has one of its holes not fully + resolved. -.. example:: + .. example:: - .. coqtop:: all + .. coqtop:: all - Parameter quo : nat -> forall n:nat, n<>0 -> nat. - Notation "x // y" := (quo x y _) (at level 40). - Declare Implicit Tactic assumption. - Goal forall n m, m<>0 -> { q:nat & { r | q * m + r = n } }. - intros. - exists (n // m). + Parameter quo : nat -> forall n:nat, n<>0 -> nat. + Notation "x // y" := (quo x y _) (at level 40). + Declare Implicit Tactic assumption. + Goal forall n m, m<>0 -> { q:nat & { r | q * m + r = n } }. + intros. + exists (n // m). - The tactic ``exists (n // m)`` did not fail. The hole was solved - by ``assumption`` so that it behaved as ``exists (quo n m H)``. + The tactic ``exists (n // m)`` did not fail. The hole was solved + by ``assumption`` so that it behaved as ``exists (quo n m H)``. .. _decisionprocedures: @@ -3680,11 +3742,12 @@ Therefore, the use of :tacn:`intros` in the previous proof is unnecessary. an instantiation of `x` is necessary. .. tacv:: dtauto + :name: dtauto - While :tacn:`tauto` recognizes inductively defined connectives isomorphic to - the standard connective ``and, prod, or, sum, False, Empty_set, unit, True``, - :tacn:`dtauto` recognizes also all inductive types with one constructors and - no indices, i.e. record-style connectives. + While :tacn:`tauto` recognizes inductively defined connectives isomorphic to + the standard connective ``and, prod, or, sum, False, Empty_set, unit, True``, + :tacn:`dtauto` recognizes also all inductive types with one constructors and + no indices, i.e. record-style connectives. .. tacn:: intuition @tactic :name: intuition @@ -3713,7 +3776,7 @@ and then uses :tacn:`auto` which completes the proof. Originally due to César Muñoz, these tactics (:tacn:`tauto` and :tacn:`intuition`) have been completely re-engineered by David Delahaye using -mainly the tactic language (see :ref:`TODO-9-thetacticlanguage`). The code is +mainly the tactic language (see :ref:`ltac`). The code is now much shorter and a significant increase in performance has been noticed. The general behavior with respect to dependent types, unfolding and introductions has slightly changed to get clearer semantics. This may lead to @@ -3730,17 +3793,10 @@ some incompatibilities. Empty_set, unit, True``, :tacn:`dintuition` recognizes also all inductive types with one constructors and no indices, i.e. record-style connectives. -Some aspects of the tactic :tacn:`intuition` can be controlled using options. -To avoid that inner negations which do not need to be unfolded are -unfolded, use: - -.. cmd:: Unset Intuition Negation Unfolding +.. opt:: Intuition Negation Unfolding - -To do that all negations of the goal are unfolded even inner ones -(this is the default), use: - -.. cmd:: Set Intuition Negation Unfolding + Controls whether :tacn:`intuition` unfolds inner negations which do not need + to be unfolded. This option is on by default. .. tacn:: rtauto :name: rtauto @@ -3764,14 +3820,15 @@ first- order reasoning, written by Pierre Corbineau. It is not restricted to usual logical connectives but instead may reason about any first-order class inductive definition. -The default tactic used by :tacn:`firstorder` when no rule applies is :g:`auto -with \*`, it can be reset locally or globally using the ``Set Firstorder -Solver`` tactic vernacular command and printed using ``Print Firstorder -Solver``. +.. opt:: Firstorder Solver + + The default tactic used by :tacn:`firstorder` when no rule applies is + :g:`auto with *`, it can be reset locally or globally using this option and + printed using :cmd:`Print Firstorder Solver`. .. tacv:: firstorder @tactic - Tries to solve the goal with :n:`@tactic` when no logical rule may apply. + Tries to solve the goal with :n:`@tactic` when no logical rule may apply. .. tacv:: firstorder using {+ @qualid} @@ -3788,8 +3845,9 @@ Solver``. This combines the effects of the different variants of :tacn:`firstorder`. -Proof-search is bounded by a depth parameter which can be set by -typing the ``Set Firstorder Depth n`` vernacular command. +.. opt:: Firstorder Depth @natural + + This option controls the proof-search depth bound. .. tacn:: congruence :name: congruence @@ -3878,7 +3936,7 @@ succeeds, and results in an error otherwise. .. tacv:: unify @term @term with @ident Unification takes the transparency information defined in the hint database - :n:`@ident` into account (see :ref:`the hints databases for auto and eauto <the-hints-databases-for-auto-and-eauto>`). + :n:`@ident` into account (see :ref:`the hints databases for auto and eauto <thehintsdatabasesforautoandeauto>`). .. tacn:: is_evar @term :name: is_evar @@ -4009,6 +4067,7 @@ symbol :g:`=`. .. tacv:: esimplify_eq @num .. tacv:: esimplify_eq @term {? with @bindings_list} + :name: esimplify_eq This works the same as ``simplify_eq`` but if the type of :n:`@term`, or the type of the hypothesis referred to by :n:`@num`, has uninstantiated @@ -4020,7 +4079,7 @@ symbol :g:`=`. :n:`intro @ident; simplify_eq @ident`. .. tacn:: dependent rewrite -> @ident - :name: dependent rewrite -> + :name: dependent rewrite This tactic applies to any goal. If :n:`@ident` has type :g:`(existT B a b)=(existT B a' b')` in the local context (i.e. each @@ -4044,7 +4103,7 @@ Inversion :tacn:`functional inversion` is a tactic that performs inversion on hypothesis :n:`@ident` of the form :n:`@qualid {+ @term} = @term` or :n:`@term = @qualid {+ @term}` where :n:`@qualid` must have been defined using Function (see -:ref:`TODO-2.3-advancedrecursivefunctions`). Note that this tactic is only +:ref:`advanced-recursive-functions`). Note that this tactic is only available after a ``Require Import FunInd``. @@ -4077,7 +4136,7 @@ This kind of inversion has nothing to do with the tactic :tacn:`inversion` above. This tactic does :g:`change (@ident t)`, where `t` is a term built in order to ensure the convertibility. In other words, it does inversion of the function :n:`@ident`. This function must be a fixpoint on a simple recursive -datatype: see :ref:`TODO-10.3-quote` for the full details. +datatype: see :ref:`quote` for the full details. .. exn:: quote: not a simple fixpoint @@ -4109,6 +4168,8 @@ using the ``Require Import`` command. Use ``classical_right`` to prove the right part of the disjunction with the assumption that the negation of left part holds. +.. _tactics-automatizing: + Automatizing ------------ @@ -4148,7 +4209,7 @@ formulas built with `~`, `\/`, `/\`, `->` on top of equalities, inequalities and disequalities on both the type :g:`nat` of natural numbers and :g:`Z` of binary integers. This tactic must be loaded by the command ``Require Import Omega``. See the additional documentation about omega -(see Chapter :ref:`TODO-21-omega`). +(see Chapter :ref:`omega`). .. tacn:: ring @@ -4168,7 +4229,7 @@ given in the conclusion of the goal by their normal forms. If no term is given, then the conclusion should be an equation and both hand sides are normalized. -See :ref:`TODO-Chapter-25-Theringandfieldtacticfamilies` for more information on +See :ref:`Theringandfieldtacticfamilies` for more information on the tactic and how to declare new ring structures. All declared field structures can be printed with the ``Print Rings`` command. @@ -4194,7 +4255,7 @@ denominators. So it produces an equation without division nor inverse. All of these 3 tactics may generate a subgoal in order to prove that denominators are different from zero. -See :ref:`TODO-Chapter-25-Theringandfieldtacticfamilies` for more information on the tactic and how to +See :ref:`Theringandfieldtacticfamilies` for more information on the tactic and how to declare new field structures. All declared field structures can be printed with the Print Fields command. @@ -4286,7 +4347,7 @@ This tactics reverses the list of the focused goals. This tactic moves all goals under focus to a shelf. While on the shelf, goals will not be focused on. They can be solved by unification, or they can be called back into focus with the command - :tacn:`Unshelve`. + :cmd:`Unshelve`. .. tacv:: shelve_unifiable @@ -4302,8 +4363,7 @@ This tactics reverses the list of the focused goals. all:shelve_unifiable. reflexivity. -.. tacn:: Unshelve - :name: Unshelve +.. cmd:: Unshelve This command moves all the goals on the shelf (see :tacn:`shelve`) from the shelf into focus, by appending them to the end of the current @@ -4334,11 +4394,11 @@ A simple example has more value than a long explanation: The tactics macros are synchronous with the Coq section mechanism: a tactic definition is deleted from the current environment when you -close the section (see also :ref:`TODO-2.4Sectionmechanism`) where it was +close the section (see also :ref:`section-mechanism`) where it was defined. If you want that a tactic macro defined in a module is usable in the modules that require it, you should put it outside of any section. -:ref:`TODO-9-Thetacticlanguage` gives examples of more complex +:ref:`ltac` gives examples of more complex user-defined tactics. .. [1] Actually, only the second subgoal will be generated since the diff --git a/doc/sphinx/proof-engine/vernacular-commands.rst b/doc/sphinx/proof-engine/vernacular-commands.rst new file mode 100644 index 0000000000..692ff294a6 --- /dev/null +++ b/doc/sphinx/proof-engine/vernacular-commands.rst @@ -0,0 +1,1357 @@ +.. include:: ../preamble.rst +.. include:: ../replaces.rst + +.. _vernacularcommands: + +Vernacular commands +============================= + +.. _displaying: + +Displaying +-------------- + + +.. _Print: + +.. cmd:: Print @qualid. + +This command displays on the screen information about the declared or +defined object referred by :n:`@qualid`. + + +Error messages: + + +.. exn:: @qualid not a defined object + +.. exn:: Universe instance should have length :n:`num`. + +.. exn:: This object does not support universe names. + + +Variants: + + +.. cmdv:: Print Term @qualid. + +This is a synonym to ``Print`` :n:`@qualid` when :n:`@qualid` +denotes a global constant. + +.. cmdv:: About @qualid. + :name: About + +This displays various information about the object +denoted by :n:`@qualid`: its kind (module, constant, assumption, inductive, +constructor, abbreviation, …), long name, type, implicit arguments and +argument scopes. It does not print the body of definitions or proofs. + +.. cmdv:: Print @qualid\@@name + +This locally renames the polymorphic universes of :n:`@qualid`. +An underscore means the raw universe is printed. +This form can be used with ``Print Term`` and ``About``. + +.. cmd:: Print All. + +This command displays information about the current state of the +environment, including sections and modules. + + +Variants: + + +.. cmdv:: Inspect @num. + :name: Inspect + +This command displays the :n:`@num` last objects of the +current environment, including sections and modules. + +.. cmdv:: Print Section @ident. + +The name :n:`@ident` should correspond to a currently open section, +this command displays the objects defined since the beginning of this +section. + + +.. _flags-options-tables: + +Flags, Options and Tables +----------------------------- + +|Coq| configurability is based on flags (e.g. :opt:`Printing All`), options +(e.g. :opt:`Printing Width`), or tables (e.g. :cmd:`Add Printing Record`). The +names of flags, options and tables are made of non-empty sequences of +identifiers (conventionally with capital initial letter). The general commands +handling flags, options and tables are given below. + +.. TODO : flag is not a syntax entry + +.. cmd:: Set @flag. + +This command switches :n:`@flag` on. The original state of :n:`@flag` is restored +when the current module ends. + +Variants: + +.. cmdv:: Local Set @flag. + +This command switches :n:`@flag` on. The original state +of :n:`@flag` is restored when the current *section* ends. + +.. cmdv:: Global Set @flag. + +This command switches :n:`@flag` on. The original state +of :n:`@flag` is *not* restored at the end of the module. Additionally, if +set in a file, :n:`@flag` is switched on when the file is `Require`-d. + +.. cmdv:: Export Set @flag. + + This command switches :n:`@flag` on. The original state + of :n:`@flag` is restored at the end of the current module, but :n:`@flag` + is switched on when this module is imported. + + +.. cmd:: Unset @flag. + +This command switches :n:`@flag` off. The original state of :n:`@flag` is restored +when the current module ends. + + +Variants: + +.. cmdv:: Local Unset @flag. + +This command switches :n:`@flag` off. The original +state of :n:`@flag` is restored when the current *section* ends. + +.. cmdv:: Global Unset @flag. + +This command switches :n:`@flag` off. The original +state of :n:`@flag` is *not* restored at the end of the module. Additionally, +if set in a file, :n:`@flag` is switched off when the file is `Require`-d. + +.. cmdv:: Export Unset @flag. + + This command switches :n:`@flag` off. The original state + of :n:`@flag` is restored at the end of the current module, but :n:`@flag` + is switched off when this module is imported. + + +.. cmd:: Test @flag. + +This command prints whether :n:`@flag` is on or off. + + +.. cmd:: Set @option @value. + +This command sets :n:`@option` to :n:`@value`. The original value of ` option` is +restored when the current module ends. + + +Variants: + +.. TODO : option and value are not syntax entries + +.. cmdv:: Local Set @option @value. + +This command sets :n:`@option` to :n:`@value`. The +original value of :n:`@option` is restored at the end of the module. + +.. cmdv:: Global Set @option @value. + +This command sets :n:`@option` to :n:`@value`. The +original value of :n:`@option` is *not* restored at the end of the module. +Additionally, if set in a file, :n:`@option` is set to value when the file +is `Require`-d. + +.. cmdv:: Export Set @option. + + This command set :n:`@option` to :n:`@value`. The original state + of :n:`@option` is restored at the end of the current module, but :n:`@option` + is set to :n:`@value` when this module is imported. + + +.. cmd:: Unset @option. + + This command turns off :n:`@option`. + + +Variants: + + +.. cmdv:: Local Unset @option. + + This command turns off :n:`@option`. The original state of :n:`@option` is restored when the current + *section* ends. + +.. cmdv:: Global Unset @option. + + This command turns off :n:`@option`. The original state of :n:`@option` is *not* restored at the end of the + module. Additionally, if unset in a file, :n:`@option` is reset to its + default value when the file is `Require`-d. + +.. cmdv:: Export Unset @option. + + This command turns off :n:`@option`. The original state of :n:`@option` is restored at the end of the + current module, but :n:`@option` is set to its default value when this module + is imported. + + +.. cmd:: Test @option. + +This command prints the current value of :n:`@option`. + + +.. TODO : table is not a syntax entry + +.. cmd:: Add @table @value. + :name: Add `table` `value` + +.. cmd:: Remove @table @value. + :name: Remove `table` `value` + +.. cmd:: Test @table @value. + :name: Test `table` `value` + +.. cmd:: Test @table for @value. + :name: Test `table` for `value` + +.. cmd:: Print Table @table. + +These are general commands for tables. + +.. cmd:: Print Options. + +This command lists all available flags, options and tables. + + +Variants: + + +.. cmdv:: Print Tables. + +This is a synonymous of ``Print Options``. + + +.. _requests-to-the-environment: + +Requests to the environment +------------------------------- + +.. cmd:: Check @term. + +This command displays the type of :n:`@term`. When called in proof mode, the +term is checked in the local context of the current subgoal. + + +Variants: + +.. TODO : selector is not a syntax entry + +.. cmdv:: @selector: Check @term. + +specifies on which subgoal to perform typing +(see Section :ref:`invocation-of-tactics`). + +.. TODO : convtactic is not a syntax entry + +.. cmd:: Eval @convtactic in @term. + +This command performs the specified reduction on :n:`@term`, and displays +the resulting term with its type. The term to be reduced may depend on +hypothesis introduced in the first subgoal (if a proof is in +progress). + + +See also: Section :ref:`performingcomputations`. + + +.. cmd:: Compute @term. + +This command performs a call-by-value evaluation of term by using the +bytecode-based virtual machine. It is a shortcut for ``Eval vm_compute in`` +:n:`@term`. + + +See also: Section :ref:`performingcomputations`. + + +.. cmd::Extraction @term. + +This command displays the extracted term from :n:`@term`. The extraction is +processed according to the distinction between :g:`Set` and :g:`Prop`; that is +to say, between logical and computational content (see Section :ref:`sorts`). +The extracted term is displayed in OCaml syntax, where global identifiers are +still displayed as in |Coq| terms. + + +Variants: + + +.. cmdv:: Recursive Extraction {+ @qualid }. + +Recursively extracts all +the material needed for the extraction of the qualified identifiers. + + +See also: Chapter :ref:`extraction`. + + +.. cmd:: Print Assumptions @qualid. + +This commands display all the assumptions (axioms, parameters and +variables) a theorem or definition depends on. Especially, it informs +on the assumptions with respect to which the validity of a theorem +relies. + + +Variants: + + +.. cmdv:: Print Opaque Dependencies @qualid. + +Displays the set of opaque constants :n:`@qualid` relies on in addition to +the assumptions. + +.. cmdv:: Print Transparent Dependencies @qualid. + +Displays the set of +transparent constants :n:`@qualid` relies on in addition to the assumptions. + +.. cmdv:: Print All Dependencies @qualid. + +Displays all assumptions and constants :n:`@qualid` relies on. + + + +.. cmd:: Search @qualid. + +This command displays the name and type of all objects (hypothesis of +the current goal, theorems, axioms, etc) of the current context whose +statement contains :n:`@qualid`. This command is useful to remind the user +of the name of library lemmas. + + +Error messages: + + +.. exn:: The reference @qualid was not found in the current environment + +There is no constant in the environment named qualid. + +Variants: + +.. cmdv:: Search @string. + +If :n:`@string` is a valid identifier, this command +displays the name and type of all objects (theorems, axioms, etc) of +the current context whose name contains string. If string is a +notation’s string denoting some reference :n:`@qualid` (referred to by its +main symbol as in `"+"` or by its notation’s string as in `"_ + _"` or +`"_ 'U' _"`, see Section :ref:`notations`), the command works like ``Search`` :n:`@qualid`. + +.. cmdv:: Search @string%@key. + +The string string must be a notation or the main +symbol of a notation which is then interpreted in the scope bound to +the delimiting key :n:`@key` (see Section :ref:`LocalInterpretationRulesForNotations`). + +.. cmdv:: Search @term_pattern. + +This searches for all statements or types of +definition that contains a subterm that matches the pattern +`term_pattern` (holes of the pattern are either denoted by `_` or by +`?ident` when non linear patterns are expected). + +.. cmdv:: Search { + [-]@term_pattern_string }. + +where +:n:`@term_pattern_string` is a term_pattern, a string, or a string followed +by a scope delimiting key `%key`. This generalization of ``Search`` searches +for all objects whose statement or type contains a subterm matching +:n:`@term_pattern` (or :n:`@qualid` if :n:`@string` is the notation for a reference +qualid) and whose name contains all string of the request that +correspond to valid identifiers. If a term_pattern or a string is +prefixed by `-`, the search excludes the objects that mention that +term_pattern or that string. + +.. cmdv:: Search @term_pattern_string … @term_pattern_string inside {+ @qualid } . + +This restricts the search to constructions defined in the modules named by the given :n:`qualid` sequence. + +.. cmdv:: Search @term_pattern_string … @term_pattern_string outside {+ @qualid }. + +This restricts the search to constructions not defined in the modules named by the given :n:`qualid` sequence. + +.. cmdv:: @selector: Search [-]@term_pattern_string … [-]@term_pattern_string. + +This specifies the goal on which to search hypothesis (see +Section :ref:`invocation-of-tactics`). +By default the 1st goal is searched. This variant can +be combined with other variants presented here. + + +.. coqtop:: in + + Require Import ZArith. + +.. coqtop:: all + + Search Z.mul Z.add "distr". + + Search "+"%Z "*"%Z "distr" -positive -Prop. + + Search (?x * _ + ?x * _)%Z outside OmegaLemmas. + +.. note:: Up to |Coq| version 8.4, ``Search`` had the behavior of current + ``SearchHead`` and the behavior of current Search was obtained with + command ``SearchAbout``. For compatibility, the deprecated name + SearchAbout can still be used as a synonym of Search. For + compatibility, the list of objects to search when using ``SearchAbout`` + may also be enclosed by optional ``[ ]`` delimiters. + + +.. cmd:: SearchHead @term. + +This command displays the name and type of all hypothesis of the +current goal (if any) and theorems of the current context whose +statement’s conclusion has the form `(term t1 .. tn)`. This command is +useful to remind the user of the name of library lemmas. + + + +.. coqtop:: reset all + + SearchHead le. + + SearchHead (@eq bool). + + +Variants: + +.. cmdv:: SearchHead @term inside {+ @qualid }. + +This restricts the search to constructions defined in the modules named by the given :n:`qualid` sequence. + +.. cmdv:: SearchHead term outside {+ @qualid }. + +This restricts the search to constructions not defined in the modules named by the given :n:`qualid` sequence. + +Error messages: + +.. exn:: Module/section @qualid not found + +No module :n:`@qualid` has been required +(see Section :ref:`compiled-files`). + +.. cmdv:: @selector: SearchHead @term. + +This specifies the goal on which to +search hypothesis (see Section :ref:`invocation-of-tactics`). +By default the 1st goal is +searched. This variant can be combined with other variants presented +here. + +.. note:: Up to |Coq| version 8.4, ``SearchHead`` was named ``Search``. + + +.. cmd:: SearchPattern @term. + +This command displays the name and type of all hypothesis of the +current goal (if any) and theorems of the current context whose +statement’s conclusion or last hypothesis and conclusion matches the +expressionterm where holes in the latter are denoted by `_`. +It is a +variant of Search @term_pattern that does not look for subterms but +searches for statements whose conclusion has exactly the expected +form, or whose statement finishes by the given series of +hypothesis/conclusion. + +.. coqtop:: in + + Require Import Arith. + +.. coqtop:: all + + SearchPattern (_ + _ = _ + _). + + SearchPattern (nat -> bool). + + SearchPattern (forall l : list _, _ l l). + +Patterns need not be linear: you can express that the same expression +must occur in two places by using pattern variables `?ident`. + + +.. coqtop:: all + + SearchPattern (?X1 + _ = _ + ?X1). + +Variants: + + +.. cmdv:: SearchPattern @term inside {+ @qualid } . + +This restricts the search to constructions defined in the modules named by the given :n:`qualid` sequence. + +.. cmdv:: SearchPattern @term outside {+ @qualid }. + +This restricts the search to constructions not defined in the modules named by the given :n:`qualid` sequence. + +.. cmdv:: @selector: SearchPattern @term. + +This specifies the goal on which to +search hypothesis (see Section :ref:`invocation-of-tactics`). By default the 1st goal is +searched. This variant can be combined with other variants presented +here. + + + +.. cmdv:: SearchRewrite @term. + +This command displays the name and type of all hypothesis of the +current goal (if any) and theorems of the current context whose +statement’s conclusion is an equality of which one side matches the +expression term. Holes in term are denoted by “_”. + +.. coqtop:: in + + Require Import Arith. + +.. coqtop:: all + + SearchRewrite (_ + _ + _). + +Variants: + + +.. cmdv:: SearchRewrite term inside {+ @qualid }. + +This restricts the search to constructions defined in the modules named by the given :n:`qualid` sequence. + +.. cmdv:: SearchRewrite @term outside {+ @qualid }. + +This restricts the search to constructions not defined in the modules named by the given :n:`qualid` sequence. + +.. cmdv:: @selector: SearchRewrite @term. + +This specifies the goal on which to +search hypothesis (see Section :ref:`invocation-of-tactics`). By default the 1st goal is +searched. This variant can be combined with other variants presented +here. + +.. note:: + + For the ``Search``, ``SearchHead``, ``SearchPattern`` and ``SearchRewrite`` + queries, it + is possible to globally filter the search results via the command + ``Add Search Blacklist`` :n:`@substring`. A lemma whose fully-qualified name + contains any of the declared substrings will be removed from the + search results. The default blacklisted substrings are ``_subproof`` + ``Private_``. The command ``Remove Search Blacklist ...`` allows expunging + this blacklist. + + +.. cmd:: Locate @qualid. + +This command displays the full name of objects whose name is a prefix +of the qualified identifier :n:`@qualid`, and consequently the |Coq| module in +which they are defined. It searches for objects from the different +qualified name spaces of |Coq|: terms, modules, Ltac, etc. + +.. coqtop:: none + + Set Printing Depth 50. + +.. coqtop:: all + + Locate nat. + + Locate Datatypes.O. + + Locate Init.Datatypes.O. + + Locate Coq.Init.Datatypes.O. + + Locate I.Dont.Exist. + +Variants: + + +.. cmdv:: Locate Term @qualid. + +As Locate but restricted to terms. + +.. cmdv:: Locate Module @qualid. + +As Locate but restricted to modules. + +.. cmdv:: Locate Ltac @qualid. + +As Locate but restricted to tactics. + + +See also: Section :ref:`locating-notations` + + +.. _loading-files: + +Loading files +----------------- + +|Coq| offers the possibility of loading different parts of a whole +development stored in separate files. Their contents will be loaded as +if they were entered from the keyboard. This means that the loaded +files are ASCII files containing sequences of commands for |Coq|’s +toplevel. This kind of file is called a *script* for |Coq|. The standard +(and default) extension of |Coq|’s script files is .v. + + +.. cmd:: Load @ident. + +This command loads the file named :n:`ident`.v, searching successively in +each of the directories specified in the *loadpath*. (see Section +:ref:`libraries-and-filesystem`) + +Files loaded this way cannot leave proofs open, and the ``Load`` +command cannot be used inside a proof either. + +Variants: + + +.. cmdv:: Load @string. + +Loads the file denoted by the string :n:`@string`, where +string is any complete filename. Then the `~` and .. abbreviations are +allowed as well as shell variables. If no extension is specified, |Coq| +will use the default extension ``.v``. + +.. cmdv:: Load Verbose @ident. + +.. cmdv:: Load Verbose @string. + +Display, while loading, +the answers of |Coq| to each command (including tactics) contained in +the loaded file See also: Section :ref:`controlling-display`. + +Error messages: + +.. exn:: Can’t find file @ident on loadpath + +.. exn:: Load is not supported inside proofs + +.. exn:: Files processed by Load cannot leave open proofs + +.. _compiled-files: + +Compiled files +------------------ + +This section describes the commands used to load compiled files (see +Chapter :ref:`thecoqcommands` for documentation on how to compile a file). A compiled +file is a particular case of module called *library file*. + + +.. cmd:: Require @qualid. + +This command looks in the loadpath for a file containing module :n:`@qualid` +and adds the corresponding module to the environment of |Coq|. As +library files have dependencies in other library files, the command +``Require`` :n:`@qualid` recursively requires all library files the module +qualid depends on and adds the corresponding modules to the +environment of |Coq| too. |Coq| assumes that the compiled files have been +produced by a valid |Coq| compiler and their contents are then not +replayed nor rechecked. + +To locate the file in the file system, :n:`@qualid` is decomposed under the +form `dirpath.ident` and the file `ident.vo` is searched in the physical +directory of the file system that is mapped in |Coq| loadpath to the +logical path dirpath (see Section :ref:`libraries-and-filesystem`). The mapping between +physical directories and logical names at the time of requiring the +file must be consistent with the mapping used to compile the file. If +several files match, one of them is picked in an unspecified fashion. + + +Variants: + +.. cmdv:: Require Import @qualid. + +This loads and declares the module :n:`@qualid` +and its dependencies then imports the contents of :n:`@qualid` as described +:ref:`here <import_qualid>`. It does not import the modules on which +qualid depends unless these modules were themselves required in module +:n:`@qualid` +using ``Require Export``, as described below, or recursively required +through a sequence of ``Require Export``. If the module required has +already been loaded, ``Require Import`` :n:`@qualid` simply imports it, as ``Import`` +:n:`@qualid` would. + +.. cmdv:: Require Export @qualid. + +This command acts as ``Require Import`` :n:`@qualid`, +but if a further module, say `A`, contains a command ``Require Export`` `B`, +then the command ``Require Import`` `A` also imports the module `B.` + +.. cmdv:: Require [Import | Export] {+ @qualid }. + +This loads the +modules named by the :n:`qualid` sequence and their recursive +dependencies. If +``Import`` or ``Export`` is given, it also imports these modules and +all the recursive dependencies that were marked or transitively marked +as ``Export``. + +.. cmdv:: From @dirpath Require @qualid. + +This command acts as ``Require``, but picks +any library whose absolute name is of the form dirpath.dirpath’.qualid +for some `dirpath’`. This is useful to ensure that the :n:`@qualid` library +comes from a given package by making explicit its absolute root. + + + +Error messages: + +.. exn:: Cannot load qualid: no physical path bound to dirpath + +.. exn:: Cannot find library foo in loadpath + +The command did not find the +file foo.vo. Either foo.v exists but is not compiled or foo.vo is in a +directory which is not in your LoadPath (see Section :ref:`libraries-and-filesystem`). + +.. exn:: Compiled library @ident.vo makes inconsistent assumptions over library qualid + +The command tried to load library file :n:`@ident`.vo that +depends on some specific version of library :n:`@qualid` which is not the +one already loaded in the current |Coq| session. Probably `ident.v` was +not properly recompiled with the last version of the file containing +module :n:`@qualid`. + +.. exn:: Bad magic number + +The file `ident.vo` was found but either it is not a +|Coq| compiled module, or it was compiled with an incompatible +version of |Coq|. + +.. exn:: The file `ident.vo` contains library dirpath and not library dirpath’ + +The library file `dirpath’` is indirectly required by the +``Require`` command but it is bound in the current loadpath to the +file `ident.vo` which was bound to a different library name `dirpath` at +the time it was compiled. + + +.. exn:: Require is not allowed inside a module or a module type + +This command +is not allowed inside a module or a module type being defined. It is +meant to describe a dependency between compilation units. Note however +that the commands ``Import`` and ``Export`` alone can be used inside modules +(see Section :ref:`Import <import_qualid>`). + + + +See also: Chapter :ref:`thecoqcommands` + + +.. cmd:: Print Libraries. + +This command displays the list of library files loaded in the +current |Coq| session. For each of these libraries, it also tells if it +is imported. + + +.. cmd:: Declare ML Module {+ @string } . + +This commands loads the OCaml compiled files +with names given by the :n:`@string` sequence +(dynamic link). It is mainly used to load tactics dynamically. The +files are searched into the current OCaml loadpath (see the +command ``Add ML Path`` in Section :ref:`libraries-and-filesystem`). Loading of OCaml files is only possible under the bytecode version of ``coqtop`` (i.e. +``coqtop`` called with option ``-byte``, see chapter :ref:`thecoqcommands`), or when |Coq| has been compiled with a +version of OCaml that supports native Dynlink (≥ 3.11). + + +Variants: + + +.. cmdv:: Local Declare ML Module {+ @string }. + +This variant is not +exported to the modules that import the module where they occur, even +if outside a section. + + + +Error messages: + +.. exn:: File not found on loadpath : @string + +.. exn:: Loading of ML object file forbidden in a native Coq + + + +.. cmd:: Print ML Modules. + +This prints the name of all OCaml modules loaded with ``Declare +ML Module``. To know from where these module were loaded, the user +should use the command ``Locate File`` (see :ref:`here <locate-file>`) + + +.. _loadpath: + +Loadpath +------------ + +Loadpaths are preferably managed using |Coq| command line options (see +Section `libraries-and-filesystem`) but there remain vernacular commands to manage them +for practical purposes. Such commands are only meant to be issued in +the toplevel, and using them in source files is discouraged. + + +.. cmd:: Pwd. + +This command displays the current working directory. + + +.. cmd:: Cd @string. + +This command changes the current directory according to :n:`@string` which +can be any valid path. + + +Variants: + + +.. cmdv:: Cd. + +Is equivalent to Pwd. + + + +.. cmd:: Add LoadPath @string as @dirpath. + +This command is equivalent to the command line option +``-Q`` :n:`@string` :n:`@dirpath`. It adds the physical directory string to the current +|Coq| loadpath and maps it to the logical directory dirpath. + +Variants: + + +.. cmdv:: Add LoadPath @string. + +Performs as Add LoadPath :n:`@string` as :n:`@dirpath` but +for the empty directory path. + + + +.. cmd:: Add Rec LoadPath @string as @dirpath. + +This command is equivalent to the command line option +``-R`` :n:`@string` :n:`@dirpath`. It adds the physical directory string and all its +subdirectories to the current |Coq| loadpath. + +Variants: + + +.. cmdv:: Add Rec LoadPath @string. + +Works as ``Add Rec LoadPath`` :n:`@string` as :n:`@dirpath` but for the empty +logical directory path. + + + +.. cmd:: Remove LoadPath @string. + +This command removes the path :n:`@string` from the current |Coq| loadpath. + + +.. cmd:: Print LoadPath. + +This command displays the current |Coq| loadpath. + + +Variants: + + +.. cmdv:: Print LoadPath @dirpath. + +Works as ``Print LoadPath`` but displays only +the paths that extend the :n:`@dirpath` prefix. + + +.. cmd:: Add ML Path @string. + +This command adds the path :n:`@string` to the current OCaml +loadpath (see the command `Declare ML Module`` in Section :ref:`compiled-files`). + + +.. cmd:: Add Rec ML Path @string. + +This command adds the directory :n:`@string` and all its subdirectories to +the current OCaml loadpath (see the command ``Declare ML Module`` +in Section :ref:`compiled-files`). + + +.. cmd:: Print ML Path @string. + +This command displays the current OCaml loadpath. This +command makes sense only under the bytecode version of ``coqtop``, i.e. +using option ``-byte`` +(see the command Declare ML Module in Section :ref:`compiled-files`). + +.. _locate-file: + +.. cmd:: Locate File @string. + +This command displays the location of file string in the current +loadpath. Typically, string is a .cmo or .vo or .v file. + + +.. cmd:: Locate Library @dirpath. + +This command gives the status of the |Coq| module dirpath. It tells if +the module is loaded and if not searches in the load path for a module +of logical name :n:`@dirpath`. + + +.. _backtracking: + +Backtracking +---------------- + +The backtracking commands described in this section can only be used +interactively, they cannot be part of a vernacular file loaded via +``Load`` or compiled by ``coqc``. + + +.. cmd:: Reset @ident. + +This command removes all the objects in the environment since :n:`@ident` +was introduced, including :n:`@ident`. :n:`@ident` may be the name of a defined or +declared object as well as the name of a section. One cannot reset +over the name of a module or of an object inside a module. + + +Error messages: + +.. exn:: @ident: no such entry + +Variants: + +.. cmd:: Reset Initial. + +Goes back to the initial state, just after the start +of the interactive session. + + + +.. cmd:: Back. + +This commands undoes all the effects of the last vernacular command. +Commands read from a vernacular file via a ``Load`` are considered as a +single command. Proof management commands are also handled by this +command (see Chapter :ref:`proofhandling`). For that, Back may have to undo more than +one command in order to reach a state where the proof management +information is available. For instance, when the last command is a +``Qed``, the management information about the closed proof has been +discarded. In this case, ``Back`` will then undo all the proof steps up to +the statement of this proof. + + +Variants: + + +.. cmdv:: Back @num. + +Undoes :n:`@num` vernacular commands. As for Back, some extra +commands may be undone in order to reach an adequate state. For +instance Back :n:`@num` will not re-enter a closed proof, but rather go just +before that proof. + + + +Error messages: + + +.. exn:: Invalid backtrack + +The user wants to undo more commands than available in the history. + +.. cmd:: BackTo @num. + +This command brings back the system to the state labeled :n:`@num`, +forgetting the effect of all commands executed after this state. The +state label is an integer which grows after each successful command. +It is displayed in the prompt when in -emacs mode. Just as ``Back`` (see +above), the ``BackTo`` command now handles proof states. For that, it may +have to undo some extra commands and end on a state `num′ ≤ num` if +necessary. + + +Variants: + + +.. cmdv:: Backtrack @num @num @num. + +`Backtrack` is a *deprecated* form of +`BackTo` which allows explicitly manipulating the proof environment. The +three numbers represent the following: + + + *first number* : State label to reach, as for BackTo. + + *second number* : *Proof state number* to unbury once aborts have been done. + |Coq| will compute the number of Undo to perform (see Chapter :ref:`proofhandling`). + + *third number* : Number of Abort to perform, i.e. the number of currently + opened nested proofs that must be canceled (see Chapter :ref:`proofhandling`). + + + + +Error messages: + + +.. exn:: Invalid backtrack + + +The destination state label is unknown. + + +.. _quitting-and-debugging: + +Quitting and debugging +-------------------------- + + +.. cmd:: Quit. + +This command permits to quit |Coq|. + + +.. cmd:: Drop. + +This is used mostly as a debug facility by |Coq|’s implementors and does +not concern the casual user. This command permits to leave |Coq| +temporarily and enter the OCaml toplevel. The OCaml +command: + + +:: + + #use "include";; + + +adds the right loadpaths and loads some toplevel printers for all +abstract types of |Coq|- section_path, identifiers, terms, judgments, …. +You can also use the file base_include instead, that loads only the +pretty-printers for section_paths and identifiers. You can return back +to |Coq| with the command: + + +:: + + go();; + +.. warning:: + + #. It only works with the bytecode version of |Coq| (i.e. `coqtop.byte`, + see Section `interactive-use`). + #. You must have compiled |Coq| from the source package and set the + environment variable COQTOP to the root of your copy of the sources + (see Section `customization-by-environment-variables`). + + + +.. TODO : command is not a syntax entry + +.. cmd:: Time @command. + +This command executes the vernacular command :n:`@command` and displays the +time needed to execute it. + + +.. cmd:: Redirect @string @command. + +This command executes the vernacular command :n:`@command`, redirecting its +output to ":n:`@string`.out". + + +.. cmd:: Timeout @num @command. + +This command executes the vernacular command :n:`@command`. If the command +has not terminated after the time specified by the :n:`@num` (time +expressed in seconds), then it is interrupted and an error message is +displayed. + + +.. opt:: Default Timeout @num + + This option controls a default timeout for subsequent commands, as if they + were passed to a :cmd:`Timeout` command. Commands already starting by a + :cmd:`Timeout` are unaffected. + +.. cmd:: Fail @command. + +For debugging scripts, sometimes it is desirable to know +whether a command or a tactic fails. If the given :n:`@command` +fails, the ``Fail`` statement succeeds, without changing the proof +state, and in interactive mode, the system +prints a message confirming the failure. +If the given :n:`@command` succeeds, the statement is an error, and +it prints a message indicating that the failure did not occur. + +Error messages: + +.. exn:: The command has not failed! + +.. _controlling-display: + +Controlling display +----------------------- + +.. opt:: Silent + + This option controls the normal displaying. + +.. opt:: Warnings "{+, {? %( - %| + %) } @ident }" + + This option configures the display of warnings. It is experimental, and + expects, between quotes, a comma-separated list of warning names or + categories. Adding - in front of a warning or category disables it, adding + + makes it an error. It is possible to use the special categories all and + default, the latter containing the warnings enabled by default. The flags are + interpreted from left to right, so in case of an overlap, the flags on the + right have higher priority, meaning that `A,-A` is equivalent to `-A`. + +.. opt:: Search Output Name Only + + This option restricts the output of search commands to identifier names; + turning it on causes invocations of :cmd:`Search`, :cmd:`SearchHead`, + :cmd:`SearchPattern`, :cmd:`SearchRewrite` etc. to omit types from their + output, printing only identifiers. + +.. opt:: Printing Width @integer + + This command sets which left-aligned part of the width of the screen is used + for display. At the time of writing this documentation, the default value + is 78. + +.. opt:: Printing Depth @integer + + This option controls the nesting depth of the formatter used for pretty- + printing. Beyond this depth, display of subterms is replaced by dots. At the + time of writing this documentation, the default value is 50. + +.. opt:: Printing Compact Contexts + + This option controls the compact display mode for goals contexts. When on, + the printer tries to reduce the vertical size of goals contexts by putting + several variables (even if of different types) on the same line provided it + does not exceed the printing width (see :opt:`Printing Width`). At the time + of writing this documentation, it is off by default. + +.. opt:: Printing Unfocused + + This option controls whether unfocused goals are displayed. Such goals are + created by focusing other goals with bullets (see :ref:`bullets` or + :ref:`curly braces <curly-braces>`). It is off by default. + +.. opt:: Printing Dependent Evars Line + + This option controls the printing of the “(dependent evars: …)” line when + ``-emacs`` is passed. + + +.. _vernac-controlling-the-reduction-strategies: + +Controlling the reduction strategies and the conversion algorithm +---------------------------------------------------------------------- + + +|Coq| provides reduction strategies that the tactics can invoke and two +different algorithms to check the convertibility of types. The first +conversion algorithm lazily compares applicative terms while the other +is a brute-force but efficient algorithm that first normalizes the +terms before comparing them. The second algorithm is based on a +bytecode representation of terms similar to the bytecode +representation used in the ZINC virtual machine :cite:`Leroy90`. It is +especially useful for intensive computation of algebraic values, such +as numbers, and for reflection-based tactics. The commands to fine- +tune the reduction strategies and the lazy conversion algorithm are +described first. + +.. cmd:: Opaque {+ @qualid }. + +This command has an effect on unfoldable constants, i.e. on constants +defined by ``Definition`` or ``Let`` (with an explicit body), or by a command +assimilated to a definition such as ``Fixpoint``, ``Program Definition``, etc, +or by a proof ended by ``Defined``. The command tells not to unfold the +constants in the :n:`@qualid` sequence in tactics using δ-conversion (unfolding +a constant is replacing it by its definition). + +``Opaque`` has also an effect on the conversion algorithm of |Coq|, telling +it to delay the unfolding of a constant as much as possible when |Coq| +has to check the conversion (see Section :ref:`conversion-rules`) of two distinct +applied constants. + +The scope of ``Opaque`` is limited to the current section, or current +file, unless the variant ``Global Opaque`` is used. + + +See also: sections :ref:`performingcomputations`, :ref:`tactics-automatizing`, :ref:`proof-editing-mode` + + +Error messages: + + +.. exn:: The reference @qualid was not found in the current environment + +There is no constant referred by :n:`@qualid` in the environment. +Nevertheless, if you asked ``Opaque`` `foo` `bar` and if `bar` does not exist, `foo` is set opaque. + +.. cmd:: Transparent {+ @qualid }. + +This command is the converse of `Opaque`` and it applies on unfoldable +constants to restore their unfoldability after an Opaque command. + +Note in particular that constants defined by a proof ended by Qed are +not unfoldable and Transparent has no effect on them. This is to keep +with the usual mathematical practice of *proof irrelevance*: what +matters in a mathematical development is the sequence of lemma +statements, not their actual proofs. This distinguishes lemmas from +the usual defined constants, whose actual values are of course +relevant in general. + +The scope of Transparent is limited to the current section, or current +file, unless the variant ``Global Transparent`` is +used. + + +Error messages: + + +.. exn:: The reference @qualid was not found in the current environment + +There is no constant referred by :n:`@qualid` in the environment. + + + +See also: sections :ref:`performingcomputations`, :ref:`tactics-automatizing`, :ref:`proof-editing-mode` + +.. _vernac-strategy: + +.. cmd:: Strategy @level [ {+ @qualid } ]. + +This command generalizes the behavior of Opaque and Transparent +commands. It is used to fine-tune the strategy for unfolding +constants, both at the tactic level and at the kernel level. This +command associates a level to the qualified names in the :n:`@qualid` +sequence. Whenever two +expressions with two distinct head constants are compared (for +instance, this comparison can be triggered by a type cast), the one +with lower level is expanded first. In case of a tie, the second one +(appearing in the cast type) is expanded. + +Levels can be one of the following (higher to lower): + + + ``opaque`` : level of opaque constants. They cannot be expanded by + tactics (behaves like +∞, see next item). + + :n:`@num` : levels indexed by an integer. Level 0 corresponds to the + default behavior, which corresponds to transparent constants. This + level can also be referred to as transparent. Negative levels + correspond to constants to be expanded before normal transparent + constants, while positive levels correspond to constants to be + expanded after normal transparent constants. + + ``expand`` : level of constants that should be expanded first (behaves + like −∞) + + +These directives survive section and module closure, unless the +command is prefixed by Local. In the latter case, the behavior +regarding sections and modules is the same as for the ``Transparent`` and +``Opaque`` commands. + + +.. cmd:: Print Strategy @qualid. + +This command prints the strategy currently associated to :n:`@qualid`. It +fails if :n:`@qualid` is not an unfoldable reference, that is, neither a +variable nor a constant. + + +Error messages: + + +.. exn:: The reference is not unfoldable. + + + +Variants: + + +.. cmdv:: Print Strategies. + +Print all the currently non-transparent strategies. + + + +.. cmd:: Declare Reduction @ident := @convtactic. + +This command allows giving a short name to a reduction expression, for +instance lazy beta delta [foo bar]. This short name can then be used +in ``Eval`` :n:`@ident` ``in`` ... or ``eval`` directives. This command +accepts the +Local modifier, for discarding this reduction name at the end of the +file or module. For the moment the name cannot be qualified. In +particular declaring the same name in several modules or in several +functor applications will be refused if these declarations are not +local. The name :n:`@ident` cannot be used directly as an Ltac tactic, but +nothing prevents the user to also perform a +``Ltac`` `ident` ``:=`` `convtactic`. + + +See also: sections :ref:`performingcomputations` + + +.. _controlling-locality-of-commands: + +Controlling the locality of commands +----------------------------------------- + + +.. cmd:: Local @command. +.. cmd:: Global @command. + +Some commands support a Local or Global prefix modifier to control the +scope of their effect. There are four kinds of commands: + + ++ Commands whose default is to extend their effect both outside the + section and the module or library file they occur in. For these + commands, the Local modifier limits the effect of the command to the + current section or module it occurs in. As an example, the ``Coercion`` + (see Section :ref:`coercions`) and ``Strategy`` (see :ref:`here <vernac-strategy>`) + commands belong to this category. ++ Commands whose default behavior is to stop their effect at the end + of the section they occur in but to extent their effect outside the module or + library file they occur in. For these commands, the Local modifier limits the + effect of the command to the current module if the command does not occur in a + section and the Global modifier extends the effect outside the current + sections and current module if the command occurs in a section. As an example, + the :cmd:`Implicit Arguments`, :cmd:`Ltac` or :cmd:`Notation` commands belong + to this category. Notice that a subclass of these commands do not support + extension of their scope outside sections at all and the Global is not + applicable to them. ++ Commands whose default behavior is to stop their effect at the end + of the section or module they occur in. For these commands, the Global + modifier extends their effect outside the sections and modules they + occurs in. The ``Transparent`` and ``Opaque`` (see Section :ref:`vernac-controlling-the-reduction-strategies`) commands belong to this category. ++ Commands whose default behavior is to extend their effect outside + sections but not outside modules when they occur in a section and to + extend their effect outside the module or library file they occur in + when no section contains them.For these commands, the Local modifier + limits the effect to the current section or module while the Global + modifier extends the effect outside the module even when the command + occurs in a section. The ``Set`` and ``Unset`` commands belong to this + category. diff --git a/doc/sphinx/replaces.rst b/doc/sphinx/replaces.rst index d4f6835ef4..28a04f90ce 100644 --- a/doc/sphinx/replaces.rst +++ b/doc/sphinx/replaces.rst @@ -35,7 +35,9 @@ .. |ident_n,1| replace:: `ident`\ :math:`_{n,1}` .. |ident_n,k_n| replace:: `ident`\ :math:`_{n,k_n}` .. |ident_n| replace:: `ident`\ :math:`_{n}` +.. |Latex| replace:: :smallcaps:`LaTeX` .. |L_tac| replace:: `L`:sub:`tac` +.. |Ltac| replace:: `L`:sub:`tac` .. |ML| replace:: :smallcaps:`ML` .. |mod_0| replace:: `mod`\ :math:`_{0}` .. |mod_1| replace:: `mod`\ :math:`_{1}` @@ -54,7 +56,7 @@ .. |module_type_n| replace:: `module_type`\ :math:`_{n}` .. |N| replace:: ``N`` .. |nat| replace:: ``nat`` -.. |Ocaml| replace:: :smallcaps:`OCaml` +.. |OCaml| replace:: :smallcaps:`OCaml` .. |p_1| replace:: `p`\ :math:`_{1}` .. |p_i| replace:: `p`\ :math:`_{i}` .. |p_n| replace:: `p`\ :math:`_{n}` @@ -64,6 +66,14 @@ .. |t_i| replace:: `t`\ :math:`_{i}` .. |t_m| replace:: `t`\ :math:`_{m}` .. |t_n| replace:: `t`\ :math:`_{n}` +.. |f_1| replace:: `f`\ :math:`_{1}` +.. |f_i| replace:: `f`\ :math:`_{i}` +.. |f_m| replace:: `f`\ :math:`_{m}` +.. |f_n| replace:: `f`\ :math:`_{n}` +.. |u_1| replace:: `u`\ :math:`_{1}` +.. |u_i| replace:: `u`\ :math:`_{i}` +.. |u_m| replace:: `u`\ :math:`_{m}` +.. |u_n| replace:: `u`\ :math:`_{n}` .. |term_0| replace:: `term`\ :math:`_{0}` .. |term_1| replace:: `term`\ :math:`_{1}` .. |term_2| replace:: `term`\ :math:`_{2}` diff --git a/doc/sphinx/user-extensions/proof-schemes.rst b/doc/sphinx/user-extensions/proof-schemes.rst index 583b73e53d..e12e4d897a 100644 --- a/doc/sphinx/user-extensions/proof-schemes.rst +++ b/doc/sphinx/user-extensions/proof-schemes.rst @@ -3,6 +3,8 @@ Proof schemes =============== +.. _proofschemes-induction-principles: + Generation of induction principles with ``Scheme`` -------------------------------------------------------- @@ -10,7 +12,7 @@ The ``Scheme`` command is a high-level tool for generating automatically (possibly mutual) induction principles for given types and sorts. Its syntax follows the schema: -.. cmd:: Scheme ident := Induction for ident' Sort sort {* with ident := Induction for ident' Sort sort} +.. cmd:: Scheme @ident := Induction for @ident Sort sort {* with @ident := Induction for @ident Sort sort} where each `ident'ᵢ` is a different inductive type identifier belonging to the same package of mutual inductive definitions. This @@ -18,17 +20,17 @@ command generates the `identᵢ`s to be mutually recursive definitions. Each term `identᵢ` proves a general principle of mutual induction for objects in type `identᵢ`. -.. cmdv:: Scheme ident := Minimality for ident' Sort sort {* with ident := Minimality for ident' Sort sort} +.. cmdv:: Scheme @ident := Minimality for @ident Sort sort {* with @ident := Minimality for @ident' Sort sort} Same as before but defines a non-dependent elimination principle more natural in case of inductively defined relations. -.. cmdv:: Scheme Equality for ident +.. cmdv:: Scheme Equality for @ident Tries to generate a Boolean equality and a proof of the decidability of the usual equality. If `ident` involves some other inductive types, their equality has to be defined first. -.. cmdv:: Scheme Induction for ident Sort sort {* with Induction for ident Sort sort} +.. cmdv:: Scheme Induction for @ident Sort sort {* with Induction for @ident Sort sort} If you do not provide the name of the schemes, they will be automatically computed from the sorts involved (works also with Minimality). @@ -101,26 +103,34 @@ induction for objects in type `identᵢ`. Automatic declaration of schemes ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +.. opt:: Elimination Schemes + It is possible to deactivate the automatic declaration of the induction principles when defining a new inductive type with the ``Unset Elimination Schemes`` command. It may be reactivated at any time with ``Set Elimination Schemes``. -The types declared with the keywords ``Variant`` (see :ref:`TODO-1.3.3`) and ``Record`` -(see :ref:`Record Types <record-types>`) do not have an automatic declaration of the induction -principles. It can be activated with the command -``Set Nonrecursive Elimination Schemes``. It can be deactivated again with -``Unset Nonrecursive Elimination Schemes``. - -In addition, the ``Case Analysis Schemes`` flag governs the generation of -case analysis lemmas for inductive types, i.e. corresponding to the -pattern-matching term alone and without fixpoint. -You can also activate the automatic declaration of those Boolean -equalities (see the second variant of ``Scheme``) with respectively the -commands ``Set Boolean Equality Schemes`` and ``Set Decidable Equality -Schemes``. However you have to be careful with this option since Coq may -now reject well-defined inductive types because it cannot compute a -Boolean equality for them. +.. opt:: Nonrecursive Elimination Schemes + +This option controls whether types declared with the keywords :cmd:`Variant` and +:cmd:`Record` get an automatic declaration of the induction principles. + +.. opt:: Case Analysis Schemes + + This flag governs the generation of case analysis lemmas for inductive types, + i.e. corresponding to the pattern-matching term alone and without fixpoint. + +.. opt:: Boolean Equality Schemes + +.. opt:: Decidable Equality Schemes + +These flags control the automatic declaration of those Boolean equalities (see +the second variant of ``Scheme``). + +.. warning:: + + You have to be careful with this option since Coq may now reject well-defined + inductive types because it cannot compute a Boolean equality for them. .. opt:: Rewriting Schemes @@ -133,7 +143,7 @@ The ``Combined Scheme`` command is a tool for combining induction principles generated by the ``Scheme command``. Its syntax follows the schema : -.. cmd:: Combined Scheme ident from {+, ident} +.. cmd:: Combined Scheme @ident from {+, ident} where each identᵢ after the ``from`` is a different inductive principle that must belong to the same package of mutual inductive principle definitions. @@ -163,6 +173,8 @@ concluded by the conjunction of their conclusions. Check tree_forest_mutind. +.. _functional-scheme: + Generation of induction principles with ``Functional`` ``Scheme`` ----------------------------------------------------------------- @@ -172,7 +184,7 @@ generating automatically induction principles corresponding to available via ``Require Import FunInd``. Its syntax then follows the schema: -.. cmd:: Functional Scheme ident := Induction for ident' Sort sort {* with ident := Induction for ident' Sort sort} +.. cmd:: Functional Scheme @ident := Induction for ident' Sort sort {* with @ident := Induction for @ident Sort sort} where each `ident'ᵢ` is a different mutually defined function name (the names must be in the same order as when they were defined). This @@ -229,7 +241,7 @@ definition written by the user. simpl; auto with arith. Qed. - We can use directly the functional induction (:ref:`TODO-8.5.5`) tactic instead + We can use directly the functional induction (:tacn:`function induction`) tactic instead of the pattern/apply trick: .. coqtop:: all @@ -305,13 +317,15 @@ definition written by the user. .. coqtop:: all Check tree_size_ind2. + +.. _derive-inversion: Generation of inversion principles with ``Derive`` ``Inversion`` ----------------------------------------------------------------- The syntax of ``Derive`` ``Inversion`` follows the schema: -.. cmd:: Derive Inversion ident with forall (x : T), I t Sort sort +.. cmd:: Derive Inversion @ident with forall (x : T), I t Sort sort This command generates an inversion principle for the `inversion … using` tactic. Let `I` be an inductive predicate and `x` the variables occurring @@ -320,17 +334,17 @@ sort `sort` corresponding to the instance `∀ (x:T), I t` with the name `ident` in the global environment. When applied, it is equivalent to having inverted the instance with the tactic `inversion`. -.. cmdv:: Derive Inversion_clear ident with forall (x:T), I t Sort sort +.. cmdv:: Derive Inversion_clear @ident with forall (x:T), I t Sort sort When applied, it is equivalent to having inverted the instance with the tactic inversion replaced by the tactic `inversion_clear`. -.. cmdv:: Derive Dependent Inversion ident with forall (x:T), I t Sort sort +.. cmdv:: Derive Dependent Inversion @ident with forall (x:T), I t Sort sort When applied, it is equivalent to having inverted the instance with the tactic `dependent inversion`. -.. cmdv:: Derive Dependent Inversion_clear ident with forall(x:T), I t Sort sort +.. cmdv:: Derive Dependent Inversion_clear @ident with forall(x:T), I t Sort sort When applied, it is equivalent to having inverted the instance with the tactic `dependent inversion_clear`. diff --git a/doc/sphinx/user-extensions/syntax-extensions.rst b/doc/sphinx/user-extensions/syntax-extensions.rst index 6e6d664475..c4a7121ce4 100644 --- a/doc/sphinx/user-extensions/syntax-extensions.rst +++ b/doc/sphinx/user-extensions/syntax-extensions.rst @@ -10,12 +10,12 @@ parses and prints objects, i.e. the translations between the concrete and internal representations of terms and commands. The main commands to provide custom symbolic notations for terms are -``Notation`` and ``Infix``. They are described in section 12.1. There is also a +``Notation`` and ``Infix``. They are described in section :ref:`Notations`. There is also a variant of ``Notation`` which does not modify the parser. This provides with a form of abbreviation and it is described in Section :ref:`Abbreviations`. It is sometimes expected that the same symbolic notation has different meanings in different contexts. To achieve this form of overloading, |Coq| offers a notion -of interpretation scope. This is described in Section :ref:`scopes`. +of interpretation scope. This is described in Section :ref:`Scopes`. The main command to provide custom notations for tactics is ``Tactic Notation``. It is described in Section :ref:`TacticNotation`. @@ -24,12 +24,16 @@ It is described in Section :ref:`TacticNotation`. Set Printing Depth 50. +.. _Notations: + Notations --------- Basic notations ~~~~~~~~~~~~~~~ +.. cmd:: Notation + A *notation* is a symbolic expression denoting some term or term pattern. @@ -68,7 +72,7 @@ have to be given. .. note:: The right-hand side of a notation is interpreted at the time the notation is - given. In particular, disambiguiation of constants, implicit arguments (see + given. In particular, disambiguation of constants, implicit arguments (see Section :ref:`ImplicitArguments`), coercions (see Section :ref:`Coercions`), etc. are resolved at the time of the declaration of the notation. @@ -343,13 +347,13 @@ inductive type or a recursive constant and a notation for it. Simultaneous definition of terms and notations ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Thanks to reserved notations, the inductive, co-inductive, record, recursive -and corecursive definitions can benefit of customized notations. To do -this, insert a ``where`` notation clause after the definition of the -(co)inductive type or (co)recursive term (or after the definition of -each of them in case of mutual definitions). The exact syntax is given -on Figure 12.1 for inductive, co-inductive, recursive and corecursive -definitions and on Figure :ref:`record-syntax` for records. Here are examples: +Thanks to reserved notations, the inductive, co-inductive, record, recursive and +corecursive definitions can benefit of customized notations. To do this, insert +a ``where`` notation clause after the definition of the (co)inductive type or +(co)recursive term (or after the definition of each of them in case of mutual +definitions). The exact syntax is given by :token:`decl_notation` for inductive, +co-inductive, recursive and corecursive definitions and in :ref:`record-types` +for records. Here are examples: .. coqtop:: in @@ -379,23 +383,21 @@ Displaying informations about notations :opt:`Printing All` To disable other elements in addition to notations. +.. _locating-notations: + Locating notations ~~~~~~~~~~~~~~~~~~ -.. cmd:: Locate @symbol - - To know to which notations a given symbol belongs to, use the command - ``Locate symbol``, where symbol is any (composite) symbol surrounded by double - quotes. To locate a particular notation, use a string where the variables of the - notation are replaced by “_” and where possible single quotes inserted around - identifiers or tokens starting with a single quote are dropped. - - .. coqtop:: all +To know to which notations a given symbol belongs to, use the :cmd:`Locate` +command. You can call it on any (composite) symbol surrounded by double quotes. +To locate a particular notation, use a string where the variables of the +notation are replaced by “_” and where possible single quotes inserted around +identifiers or tokens starting with a single quote are dropped. - Locate "exists". - Locate "exists _ .. _ , _". +.. coqtop:: all - .. todo:: See also: Section 6.3.10. + Locate "exists". + Locate "exists _ .. _ , _". Notations and binders ~~~~~~~~~~~~~~~~~~~~~ @@ -433,8 +435,7 @@ Binders bound in the notation and parsed as patterns In the same way as patterns can be used as binders, as in :g:`fun '(x,y) => x+y` or :g:`fun '(existT _ x _) => x`, notations can be -defined so that any pattern (in the sense of the entry :n:`@pattern` of -Figure :ref:`term-syntax-aux`) can be used in place of the +defined so that any :n:`@pattern` can be used in place of the binder. Here is an example: .. coqtop:: in reset @@ -473,7 +474,7 @@ variable. Here is an example showing the difference: The default level for a ``pattern`` is 0. One can use a different level by using ``pattern at level`` :math:`n` where the scale is the same as the one for -terms (Figure :ref:`init-notations`). +terms (see :ref:`init-notations`). Binders bound in the notation and parsed as terms +++++++++++++++++++++++++++++++++++++++++++++++++ @@ -489,7 +490,7 @@ the following: This is so because the grammar also contains rules starting with :g:`{}` and followed by a term, such as the rule for the notation :g:`{ A } + { B }` for the -constant :g:`sumbool` (see Section :ref:`sumbool`). +constant :g:`sumbool` (see Section :ref:`specification`). Then, in the rule, ``x ident`` is replaced by ``x at level 99 as ident`` meaning that ``x`` is parsed as a term at level 99 (as done in the notation for @@ -689,8 +690,7 @@ side. E.g.: Summary ~~~~~~~ -Syntax of notations -~~~~~~~~~~~~~~~~~~~ +**Syntax of notations** The different syntactic variants of the command Notation are given on the following figure. The optional :token:`scope` is described in the Section 12.2. @@ -743,8 +743,7 @@ following figure. The optional :token:`scope` is described in the Section 12.2. given to some notation, say ``"{ y } & { z }"`` in fact applies to the underlying ``"{ x }"``\-free rule which is ``"y & z"``). -Persistence of notations -~~~~~~~~~~~~~~~~~~~~~~~~ +**Persistence of notations** Notations do not survive the end of sections. @@ -753,6 +752,8 @@ Notations do not survive the end of sections. Notations survive modules unless the command ``Local Notation`` is used instead of ``Notation``. +.. _Scopes: + Interpretation scopes ---------------------- @@ -827,6 +828,8 @@ lonely notations. These scopes, in opening order, are ``core_scope``, These variants survive sections. They behave as if Global were absent when not inside a section. +.. _LocalInterpretationRulesForNotations: + Local interpretation rules for notations ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -857,6 +860,7 @@ Binding arguments of a constant to an interpretation scope +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ .. cmd:: Arguments @qualid {+ @name%@scope} + :name: Arguments (scopes) It is possible to set in advance that some arguments of a given constant have to be interpreted in a given scope. The command is @@ -895,7 +899,7 @@ Binding arguments of a constant to an interpretation scope .. cmdv:: Arguments @qualid {+ @name%scope} : extra scopes Defines extra argument scopes, to be used in case of coercion to Funclass - (see Chapter :ref:`Coercions-full`) or with a computed type. + (see Chapter :ref:`implicitcoercions`) or with a computed type. .. cmdv:: Global Arguments @qualid {+ @name%@scope} @@ -955,7 +959,7 @@ Binding types of arguments to an interpretation scope type :g:`t` in :g:`f t a` is not recognized as an argument to be interpreted in scope ``scope``. - More generally, any coercion :n:`@class` (see Chapter :ref:`Coercions-full`) + More generally, any coercion :n:`@class` (see Chapter :ref:`implicitcoercions`) can be bound to an interpretation scope. The command to do it is :n:`Bind Scope @scope with @class` @@ -1125,6 +1129,8 @@ Displaying informations about scopes class of all the existing interpretation scopes. It also displays the lonely notations. +.. _Abbreviations: + Abbreviations -------------- @@ -1187,6 +1193,8 @@ Abbreviations denoted expression is performed at definition time. Type-checking is done only at the time of use of the abbreviation. +.. _TacticNotation: + Tactic Notations ----------------- @@ -1194,7 +1202,7 @@ Tactic notations allow to customize the syntax of the tactics of the tactic language. Tactic notations obey the following syntax: .. productionlist:: coq - tacn : [Local] Tactic Notation [`tactic_level`] [`prod_item` … `prod_item`] := `tactic`. + tacn : Tactic Notation [`tactic_level`] [`prod_item` … `prod_item`] := `tactic`. prod_item : `string` | `tactic_argument_type`(`ident`) tactic_level : (at level `natural`) tactic_argument_type : ident | simple_intropattern | reference @@ -1205,7 +1213,7 @@ tactic language. Tactic notations obey the following syntax: : | tactic | tactic0 | tactic1 | tactic2 | tactic3 : | tactic4 | tactic5 -.. cmd:: {? Local} Tactic Notation {? (at level @level)} {+ @prod_item} := @tactic. +.. cmd:: Tactic Notation {? (at level @level)} {+ @prod_item} := @tactic. A tactic notation extends the parser and pretty-printer of tactics with a new rule made of the list of production items. It then evaluates into the |