From 730e25488e0f502359ed8c2a845b97bf0245d1e7 Mon Sep 17 00:00:00 2001 From: gmelquio Date: Sat, 15 Sep 2012 17:10:37 +0000 Subject: Port rewrites of tactic documentation from branch 8.4. This encompasses commits r15183, r15190, r15243, r15262, r15276, r15277, r15278, r15337. The merge did not go without troubles, but hopefully none of the changes were lost in process. git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@15806 85f007b7-540e-0410-9357-904b9bb8a0f7 --- Makefile.common | 2 +- doc/refman/RefMan-sch.tex | 418 +++ doc/refman/RefMan-tac.tex | 6431 ++++++++++++++++++++------------------- doc/refman/RefMan-tacex.tex | 584 ---- doc/refman/Reference-Manual.tex | 3 +- 5 files changed, 3691 insertions(+), 3747 deletions(-) create mode 100644 doc/refman/RefMan-sch.tex diff --git a/Makefile.common b/Makefile.common index 63d194a4b9..654a715272 100644 --- a/Makefile.common +++ b/Makefile.common @@ -120,7 +120,7 @@ REFMANCOQTEXFILES:=$(addprefix doc/refman/, \ RefMan-cic.v.tex RefMan-lib.v.tex \ RefMan-tacex.v.tex RefMan-syn.v.tex \ RefMan-oth.v.tex RefMan-ltac.v.tex \ - RefMan-decl.v.tex RefMan-pro.v.tex \ + RefMan-decl.v.tex RefMan-pro.v.tex RefMan-sch.v.tex \ Cases.v.tex Coercion.v.tex Extraction.v.tex \ Program.v.tex Omega.v.tex Micromega.v.tex Polynom.v.tex Nsatz.v.tex \ Setoid.v.tex Helm.tex Classes.v.tex ) diff --git a/doc/refman/RefMan-sch.tex b/doc/refman/RefMan-sch.tex new file mode 100644 index 0000000000..707ee8240f --- /dev/null +++ b/doc/refman/RefMan-sch.tex @@ -0,0 +1,418 @@ +\chapter{Proof schemes} + +\section{Generation of induction principles with {\tt Scheme}} +\label{Scheme} +\index{Schemes} +\comindex{Scheme} + +The {\tt Scheme} command is a high-level tool for generating +automatically (possibly mutual) induction principles for given types +and sorts. Its syntax follows the schema: +\begin{quote} +{\tt Scheme {\ident$_1$} := Induction for \ident'$_1$ Sort {\sort$_1$} \\ + with\\ + \mbox{}\hspace{0.1cm} \dots\\ + with {\ident$_m$} := Induction for {\ident'$_m$} Sort + {\sort$_m$}} +\end{quote} +where \ident'$_1$ \dots\ \ident'$_m$ are different inductive type +identifiers belonging to the same package of mutual inductive +definitions. This command generates {\ident$_1$}\dots{} {\ident$_m$} +to be mutually recursive definitions. Each term {\ident$_i$} proves a +general principle of mutual induction for objects in type {\term$_i$}. + +\begin{Variants} +\item {\tt Scheme {\ident$_1$} := Minimality for \ident'$_1$ Sort {\sort$_1$} \\ + with\\ + \mbox{}\hspace{0.1cm} \dots\ \\ + with {\ident$_m$} := Minimality for {\ident'$_m$} Sort + {\sort$_m$}} + + Same as before but defines a non-dependent elimination principle more + natural in case of inductively defined relations. + +\item {\tt Scheme Equality for \ident$_1$\comindex{Scheme Equality}} + + Tries to generate a boolean equality and a proof of the + decidability of the usual equality. If \ident$_i$ involves + some other inductive types, their equality has to be defined first. + +\item {\tt Scheme Induction for \ident$_1$ Sort {\sort$_1$} \\ + with\\ + \mbox{}\hspace{0.1cm} \dots\\ + with Induction for {\ident$_m$} Sort + {\sort$_m$}} + + If you do not provide the name of the schemes, they will be automatically + computed from the sorts involved (works also with Minimality). + +\end{Variants} +\label{Scheme-examples} + +\firstexample +\example{Induction scheme for \texttt{tree} and \texttt{forest}} + +The definition of principle of mutual induction for {\tt tree} and +{\tt forest} over the sort {\tt Set} is defined by the command: + +\begin{coq_eval} +Reset Initial. +Variables A B : Set. +\end{coq_eval} + +\begin{coq_example*} +Inductive tree : Set := + node : A -> forest -> tree +with forest : Set := + | leaf : B -> forest + | cons : tree -> forest -> forest. + +Scheme tree_forest_rec := Induction for tree Sort Set + with forest_tree_rec := Induction for forest Sort Set. +\end{coq_example*} + +You may now look at the type of {\tt tree\_forest\_rec}: + +\begin{coq_example} +Check tree_forest_rec. +\end{coq_example} + +This principle involves two different predicates for {\tt trees} and +{\tt forests}; it also has three premises each one corresponding to a +constructor of one of the inductive definitions. + +The principle {\tt forest\_tree\_rec} shares exactly the same +premises, only the conclusion now refers to the property of forests. + +\begin{coq_example} +Check forest_tree_rec. +\end{coq_example} + +\example{Predicates {\tt odd} and {\tt even} on naturals} + +Let {\tt odd} and {\tt even} be inductively defined as: + +% Reset Initial. +\begin{coq_eval} +Open Scope nat_scope. +\end{coq_eval} + +\begin{coq_example*} +Inductive odd : nat -> Prop := + oddS : forall n:nat, even n -> odd (S n) +with even : nat -> Prop := + | evenO : even 0 + | evenS : forall n:nat, odd n -> even (S n). +\end{coq_example*} + +The following command generates a powerful elimination +principle: + +\begin{coq_example} +Scheme odd_even := Minimality for odd Sort Prop + with even_odd := Minimality for even Sort Prop. +\end{coq_example} + +The type of {\tt odd\_even} for instance will be: + +\begin{coq_example} +Check odd_even. +\end{coq_example} + +The type of {\tt even\_odd} shares the same premises but the +conclusion is {\tt (n:nat)(even n)->(Q n)}. + +\subsection{Automatic declaration of schemes} +\comindex{Set Equality Schemes} +\comindex{Set Elimination Schemes} + +It is possible to deactivate the automatic declaration of the induction + principles when defining a new inductive type with the + {\tt Unset Elimination Schemes} command. It may be +reactivated at any time with {\tt Set Elimination Schemes}. +\\ + +You can also activate the automatic declaration of those boolean equalities +(see the second variant of {\tt Scheme}) with the {\tt Set Equality Schemes} + command. 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. + +\subsection{\tt Combined Scheme} +\label{CombinedScheme} +\comindex{Combined Scheme} + +The {\tt Combined Scheme} command is a tool for combining +induction principles generated by the {\tt Scheme} command. +Its syntax follows the schema : +\begin{quote} +{\tt Combined Scheme {\ident$_0$} from {\ident$_1$}, .., {\ident$_n$}} +\end{quote} +where +\ident$_1$ \ldots \ident$_n$ are different inductive principles that must belong to +the same package of mutual inductive principle definitions. This command +generates {\ident$_0$} to be the conjunction of the principles: it is +built from the common premises of the principles and concluded by the +conjunction of their conclusions. + +\Example +We can define the induction principles for trees and forests using: +\begin{coq_example} +Scheme tree_forest_ind := Induction for tree Sort Prop + with forest_tree_ind := Induction for forest Sort Prop. +\end{coq_example} + +Then we can build the combined induction principle which gives the +conjunction of the conclusions of each individual principle: +\begin{coq_example} +Combined Scheme tree_forest_mutind from tree_forest_ind, forest_tree_ind. +\end{coq_example} + +The type of {\tt tree\_forest\_mutrec} will be: +\begin{coq_example} +Check tree_forest_mutind. +\end{coq_example} + +\section{Generation of induction principles with {\tt Functional Scheme}} +\label{FunScheme} +\comindex{Functional Scheme} + +The {\tt Functional Scheme} command is a high-level experimental +tool for generating automatically induction principles +corresponding to (possibly mutually recursive) functions. Its +syntax follows the schema: +\begin{quote} +{\tt Functional Scheme {\ident$_1$} := Induction for \ident'$_1$ Sort {\sort$_1$} \\ + with\\ + \mbox{}\hspace{0.1cm} \dots\ \\ + with {\ident$_m$} := Induction for {\ident'$_m$} Sort + {\sort$_m$}} +\end{quote} +where \ident'$_1$ \dots\ \ident'$_m$ are different mutually defined function +names (they must be in the same order as when they were defined). +This command generates the induction principles +\ident$_1$\dots\ident$_m$, following the recursive structure and case +analyses of the functions \ident'$_1$ \dots\ \ident'$_m$. + +\Rem +There is a difference between obtaining an induction scheme by using +\texttt{Functional Scheme} on a function defined by \texttt{Function} +or not. Indeed \texttt{Function} generally produces smaller +principles, closer to the definition written by the user. + +\firstexample +\example{Induction scheme for \texttt{div2}} +\label{FunScheme-examples} + +We define the function \texttt{div2} as follows: + +\begin{coq_eval} +Reset Initial. +\end{coq_eval} + +\begin{coq_example*} +Require Import Arith. +Fixpoint div2 (n:nat) : nat := + match n with + | O => 0 + | S O => 0 + | S (S n') => S (div2 n') + end. +\end{coq_example*} + +The definition of a principle of induction corresponding to the +recursive structure of \texttt{div2} is defined by the command: + +\begin{coq_example} +Functional Scheme div2_ind := Induction for div2 Sort Prop. +\end{coq_example} + +You may now look at the type of {\tt div2\_ind}: + +\begin{coq_example} +Check div2_ind. +\end{coq_example} + +We can now prove the following lemma using this principle: + +\begin{coq_example*} +Lemma div2_le' : forall n:nat, div2 n <= n. +intro n. + pattern n , (div2 n). +\end{coq_example*} + +\begin{coq_example} +apply div2_ind; intros. +\end{coq_example} + +\begin{coq_example*} +auto with arith. +auto with arith. +simpl; auto with arith. +Qed. +\end{coq_example*} + +We can use directly the \texttt{functional induction} +(\ref{FunInduction}) tactic instead of the pattern/apply trick: +\tacindex{functional induction} + +\begin{coq_example*} +Reset div2_le'. +Lemma div2_le : forall n:nat, div2 n <= n. +intro n. +\end{coq_example*} + +\begin{coq_example} +functional induction (div2 n). +\end{coq_example} + +\begin{coq_example*} +auto with arith. +auto with arith. +auto with arith. +Qed. +\end{coq_example*} + +\Rem There is a difference between obtaining an induction scheme for a +function by using \texttt{Function} (see Section~\ref{Function}) and by +using \texttt{Functional Scheme} after a normal definition using +\texttt{Fixpoint} or \texttt{Definition}. See \ref{Function} for +details. + + +\example{Induction scheme for \texttt{tree\_size}} + +\begin{coq_eval} +Reset Initial. +\end{coq_eval} + +We define trees by the following mutual inductive type: + +\begin{coq_example*} +Variable A : Set. +Inductive tree : Set := + node : A -> forest -> tree +with forest : Set := + | empty : forest + | cons : tree -> forest -> forest. +\end{coq_example*} + +We define the function \texttt{tree\_size} that computes the size +of a tree or a forest. Note that we use \texttt{Function} which +generally produces better principles. + +\begin{coq_example*} +Function 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 + | empty => 0 + | cons t f' => (tree_size t + forest_size f') + end. +\end{coq_example*} + +\Rem \texttt{Function} generates itself non mutual induction +principles {\tt tree\_size\_ind} and {\tt forest\_size\_ind}: + +\begin{coq_example} +Check tree_size_ind. +\end{coq_example} + +The definition of mutual induction principles following the recursive +structure of \texttt{tree\_size} and \texttt{forest\_size} is defined +by the command: + +\begin{coq_example*} +Functional Scheme tree_size_ind2 := Induction for tree_size Sort Prop +with forest_size_ind2 := Induction for forest_size Sort Prop. +\end{coq_example*} + +You may now look at the type of {\tt tree\_size\_ind2}: + +\begin{coq_example} +Check tree_size_ind2. +\end{coq_example} + +\section{Generation of inversion principles with \tt Derive Inversion} +\label{Derive-Inversion} +\comindex{Derive Inversion} + +The syntax of {\tt Derive Inversion} follows the schema: +\begin{quote} +{\tt Derive Inversion {\ident} with forall + $(\vec{x} : \vec{T})$, $I~\vec{t}$ Sort \sort} +\end{quote} + +This command generates an inversion principle for the +\texttt{inversion \dots\ using} tactic. +\tacindex{inversion \dots\ using} +Let $I$ be an inductive predicate and $\vec{x}$ the variables +occurring in $\vec{t}$. This command generates and stocks the +inversion lemma for the sort \sort~ corresponding to the instance +$\forall (\vec{x}:\vec{T}), I~\vec{t}$ with the name {\ident} in the {\bf +global} environment. When applied, it is equivalent to having inverted +the instance with the tactic {\tt inversion}. + +\begin{Variants} +\item \texttt{Derive Inversion\_clear {\ident} with forall + $(\vec{x}:\vec{T})$, $I~\vec{t}$ Sort \sort}\\ + \comindex{Derive Inversion\_clear} + When applied, it is equivalent to having + inverted the instance with the tactic \texttt{inversion} + replaced by the tactic \texttt{inversion\_clear}. +\item \texttt{Derive Dependent Inversion {\ident} with forall + $(\vec{x}:\vec{T})$, $I~\vec{t}$ Sort \sort}\\ + \comindex{Derive Dependent Inversion} + When applied, it is equivalent to having + inverted the instance with the tactic \texttt{dependent inversion}. +\item \texttt{Derive Dependent Inversion\_clear {\ident} with forall + $(\vec{x}:\vec{T})$, $I~\vec{t}$ Sort \sort}\\ + \comindex{Derive Dependent Inversion\_clear} + When applied, it is equivalent to having + inverted the instance with the tactic \texttt{dependent inversion\_clear}. +\end{Variants} + +\Example + +Let us consider the relation \texttt{Le} over natural numbers and the +following variable: + +\begin{coq_eval} +Reset Initial. +\end{coq_eval} + +\begin{coq_example*} +Inductive Le : nat -> nat -> Set := + | LeO : forall n:nat, Le 0 n + | LeS : forall n m:nat, Le n m -> Le (S n) (S m). +Variable P : nat -> nat -> Prop. +\end{coq_example*} + +To generate the inversion lemma for the instance +\texttt{(Le (S n) m)} and the sort \texttt{Prop}, we do: + +\begin{coq_example*} +Derive Inversion_clear leminv with (forall n m:nat, Le (S n) m) Sort Prop. +\end{coq_example*} + +\begin{coq_example} +Check leminv. +\end{coq_example} + +Then we can use the proven inversion lemma: + +\begin{coq_eval} +Lemma ex : forall n m:nat, Le (S n) m -> P n m. +intros. +\end{coq_eval} + +\begin{coq_example} +Show. +\end{coq_example} + +\begin{coq_example} +inversion H using leminv. +\end{coq_example} + diff --git a/doc/refman/RefMan-tac.tex b/doc/refman/RefMan-tac.tex index f35596f910..7315aec35f 100644 --- a/doc/refman/RefMan-tac.tex +++ b/doc/refman/RefMan-tac.tex @@ -6,15 +6,15 @@ A deduction rule is a link between some (unique) formula, that we call the {\em conclusion} and (several) formulas that we call the {\em -premises}. Indeed, a deduction rule can be read in two ways. The first -one has the shape: {\it ``if I know this and this then I can deduce +premises}. A deduction rule can be read in two ways. The first +one says: {\it ``if I know this and this then I can deduce this''}. For instance, if I have a proof of $A$ and a proof of $B$ then I have a proof of $A \land B$. This is forward reasoning from premises to conclusion. The other way says: {\it ``to prove this I have to prove this and this''}. For instance, to prove $A \land B$, I have to prove $A$ and I have to prove $B$. This is backward reasoning -which proceeds from conclusion to premises. We say that the conclusion -is {\em the goal}\index{goal} to prove and premises are {\em the +from conclusion to premises. We say that the conclusion +is the {\em goal}\index{goal} to prove and premises are the {\em subgoals}\index{subgoal}. The tactics implement {\em backward reasoning}. When applied to a goal, a tactic replaces this goal with the subgoals it generates. We say that a tactic reduces a goal to its @@ -25,29 +25,23 @@ Each (sub)goal is denoted with a number. The current goal is numbered address a particular goal in the list by writing {\sl n:\tac} which means {\it ``apply tactic {\tac} to goal number {\sl n}''}. We can show the list of subgoals by typing {\tt Show} (see -Section~\ref{Show}). +Section~\ref{Show}). 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 to a given goal, the system checks that some {\em preconditions} are satisfied. If it is not the case, the tactic raises an error message. -Tactics are build from atomic tactics and tactic expressions (which +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{TacticLanguage}. -There are, at least, three levels of atomic tactics. The simplest one -implements basic rules of the logical framework. The second level is -the one of {\em derived rules} which are built by combination of other -tactics. The third one implements heuristics or decision procedures to -build a complete proof of a goal. - \section{Invocation of tactics \label{tactic-syntax} \index{tactic@{\tac}}} -A tactic is applied as an ordinary command. If the tactic does not +A tactic is applied as an ordinary command. If the tactic is not meant to address the first subgoal, the command may be preceded by the wished subgoal number as shown below: @@ -56,11 +50,107 @@ subgoal number as shown below: & $|$ & {\tac} {\tt .} \end{tabular} -\section{Explicit proof as a term} +\subsection{Bindings list +\index{Binding list} +\label{Binding-list}} + +Tactics that take a term as argument may also support a bindings list, so +as to instantiate some parameters of the term by name or position. +The general form of a term equipped with a bindings list is {\tt +{\term} with {\bindinglist}} where {\bindinglist} may be of two +different forms: + +\begin{itemize} +\item In a bindings list of the form {\tt (\vref$_1$ := \term$_1$) + \dots\ (\vref$_n$ := \term$_n$)}, {\vref} is either an {\ident} or a + {\num}. The references are determined according to the type of + {\term}. If \vref$_i$ is an identifier, this identifier has to be + bound in the type of {\term} and the binding provides the tactic + with an instance for the parameter of this name. If \vref$_i$ is + some number $n$, this number denotes the $n$-th non dependent + premise of the {\term}, as determined by the type of {\term}. + + \ErrMsg \errindex{No such binder} + +\item A bindings list can also be a simple list of terms {\tt + \term$_1$ \dots\ \term$_n$}. In that case the references to + which these terms correspond are determined by the tactic. In case + of {\tt induction}, {\tt destruct}, {\tt elim} and {\tt case} (see + Section~\ref{elim}) the terms have to provide instances for all the + dependent products in the type of \term\ while in the case of {\tt + apply}, or of {\tt constructor} and its variants, only instances for + the dependent products that are not bound in the conclusion of the + type are required. + + \ErrMsg \errindex{Not the right number of missing arguments} +\end{itemize} + +\subsection{Occurrences sets and occurrences clauses} +\label{Occurrences clauses} +\index{Occurrences clauses} + +An occurrences clause is a modifier to some tactics that obeys the +following syntax: + +\begin{tabular}{lcl} +{\occclause} & ::= & {\tt in} {\occgoalset} \\ +{\occgoalset} & ::= & + \zeroone{{\ident$_1$} \zeroone{\atoccurrences} {\tt ,} \\ +& & {\dots} {\tt ,}\\ +& & {\ident$_m$} \zeroone{\atoccurrences}}\\ +& & \zeroone{{\tt |-} \zeroone{{\tt *} \zeroone{\atoccurrences}}}\\ +& | & + {\tt *} {\tt |-} \zeroone{{\tt *} \zeroone{\atoccurrences}}\\ +& | & + {\tt *}\\ +{\atoccurrences} & ::= & {\tt at} {\occlist}\\ +{\occlist} & ::= & \zeroone{{\tt -}} {\num$_1$} \dots\ {\num$_n$} +\end{tabular} + +The role of an occurrence clause is to select a set of occurrences of +a {\term} in a goal. In the first case, the {{\ident$_i$} +\zeroone{{\tt at} {\num$_1^i$} \dots\ {\num$_{n_i}^i$}}} parts +indicate that occurrences have to be selected in the hypotheses named +{\ident$_i$}. If no numbers are given for hypothesis {\ident$_i$}, +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 {\tt Set Printing All} (see +Section~\ref{SetPrintingAll}), counting from left to right. In +particular, occurrences of {\term} in implicit arguments (see +Section~\ref{Implicit Arguments}) or coercions (see +Section~\ref{Coercions}) are counted. + +If a minus sign is given between {\tt at} and the list of occurrences, +it negates the condition so that the clause denotes all the occurrences except +the ones explicitly mentioned after the minus sign. + +As an exception to the left-to-right order, the occurrences in the +{\tt return} subexpression of a {\tt match} are considered {\em +before} the occurrences in the matched term. + +In the second case, the {\tt *} on the left of {\tt |-} means that +all occurrences of {\term} are selected in every hypothesis. + +In the first and second case, if {\tt *} is mentioned on the right of +{\tt |-}, the occurrences of the conclusion of the goal have to be +selected. If some numbers are given, then only the occurrences denoted +by these numbers are selected. In no numbers are given, all +occurrences of {\term} in the goal are selected. + +Finally, the last notation is an abbreviation for {\tt * |- *}. Note +also that {\tt |-} is optional in the first case when no {\tt *} is +given. + +Here are some tactics that understand occurrences clauses: +{\tt set}, {\tt remember}, {\tt induction}, {\tt destruct}. + +\SeeAlso~Sections~\ref{tactic:set}, \ref{Tac-induction}, \ref{SetPrintingAll}. -\subsection{\tt exact \term +\section{Applying theorems} + +\subsection{\tt exact \term} \tacindex{exact} -\label{exact}} +\label{exact} This tactic applies to any goal. It gives directly the exact proof term of the goal. Let {\T} be our goal, let {\tt p} be a term of type @@ -72,48 +162,17 @@ convertible (see Section~\ref{conv-rules}). \end{ErrMsgs} \begin{Variants} - \item \texttt{eexact \term}\tacindex{eexact} - - This tactic behaves like \texttt{exact} but is able to handle terms with meta-variables. - -\end{Variants} - + \item \texttt{eexact \term}\tacindex{eexact} -\subsection{\tt refine \term -\tacindex{refine} -\label{refine} -\index{?@{\texttt{?}}}} - -This tactic allows to give an exact proof but still with some -holes. The holes are noted ``\texttt{\_}''. - -\begin{ErrMsgs} -\item \errindex{invalid argument}: - the tactic \texttt{refine} doesn't know what to do - with the term you gave. -\item \texttt{Refine passed ill-formed term}: the term you gave is not - a valid proof (not easy to debug in general). - This message may also occur in higher-level tactics, which call - \texttt{refine} internally. -\item \errindex{Cannot infer a term for this placeholder} - there is a hole in the term you gave - which type cannot be inferred. Put a cast around it. -\end{ErrMsgs} + This tactic behaves like \texttt{exact} but is able to handle terms + and goals with meta-variables. -An example of use is given in Section~\ref{refine-example}. - -\section{Basics -\index{Typing rules}} - -Tactics presented in this section implement the basic typing rules of -{\CIC} given in Chapter~\ref{Cic}. +\end{Variants} -\subsection{{\tt assumption} -\tacindex{assumption}} +\subsection{\tt assumption} +\tacindex{assumption} -This tactic applies to any goal. It implements the -``Var''\index{Typing rules!Var} rule given in -Section~\ref{Typed-terms}. It looks in the local context for an +This tactic looks in the local context for an hypothesis which type is equal to the goal. If it is the case, the subgoal is proved. Otherwise, it fails. @@ -130,389 +189,299 @@ subgoal is proved. Otherwise, it fails. \end{Variants} +\subsection{\tt refine \term} +\tacindex{refine} +\label{refine} +\label{refine-example} +\index{?@{\texttt{?}}} -\subsection{\tt clear {\ident} -\tacindex{clear} -\label{clear}} - -This tactic erases the hypothesis named {\ident} in the local context -of the current goal. Then {\ident} is no more displayed and no more -usable in the proof development. - -\begin{Variants} - -\item {\tt clear {\ident$_1$} {\ldots} {\ident$_n$}} - - This is equivalent to {\tt clear {\ident$_1$}. {\ldots} clear - {\ident$_n$}.} - -\item {\tt clearbody {\ident}}\tacindex{clearbody} - - This tactic expects {\ident} to be a local definition then clears - its body. Otherwise said, this tactic turns a definition into an - assumption. - -\item \texttt{clear - {\ident$_1$} {\ldots} {\ident$_n$}} +This tactic applies to any goal. It behaves like {\tt exact} with a big +difference: the user can leave some holes (denoted by \texttt{\_} or +{\tt (\_:\type)}) in the term. {\tt refine} will generate as +many subgoals as there are holes in the term. The type of holes must be +either synthesized by the system or declared by an +explicit cast like \verb|(_:nat->Prop)|. This low-level +tactic can be useful to advanced users. - This tactic clears all hypotheses except the ones depending in - the hypotheses named {\ident$_1$} {\ldots} {\ident$_n$} and in the - goal. +\Example -\item \texttt{clear} +\begin{coq_example*} +Inductive Option : Set := + | Fail : Option + | Ok : bool -> Option. +\end{coq_example} +\begin{coq_example} +Definition get : forall x:Option, x <> Fail -> bool. +refine + (fun x:Option => + match x return x <> Fail -> bool with + | Fail => _ + | Ok b => fun _ => b + end). +intros; absurd (Fail = Fail); trivial. +\end{coq_example} +\begin{coq_example*} +Defined. +\end{coq_example*} - This tactic clears all hypotheses except the ones depending in - goal. +\begin{ErrMsgs} +\item \errindex{invalid argument}: + the tactic \texttt{refine} does not know what to do + with the term you gave. +\item \texttt{Refine passed ill-formed term}: the term you gave is not + a valid proof (not easy to debug in general). + This message may also occur in higher-level tactics that call + \texttt{refine} internally. +\item \errindex{Cannot infer a term for this placeholder}: + there is a hole in the term you gave + which type cannot be inferred. Put a cast around it. +\end{ErrMsgs} -\item {\tt clear dependent \ident \tacindex{clear dependent}} +\subsection{\tt apply \term} +\tacindex{apply} +\label{apply} - This clears the hypothesis \ident\ and all hypotheses - which depend on it. +This tactic applies to any goal. The argument {\term} is a term +well-formed in the local context. The tactic {\tt apply} tries to +match the current goal against the conclusion of the type of {\term}. +If it succeeds, then the tactic returns as many subgoals as the number +of non-dependent premises of the type of {\term}. If the conclusion of +the type of {\term} does not match the goal {\em and} the conclusion +is an inductive type isomorphic to a tuple type, then each component +of the tuple is recursively matched to the goal in the left-to-right +order. -\end{Variants} +The tactic {\tt apply} relies on first-order unification with +dependent types unless the conclusion of the type of {\term} is of the +form {\tt ($P$ $t_1$ \dots\ $t_n$)} with $P$ to be instantiated. In +the latter case, the behavior depends on the form of the goal. If the +goal is of the form {\tt (fun $x$ => $Q$)~$u_1$~\ldots~$u_n$} and the +$t_i$ and $u_i$ unifies, then $P$ is taken to be {\tt (fun $x$ => $Q$)}. +Otherwise, {\tt apply} tries to define $P$ by abstracting over +$t_1$~\ldots ~$t_n$ in the goal. See {\tt pattern} in +Section~\ref{pattern} to transform the goal so that it gets the form +{\tt (fun $x$ => $Q$)~$u_1$~\ldots~$u_n$}. \begin{ErrMsgs} -\item \errindex{{\ident} not found} -\item \errindexbis{{\ident} is used in the conclusion}{is used in the - conclusion} -\item \errindexbis{{\ident} is used in the hypothesis {\ident'}}{is - used in the hypothesis} -\end{ErrMsgs} +\item \errindex{Impossible to unify \dots\ with \dots} -\subsection{\tt move {\ident$_1$} after {\ident$_2$} -\tacindex{move} -\label{move}} + The {\tt apply} + tactic failed to match the conclusion of {\term} and the current goal. + You can help the {\tt apply} tactic by transforming your + goal with the {\tt change} or {\tt pattern} tactics (see + sections~\ref{pattern},~\ref{change}). -This moves the hypothesis named {\ident$_1$} in the local context -after the hypothesis named {\ident$_2$}. +\item \errindex{Unable to find an instance for the variables +{\ident} \dots\ {\ident}} -If {\ident$_1$} comes before {\ident$_2$} in the order of dependences, -then all hypotheses between {\ident$_1$} and {\ident$_2$} which -(possibly indirectly) depend on {\ident$_1$} are moved also. + 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: -If {\ident$_1$} comes after {\ident$_2$} in the order of dependences, -then all hypotheses between {\ident$_1$} and {\ident$_2$} which -(possibly indirectly) occur in {\ident$_1$} are moved also. +\end{ErrMsgs} \begin{Variants} -\item {\tt move {\ident$_1$} before {\ident$_2$}} +\item{\tt apply {\term} with {\term$_1$} \dots\ {\term$_n$}} + \tacindex{apply \dots\ with} -This moves {\ident$_1$} towards and just before the hypothesis named {\ident$_2$}. + Provides {\tt apply} with explicit instantiations for all dependent + premises of the type of {\term} which do not occur in the conclusion + and consequently cannot be found by unification. Notice that + {\term$_1$} \mbox{\dots} {\term$_n$} must be given according to the order + of these dependent premises of the type of {\term}. -\item {\tt move {\ident} at top} + \ErrMsg \errindex{Not the right number of missing arguments} -This moves {\ident} at the top of the local context (at the beginning of the context). +\item{\tt apply {\term} with ({\vref$_1$} := {\term$_1$}) \dots\ ({\vref$_n$} + := {\term$_n$})} -\item {\tt move {\ident} at bottom} + This also provides {\tt apply} with values for instantiating + premises. Here, variables are referred by names and non-dependent + products by increasing numbers (see syntax in Section~\ref{Binding-list}). -This moves {\ident} at the bottom of the local context (at the end of the context). +\item {\tt apply} {\term$_1$} {\tt ,} \ldots {\tt ,} {\term$_n$} -\end{Variants} + This is a shortcut for {\tt apply} {\term$_1$} {\tt ; [ ..~|} + \ldots~{\tt ; [ ..~| {\tt apply} {\term$_n$} ]} \ldots~{\tt ]}, i.e. for the + successive applications of {\term$_{i+1}$} on the last subgoal + generated by {\tt apply} {\term$_i$}, starting from the application + of {\term$_1$}. -\begin{ErrMsgs} +\item {\tt eapply \term}\tacindex{eapply}\label{eapply} -\item \errindex{{\ident$_i$} not found} + The tactic {\tt eapply} behaves like {\tt apply} but it does not fail + when no instantiations are deducible for some variables in the + premises. Rather, it turns these variables into so-called + existential variables which are variables still to instantiate. An + existential variable is identified by a name of the form {\tt ?$n$} + where $n$ is a number. The instantiation is intended to be found + later in the proof. -\item \errindex{Cannot move {\ident$_1$} after {\ident$_2$}: - it occurs in {\ident$_2$}} +\item {\tt simple apply {\term}} \tacindex{simple apply} -\item \errindex{Cannot move {\ident$_1$} after {\ident$_2$}: - it depends on {\ident$_2$}} + This behaves like {\tt apply} but it reasons modulo conversion only + on subterms that contain no variables to instantiate. For instance, + the following example does not succeed because it would require the + conversion of {\tt id ?1234} and {\tt O}. -\end{ErrMsgs} +\begin{coq_eval} +Reset Initial. +\end{coq_eval} +\begin{coq_example*} +Definition id (x : nat) := x. +Hypothesis H : forall y, id y = y. +Goal O = O. +\end{coq_example*} +\begin{coq_example} +simple apply H. +\end{coq_example} -\subsection{\tt rename {\ident$_1$} into {\ident$_2$} -\tacindex{rename}} + Because it reasons modulo a limited amount of conversion, {\tt + simple apply} fails quicker than {\tt apply} and it is then + well-suited for uses in used-defined tactics that backtrack often. + Moreover, it does not traverse tuples as {\tt apply} does. -This renames hypothesis {\ident$_1$} into {\ident$_2$} in the current -context\footnote{but it does not rename the hypothesis in the - proof-term...} +\item \zeroone{{\tt simple}} {\tt apply} {\term$_1$} \zeroone{{\tt with} + {\bindinglist$_1$}} {\tt ,} \ldots {\tt ,} {\term$_n$} \zeroone{{\tt with} + {\bindinglist$_n$}}\\ + \zeroone{{\tt simple}} {\tt eapply} {\term$_1$} \zeroone{{\tt with} + {\bindinglist$_1$}} {\tt ,} \ldots {\tt ,} {\term$_n$} \zeroone{{\tt with} + {\bindinglist$_n$}} -\begin{Variants} + This summarizes the different syntaxes for {\tt apply} and {\tt eapply}. -\item {\tt rename {\ident$_1$} into {\ident$_2$}, \ldots, - {\ident$_{2k-1}$} into {\ident$_{2k}$}} +\item {\tt lapply {\term}} \tacindex{lapply} + + This tactic applies to any goal, say {\tt G}. The argument {\term} + has to be well-formed in the current context, its type being + reducible to a non-dependent product {\tt A -> B} with {\tt B} + possibly containing products. Then it generates two subgoals {\tt + B->G} and {\tt A}. Applying {\tt lapply H} (where {\tt H} has type + {\tt A->B} and {\tt B} does not start with a product) does the same + as giving the sequence {\tt cut B. 2:apply H.} where {\tt cut} is + described below. - Is equivalent to the sequence of the corresponding atomic {\tt rename}. + \Warning When {\term} contains more than one non + dependent product the tactic {\tt lapply} only takes into account the + first product. \end{Variants} -\begin{ErrMsgs} - -\item \errindex{{\ident$_1$} not found} - -\item \errindexbis{{\ident$_2$} is already used}{is already used} - -\end{ErrMsgs} - -\subsection{\tt intro -\tacindex{intro} -\label{intro}} - -This tactic applies to a goal which is either a product or starts with -a let binder. If the goal is a product, the tactic implements the -``Lam''\index{Typing rules!Lam} rule given in -Section~\ref{Typed-terms}\footnote{Actually, only the second subgoal will be -generated since the other one can be automatically checked.}. If the -goal starts with a let binder then the tactic implements a mix of the -``Let''\index{Typing rules!Let} and ``Conv''\index{Typing rules!Conv}. - -If the current goal is a dependent product {\tt forall $x$:$T$, $U$} (resp {\tt -let $x$:=$t$ in $U$}) then {\tt intro} puts {\tt $x$:$T$} (resp {\tt $x$:=$t$}) - in the local context. -% Obsolete (quantified names already avoid hypotheses names): -% Otherwise, it puts -% {\tt x}{\it n}{\tt :T} where {\it n} is such that {\tt x}{\it n} is a -%fresh name. -The new subgoal is $U$. -% If the {\tt x} has been renamed {\tt x}{\it n} then it is replaced -% by {\tt x}{\it n} in {\tt U}. - -If the goal is a non dependent product {\tt $T$ -> $U$}, then it puts -in the local context either {\tt H}{\it n}{\tt :$T$} (if $T$ is of -type {\tt Set} or {\tt Prop}) or {\tt X}{\it n}{\tt :$T$} (if the type -of $T$ is {\tt Type}). The optional index {\it n} is such that {\tt -H}{\it n} or {\tt X}{\it n} is a fresh identifier. -In both cases the new subgoal is $U$. - -If the goal is neither a product nor starting with a let definition, -the tactic {\tt intro} applies the tactic {\tt red} until the tactic -{\tt intro} can be applied or the goal is not reducible. - -\begin{ErrMsgs} -\item \errindex{No product even after head-reduction} -\item \errindexbis{{\ident} is already used}{is already used} -\end{ErrMsgs} - -\begin{Variants} - -\item {\tt intros}\tacindex{intros} - - Repeats {\tt intro} until it meets the head-constant. It never reduces - head-constants and it never fails. - -\item {\tt intro {\ident}} - - Applies {\tt intro} but forces {\ident} to be the name of the - introduced hypothesis. - - \ErrMsg \errindex{name {\ident} is already used} - - \Rem If a name used by {\tt intro} hides the base name of a global - constant then the latter can still be referred to by a qualified name - (see \ref{LongNames}). - -\item {\tt intros \ident$_1$ \mbox{\dots} \ident$_n$} - - Is equivalent to the composed tactic {\tt intro \ident$_1$; \mbox{\dots} ; - intro \ident$_n$}. - - More generally, the \texttt{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{intros-pattern}. - -\item {\tt intros until {\ident}} \tacindex{intros until} - - Repeats {\tt intro} until it meets a premise of the goal having form - {\tt (} {\ident}~{\tt :}~{\term} {\tt )} and discharges the variable - named {\ident} of the current goal. - - \ErrMsg \errindex{No such hypothesis in current goal} - -\item {\tt intros until {\num}} \tacindex{intros until} - - Repeats {\tt intro} until the {\num}-th non-dependent product. For - instance, on the subgoal % - \verb+forall x y:nat, x=y -> y=x+ the tactic \texttt{intros until 1} - is equivalent to \texttt{intros x y H}, as \verb+x=y -> y=x+ is the - first non-dependent product. And on the subgoal % - \verb+forall x y z:nat, x=y -> y=x+ the tactic \texttt{intros until 1} - is equivalent to \texttt{intros x y z} as the product on \texttt{z} - can be rewritten as a non-dependent product: % - \verb+forall x y:nat, nat -> x=y -> y=x+ - - - \ErrMsg \errindex{No such hypothesis in current goal} - - Happens when {\num} is 0 or is greater than the number of non-dependent - products of the goal. - -\item {\tt intro after \ident} \tacindex{intro after}\\ - {\tt intro before \ident} \tacindex{intro before}\\ - {\tt intro at top} \tacindex{intro at top}\\ - {\tt intro at bottom} \tacindex{intro at bottom} - - Applies {\tt intro} and moves the freshly introduced hypothesis - respectively after the hypothesis \ident{}, before the hypothesis - \ident{}, at the top of the local context, or at the bottom of the - local context. All hypotheses on which the new hypothesis depends - are moved too so as to respect the order of dependencies between - hypotheses. Note that {\tt intro at bottom} is a synonym for {\tt - intro} with no argument. - -\begin{ErrMsgs} -\item \errindex{No product even after head-reduction} -\item \errindex{No such hypothesis} : {\ident} -\end{ErrMsgs} - -\item {\tt intro \ident$_1$ after \ident$_2$}\\ - {\tt intro \ident$_1$ before \ident$_2$}\\ - {\tt intro \ident$_1$ at top}\\ - {\tt intro \ident$_1$ at bottom} - - Behaves as previously but naming the introduced hypothesis - \ident$_1$. It is equivalent to {\tt intro \ident$_1$} followed by - the appropriate call to {\tt move}~(see Section~\ref{move}). - -\begin{ErrMsgs} -\item \errindex{No product even after head-reduction} -\item \errindex{No such hypothesis} : {\ident} -\end{ErrMsgs} - -\end{Variants} - -\subsection{\tt apply \term -\tacindex{apply} -\label{apply}} - -This tactic applies to any goal. The argument {\term} is a term -well-formed in the local context. The tactic {\tt apply} tries to -match the current goal against the conclusion of the type of {\term}. -If it succeeds, then the tactic returns as many subgoals as the number -of non dependent premises of the type of {\term}. If the conclusion of -the type of {\term} does not match the goal {\em and} the conclusion -is an inductive type isomorphic to a tuple type, then each component -of the tuple is recursively matched to the goal in the left-to-right -order. - -The tactic {\tt apply} relies on first-order unification with -dependent types unless the conclusion of the type of {\term} is of the -form {\tt ($P$~ $t_1$~\ldots ~$t_n$)} with $P$ to be instantiated. In -the latter case, the behavior depends on the form of the goal. If the -goal is of the form {\tt (fun $x$ => $Q$)~$u_1$~\ldots~$u_n$} and the -$t_i$ and $u_i$ unifies, then $P$ is taken to be (fun $x$ => $Q$). -Otherwise, {\tt apply} tries to define $P$ by abstracting over -$t_1$~\ldots ~$t_n$ in the goal. See {\tt pattern} in -Section~\ref{pattern} to transform the goal so that it gets the form -{\tt (fun $x$ => $Q$)~$u_1$~\ldots~$u_n$}. - -\begin{ErrMsgs} -\item \errindex{Impossible to unify \dots\ with \dots} - - The {\tt apply} - tactic failed to match the conclusion of {\term} and the current goal. - You can help the {\tt apply} tactic by transforming your - goal with the {\tt change} or {\tt pattern} tactics (see - sections~\ref{pattern},~\ref{change}). - -\item \errindex{Unable to find an instance for the variables -{\ident} \ldots {\ident}} +\Example +Assume we have a transitive relation {\tt R} on {\tt nat}: +\label{eapply-example} - 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: +\begin{coq_eval} +Reset Initial. +\end{coq_eval} +\begin{coq_example*} +Variable R : nat -> nat -> Prop. +Hypothesis Rtrans : forall x y z:nat, R x y -> R y z -> R x z. +Variables n m p : nat. +Hypothesis Rnm : R n m. +Hypothesis Rmp : R m p. +\end{coq_example*} -\end{ErrMsgs} +Consider the goal {\tt (R n p)} provable using the transitivity of +{\tt R}: -\begin{Variants} +\begin{coq_example*} +Goal R n p. +\end{coq_example*} -\item{\tt apply {\term} with {\term$_1$} \mbox{\dots} {\term$_n$}} - \tacindex{apply \mbox{\dots} with} - - Provides {\tt apply} with explicit instantiations for all dependent - premises of the type of {\term} which do not occur in the conclusion - and consequently cannot be found by unification. Notice that - {\term$_1$} \mbox{\dots} {\term$_n$} must be given according to the order - of these dependent premises of the type of {\term}. +The direct application of {\tt Rtrans} with {\tt apply} fails because +no value for {\tt y} in {\tt Rtrans} is found by {\tt apply}: - \ErrMsg \errindex{Not the right number of missing arguments} +%\begin{coq_eval} +%Set Printing Depth 50. +%(********** The following is not correct and should produce **********) +%(**** Error: generated subgoal (R n ?17) has metavariables in it *****) +%\end{coq_eval} +\begin{coq_example} +apply Rtrans. +\end{coq_example} -\item{\tt apply {\term} with ({\vref$_1$} := {\term$_1$}) \mbox{\dots} ({\vref$_n$} - := {\term$_n$})} - - This also provides {\tt apply} with values for instantiating - premises. Here, variables are referred by names and non-dependent - products by increasing numbers (see syntax in Section~\ref{Binding-list}). +A solution is to apply {\tt (Rtrans n m p)} or {\tt (Rtrans n m)}. -\item {\tt apply} {\term$_1$} {\tt ,} \ldots {\tt ,} {\term$_n$} +\begin{coq_example} +apply (Rtrans n m p). +\end{coq_example} - This is a shortcut for {\tt apply} {\term$_1$} {\tt ; [ ..~|} - \ldots~{\tt ; [ ..~| {\tt apply} {\term$_n$} ]} \ldots~{\tt ]}, i.e. for the - successive applications of {\term$_{i+1}$} on the last subgoal - generated by {\tt apply} {\term$_i$}, starting from the application - of {\term$_1$}. +\begin{coq_eval} +Undo. +\end{coq_eval} -\item {\tt eapply \term}\tacindex{eapply}\label{eapply} - - The tactic {\tt eapply} behaves as {\tt apply} but does not fail - when no instantiation are deducible for some variables in the - premises. Rather, it turns these variables into so-called - existential variables which are variables still to instantiate. An - existential variable is identified by a name of the form {\tt ?$n$} - where $n$ is a number. The instantiation is intended to be found - later in the proof. +Note that {\tt n} can be inferred from the goal, so the following would +work too. - An example of use of {\tt eapply} is given in - Section~\ref{eapply-example}. +\begin{coq_example*} +apply (Rtrans _ m). +\end{coq_example*} +\begin{coq_eval} +Undo. +\end{coq_eval} -\item {\tt simple apply {\term}} \tacindex{simple apply} +More elegantly, {\tt apply Rtrans with (y:=m)} allows to only mention +the unknown {\tt m}: - This behaves like {\tt apply} but it reasons modulo conversion only - on subterms that contain no variables to instantiate. For instance, - if {\tt id := fun x:nat => x} and {\tt H : forall y, id y = y} then - {\tt simple apply H} on goal {\tt O = O} does not succeed because it - would require the conversion of {\tt f ?y} and {\tt O} where {\tt - ?y} is a variable to instantiate. Tactic {\tt simple apply} does not - either traverse tuples as {\tt apply} does. +\begin{coq_example*} +apply Rtrans with (y := m). +\end{coq_example*} +\begin{coq_eval} +Undo. +\end{coq_eval} - Because it reasons modulo a limited amount of conversion, {\tt - simple apply} fails quicker than {\tt apply} and it is then - well-suited for uses in used-defined tactics that backtrack often. +Another solution is to mention the proof of {\tt (R x y)} in {\tt +Rtrans} \ldots -\item \zeroone{{\tt simple}} {\tt apply} {\term$_1$} \zeroone{{\tt with} - {\bindinglist$_1$}} {\tt ,} \ldots {\tt ,} {\term$_n$} \zeroone{{\tt with} - {\bindinglist$_n$}}\\ - \zeroone{{\tt simple}} {\tt eapply} {\term$_1$} \zeroone{{\tt with} - {\bindinglist$_1$}} {\tt ,} \ldots {\tt ,} {\term$_n$} \zeroone{{\tt with} - {\bindinglist$_n$}} +\begin{coq_example} +apply Rtrans with (1 := Rnm). +\end{coq_example} +\begin{coq_eval} +Undo. +\end{coq_eval} - This summarizes the different syntaxes for {\tt apply} and {\tt eapply}. +\ldots or the proof of {\tt (R y z)}. -\item {\tt lapply {\term}} \tacindex{lapply} +\begin{coq_example} +apply Rtrans with (2 := Rmp). +\end{coq_example} +\begin{coq_eval} +Undo. +\end{coq_eval} - This tactic applies to any goal, say {\tt G}. The argument {\term} - has to be well-formed in the current context, its type being - reducible to a non-dependent product {\tt A -> B} with {\tt B} - possibly containing products. Then it generates two subgoals {\tt - B->G} and {\tt A}. Applying {\tt lapply H} (where {\tt H} has type - {\tt A->B} and {\tt B} does not start with a product) does the same - as giving the sequence {\tt cut B. 2:apply H.} where {\tt cut} is - described below. +On the opposite, one can use {\tt eapply} which postpone the problem +of finding {\tt m}. Then one can apply the hypotheses {\tt Rnm} and {\tt +Rmp}. This instantiates the existential variable and completes the proof. - \Warning When {\term} contains more than one non - dependent product the tactic {\tt lapply} only takes into account the - first product. +\begin{coq_example} +eapply Rtrans. +apply Rnm. +apply Rmp. +\end{coq_example} -\end{Variants} +\begin{coq_eval} +Reset R. +\end{coq_eval} -\subsection{{\tt apply {\term} in {\ident}} -\tacindex{apply {\ldots} in}} +\subsection{\tt apply {\term} in {\ident}} +\tacindex{apply \dots\ in} This tactic applies to any goal. The argument {\term} is a term well-formed in the local context and the argument {\ident} is an hypothesis of the context. The tactic {\tt apply {\term} in {\ident}} -tries to match the conclusion of the type of {\ident} against a non -dependent premise of the type of {\term}, trying them from right to +tries to match the conclusion of the type of {\ident} against a +non-dependent premise of the type of {\term}, trying them from right to left. If it succeeds, the statement of hypothesis {\ident} is replaced by the conclusion of the type of {\term}. The tactic also -returns as many subgoals as the number of other non dependent premises -in the type of {\term} and of the non dependent premises of the type +returns as many subgoals as the number of other non-dependent premises +in the type of {\term} and of the non-dependent premises of the type of {\ident}. If the conclusion of the type of {\term} does not match the goal {\em and} the conclusion is an inductive type isomorphic to a tuple type, then the tuple is (recursively) decomposed and the first -component of the tuple of which a non dependent premise matches the +component of the tuple of which a non-dependent premise matches the conclusion of the type of {\ident}. Tuples are decomposed in a width-first left-to-right order (for instance if the type of {\tt H1} is a \verb=A <-> B= statement, and the type of {\tt H2} is \verb=A= @@ -538,12 +507,12 @@ This applies each of {\term} in sequence in {\ident}. \item {\tt apply \nelist{{\term} with {\bindinglist}}{,} in {\ident}} -This does the same but uses the bindings in each {\bindinglist} to +This does the same but uses the bindings in each {\bindinglist} to instantiate the parameters of the corresponding type of {\term} (see syntax of bindings in Section~\ref{Binding-list}). \item {\tt eapply \nelist{{\term} with {\bindinglist}}{,} in {\ident}} -\tacindex{eapply {\ldots} in} +\tacindex{eapply \dots\ in} This works as {\tt apply \nelist{{\term} with {\bindinglist}}{,} in {\ident}} but turns unresolved bindings into existential variables, if @@ -561,15 +530,15 @@ This works as {\tt apply \nelist{{\term}{,} with {\bindinglist}}{,} in This works as {\tt apply \nelist{{\term}{,} with {\bindinglist}}{,} in {\ident} as {\disjconjintropattern}} but using {\tt eapply}. \item {\tt simple apply {\term} in {\ident}} -\tacindex{simple apply {\ldots} in} -\tacindex{simple eapply {\ldots} in} +\tacindex{simple apply \dots\ in} +\tacindex{simple eapply \dots\ in} This behaves like {\tt apply {\term} in {\ident}} but it reasons modulo conversion only on subterms that contain no variables to instantiate. For instance, if {\tt id := fun x:nat => x} and {\tt H : - forall y, id y = y -> True} and {\tt H0 : O = O} then {\tt simple + forall y, id y = y -> True} and {\tt H0 :\ O = O} then {\tt simple apply H in H0} does not succeed because it would require the -conversion of {\tt f ?y} and {\tt O} where {\tt ?y} is a variable to +conversion of {\tt id ?1234} and {\tt O} where {\tt ?1234} is a variable to instantiate. Tactic {\tt simple apply {\term} in {\ident}} does not either traverse tuples as {\tt apply {\term} in {\ident}} does. @@ -580,1136 +549,1030 @@ This summarizes the different syntactic variants of {\tt apply {\term} in {\ident}} and {\tt eapply {\term} in {\ident}}. \end{Variants} -\subsection{{\tt set ( {\ident} {\tt :=} {\term} \tt )} -\label{tactic:set} -\tacindex{set} -\tacindex{pose} -\tacindex{remember}} +\subsection{\tt constructor \num} +\label{constructor} +\tacindex{constructor} -This replaces {\term} by {\ident} in the conclusion or in the -hypotheses of the current goal and adds the new definition {\ident -{\tt :=} \term} to the local context. The default is to make this -replacement only in the conclusion. +This tactic applies to a goal such that its conclusion is +an inductive type (say {\tt I}). The argument {\num} must be less +or equal to the numbers of constructor(s) of {\tt I}. Let {\tt ci} be +the {\tt i}-th constructor of {\tt I}, then {\tt constructor i} is +equivalent to {\tt intros; apply ci}. -If {\term} has holes (i.e. subexpressions of the form ``\_''), the -tactic first checks that all subterms matching the pattern are -compatible before doing the replacement using the leftmost subterm -matching the pattern. +\begin{ErrMsgs} +\item \errindex{Not an inductive product} +\item \errindex{Not enough constructors} +\end{ErrMsgs} \begin{Variants} +\item \texttt{constructor} -\item {\tt set (} {\ident} {\tt :=} {\term} {\tt ) in {\occgoalset}} + This tries \texttt{constructor 1} then \texttt{constructor 2}, + \dots\ , then \texttt{constructor} \textit{n} where \textit{n} is + the number of constructors of the head of the goal. -This notation allows to specify which occurrences of {\term} have to -be substituted in the context. The {\tt in {\occgoalset}} clause is an -occurrence clause whose syntax and behavior is described in -Section~\ref{Occurrences clauses}. +\item {\tt constructor \num~with} {\bindinglist} -\item {\tt set (} {\ident} \nelist{\binder}{} {\tt :=} {\term} {\tt )} + Let {\tt ci} be the {\tt i}-th constructor of {\tt I}, then {\tt + constructor i with \bindinglist} is equivalent to {\tt intros; + apply ci with \bindinglist}. - This is equivalent to {\tt set (} {\ident} {\tt :=} {\tt fun} - \nelist{\binder}{} {\tt =>} {\term} {\tt )}. + \Warning the terms in the \bindinglist\ are checked + in the context where {\tt constructor} is executed and not in the + context where {\tt apply} is executed (the introductions are not + taken into account). -\item {\tt set } {\term} +% To document? +% \item {\tt constructor {\tactic}} - This behaves as {\tt set (} {\ident} := {\term} {\tt )} but {\ident} - is generated by {\Coq}. This variant also supports an occurrence clause. +\item {\tt split}\tacindex{split} -\item {\tt set (} {\ident$_0$} \nelist{\binder}{} {\tt :=} {\term} - {\tt ) in {\occgoalset}}\\ - {\tt set {\term} in {\occgoalset}} + This applies only if {\tt I} has a single constructor. It is then + equivalent to {\tt constructor 1}. It is typically used in the case + of a conjunction $A\land B$. - These are the general forms which combine the previous possibilities. + \ErrMsg \errindex{Not an inductive goal with 1 constructor} -\item {\tt remember {\term} {\tt as} {\ident}} +\item {\tt exists {\bindinglist}}\tacindex{exists} - This behaves as {\tt set (} {\ident} := {\term} {\tt ) in *} and using a - logical (Leibniz's) equality instead of a local definition. + This applies only if {\tt I} has a single constructor. It is then + equivalent to {\tt intros; constructor 1 with \bindinglist}. It is + typically used in the case of an existential quantification $\exists + x, P(x)$. -\item {\tt remember {\term} {\tt as} {\ident} {\tt eqn:\ident}} + \ErrMsg \errindex{Not an inductive goal with 1 constructor} - This behaves as {\tt remember {\term} {\tt as} {\ident}}, except - that the name of the generated equality is also given. +\item {\tt exists \nelist{\bindinglist}{,}} -\item {\tt remember {\term} {\tt as} {\ident} in {\occgoalset}} + This iteratively applies {\tt exists {\bindinglist}}. - This is a more general form of {\tt remember} that remembers the - occurrences of {\term} specified by an occurrences set. +\item {\tt left}\tacindex{left}\\ + {\tt right}\tacindex{right} -\item {\tt pose ( {\ident} := {\term} )} - - This adds the local definition {\ident} := {\term} to the current - context without performing any replacement in the goal or in the - hypotheses. It is equivalent to {\tt set ( {\ident} {\tt :=} - {\term} {\tt ) in |-}}. + These tactics apply only if {\tt I} has two constructors, for instance + in the case of a + disjunction $A\lor B$. Then, they are respectively equivalent to {\tt + constructor 1} and {\tt constructor 2}. -\item {\tt pose (} {\ident} \nelist{\binder}{} {\tt :=} {\term} {\tt )} + \ErrMsg \errindex{Not an inductive goal with 2 constructors} - This is equivalent to {\tt pose (} {\ident} {\tt :=} {\tt fun} - \nelist{\binder}{} {\tt =>} {\term} {\tt )}. +\item {\tt left with \bindinglist}\\ + {\tt right with \bindinglist}\\ + {\tt split with \bindinglist} -\item{\tt pose {\term}} + As soon as the inductive type has the right number of constructors, + these expressions are equivalent to calling {\tt + constructor $i$ with \bindinglist} for the appropriate $i$. - This behaves as {\tt pose (} {\ident} := {\term} {\tt )} but - {\ident} is generated by {\Coq}. +\item \texttt{econstructor}\tacindex{econstructor}\\ + \texttt{eexists}\tacindex{eexists}\\ + \texttt{esplit}\tacindex{esplit}\\ + \texttt{eleft}\tacindex{eleft}\\ + \texttt{eright}\tacindex{eright} -\end{Variants} + These tactics and their variants behave like \texttt{constructor}, + \texttt{exists}, \texttt{split}, \texttt{left}, \texttt{right} and + their variants but they introduce existential variables instead of + failing when the instantiation of a variable cannot be found (cf + \texttt{eapply} and Section~\ref{eapply-example}). -\subsection{{\tt assert ( {\ident} : {\form} \tt )} -\tacindex{assert}} +\end{Variants} -This tactic applies to any goal. {\tt assert (H : U)} adds a new -hypothesis of name \texttt{H} asserting \texttt{U} to the current goal -and opens a new subgoal \texttt{U}\footnote{This corresponds to the - cut rule of sequent calculus.}. The subgoal {\texttt U} comes first -in the list of subgoals remaining to prove. +\section{Managing the local context} -\begin{ErrMsgs} -\item \errindex{Not a proposition or a type} - - Arises when the argument {\form} is neither of type {\tt Prop}, {\tt - Set} nor {\tt Type}. +\subsection{\tt intro} +\tacindex{intro} +\label{intro} -\end{ErrMsgs} +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''\index{Typing rules!Lam} rule given in +Section~\ref{Typed-terms}\footnote{Actually, only the second subgoal will be +generated since the other one can be automatically checked.}. If the +goal starts with a let binder, then the tactic implements a mix of the +``Let''\index{Typing rules!Let} and ``Conv''\index{Typing rules!Conv}. -\begin{Variants} +If the current goal is a dependent product $\forall x:T,~U$ (resp {\tt +let $x$:=$t$ in $U$}) then {\tt intro} puts {\tt $x$:$T$} (resp {\tt $x$:=$t$}) + in the local context. +% Obsolete (quantified names already avoid hypotheses names): +% Otherwise, it puts +% {\tt x}{\it n}{\tt :T} where {\it n} is such that {\tt x}{\it n} is a +%fresh name. +The new subgoal is $U$. +% If the {\tt x} has been renamed {\tt x}{\it n} then it is replaced +% by {\tt x}{\it n} in {\tt U}. -\item{\tt assert {\form}} - - This behaves as {\tt assert (} {\ident} : {\form} {\tt )} but - {\ident} is generated by {\Coq}. +If the goal is a non-dependent product $T \to U$, then it puts +in the local context either {\tt H}{\it n}{\tt :$T$} (if $T$ is of +type {\tt Set} or {\tt Prop}) or {\tt X}{\it n}{\tt :$T$} (if the type +of $T$ is {\tt Type}). The optional index {\it n} is such that {\tt +H}{\it n} or {\tt X}{\it n} is a fresh identifier. +In both cases, the new subgoal is $U$. -\item{\tt assert (} {\ident} := {\term} {\tt )} - - This behaves as {\tt assert ({\ident} : {\type});[exact - {\term}|idtac]} where {\type} is the type of {\term}. +If the goal is neither a product nor starting with a let definition, +the tactic {\tt intro} applies the tactic {\tt red} until the tactic +{\tt intro} can be applied or the goal is not reducible. -\item {\tt cut {\form}}\tacindex{cut} - - This tactic applies to any goal. It implements the non dependent - case of the ``App''\index{Typing rules!App} rule given in - Section~\ref{Typed-terms}. (This is Modus Ponens inference rule.) - {\tt cut U} transforms the current goal \texttt{T} into the two - following subgoals: {\tt U -> T} and \texttt{U}. The subgoal {\tt U - -> T} comes first in the list of remaining subgoal to prove. +\begin{ErrMsgs} +\item \errindex{No product even after head-reduction} +\item \errindexbis{{\ident} is already used}{is already used} +\end{ErrMsgs} -\item \texttt{assert {\form} by {\tac}}\tacindex{assert by} - - This tactic behaves like \texttt{assert} but applies {\tac} - to solve the subgoals generated by \texttt{assert}. +\begin{Variants} -\item \texttt{assert {\form} as {\intropattern}\tacindex{assert as}} +\item {\tt intros}\tacindex{intros} - If {\intropattern} is a naming introduction pattern (see - Section~\ref{intros-pattern}), the hypothesis is named after this - introduction pattern (in particular, if {\intropattern} is {\ident}, - the tactic behaves like \texttt{assert ({\ident} : {\form})}). + This repeats {\tt intro} until it meets the head-constant. It never reduces + head-constants and it never fails. - If {\intropattern} is a disjunctive/conjunctive introduction - pattern, the tactic behaves like \texttt{assert {\form}} then destructing the - resulting hypothesis using the given introduction pattern. +\item {\tt intro {\ident}} -\item \texttt{assert {\form} as {\intropattern} by {\tac}} + This applies {\tt intro} but forces {\ident} to be the name of the + introduced hypothesis. - This combines the two previous variants of {\tt assert}. + \ErrMsg \errindex{name {\ident} is already used} -\item \texttt{pose proof {\term} as {\intropattern}\tacindex{pose proof}} + \Rem If a name used by {\tt intro} hides the base name of a global + constant then the latter can still be referred to by a qualified name + (see \ref{LongNames}). - This tactic behaves like \texttt{assert T as {\intropattern} by - exact {\term}} where \texttt{T} is the type of {\term}. +\item {\tt intros \ident$_1$ \dots\ \ident$_n$} - In particular, \texttt{pose proof {\term} as {\ident}} behaves as - \texttt{assert ({\ident}:T) by exact {\term}} (where \texttt{T} is - the type of {\term}) and \texttt{pose proof {\term} as - {\disjconjintropattern}\tacindex{pose proof}} behaves - like \texttt{destruct {\term} as {\disjconjintropattern}}. + This is equivalent to the composed tactic {\tt intro \ident$_1$; \dots\ ; + intro \ident$_n$}. -\item {\tt specialize ({\ident} \term$_1$ {\ldots} \term$_n$)\tacindex{specialize}} \\ - {\tt specialize {\ident} with \bindinglist} + More generally, the \texttt{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{intros-pattern}. - The tactic {\tt specialize} works on local hypothesis \ident. - The premises of this hypothesis (either universal - quantifications or non-dependent implications) are instantiated - by concrete terms coming either from arguments \term$_1$ - $\ldots$ \term$_n$ or from a bindings list (see - Section~\ref{Binding-list} for more about bindings lists). In the - second form, all instantiation elements must be given, whereas - in the first form the application to \term$_1$ {\ldots} - \term$_n$ can be partial. The first form is equivalent to - {\tt assert (\ident':=\ident \term$_1$ {\ldots} \term$_n$); - clear \ident; rename \ident' into \ident}. +\item {\tt intros until {\ident}} \tacindex{intros until} - The name {\ident} can also refer to a global lemma or - hypothesis. In this case, for compatibility reasons, the - behavior of {\tt specialize} is close to that of {\tt - generalize}: the instantiated statement becomes an additional - premise of the goal. + This repeats {\tt intro} until it meets a premise of the goal having form + {\tt (} {\ident}~{\tt :}~{\term} {\tt )} and discharges the variable + named {\ident} of the current goal. -%% Moreover, the old syntax allows the use of a number after {\tt specialize} -%% for controlling the number of premises to instantiate. Giving this -%% number should not be mandatory anymore (automatic detection of how -%% many premises can be eaten without leaving meta-variables). Hence -%% no documentation for this integer optional argument of specialize + \ErrMsg \errindex{No such hypothesis in current goal} -\end{Variants} +\item {\tt intros until {\num}} \tacindex{intros until} -\subsection{\tt generalize \term -\tacindex{generalize} -\label{generalize}} + This repeats {\tt intro} until the {\num}-th non-dependent product. For + instance, on the subgoal % + \verb+forall x y:nat, x=y -> y=x+ the tactic \texttt{intros until 1} + is equivalent to \texttt{intros x y H}, as \verb+x=y -> y=x+ is the + first non-dependent product. And on the subgoal % + \verb+forall x y z:nat, x=y -> y=x+ the tactic \texttt{intros until 1} + is equivalent to \texttt{intros x y z} as the product on \texttt{z} + can be rewritten as a non-dependent product: % + \verb+forall x y:nat, nat -> x=y -> y=x+ -This tactic applies to any goal. It generalizes the conclusion w.r.t. -one subterm of it. For example: -\begin{coq_eval} -Goal forall x y:nat, (0 <= x + y + y). -intros. -\end{coq_eval} -\begin{coq_example} -Show. -generalize (x + y + y). -\end{coq_example} + \ErrMsg \errindex{No such hypothesis in current goal} -\begin{coq_eval} -Abort. -\end{coq_eval} + This happens when {\num} is 0 or is greater than the number of non-dependent + products of the goal. -If the goal is $G$ and $t$ is a subterm of type $T$ in the goal, then -{\tt generalize} \textit{t} replaces the goal by {\tt forall (x:$T$), $G'$} -where $G'$ is obtained from $G$ by replacing all occurrences of $t$ by -{\tt x}. The name of the variable (here {\tt n}) is chosen based on $T$. +\item {\tt intro after \ident} \tacindex{intro after}\\ + {\tt intro before \ident} \tacindex{intro before}\\ + {\tt intro at top} \tacindex{intro at top}\\ + {\tt intro at bottom} \tacindex{intro at bottom} -\begin{Variants} -\item {\tt generalize {\term$_1$ , \mbox{\dots} , \term$_n$}} - - Is equivalent to {\tt generalize \term$_n$; \mbox{\dots} ; generalize - \term$_1$}. Note that the sequence of \term$_i$'s are processed - from $n$ to $1$. + These tactics apply {\tt intro} and move the freshly introduced hypothesis + respectively after the hypothesis \ident{}, before the hypothesis + \ident{}, at the top of the local context, or at the bottom of the + local context. All hypotheses on which the new hypothesis depends + are moved too so as to respect the order of dependencies between + hypotheses. Note that {\tt intro at bottom} is a synonym for {\tt + intro} with no argument. -\item {\tt generalize {\term} at {\num$_1$ \mbox{\dots} \num$_i$}} - - Is equivalent to {\tt generalize \term} but generalizing only over - the specified occurrences of {\term} (counting from left to right on the - expression printed using option {\tt Set Printing All}). + \ErrMsg \errindex{No such hypothesis} : {\ident} -\item {\tt generalize {\term} as {\ident}} - - Is equivalent to {\tt generalize \term} but use {\ident} to name the - generalized hypothesis. +\item {\tt intro \ident$_1$ after \ident$_2$}\\ + {\tt intro \ident$_1$ before \ident$_2$}\\ + {\tt intro \ident$_1$ at top}\\ + {\tt intro \ident$_1$ at bottom} -\item {\tt generalize {\term$_1$} at {\num$_{11}$ \mbox{\dots} \num$_{1i_1}$} - as {\ident$_1$} - , {\ldots} , - {\term$_n$} at {\num$_{n1}$ \mbox{\dots} \num$_{ni_n}$} - as {\ident$_2$}} - - This is the most general form of {\tt generalize} that combines the - previous behaviors. - -\item {\tt generalize dependent \term} \tacindex{generalize dependent} - - This generalizes {\term} but also {\em all} hypotheses which depend - on {\term}. It clears the generalized hypotheses. + These tactics behave as previously but naming the introduced hypothesis + \ident$_1$. It is equivalent to {\tt intro \ident$_1$} followed by + the appropriate call to {\tt move}~(see Section~\ref{move}). \end{Variants} +\subsection{\tt intros {\intropattern} {\ldots} {\intropattern}} +\label{intros-pattern} +\tacindex{intros \intropattern} +\index{Introduction patterns} +\index{Naming introduction patterns} +\index{Disjunctive/conjunctive introduction patterns} -\subsection{\tt revert \ident$_1$ \mbox{\dots} \ident$_n$ -\tacindex{revert} -\label{revert}} +This extension of the tactic {\tt intros} combines introduction of +variables or hypotheses and case analysis. An {\em introduction pattern} is +either: +\begin{itemize} +\item a {\em naming introduction pattern}, i.e. either one of: + \begin{itemize} + \item the pattern \texttt{?} + \item the pattern \texttt{?\ident} + \item an identifier + \end{itemize} +\item a {\em disjunctive/conjunctive introduction pattern}, i.e. either one of: + \begin{itemize} + \item a disjunction of lists of patterns: + {\tt [$p_{11}$ \dots\ $p_{1m_1}$ | \dots\ | $p_{11}$ \dots\ $p_{nm_n}$]} + \item a conjunction of patterns: {\tt ($p_1$ , \dots\ , $p_n$)} + \item a list of patterns {\tt ($p_1$ \&\ \dots\ \&\ $p_n$)} + for sequence of right-associative binary constructs + \end{itemize} +\item the wildcard: {\tt \_} +\item the rewriting orientations: {\tt ->} or {\tt <-} +\end{itemize} -This applies to any goal with variables \ident$_1$ \mbox{\dots} \ident$_n$. -It moves the hypotheses (possibly defined) to the goal, if this respects -dependencies. This tactic is the inverse of {\tt intro}. +Assuming a goal of type $Q \to P$ (non-dependent product), or +of type $\forall x:T,~P$ (dependent product), the behavior of +{\tt intros $p$} is defined inductively over the structure of the +introduction pattern~$p$: +\begin{itemize} +\item introduction on \texttt{?} performs the introduction, and lets {\Coq} + choose a fresh name for the variable; +\item introduction on \texttt{?\ident} performs the introduction, and + lets {\Coq} choose a fresh name for the variable based on {\ident}; +\item introduction on \texttt{\ident} behaves as described in + Section~\ref{intro}; +\item introduction over a disjunction of list of patterns {\tt + [$p_{11}$ \dots\ $p_{1m_1}$ | \dots\ | $p_{11}$ \dots\ $p_{nm_n}$]} + expects the product to be over an inductive type + whose number of constructors is $n$ (or more generally over a type + of conclusion an inductive type built from $n$ constructors, + e.g. {\tt C -> A\textbackslash/B if $n=2$}): it destructs the introduced + hypothesis as {\tt destruct} (see Section~\ref{destruct}) would and + applies on each generated subgoal the corresponding tactic; + \texttt{intros}~$p_{i1}$ {\ldots} $p_{im_i}$; if the disjunctive + pattern is part of a sequence of patterns and is not the last + pattern of the sequence, then {\Coq} completes the pattern so that all + the argument of the constructors of the inductive type are + introduced (for instance, the list of patterns {\tt [$\;$|$\;$] H} + applied on goal {\tt forall x:nat, x=0 -> 0=x} behaves the same as + the list of patterns {\tt [$\,$|$\,$?$\,$] H}); +\item introduction over a conjunction of patterns {\tt ($p_1$, \ldots, + $p_n$)} expects the goal to be a product over an inductive type $I$ with a + single constructor that itself has at least $n$ arguments: it + performs a case analysis over the hypothesis, as {\tt destruct} + would, and applies the patterns $p_1$~\ldots~$p_n$ to the arguments + of the constructor of $I$ (observe that {\tt ($p_1$, {\ldots}, + $p_n$)} is an alternative notation for {\tt [$p_1$ {\ldots} + $p_n$]}); +\item introduction via {\tt ($p_1$ \& \dots\ \& $p_n$)} + is a shortcut for introduction via + {\tt ($p_1$,(\ldots,(\dots,$p_n$)\ldots))}; it expects the + hypothesis to be a sequence of right-associative binary inductive + constructors such as {\tt conj} or {\tt ex\_intro}; for instance, an + hypothesis with type {\tt A\verb|/\|exists x, B\verb|/\|C\verb|/\|D} can be + introduced via pattern {\tt (a \& x \& b \& c \& d)}; +\item introduction on the wildcard depends on whether the product is + dependent or not: in the non-dependent case, it erases the + corresponding hypothesis (i.e. it behaves as an {\tt intro} followed + by a {\tt clear}, cf Section~\ref{clear}) while in the dependent + case, it succeeds and erases the variable only if the wildcard is + part of a more complex list of introduction patterns that also + erases the hypotheses depending on this variable; +\item introduction over {\tt ->} (respectively {\tt <-}) expects the + hypothesis to be an equality and the right-hand-side (respectively + the left-hand-side) is replaced by the left-hand-side (respectively + the right-hand-side) in both the conclusion and the context of the goal; + if moreover the term to substitute is a variable, the hypothesis is + removed. +\end{itemize} -\begin{ErrMsgs} -\item \errindexbis{{\ident} is used in the hypothesis {\ident'}}{is - used in the hypothesis} -\end{ErrMsgs} +\Example -\begin{Variants} -\item {\tt revert dependent \ident \tacindex{revert dependent}} +\begin{coq_example} +Goal forall A B C:Prop, A \/ B /\ C -> (A -> C) -> C. +intros A B C [a| [_ c]] f. +apply (f a). +exact c. +Qed. +\end{coq_example} - This moves to the goal the hypothesis \ident\ and all hypotheses - which depend on it. +\Rem {\tt intros $p_1~\ldots~p_n$} is not equivalent to \texttt{intros + $p_1$;\ldots; intros $p_n$} for the following reasons: +\begin{itemize} +\item A wildcard pattern never succeeds when applied isolated on a + dependent product, while it succeeds as part of a list of + introduction patterns if the hypotheses that depends on it are + erased too. +\item A disjunctive or conjunctive pattern followed by an introduction + pattern forces the introduction in the context of all arguments of + the constructors before applying the next pattern while a terminal + disjunctive or conjunctive pattern does not. Here is an example -\end{Variants} +\begin{coq_example} +Goal forall n:nat, n = 0 -> n = 0. +intros [ | ] H. +Show 2. +Undo. +intros [ | ]; intros H. +Show 2. +\end{coq_example} -\subsection{\tt change \term -\tacindex{change} -\label{change}} +\end{itemize} -This tactic applies to any goal. It implements the rule -``Conv''\index{Typing rules!Conv} given in Section~\ref{Conv}. {\tt - change U} replaces the current goal \T\ with \U\ providing that -\U\ is well-formed and that \T\ and \U\ are convertible. +\subsection{\tt clear \ident} +\tacindex{clear} +\label{clear} + +This tactic erases the hypothesis named {\ident} in the local context +of the current goal. As a consequence, {\ident} is no more displayed and no more +usable in the proof development. \begin{ErrMsgs} -\item \errindex{Not convertible} +\item \errindex{No such hypothesis} +\item \errindexbis{{\ident} is used in the conclusion}{is used in the + conclusion} +\item \errindexbis{{\ident} is used in the hypothesis {\ident'}}{is + used in the hypothesis} \end{ErrMsgs} -\tacindex{change \mbox{\dots} in} \begin{Variants} -\item {\tt change \term$_1$ with \term$_2$} - - This replaces the occurrences of \term$_1$ by \term$_2$ in the - current goal. The terms \term$_1$ and \term$_2$ must be - convertible. - -\item {\tt change \term$_1$ at \num$_1$ \mbox{\dots} \num$_i$ with \term$_2$} - - This replaces the occurrences numbered \num$_1$ \mbox{\dots} \num$_i$ of - \term$_1$ by \term$_2$ in the current goal. - The terms \term$_1$ and \term$_2$ must be convertible. - \ErrMsg {\tt Too few occurrences} +\item {\tt clear {\ident$_1$} \dots\ {\ident$_n$}} -\item {\tt change {\term} in {\ident}} + This is equivalent to {\tt clear {\ident$_1$}. {\ldots} clear + {\ident$_n$}.} -\item {\tt change \term$_1$ with \term$_2$ in {\ident}} - -\item {\tt change \term$_1$ at \num$_1$ \mbox{\dots} \num$_i$ with \term$_2$ in - {\ident}} - - This applies the {\tt change} tactic not to the goal but to the - hypothesis {\ident}. +\item {\tt clearbody {\ident}}\tacindex{clearbody} -\end{Variants} + This tactic expects {\ident} to be a local definition then clears + its body. Otherwise said, this tactic turns a definition into an + assumption. -\SeeAlso \ref{Conversion-tactics} + \ErrMsg \errindexbis{{\ident} is not a local definition}{is not a local definition} -\subsection{\tt fix {\ident} {\num} -\tacindex{fix} -\label{tactic:fix}} +\item \texttt{clear - {\ident$_1$} \dots\ {\ident$_n$}} -This tactic is a primitive tactic to start a proof by induction. In -general, it is easier to rely on higher-level induction tactics such -as the ones described in Section~\ref{Tac-induction}. + This tactic clears all the hypotheses except the ones depending in + the hypotheses named {\ident$_1$} {\ldots} {\ident$_n$} and in the + goal. -In the syntax of the tactic, the identifier {\ident} is the name given -to the induction hypothesis. The natural number {\num} tells on which -premise of the current goal the induction acts, starting -from 1 and counting both dependent and non dependent -products. Especially, the current lemma must be composed of at least -{\num} products. +\item \texttt{clear} -Like in a {\tt fix} expression, the induction -hypotheses have to be used on structurally smaller arguments. -The verification that inductive 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 {\tt - Guarded} (see Section~\ref{Guarded}). + This tactic clears all the hypotheses except the ones the goal depends on. -\begin{Variants} - \item {\tt fix} {\ident}$_1$ {\num} {\tt with (} {\ident}$_2$ - \nelist{{\binder}$_{2}$}{} \zeroone{{\tt \{ struct {\ident$'_2$} - \}}} {\tt :} {\type}$_2$ {\tt )} {\ldots} {\tt (} {\ident}$_1$ - \nelist{{\binder}$_n$}{} \zeroone{{\tt \{ struct {\ident$'_n$} \}}} - {\tt :} {\type}$_n$ {\tt )} +\item {\tt clear dependent \ident \tacindex{clear dependent}} -This starts a proof by mutual induction. The statements to be -simultaneously proved are respectively {\tt forall} - \nelist{{\binder}$_2$}{}{\tt ,} {\type}$_2$, {\ldots}, {\tt forall} - \nelist{{\binder}$_n$}{}{\tt ,} {\type}$_n$. The identifiers -{\ident}$_1$ {\ldots} {\ident}$_n$ are the names of the induction -hypotheses. The identifiers {\ident}$'_2$ {\ldots} {\ident}$'_n$ are the -respective names of the premises on which the induction is performed -in the statements to be simultaneously proved (if not given, the -system tries to guess itself what they are). + This clears the hypothesis \ident\ and all the hypotheses + that depend on it. \end{Variants} -\subsection{\tt cofix {\ident} -\tacindex{cofix} -\label{tactic:cofix}} +\subsection{\tt revert \ident$_1$ \dots\ \ident$_n$} +\tacindex{revert} +\label{revert} -This tactic starts a proof by coinduction. The identifier {\ident} is -the name given to the coinduction hypothesis. Like in a {\tt cofix} -expression, the use of induction hypotheses have to guarded by a -constructor. The verification that the use of co-inductive hypotheses -is correct is 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 {\tt Guarded} (see Section~\ref{Guarded}). +This applies to any goal with variables \ident$_1$ \dots\ \ident$_n$. +It moves the hypotheses (possibly defined) to the goal, if this respects +dependencies. This tactic is the inverse of {\tt intro}. +\begin{ErrMsgs} +\item \errindex{No such hypothesis} +\item \errindexbis{{\ident} is used in the hypothesis {\ident'}}{is + used in the hypothesis} +\end{ErrMsgs} \begin{Variants} - \item {\tt cofix} {\ident}$_1$ {\tt with (} {\ident}$_2$ - \nelist{{\binder}$_2$}{} {\tt :} {\type}$_2$ {\tt )} {\ldots} {\tt - (} {\ident}$_1$ \nelist{{\binder}$_1$}{} {\tt :} {\type}$_n$ - {\tt )} +\item {\tt revert dependent \ident \tacindex{revert dependent}} -This starts a proof by mutual coinduction. The statements to be -simultaneously proved are respectively {\tt forall} -\nelist{{\binder}$_2$}{}{\tt ,} {\type}$_2$, {\ldots}, {\tt forall} - \nelist{{\binder}$_n$}{}{\tt ,} {\type}$_n$. The identifiers - {\ident}$_1$ {\ldots} {\ident}$_n$ are the names of the - coinduction hypotheses. + This moves to the goal the hypothesis \ident\ and all hypotheses + which depend on it. \end{Variants} -\subsection{\tt evar (\ident:\term) -\tacindex{evar} -\label{evar}} +\subsection{\tt move {\ident$_1$} after {\ident$_2$}} +\tacindex{move} +\label{move} -The {\tt evar} tactic creates a new local definition named \ident\ with -type \term\ in the context. The body of this binding is a fresh -existential variable. +This moves the hypothesis named {\ident$_1$} in the local context +after the hypothesis named {\ident$_2$}. The proof term is not changed. -\subsection{\tt instantiate (\num:= \term) -\tacindex{instantiate} -\label{instantiate}} +If {\ident$_1$} comes before {\ident$_2$} in the order of dependences, +then all hypotheses between {\ident$_1$} and {\ident$_2$} that +(possibly indirectly) depend on {\ident$_1$} are moved also. -The {\tt instantiate} tactic allows to refine (see Section~\ref{refine}) -an existential variable -with the term \term. The \num\ argument is the position of the -existential variable from right to left in the conclusion. This cannot be -the number of the existential variable since this number is different -in every session. +If {\ident$_1$} comes after {\ident$_2$} in the order of dependences, +then all hypotheses between {\ident$_1$} and {\ident$_2$} that +(possibly indirectly) occur in {\ident$_1$} are moved also. \begin{Variants} - \item {\tt instantiate (\num:=\term) in \ident} - - \item {\tt instantiate (\num:=\term) in (Value of \ident)} - - \item {\tt instantiate (\num:=\term) in (Type of \ident)} -These allow to refer respectively to existential variables occurring in -a hypothesis or in the body or the type of a local definition. +\item {\tt move {\ident$_1$} before {\ident$_2$}} - \item {\tt instantiate} +This moves {\ident$_1$} towards and just before the hypothesis named {\ident$_2$}. - Without argument, the {\tt instantiate} tactic tries to solve as - many existential variables as possible, using information gathered - from other tactics in the same tactical. This is automatically - done after each complete tactic (i.e. after a dot in proof mode), - but not, for example, between each tactic when they are sequenced - by semicolons. +\item {\tt move {\ident} at top} -\end{Variants} +This moves {\ident} at the top of the local context (at the beginning of the context). -\subsection{\tt admit -\tacindex{admit} -\label{admit}} +\item {\tt move {\ident} at bottom} -The {\tt admit} tactic ``solves'' the current subgoal by an -axiom. This typically allows to temporarily skip a subgoal so as to -progress further in the rest of the proof. To know if some proof still -relies on unproved subgoals, one can use the command {\tt Print -Assumptions} (see Section~\ref{PrintAssumptions}). Admitted subgoals -have names of the form {\ident}\texttt{\_admitted} possibly followed -by a number. +This moves {\ident} at the bottom of the local context (at the end of the context). -\subsection{\tt constr\_eq \term$_1$ \term$_2$ -\tacindex{constr\_eq} -\label{constreq}} +\end{Variants} -This tactic applies to any goal. It checks whether its arguments are -equal modulo alpha conversion and casts. +\begin{ErrMsgs} -\ErrMsg \errindex{Not equal} +\item \errindex{No such hypothesis} -\subsection{\tt unify \term$_1$ \term$_2$ -\tacindex{unify} -\label{unify}} +\item \errindex{Cannot move {\ident$_1$} after {\ident$_2$}: + it occurs in {\ident$_2$}} -This tactic applies to any goal. It checks whether its arguments are -unifiable, potentially instantiating existential variables. +\item \errindex{Cannot move {\ident$_1$} after {\ident$_2$}: + it depends on {\ident$_2$}} -\ErrMsg \errindex{Not unifiable} +\end{ErrMsgs} + +\subsection{\tt rename {\ident$_1$} into {\ident$_2$}} +\tacindex{rename} + +This renames hypothesis {\ident$_1$} into {\ident$_2$} in the current +context. The name of the hypothesis in the proof-term, however, is left +unchanged. \begin{Variants} -\item {\tt unify \term$_1$ \term$_2$ with \ident} - Unification takes the transparency information defined in the - hint database {\tt \ident} into account (see Section~\ref{HintTransparency}). +\item {\tt rename {\ident$_1$} into {\ident$_2$}, \ldots, + {\ident$_{2k-1}$} into {\ident$_{2k}$}} + +This is equivalent to the sequence of the corresponding atomic {\tt rename}. + \end{Variants} -\subsection{\tt is\_evar \term -\tacindex{is\_evar} -\label{isevar}} +\begin{ErrMsgs} +\item \errindex{No such hypothesis} +\item \errindexbis{{\ident$_2$} is already used}{is already used} +\end{ErrMsgs} -This tactic applies to any goal. It checks whether its argument is an -existential variable. Existential variables are uninstantiated -variables generated by e.g. {\tt eapply} (see Section~\ref{apply}). +\subsection{\tt set ( {\ident} := {\term} )} +\label{tactic:set} +\tacindex{set} -\ErrMsg \errindex{Not an evar} +This replaces {\term} by {\ident} in the conclusion of the current goal +and adds the new definition {\tt {\ident} := \term} to the local context. -\subsection{\tt has\_evar \term -\tacindex{has\_evar} -\label{hasevar}} +If {\term} has holes (i.e. subexpressions of the form ``\_''), the +tactic first checks that all subterms matching the pattern are +compatible before doing the replacement using the leftmost subterm +matching the pattern. -This tactic applies to any goal. It checks whether its argument has an -existential variable as a subterm. Unlike {\tt context} patterns -combined with {\tt is\_evar}, this tactic scans all subterms, -including those under binders. +\begin{ErrMsgs} +\item \errindex{The variable {\ident} is already defined} +\end{ErrMsgs} -\ErrMsg \errindex{No evars} +\begin{Variants} -\subsection{\tt is\_var \term -\tacindex{is\_var} -\label{isvar}} +\item {\tt set ( {\ident} := {\term} ) in {\occgoalset}} -This tactic applies to any goal. It checks whether its argument is a -variable or hypothesis in the current goal context or in the opened sections. +This notation allows to specify which occurrences of {\term} have to +be substituted in the context. The {\tt in {\occgoalset}} clause is an +occurrence clause whose syntax and behavior are described in +Section~\ref{Occurrences clauses}. -\ErrMsg \errindex{Not a variable or hypothesis} +\item {\tt set ( {\ident} \nelist{\binder}{} := {\term} )} -\subsection{Bindings list -\index{Binding list} -\label{Binding-list}} + This is equivalent to {\tt set ( {\ident} := fun + \nelist{\binder}{} => {\term} )}. -Tactics that take a term as argument may also support a bindings list, so -as to instantiate some parameters of the term by name or position. -The general form of a term equipped with a bindings list is {\tt -{\term} with {\bindinglist}} where {\bindinglist} may be of two -different forms: +\item {\tt set \term} -\begin{itemize} -\item In a bindings list of the form {\tt (\vref$_1$ := \term$_1$) - \mbox{\dots} (\vref$_n$ := \term$_n$)}, {\vref} is either an {\ident} or a - {\num}. The references are determined according to the type of - {\term}. If \vref$_i$ is an identifier, this identifier has to be - bound in the type of {\term} and the binding provides the tactic - with an instance for the parameter of this name. If \vref$_i$ is - some number $n$, this number denotes the $n$-th non dependent - premise of the {\term}, as determined by the type of {\term}. + This behaves as {\tt set (} {\ident} := {\term} {\tt )} but {\ident} + is generated by {\Coq}. This variant also supports an occurrence clause. - \ErrMsg \errindex{No such binder} +\item {\tt set ( {\ident$_0$} \nelist{\binder}{} := {\term} ) in {\occgoalset}}\\ + {\tt set {\term} in {\occgoalset}} -\item A bindings list can also be a simple list of terms {\tt - \term$_1$ \dots\term$_n$}. In that case the references to - which these terms correspond are determined by the tactic. In case - of {\tt induction}, {\tt destruct}, {\tt elim} and {\tt case} (see - Section~\ref{elim}) the terms have to provide instances for all the - dependent products in the type of \term\ while in the case of {\tt - apply}, or of {\tt constructor} and its variants, only instances for - the dependent products which are not bound in the conclusion of the - type are required. + These are the general forms which combine the previous possibilities. - \ErrMsg \errindex{Not the right number of missing arguments} -\end{itemize} +\item {\tt remember {\term} as {\ident}}\tacindex{remember} -\subsection{Occurrences sets and occurrences clauses} -\label{Occurrences clauses} -\index{Occurrences clauses} + This behaves as {\tt set ( {\ident} := {\term} ) in *} and using a + logical (Leibniz's) equality instead of a local definition. -An occurrences clause is a modifier to some tactics that obeys the -following syntax: +\item {\tt remember {\term} as {\ident} eqn:{\ident}} -$\!\!\!$\begin{tabular}{lcl} -{\occclause} & ::= & {\tt in} {\occgoalset} \\ -{\occgoalset} & ::= & - \zeroone{{\ident$_1$} \zeroone{\atoccurrences} {\tt ,} \\ -& & {\dots} {\tt ,}\\ -& & {\ident$_m$} \zeroone{\atoccurrences}}\\ -& & \zeroone{{\tt |-} \zeroone{{\tt *} \zeroone{\atoccurrences}}}\\ -& | & - {\tt *} {\tt |-} \zeroone{{\tt *} \zeroone{\atoccurrences}}\\ -& | & - {\tt *}\\ -{\atoccurrences} & ::= & {\tt at} {\occlist}\\ -{\occlist} & ::= & \zeroone{{\tt -}} {\num$_1$} \dots\ {\num$_n$} -\end{tabular} - -The role of an occurrence clause is to select a set of occurrences of -a {\term} in a goal. In the first case, the {{\ident$_i$} -\zeroone{{\tt at} {\num$_1^i$} \dots\ {\num$_{n_i}^i$}}} parts -indicate that occurrences have to be selected in the hypotheses named -{\ident$_i$}. If no numbers are given for hypothesis {\ident$_i$}, -then all 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 {\tt Set Printing All} (see -Section~\ref{SetPrintingAll}), counting from left to right. In -particular, occurrences of {\term} in implicit arguments (see -Section~\ref{Implicit Arguments}) or coercions (see -Section~\ref{Coercions}) are counted. + This behaves as {\tt remember {\term} as {\ident}}, except + that the name of the generated equality is also given. -If a minus sign is given between {\tt at} and the list of occurrences, -it negates the condition so that the clause denotes all the occurrences except -the ones explicitly mentioned after the minus sign. +\item {\tt remember {\term} as {\ident} in {\occgoalset}} -As an exception to the left-to-right order, the occurrences in the -{\tt return} subexpression of a {\tt match} are considered {\em -before} the occurrences in the matched term. + This is a more general form of {\tt remember} that remembers the + occurrences of {\term} specified by an occurrences set. -In the second case, the {\tt *} on the left of {\tt |-} means that -all occurrences of {\term} are selected in every hypothesis. +\item {\tt pose ( {\ident} := {\term} )}\tacindex{pose} -In the first and second case, if {\tt *} is mentioned on the right of -{\tt |-}, the occurrences of the conclusion of the goal have to be -selected. If some numbers are given, then only the occurrences denoted -by these numbers are selected. In no numbers are given, all -occurrences of {\term} in the goal are selected. + This adds the local definition {\ident} := {\term} to the current + context without performing any replacement in the goal or in the + hypotheses. It is equivalent to {\tt set ( {\ident} {\tt :=} + {\term} {\tt ) in |-}}. -Finally, the last notation is an abbreviation for {\tt * |- *}. Note -also that {\tt |-} is optional in the first case when no {\tt *} is -given. +\item {\tt pose ( {\ident} \nelist{\binder}{} := {\term} )} -Here are some tactics that understand occurrences clauses: -{\tt set}, {\tt remember}, {\tt induction}, {\tt destruct}. + This is equivalent to {\tt pose (} {\ident} {\tt :=} {\tt fun} + \nelist{\binder}{} {\tt =>} {\term} {\tt )}. -\SeeAlso~Sections~\ref{tactic:set}, \ref{Tac-induction}, \ref{SetPrintingAll}. +\item{\tt pose {\term}} + This behaves as {\tt pose ( {\ident} := {\term} )} but + {\ident} is generated by {\Coq}. -\section{Negation and contradiction} +\end{Variants} -\subsection{\tt absurd \term -\tacindex{absurd} -\label{absurd}} +\subsection{\tt decompose [ {\qualid$_1$} \dots\ {\qualid$_n$} ] \term} +\label{decompose} +\tacindex{decompose} -This tactic applies to any goal. The argument {\term} is any -proposition {\tt P} of type {\tt Prop}. This tactic applies {\tt - False} elimination, that is it deduces the current goal from {\tt - False}, and generates as subgoals {\tt $\sim$P} and {\tt P}. It is -very useful in proofs by cases, where some cases are impossible. In -most cases, \texttt{P} or $\sim$\texttt{P} is one of the hypotheses of -the local context. +This tactic allows to recursively decompose a +complex proposition in order to obtain atomic ones. -\subsection{\tt contradiction -\label{contradiction} -\tacindex{contradiction}} +\Example -This tactic applies to any goal. The {\tt contradiction} tactic -attempts to find in the current context (after all {\tt intros}) one -hypothesis which is equivalent to {\tt False}. It permits to prune -irrelevant cases. This tactic is a macro for the tactics sequence -{\tt intros; elimtype False; assumption}. +\begin{coq_eval} +Reset Initial. +\end{coq_eval} +\begin{coq_example} +Goal forall A B C:Prop, A /\ B /\ C \/ B /\ C \/ C /\ A -> C. +intros A B C H; decompose [and or] H; assumption. +\end{coq_example} +\begin{coq_example*} +Qed. +\end{coq_example*} -\begin{ErrMsgs} -\item \errindex{No such assumption} -\end{ErrMsgs} +{\tt decompose} does not work on right-hand sides of implications or products. \begin{Variants} -\item {\tt contradiction \ident} -The proof of {\tt False} is searched in the hypothesis named \ident. -\end{Variants} +\item {\tt decompose sum \term}\tacindex{decompose sum} -\subsection {\tt contradict \ident} -\label{contradict} -\tacindex{contradict} + This decomposes sum types (like \texttt{or}). -This tactic allows to manipulate negated hypothesis and goals. The -name \ident\ should correspond to a hypothesis. With -{\tt contradict H}, the current goal and context is transformed in -the following way: -\begin{itemize} -\item {\tt H:$\neg$A $\vd$ B} \ becomes \ {\tt $\vd$ A} -\item {\tt H:$\neg$A $\vd$ $\neg$B} \ becomes \ {\tt H: B $\vd$ A } -\item {\tt H: A $\vd$ B} \ becomes \ {\tt $\vd$ $\neg$A} -\item {\tt H: A $\vd$ $\neg$B} \ becomes \ {\tt H: B $\vd$ $\neg$A} -\end{itemize} +\item {\tt decompose record \term}\tacindex{decompose record} -\subsection{\tt exfalso} -\label{exfalso} -\tacindex{exfalso} + This decomposes record types (inductive types with one constructor, + like \texttt{and} and \texttt{exists} and those defined with the + \texttt{Record} macro, see Section~\ref{Record}). -This tactic implements the ``ex falso quodlibet'' logical principle: -an elimination of {\tt False} is performed on the current goal, and the -user is then required to prove that {\tt False} is indeed provable in -the current context. This tactic is a macro for {\tt elimtype False}. +\end{Variants} -\section{Conversion tactics -\index{Conversion tactics} -\label{Conversion-tactics}} +\section{Controlling the proof flow} -This set of tactics implements different specialized usages of the -tactic \texttt{change}. +\subsection{\tt assert ( {\ident} :\ {\form} )} +\tacindex{assert} -All conversion tactics (including \texttt{change}) can be -parameterized by the parts of the goal where the conversion can -occur. This is done using \emph{goal clauses} which consists in a list -of hypotheses and, optionally, of a reference to the conclusion of the -goal. For defined hypothesis it is possible to specify if the -conversion should occur on the type part, the body part or both -(default). +This tactic applies to any goal. {\tt assert (H : U)} adds a new +hypothesis of name \texttt{H} asserting \texttt{U} to the current goal +and opens a new subgoal \texttt{U}\footnote{This corresponds to the + cut rule of sequent calculus.}. The subgoal {\texttt U} comes first +in the list of subgoals remaining to prove. -\index{Clauses} -\index{Goal clauses} -Goal clauses are written after a conversion tactic (tactics -\texttt{set}~\ref{tactic:set}, \texttt{rewrite}~\ref{rewrite}, -\texttt{replace}~\ref{tactic:replace} and -\texttt{autorewrite}~\ref{tactic:autorewrite} also use goal clauses) and -are introduced by the keyword \texttt{in}. If no goal clause is provided, -the default is to perform the conversion only in the conclusion. +\begin{ErrMsgs} +\item \errindex{Not a proposition or a type} -The syntax of goal clauses for conversion is the following: -\begin{center} -\begin{tabular}{rcl} -{\hyplocation} & ::= & {\ident} $\mid$ {\tt (type of} {\ident}{\tt )} $\mid$ {\tt (value of} {\ident}{\tt )}\\ -{\convclause} & ::= & \texttt{in} \sequence{\hyplocation}{,} {\tt |- \zeroone{*}}\\ -& $\mid$ & \texttt{in * |- \zeroone{*}}\\ -& $\mid$ & \texttt{in *}\\ - \end{tabular} -\end{center} - -If {\ident} refers to a local definition, then {\tt (type of} -{\ident}{\tt )} refers to the type part of it only and {\tt (value of} -{\ident}{\tt )} refers to the value part of it. If {\tt *} is given -on the right of {\tt |-}, then the conclusion is concerned -too. Otherwise, only the listed names of hypotheses are concerned. If -{\tt *} appears on the left of {\tt |-}, then all hypotheses are -concerned. Finally, the expression {\tt in *} is an short-hand for -\texttt{in * |- *}. - -For backward compatibility, the notation \texttt{in}~{\ident}$_1$ {\tt - ,} {\ldots} {\tt ,} {\ident}$_n$ performs the conversion in -hypotheses {\ident}$_1$ {\ldots} {\ident}$_n$. + Arises when the argument {\form} is neither of type {\tt Prop}, {\tt + Set} nor {\tt Type}. -%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -%voir reduction__conv_x : histoires d'univers. -%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +\end{ErrMsgs} -\subsection[{\tt cbv} \flag$_1$ \mbox{\ldots} \flag$_n$, {\tt lazy} \flag$_1$ -\mbox{\ldots} \flag$_n$ and {\tt compute}] -{{\tt cbv} \flag$_1$ {\ldots} \flag$_n$, {\tt lazy} \flag$_1$ -{\ldots} \flag$_n$ and {\tt compute} -\tacindex{cbv} -\tacindex{lazy} -\tacindex{compute} -\tacindex{vm\_compute}\label{vmcompute}} +\begin{Variants} -These parameterized reduction tactics apply to any goal and perform -the normalization of the goal according to the specified flags. In -correspondence with the kinds of reduction considered in \Coq\, namely -$\beta$ (reduction of functional application), $\delta$ (unfolding of -transparent constants, see \ref{Transparent}), $\iota$ (reduction of -pattern-matching over a constructed term, and unfolding of {\tt fix} -and {\tt cofix} expressions) and $\zeta$ (contraction of local -definitions), the flag are either {\tt beta}, {\tt delta}, {\tt iota} -or {\tt zeta}. The {\tt delta} flag itself can be refined into {\tt -delta [}{\qualid$_1$} {\ldots} {\qualid$_k$}{\tt ]} or {\tt delta --[}{\qualid$_1$} {\ldots} {\qualid$_k$}{\tt ]}, restricting in the first case the -constants to unfold to the constants listed, and restricting in the -second case the constant to unfold to all but the ones explicitly -mentioned. Notice that the {\tt delta} flag does not apply to -variables bound by a let-in construction inside the term itself (use -here the {\tt zeta} flag). In any cases, opaque constants are not -unfolded (see Section~\ref{Opaque}). +\item{\tt assert {\form}} -The goal may be normalized with two strategies: {\em lazy} ({\tt lazy} -tactic), or {\em call-by-value} ({\tt cbv} tactic). The lazy strategy -is a call-by-need strategy, with sharing of reductions: the arguments of a -function call are partially evaluated only when necessary, and if an -argument is used several times then it is computed only once. This -reduction is efficient for reducing expressions with dead code. For -instance, the proofs of a proposition {\tt exists~$x$. $P(x)$} reduce to a -pair of a witness $t$, and a proof that $t$ satisfies the predicate -$P$. Most of the time, $t$ may be computed without computing the proof -of $P(t)$, thanks to the lazy strategy. + This behaves as {\tt assert ( {\ident} :\ {\form} )} but + {\ident} is generated by {\Coq}. -The call-by-value strategy is the one used in ML languages: the -arguments of a function call are evaluated first, using a weak -reduction (no reduction under the $\lambda$-abstractions). Despite the -lazy strategy always performs fewer reductions than the call-by-value -strategy, the latter is generally more efficient for evaluating purely -computational expressions (i.e. with few dead code). +\item{\tt assert ( {\ident} := {\term} )} -\begin{Variants} -\item {\tt compute} \tacindex{compute}\\ - {\tt cbv} - - These are synonyms for {\tt cbv beta delta iota zeta}. + This behaves as {\tt assert ({\ident} :\ {\type});[exact + {\term}|idtac]} where {\type} is the type of {\term}. -\item {\tt lazy} - - This is a synonym for {\tt lazy beta delta iota zeta}. + \ErrMsg \errindex{Variable {\ident} is already declared} -\item {\tt compute [}{\qualid$_1$} {\ldots} {\qualid$_k$}{\tt ]}\\ - {\tt cbv [}{\qualid$_1$} {\ldots} {\qualid$_k$}{\tt ]} +\item {\tt cut {\form}}\tacindex{cut} - These are synonyms of {\tt cbv beta delta - [}{\qualid$_1$} {\ldots} {\qualid$_k$}{\tt ] iota zeta}. - -\item {\tt compute -[}{\qualid$_1$} {\ldots} {\qualid$_k$}{\tt ]}\\ - {\tt cbv -[}{\qualid$_1$} {\ldots} {\qualid$_k$}{\tt ]} + This tactic applies to any goal. It implements the non-dependent + case of the ``App''\index{Typing rules!App} rule given in + Section~\ref{Typed-terms}. (This is Modus Ponens inference rule.) + {\tt cut U} transforms the current goal \texttt{T} into the two + following subgoals: {\tt U -> T} and \texttt{U}. The subgoal {\tt U + -> T} comes first in the list of remaining subgoal to prove. - These are synonyms of {\tt cbv beta delta - -[}{\qualid$_1$} {\ldots} {\qualid$_k$}{\tt ] iota zeta}. +\item \texttt{assert {\form} by {\tac}}\tacindex{assert by} -\item {\tt lazy [}{\qualid$_1$} {\ldots} {\qualid$_k$}{\tt ]}\\ - {\tt lazy -[}{\qualid$_1$} {\ldots} {\qualid$_k$}{\tt ]} + This tactic behaves like \texttt{assert} but applies {\tac} + to solve the subgoals generated by \texttt{assert}. - These are respectively synonyms of {\tt lazy beta delta - [}{\qualid$_1$} {\ldots} {\qualid$_k$}{\tt ] iota zeta} and {\tt lazy beta delta - -[}{\qualid$_1$} {\ldots} {\qualid$_k$}{\tt ] iota zeta}. + \ErrMsg \errindex{Proof is not complete} -\item {\tt vm\_compute} \tacindex{vm\_compute} +\item \texttt{assert {\form} as {\intropattern}\tacindex{assert as}} - This tactic evaluates the goal using the optimized call-by-value - evaluation bytecode-based virtual machine. This algorithm is - dramatically more efficient than the algorithm used for the {\tt - cbv} tactic, but it cannot be fine-tuned. It is specially - interesting for full evaluation of algebraic objects. This includes - the case of reflexion-based tactics. + If {\intropattern} is a naming introduction pattern (see + Section~\ref{intros-pattern}), the hypothesis is named after this + introduction pattern (in particular, if {\intropattern} is {\ident}, + the tactic behaves like \texttt{assert ({\ident} :\ {\form})}). -\end{Variants} + If {\intropattern} is a disjunctive/conjunctive introduction + pattern, the tactic behaves like \texttt{assert {\form}} then destructing the + resulting hypothesis using the given introduction pattern. -% Obsolete? Anyway not very important message -%\begin{ErrMsgs} -%\item \errindex{Delta must be specified before} -% -% A list of constants appeared before the {\tt delta} flag. -%\end{ErrMsgs} +\item \texttt{assert {\form} as {\intropattern} by {\tac}} + This combines the two previous variants of {\tt assert}. -\subsection{{\tt red} -\tacindex{red}} +\item \texttt{pose proof {\term} as {\intropattern}\tacindex{pose proof}} -This tactic applies to a goal which has the form {\tt - forall (x:T1)} {\ldots} {\tt (xk:Tk), c t1} {\ldots} {\tt tn} where {\tt c} is a constant. If -{\tt c} is transparent then it replaces {\tt c} with its definition -(say {\tt t}) and then reduces {\tt (t t1} {\ldots} {\tt tn)} according to -$\beta\iota\zeta$-reduction rules. + This tactic behaves like \texttt{assert T as {\intropattern} by + exact {\term}} where \texttt{T} is the type of {\term}. -\begin{ErrMsgs} -\item \errindex{Not reducible} -\end{ErrMsgs} + In particular, \texttt{pose proof {\term} as {\ident}} behaves as + \texttt{assert ({\ident} := {\term})} and \texttt{pose proof {\term} as + {\disjconjintropattern}\tacindex{pose proof}} behaves + like \texttt{destruct {\term} as {\disjconjintropattern}}. -\subsection{{\tt hnf} -\tacindex{hnf}} +\item {\tt specialize ({\ident} \term$_1$ \dots\ \term$_n$)\tacindex{specialize}} \\ + {\tt specialize {\ident} with \bindinglist} -This tactic applies to any goal. It replaces the current goal with its -head normal form according to the $\beta\delta\iota\zeta$-reduction -rules, i.e. it reduces the head of the goal until it becomes a -product or an irreducible term. + The tactic {\tt specialize} works on local hypothesis \ident. + The premises of this hypothesis (either universal + quantifications or non-dependent implications) are instantiated + by concrete terms coming either from arguments \term$_1$ + $\ldots$ \term$_n$ or from a bindings list (see + Section~\ref{Binding-list} for more about bindings lists). In the + second form, all instantiation elements must be given, whereas + in the first form the application to \term$_1$ {\ldots} + \term$_n$ can be partial. The first form is equivalent to + {\tt assert (\ident' := {\ident} {\term$_1$} \dots\ \term$_n$); + clear \ident; rename \ident' into \ident}. -\Example -The term \verb+forall n:nat, (plus (S n) (S n))+ is not reduced by {\tt hnf}. + The name {\ident} can also refer to a global lemma or + hypothesis. In this case, for compatibility reasons, the + behavior of {\tt specialize} is close to that of {\tt + generalize}: the instantiated statement becomes an additional + premise of the goal. -\Rem The $\delta$ rule only applies to transparent constants -(see Section~\ref{Opaque} on transparency and opacity). - -\subsection{\tt simpl -\tacindex{simpl}} - -This tactic applies to any goal. The tactic {\tt simpl} first applies -$\beta\iota$-reduction rule. Then it expands transparent constants -and tries to reduce {\tt T'} according, once more, to $\beta\iota$ -rules. But when the $\iota$ rule is not applicable then possible -$\delta$-reductions are not applied. For instance trying to use {\tt -simpl} on {\tt (plus n O)=n} changes nothing. Notice that only -transparent constants whose name can be reused as such in the -recursive calls are possibly unfolded. For instance a constant defined -by {\tt plus' := plus} is possibly unfolded and reused in the -recursive calls, but a constant such as {\tt succ := plus (S O)} is -never unfolded. - -The behavior of {\tt simpl} can be tuned using the {\tt Arguments} vernacular -command as follows: -\comindex{Arguments} -\begin{itemize} -\item -A constant can be marked to be never unfolded by {\tt simpl}: -\begin{coq_example*} -Arguments minus x y : simpl never -\end{coq_example*} -After that command an expression like {\tt (minus (S x) y)} is left untouched by -the {\tt simpl} tactic. -\item -A constant can be marked to be unfolded only if applied to enough arguments. -The number of arguments required can be specified using -the {\tt /} symbol in the arguments list of the {\tt Arguments} vernacular -command. -\begin{coq_example*} -Definition fcomp A B C f (g : A -> B) (x : A) : C := f (g x). -Notation "f \o g" := (fcomp f g) (at level 50). -Arguments fcomp {A B C} f g x /. -\end{coq_example*} -After that command the expression {\tt (f \verb+\+o g)} is left untouched by -{\tt simpl} while {\tt ((f \verb+\+o g) t)} is reduced to {\tt (f (g t))}. -The same mechanism can be used to make a constant volatile, i.e. always -unfolded by {\tt simpl}. -\begin{coq_example*} -Definition volatile := fun x : nat => x. -Arguments volatile / x. -\end{coq_example*} -\item -A constant can be marked to be unfolded only if an entire set of arguments -evaluates to a constructor. The {\tt !} symbol can be used to mark such -arguments. -\begin{coq_example*} -Arguments minus !x !y. -\end{coq_example*} -After that command, the expression {\tt (minus (S x) y)} is left untouched by -{\tt simpl}, while {\tt (minus (S x) (S y))} is reduced to {\tt (minus x y)}. -\item -A special heuristic to determine if a constant has to be unfolded can be -activated with the following command: -\begin{coq_example*} -Arguments minus x y : simpl nomatch -\end{coq_example*} -The heuristic avoids to perform a simplification step that would -expose a {\tt match} construct in head position. For example the -expression {\tt (minus (S (S x)) (S y))} is simplified to -{\tt (minus (S x) y)} even if an extra simplification is possible. -\end{itemize} - -\tacindex{simpl \mbox{\dots} in} -\begin{Variants} -\item {\tt simpl {\term}} - - This applies {\tt simpl} only to the occurrences of {\term} in the - current goal. - -\item {\tt simpl {\term} at \num$_1$ \mbox{\dots} \num$_i$} - - This applies {\tt simpl} only to the \num$_1$, \dots, \num$_i$ - occurrences of {\term} in the current goal. + \begin{ErrMsgs} + \item \errindexbis{{\ident} is used in hypothesis \ident'}{is used in hypothesis} + \item \errindexbis{{\ident} is used in conclusion}{is used in conclusion} + \end{ErrMsgs} - \ErrMsg {\tt Too few occurrences} +%% Moreover, the old syntax allows the use of a number after {\tt specialize} +%% for controlling the number of premises to instantiate. Giving this +%% number should not be mandatory anymore (automatic detection of how +%% many premises can be eaten without leaving meta-variables). Hence +%% no documentation for this integer optional argument of specialize -\item {\tt simpl {\ident}} - - This applies {\tt simpl} only to the applicative subterms whose head - occurrence is {\ident}. +\end{Variants} -\item {\tt simpl {\ident} at \num$_1$ \mbox{\dots} \num$_i$} - - This applies {\tt simpl} only to the \num$_1$, \dots, \num$_i$ -applicative subterms whose head occurrence is {\ident}. +\subsection{\tt generalize \term} +\tacindex{generalize} +\label{generalize} -\end{Variants} +This tactic applies to any goal. It generalizes the conclusion with +respect to one of its subterms. -\subsection{\tt unfold \qualid -\tacindex{unfold} -\label{unfold}} +\Example -This tactic applies to any goal. The argument {\qualid} must denote a -defined transparent constant or local definition (see Sections~\ref{Basic-definitions} and~\ref{Transparent}). The tactic {\tt - unfold} applies the $\delta$ rule to each occurrence of the constant -to which {\qualid} refers in the current goal and then replaces it -with its $\beta\iota$-normal form. +\begin{coq_eval} +Goal forall x y:nat, (0 <= x + y + y). +intros. +\end{coq_eval} +\begin{coq_example} +Show. +generalize (x + y + y). +\end{coq_example} -\begin{ErrMsgs} -\item {\qualid} \errindex{does not denote an evaluable constant} +\begin{coq_eval} +Abort. +\end{coq_eval} -\end{ErrMsgs} +If the goal is $G$ and $t$ is a subterm of type $T$ in the goal, then +{\tt generalize} \textit{t} replaces the goal by {\tt forall (x:$T$), $G'$} +where $G'$ is obtained from $G$ by replacing all occurrences of $t$ by +{\tt x}. The name of the variable (here {\tt n}) is chosen based on $T$. \begin{Variants} -\item {\tt unfold {\qualid}$_1$, \dots, \qualid$_n$} - \tacindex{unfold \mbox{\dots} in} - - Replaces {\em simultaneously} {\qualid}$_1$, \dots, {\qualid}$_n$ - with their definitions and replaces the current goal with its - $\beta\iota$ normal form. +\item {\tt generalize {\term$_1$ , \dots\ , \term$_n$}} -\item {\tt unfold {\qualid}$_1$ at \num$_1^1$, \dots, \num$_i^1$, -\dots,\ \qualid$_n$ at \num$_1^n$ \mbox{\dots} \num$_j^n$} - - The lists \num$_1^1$, \dots, \num$_i^1$ and \num$_1^n$, \dots, - \num$_j^n$ specify the occurrences of {\qualid}$_1$, \dots, - \qualid$_n$ to be unfolded. Occurrences are located from left to - right. + This is equivalent to {\tt generalize \term$_n$; \dots\ ; generalize + \term$_1$}. Note that the sequence of \term$_i$'s are processed + from $n$ to $1$. - \ErrMsg {\tt bad occurrence number of {\qualid}$_i$} +\item {\tt generalize {\term} at {\num$_1$ \dots\ \num$_i$}} - \ErrMsg {\qualid}$_i$ {\tt does not occur} + This is equivalent to {\tt generalize \term} but it generalizes only over + the specified occurrences of {\term} (counting from left to right on the + expression printed using option {\tt Set Printing All}). -\item {\tt unfold {\qstring}} +\item {\tt generalize {\term} as {\ident}} - If {\qstring} denotes the discriminating symbol of a notation (e.g. {\tt - "+"}) or an expression defining a notation (e.g. \verb!"_ + _"!), and - this notation refers to an unfoldable constant, then the tactic - unfolds it. + This is equivalent to {\tt generalize \term} but it uses {\ident} to name the + generalized hypothesis. -\item {\tt unfold {\qstring}\%{\delimkey}} +\item {\tt generalize {\term$_1$} at {\num$_{11}$ \dots\ \num$_{1i_1}$} + as {\ident$_1$} + , {\ldots} , + {\term$_n$} at {\num$_{n1}$ \mbox{\dots} \num$_{ni_n}$} + as {\ident$_2$}} - This is variant of {\tt unfold {\qstring}} where {\qstring} gets its - interpretation from the scope bound to the delimiting key - {\delimkey} instead of its default interpretation (see - Section~\ref{scopechange}). + This is the most general form of {\tt generalize} that combines the + previous behaviors. -\item {\tt unfold \qualidorstring$_1$ at \num$_1^1$, \dots, \num$_i^1$, -\dots,\ \qualidorstring$_n$ at \num$_1^n$ \mbox{\dots} \num$_j^n$} +\item {\tt generalize dependent \term} \tacindex{generalize dependent} - This is the most general form, where {\qualidorstring} is either a - {\qualid} or a {\qstring} referring to a notation. + This generalizes {\term} but also {\em all} hypotheses that depend + on {\term}. It clears the generalized hypotheses. \end{Variants} -\subsection{{\tt fold} \term -\tacindex{fold}} - -This tactic applies to any goal. The term \term\ is reduced using the {\tt red} -tactic. Every occurrence of the resulting term in the goal is then -replaced by \term. - -\begin{Variants} -\item {\tt fold} \term$_1$ \dots\ \term$_n$ - - Equivalent to {\tt fold} \term$_1$ {\tt;} {\ldots} {\tt; fold} \term$_n$. -\end{Variants} +\subsection{\tt evar ( {\ident} :\ {\term} )} +\tacindex{evar} +\label{evar} -\subsection{{\tt pattern {\term}} -\tacindex{pattern} -\label{pattern}} +The {\tt evar} tactic creates a new local definition named \ident\ with +type \term\ in the context. The body of this binding is a fresh +existential variable. -This command applies to any goal. The argument {\term} must be a free -subterm of the current goal. The command {\tt pattern} performs -$\beta$-expansion (the inverse of $\bt$-reduction) of the current goal -(say \T) by -\begin{enumerate} -\item replacing all occurrences of {\term} in {\T} with a fresh variable -\item abstracting this variable -\item applying the abstracted goal to {\term} -\end{enumerate} +\subsection{\tt instantiate ( {\num} := {\term} )} +\tacindex{instantiate} +\label{instantiate} -For instance, if the current goal $T$ is expressible has $\phi(t)$ -where the notation captures all the instances of $t$ in $\phi(t)$, -then {\tt pattern $t$} transforms it into {\tt (fun x:$A$ => $\phi(${\tt -x}$)$) $t$}. This command can be used, for instance, when the tactic -{\tt apply} fails on matching. +The {\tt instantiate} tactic allows to refine (see Section~\ref{refine}) +an existential variable +with the term \term. The \num\ argument is the position of the +existential variable from right to left in the conclusion. This cannot be +the number of the existential variable since this number is different +in every session. \begin{Variants} -\item {\tt pattern {\term} at {\num$_1$} \mbox{\dots} {\num$_n$}} - - Only the occurrences {\num$_1$} \dots\ {\num$_n$} of {\term} are - considered for $\beta$-expansion. Occurrences are located from left - to right. - -\item {\tt pattern {\term} at - {\num$_1$} \mbox{\dots} {\num$_n$}} - - All occurrences except the occurrences of indexes {\num$_1$} \dots\ - {\num$_n$} of {\term} are considered for - $\beta$-expansion. Occurrences are located from left to right. - -\item {\tt pattern {\term$_1$}, \dots, {\term$_m$}} - - Starting from a goal $\phi(t_1 \mbox{\dots} t_m)$, the tactic - {\tt pattern $t_1$, \dots,\ $t_m$} generates the equivalent goal {\tt - (fun (x$_1$:$A_1$) \mbox{\dots} (x$_m$:$A_m$) => $\phi(${\tt x$_1$\dots\ - x$_m$}$)$) $t_1$ \mbox{\dots} $t_m$}.\\ If $t_i$ occurs in one of the - generated types $A_j$ these occurrences will also be considered and - possibly abstracted. - -\item {\tt pattern {\term$_1$} at {\num$_1^1$} \mbox{\dots} {\num$_{n_1}^1$}, \dots, - {\term$_m$} at {\num$_1^m$} \mbox{\dots} {\num$_{n_m}^m$}} - - This behaves as above but processing only the occurrences \num$_1^1$, - \dots, \num$_i^1$ of \term$_1$, \dots, \num$_1^m$, \dots, \num$_j^m$ - of \term$_m$ starting from \term$_m$. + \item {\tt instantiate ( {\num} := {\term} ) in \ident} -\item {\tt pattern} {\term$_1$} \zeroone{{\tt at \zeroone{-}} {\num$_1^1$} \dots\ {\num$_{n_1}^1$}} {\tt ,} \dots {\tt ,} - {\term$_m$} \zeroone{{\tt at \zeroone{-}} {\num$_1^m$} \dots\ {\num$_{n_m}^m$}} - - This is the most general syntax that combines the different variants. + \item {\tt instantiate ( {\num} := {\term} ) in ( Value of {\ident} )} -\end{Variants} + \item {\tt instantiate ( {\num} := {\term} ) in ( Type of {\ident} )} -\subsection{Conversion tactics applied to hypotheses} +These allow to refer respectively to existential variables occurring in +a hypothesis or in the body or the type of a local definition. -{\convtactic} {\tt in} \ident$_1$ \dots\ \ident$_n$ + \item {\tt instantiate} -Applies the conversion tactic {\convtactic} to the -hypotheses \ident$_1$, \ldots, \ident$_n$. The tactic {\convtactic} is -any of the conversion tactics listed in this section. + Without argument, the {\tt instantiate} tactic tries to solve as + many existential variables as possible, using information gathered + from other tactics in the same tactical. This is automatically + done after each complete tactic (i.e. after a dot in proof mode), + but not, for example, between each tactic when they are sequenced + by semicolons. -If \ident$_i$ is a local definition, then \ident$_i$ can be replaced -by (Type of \ident$_i$) to address not the body but the type of the -local definition. Example: {\tt unfold not in (Type of H1) (Type of H3).} +\end{Variants} -\begin{ErrMsgs} -\item \errindex{No such hypothesis} : {\ident}. -\end{ErrMsgs} +\subsection{\tt admit} +\tacindex{admit} +\label{admit} +The {\tt admit} tactic ``solves'' the current subgoal by an +axiom. This typically allows to temporarily skip a subgoal so as to +progress further in the rest of the proof. To know if some proof still +relies on unproved subgoals, one can use the command {\tt Print +Assumptions} (see Section~\ref{PrintAssumptions}). Admitted subgoals +have names of the form {\ident}\texttt{\_admitted} possibly followed +by a number. -\section{Introductions} +\subsection{\tt absurd \term} +\tacindex{absurd} +\label{absurd} -Introduction tactics address goals which are inductive constants. -They are used when one guesses that the goal can be obtained with one -of its constructors' type. +This tactic applies to any goal. The argument {\term} is any +proposition {\tt P} of type {\tt Prop}. This tactic applies {\tt + False} elimination, that is it deduces the current goal from {\tt + False}, and generates as subgoals {\tt $\sim$P} and {\tt P}. It is +very useful in proofs by cases, where some cases are impossible. In +most cases, \texttt{P} or $\sim$\texttt{P} is one of the hypotheses of +the local context. -\subsection{\tt constructor \num -\label{constructor} -\tacindex{constructor}} +\subsection{\tt contradiction} +\label{contradiction} +\tacindex{contradiction} -This tactic applies to a goal such that the head of its conclusion is -an inductive constant (say {\tt I}). The argument {\num} must be less -or equal to the numbers of constructor(s) of {\tt I}. Let {\tt ci} be -the {\tt i}-th constructor of {\tt I}, then {\tt constructor i} is -equivalent to {\tt intros; apply ci}. +This tactic applies to any goal. The {\tt contradiction} tactic +attempts to find in the current context (after all {\tt intros}) one +hypothesis that is equivalent to {\tt False}. It permits to prune +irrelevant cases. This tactic is a macro for the tactics sequence +{\tt intros; elimtype False; assumption}. \begin{ErrMsgs} -\item \errindex{Not an inductive product} -\item \errindex{Not enough constructors} +\item \errindex{No such assumption} \end{ErrMsgs} \begin{Variants} -\item \texttt{constructor} - - This tries \texttt{constructor 1} then \texttt{constructor 2}, - \dots\ , then \texttt{constructor} \textit{n} where \textit{n} if - the number of constructors of the head of the goal. +\item {\tt contradiction \ident} -\item {\tt constructor \num~with} {\bindinglist} - - Let {\tt ci} be the {\tt i}-th constructor of {\tt I}, then {\tt - constructor i with \bindinglist} is equivalent to {\tt intros; - apply ci with \bindinglist}. +The proof of {\tt False} is searched in the hypothesis named \ident. +\end{Variants} - \Warning the terms in the \bindinglist\ are checked - in the context where {\tt constructor} is executed and not in the - context where {\tt apply} is executed (the introductions are not - taken into account). +\subsection{\tt contradict \ident} +\label{contradict} +\tacindex{contradict} -% To document? -% \item {\tt constructor {\tactic}} +This tactic allows to manipulate negated hypothesis and goals. The +name \ident\ should correspond to a hypothesis. With +{\tt contradict H}, the current goal and context is transformed in +the following way: +\begin{itemize} +\item {\tt H:$\neg$A $\vd$ B} \ becomes \ {\tt $\vd$ A} +\item {\tt H:$\neg$A $\vd$ $\neg$B} \ becomes \ {\tt H: B $\vd$ A } +\item {\tt H: A $\vd$ B} \ becomes \ {\tt $\vd$ $\neg$A} +\item {\tt H: A $\vd$ $\neg$B} \ becomes \ {\tt H: B $\vd$ $\neg$A} +\end{itemize} -\item {\tt split}\tacindex{split} +\subsection{\tt exfalso} +\label{exfalso} +\tacindex{exfalso} - Applies if {\tt I} has only one constructor, typically in the case - of conjunction $A\land B$. Then, it is equivalent to {\tt constructor 1}. +This tactic implements the ``ex falso quodlibet'' logical principle: +an elimination of {\tt False} is performed on the current goal, and the +user is then required to prove that {\tt False} is indeed provable in +the current context. This tactic is a macro for {\tt elimtype False}. -\item {\tt exists {\bindinglist}}\tacindex{exists} +\section{Case analysis and induction} - Applies if {\tt I} has only one constructor, for instance in the - case of existential quantification $\exists x\cdot P(x)$. - Then, it is equivalent to {\tt intros; constructor 1 with \bindinglist}. +The tactics presented in this section implement induction or case +analysis on inductive or co-inductive objects (see +Section~\ref{Cic-inductive-definitions}). -\item {\tt exists \nelist{\bindinglist}{,}} +\subsection{\tt destruct \term} +\tacindex{destruct} +\label{destruct} - This iteratively applies {\tt exists {\bindinglist}}. +This tactic applies to any goal. The argument {\term} must be of +inductive or co-inductive type and the tactic generates subgoals, one +for each possible form of {\term}, i.e. one for each constructor of +the inductive or co-inductive type. Unlike {\tt induction}, no +induction hypothesis is generated by {\tt destruct}. -\item {\tt left}\tacindex{left}\\ - {\tt right}\tacindex{right} +If the argument is dependent in either the conclusion or some +hypotheses of the goal, the argument is replaced by the appropriate +constructor form in each of the resulting subgoals, thus performing +case analysis. If non-dependent, the tactic simply exposes the +inductive or co-inductive structure of the argument. - Apply if {\tt I} has two constructors, for instance in the case of - disjunction $A\lor B$. Then, they are respectively equivalent to {\tt - constructor 1} and {\tt constructor 2}. - -\item {\tt left with \bindinglist}\\ - {\tt right with \bindinglist}\\ - {\tt split with \bindinglist} - - As soon as the inductive type has the right number of constructors, - these expressions are equivalent to calling {\tt - constructor $i$ with \bindinglist} for the appropriate $i$. +There are special cases: -\item \texttt{econstructor}\tacindex{econstructor}\\ - \texttt{eexists}\tacindex{eexists}\\ - \texttt{esplit}\tacindex{esplit}\\ - \texttt{eleft}\tacindex{eleft}\\ - \texttt{eright}\tacindex{eright}\\ +\begin{itemize} - These tactics and their variants behave like \texttt{constructor}, - \texttt{exists}, \texttt{split}, \texttt{left}, \texttt{right} and - their variants but they introduce existential variables instead of - failing when the instantiation of a variable cannot be found (cf - \texttt{eapply} and Section~\ref{eapply-example}). +\item If {\term} is an identifier {\ident} denoting a quantified +variable of the conclusion of the goal, then {\tt destruct {\ident}} +behaves as {\tt intros until {\ident}; destruct {\ident}}. -\end{Variants} +\item If {\term} is a {\num}, then {\tt destruct {\num}} behaves as +{\tt intros until {\num}} followed by {\tt destruct} applied to the +last introduced hypothesis. Remark: For destruction of a numeral, use +syntax {\tt destruct ({\num})} (not very interesting anyway). + +\item The argument {\term} can also be a pattern of which holes are + denoted by ``\_''. In this case, the tactic checks that all subterms + matching the pattern in the conclusion and the hypotheses are + compatible and performs case analysis using this subterm. -\section[Induction and Case Analysis]{Induction and Case Analysis -\label{Tac-induction}} +\end{itemize} -The tactics presented in this section implement induction or case -analysis on inductive or co-inductive objects (see -Section~\ref{Cic-inductive-definitions}). +\begin{Variants} +\item{\tt destruct \term$_1$, \ldots, \term$_n$} + + This is a shortcut for {\tt destruct \term$_1$; \ldots; destruct \term$_n$}. + +\item{\tt destruct {\term} as {\disjconjintropattern}} + + This behaves as {\tt destruct {\term}} but uses the names in + {\intropattern} to name the variables introduced in the context. + The {\intropattern} must have the form {\tt [} $p_{11}$ \ldots + $p_{1n_1}$ {\tt |} {\ldots} {\tt |} $p_{m1}$ \ldots $p_{mn_m}$ {\tt + ]} with $m$ being the number of constructors of the type of + {\term}. Each variable introduced by {\tt destruct} in the context + of the $i^{th}$ goal gets its name from the list $p_{i1}$ \ldots + $p_{in_i}$ in order. If there are not enough names, {\tt destruct} + invents names for the remaining variables to introduce. More + generally, the $p_{ij}$ can be any disjunctive/conjunctive + introduction pattern (see Section~\ref{intros-pattern}). This + provides a concise notation for nested destruction. + +% It is recommended to use this variant of {\tt destruct} for +% robust proof scripts. + +\item{\tt destruct {\term} eqn:{\namingintropattern}} + + This behaves as {\tt destruct {\term}} but adds an equation between + {\term} and the value that {\term} takes in each of the possible + cases. The name of the equation is specified by {\namingintropattern} + (see Section~\ref{intros-pattern}), in particular {\tt ?} can be + used to let Coq generate a fresh name. + +\item{\tt destruct {\term} as {\disjconjintropattern} \_eqn} + + This behaves as {\tt destruct {\term}} but adds an equation between + {\term} and the value that {\term} takes in each of the possible + cases. The name of the equation is chosen by Coq. If + {\disjconjintropattern} is simply {\tt []}, it is automatically considered + as a disjunctive pattern of the appropriate size. + +\item{\tt destruct {\term} as {\disjconjintropattern} \_eqn:~{\namingintropattern}} + + This behaves as {\tt destruct {\term} as + {\disjconjintropattern} \_eqn} but use {\namingintropattern} to + name the equation (see Section~\ref{intros-pattern}). Note that spaces + can generally be removed around {\tt \_eqn}. + +\item{\tt destruct {\term} with \bindinglist} + + This behaves like \texttt{destruct {\term}} providing explicit + instances for the dependent premises of the type of {\term} (see + syntax of bindings in Section~\ref{Binding-list}). + +\item{\tt edestruct {\term}\tacindex{edestruct}} + + This tactic behaves like \texttt{destruct {\term}} except that it + does not fail if the instance of a dependent premises of the type of + {\term} is not inferable. Instead, the unresolved instances are left + as existential variables to be inferred later, in the same way as + {\tt eapply} does (see Section~\ref{eapply-example}). + +\item{\tt destruct {\term$_1$} using {\term$_2$}}\\ + {\tt destruct {\term$_1$} using {\term$_2$} with {\bindinglist}} -\subsection{\tt induction \term -\tacindex{induction}} + These are synonyms of {\tt induction {\term$_1$} using {\term$_2$}} and + {\tt induction {\term$_1$} using {\term$_2$} with {\bindinglist}}. + +\item \texttt{destruct {\term} in {\occgoalset}} + + This syntax is used for selecting which occurrences of {\term} the + case analysis has to be done on. The {\tt in {\occgoalset}} clause is an + occurrence clause whose syntax and behavior is described in + Section~\ref{Occurrences clauses}. + +% When an occurrence clause is given, an equation between {\term} and +% the value it gets in each case of the analysis is added to the +% context of the subgoals corresponding to the cases (even +% if no clause {\tt as {\namingintropattern}} is given). + +\item{\tt destruct {\term$_1$} with {\bindinglist$_1$} as {\disjconjintropattern} \_eqn:~{\namingintropattern} using {\term$_2$} with {\bindinglist$_2$} in {\occgoalset}}\\ + {\tt edestruct {\term$_1$} with {\bindinglist$_1$} as {\disjconjintropattern} \_eqn:~{\namingintropattern} using {\term$_2$} with {\bindinglist$_2$} in {\occgoalset}} + + These are the general forms of {\tt destruct} and {\tt edestruct}. + They combine the effects of the {\tt with}, {\tt as}, {\tt using}, + and {\tt in} clauses. + +\item{\tt case \term}\label{case}\tacindex{case} + + The tactic {\tt case} is a more basic tactic to perform case + analysis without recursion. It behaves as {\tt elim \term} but using + a case-analysis elimination principle and not a recursive one. + +\item {\tt case {\term} with {\bindinglist}} + + Analogous to {\tt elim {\term} with {\bindinglist}} above. + +\item{\tt ecase {\term}\tacindex{ecase}}\\ + {\tt ecase {\term} with {\bindinglist}} + + In case the type of {\term} has dependent premises, or dependent + premises whose values are not inferable from the {\tt with + {\bindinglist}} clause, {\tt ecase} turns them into existential + variables to be resolved later on. + +\item {\tt simple destruct \ident}\tacindex{simple destruct} + + This tactic behaves as {\tt intros until + {\ident}; case {\tt {\ident}}} when {\ident} is a quantified + variable of the goal. + +\item {\tt simple destruct {\num}} + + This tactic behaves as {\tt intros until + {\num}; case {\tt {\ident}}} where {\ident} is the name given by + {\tt intros until {\num}} to the {\num}-th non-dependent premise of + the goal. + +\item{\tt case\_eq \term}\label{case_eq}\tacindex{case\_eq} + + The tactic {\tt case\_eq} is a variant of the {\tt case} tactic that + allow to perform case analysis on a term without completely + forgetting its original form. This is done by generating equalities + between the original form of the term and the outcomes of the case + analysis. + +% The effect of this tactic is similar to the effect of {\tt +% destruct {\term} in |- *} with the exception that no new hypotheses +% are introduced in the context. + +\end{Variants} + +\subsection{\tt induction \term} +\tacindex{induction} +\label{Tac-induction} This tactic applies to any goal. The argument {\term} must be of inductive type and the tactic {\tt induction} generates subgoals, @@ -1753,15 +1616,15 @@ induction n. \begin{ErrMsgs} \item \errindex{Not an inductive product} \item \errindex{Unable to find an instance for the variables -{\ident} {\ldots} {\ident}} - - Use in this case +{\ident} \ldots {\ident}} + + Use in this case the variant {\tt elim \dots\ with \dots} below. \end{ErrMsgs} \begin{Variants} \item{\tt induction {\term} as {\disjconjintropattern}} - + This behaves as {\tt induction {\term}} but uses the names in {\disjconjintropattern} to name the variables introduced in the context. The {\disjconjintropattern} must typically be of the form @@ -1824,7 +1687,7 @@ induction n. \item \texttt{induction {\term} in {\occgoalset}} This syntax is used for selecting which occurrences of {\term} the - induction has to be carried on. The {\tt in {\atoccurrences}} clause is an + induction has to be carried on. The {\tt in \occgoalset} clause is an occurrence clause whose syntax and behavior is described in Section~\ref{Occurrences clauses}. @@ -1841,7 +1704,7 @@ induction n. {\tt eqn:}, {\tt using}, and {\tt in} clauses. \item {\tt elim \term}\label{elim} - + This is a more basic induction tactic. Again, the type of the argument {\term} must be an inductive type. Then, according to the type of the goal, the tactic {\tt elim} chooses the appropriate @@ -1862,7 +1725,7 @@ induction n. otherwise. \item {\tt elim {\term} with {\bindinglist}} - + Allows to give explicit instances to the premises of the type of {\term} (see Section~\ref{Binding-list}). @@ -1887,7 +1750,7 @@ instantiate premises of the type of {\term$_2$}. of the {\tt with} clause. \item {\tt elimtype \form}\tacindex{elimtype} - + The argument {\form} must be inductively defined. {\tt elimtype I} is equivalent to {\tt cut I. intro H{\rm\sl n}; elim H{\rm\sl n}; clear H{\rm\sl n}}. Therefore the hypothesis {\tt H{\rm\sl n}} will @@ -1897,20 +1760,20 @@ instantiate premises of the type of {\term$_2$}. exact t.} \item {\tt simple induction \ident}\tacindex{simple induction} - + This tactic behaves as {\tt intros until {\ident}; elim {\tt {\ident}}} when {\ident} is a quantified variable of the goal. \item {\tt simple induction {\num}} - + This tactic behaves as {\tt intros until {\num}; elim {\tt {\ident}}} where {\ident} is the name given by {\tt intros until {\num}} to the {\num}-th non-dependent premise of the goal. %% \item {\tt simple induction {\term}}\tacindex{simple induction} - + %% If {\term} is an {\ident} corresponding to a quantified variable of %% the goal then the tactic behaves as {\tt intros until {\ident}; elim %% {\tt {\ident}}}. If {\term} is a {\num} then the tactic behaves as @@ -1922,312 +1785,45 @@ instantiate premises of the type of {\term$_2$}. \end{Variants} -\subsection{\tt destruct \term -\tacindex{destruct}} -\label{destruct} +%\subsection[\tt FixPoint \dots]{\tt FixPoint \dots\tacindex{Fixpoint}} +%Not yet documented. -This tactic applies to any goal. The argument {\term} must be of -inductive or co-inductive type and the tactic generates subgoals, one -for each possible form of {\term}, i.e. one for each constructor of -the inductive or co-inductive type. Unlike {\tt induction}, no -induction hypothesis is generated by {\tt destruct}. +\subsection{\tt double induction \ident$_1$ \ident$_2$} +\tacindex{double induction} -If the argument is dependent in either the conclusion or some -hypotheses of the goal, the argument is replaced by the appropriate -constructor form in each of the resulting subgoals, thus performing -case analysis. If non dependent, the tactic simply exposes the -inductive or co-inductive structure of the argument. +This tactic is deprecated and should be replaced by {\tt induction \ident$_1$; induction \ident$_2$} (or {\tt induction \ident$_1$; destruct \ident$_2$} depending on the exact needs). -There are special cases: +%% This tactic applies to any goal. If the variables {\ident$_1$} and +%% {\ident$_2$} of the goal have an inductive type, then this tactic +%% performs double induction on these variables. For instance, if the +%% current goal is \verb+forall n m:nat, P n m+ then, {\tt double induction n +%% m} yields the four cases with their respective inductive hypotheses. -\begin{itemize} +%% In particular, for proving \verb+(P (S n) (S m))+, the generated induction +%% hypotheses are \verb+(P (S n) m)+ and \verb+(m:nat)(P n m)+ (of the latter, +%% \verb+(P n m)+ and \verb+(P n (S m))+ are derivable). -\item If {\term} is an identifier {\ident} denoting a quantified -variable of the conclusion of the goal, then {\tt destruct {\ident}} -behaves as {\tt intros until {\ident}; destruct {\ident}}. +%% \Rem When the induction hypothesis \verb+(P (S n) m)+ is not +%% needed, {\tt induction \ident$_1$; destruct \ident$_2$} produces +%% more concise subgoals. -\item If {\term} is a {\num}, then {\tt destruct {\num}} behaves as -{\tt intros until {\num}} followed by {\tt destruct} applied to the -last introduced hypothesis. Remark: For destruction of a numeral, use -syntax {\tt destruct ({\num})} (not very interesting anyway). +\begin{Variant} -\item The argument {\term} can also be a pattern of which holes are - denoted by ``\_''. In this case, the tactic checks that all subterms - matching the pattern in the conclusion and the hypotheses are - compatible and performs case analysis using this subterm. +\item {\tt double induction \num$_1$ \num$_2$} -\end{itemize} +This tactic is deprecated and should be replaced by {\tt induction + \num$_1$; induction \num$_3$} where \num$_3$ is the result of +\num$_2$-\num$_1$. -\begin{Variants} -\item{\tt destruct \term$_1$, \ldots, \term$_n$} +%% This applies double induction on the \num$_1^{th}$ and \num$_2^{th}$ {\it +%% non dependent} premises of the goal. More generally, any combination of an +%% {\ident} and a {\num} is valid. - This is a shortcut for {\tt destruct \term$_1$; \ldots; destruct \term$_n$}. +\end{Variant} -\item{\tt destruct {\term} as {\disjconjintropattern}} - - This behaves as {\tt destruct {\term}} but uses the names in - {\intropattern} to name the variables introduced in the context. - The {\intropattern} must have the form {\tt [} $p_{11}$ {\ldots} - $p_{1n_1}$ {\tt |} {\ldots} {\tt |} $p_{m1}$ {\ldots} $p_{mn_m}$ {\tt - ]} with $m$ being the number of constructors of the type of - {\term}. Each variable introduced by {\tt destruct} in the context - of the $i^{th}$ goal gets its name from the list $p_{i1}$ {\ldots} - $p_{in_i}$ in order. If there are not enough names, {\tt destruct} - invents names for the remaining variables to introduce. More - generally, the $p_{ij}$ can be any disjunctive/conjunctive - introduction pattern (see Section~\ref{intros-pattern}). This - provides a concise notation for nested destruction. - -% It is recommended to use this variant of {\tt destruct} for -% robust proof scripts. - -\item{\tt destruct {\term} eqn:{\namingintropattern}} - - This behaves as {\tt destruct {\term}} but adds an equation between - {\term} and the value that {\term} takes in each of the possible - cases. The name of the equation is specified by {\namingintropattern} - (see Section~\ref{intros-pattern}), in particular {\tt ?} can be - used to let Coq generate a fresh name. - -\item{\tt destruct {\term} with \bindinglist} - - This behaves like \texttt{destruct {\term}} providing explicit - instances for the dependent premises of the type of {\term} (see - syntax of bindings in Section~\ref{Binding-list}). - -\item{\tt edestruct {\term}\tacindex{edestruct}} - - This tactic behaves like \texttt{destruct {\term}} excepts that it - does not fail if the instance of a dependent premises of the type of - {\term} is not inferable. Instead, the unresolved instances are left - as existential variables to be inferred later, in the same way as - {\tt eapply} does (see Section~\ref{eapply-example}). - -\item{\tt destruct {\term$_1$} using {\term$_2$}}\\ - {\tt destruct {\term$_1$} using {\term$_2$} with {\bindinglist}} - - These are synonyms of {\tt induction {\term$_1$} using {\term$_2$}} and - {\tt induction {\term$_1$} using {\term$_2$} with {\bindinglist}}. - -\item \texttt{destruct {\term} in {\occgoalset}} - - This syntax is used for selecting which occurrences of {\term} the - case analysis has to be done on. The {\tt in {\occgoalset}} clause is an - occurrence clause whose syntax and behavior is described in - Section~\ref{Occurrences clauses}. - - When an occurrence clause is given, an equation between {\term} and - the value it gets in each case of the analysis is added to the - context of the subgoals corresponding to the cases (even - if no clause {\tt as {\namingintropattern}} is given). - -\item{\tt destruct {\term$_1$} with {\bindinglist$_1$} as {\disjconjintropattern} eqn:{\namingintropattern} using {\term$_2$} with {\bindinglist$_2$} in {\occgoalset}}\\ - {\tt edestruct {\term$_1$} with {\bindinglist$_1$} as {\disjconjintropattern} eqn:{\namingintropattern} using {\term$_2$} with {\bindinglist$_2$} in {\occgoalset}} - - These are the general forms of {\tt destruct} and {\tt edestruct}. - They combine the effects of the {\tt with}, {\tt as}, {\tt eqn:}, {\tt using}, - and {\tt in} clauses. - -\item{\tt case \term}\label{case}\tacindex{case} - - The tactic {\tt case} is a more basic tactic to perform case - analysis without recursion. It behaves as {\tt elim \term} but using - a case-analysis elimination principle and not a recursive one. - -\item{\tt case\_eq \term}\label{case_eq}\tacindex{case\_eq} - - The tactic {\tt case\_eq} is a variant of the {\tt case} tactic that - allow to perform case analysis on a term without completely - forgetting its original form. This is done by generating equalities - between the original form of the term and the outcomes of the case - analysis. The effect of this tactic is similar to the effect of {\tt - destruct {\term} in |- *} with the exception that no new hypotheses - are introduced in the context. - -\item {\tt case {\term} with {\bindinglist}} - - Analogous to {\tt elim {\term} with {\bindinglist}} above. - -\item{\tt ecase {\term}\tacindex{ecase}}\\ - {\tt ecase {\term} with {\bindinglist}} - - In case the type of {\term} has dependent premises, or dependent - premises whose values are not inferable from the {\tt with - {\bindinglist}} clause, {\tt ecase} turns them into existential - variables to be resolved later on. - -\item {\tt simple destruct \ident}\tacindex{simple destruct} - - This tactic behaves as {\tt intros until - {\ident}; case {\tt {\ident}}} when {\ident} is a quantified - variable of the goal. - -\item {\tt simple destruct {\num}} - - This tactic behaves as {\tt intros until - {\num}; case {\tt {\ident}}} where {\ident} is the name given by - {\tt intros until {\num}} to the {\num}-th non-dependent premise of - the goal. - - -\end{Variants} - -\subsection{\tt intros {\intropattern} {\ldots} {\intropattern} -\label{intros-pattern} -\tacindex{intros \intropattern}} -\index{Introduction patterns} -\index{Naming introduction patterns} -\index{Disjunctive/conjunctive introduction patterns} - -This extension of the tactic {\tt intros} combines introduction of -variables or hypotheses and case analysis. An {\em introduction pattern} is -either: -\begin{itemize} -\item A {\em naming introduction pattern}, i.e. either one of: - \begin{itemize} - \item the pattern \texttt{?} - \item the pattern \texttt{?\ident} - \item an identifier - \end{itemize} -\item A {\em disjunctive/conjunctive introduction pattern}, i.e. either one of: - \begin{itemize} - \item a disjunction of lists of patterns: - {\tt [$p_{11}$ {\ldots} $p_{1m_1}$ | {\ldots} | $p_{11}$ {\ldots} $p_{nm_n}$]} - \item a conjunction of patterns: {\tt (} $p_1$ {\tt ,} {\ldots} {\tt ,} $p_n$ {\tt )} - \item a list of patterns {\tt (} $p_1$\ {\tt \&}\ {\ldots}\ {\tt \&}\ $p_n$ {\tt )} - for sequence of right-associative binary constructs - \end{itemize} -\item the wildcard: {\tt \_} -\item the rewriting orientations: {\tt ->} or {\tt <-} -\end{itemize} - -Assuming a goal of type {\tt $Q$ -> $P$} (non dependent product), or -of type {\tt forall $x$:$T$, $P$} (dependent product), the behavior of -{\tt intros $p$} is defined inductively over the structure of the -introduction pattern $p$: -\begin{itemize} -\item introduction on \texttt{?} performs the introduction, and lets {\Coq} - choose a fresh name for the variable; -\item introduction on \texttt{?\ident} performs the introduction, and - lets {\Coq} choose a fresh name for the variable based on {\ident}; -\item introduction on \texttt{\ident} behaves as described in - Section~\ref{intro}; -\item introduction over a disjunction of list of patterns {\tt - [}$p_{11}$ {\ldots} $p_{1m_1}$ {\tt |} {\ldots} {\tt |} $p_{11}$ {\ldots} - $p_{nm_n}${\tt ]} expects the product to be over an inductive type - whose number of constructors is $n$ (or more generally over a type - of conclusion an inductive type built from $n$ constructors, - e.g. {\tt C -> A$\backslash$/B if $n=2$}): it destructs the introduced - hypothesis as {\tt destruct} (see Section~\ref{destruct}) would and - applies on each generated subgoal the corresponding tactic; - \texttt{intros}~$p_{i1}$ {\ldots} $p_{im_i}$; if the disjunctive - pattern is part of a sequence of patterns and is not the last - pattern of the sequence, then {\Coq} completes the pattern so as all - the argument of the constructors of the inductive type are - introduced (for instance, the list of patterns {\tt [$\;$|$\;$] H} - applied on goal {\tt forall x:nat, x=0 -> 0=x} behaves the same as - the list of patterns {\tt [$\,$|$\,$?$\,$] H}); -\item introduction over a conjunction of patterns {\tt (}$p_1${\tt ,} {\ldots}{\tt ,} - $p_n${\tt )} expects the goal to be a product over an inductive type $I$ with a - single constructor that itself has at least $n$ arguments: it - performs a case analysis over the hypothesis, as {\tt destruct} - would, and applies the patterns $p_1$ {\ldots} $p_n$ to the arguments - of the constructor of $I$ (observe that {\tt ($p_1$, {\ldots}, - $p_n$)} is an alternative notation for {\tt [$p_1$ {\ldots} - $p_n$]}); -\item introduction via {\tt (} $p_1$ {\tt \&} {\ldots} {\tt \&} $p_n$ {\tt )} - is a shortcut for introduction via - {\tt (}$p_1$ {\tt ,(}{\ldots}{\tt ,(}{\dots}{\tt ,}$p_n$){\ldots}{\tt ))}; it expects the - hypothesis to be a sequence of right-associative binary inductive - constructors such as {\tt conj} or {\tt ex\_intro}; for instance, an - hypothesis with type {\tt A\verb|/\|exists x, B\verb|/\|C\verb|/\|D} can be - introduced via pattern {\tt (a \& x \& b \& c \& d)}; -\item introduction on the wildcard depends on whether the product is - dependent or not: in the non dependent case, it erases the - corresponding hypothesis (i.e. it behaves as an {\tt intro} followed - by a {\tt clear}, cf Section~\ref{clear}) while in the dependent - case, it succeeds and erases the variable only if the wildcard is - part of a more complex list of introduction patterns that also - erases the hypotheses depending on this variable; -\item introduction over {\tt ->} (respectively {\tt <-}) expects the - hypothesis to be an equality and the right-hand-side (respectively - the left-hand-side) is replaced by the left-hand-side (respectively - the right-hand-side) in both the conclusion and the context of the goal; - if moreover the term to substitute is a variable, the hypothesis is - removed. -\end{itemize} - -\Rem {\tt intros} $p_1$ {\ldots} $p_n$ is not equivalent to \texttt{intros} - $p_1${\tt ;} {\ldots}{\tt ; intros} $p_n$ for the following reasons: -\begin{itemize} -\item A wildcard pattern never succeeds when applied isolated on a - dependent product, while it succeeds as part of a list of - introduction patterns if the hypotheses that depends on it are - erased too. -\item A disjunctive or conjunctive pattern followed by an introduction - pattern forces the introduction in the context of all arguments of - the constructors before applying the next pattern while a terminal - disjunctive or conjunctive pattern does not. Here is an example - -\begin{coq_example} -Goal forall n:nat, n = 0 -> n = 0. -intros [ | ] H. -Show 2. -Undo. -intros [ | ]; intros H. -Show 2. -\end{coq_example} - -\end{itemize} - -\begin{coq_example} -Lemma intros_test : forall A B C:Prop, A \/ B /\ C -> (A -> C) -> C. -intros A B C [a| [_ c]] f. -apply (f a). -exact c. -Qed. -\end{coq_example} - -%\subsection[\tt FixPoint \dots]{\tt FixPoint \dots\tacindex{Fixpoint}} -%Not yet documented. - -\subsection{\tt double induction \ident$_1$ \ident$_2$} -%\tacindex{double induction}} -This tactic is deprecated and should be replaced by {\tt induction \ident$_1$; induction \ident$_2$} (or {\tt induction \ident$_1$; destruct \ident$_2$} depending on the exact needs). - -%% This tactic applies to any goal. If the variables {\ident$_1$} and -%% {\ident$_2$} of the goal have an inductive type, then this tactic -%% performs double induction on these variables. For instance, if the -%% current goal is \verb+forall n m:nat, P n m+ then, {\tt double induction n -%% m} yields the four cases with their respective inductive hypotheses. - -%% In particular, for proving \verb+(P (S n) (S m))+, the generated induction -%% hypotheses are \verb+(P (S n) m)+ and \verb+(m:nat)(P n m)+ (of the latter, -%% \verb+(P n m)+ and \verb+(P n (S m))+ are derivable). - -%% \Rem When the induction hypothesis \verb+(P (S n) m)+ is not -%% needed, {\tt induction \ident$_1$; destruct \ident$_2$} produces -%% more concise subgoals. - -\begin{Variant} - -\item {\tt double induction \num$_1$ \num$_2$} - -This tactic is deprecated and should be replaced by {\tt induction - \num$_1$; induction \num$_3$} where \num$_3$ is the result of -\num$_2$-\num$_1$. - -%% This tactic applies to any goal. If the variables {\ident$_1$} and - -%% This applies double induction on the \num$_1^{th}$ and \num$_2^{th}$ {\it -%% non dependent} premises of the goal. More generally, any combination of an -%% {\ident} and a {\num} is valid. - -\end{Variant} - -\subsection{\tt dependent induction \ident - \tacindex{dependent induction} - \label{DepInduction}} +\subsection{\tt dependent induction \ident} +\tacindex{dependent induction} +\label{DepInduction} The \emph{experimental} tactic \texttt{dependent induction} performs induction-inversion on an instantiated inductive predicate. @@ -2235,12 +1831,13 @@ One needs to first require the {\tt Coq.Program.Equality} module to use this tactic. The tactic is based on the BasicElim tactic by Conor McBride \cite{DBLP:conf/types/McBride00} and the work of Cristina Cornes around inversion \cite{DBLP:conf/types/CornesT95}. From an instantiated -inductive predicate and a goal it generates an equivalent goal where the +inductive predicate and a goal, it generates an equivalent goal where the hypothesis has been generalized over its indexes which are then constrained by equalities to be the right instances. This permits to state lemmas without resorting to manually adding these equalities and -still get enough information in the proofs. -A simple example is the following: +still get enough information in the proofs. + +\Example \begin{coq_eval} Reset Initial. @@ -2250,8 +1847,8 @@ Lemma le_minus : forall n:nat, n < 1 -> n = 0. intros n H ; induction H. \end{coq_example} -Here we didn't get any information on the indexes to help fulfill this -proof. The problem is that when we use the \texttt{induction} tactic +Here we did not get any information on the indexes to help fulfill this +proof. The problem is that, when we use the \texttt{induction} tactic, we lose information on the hypothesis instance, notably that the second argument is \texttt{1} here. Dependent induction solves this problem by adding the corresponding equality to the context. @@ -2267,7 +1864,7 @@ intros n H ; dependent induction H. The subgoal is cleaned up as the tactic tries to automatically simplify the subgoals with respect to the generated equalities. -In this enriched context it becomes possible to solve this subgoal. +In this enriched context, it becomes possible to solve this subgoal. \begin{coq_example} reflexivity. \end{coq_example} @@ -2281,65 +1878,32 @@ This technique works with any inductive predicate. In fact, the \texttt{dependent induction} tactic is just a wrapper around the \texttt{induction} tactic. One can make its own variant by just writing a new tactic based on the definition found in -\texttt{Coq.Program.Equality}. Common useful variants are the following, -defined in the same file: +\texttt{Coq.Program.Equality}. \begin{Variants} \item {\tt dependent induction {\ident} generalizing {\ident$_1$} \dots {\ident$_n$}}\tacindex{dependent induction \dots\ generalizing} - - Does dependent induction on the hypothesis {\ident} but first + + This performs dependent induction on the hypothesis {\ident} but first generalizes the goal by the given variables so that they are universally quantified in the goal. This is generally what one wants to do with the variables that are inside some constructors in the induction hypothesis. The other ones need not be further generalized. \item {\tt dependent destruction {\ident}}\tacindex{dependent destruction} - - Does the generalization of the instance {\ident} but uses {\tt destruct} + + This performs the generalization of the instance {\ident} but uses {\tt destruct} instead of {\tt induction} on the generalized hypothesis. This gives results equivalent to {\tt inversion} or {\tt dependent inversion} if the hypothesis is dependent. \end{Variants} -A larger example of dependent induction and an explanation of the -underlying technique are developed in section~\ref{dependent-induction-example}. - -\subsection{\tt decompose [ {\qualid$_1$} \dots\ {\qualid$_n$} ] \term -\label{decompose} -\tacindex{decompose}} - -This tactic allows to recursively decompose a -complex proposition in order to obtain atomic ones. -Example: - -\begin{coq_eval} -Reset Initial. -\end{coq_eval} -\begin{coq_example} -Lemma ex1 : forall A B C:Prop, A /\ B /\ C \/ B /\ C \/ C /\ A -> C. -intros A B C H; decompose [and or] H; assumption. -\end{coq_example} -\begin{coq_example*} -Qed. -\end{coq_example*} - -{\tt decompose} does not work on right-hand sides of implications or products. - -\begin{Variants} - -\item {\tt decompose sum \term}\tacindex{decompose sum} - This decomposes sum types (like \texttt{or}). -\item {\tt decompose record \term}\tacindex{decompose record} - This decomposes record types (inductive types with one constructor, - like \texttt{and} and \texttt{exists} and those defined with the - \texttt{Record} macro, see Section~\ref{Record}). -\end{Variants} - +\SeeAlso \ref{dependent-induction-example} for a larger example of +dependent induction and an explanation of the underlying technique. -\subsection{\tt functional induction (\qualid\ \term$_1$ \dots\ \term$_n$). +\subsection{\tt functional induction (\qualid\ \term$_1$ \dots\ \term$_n$)} \tacindex{functional induction} -\label{FunInduction}} +\label{FunInduction} The \emph{experimental} tactic \texttt{functional induction} performs case analysis and induction following the definition of a function. It @@ -2352,9 +1916,8 @@ Reset Initial. \end{coq_eval} \begin{coq_example} Functional Scheme minus_ind := Induction for minus Sort Prop. - -Lemma le_minus : forall n m:nat, (n - m <= n). -intros n m. +Check minus_ind. +Lemma le_minus (n m:nat) : n - m <= n. functional induction (minus n m); simpl; auto. \end{coq_example} \begin{coq_example*} @@ -2366,15 +1929,15 @@ full application of \qualid. In particular, the rules for implicit arguments are the same as usual. For example use \texttt{@\qualid} if you want to write implicit arguments explicitly. -\Rem Parenthesis over \qualid \dots \term$_n$ are mandatory. +\Rem Parentheses over \qualid \dots \term$_n$ are mandatory. \Rem \texttt{functional induction (f x1 x2 x3)} is actually a wrapper for \texttt{induction x1 x2 x3 (f x1 x2 x3) using \qualid} followed by -a cleaning phase, where $\qualid$ is the induction principle +a cleaning phase, where {\qualid} is the induction principle registered for $f$ (by the \texttt{Function} (see Section~\ref{Function}) or \texttt{Functional Scheme} (see Section~\ref{FunScheme}) command) corresponding to the sort of the goal. Therefore \texttt{functional - induction} may fail if the induction scheme (\texttt{\qualid}) is + induction} may fail if the induction scheme {\qualid} is not defined. See also Section~\ref{Function} for the function terms accepted by \texttt{Function}. @@ -2389,988 +1952,1858 @@ details. \begin{ErrMsgs} \item \errindex{Cannot find induction information on \qualid} - - ~ - \item \errindex{Not the right number of induction arguments} \end{ErrMsgs} \begin{Variants} \item {\tt functional induction (\qualid\ \term$_1$ \dots\ \term$_n$) - using \term$_{m+1}$ with {\term$_{n+1}$} \dots {\term$_m$}} + as {\disjconjintropattern} using \term$_{m+1}$ with \bindinglist} - Similar to \texttt{Induction} and \texttt{elim} - (see Section~\ref{Tac-induction}), allows to give explicitly the - induction principle and the values of dependent premises of the + Similarly to \texttt{Induction} and \texttt{elim} + (see Section~\ref{Tac-induction}), this allows to give explicitly the + name of the introduced variables, the + induction principle, and the values of dependent premises of the elimination scheme, including \emph{predicates} for mutual induction when {\qualid} is part of a mutually recursive definition. -\item {\tt functional induction (\qualid\ \term$_1$ \dots\ \term$_n$) - using \term$_{m+1}$ with {\vref$_1$} := {\term$_{n+1}$} \dots\ - {\vref$_m$} := {\term$_n$}} - - Similar to \texttt{induction} and \texttt{elim} - (see Section~\ref{Tac-induction}). - -\item All previous variants can be extended by the usual \texttt{as - \intropattern} construction, similar for example to - \texttt{induction} and \texttt{elim} (see Section~\ref{Tac-induction}). - \end{Variants} +\subsection{\tt discriminate \term} +\label{discriminate} +\tacindex{discriminate} -\section{Equality} - -These tactics use the equality {\tt eq:forall A:Type, A->A->Prop} -defined in file {\tt Logic.v} (see Section~\ref{Equality}). The -notation for {\tt eq}~$T~t~u$ is simply {\tt $t$=$u$} dropping the -implicit type of $t$ and $u$. +This tactic proves any goal from an assumption stating that two +structurally different terms of an inductive set are equal. For +example, from {\tt (S (S O))=(S O)} we can derive by absurdity any +proposition. -\subsection{\tt rewrite \term +The argument {\term} is assumed to be a proof of a statement +of conclusion {\tt{\term$_1$} = {\term$_2$}} with {\term$_1$} and +{\term$_2$} being elements of an inductive set. To build the proof, +the tactic traverses the normal forms\footnote{Reminder: opaque + constants will not be expanded by $\delta$ reductions.} of +{\term$_1$} and {\term$_2$} looking for a couple of subterms {\tt u} +and {\tt w} ({\tt u} subterm of the normal form of {\term$_1$} and +{\tt w} subterm of the normal form of {\term$_2$}), placed at the same +positions and whose head symbols are two different constructors. If +such a couple of subterms exists, then the proof of the current goal +is completed, otherwise the tactic fails. + +\Rem The syntax {\tt discriminate {\ident}} can be used to refer to a +hypothesis quantified in the goal. In this case, the quantified +hypothesis whose name is {\ident} is first introduced in the local +context using \texttt{intros until \ident}. + +\begin{ErrMsgs} +\item \errindex{No primitive equality found} +\item \errindex{Not a discriminable equality} +\end{ErrMsgs} + +\begin{Variants} +\item \texttt{discriminate \num} + + This does the same thing as \texttt{intros until \num} followed by + \texttt{discriminate \ident} where {\ident} is the identifier for + the last introduced hypothesis. + +\item \texttt{discriminate {\term} with \bindinglist} + + This does the same thing as \texttt{discriminate {\term}} but using +the given bindings to instantiate parameters or hypotheses of {\term}. + +\item \texttt{ediscriminate \num}\tacindex{ediscriminate}\\ + \texttt{ediscriminate {\term} \zeroone{with \bindinglist}} + + This works the same as {\tt discriminate} but if the type of {\term}, + or the type of the hypothesis referred to by {\num}, has uninstantiated + parameters, these parameters are left as existential variables. + +\item \texttt{discriminate} + + This behaves like {\tt discriminate {\ident}} if {\ident} is the + name of an hypothesis to which {\tt discriminate} is applicable; if + the current goal is of the form {\term$_1$} {\tt <>} {\term$_2$}, + this behaves as {\tt intro {\ident}; injection {\ident}}. + + \ErrMsg \errindex{No discriminable equalities} +\end{Variants} + +\subsection{\tt injection \term} +\label{injection} +\tacindex{injection} + +The {\tt injection} tactic is based on the fact that constructors of +inductive sets are injections. That means that if $c$ is a constructor +of an inductive set, and if $(c~\vec{t_1})$ and $(c~\vec{t_2})$ are two +terms that are equal then $~\vec{t_1}$ and $~\vec{t_2}$ are equal +too. + +If {\term} is a proof of a statement of conclusion + {\tt {\term$_1$} = {\term$_2$}}, +then {\tt injection} applies injectivity as deep as possible to +derive the equality of all the subterms of {\term$_1$} and {\term$_2$} +placed in the same positions. For example, from {\tt (S + (S n))=(S (S (S m)))} we may derive {\tt n=(S m)}. To use this +tactic {\term$_1$} and {\term$_2$} should be elements of an inductive +set and they should be neither explicitly equal, nor structurally +different. We mean by this that, if {\tt n$_1$} and {\tt n$_2$} are +their respective normal forms, then: +\begin{itemize} +\item {\tt n$_1$} and {\tt n$_2$} should not be syntactically equal, +\item there must not exist any pair of subterms {\tt u} and {\tt w}, + {\tt u} subterm of {\tt n$_1$} and {\tt w} subterm of {\tt n$_2$} , + placed in the same positions and having different constructors as + head symbols. +\end{itemize} +If these conditions are satisfied, then, the tactic derives the +equality of all the subterms of {\term$_1$} and {\term$_2$} placed in +the same positions and puts them as antecedents of the current goal. + +\Example Consider the following goal: + +\begin{coq_example*} +Inductive list : Set := + | nil : list + | cons : nat -> list -> list. +Variable P : list -> Prop. +\end{coq_example*} +\begin{coq_eval} +Lemma ex : + forall (l:list) (n:nat), P nil -> cons n l = cons 0 nil -> P l. +intros l n H H0. +\end{coq_eval} +\begin{coq_example} +Show. +injection H0. +\end{coq_example} +\begin{coq_eval} +Abort. +\end{coq_eval} + +Beware that \texttt{injection} yields always an equality in a sigma type +whenever the injected object has a dependent type. + +\Rem There is a special case for dependent pairs. If we have a decidable +equality over the type of the first argument, then it is safe to do +the projection on the second one, and so {\tt injection} will work fine. +To define such an equality, you have to use the {\tt Scheme} command +(see \ref{Scheme}). + +\Rem If some quantified hypothesis of the goal is named {\ident}, then +{\tt injection {\ident}} first introduces the hypothesis in the local +context using \texttt{intros until \ident}. + +\begin{ErrMsgs} +\item \errindex{Not a projectable equality but a discriminable one} +\item \errindex{Nothing to do, it is an equality between convertible terms} +\item \errindex{Not a primitive equality} +\end{ErrMsgs} + +\begin{Variants} +\item \texttt{injection \num} + + This does the same thing as \texttt{intros until \num} followed by +\texttt{injection \ident} where {\ident} is the identifier for the last +introduced hypothesis. + +\item \texttt{injection {\term} with \bindinglist} + + This does the same as \texttt{injection {\term}} but using + the given bindings to instantiate parameters or hypotheses of {\term}. + +\item \texttt{einjection \num}\tacindex{einjection}\\ + \texttt{einjection {\term} \zeroone{with \bindinglist}} + + This works the same as {\tt injection} but if the type of {\term}, + or the type of the hypothesis referred to by {\num}, has uninstantiated + parameters, these parameters are left as existential variables. + +\item{\tt injection} + + If the current goal is of the form {\term$_1$} {\tt <>} {\term$_2$}, + this behaves as {\tt intro {\ident}; injection {\ident}}. + + \ErrMsg \errindex{goal does not satisfy the expected preconditions} + +\item \texttt{injection {\term} \zeroone{with \bindinglist} as \nelist{\intropattern}{}}\\ +\texttt{injection {\num} as {\intropattern} \dots\ \intropattern}\\ +\texttt{injection as {\intropattern} \dots\ \intropattern}\\ +\texttt{einjection {\term} \zeroone{with \bindinglist} as \nelist{\intropattern}{}}\\ +\texttt{einjection {\num} as {\intropattern} \dots\ \intropattern}\\ +\texttt{einjection as {\intropattern} \dots\ \intropattern} +\tacindex{injection \dots\ as} + +These variants apply \texttt{intros} \nelist{\intropattern}{} after +the call to \texttt{injection} or \texttt{einjection}. + +\end{Variants} + +\subsection{\tt inversion \ident} +\tacindex{inversion} + +Let the type of {\ident} in the local context be $(I~\vec{t})$, +where $I$ is a (co)inductive predicate. Then, +\texttt{inversion} applied to \ident~ derives for each possible +constructor $c_i$ of $(I~\vec{t})$, {\bf all} the necessary +conditions that should hold for the instance $(I~\vec{t})$ to be +proved by $c_i$. + +\Rem If {\ident} does not denote a hypothesis in the local context +but refers to a hypothesis quantified in the goal, then the +latter is first introduced in the local context using +\texttt{intros until \ident}. + +\Rem 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 Section~\ref{Derive-Inversion}. + +\begin{Variants} +\item \texttt{inversion \num} + + This does the same thing as \texttt{intros until \num} then + \texttt{inversion \ident} where {\ident} is the identifier for the + last introduced hypothesis. + +\item \tacindex{inversion\_clear} \texttt{inversion\_clear \ident} + + This behaves as \texttt{inversion} and then erases \ident~ from the + context. + +\item \tacindex{inversion \dots\ as} \texttt{inversion {\ident} as \intropattern} + + This behaves as \texttt{inversion} but using names in + {\intropattern} for naming hypotheses. The {\intropattern} must have + the form {\tt [} $p_{11}$ \ldots $p_{1n_1}$ {\tt |} {\ldots} {\tt |} + $p_{m1}$ \ldots $p_{mn_m}$ {\tt ]} with $m$ being the number of + constructors of the type of {\ident}. Be careful that the list must + be of length $m$ even if {\tt inversion} discards some cases (which + is precisely one of its roles): for the discarded cases, just use an + empty list (i.e. $n_i=0$). + + The arguments of the $i^{th}$ constructor and the + equalities that {\tt inversion} introduces in the context of the + goal corresponding to the $i^{th}$ constructor, if it exists, get + their names from the list $p_{i1}$ \ldots $p_{in_i}$ in order. If + there are not enough names, {\tt induction} invents names for the + remaining variables to introduce. In case an equation splits into + several equations (because {\tt inversion} applies {\tt injection} + on the equalities it generates), the corresponding name $p_{ij}$ in + the list must be replaced by a sublist of the form {\tt [$p_{ij1}$ + \ldots $p_{ijq}$]} (or, equivalently, {\tt ($p_{ij1}$, + \ldots, $p_{ijq}$)}) where $q$ is the number of subequalities + obtained from splitting the original equation. Here is an example. + +\begin{coq_eval} +Require Import List. +\end{coq_eval} + +\begin{coq_example} +Inductive contains0 : list nat -> Prop := + | in_hd : forall l, contains0 (0 :: l) + | in_tl : forall l b, contains0 l -> contains0 (b :: l). +Goal forall l:list nat, contains0 (1 :: l) -> contains0 l. +intros l H; inversion H as [ | l' p Hl' [Heqp Heql'] ]. +\end{coq_example} + +\begin{coq_eval} +Abort. +\end{coq_eval} + +\item \texttt{inversion {\num} as \intropattern} + + This allows to name the hypotheses introduced by + \texttt{inversion \num} in the context. + +\item \tacindex{inversion\_clear \dots\ as} \texttt{inversion\_clear + {\ident} as \intropattern} + + This allows to name the hypotheses introduced by + \texttt{inversion\_clear} in the context. + +\item \tacindex{inversion \dots\ in} \texttt{inversion {\ident} + in \ident$_1$ \dots\ \ident$_n$} + + Let \ident$_1$ \dots\ \ident$_n$, be identifiers in the local context. This + tactic behaves as generalizing \ident$_1$ \dots\ \ident$_n$, and + then performing \texttt{inversion}. + +\item \tacindex{inversion \dots\ as \dots\ in} \texttt{inversion + {\ident} as {\intropattern} in \ident$_1$ \dots\ + \ident$_n$} + + This allows to name the hypotheses introduced in the context by + \texttt{inversion {\ident} in \ident$_1$ \dots\ \ident$_n$}. + +\item \tacindex{inversion\_clear \dots\ in} \texttt{inversion\_clear + {\ident} in \ident$_1$ \dots\ \ident$_n$} + + Let \ident$_1$ \dots\ \ident$_n$, be identifiers in the local context. This + tactic behaves as generalizing \ident$_1$ \dots\ \ident$_n$, and + then performing {\tt inversion\_clear}. + +\item \tacindex{inversion\_clear \dots\ as \dots\ in} + \texttt{inversion\_clear {\ident} as {\intropattern} + in \ident$_1$ \dots\ \ident$_n$} + + This allows to name the hypotheses introduced in the context by + \texttt{inversion\_clear {\ident} in \ident$_1$ \dots\ \ident$_n$}. + +\item \tacindex{dependent inversion} \texttt{dependent inversion \ident} + + That must be used when \ident\ appears in the current goal. It acts + like \texttt{inversion} and then substitutes \ident\ for the + corresponding term in the goal. + +\item \tacindex{dependent inversion \dots\ as } \texttt{dependent + inversion {\ident} as \intropattern} + + This allows to name the hypotheses introduced in the context by + \texttt{dependent inversion} {\ident}. + +\item \tacindex{dependent inversion\_clear} \texttt{dependent + inversion\_clear \ident} + + Like \texttt{dependent inversion}, except that {\ident} is cleared + from the local context. + +\item \tacindex{dependent inversion\_clear \dots\ as} + \texttt{dependent inversion\_clear {\ident} as \intropattern} + + This allows to name the hypotheses introduced in the context by + \texttt{dependent inversion\_clear} {\ident}. + +\item \tacindex{dependent inversion \dots\ with} \texttt{dependent + inversion {\ident} with \term} + + This variant allows you to specify the generalization of the goal. It + is useful when the system fails to generalize the goal automatically. If + {\ident} has type $(I~\vec{t})$ and $I$ has type + $\forall (\vec{x}:\vec{T}), s$, then \term~ must be of type + $I:\forall (\vec{x}:\vec{T}), I~\vec{x}\to s'$ where $s'$ is the + type of the goal. + +\item \tacindex{dependent inversion \dots\ as \dots\ with} + \texttt{dependent inversion {\ident} as {\intropattern} + with \term} + + This allows to name the hypotheses introduced in the context by + \texttt{dependent inversion {\ident} with \term}. + +\item \tacindex{dependent inversion\_clear \dots\ with} + \texttt{dependent inversion\_clear {\ident} with \term} + + Like \texttt{dependent inversion \dots\ with} but clears {\ident} from + the local context. + +\item \tacindex{dependent inversion\_clear \dots\ as \dots\ with} + \texttt{dependent inversion\_clear {\ident} as + {\intropattern} with \term} + + This allows to name the hypotheses introduced in the context by + \texttt{dependent inversion\_clear {\ident} with \term}. + +\item \tacindex{simple inversion} \texttt{simple inversion \ident} + + It is a very primitive inversion tactic that derives all the necessary + equalities but it does not simplify the constraints as + \texttt{inversion} does. + +\item \tacindex{simple inversion \dots\ as} \texttt{simple inversion + {\ident} as \intropattern} + + This allows to name the hypotheses introduced in the context by + \texttt{simple inversion}. + +\item \tacindex{inversion \dots\ using} \texttt{inversion {\ident} + using \ident$'$} + + Let {\ident} have type $(I~\vec{t})$ ($I$ an inductive + predicate) in the local context, and \ident$'$ be a (dependent) inversion + lemma. Then, this tactic refines the current goal with the specified + lemma. + +\item \tacindex{inversion \dots\ using \dots\ in} \texttt{inversion + {\ident} using \ident$'$ in \ident$_1$\dots\ \ident$_n$} + + This tactic behaves as generalizing \ident$_1$\dots\ \ident$_n$, + then doing \texttt{inversion {\ident} using \ident$'$}. + +\end{Variants} + +\firstexample +\example{Non-dependent inversion} +\label{inversion-examples} + +Let us consider the relation \texttt{Le} over natural numbers and the +following variables: + +\begin{coq_eval} +Reset Initial. +\end{coq_eval} + +\begin{coq_example*} +Inductive Le : nat -> nat -> Set := + | LeO : forall n:nat, Le 0 n + | LeS : forall n m:nat, Le n m -> Le (S n) (S m). +Variable P : nat -> nat -> Prop. +Variable Q : forall n m:nat, Le n m -> Prop. +\end{coq_example*} + +Let us consider the following goal: + +\begin{coq_eval} +Lemma ex : forall n m:nat, Le (S n) m -> P n m. +intros. +\end{coq_eval} + +\begin{coq_example} +Show. +\end{coq_example} + +To prove the goal, we may need to reason by cases on \texttt{H} and to +derive that \texttt{m} is necessarily of +the form $(S~m_0)$ for certain $m_0$ and that $(Le~n~m_0)$. +Deriving these conditions corresponds to prove that the +only possible constructor of \texttt{(Le (S n) m)} is +\texttt{LeS} and that we can invert the +\texttt{->} in the type of \texttt{LeS}. +This inversion is possible because \texttt{Le} is the smallest set closed by +the constructors \texttt{LeO} and \texttt{LeS}. + +\begin{coq_example} +inversion_clear H. +\end{coq_example} + +Note that \texttt{m} has been substituted in the goal for \texttt{(S m0)} +and that the hypothesis \texttt{(Le n m0)} has been added to the +context. + +Sometimes it is +interesting to have the equality \texttt{m=(S m0)} in the +context to use it after. In that case we can use \texttt{inversion} that +does not clear the equalities: + +\begin{coq_eval} +Undo. +\end{coq_eval} + +\begin{coq_example} +inversion H. +\end{coq_example} + +\begin{coq_eval} +Abort. +\end{coq_eval} + +\example{Dependent inversion} + +Let us consider the following goal: + +\begin{coq_eval} +Lemma ex_dep : forall (n m:nat) (H:Le (S n) m), Q (S n) m H. +intros. +\end{coq_eval} + +\begin{coq_example} +Show. +\end{coq_example} + +As \texttt{H} occurs in the goal, we may want to reason by cases on its +structure and so, we would like inversion tactics to +substitute \texttt{H} by the corresponding term in constructor form. +Neither \texttt{Inversion} nor {\tt Inversion\_clear} make such a +substitution. +To have such a behavior we use the dependent inversion tactics: + +\begin{coq_example} +dependent inversion_clear H. +\end{coq_example} + +Note that \texttt{H} has been substituted by \texttt{(LeS n m0 l)} and +\texttt{m} by \texttt{(S m0)}. + +\subsection{\tt fix {\ident} {\num}} +\tacindex{fix} +\label{tactic:fix} + +This tactic is a primitive tactic to start a proof by induction. In +general, it is easier to rely on higher-level induction tactics such +as the ones described in Section~\ref{Tac-induction}. + +In the syntax of the tactic, the identifier {\ident} is the name given +to the induction hypothesis. The natural number {\num} tells on which +premise of the current goal the induction acts, starting +from 1 and counting both dependent and non dependent +products. Especially, the current lemma must be composed of at least +{\num} products. + +Like in a {\tt fix} expression, the induction +hypotheses have to be used on structurally smaller arguments. +The verification that inductive 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 {\tt + Guarded} (see Section~\ref{Guarded}). + +\begin{Variants} + \item {\tt fix \ident$_1$ {\num} with ( \ident$_2$ + \nelist{\binder$_2$}{} \zeroone{\{ struct \ident$'_2$ + \}} :~\type$_2$ ) \dots\ ( \ident$_n$ + \nelist{\binder$_n$}{} \zeroone{\{ struct \ident$'_n$ \}} :~\type$_n$ )} + +This starts a proof by mutual induction. The statements to be +simultaneously proved are respectively {\tt forall} + \nelist{{\binder}$_2$}{}{\tt ,} {\type}$_2$, {\ldots}, {\tt forall} + \nelist{{\binder}$_n$}{}{\tt ,} {\type}$_n$. The identifiers +{\ident}$_1$ {\ldots} {\ident}$_n$ are the names of the induction +hypotheses. The identifiers {\ident}$'_2$ {\ldots} {\ident}$'_n$ are the +respective names of the premises on which the induction is performed +in the statements to be simultaneously proved (if not given, the +system tries to guess itself what they are). + +\end{Variants} + +\subsection{\tt cofix \ident} +\tacindex{cofix} +\label{tactic:cofix} + +This tactic starts a proof by coinduction. The identifier {\ident} is +the name given to the coinduction hypothesis. Like in a {\tt cofix} +expression, the use of induction hypotheses have to guarded by a +constructor. The verification that the use of co-inductive hypotheses +is correct is 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 {\tt Guarded} (see Section~\ref{Guarded}). + + +\begin{Variants} + \item {\tt cofix \ident$_1$ with ( \ident$_2$ + \nelist{\binder$_2$}{} :~\type$_2$ ) \dots\ ( + \ident$_n$ \nelist{\binder$_n$}{} :~\type$_n$ )} + +This starts a proof by mutual coinduction. The statements to be +simultaneously proved are respectively {\tt forall} +\nelist{{\binder}$_2$}{}{\tt ,} {\type}$_2$, {\ldots}, {\tt forall} + \nelist{{\binder}$_n$}{}{\tt ,} {\type}$_n$. The identifiers + {\ident}$_1$ {\ldots} {\ident}$_n$ are the names of the + coinduction hypotheses. + +\end{Variants} + +\section{Rewriting expressions} + + +These tactics use the equality {\tt eq:forall A:Type, A->A->Prop} +defined in file {\tt Logic.v} (see Section~\ref{Equality}). The +notation for {\tt eq}~$T~t~u$ is simply {\tt $t$=$u$} dropping the +implicit type of $t$ and $u$. + +\subsection{\tt rewrite \term \label{rewrite} \tacindex{rewrite}} -This tactic applies to any goal. The type of {\term} -must have the form +This tactic applies to any goal. The type of {\term} +must have the form + +\texttt{forall (x$_1$:A$_1$) \dots\ (x$_n$:A$_n$)}\texttt{eq} \term$_1$ \term$_2$. + +\noindent where \texttt{eq} is the Leibniz equality or a registered +setoid equality. + +\noindent Then {\tt rewrite \term} finds the first subterm matching +\term$_1$ in the goal, resulting in instances \term$_1'$ and \term$_2'$ +and then replaces every occurrence of \term$_1'$ by \term$_2'$. +Hence, some of the variables x$_i$ are +solved by unification, and some of the types \texttt{A}$_1$, \dots, +\texttt{A}$_n$ become new subgoals. + +% \Rem In case the type of +% \term$_1$ contains occurrences of variables bound in the +% type of \term, the tactic tries first to find a subterm of the goal +% which matches this term in order to find a closed instance \term$'_1$ +% of \term$_1$, and then all instances of \term$'_1$ will be replaced. + +\begin{ErrMsgs} +\item \errindex{The term provided does not end with an equation} + +\item \errindex{Tactic generated a subgoal identical to the original goal}\\ +This happens if \term$_1$ does not occur in the goal. +\end{ErrMsgs} + +\begin{Variants} +\item {\tt rewrite -> {\term}}\tacindex{rewrite ->}\\ + Is equivalent to {\tt rewrite \term} + +\item {\tt rewrite <- {\term}}\tacindex{rewrite <-}\\ + Uses the equality \term$_1${\tt=}\term$_2$ from right to left + +\item {\tt rewrite {\term} in \textit{clause}} + \tacindex{rewrite \dots\ in}\\ + Analogous to {\tt rewrite {\term}} but rewriting is done following + \textit{clause} (similarly to \ref{Conversion-tactics}). For + instance: + \begin{itemize} + \item \texttt{rewrite H in H1} will rewrite \texttt{H} in the hypothesis + \texttt{H1} instead of the current goal. + \item \texttt{rewrite H in H1 at 1, H2 at - 2 |- *} means \texttt{rewrite H; rewrite H in H1 at 1; + rewrite H in H2 at - 2}. In particular a failure will happen if any of + these three simpler tactics fails. + \item \texttt{rewrite H in * |- } will do \texttt{rewrite H in + H$_i$} for all hypothesis \texttt{H$_i$ <> H}. A success will happen + as soon as at least one of these simpler tactics succeeds. + \item \texttt{rewrite H in *} is a combination of \texttt{rewrite H} + and \texttt{rewrite H in * |-} that succeeds if at + least one of these two tactics succeeds. + \end{itemize} + Orientation {\tt ->} or {\tt <-} can be + inserted before the term to rewrite. + +\item {\tt rewrite {\term} at {\occlist}} + \tacindex{rewrite \dots\ at} + + Rewrite only the given occurrences of \term$_1'$. Occurrences are + specified from left to right as for \texttt{pattern} (\S + \ref{pattern}). The rewrite is always performed using setoid + rewriting, even for Leibniz's equality, so one has to + \texttt{Import Setoid} to use this variant. + +\item {\tt rewrite {\term} by {\tac}} + \tacindex{rewrite \dots\ by} + + Use {\tac} to completely solve the side-conditions arising from the + rewrite. + +\item {\tt rewrite} $\term_1${\tt ,} {\ldots}{\tt ,} $\term_n$\\ + Is equivalent to the $n$ successive tactics {\tt rewrite $\term_1$} + up to {\tt rewrite $\term_n$}, each one working on the first subgoal + generated by the previous one. + Orientation {\tt ->} or {\tt <-} can be + inserted before each term to rewrite. One unique \textit{clause} + can be added at the end after the keyword {\tt in}; it will + then affect all rewrite operations. + +\item In all forms of {\tt rewrite} described above, a term to rewrite + can be immediately prefixed by one of the following modifiers: + \begin{itemize} + \item {\tt ?} : the tactic {\tt rewrite ?$\term$} performs the + rewrite of $\term$ as many times as possible (perhaps zero time). + This form never fails. + \item {\tt $n$?} : works similarly, except that it will do at most + $n$ rewrites. + \item {\tt !} : works as {\tt ?}, except that at least one rewrite + should succeed, otherwise the tactic fails. + \item {\tt $n$!} (or simply {\tt $n$}) : precisely $n$ rewrites + of $\term$ will be done, leading to failure if these $n$ rewrites are not possible. + \end{itemize} + +\item {\tt erewrite {\term}\tacindex{erewrite}} + +This tactic works as {\tt rewrite {\term}} but turning unresolved +bindings into existential variables, if any, instead of failing. It has +the same variants as {\tt rewrite} has. + +\end{Variants} + + +\subsection{\tt cutrewrite -> \term$_1$ = \term$_2$ +\label{cutrewrite} +\tacindex{cutrewrite}} + +This tactic acts like {\tt replace {\term$_1$} with {\term$_2$}} +(see below). + +\subsection{\tt replace {\term$_1$} with {\term$_2$} +\label{tactic:replace} +\tacindex{replace \dots\ with}} + +This tactic applies to any goal. It replaces all free occurrences of +{\term$_1$} in the current goal with {\term$_2$} and generates the +equality {\term$_2$}{\tt =}{\term$_1$} as a subgoal. This equality is +automatically solved if it occurs amongst the assumption, or if its +symmetric form occurs. It is equivalent to {\tt cut +\term$_2$=\term$_1$; [intro H{\sl n}; rewrite <- H{\sl n}; clear H{\sl +n}| assumption || symmetry; try assumption]}. + +\begin{ErrMsgs} +\item \errindex{terms do not have convertible types} +\end{ErrMsgs} + +\begin{Variants} +\item {\tt replace {\term$_1$} with {\term$_2$} by \tac}\\ This acts + as {\tt replace {\term$_1$} with {\term$_2$}} but applies {\tt \tac} + to solve the generated subgoal {\tt \term$_2$=\term$_1$}. +\item {\tt replace {\term}}\\ Replace {\term} with {\term'} using the + first assumption whose type has the form {\tt \term=\term'} or {\tt + \term'=\term} +\item {\tt replace -> {\term}}\\ Replace {\term} with {\term'} using the + first assumption whose type has the form {\tt \term=\term'} +\item {\tt replace <- {\term}}\\ Replace {\term} with {\term'} using the + first assumption whose type has the form {\tt \term'=\term} +\item {\tt replace {\term$_1$} with {\term$_2$} \textit{clause} }\\ + {\tt replace {\term$_1$} with {\term$_2$} \textit{clause} by \tac }\\ + {\tt replace {\term} \textit{clause}}\\ + {\tt replace -> {\term} \textit{clause}}\\ + {\tt replace <- {\term} \textit{clause}}\\ + Act as before but the replacements take place in + \textit{clause}~(see Section~\ref{Conversion-tactics}) and not only + in the conclusion of the goal.\\ + The \textit{clause} argument must not contain any \texttt{type of} nor \texttt{value of}. +\end{Variants} + +\subsection{\tt reflexivity +\label{reflexivity} +\tacindex{reflexivity}} + +This tactic applies to a goal which has the form {\tt t=u}. It checks +that {\tt t} and {\tt u} are convertible and then solves the goal. +It is equivalent to {\tt apply refl\_equal}. + +\begin{ErrMsgs} +\item \errindex{The conclusion is not a substitutive equation} +\item \errindex{Impossible to unify \dots\ with \dots} +\end{ErrMsgs} + +\subsection{\tt symmetry +\tacindex{symmetry} +\tacindex{symmetry in}} +This tactic applies to a goal which has the form {\tt t=u} and changes it +into {\tt u=t}. + +\variant {\tt symmetry in {\ident}}\\ +If the statement of the hypothesis {\ident} has the form {\tt t=u}, +the tactic changes it to {\tt u=t}. + +\subsection{\tt transitivity \term +\tacindex{transitivity}} +This tactic applies to a goal which has the form {\tt t=u} +and transforms it into the two subgoals +{\tt t={\term}} and {\tt {\term}=u}. + +\subsection{\tt subst {\ident} +\tacindex{subst}} + +This tactic applies to a goal which has \ident\ in its context and +(at least) one hypothesis, say {\tt H}, of type {\tt + \ident=t} or {\tt t=\ident}. Then it replaces +\ident\ by {\tt t} everywhere in the goal (in the hypotheses +and in the conclusion) and clears \ident\ and {\tt H} from the context. + +\Rem +When several hypotheses have the form {\tt \ident=t} or {\tt + t=\ident}, the first one is used. + +\begin{Variants} + \item {\tt subst \ident$_1$ \dots \ident$_n$} \\ + Is equivalent to {\tt subst \ident$_1$; \dots; subst \ident$_n$}. + \item {\tt subst} \\ + Applies {\tt subst} repeatedly to all identifiers from the context + for which an equality exists. +\end{Variants} + +\subsection[{\tt stepl {\term}}]{{\tt stepl {\term}}\tacindex{stepl}} + +This tactic is for chaining rewriting steps. It assumes a goal of the +form ``$R$ {\term}$_1$ {\term}$_2$'' where $R$ is a binary relation +and relies on a database of lemmas of the form {\tt forall} $x$ $y$ +$z$, $R$ $x$ $y$ {\tt ->} $eq$ $x$ $z$ {\tt ->} $R$ $z$ $y$ where $eq$ +is typically a setoid equality. The application of {\tt stepl {\term}} +then replaces the goal by ``$R$ {\term} {\term}$_2$'' and adds a new +goal stating ``$eq$ {\term} {\term}$_1$''. + +Lemmas are added to the database using the command +\comindex{Declare Left Step} +\begin{quote} +{\tt Declare Left Step {\term}.} +\end{quote} + +The tactic is especially useful for parametric setoids which are not +accepted as regular setoids for {\tt rewrite} and {\tt + setoid\_replace} (see Chapter~\ref{setoid_replace}). + +\tacindex{stepr} +\comindex{Declare Right Step} +\begin{Variants} +\item{\tt stepl {\term} by {\tac}}\\ +This applies {\tt stepl {\term}} then applies {\tac} to the second goal. + +\item{\tt stepr {\term}}\\ + {\tt stepr {\term} by {\tac}}\\ +This behaves as {\tt stepl} but on the right-hand-side of the binary relation. +Lemmas are expected to be of the form +``{\tt forall} $x$ $y$ +$z$, $R$ $x$ $y$ {\tt ->} $eq$ $y$ $z$ {\tt ->} $R$ $x$ $z$'' +and are registered using the command +\begin{quote} +{\tt Declare Right Step {\term}.} +\end{quote} +\end{Variants} + +\subsection{\tt change \term +\tacindex{change} +\label{change}} + +This tactic applies to any goal. It implements the rule +``Conv''\index{Typing rules!Conv} given in Section~\ref{Conv}. {\tt + change U} replaces the current goal \T\ with \U\ providing that +\U\ is well-formed and that \T\ and \U\ are convertible. + +\begin{ErrMsgs} +\item \errindex{Not convertible} +\end{ErrMsgs} + +\tacindex{change \dots\ in} +\begin{Variants} +\item {\tt change \term$_1$ with \term$_2$} + + This replaces the occurrences of \term$_1$ by \term$_2$ in the + current goal. The terms \term$_1$ and \term$_2$ must be + convertible. + +\item {\tt change \term$_1$ at \num$_1$ \dots\ \num$_i$ with \term$_2$} + + This replaces the occurrences numbered \num$_1$ \dots\ \num$_i$ of + \term$_1$ by \term$_2$ in the current goal. + The terms \term$_1$ and \term$_2$ must be convertible. + + \ErrMsg {\tt Too few occurrences} + +\item {\tt change {\term} in {\ident}} + +\item {\tt change \term$_1$ with \term$_2$ in {\ident}} + +\item {\tt change \term$_1$ at \num$_1$ \dots\ \num$_i$ with \term$_2$ in + {\ident}} + + This applies the {\tt change} tactic not to the goal but to the + hypothesis {\ident}. + +\end{Variants} + +\SeeAlso \ref{Conversion-tactics} + + +\section{Performing computations +\index{Conversion tactics} +\label{Conversion-tactics}} + +This set of tactics implements different specialized usages of the +tactic \texttt{change}. + +All conversion tactics (including \texttt{change}) can be +parameterized by the parts of the goal where the conversion can +occur. This is done using \emph{goal clauses} which consists in a list +of hypotheses and, optionally, of a reference to the conclusion of the +goal. For defined hypothesis it is possible to specify if the +conversion should occur on the type part, the body part or both +(default). + +\index{Clauses} +\index{Goal clauses} +Goal clauses are written after a conversion tactic (tactics +\texttt{set}~\ref{tactic:set}, \texttt{rewrite}~\ref{rewrite}, +\texttt{replace}~\ref{tactic:replace} and +\texttt{autorewrite}~\ref{tactic:autorewrite} also use goal clauses) and +are introduced by the keyword \texttt{in}. If no goal clause is provided, +the default is to perform the conversion only in the conclusion. + +The syntax and description of the various goal clauses is the following: +\begin{description} +\item[]\texttt{in {\ident}$_1$ $\ldots$ {\ident}$_n$ |- } only in hypotheses {\ident}$_1$ + \ldots {\ident}$_n$ +\item[]\texttt{in {\ident}$_1$ $\ldots$ {\ident}$_n$ |- *} in hypotheses {\ident}$_1$ \ldots + {\ident}$_n$ and in the conclusion +\item[]\texttt{in * |-} in every hypothesis +\item[]\texttt{in *} (equivalent to \texttt{in * |- *}) everywhere +\item[]\texttt{in (type of {\ident}$_1$) (value of {\ident}$_2$) $\ldots$ |-} in + type part of {\ident}$_1$, in the value part of {\ident}$_2$, etc. +\end{description} + +For backward compatibility, the notation \texttt{in}~{\ident}$_1$\ldots {\ident}$_n$ +performs the conversion in hypotheses {\ident}$_1$\ldots {\ident}$_n$. + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%voir reduction__conv_x : histoires d'univers. +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% + +\subsection[{\tt cbv \flag$_1$ \dots\ \flag$_n$}, {\tt lazy \flag$_1$ +\dots\ \flag$_n$} and {\tt compute}] +{{\tt cbv \flag$_1$ \dots\ \flag$_n$}, {\tt lazy \flag$_1$ +\dots\ \flag$_n$} and {\tt compute} +\tacindex{cbv} +\tacindex{lazy} +\tacindex{compute} +\tacindex{vm\_compute}\label{vmcompute}} + +These parameterized reduction tactics apply to any goal and perform +the normalization of the goal according to the specified flags. In +correspondence with the kinds of reduction considered in \Coq\, namely +$\beta$ (reduction of functional application), $\delta$ (unfolding of +transparent constants, see \ref{Transparent}), $\iota$ (reduction of +pattern-matching over a constructed term, and unfolding of {\tt fix} +and {\tt cofix} expressions) and $\zeta$ (contraction of local +definitions), the flag are either {\tt beta}, {\tt delta}, {\tt iota} +or {\tt zeta}. The {\tt delta} flag itself can be refined into {\tt +delta [\qualid$_1$\ldots\qualid$_k$]} or {\tt delta +-[\qualid$_1$\ldots\qualid$_k$]}, restricting in the first case the +constants to unfold to the constants listed, and restricting in the +second case the constant to unfold to all but the ones explicitly +mentioned. Notice that the {\tt delta} flag does not apply to +variables bound by a let-in construction inside the term itself (use +here the {\tt zeta} flag). In any cases, opaque constants are not +unfolded (see Section~\ref{Opaque}). + +The goal may be normalized with two strategies: {\em lazy} ({\tt lazy} +tactic), or {\em call-by-value} ({\tt cbv} tactic). The lazy strategy +is a call-by-need strategy, with sharing of reductions: the arguments of a +function call are partially evaluated only when necessary, and if an +argument is used several times then it is computed only once. This +reduction is efficient for reducing expressions with dead code. For +instance, the proofs of a proposition {\tt exists~$x$. $P(x)$} reduce to a +pair of a witness $t$, and a proof that $t$ satisfies the predicate +$P$. Most of the time, $t$ may be computed without computing the proof +of $P(t)$, thanks to the lazy strategy. + +The call-by-value strategy is the one used in ML languages: the +arguments of a function call are evaluated first, using a weak +reduction (no reduction under the $\lambda$-abstractions). Despite the +lazy strategy always performs fewer reductions than the call-by-value +strategy, the latter is generally more efficient for evaluating purely +computational expressions (i.e. with few dead code). + +\begin{Variants} +\item {\tt compute} \tacindex{compute}\\ + {\tt cbv} + + These are synonyms for {\tt cbv beta delta iota zeta}. + +\item {\tt lazy} + + This is a synonym for {\tt lazy beta delta iota zeta}. + +\item {\tt compute [\qualid$_1$\ldots\qualid$_k$]}\\ + {\tt cbv [\qualid$_1$\ldots\qualid$_k$]} + + These are synonyms of {\tt cbv beta delta + [\qualid$_1$\ldots\qualid$_k$] iota zeta}. + +\item {\tt compute -[\qualid$_1$\ldots\qualid$_k$]}\\ + {\tt cbv -[\qualid$_1$\ldots\qualid$_k$]} + + These are synonyms of {\tt cbv beta delta + -[\qualid$_1$\ldots\qualid$_k$] iota zeta}. + +\item {\tt lazy [\qualid$_1$\ldots\qualid$_k$]}\\ + {\tt lazy -[\qualid$_1$\ldots\qualid$_k$]} + + These are respectively synonyms of {\tt lazy beta delta + [\qualid$_1$\ldots\qualid$_k$] iota zeta} and {\tt lazy beta delta + -[\qualid$_1$\ldots\qualid$_k$] iota zeta}. + +\item {\tt vm\_compute} \tacindex{vm\_compute} + + This tactic evaluates the goal using the optimized call-by-value + evaluation bytecode-based virtual machine. This algorithm is + dramatically more efficient than the algorithm used for the {\tt + cbv} tactic, but it cannot be fine-tuned. It is specially + interesting for full evaluation of algebraic objects. This includes + the case of reflexion-based tactics. + +\end{Variants} + +% Obsolete? Anyway not very important message +%\begin{ErrMsgs} +%\item \errindex{Delta must be specified before} +% +% A list of constants appeared before the {\tt delta} flag. +%\end{ErrMsgs} + + +\subsection{{\tt red} +\tacindex{red}} + +This tactic applies to a goal which has the form {\tt + forall (x:T1)\dots(xk:Tk), c t1 \dots\ tn} where {\tt c} is a constant. If +{\tt c} is transparent then it replaces {\tt c} with its definition +(say {\tt t}) and then reduces {\tt (t t1 \dots\ tn)} according to +$\beta\iota\zeta$-reduction rules. + +\begin{ErrMsgs} +\item \errindex{Not reducible} +\end{ErrMsgs} + +\subsection{{\tt hnf} +\tacindex{hnf}} + +This tactic applies to any goal. It replaces the current goal with its +head normal form according to the $\beta\delta\iota\zeta$-reduction +rules, i.e. it reduces the head of the goal until it becomes a +product or an irreducible term. + +\Example +The term \verb+forall n:nat, (plus (S n) (S n))+ is not reduced by {\tt hnf}. + +\Rem The $\delta$ rule only applies to transparent constants +(see Section~\ref{Opaque} on transparency and opacity). + +\subsection{\tt simpl +\tacindex{simpl}} + +This tactic applies to any goal. The tactic {\tt simpl} first applies +$\beta\iota$-reduction rule. Then it expands transparent constants +and tries to reduce {\tt T'} according, once more, to $\beta\iota$ +rules. But when the $\iota$ rule is not applicable then possible +$\delta$-reductions are not applied. For instance trying to use {\tt +simpl} on {\tt (plus n O)=n} changes nothing. Notice that only +transparent constants whose name can be reused as such in the +recursive calls are possibly unfolded. For instance a constant defined +by {\tt plus' := plus} is possibly unfolded and reused in the +recursive calls, but a constant such as {\tt succ := plus (S O)} is +never unfolded. + +The behavior of {\tt simpl} can be tuned using the {\tt Arguments} vernacular +command as follows: +\comindex{Arguments} +\begin{itemize} +\item +A constant can be marked to be never unfolded by {\tt simpl}: +\begin{coq_example*} +Arguments minus x y : simpl never +\end{coq_example*} +After that command an expression like {\tt (minus (S x) y)} is left untouched by +the {\tt simpl} tactic. +\item +A constant can be marked to be unfolded only if applied to enough arguments. +The number of arguments required can be specified using +the {\tt /} symbol in the arguments list of the {\tt Arguments} vernacular +command. +\begin{coq_example*} +Definition fcomp A B C f (g : A -> B) (x : A) : C := f (g x). +Notation "f \o g" := (fcomp f g) (at level 50). +Arguments fcomp {A B C} f g x /. +\end{coq_example*} +After that command the expression {\tt (f \verb+\+o g)} is left untouched by +{\tt simpl} while {\tt ((f \verb+\+o g) t)} is reduced to {\tt (f (g t))}. +The same mechanism can be used to make a constant volatile, i.e. always +unfolded by {\tt simpl}. +\begin{coq_example*} +Definition volatile := fun x : nat => x. +Arguments volatile / x. +\end{coq_example*} +\item +A constant can be marked to be unfolded only if an entire set of arguments +evaluates to a constructor. The {\tt !} symbol can be used to mark such +arguments. +\begin{coq_example*} +Arguments minus !x !y. +\end{coq_example*} +After that command, the expression {\tt (minus (S x) y)} is left untouched by +{\tt simpl}, while {\tt (minus (S x) (S y))} is reduced to {\tt (minus x y)}. +\item +A special heuristic to determine if a constant has to be unfolded can be +activated with the following command: +\begin{coq_example*} +Arguments minus x y : simpl nomatch +\end{coq_example*} +The heuristic avoids to perform a simplification step that would +expose a {\tt match} construct in head position. For example the +expression {\tt (minus (S (S x)) (S y))} is simplified to +{\tt (minus (S x) y)} even if an extra simplification is possible. +\end{itemize} + +\tacindex{simpl \dots\ in} +\begin{Variants} +\item {\tt simpl {\term}} + + This applies {\tt simpl} only to the occurrences of {\term} in the + current goal. + +\item {\tt simpl {\term} at \num$_1$ \dots\ \num$_i$} + + This applies {\tt simpl} only to the \num$_1$, \dots, \num$_i$ + occurrences of {\term} in the current goal. + + \ErrMsg {\tt Too few occurrences} + +\item {\tt simpl {\ident}} + + This applies {\tt simpl} only to the applicative subterms whose head + occurrence is {\ident}. + +\item {\tt simpl {\ident} at \num$_1$ \dots\ \num$_i$} + + This applies {\tt simpl} only to the \num$_1$, \dots, \num$_i$ +applicative subterms whose head occurrence is {\ident}. + +\end{Variants} + +\subsection{\tt unfold \qualid +\tacindex{unfold} +\label{unfold}} + +This tactic applies to any goal. The argument {\qualid} must denote a +defined transparent constant or local definition (see Sections~\ref{Basic-definitions} and~\ref{Transparent}). The tactic {\tt + unfold} applies the $\delta$ rule to each occurrence of the constant +to which {\qualid} refers in the current goal and then replaces it +with its $\beta\iota$-normal form. + +\begin{ErrMsgs} +\item {\qualid} \errindex{does not denote an evaluable constant} + +\end{ErrMsgs} + +\begin{Variants} +\item {\tt unfold {\qualid}$_1$, \dots, \qualid$_n$} + \tacindex{unfold \dots\ in} + + Replaces {\em simultaneously} {\qualid}$_1$, \dots, {\qualid}$_n$ + with their definitions and replaces the current goal with its + $\beta\iota$ normal form. + +\item {\tt unfold {\qualid}$_1$ at \num$_1^1$, \dots, \num$_i^1$, +\dots,\ \qualid$_n$ at \num$_1^n$ \dots\ \num$_j^n$} + + The lists \num$_1^1$, \dots, \num$_i^1$ and \num$_1^n$, \dots, + \num$_j^n$ specify the occurrences of {\qualid}$_1$, \dots, + \qualid$_n$ to be unfolded. Occurrences are located from left to + right. + + \ErrMsg {\tt bad occurrence number of {\qualid}$_i$} + + \ErrMsg {\qualid}$_i$ {\tt does not occur} + +\item {\tt unfold {\qstring}} + + If {\qstring} denotes the discriminating symbol of a notation (e.g. {\tt + "+"}) or an expression defining a notation (e.g. \verb!"_ + _"!), and + this notation refers to an unfoldable constant, then the tactic + unfolds it. + +\item {\tt unfold {\qstring}\%{\delimkey}} + + This is variant of {\tt unfold {\qstring}} where {\qstring} gets its + interpretation from the scope bound to the delimiting key + {\delimkey} instead of its default interpretation (see + Section~\ref{scopechange}). + +\item {\tt unfold \qualidorstring$_1$ at \num$_1^1$, \dots, \num$_i^1$, +\dots,\ \qualidorstring$_n$ at \num$_1^n$ \dots\ \num$_j^n$} + + This is the most general form, where {\qualidorstring} is either a + {\qualid} or a {\qstring} referring to a notation. + +\end{Variants} -\texttt{forall (x$_1$:A$_1$) \dots\ (x$_n$:A$_n$)}\texttt{eq} \term$_1$ \term$_2$. +\subsection{{\tt fold} \term +\tacindex{fold}} -\noindent where \texttt{eq} is the Leibniz equality or a registered -setoid equality. +This tactic applies to any goal. The term \term\ is reduced using the {\tt red} +tactic. Every occurrence of the resulting term in the goal is then +replaced by \term. -\noindent Then {\tt rewrite \term} finds the first subterm matching -\term$_1$ in the goal, resulting in instances \term$_1'$ and \term$_2'$ -and then replaces every occurrence of \term$_1'$ by \term$_2'$. -Hence, some of the variables x$_i$ are -solved by unification, and some of the types \texttt{A}$_1$, \dots, -\texttt{A}$_n$ become new subgoals. +\begin{Variants} +\item {\tt fold} \term$_1$ \dots\ \term$_n$ -% \Rem In case the type of -% \term$_1$ contains occurrences of variables bound in the -% type of \term, the tactic tries first to find a subterm of the goal -% which matches this term in order to find a closed instance \term$'_1$ -% of \term$_1$, and then all instances of \term$'_1$ will be replaced. + Equivalent to {\tt fold} \term$_1${\tt;}\ldots{\tt; fold} \term$_n$. +\end{Variants} -\begin{ErrMsgs} -\item \errindex{The term provided does not end with an equation} +\subsection{{\tt pattern {\term}} +\tacindex{pattern} +\label{pattern}} -\item \errindex{Tactic generated a subgoal identical to the original goal}\\ -This happens if \term$_1$ does not occur in the goal. -\end{ErrMsgs} +This command applies to any goal. The argument {\term} must be a free +subterm of the current goal. The command {\tt pattern} performs +$\beta$-expansion (the inverse of $\bt$-reduction) of the current goal +(say \T) by +\begin{enumerate} +\item replacing all occurrences of {\term} in {\T} with a fresh variable +\item abstracting this variable +\item applying the abstracted goal to {\term} +\end{enumerate} -\begin{Variants} -\item {\tt rewrite -> {\term}}\tacindex{rewrite ->}\\ - Is equivalent to {\tt rewrite \term} +For instance, if the current goal $T$ is expressible has $\phi(t)$ +where the notation captures all the instances of $t$ in $\phi(t)$, +then {\tt pattern $t$} transforms it into {\tt (fun x:$A$ => $\phi(${\tt +x}$)$) $t$}. This command can be used, for instance, when the tactic +{\tt apply} fails on matching. -\item {\tt rewrite <- {\term}}\tacindex{rewrite <-}\\ - Uses the equality \term$_1${\tt=}\term$_2$ from right to left +\begin{Variants} +\item {\tt pattern {\term} at {\num$_1$} \dots\ {\num$_n$}} -\item {\tt rewrite {\term} in \textit{clause}} - \tacindex{rewrite \dots\ in}\\ - Analogous to {\tt rewrite {\term}} but rewriting is done following - \textit{clause} (similarly to \ref{Conversion-tactics}). For - instance: - \begin{itemize} - \item \texttt{rewrite H in H1} will rewrite \texttt{H} in the hypothesis - \texttt{H1} instead of the current goal. - \item \texttt{rewrite H in H1 at 1, H2 at - 2 |- *} means \texttt{rewrite H; rewrite H in H1 at 1; - rewrite H in H2 at - 2}. In particular a failure will happen if any of - these three simpler tactics fails. - \item \texttt{rewrite H in * |- } will do \texttt{rewrite H in - H$_i$} for all hypothesis \texttt{H$_i$ <> H}. A success will happen - as soon as at least one of these simpler tactics succeeds. - \item \texttt{rewrite H in *} is a combination of \texttt{rewrite H} - and \texttt{rewrite H in * |-} that succeeds if at - least one of these two tactics succeeds. - \end{itemize} - Orientation {\tt ->} or {\tt <-} can be - inserted before the term to rewrite. + Only the occurrences {\num$_1$} \dots\ {\num$_n$} of {\term} are + considered for $\beta$-expansion. Occurrences are located from left + to right. -\item {\tt rewrite {\term} at {\occlist}} - \tacindex{rewrite \dots\ at} +\item {\tt pattern {\term} at - {\num$_1$} \dots\ {\num$_n$}} - Rewrite only the given occurrences of \term$_1'$. Occurrences are - specified from left to right as for \texttt{pattern} (\S - \ref{pattern}). The rewrite is always performed using setoid - rewriting, even for Leibniz's equality, so one has to - \texttt{Import Setoid} to use this variant. + All occurrences except the occurrences of indexes {\num$_1$} \dots\ + {\num$_n$} of {\term} are considered for + $\beta$-expansion. Occurrences are located from left to right. -\item {\tt rewrite {\term} by {\tac}} - \tacindex{rewrite \dots\ by} +\item {\tt pattern {\term$_1$}, \dots, {\term$_m$}} - Use {\tac} to completely solve the side-conditions arising from the - rewrite. + Starting from a goal $\phi(t_1 \dots\ t_m)$, the tactic + {\tt pattern $t_1$, \dots,\ $t_m$} generates the equivalent goal {\tt + (fun (x$_1$:$A_1$) \dots\ (x$_m$:$A_m$) => $\phi(${\tt x$_1$\dots\ + x$_m$}$)$) $t_1$ \dots\ $t_m$}.\\ If $t_i$ occurs in one of the + generated types $A_j$ these occurrences will also be considered and + possibly abstracted. -\item {\tt rewrite} $\term_1${\tt ,} {\ldots}{\tt ,} $\term_n$\\ - Is equivalent to the $n$ successive tactics {\tt rewrite $\term_1$} - up to {\tt rewrite $\term_n$}, each one working on the first subgoal - generated by the previous one. - Orientation {\tt ->} or {\tt <-} can be - inserted before each term to rewrite. One unique \textit{clause} - can be added at the end after the keyword {\tt in}; it will - then affect all rewrite operations. +\item {\tt pattern {\term$_1$} at {\num$_1^1$} \dots\ {\num$_{n_1}^1$}, \dots, + {\term$_m$} at {\num$_1^m$} \dots\ {\num$_{n_m}^m$}} -\item In all forms of {\tt rewrite} described above, a term to rewrite - can be immediately prefixed by one of the following modifiers: - \begin{itemize} - \item {\tt ?} : the tactic {\tt rewrite ?$\term$} performs the - rewrite of $\term$ as many times as possible (perhaps zero time). - This form never fails. - \item {\tt $n$?} : works similarly, except that it will do at most - $n$ rewrites. - \item {\tt !} : works as {\tt ?}, except that at least one rewrite - should succeed, otherwise the tactic fails. - \item {\tt $n$!} (or simply {\tt $n$}) : precisely $n$ rewrites - of $\term$ will be done, leading to failure if these $n$ rewrites are not possible. - \end{itemize} + This behaves as above but processing only the occurrences \num$_1^1$, + \dots, \num$_i^1$ of \term$_1$, \dots, \num$_1^m$, \dots, \num$_j^m$ + of \term$_m$ starting from \term$_m$. -\item {\tt erewrite {\term}\tacindex{erewrite}} +\item {\tt pattern} {\term$_1$} \zeroone{{\tt at \zeroone{-}} {\num$_1^1$} \dots\ {\num$_{n_1}^1$}} {\tt ,} \dots {\tt ,} + {\term$_m$} \zeroone{{\tt at \zeroone{-}} {\num$_1^m$} \dots\ {\num$_{n_m}^m$}} -This tactic works as {\tt rewrite {\term}} but turning unresolved -bindings into existential variables, if any, instead of failing. It has -the same variants as {\tt rewrite} has. + This is the most general syntax that combines the different variants. \end{Variants} +\subsection{Conversion tactics applied to hypotheses} -\subsection{\tt cutrewrite -> \term$_1$ = \term$_2$ -\label{cutrewrite} -\tacindex{cutrewrite}} - -This tactic acts like {\tt replace {\term$_1$} with {\term$_2$}} -(see below). +{\convtactic} {\tt in} \ident$_1$ \dots\ \ident$_n$ -\subsection{\tt replace {\term$_1$} with {\term$_2$} -\label{tactic:replace} -\tacindex{replace \dots\ with}} +Applies the conversion tactic {\convtactic} to the +hypotheses \ident$_1$, \ldots, \ident$_n$. The tactic {\convtactic} is +any of the conversion tactics listed in this section. -This tactic applies to any goal. It replaces all free occurrences of -{\term$_1$} in the current goal with {\term$_2$} and generates the -equality {\term$_2$}{\tt =}{\term$_1$} as a subgoal. This equality is -automatically solved if it occurs amongst the assumption, or if its -symmetric form occurs. It is equivalent to {\tt cut -\term$_2$=\term$_1$; [intro H{\sl n}; rewrite <- H{\sl n}; clear H{\sl -n}| assumption || symmetry; try assumption]}. +If \ident$_i$ is a local definition, then \ident$_i$ can be replaced +by (Type of \ident$_i$) to address not the body but the type of the +local definition. Example: {\tt unfold not in (Type of H1) (Type of H3).} \begin{ErrMsgs} -\item \errindex{terms do not have convertible types} +\item \errindex{No such hypothesis} : {\ident}. \end{ErrMsgs} -\begin{Variants} -\item {\tt replace {\term$_1$} with {\term$_2$} by \tac}\\ This acts - as {\tt replace {\term$_1$} with {\term$_2$}} but applies {\tt \tac} - to solve the generated subgoal {\tt \term$_2$=\term$_1$}. -\item {\tt replace {\term}}\\ Replace {\term} with {\term'} using the - first assumption whose type has the form {\tt \term=\term'} or {\tt - \term'=\term} -\item {\tt replace -> {\term}}\\ Replace {\term} with {\term'} using the - first assumption whose type has the form {\tt \term=\term'} -\item {\tt replace <- {\term}}\\ Replace {\term} with {\term'} using the - first assumption whose type has the form {\tt \term'=\term} -\item {\tt replace {\term$_1$} with {\term$_2$} \textit{clause} }\\ - {\tt replace {\term$_1$} with {\term$_2$} \textit{clause} by \tac }\\ - {\tt replace {\term} \textit{clause}}\\ - {\tt replace -> {\term} \textit{clause}}\\ - {\tt replace <- {\term} \textit{clause}}\\ - Act as before but the replacements take place in - \textit{clause}~(see Section~\ref{Conversion-tactics}) and not only - in the conclusion of the goal.\\ - The \textit{clause} argument must not contain any \texttt{type of} nor \texttt{value of}. -\end{Variants} -\subsection{\tt reflexivity -\label{reflexivity} -\tacindex{reflexivity}} +\section{Automation} +\subsection{\tt auto +\label{auto} +\tacindex{auto}} -This tactic applies to a goal which has the form {\tt t=u}. It checks -that {\tt t} and {\tt u} are convertible and then solves the goal. -It is equivalent to {\tt apply refl\_equal}. +This tactic implements a Prolog-like resolution procedure to solve the +current goal. It first tries to solve the goal using the {\tt + assumption} tactic, then it reduces the goal to an atomic one using +{\tt intros} and introducing the newly generated hypotheses as hints. +Then it looks at the list of tactics associated to the head symbol of +the goal and tries to apply one of them (starting from the tactics +with lower cost). This process is recursively applied to the generated +subgoals. -\begin{ErrMsgs} -\item \errindex{The conclusion is not a substitutive equation} -\item \errindex{Impossible to unify \dots\ with \dots} -\end{ErrMsgs} +By default, \texttt{auto} only uses the hypotheses of the current goal and the +hints of the database named {\tt core}. -\subsection{\tt symmetry -\tacindex{symmetry} -\tacindex{symmetry in}} -This tactic applies to a goal which has the form {\tt t=u} and changes it -into {\tt u=t}. +\begin{Variants} -\variant {\tt symmetry in {\ident}}\\ -If the statement of the hypothesis {\ident} has the form {\tt t=u}, -the tactic changes it to {\tt u=t}. +\item {\tt auto \num} -\subsection{\tt transitivity \term -\tacindex{transitivity}} -This tactic applies to a goal which has the form {\tt t=u} -and transforms it into the two subgoals -{\tt t={\term}} and {\tt {\term}=u}. + Forces the search depth to be \num. The maximal search depth is 5 by + default. -\subsection{\tt subst {\ident} -\tacindex{subst}} +\item {\tt auto with \ident$_1$ \dots\ \ident$_n$} -This tactic applies to a goal which has \ident\ in its context and -(at least) one hypothesis, say {\tt H}, of type {\tt - \ident=t} or {\tt t=\ident}. Then it replaces -\ident\ by {\tt t} everywhere in the goal (in the hypotheses -and in the conclusion) and clears \ident\ and {\tt H} from the context. + Uses the hint databases $\ident_1$ \dots\ $\ident_n$ in addition to + the database {\tt core}. See Section~\ref{Hints-databases} for the + list of pre-defined databases and the way to create or extend a + database. This option can be combined with the previous one. -\Rem -When several hypotheses have the form {\tt \ident=t} or {\tt - t=\ident}, the first one is used. +\item {\tt auto with *} -\begin{Variants} - \item {\tt subst \ident$_1$ \dots \ident$_n$} \\ - Is equivalent to {\tt subst \ident$_1$; \dots; subst \ident$_n$}. - \item {\tt subst} \\ - Applies {\tt subst} repeatedly to all identifiers from the context - for which an equality exists. -\end{Variants} + Uses all existing hint databases, minus the special database + {\tt v62}. See Section~\ref{Hints-databases} -\subsection[{\tt stepl {\term}}]{{\tt stepl {\term}}\tacindex{stepl}} +\item \texttt{auto using} \nterm{lemma}$_1$ {\tt ,} {\ldots} {\tt ,} \nterm{lemma}$_n$ -This tactic is for chaining rewriting steps. It assumes a goal of the -form ``$R$ {\term}$_1$ {\term}$_2$'' where $R$ is a binary relation -and relies on a database of lemmas of the form {\tt forall} $x$ $y$ -$z$, $R$ $x$ $y$ {\tt ->} $eq$ $x$ $z$ {\tt ->} $R$ $z$ $y$ where $eq$ -is typically a setoid equality. The application of {\tt stepl {\term}} -then replaces the goal by ``$R$ {\term} {\term}$_2$'' and adds a new -goal stating ``$eq$ {\term} {\term}$_1$''. + Uses \nterm{lemma}$_1$, \ldots, \nterm{lemma}$_n$ in addition to + hints (can be combined with the \texttt{with \ident} option). If + $lemma_i$ is an inductive type, it is the collection of its + constructors which is added as hints. -Lemmas are added to the database using the command -\comindex{Declare Left Step} -\begin{quote} -{\tt Declare Left Step {\term}.} -\end{quote} +\item \texttt{auto using} \nterm{lemma}$_1$ {\tt ,} {\ldots} {\tt ,} \nterm{lemma}$_n$ with \ident$_1$ {\ldots} \ident$_n$ -The tactic is especially useful for parametric setoids which are not -accepted as regular setoids for {\tt rewrite} and {\tt - setoid\_replace} (see Chapter~\ref{setoid_replace}). + This combines the effects of the {\tt using} and {\tt with} options. -\tacindex{stepr} -\comindex{Declare Right Step} -\begin{Variants} -\item{\tt stepl {\term} by {\tac}}\\ -This applies {\tt stepl {\term}} then applies {\tac} to the second goal. +\item {\tt trivial}\tacindex{trivial} + + This tactic is a restriction of {\tt auto} that is not recursive and + tries only hints which cost 0. Typically it solves trivial + equalities like $X=X$. + +\item \texttt{trivial with \ident$_1$ \dots\ \ident$_n$} + +\item \texttt{trivial with *} -\item{\tt stepr {\term}}\\ - {\tt stepr {\term} by {\tac}}\\ -This behaves as {\tt stepl} but on the right-hand-side of the binary relation. -Lemmas are expected to be of the form -``{\tt forall} $x$ $y$ -$z$, $R$ $x$ $y$ {\tt ->} $eq$ $y$ $z$ {\tt ->} $R$ $x$ $z$'' -and are registered using the command -\begin{quote} -{\tt Declare Right Step {\term}.} -\end{quote} \end{Variants} +\Rem {\tt auto} either solves completely the goal or else leaves it +intact. \texttt{auto} and \texttt{trivial} never fail. + +\SeeAlso Section~\ref{Hints-databases} + +\subsection{\tt eauto +\tacindex{eauto} +\label{eauto}} + +This tactic generalizes {\tt auto}. In contrast with +the latter, {\tt eauto} uses unification of the goal +against the hints rather than pattern-matching +(in other words, it uses {\tt eapply} instead of +{\tt apply}). +As a consequence, {\tt eauto} can solve such a goal: -\subsection{\tt f\_equal -\label{f-equal} -\tacindex{f\_equal}} +\begin{coq_example} +Hint Resolve ex_intro. +Goal forall P:nat -> Prop, P 0 -> exists n, P n. +eauto. +\end{coq_example} +\begin{coq_eval} +Abort. +\end{coq_eval} -This tactic applies to a goal of the form $f\ a_1\ \ldots\ a_n = f'\ -a'_1\ \ldots\ a'_n$. Using {\tt f\_equal} on such a goal leads to -subgoals $f=f'$ and $a_1=a'_1$ and so on up to $a_n=a'_n$. Amongst -these subgoals, the simple ones (e.g. provable by -reflexivity or congruence) are automatically solved by {\tt f\_equal}. +Note that {\tt ex\_intro} should be declared as an +hint. +\SeeAlso Section~\ref{Hints-databases} -\section{Equality and inductive sets} +\subsection{\tt autounfold with \ident$_1$ \dots\ \ident$_n$ +\tacindex{autounfold} +\label{autounfold}} -We describe in this section some special purpose tactics dealing with -equality and inductive sets or types. These tactics use the equality -{\tt eq:forall (A:Type), A->A->Prop}, simply written with the -infix symbol {\tt =}. +This tactic unfolds constants that were declared through a {\tt Hint + Unfold} in the given databases. -\subsection{\tt decide equality -\label{decideequality} -\tacindex{decide equality}} +\begin{Variants} +\item {\tt autounfold with \ident$_1$ \dots\ \ident$_n$ in \textit{clause}} -This tactic solves a goal of the form -{\tt forall $x$ $y$:$R$, \{$x$=$y$\}+\{\verb|~|$x$=$y$\}}, where $R$ -is an inductive type such that its constructors do not take proofs or -functions as arguments, nor objects in dependent types. -It solves goals of the form {\tt \{$x$=$y$\}+\{\verb|~|$x$=$y$\}} as well. + Perform the unfolding in the given clause. -\subsection{\tt compare \term$_1$ \term$_2$ -\tacindex{compare}} +\item {\tt autounfold with *} -This tactic compares two given objects \term$_1$ and \term$_2$ -of an inductive datatype. If $G$ is the current goal, it leaves the sub-goals -\term$_1${\tt =}\term$_2$ {\tt ->} $G$ and \verb|~|\term$_1${\tt =}\term$_2$ -{\tt ->} $G$. The type -of \term$_1$ and \term$_2$ must satisfy the same restrictions as in the tactic -\texttt{decide equality}. + Uses the unfold hints declared in all the hint databases. +\end{Variants} -\subsection{\tt discriminate {\term} -\label{discriminate} -\tacindex{discriminate} -\tacindex{ediscriminate}} -This tactic proves any goal from an assumption stating that two -structurally different terms of an inductive set are equal. For -example, from {\tt (S (S O))=(S O)} we can derive by absurdity any -proposition. +\subsection{\tt autorewrite with \ident$_1$ \dots \ident$_n$. +\label{tactic:autorewrite} +\tacindex{autorewrite}} -The argument {\term} is assumed to be a proof of a statement -of conclusion {\tt{\term$_1$} = {\term$_2$}} with {\term$_1$} and -{\term$_2$} being elements of an inductive set. To build the proof, -the tactic traverses the normal forms\footnote{Reminder: opaque - constants will not be expanded by $\delta$ reductions} of -{\term$_1$} and {\term$_2$} looking for a couple of subterms {\tt u} -and {\tt w} ({\tt u} subterm of the normal form of {\term$_1$} and -{\tt w} subterm of the normal form of {\term$_2$}), placed at the same -positions and whose head symbols are two different constructors. If -such a couple of subterms exists, then the proof of the current goal -is completed, otherwise the tactic fails. +This tactic \footnote{The behavior of this tactic has much changed compared to +the versions available in the previous distributions (V6). This may cause +significant changes in your theories to obtain the same result. As a drawback +of the re-engineering of the code, this tactic has also been completely revised +to get a very compact and readable version.} carries out rewritings according +the rewriting rule bases {\tt \ident$_1$ \dots \ident$_n$}. -\Rem The syntax {\tt discriminate {\ident}} can be used to refer to a -hypothesis quantified in the goal. In this case, the quantified -hypothesis whose name is {\ident} is first introduced in the local -context using \texttt{intros until \ident}. +Each rewriting rule of a base \ident$_i$ is applied to the main subgoal until +it fails. Once all the rules have been processed, if the main subgoal has +progressed (e.g., if it is distinct from the initial main goal) then the rules +of this base are processed again. If the main subgoal has not progressed then +the next base is processed. For the bases, the behavior is exactly similar to +the processing of the rewriting rules. -\begin{ErrMsgs} -\item \errindex{No primitive equality found} -\item \errindex{Not a discriminable equality} -\end{ErrMsgs} +The rewriting rule bases are built with the {\tt Hint~Rewrite} vernacular +command. -\begin{Variants} -\item \texttt{discriminate} \num +\Warning{} This tactic may loop if you build non terminating rewriting systems. - This does the same thing as \texttt{intros until \num} followed by - \texttt{discriminate \ident} where {\ident} is the identifier for - the last introduced hypothesis. +\begin{Variant} +\item {\tt autorewrite with \ident$_1$ \dots \ident$_n$ using \tac}\\ +Performs, in the same way, all the rewritings of the bases {\tt \ident$_1$ $...$ +\ident$_n$} applying {\tt \tac} to the main subgoal after each rewriting step. -\item \texttt{discriminate} {\term} {\tt with} {\bindinglist} +\item \texttt{autorewrite with {\ident$_1$} \dots \ident$_n$ in {\qualid}} - This does the same thing as \texttt{discriminate {\term}} but using -the given bindings to instantiate parameters or hypotheses of {\term}. + Performs all the rewritings in hypothesis {\qualid}. +\item \texttt{autorewrite with {\ident$_1$} \dots \ident$_n$ in {\qualid} using \tac} -\item \texttt{ediscriminate} \num\\ - \texttt{ediscriminate} {\term} \zeroone{{\tt with} {\bindinglist}} + Performs all the rewritings in hypothesis {\qualid} applying {\tt + \tac} to the main subgoal after each rewriting step. - This works the same as {\tt discriminate} but if the type of {\term}, - or the type of the hypothesis referred to by {\num}, has uninstantiated - parameters, these parameters are left as existential variables. +\item \texttt{autorewrite with {\ident$_1$} \dots \ident$_n$ in \textit{clause}} + Performs all the rewritings in the clause \textit{clause}. \\ + The \textit{clause} argument must not contain any \texttt{type of} nor \texttt{value of}. -\item \texttt{discriminate} +\end{Variant} - This behaves like {\tt discriminate {\ident}} if {\ident} is the - name of an hypothesis to which {\tt discriminate} is applicable; if - the current goal is of the form {\term$_1$} {\tt <>} {\term$_2$}, - this behaves as {\tt intro {\ident}; injection {\ident}}. +\SeeAlso Section~\ref{HintRewrite} for feeding the database of lemmas used by {\tt autorewrite}. - \begin{ErrMsgs} - \item \errindex{No discriminable equalities} \\ - occurs when the goal does not verify the expected preconditions. - \end{ErrMsgs} -\end{Variants} +\SeeAlso Section~\ref{autorewrite-example} for examples showing the use of +this tactic. -\subsection{\tt injection {\term} -\label{injection} -\tacindex{injection} -\tacindex{einjection}} +% En attente d'un moyen de valoriser les fichiers de demos +%\SeeAlso file \texttt{contrib/Rocq/DEMOS/Demo\_AutoRewrite.v} -The {\tt injection} tactic is based on the fact that constructors of -inductive sets are injections. That means that if $c$ is a constructor -of an inductive set, and if $(c~\vec{t_1})$ and $(c~\vec{t_2})$ are two -terms that are equal then $~\vec{t_1}$ and $~\vec{t_2}$ are equal -too. +\section{Controlling automation} -If {\term} is a proof of a statement of conclusion - {\tt {\term$_1$} = {\term$_2$}}, -then {\tt injection} applies injectivity as deep as possible to -derive the equality of all the subterms of {\term$_1$} and {\term$_2$} -placed in the same positions. For example, from {\tt (S - (S n))=(S (S (S m)))} we may derive {\tt n=(S m)}. To use this -tactic {\term$_1$} and {\term$_2$} should be elements of an inductive -set and they should be neither explicitly equal, nor structurally -different. We mean by this that, if {\tt n$_1$} and {\tt n$_2$} are -their respective normal forms, then: -\begin{itemize} -\item {\tt n$_1$} and {\tt n$_2$} should not be syntactically equal, -\item there must not exist any pair of subterms {\tt u} and {\tt w}, - {\tt u} subterm of {\tt n$_1$} and {\tt w} subterm of {\tt n$_2$} , - placed in the same positions and having different constructors as - head symbols. -\end{itemize} -If these conditions are satisfied, then, the tactic derives the -equality of all the subterms of {\term$_1$} and {\term$_2$} placed in -the same positions and puts them as antecedents of the current goal. +\subsection{The hints databases for {\tt auto} and {\tt eauto} +\index{Hints databases} +\label{Hints-databases} +\comindex{Hint}} -\Example Consider the following goal: +The hints for \texttt{auto} and \texttt{eauto} are stored in +databases. Each database maps head symbols to a list of hints. One can +use the command \texttt{Print Hint \ident} to display the hints +associated to the head symbol \ident{} (see \ref{PrintHint}). Each +hint has a cost that is an nonnegative integer, and an optional pattern. +The hints with lower cost are tried first. A hint is tried by +\texttt{auto} when the conclusion of the current goal +matches its pattern or when it has no pattern. -\begin{coq_example*} -Inductive list : Set := - | nil : list - | cons : nat -> list -> list. -Variable P : list -> Prop. -\end{coq_example*} -\begin{coq_eval} -Lemma ex : - forall (l:list) (n:nat), P nil -> cons n l = cons 0 nil -> P l. -intros l n H H0. -\end{coq_eval} -\begin{coq_example} -Show. -injection H0. -\end{coq_example} -\begin{coq_eval} -Abort. -\end{coq_eval} +\subsubsection*{Creating Hint databases + \label{CreateHintDb}\comindex{CreateHintDb}} -Beware that \texttt{injection} yields always an equality in a sigma type -whenever the injected object has a dependent type. +One can optionally declare a hint database using the command +\texttt{Create HintDb}. If a hint is added to an unknown database, it +will be automatically created. -\Rem There is a special case for dependent pairs. If we have a decidable -equality over the type of the first argument, then it is safe to do -the projection on the second one, and so {\tt injection} will work fine. -To define such an equality, you have to use the {\tt Scheme} command -(see \ref{Scheme}). +\medskip +\texttt{Create HintDb} {\ident} [\texttt{discriminated}] +\medskip -\Rem If some quantified hypothesis of the goal is named {\ident}, then -{\tt injection {\ident}} first introduces the hypothesis in the local -context using \texttt{intros until \ident}. +This command creates a new database named \ident. +The database is implemented by a Discrimination Tree (DT) that serves as +an index of all the lemmas. The DT can use transparency information to decide +if a constant should be indexed or not (c.f. \ref{HintTransparency}), +making the retrieval more efficient. +The legacy implementation (the default one for new databases) uses the +DT only on goals without existentials (i.e., auto goals), for non-Immediate +hints and do not make use of transparency hints, putting more work on the +unification that is run after retrieval (it keeps a list of the lemmas +in case the DT is not used). The new implementation enabled by +the {\tt discriminated} option makes use of DTs in all cases and takes +transparency information into account. However, the order in which hints +are retrieved from the DT may differ from the order in which they were +inserted, making this implementation observationally different from the +legacy one. -\begin{ErrMsgs} -\item \errindex{Not a projectable equality but a discriminable one} -\item \errindex{Nothing to do, it is an equality between convertible terms} -\item \errindex{Not a primitive equality} -\end{ErrMsgs} +The general +command to add a hint to some database \ident$_1$, \dots, \ident$_n$ is +\begin{tabbing} + \texttt{Hint} \textsl{hint\_definition} \texttt{:} \ident$_1$ {\ldots} \ident$_n$ +\end{tabbing} \begin{Variants} -\item \texttt{injection} \num{} +\item \texttt{Hint} \textsl{hint\_definition} - This does the same thing as \texttt{intros until \num} followed by -\texttt{injection \ident} where {\ident} is the identifier for the last -introduced hypothesis. + No database name is given: the hint is registered in the {\tt core} + database. -\item \texttt{injection} \term{} {\tt with} {\bindinglist} +\item\texttt{Local Hint} \textsl{hint\_definition} \texttt{:} + \ident$_1$ \ldots\ \ident$_n$ - This does the same as \texttt{injection {\term}} but using - the given bindings to instantiate parameters or hypotheses of {\term}. + 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 {\tt Local} is useless since hints do not + survive anyway to the closure of sections. -\item \texttt{einjection} \num\\ - \texttt{einjection} \term{} \zeroone{{\tt with} {\bindinglist}} +\item\texttt{Local Hint} \textsl{hint\_definition} - This works the same as {\tt injection} but if the type of {\term}, - or the type of the hypothesis referred to by {\num}, has uninstantiated - parameters, these parameters are left as existential variables. + Idem for the {\tt core} database. -\item{\tt injection} - - If the current goal is of the form {\term$_1$} {\tt <>} {\term$_2$}, - this behaves as {\tt intro {\ident}; injection {\ident}}. - - \ErrMsg \errindex{goal does not satisfy the expected preconditions} +\end{Variants} -\item \texttt{injection} \term{} \zeroone{{\tt with} {\bindinglist}} \texttt{as} \nelist{\intropattern}{}\\ -\texttt{injection} \num{} \texttt{as} {\intropattern} {\ldots} {\intropattern}\\ -\texttt{injection} \texttt{as} {\intropattern} {\ldots} {\intropattern}\\ -\texttt{einjection} \term{} \zeroone{{\tt with} {\bindinglist}} \texttt{as} \nelist{\intropattern}{}\\ -\texttt{einjection} \num{} \texttt{as} {\intropattern} {\ldots} {\intropattern}\\ -\texttt{einjection} \texttt{as} {\intropattern} {\ldots} {\intropattern}\\ -\tacindex{injection \ldots{} as} - -These variants apply \texttt{intros} \nelist{\intropattern}{} after -the call to \texttt{injection} or \texttt{einjection}. +The \textsl{hint\_definition} is one of the following expressions: + +\begin{itemize} +\item \texttt{Resolve} {\term} + \comindex{Hint Resolve} + + This command adds {\tt apply {\term}} to the hint list + with the head symbol of the type of \term. The cost of that hint is + the number of subgoals generated by {\tt apply {\term}}. + + In case the inferred type of \term\ does not start with a product the + tactic added in the hint list is {\tt exact {\term}}. In case this + type can be reduced to a type starting with a product, the tactic {\tt + apply {\term}} is also stored in the hints list. -\end{Variants} + If the inferred type of \term\ contains a dependent + quantification on a predicate, it is added to the hint list of {\tt + eapply} instead of the hint list of {\tt apply}. In this case, a + warning is printed since the hint is only used by the tactic {\tt + eauto} (see \ref{eauto}). A typical example of a hint that is used + only by \texttt{eauto} is a transitivity lemma. -\subsection{\tt simplify\_eq {\term} -\tacindex{simplify\_eq} -\tacindex{esimplify\_eq} -\label{simplify-eq}} + \begin{ErrMsgs} + \item \errindex{Bound head variable} -Let {\term} be the proof of a statement of conclusion {\tt - {\term$_1$}={\term$_2$}}. If {\term$_1$} and -{\term$_2$} are structurally different (in the sense described for the -tactic {\tt discriminate}), then the tactic {\tt simplify\_eq} behaves as {\tt - discriminate {\term}}, otherwise it behaves as {\tt injection - {\term}}. + The head symbol of the type of {\term} is a bound variable such + that this tactic cannot be associated to a constant. -\Rem If some quantified hypothesis of the goal is named {\ident}, then -{\tt simplify\_eq {\ident}} first introduces the hypothesis in the local -context using \texttt{intros until \ident}. + \item \term\ \errindex{cannot be used as a hint} -\begin{Variants} -\item \texttt{simplify\_eq} \num + The type of \term\ contains products over variables which do not + appear in the conclusion. A typical example is a transitivity axiom. + In that case the {\tt apply} tactic fails, and thus is useless. - This does the same thing as \texttt{intros until \num} then -\texttt{simplify\_eq \ident} where {\ident} is the identifier for the last -introduced hypothesis. + \end{ErrMsgs} -\item \texttt{simplify\_eq} \term{} {\tt with} {\bindinglist} + \begin{Variants} - This does the same as \texttt{simplify\_eq {\term}} but using - the given bindings to instantiate parameters or hypotheses of {\term}. + \item \texttt{Resolve} {\term$_1$} \dots {\term$_m$} -\item \texttt{esimplify\_eq} \num\\ - \texttt{esimplify\_eq} \term{} \zeroone{{\tt with} {\bindinglist}} + Adds each \texttt{Resolve} {\term$_i$}. - This works the same as {\tt simplify\_eq} but if the type of {\term}, - or the type of the hypothesis referred to by {\num}, has uninstantiated - parameters, these parameters are left as existential variables. + \end{Variants} -\item{\tt simplify\_eq} +\item \texttt{Immediate {\term}} +\comindex{Hint Immediate} -If the current goal has form $t_1\verb=<>=t_2$, it behaves as -\texttt{intro {\ident}; simplify\_eq {\ident}}. -\end{Variants} + This command adds {\tt apply {\term}; trivial} to the hint list + associated with the head symbol of the type of {\ident} in the given + database. This tactic will fail if all the subgoals generated by + {\tt apply {\term}} are not solved immediately by the {\tt trivial} + tactic (which only tries tactics with cost $0$). -\subsection{\tt dependent rewrite -> {\ident} -\tacindex{dependent rewrite ->} -\label{dependent-rewrite}} + This command is useful for theorems such as the symmetry of equality + or $n+1=m+1 \to n=m$ that we may like to introduce with a + limited use in order to avoid useless proof-search. -This tactic applies to any goal. If \ident\ has type -\verb+(existT B a b)=(existT B a' b')+ -in the local context (i.e. each term of the -equality has a sigma type $\{ a:A~ \&~(B~a)\}$) this tactic rewrites -\verb+a+ into \verb+a'+ and \verb+b+ into \verb+b'+ in the current -goal. This tactic works even if $B$ is also a sigma type. This kind -of equalities between dependent pairs may be derived by the injection -and inversion tactics. + The cost of this tactic (which never generates subgoals) is always 1, + so that it is not used by {\tt trivial} itself. -\begin{Variants} -\item{\tt dependent rewrite <- {\ident}} -\tacindex{dependent rewrite <-} \\ -Analogous to {\tt dependent rewrite ->} but uses the equality from -right to left. -\end{Variants} + \begin{ErrMsgs} -\section{Inversion -\label{inversion}} + \item \errindex{Bound head variable} -\subsection{\tt inversion {\ident} -\tacindex{inversion}} + \item \term\ \errindex{cannot be used as a hint} -Let the type of \ident~ in the local context be $(I~\vec{t})$, -where $I$ is a (co)inductive predicate. Then, -\texttt{inversion} applied to \ident~ derives for each possible -constructor $c_i$ of $(I~\vec{t})$, {\bf all} the necessary -conditions that should hold for the instance $(I~\vec{t})$ to be -proved by $c_i$. + \end{ErrMsgs} -\Rem If {\ident} does not denote a hypothesis in the local context -but refers to a hypothesis quantified in the goal, then the -latter is first introduced in the local context using -\texttt{intros until \ident}. + \begin{Variants} -\begin{Variants} -\item \texttt{inversion} \num - - This does the same thing as \texttt{intros until \num} then - \texttt{inversion \ident} where {\ident} is the identifier for the - last introduced hypothesis. + \item \texttt{Immediate} {\term$_1$} \dots {\term$_m$} -\item \tacindex{inversion\_clear} \texttt{inversion\_clear} \ident + Adds each \texttt{Immediate} {\term$_i$}. - This behaves as \texttt{inversion} and then erases \ident~ from the - context. + \end{Variants} -\item \tacindex{inversion \dots\ as} \texttt{inversion} {\ident} \texttt{as} {\intropattern} - - This behaves as \texttt{inversion} but using names in - {\intropattern} for naming hypotheses. The {\intropattern} must have - the form {\tt [} $p_{11}$ \ldots $p_{1n_1}$ {\tt |} {\ldots} {\tt |} - $p_{m1}$ \ldots $p_{mn_m}$ {\tt ]} with $m$ being the number of - constructors of the type of {\ident}. Be careful that the list must - be of length $m$ even if {\tt inversion} discards some cases (which - is precisely one of its roles): for the discarded cases, just use an - empty list (i.e. $n_i=0$). +\item \texttt{Constructors} {\ident} +\comindex{Hint Constructors} - The arguments of the $i^{th}$ constructor and the - equalities that {\tt inversion} introduces in the context of the - goal corresponding to the $i^{th}$ constructor, if it exists, get - their names from the list $p_{i1}$ {\ldots} $p_{in_i}$ in order. If - there are not enough names, {\tt induction} invents names for the - remaining variables to introduce. In case an equation splits into - several equations (because {\tt inversion} applies {\tt injection} - on the equalities it generates), the corresponding name $p_{ij}$ in - the list must be replaced by a sublist of the form {\tt [$p_{ij1}$ - {\ldots} $p_{ijq}$]} (or, equivalently, {\tt ($p_{ij1}$, - {\ldots}, $p_{ijq}$)}) where $q$ is the number of subequalities - obtained from splitting the original equation. Here is an example. + If {\ident} is an inductive type, this command adds all its + constructors as hints of type \texttt{Resolve}. Then, when the + conclusion of current goal has the form \texttt{({\ident} \dots)}, + \texttt{auto} will try to apply each constructor. -\begin{coq_eval} -Require Import List. -\end{coq_eval} + \begin{ErrMsgs} -\begin{coq_example} -Inductive contains0 : list nat -> Prop := - | in_hd : forall l, contains0 (0 :: l) - | in_tl : forall l b, contains0 l -> contains0 (b :: l). -Goal forall l:list nat, contains0 (1 :: l) -> contains0 l. -intros l H; inversion H as [ | l' p Hl' [Heqp Heql'] ]. -\end{coq_example} + \item {\ident} \errindex{is not an inductive type} -\begin{coq_eval} -Abort. -\end{coq_eval} + \item {\ident} \errindex{not declared} -\item \texttt{inversion} {\num} {\tt as} {\intropattern} + \end{ErrMsgs} - This allows to name the hypotheses introduced by - \texttt{inversion} {\num} in the context. + \begin{Variants} -\item \tacindex{inversion\_cleardots\ as} \texttt{inversion\_clear} - {\ident} {\tt as} {\intropattern} + \item \texttt{Constructors} {\ident$_1$} \dots {\ident$_m$} - This allows to name the hypotheses introduced by - \texttt{inversion\_clear} in the context. - -\item \tacindex{inversion \dots\ in} \texttt{inversion } {\ident} - \texttt{in} \ident$_1$ \dots\ \ident$_n$ + Adds each \texttt{Constructors} {\ident$_i$}. - Let \ident$_1$ \dots\ \ident$_n$, be identifiers in the local context. This - tactic behaves as generalizing \ident$_1$ \dots\ \ident$_n$, and - then performing \texttt{inversion}. - -\item \tacindex{inversion \dots\ as \dots\ in} \texttt{inversion } - {\ident} {\tt as} {\intropattern} \texttt{in} \ident$_1$ \dots\ - \ident$_n$ - - This allows to name the hypotheses introduced in the context by - \texttt{inversion} {\ident} \texttt{in} \ident$_1$ \dots\ - \ident$_n$. - -\item \tacindex{inversion\_clear {\ldots} in} \texttt{inversion\_clear} - {\ident} \texttt{in} \ident$_1$ {\ldots} \ident$_n$ - - Let \ident$_1$ \dots\ \ident$_n$, be identifiers in the local context. This - tactic behaves as generalizing \ident$_1$ {\ldots} \ident$_n$, and - then performing {\tt inversion\_clear}. - -\item \tacindex{inversion\_clear {\ldots} as \dots\ in} - \texttt{inversion\_clear} {\ident} \texttt{as} {\intropattern} - \texttt{in} \ident$_1$ {\ldots} \ident$_n$ + \end{Variants} - This allows to name the hypotheses introduced in the context by - \texttt{inversion\_clear} {\ident} \texttt{in} \ident$_1$ {\ldots} - \ident$_n$. +\item \texttt{Unfold} {\qualid} +\comindex{Hint Unfold} -\item \tacindex{dependent inversion} \texttt{dependent inversion} - {\ident} - - That must be used when \ident\ appears in the current goal. It acts - like \texttt{inversion} and then substitutes \ident\ for the - corresponding term in the goal. - -\item \tacindex{dependent inversion \dots\ as } \texttt{dependent - inversion} {\ident} \texttt{as} {\intropattern} - - This allows to name the hypotheses introduced in the context by - \texttt{dependent inversion} {\ident}. + This adds the tactic {\tt unfold {\qualid}} to the hint list that + will only be used when the head constant of the goal is \ident. Its + cost is 4. -\item \tacindex{dependent inversion\_clear} \texttt{dependent - inversion\_clear} {\ident} - - Like \texttt{dependent inversion}, except that {\ident} is cleared - from the local context. + \begin{Variants} -\item \tacindex{dependent inversion\_clear \dots\ as} - \texttt{dependent inversion\_clear} {\ident}\texttt{as} {\intropattern} - - This allows to name the hypotheses introduced in the context by - \texttt{dependent inversion\_clear} {\ident}. + \item \texttt{Unfold} {\ident$_1$} \dots {\ident$_m$} -\item \tacindex{dependent inversion \dots\ with} \texttt{dependent - inversion } {\ident} \texttt{ with } \term - - This variant allows you to specify the generalization of the goal. It - is useful when the system fails to generalize the goal automatically. If - {\ident} has type $(I~\vec{t})$ and $I$ has type - $forall (\vec{x}:\vec{T}), s$, then \term~ must be of type - $I:forall (\vec{x}:\vec{T}), I~\vec{x}\to s'$ where $s'$ is the - type of the goal. + Adds each \texttt{Unfold} {\ident$_i$}. -\item \tacindex{dependent inversion \dots\ as \dots\ with} - \texttt{dependent inversion } {\ident} \texttt{as} {\intropattern} - \texttt{ with } \term - - This allows to name the hypotheses introduced in the context by - \texttt{dependent inversion } {\ident} \texttt{ with } \term. + \end{Variants} -\item \tacindex{dependent inversion\_clear \dots\ with} - \texttt{dependent inversion\_clear } {\ident} \texttt{ with } \term - - Like \texttt{dependent inversion \dots\ with} but clears {\ident} from - the local context. +\item \texttt{Transparent}, \texttt{Opaque} {\qualid} +\label{HintTransparency} +\comindex{Hint Transparent} +\comindex{Hint Opaque} -\item \tacindex{dependent inversion\_clear \dots\ as \dots\ with} - \texttt{dependent inversion\_clear } {\ident} \texttt{as} - {\intropattern} \texttt{ with } \term - - This allows to name the hypotheses introduced in the context by - \texttt{dependent inversion\_clear } {\ident} \texttt{ with } \term. + This adds a transparency hint to the database, making {\tt {\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 \texttt{discriminated} databases. -\item \tacindex{simple inversion} \texttt{simple inversion} {\ident} - - It is a very primitive inversion tactic that derives all the necessary - equalities but it does not simplify the constraints as - \texttt{inversion} does. + \begin{Variants} -\item \tacindex{simple inversion \dots\ as} \texttt{simple inversion} - {\ident} \texttt{as} {\intropattern} - - This allows to name the hypotheses introduced in the context by - \texttt{simple inversion}. + \item \texttt{Transparent}, \texttt{Opaque} {\ident$_1$} \dots {\ident$_m$} -\item \tacindex{inversion \dots\ using} \texttt{inversion} \ident - \texttt{ using} \ident$'$ - - Let {\ident} have type $(I~\vec{t})$ ($I$ an inductive - predicate) in the local context, and \ident$'$ be a (dependent) inversion - lemma. Then, this tactic refines the current goal with the specified - lemma. + Declares each {\ident$_i$} as a transparent or opaque constant. -\item \tacindex{inversion \dots\ using \dots\ in} \texttt{inversion} - {\ident} \texttt{using} \ident$'$ \texttt{in} \ident$_1$\dots\ \ident$_n$ - - This tactic behaves as generalizing \ident$_1$\dots\ \ident$_n$, - then doing \texttt{inversion} {\ident} \texttt{using} \ident$'$. + \end{Variants} -\end{Variants} +\item \texttt{Extern \num\ [\pattern]\ => }\textsl{tactic} +\comindex{Hint Extern} -\SeeAlso~\ref{inversion-examples} for detailed examples + This hint type is to extend \texttt{auto} with tactics other than + \texttt{apply} and \texttt{unfold}. For that, we must specify a + cost, an optional pattern and a tactic to execute. Here is an example: -\subsection{\tt Derive Inversion {\ident} with - ${\tt forall (}\vec{x}{\tt :}\vec{T}{\tt),} I~\vec{t}$ Sort \sort -\label{Derive-Inversion} -\comindex{Derive Inversion}} +\begin{quotation} +\begin{verbatim} +Hint Extern 4 (~(_ = _)) => discriminate. +\end{verbatim} +\end{quotation} -This command generates an inversion principle for the -\texttt{inversion \dots\ using} tactic. -Let $I$ be an inductive predicate and $\vec{x}$ the variables -occurring in $\vec{t}$. This command generates and stocks the -inversion lemma for the sort \sort~ corresponding to the instance -$forall (\vec{x}:\vec{T}), I~\vec{t}$ with the name {\ident} in the {\bf -global} environment. When applied it is equivalent to have inverted -the instance with the tactic {\tt inversion}. + Now, when the head of the goal is a disequality, \texttt{auto} will + try \texttt{discriminate} if it does not manage to solve the goal + with hints with a cost less than 4. -\begin{Variants} -\item \texttt{Derive Inversion\_clear} {\ident} \texttt{with} - \comindex{Derive Inversion\_clear} - $forall (\vec{x}:\vec{T}), I~\vec{t}$ \texttt{Sort} \sort~ \\ - \index{Derive Inversion\_clear \dots\ with} - When applied it is equivalent to having - inverted the instance with the tactic \texttt{inversion} - replaced by the tactic \texttt{inversion\_clear}. -\item \texttt{Derive Dependent Inversion} {\ident} \texttt{with} - $forall (\vec{x}:\vec{T}), I~\vec{t}$ \texttt{Sort} \sort~\\ - \comindex{Derive Dependent Inversion} - When applied it is equivalent to having - inverted the instance with the tactic \texttt{dependent inversion}. -\item \texttt{Derive Dependent Inversion\_clear} {\ident} \texttt{with} - $forall (\vec{x}:\vec{T}), I~\vec{t}$ \texttt{Sort} \sort~\\ - \comindex{Derive Dependent Inversion\_clear} - When applied it is equivalent to having - inverted the instance with the tactic \texttt{dependent inversion\_clear}. -\end{Variants} + One can even use some sub-patterns of the pattern in the tactic + script. A sub-pattern is a question mark followed by an ident, like + \texttt{?X1} or \texttt{?X2}. Here is an example: -\SeeAlso \ref{inversion-examples} for examples +% Require EqDecide. +\begin{coq_example*} +Require Import List. +\end{coq_example*} +\begin{coq_example} +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 auto with eqdec. +\end{coq_example} +\begin{coq_eval} +Abort. +\end{coq_eval} +\end{itemize} +\Rem One can use an \texttt{Extern} hint with no pattern to do +pattern-matching on hypotheses using \texttt{match goal with} inside +the tactic. -\subsection[\tt functional inversion \ident]{\tt functional inversion \ident\label{sec:functional-inversion}} +\begin{Variants} +\item \texttt{Hint} \textsl{hint\_definition} -\texttt{functional inversion} is a \emph{highly} experimental tactic -which performs inversion on hypothesis \ident\ of the form -\texttt{\qualid\ \term$_1$\dots\term$_n$\ = \term} or \texttt{\term\ = - \qualid\ \term$_1$\dots\term$_n$} where \qualid\ must have been -defined using \texttt{Function} (see Section~\ref{Function}). + No database name is given: the hint is registered in the {\tt core} + database. -\begin{ErrMsgs} -\item \errindex{Hypothesis {\ident} must contain at least one Function} -\item \errindex{Cannot find inversion information for hypothesis \ident} - This error may be raised when some inversion lemma failed to be - generated by Function. -\end{ErrMsgs} +\item\texttt{Hint Local} \textsl{hint\_definition} \texttt{:} + \ident$_1$ \ldots\ \ident$_n$ -\begin{Variants} -\item {\tt functional inversion \num} + 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 {\tt Local} is useless since hints do not + survive anyway to the closure of sections. - This does the same thing as \texttt{intros until \num} then - \texttt{functional inversion \ident} where {\ident} is the - identifier for the last introduced hypothesis. -\item {\tt functional inversion \ident\ \qualid}\\ - {\tt functional inversion \num\ \qualid} +\item\texttt{Hint Local} \textsl{hint\_definition} + + Idem for the {\tt core} database. - In case the hypothesis {\ident} (or {\num}) has a type of the form - \texttt{\qualid$_1$\ \term$_1$\dots\term$_n$\ =\ \qualid$_2$\ - \term$_{n+1}$\dots\term$_{n+m}$} where \qualid$_1$ and \qualid$_2$ - are valid candidates to functional inversion, this variant allows to - choose which must be inverted. \end{Variants} +% There are shortcuts that allow to define several goal at once: +% \begin{itemize} +% \item \comindex{Hints Resolve}\texttt{Hints Resolve \ident$_1$ \dots\ \ident$_n$ : \ident.}\\ +% This command is a shortcut for the following ones: +% \begin{quotation} +% \noindent\texttt{Hint \ident$_1$ : \ident\ := Resolve \ident$_1$}\\ +% \dots\\ +% \texttt{Hint \ident$_1$ : \ident := Resolve \ident$_1$} +% \end{quotation} +% Notice that the hint name is the same that the theorem given as +% hint. +% \item \comindex{Hints Immediate}\texttt{Hints Immediate \ident$_1$ \dots\ \ident$_n$ : \ident.}\\ +% \item \comindex{Hints Unfold}\texttt{Hints Unfold \qualid$_1$ \dots\ \qualid$_n$ : \ident.}\\ +% \end{itemize} -\subsection{\tt quote \ident -\tacindex{quote} -\index{2-level approach}} +%\begin{Warnings} +% \item \texttt{Overriding hint named \dots\ in database \dots} +%\end{Warnings} -This kind of inversion has nothing to do with the tactic -\texttt{inversion} above. This tactic does \texttt{change (\ident\ - t)}, where \texttt{t} is a term built in order to ensure the -convertibility. In other words, it does inversion of the function -\ident. This function must be a fixpoint on a simple recursive -datatype: see~\ref{quote-examples} for the full details. -\begin{ErrMsgs} -\item \errindex{quote: not a simple fixpoint}\\ - Happens when \texttt{quote} is not able to perform inversion properly. -\end{ErrMsgs} -\begin{Variants} -\item \texttt{quote {\ident} [ \ident$_1$ \dots \ident$_n$ ]}\\ - All terms that are built only with \ident$_1$ \dots \ident$_n$ will be - considered by \texttt{quote} as constants rather than variables. -\end{Variants} +\subsection{Hint databases defined in the \Coq\ standard library} -% En attente d'un moyen de valoriser les fichiers de demos -% \SeeAlso file \texttt{theories/DEMOS/DemoQuote.v} in the distribution +Several hint databases are defined in the \Coq\ standard library. The +actual content of a database is the collection of the hints declared +to belong to this database in each of the various modules currently +loaded. Especially, requiring new modules potentially extend a +database. At {\Coq} startup, only the {\tt core} and {\tt v62} +databases are non empty and can be used. -\section[Classical tactics]{Classical tactics\label{ClassicalTactics}} +\begin{description} -In order to ease the proving process, when the {\tt Classical} module is loaded. A few more tactics are available. Make sure to load the module using the \texttt{Require Import} command. +\item[\tt core] This special database is automatically used by + \texttt{auto}, except when pseudo-database \texttt{nocore} is + given to \texttt{auto}. The \texttt{core} database contains + only basic lemmas about negation, + conjunction, and so on from. Most of the hints in this database come + from the \texttt{Init} and \texttt{Logic} directories. -\subsection{{\tt classical\_left, classical\_right} \tacindex{classical\_left} \tacindex{classical\_right}} +\item[\tt arith] This database contains all lemmas about Peano's + arithmetic proved in the directories \texttt{Init} and + \texttt{Arith} -The tactics \texttt{classical\_left} and \texttt{classical\_right} are the analog of the \texttt{left} and \texttt{right} but using classical logic. They can only be used for disjunctions. -Use \texttt{classical\_left} to prove the left part of the disjunction with the assumption that the negation of right part holds. -Use \texttt{classical\_right} to prove the right part of the disjunction with the assumption that the negation of left part holds. +\item[\tt zarith] contains lemmas about binary signed integers from + the directories \texttt{theories/ZArith}. When required, the module + {\tt Omega} also extends the database {\tt zarith} with a high-cost + hint that calls {\tt omega} on equations and inequalities in {\tt + nat} or {\tt Z}. -\section{Automatizing -\label{Automatizing}} +\item[\tt bool] contains lemmas about booleans, mostly from directory + \texttt{theories/Bool}. -\subsection{\tt auto -\label{auto} -\tacindex{auto}} +\item[\tt datatypes] is for lemmas about lists, streams and so on that + are mainly proved in the \texttt{Lists} subdirectory. -This tactic implements a Prolog-like resolution procedure to solve the -current goal. It first tries to solve the goal using the {\tt - assumption} tactic, then it reduces the goal to an atomic one using -{\tt intros} and introducing the newly generated hypotheses as hints. -Then it looks at the list of tactics associated to the head symbol of -the goal and tries to apply one of them (starting from the tactics -with lower cost). This process is recursively applied to the generated -subgoals. +\item[\tt sets] contains lemmas about sets and relations from the + directories \texttt{Sets} and \texttt{Relations}. -By default, \texttt{auto} only uses the hypotheses of the current goal and the -hints of the database named {\tt core}. +\item[\tt typeclass\_instances] contains all the type class instances + declared in the environment, including those used for \texttt{setoid\_rewrite}, + from the \texttt{Classes} directory. +\end{description} + +There is also a special database called {\tt v62}. It collects all +hints that were declared in the versions of {\Coq} prior to version +6.2.4 when the databases {\tt core}, {\tt arith}, and so on were +introduced. The purpose of the database {\tt v62} is to ensure +compatibility with further versions of {\Coq} for developments done in +versions prior to 6.2.4 ({\tt auto} being replaced by {\tt auto with v62}). +The database {\tt v62} is intended not to be extended (!). It is not +included in the hint databases list used in the {\tt auto with *} tactic. + +Furthermore, you are advised not to put your own hints in the +{\tt core} database, but use one or several databases specific to your +development. + +\subsection{\tt Print Hint +\label{PrintHint} +\comindex{Print Hint}} + +This command displays all hints that apply to the current goal. It +fails if no proof is being edited, while the two variants can be used at +every moment. \begin{Variants} -\item {\tt auto \num} +\item {\tt Print Hint {\ident} } - Forces the search depth to be \num. The maximal search depth is 5 by - default. + This command displays only tactics associated with \ident\ in the + hints list. This is independent of the goal being edited, so this + command will not fail if no goal is being edited. -\item {\tt auto with \ident$_1$ \dots\ \ident$_n$} - - Uses the hint databases $\ident_1$ \dots\ $\ident_n$ in addition to - the database {\tt core}. See Section~\ref{Hints-databases} for the - list of pre-defined databases and the way to create or extend a - database. This option can be combined with the previous one. +\item {\tt Print Hint *} -\item {\tt auto with *} + This command displays all declared hints. - Uses all existing hint databases, minus the special database - {\tt v62}. See Section~\ref{Hints-databases} +\item {\tt Print HintDb {\ident} } +\label{PrintHintDb} +\comindex{Print HintDb} -\item \texttt{auto using} \nterm{lemma}$_1$ {\tt ,} {\ldots} {\tt ,} \nterm{lemma}$_n$ + This command displays all hints from database \ident. - Uses \nterm{lemma}$_1$, \ldots, \nterm{lemma}$_n$ in addition to - hints (can be combined with the \texttt{with \ident} option). If - $lemma_i$ is an inductive type, it is the collection of its - constructors which is added as hints. +\end{Variants} -\item \texttt{auto using} \nterm{lemma}$_1$ {\tt ,} {\ldots} {\tt ,} \nterm{lemma}$_n$ with \ident$_1$ {\ldots} \ident$_n$ +\subsection{\tt Hint Rewrite \term$_1$ \dots \term$_n$ : \ident +\label{HintRewrite} +\comindex{Hint Rewrite}} - This combines the effects of the {\tt using} and {\tt with} options. +This vernacular command adds the terms {\tt \term$_1$ \dots \term$_n$} +(their types must be equalities) in the rewriting base {\tt \ident} +with the default orientation (left to right). Notice that the +rewriting bases are distinct from the {\tt auto} hint bases and that +{\tt auto} does not take them into account. -\item {\tt trivial}\tacindex{trivial} +This command is synchronous with the section mechanism (see \ref{Section}): +when closing a section, all aliases created by \texttt{Hint Rewrite} in that +section are lost. Conversely, when loading a module, all \texttt{Hint Rewrite} +declarations at the global level of that module are loaded. - This tactic is a restriction of {\tt auto} that is not recursive and - tries only hints which cost 0. Typically it solves trivial - equalities like $X=X$. +\begin{Variants} +\item {\tt Hint Rewrite -> \term$_1$ \dots \term$_n$ : \ident}\\ +This is strictly equivalent to the command above (we only make explicit the +orientation which otherwise defaults to {\tt ->}). -\item \texttt{trivial with \ident$_1$ \dots\ \ident$_n$} +\item {\tt Hint Rewrite <- \term$_1$ \dots \term$_n$ : \ident}\\ +Adds the rewriting rules {\tt \term$_1$ \dots \term$_n$} with a right-to-left +orientation in the base {\tt \ident}. -\item \texttt{trivial with *} +\item {\tt Hint Rewrite \term$_1$ \dots \term$_n$ using {\tac} : {\ident}}\\ +When the rewriting rules {\tt \term$_1$ \dots \term$_n$} in {\tt \ident} will +be used, the tactic {\tt \tac} will be applied to the generated subgoals, the +main subgoal excluded. -\end{Variants} +%% \item +%% {\tt Hint Rewrite [ \term$_1$ \dots \term$_n$ ] in \ident}\\ +%% {\tt Hint Rewrite [ \term$_1$ \dots \term$_n$ ] in {\ident} using {\tac}}\\ +%% These are deprecated syntactic variants for +%% {\tt Hint Rewrite \term$_1$ \dots \term$_n$ : \ident} and +%% {\tt Hint Rewrite \term$_1$ \dots \term$_n$ using {\tac} : {\ident}}. -\Rem {\tt auto} either solves completely the goal or else leaves it -intact. \texttt{auto} and \texttt{trivial} never fail. +\item \texttt{Print Rewrite HintDb {\ident}} -\SeeAlso Section~\ref{Hints-databases} + This command displays all rewrite hints contained in {\ident}. -\subsection{\tt eauto -\tacindex{eauto} -\label{eauto}} +\end{Variants} -This tactic generalizes {\tt auto}. In contrast with -the latter, {\tt eauto} uses unification of the goal -against the hints rather than pattern-matching -(in other words, it uses {\tt eapply} instead of -{\tt apply}). -As a consequence, {\tt eauto} can solve such a goal: +\subsection{Hints and sections +\label{Hint-and-Section}} -\begin{coq_example} -Hint Resolve ex_intro. -Goal forall P:nat -> Prop, P 0 -> exists n, P n. -eauto. -\end{coq_example} -\begin{coq_eval} -Abort. -\end{coq_eval} +Hints provided by the \texttt{Hint} commands are erased when closing a +section. Conversely, all hints of a module \texttt{A} that are not +defined inside a section (and not defined with option {\tt Local}) become +available when the module {\tt A} is imported (using +e.g. \texttt{Require Import A.}). -Note that {\tt ex\_intro} should be declared as an -hint. +\subsection{Setting implicit automation tactics} -\SeeAlso Section~\ref{Hints-databases} +\subsubsection[\tt Proof with {\tac}.]{\tt Proof with {\tac}.\label{ProofWith} +\comindex{Proof with}} -\subsection{\tt autounfold with \ident$_1$ \dots\ \ident$_n$ -\tacindex{autounfold} -\label{autounfold}} + This command may be used to start a proof. It defines a default + tactic to be used each time a tactic command {\tac$_1$} is ended by + ``\verb#...#''. In this case the tactic command typed by the user is + equivalent to \tac$_1$;{\tac}. -This tactic unfolds constants that were declared through a {\tt Hint - Unfold} in the given databases. +\SeeAlso {\tt Proof.} in Section~\ref{BeginProof}. \begin{Variants} -\item {\tt autounfold with \ident$_1$ \dots\ \ident$_n$ in \textit{clause}} - - Perform the unfolding in the given clause. +\item {\tt Proof with {\tac} using {\ident$_1$ \dots {\ident$_n$}}} + Combines in a single line {\tt Proof with} and {\tt Proof using}, + see~\ref{ProofUsing} +\item {\tt Proof using {\ident$_1$ \dots {\ident$_n$}} with {\tac}} + Combines in a single line {\tt Proof with} and {\tt Proof using}, + see~\ref{ProofUsing} -\item {\tt autounfold with *} - - Uses the unfold hints declared in all the hint databases. \end{Variants} +\subsubsection[\tt Declare Implicit Tactic {\tac}.]{\tt Declare Implicit Tactic {\tac}.\comindex{Declare Implicit Tactic}} -% EXISTE ENCORE ? -% -% \subsection{\tt Prolog [ \term$_1$ \dots\ \term$_n$ ] \num} -% \tacindex{Prolog}\label{Prolog} -% This tactic, implemented by Chet Murthy, is based upon the concept of -% existential variables of Gilles Dowek, stating that resolution is a -% kind of unification. It tries to solve the current goal using the {\tt -% Assumption} tactic, the {\tt intro} tactic, and applying hypotheses -% of the local context and terms of the given list {\tt [ \term$_1$ -% \dots\ \term$_n$\ ]}. It is more powerful than {\tt auto} since it -% may apply to any theorem, even those of the form {\tt (x:A)(P x) -> Q} -% where {\tt x} does not appear free in {\tt Q}. The maximal search -% depth is {\tt \num}. +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. + +Here is an example: + +\begin{coq_example} +Parameter quo : nat -> forall n:nat, n<>0 -> nat. +Notation "x // y" := (quo x y _) (at level 40). -% \begin{ErrMsgs} -% \item \errindex{Prolog failed}\\ -% The Prolog tactic was not able to prove the subgoal. -% \end{ErrMsgs} +Declare Implicit Tactic assumption. +Goal forall n m, m<>0 -> { q:nat & { r | q * m + r = n } }. +intros. +exists (n // m). +\end{coq_example} + +The tactic {\tt exists (n // m)} did not fail. The hole was solved by +{\tt assumption} so that it behaved as {\tt exists (quo n m H)}. + +\section{Decision procedures} \subsection{\tt tauto \tacindex{tauto} @@ -3429,7 +3862,7 @@ instantiation of \verb=x= is necessary. The tactic \texttt{intuition} takes advantage of the search-tree built by the decision procedure involved in the tactic {\tt tauto}. It uses this information to generate a set of subgoals equivalent to the -original one (but simpler than it) and applies the tactic +original one (but simpler than it) and applies the tactic {\tac} to them \cite{Mun94}. If this tactic fails on some goals then {\tt intuition} fails. In fact, {\tt tauto} is simply {\tt intuition fail}. @@ -3465,17 +3898,17 @@ incompatibilities. \tacindex{rtauto} \label{rtauto}} -The {\tt rtauto} tactic solves propositional tautologies similarly to what {\tt tauto} does. The main difference is that the proof term is built using a reflection scheme applied to a sequent calculus proof of the goal. The search procedure is also implemented using a different technique. +The {\tt rtauto} tactic solves propositional tautologies similarly to what {\tt tauto} does. The main difference is that the proof term is built using a reflection scheme applied to a sequent calculus proof of the goal. The search procedure is also implemented using a different technique. -Users should be aware that this difference may result in faster proof-search but slower proof-checking, and {\tt rtauto} might not solve goals that {\tt tauto} would be able to solve (e.g. goals involving universal quantifiers). +Users should be aware that this difference may result in faster proof-search but slower proof-checking, and {\tt rtauto} might not solve goals that {\tt tauto} would be able to solve (e.g. goals involving universal quantifiers). \subsection{{\tt firstorder} \tacindex{firstorder} \label{firstorder}} The tactic \texttt{firstorder} is an {\it experimental} extension of -\texttt{tauto} to -first-order reasoning, written by Pierre Corbineau. +\texttt{tauto} to +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. @@ -3505,118 +3938,9 @@ instead may reason about any first-order class inductive definition. \end{Variants} Proof-search is bounded by a depth parameter which can be set by typing the -{\nobreak \tt Set Firstorder Depth $n$} \comindex{Set Firstorder Depth} +{\nobreak \tt Set Firstorder Depth $n$} \comindex{Set Firstorder Depth} vernacular command. -%% \subsection{{\tt jp} {\em (Jprover)} -%% \tacindex{jp} -%% \label{jprover}} - -%% The tactic \texttt{jp}, due to Huang Guan-Shieng, is an experimental -%% port of the {\em Jprover}\cite{SLKN01} semi-decision procedure for -%% first-order intuitionistic logic implemented in {\em -%% NuPRL}\cite{Kre02}. - -%% The tactic \texttt{jp}, due to Huang Guan-Shieng, is an {\it -%% experimental} port of the {\em Jprover}\cite{SLKN01} semi-decision -%% procedure for first-order intuitionistic logic implemented in {\em -%% NuPRL}\cite{Kre02}. - -%% Search may optionnaly be bounded by a multiplicity parameter -%% indicating how many (at most) copies of a formula may be used in -%% the proof process, its absence may lead to non-termination of the tactic. - -%% %\begin{coq_eval} -%% %Variable S:Set. -%% %Variables P Q:S->Prop. -%% %Variable f:S->S. -%% %\end{coq_eval} - -%% %\begin{coq_example*} -%% %Lemma example: (exists x |P x\/Q x)->(exists x |P x)\/(exists x |Q x). -%% %jp. -%% %Qed. - -%% %Lemma example2: (forall x ,P x->P (f x))->forall x,P x->P (f(f x)). -%% %jp. -%% %Qed. -%% %\end{coq_example*} - -%% \begin{Variants} -%% \item {\tt jp $n$}\\ -%% \tacindex{jp $n$} -%% Tries the {\em Jprover} procedure with multiplicities up to $n$, -%% starting from 1. -%% \item {\tt jp}\\ -%% Tries the {\em Jprover} procedure without multiplicity bound, -%% possibly running forever. -%% \end{Variants} - -%% \begin{ErrMsgs} -%% \item \errindex{multiplicity limit reached}\\ -%% The procedure tried all multiplicities below the limit and -%% failed. Goal might be solved by increasing the multiplicity limit. -%% \item \errindex{formula is not provable}\\ -%% The procedure determined that goal was not provable in -%% intuitionistic first-order logic, no matter how big the -%% multiplicity is. -%% \end{ErrMsgs} - - -% \subsection[\tt Linear]{\tt Linear\tacindex{Linear}\label{Linear}} -% The tactic \texttt{Linear}, due to Jean-Christophe Filli{\^a}atre -% \cite{Fil94}, implements a decision procedure for {\em Direct -% Predicate Calculus}, that is first-order Gentzen's Sequent Calculus -% without contraction rules \cite{KeWe84,BeKe92}. Intuitively, a -% first-order goal is provable in Direct Predicate Calculus if it can be -% proved using each hypothesis at most once. - -% Unlike the previous tactics, the \texttt{Linear} tactic does not belong -% to the initial state of the system, and it must be loaded explicitly -% with the command - -% \begin{coq_example*} -% Require Linear. -% \end{coq_example*} - -% For instance, assuming that \texttt{even} and \texttt{odd} are two -% predicates on natural numbers, and \texttt{a} of type \texttt{nat}, the -% tactic \texttt{Linear} solves the following goal - -% \begin{coq_eval} -% Variables even,odd : nat -> Prop. -% Variable a:nat. -% \end{coq_eval} - -% \begin{coq_example*} -% Lemma example : (even a) -% -> ((x:nat)((even x)->(odd (S x)))) -% -> (EX y | (odd y)). -% \end{coq_example*} - -% You can find examples of the use of \texttt{Linear} in -% \texttt{theories/DEMOS/DemoLinear.v}. -% \begin{coq_eval} -% Abort. -% \end{coq_eval} - -% \begin{Variants} -% \item {\tt Linear with \ident$_1$ \dots\ \ident$_n$}\\ -% \tacindex{Linear with} -% Is equivalent to apply first {\tt generalize \ident$_1$ \dots -% \ident$_n$} (see Section~\ref{generalize}) then the \texttt{Linear} -% tactic. So one can use axioms, lemmas or hypotheses of the local -% context with \texttt{Linear} in this way. -% \end{Variants} - -% \begin{ErrMsgs} -% \item \errindex{Not provable in Direct Predicate Calculus} -% \item \errindex{Found $n$ classical proof(s) but no intuitionistic one}\\ -% The decision procedure looks actually for classical proofs of the -% goals, and then checks that they are intuitionistic. In that case, -% classical proofs have been found, which do not correspond to -% intuitionistic ones. -% \end{ErrMsgs} \subsection{\tt congruence \tacindex{congruence} @@ -3630,802 +3954,587 @@ If the goal is a non-quantified equality, {\tt congruence} tries to prove it with non-quantified equalities in the context. Otherwise it tries to infer a discriminable equality from those in the context. Alternatively, congruence tries to prove that a hypothesis is equal to the goal or to the negation of another hypothesis. -{\tt congruence} is also able to take advantage of hypotheses stating quantified equalities, you have to provide a bound for the number of extra equalities generated that way. Please note that one of the members of the equality must contain all the quantified variables in order for {\tt congruence} to match against it. - -\begin{coq_eval} -Reset Initial. -Variable A:Set. -Variables a b:A. -Variable f:A->A. -Variable g:A->A->A. -\end{coq_eval} - -\begin{coq_example} -Theorem T: - a=(f a) -> (g b (f a))=(f (f a)) -> (g a b)=(f (g b a)) -> (g a b)=a. -intros. -congruence. -\end{coq_example} +{\tt congruence} is also able to take advantage of hypotheses stating quantified equalities, you have to provide a bound for the number of extra equalities generated that way. Please note that one of the members of the equality must contain all the quantified variables in order for {\tt congruence} to match against it. \begin{coq_eval} -Reset Initial. -Variable A:Set. -Variables a c d:A. -Variable f:A->A*A. -\end{coq_eval} - -\begin{coq_example} -Theorem inj : f = pair a -> Some (f c) = Some (f d) -> c=d. -intros. -congruence. -\end{coq_example} - -\begin{Variants} - \item {\tt congruence {\sl n}}\\ - Tries to add at most {\tt \sl n} instances of hypotheses stating quantified equalities to the problem in order to solve it. A bigger value of {\tt \sl n} does not make success slower, only failure. You might consider adding some lemmas as hypotheses using {\tt assert} in order for congruence to use them. - -\end{Variants} - -\begin{Variants} -\item {\tt congruence with \term$_1$ \dots\ \term$_n$}\\ - Adds {\tt \term$_1$ \dots\ \term$_n$} to the pool of terms used by - {\tt congruence}. This helps in case you have partially applied - constructors in your goal. -\end{Variants} - -\begin{ErrMsgs} - \item \errindex{I don't know how to handle dependent equality} \\ - The decision procedure managed to find a proof of the goal or of - a discriminable equality but this proof couldn't be built in {\Coq} - because of dependently-typed functions. - \item \errindex{I couldn't solve goal} \\ - The decision procedure didn't find any way to solve the goal. - \item \errindex{Goal is solvable by congruence but some arguments are missing. Try "congruence with \dots", replacing metavariables by arbitrary terms.} \\ - The decision procedure could solve the goal with the provision - that additional arguments are supplied for some partially applied - constructors. Any term of an appropriate type will allow the - tactic to successfully solve the goal. Those additional arguments - can be given to {\tt congruence} by filling in the holes in the - terms given in the error message, using the {\tt with} variant - described above. -\end{ErrMsgs} - -\subsection{\tt btauto -\tacindex{btauto} -\label{btauto}} - -The tactic \texttt{btauto} implements a reflexive solver for boolean tautologies. It -solves goals of the form {\tt t = u} where {\tt t} and {\tt u} are constructed -over the following grammar: - -$$\mathtt{t} ::= x \mid \mathtt{true} \mid \mathtt{false}\mid \mathtt{orb\ t_1\ t_2} -\mid \mathtt{andb\ t_1\ t_2} \mid\mathtt{xorb\ t_1\ t_2} \mid\mathtt{negb\ t} -\mid\mathtt{if\ t_1\ then\ t_2\ else\ t_3} -$$ - -Whenever the formula supplied is not a tautology, it also provides a counter-example. - -Internally, it uses a system very similar to the one of the {\tt ring} tactic. - -\subsection{\tt omega -\tacindex{omega} -\label{omega}} - -The tactic \texttt{omega}, due to Pierre Cr{\'e}gut, -is an automatic decision procedure for Presburger -arithmetic. It solves quantifier-free -formulas built with \verb|~|, \verb|\/|, \verb|/\|, -\verb|->| on top of equalities, inequalities and disequalities on -both the type \texttt{nat} of natural numbers and \texttt{Z} of binary -integers. This tactic must be loaded by the command \texttt{Require Import - Omega}. See the additional documentation about \texttt{omega} -(see Chapter~\ref{OmegaChapter}). - -\subsection{{\tt ring} and {\tt ring\_simplify \term$_1$ \dots\ \term$_n$} -\tacindex{ring} -\tacindex{ring\_simplify} -\comindex{Add Ring}} - -The {\tt 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) and comparing syntactically the -results. - -{\tt 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. - -See Chapter~\ref{ring} for more information on the tactic and how to -declare new ring structures. - -\subsection{{\tt field}, {\tt field\_simplify \term$_1$\dots\ \term$_n$} - and {\tt field\_simplify\_eq} -\tacindex{field} -\tacindex{field\_simplify} -\tacindex{field\_simplify\_eq} -\comindex{Add Field}} - -The {\tt field} tactic is built on the same ideas as {\tt ring}: this -is a reflexive tactic that solves or simplifies equations in a field -structure. The main idea is to reduce a field expression (which is an -extension of ring expressions with the inverse and division -operations) to a fraction made of two polynomial expressions. - -Tactic {\tt field} is used to solve subgoals, whereas {\tt - field\_simplify \term$_1$\dots\term$_n$} replaces the provided terms -by their reduced fraction. {\tt field\_simplify\_eq} applies when the -conclusion is an equation: it simplifies both hand sides and multiplies -so as to cancel 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 Chapter~\ref{ring} for more information on the tactic and how to -declare new field structures. - -\Example -\begin{coq_example*} -Require Import Reals. -Goal forall x y:R, - (x * y > 0)%R -> - (x * (1 / x + x / (x + y)))%R = - ((- 1 / y) * y * (- x * (x / (x + y)) - 1))%R. -\end{coq_example*} +Reset Initial. +Variable A:Set. +Variables a b:A. +Variable f:A->A. +Variable g:A->A->A. +\end{coq_eval} \begin{coq_example} -intros; field. +Theorem T: + a=(f a) -> (g b (f a))=(f (f a)) -> (g a b)=(f (g b a)) -> (g a b)=a. +intros. +congruence. \end{coq_example} \begin{coq_eval} Reset Initial. +Variable A:Set. +Variables a c d:A. +Variable f:A->A*A. \end{coq_eval} -\SeeAlso file {\tt plugins/setoid\_ring/RealField.v} for an example of instantiation,\\ -\phantom{\SeeAlso}theory {\tt theories/Reals} for many examples of use of {\tt -field}. +\begin{coq_example} +Theorem inj : f = pair a -> Some (f c) = Some (f d) -> c=d. +intros. +congruence. +\end{coq_example} -\subsection{\tt fourier -\tacindex{fourier}} +\begin{Variants} + \item {\tt congruence {\sl n}}\\ + Tries to add at most {\tt \sl n} instances of hypotheses stating quantified equalities to the problem in order to solve it. A bigger value of {\tt \sl n} does not make success slower, only failure. You might consider adding some lemmas as hypotheses using {\tt assert} in order for congruence to use them. -This tactic written by Lo{\"\i}c Pottier solves linear inequalities on -real numbers using Fourier's method~\cite{Fourier}. This tactic must -be loaded by {\tt Require Import Fourier}. +\end{Variants} -\Example -\begin{coq_example*} -Require Import Reals. -Require Import Fourier. -Goal forall x y:R, (x < y)%R -> (y + 1 >= x - 1)%R. -\end{coq_example*} +\begin{Variants} +\item {\tt congruence with \term$_1$ \dots\ \term$_n$}\\ + Adds {\tt \term$_1$ \dots\ \term$_n$} to the pool of terms used by + {\tt congruence}. This helps in case you have partially applied + constructors in your goal. +\end{Variants} -\begin{coq_example} -intros; fourier. -\end{coq_example} +\begin{ErrMsgs} + \item \errindex{I don't know how to handle dependent equality} \\ + The decision procedure managed to find a proof of the goal or of + a discriminable equality but this proof couldn't be built in {\Coq} + because of dependently-typed functions. + \item \errindex{I couldn't solve goal} \\ + The decision procedure didn't find any way to solve the goal. + \item \errindex{Goal is solvable by congruence but some arguments are missing. Try "congruence with \dots", replacing metavariables by arbitrary terms.} \\ + The decision procedure could solve the goal with the provision + that additional arguments are supplied for some partially applied + constructors. Any term of an appropriate type will allow the + tactic to successfully solve the goal. Those additional arguments + can be given to {\tt congruence} by filling in the holes in the + terms given in the error message, using the {\tt with} variant + described above. +\end{ErrMsgs} -\begin{coq_eval} -Reset Initial. -\end{coq_eval} +\section{Things that do not fit other sections} -\subsection{\tt autorewrite with \ident$_1$ \dots \ident$_n$. -\label{tactic:autorewrite} -\tacindex{autorewrite}} -This tactic \footnote{The behavior of this tactic has much changed compared to -the versions available in the previous distributions (V6). This may cause -significant changes in your theories to obtain the same result. As a drawback -of the re-engineering of the code, this tactic has also been completely revised -to get a very compact and readable version.} carries out rewritings according -the rewriting rule bases {\tt \ident$_1$ \dots \ident$_n$}. -Each rewriting rule of a base \ident$_i$ is applied to the main subgoal until -it fails. Once all the rules have been processed, if the main subgoal has -progressed (e.g., if it is distinct from the initial main goal) then the rules -of this base are processed again. If the main subgoal has not progressed then -the next base is processed. For the bases, the behavior is exactly similar to -the processing of the rewriting rules. -The rewriting rule bases are built with the {\tt Hint~Rewrite} vernacular -command. -\Warning{} This tactic may loop if you build non terminating rewriting systems. -\begin{Variant} -\item {\tt autorewrite with \ident$_1$ \dots \ident$_n$ using \tac}\\ -Performs, in the same way, all the rewritings of the bases {\tt \ident$_1$ $...$ -\ident$_n$} applying {\tt \tac} to the main subgoal after each rewriting step. -\item \texttt{autorewrite with {\ident$_1$} \dots \ident$_n$ in {\qualid}} - Performs all the rewritings in hypothesis {\qualid}. -\item \texttt{autorewrite with {\ident$_1$} \dots \ident$_n$ in {\qualid} using \tac} - Performs all the rewritings in hypothesis {\qualid} applying {\tt - \tac} to the main subgoal after each rewriting step. -\item \texttt{autorewrite with {\ident$_1$} \dots \ident$_n$ in \textit{clause}} - Performs all the rewritings in the clause \textit{clause}. \\ - The \textit{clause} argument must not contain any \texttt{type of} nor \texttt{value of}. -\end{Variant} -\SeeAlso Section~\ref{HintRewrite} for feeding the database of lemmas used by {\tt autorewrite}. -\SeeAlso Section~\ref{autorewrite-example} for examples showing the use of -this tactic. -% En attente d'un moyen de valoriser les fichiers de demos -%\SeeAlso file \texttt{contrib/Rocq/DEMOS/Demo\_AutoRewrite.v} -\section{Controlling automation} -\subsection{The hints databases for {\tt auto} and {\tt eauto} -\index{Hints databases} -\label{Hints-databases} -\comindex{Hint}} -The hints for \texttt{auto} and \texttt{eauto} are stored in -databases. Each database maps head symbols to a list of hints. One can -use the command \texttt{Print Hint \ident} to display the hints -associated to the head symbol \ident{} (see \ref{PrintHint}). Each -hint has a cost that is an nonnegative integer, and an optional pattern. -The hints with lower cost are tried first. A hint is tried by -\texttt{auto} when the conclusion of the current goal -matches its pattern or when it has no pattern. -\subsubsection*{Creating Hint databases - \label{CreateHintDb}\comindex{CreateHintDb}} -One can optionally declare a hint database using the command -\texttt{Create HintDb}. If a hint is added to an unknown database, it -will be automatically created. -\medskip -\texttt{Create HintDb} {\ident} [\texttt{discriminated}] -\medskip -This command creates a new database named \ident. -The database is implemented by a Discrimination Tree (DT) that serves as -an index of all the lemmas. The DT can use transparency information to decide -if a constant should be indexed or not (c.f. \ref{HintTransparency}), -making the retrieval more efficient. -The legacy implementation (the default one for new databases) uses the -DT only on goals without existentials (i.e., auto goals), for non-Immediate -hints and do not make use of transparency hints, putting more work on the -unification that is run after retrieval (it keeps a list of the lemmas -in case the DT is not used). The new implementation enabled by -the {\tt discriminated} option makes use of DTs in all cases and takes -transparency information into account. However, the order in which hints -are retrieved from the DT may differ from the order in which they were -inserted, making this implementation observationaly different from the -legacy one. -\begin{Variants} -\item\texttt{Local Hint} \textsl{hint\_definition} \texttt{:} - \ident$_1$ {\ldots} \ident$_n$ - - This is used to declare a hint database that must not be exported to the other - modules that require and import the current module. Inside a - section, the option {\tt Local} is useless since hints do not - survive anyway to the closure of sections. -\end{Variants} -The general -command to add a hint to some database \ident$_1$, \dots, \ident$_n$ is: -\begin{tabbing} - \texttt{Hint} \textsl{hint\_definition} \texttt{:} \ident$_1$ {\ldots} \ident$_n$ -\end{tabbing} -where {\sl hint\_definition} is one of the following expressions: -\begin{itemize} -\item \texttt{Resolve} {\term} - \comindex{Hint Resolve} - - This command adds {\tt apply {\term}} to the hint list - with the head symbol of the type of \term. The cost of that hint is - the number of subgoals generated by {\tt apply {\term}}. - - In case the inferred type of \term\ does not start with a product the - tactic added in the hint list is {\tt exact {\term}}. In case this - type can be reduced to a type starting with a product, the tactic {\tt - apply {\term}} is also stored in the hints list. - - If the inferred type of \term\ contains a dependent - quantification on a predicate, it is added to the hint list of {\tt - eapply} instead of the hint list of {\tt apply}. In this case, a - warning is printed since the hint is only used by the tactic {\tt - eauto} (see \ref{eauto}). A typical example of a hint that is used - only by \texttt{eauto} is a transitivity lemma. - \begin{ErrMsgs} - \item \errindex{Bound head variable} - The head symbol of the type of {\term} is a bound variable such - that this tactic cannot be associated to a constant. - \item \term\ \errindex{cannot be used as a hint} - The type of \term\ contains products over variables which do not - appear in the conclusion. A typical example is a transitivity axiom. - In that case the {\tt apply} tactic fails, and thus is useless. - \end{ErrMsgs} - \begin{Variants} - \item \texttt{Resolve} {\term$_1$} \dots {\term$_m$} - Adds each \texttt{Resolve} {\term$_i$}. - \end{Variants} -\item \texttt{Immediate {\term}} -\comindex{Hint Immediate} - - This command adds {\tt apply {\term}; trivial} to the hint list - associated with the head symbol of the type of {\ident} in the given - database. This tactic will fail if all the subgoals generated by - {\tt apply {\term}} are not solved immediately by the {\tt trivial} - tactic (which only tries tactics with cost $0$). - - This command is useful for theorems such as the symmetry of equality - or $n+1=m+1 \to n=m$ 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 {\tt trivial} itself. - \begin{ErrMsgs} - \item \errindex{Bound head variable} +\section{Everything after this point has yet to be sorted} - \item \term\ \errindex{cannot be used as a hint} - \end{ErrMsgs} +\subsection{\tt constr\_eq \term$_1$ \term$_2$ +\tacindex{constr\_eq} +\label{constreq}} - \begin{Variants} +This tactic applies to any goal. It checks whether its arguments are +equal modulo alpha conversion and casts. - \item \texttt{Immediate} {\term$_1$} \dots {\term$_m$} +\ErrMsg \errindex{Not equal} - Adds each \texttt{Immediate} {\term$_i$}. +\subsection{\tt unify \term$_1$ \term$_2$ +\tacindex{unify} +\label{unify}} - \end{Variants} +This tactic applies to any goal. It checks whether its arguments are +unifiable, potentially instantiating existential variables. -\item \texttt{Constructors} {\ident} -\comindex{Hint Constructors} - - If {\ident} is an inductive type, this command adds all its - constructors as hints of type \texttt{Resolve}. Then, when the - conclusion of current goal has the form \texttt{({\ident} \dots)}, - \texttt{auto} will try to apply each constructor. +\ErrMsg \errindex{Not unifiable} - \begin{ErrMsgs} +\begin{Variants} +\item {\tt unify \term$_1$ \term$_2$ with \ident} - \item {\ident} \errindex{is not an inductive type} + Unification takes the transparency information defined in the + hint database {\tt \ident} into account (see Section~\ref{HintTransparency}). +\end{Variants} - \item {\ident} \errindex{not declared} +\subsection{\tt is\_evar \term +\tacindex{is\_evar} +\label{isevar}} - \end{ErrMsgs} +This tactic applies to any goal. It checks whether its argument is an +existential variable. Existential variables are uninstantiated +variables generated by e.g. {\tt eapply} (see Section~\ref{apply}). - \begin{Variants} +\ErrMsg \errindex{Not an evar} - \item \texttt{Constructors} {\ident$_1$} \dots {\ident$_m$} +\subsection{\tt has\_evar \term +\tacindex{has\_evar} +\label{hasevar}} - Adds each \texttt{Constructors} {\ident$_i$}. +This tactic applies to any goal. It checks whether its argument has an +existential variable as a subterm. Unlike {\tt context} patterns +combined with {\tt is\_evar}, this tactic scans all subterms, +including those under binders. - \end{Variants} +\ErrMsg \errindex{No evars} -\item \texttt{Unfold} {\qualid} -\comindex{Hint Unfold} - - This adds the tactic {\tt unfold {\qualid}} to the hint list that - will only be used when the head constant of the goal is \ident. Its - cost is 4. +\subsection{\tt is\_var \term +\tacindex{is\_var} +\label{isvar}} + +This tactic applies to any goal. It checks whether its argument is a +variable or hypothesis in the current goal context or in the opened sections. + +\ErrMsg \errindex{Not a variable or hypothesis} + +\section{Equality} + +\subsection{\tt f\_equal +\label{f-equal} +\tacindex{f\_equal}} + +This tactic applies to a goal of the form $f\ a_1\ \ldots\ a_n = f'\ +a'_1\ \ldots\ a'_n$. Using {\tt f\_equal} on such a goal leads to +subgoals $f=f'$ and $a_1=a'_1$ and so on up to $a_n=a'_n$. Amongst +these subgoals, the simple ones (e.g. provable by +reflexivity or congruence) are automatically solved by {\tt f\_equal}. + + +\section{Equality and inductive sets} - \begin{Variants} +We describe in this section some special purpose tactics dealing with +equality and inductive sets or types. These tactics use the equality +{\tt eq:forall (A:Type), A->A->Prop}, simply written with the +infix symbol {\tt =}. - \item \texttt{Unfold} {\ident$_1$} \dots {\ident$_m$} +\subsection{\tt decide equality +\label{decideequality} +\tacindex{decide equality}} - Adds each \texttt{Unfold} {\ident$_i$}. +This tactic solves a goal of the form +{\tt forall $x$ $y$:$R$, \{$x$=$y$\}+\{\verb|~|$x$=$y$\}}, where $R$ +is an inductive type such that its constructors do not take proofs or +functions as arguments, nor objects in dependent types. +It solves goals of the form {\tt \{$x$=$y$\}+\{\verb|~|$x$=$y$\}} as well. - \end{Variants} +\subsection{\tt compare \term$_1$ \term$_2$ +\tacindex{compare}} -\item \texttt{Transparent}, \texttt{Opaque} {\qualid} -\label{HintTransparency} -\comindex{Hint Transparent} -\comindex{Hint Opaque} - - This adds a transparency hint to the database, making {\tt {\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 \texttt{discriminated} databases. - - \begin{Variants} +This tactic compares two given objects \term$_1$ and \term$_2$ +of an inductive datatype. If $G$ is the current goal, it leaves the sub-goals +\term$_1${\tt =}\term$_2$ {\tt ->} $G$ and \verb|~|\term$_1${\tt =}\term$_2$ +{\tt ->} $G$. The type +of \term$_1$ and \term$_2$ must satisfy the same restrictions as in the tactic +\texttt{decide equality}. - \item \texttt{Transparent}, \texttt{Opaque} {\ident$_1$} \dots {\ident$_m$} +\subsection{\tt simplify\_eq {\term} +\tacindex{simplify\_eq} +\tacindex{esimplify\_eq} +\label{simplify-eq}} - Declares each {\ident$_i$} as a transparent or opaque constant. - - \end{Variants} +Let {\term} be the proof of a statement of conclusion {\tt + {\term$_1$}={\term$_2$}}. If {\term$_1$} and +{\term$_2$} are structurally different (in the sense described for the +tactic {\tt discriminate}), then the tactic {\tt simplify\_eq} behaves as {\tt + discriminate {\term}}, otherwise it behaves as {\tt injection + {\term}}. -\item \texttt{Extern \num\ [\pattern]\ => }\textsl{tactic} -\comindex{Hint Extern} +\Rem If some quantified hypothesis of the goal is named {\ident}, then +{\tt simplify\_eq {\ident}} first introduces the hypothesis in the local +context using \texttt{intros until \ident}. - This hint type is to extend \texttt{auto} with tactics other than - \texttt{apply} and \texttt{unfold}. For that, we must specify a - cost, an optional pattern and a tactic to execute. Here is an example: +\begin{Variants} +\item \texttt{simplify\_eq} \num -\begin{quotation} -\begin{verbatim} -Hint Extern 4 (~(_ = _)) => discriminate. -\end{verbatim} -\end{quotation} + This does the same thing as \texttt{intros until \num} then +\texttt{simplify\_eq \ident} where {\ident} is the identifier for the last +introduced hypothesis. - Now, when the head of the goal is a disequality, \texttt{auto} will - try \texttt{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 ident, like - \texttt{?X1} or \texttt{?X2}. Here is an example: +\item \texttt{simplify\_eq} \term{} {\tt with} {\bindinglist} -% Require EqDecide. -\begin{coq_example*} -Require Import List. -\end{coq_example*} -\begin{coq_example} -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 auto with eqdec. -\end{coq_example} -\begin{coq_eval} -Abort. -\end{coq_eval} + This does the same as \texttt{simplify\_eq {\term}} but using + the given bindings to instantiate parameters or hypotheses of {\term}. -\end{itemize} +\item \texttt{esimplify\_eq} \num\\ + \texttt{esimplify\_eq} \term{} \zeroone{{\tt with} {\bindinglist}} -\Rem One can use an \texttt{Extern} hint with no pattern to do -pattern-matching on hypotheses using \texttt{match goal with} inside -the tactic. + This works the same as {\tt simplify\_eq} but if the type of {\term}, + or the type of the hypothesis referred to by {\num}, has uninstantiated + parameters, these parameters are left as existential variables. -\begin{Variants} -\item \texttt{Hint} \textsl{hint\_definition} - - No database name is given: the hint is registered in the {\tt core} - database. +\item{\tt simplify\_eq} -\item\texttt{Local Hint} \textsl{hint\_definition} \texttt{:} - \ident$_1$ {\ldots} \ident$_n$ +If the current goal has form $t_1\verb=<>=t_2$, it behaves as +\texttt{intro {\ident}; simplify\_eq {\ident}}. +\end{Variants} - 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 {\tt Local} is useless since hints do not - survive anyway to the closure of sections. +\subsection{\tt dependent rewrite -> {\ident} +\tacindex{dependent rewrite ->} +\label{dependent-rewrite}} -\item\texttt{Local Hint} \textsl{hint\_definition} +This tactic applies to any goal. If \ident\ has type +\verb+(existT B a b)=(existT B a' b')+ +in the local context (i.e. each term of the +equality has a sigma type $\{ a:A~ \&~(B~a)\}$) this tactic rewrites +\verb+a+ into \verb+a'+ and \verb+b+ into \verb+b'+ in the current +goal. This tactic works even if $B$ is also a sigma type. This kind +of equalities between dependent pairs may be derived by the injection +and inversion tactics. - Idem for the {\tt core} database. - +\begin{Variants} +\item{\tt dependent rewrite <- {\ident}} +\tacindex{dependent rewrite <-} \\ +Analogous to {\tt dependent rewrite ->} but uses the equality from +right to left. \end{Variants} -% There are shortcuts that allow to define several goal at once: +\section{Inversion +\label{inversion}} -% \begin{itemize} -% \item \comindex{Hints Resolve}\texttt{Hints Resolve \ident$_1$ \dots\ \ident$_n$ : \ident.}\\ -% This command is a shortcut for the following ones: -% \begin{quotation} -% \noindent\texttt{Hint \ident$_1$ : \ident\ := Resolve \ident$_1$}\\ -% \dots\\ -% \texttt{Hint \ident$_1$ : \ident := Resolve \ident$_1$} -% \end{quotation} -% Notice that the hint name is the same that the theorem given as -% hint. -% \item \comindex{Hints Immediate}\texttt{Hints Immediate \ident$_1$ \dots\ \ident$_n$ : \ident.}\\ -% \item \comindex{Hints Unfold}\texttt{Hints Unfold \qualid$_1$ \dots\ \qualid$_n$ : \ident.}\\ -% \end{itemize} +\subsection[\tt functional inversion \ident]{\tt functional inversion \ident\label{sec:functional-inversion}} -%\begin{Warnings} -% \item \texttt{Overriding hint named \dots\ in database \dots} -%\end{Warnings} +\texttt{functional inversion} is a \emph{highly} experimental tactic +which performs inversion on hypothesis \ident\ of the form +\texttt{\qualid\ \term$_1$\dots\term$_n$\ = \term} or \texttt{\term\ = + \qualid\ \term$_1$\dots\term$_n$} where \qualid\ must have been +defined using \texttt{Function} (see Section~\ref{Function}). +\begin{ErrMsgs} +\item \errindex{Hypothesis {\ident} must contain at least one Function} +\item \errindex{Cannot find inversion information for hypothesis \ident} + This error may be raised when some inversion lemma failed to be + generated by Function. +\end{ErrMsgs} +\begin{Variants} +\item {\tt functional inversion \num} -\subsection{Hint databases defined in the \Coq\ standard library} + This does the same thing as \texttt{intros until \num} then + \texttt{functional inversion \ident} where {\ident} is the + identifier for the last introduced hypothesis. +\item {\tt functional inversion \ident\ \qualid}\\ + {\tt functional inversion \num\ \qualid} -Several hint databases are defined in the \Coq\ standard library. The -actual content of a database is the collection of the hints declared -to belong to this database in each of the various modules currently -loaded. Especially, requiring new modules potentially extend a -database. At {\Coq} startup, only the {\tt core} and {\tt v62} -databases are non empty and can be used. + In case the hypothesis {\ident} (or {\num}) has a type of the form + \texttt{\qualid$_1$\ \term$_1$\dots\term$_n$\ =\ \qualid$_2$\ + \term$_{n+1}$\dots\term$_{n+m}$} where \qualid$_1$ and \qualid$_2$ + are valid candidates to functional inversion, this variant allows to + choose which must be inverted. +\end{Variants} -\begin{description} -\item[\tt core] This special database is automatically used by - \texttt{auto}, except when pseudo-database \texttt{nocore} is - given to \texttt{auto}. The \texttt{core} database contains - only basic lemmas about negation, - conjunction, and so on from. Most of the hints in this database come - from the \texttt{Init} and \texttt{Logic} directories. -\item[\tt arith] This database contains all lemmas about Peano's - arithmetic proved in the directories \texttt{Init} and - \texttt{Arith} +\subsection{\tt quote \ident +\tacindex{quote} +\index{2-level approach}} -\item[\tt zarith] contains lemmas about binary signed integers from - the directories \texttt{theories/ZArith}. When required, the module - {\tt Omega} also extends the database {\tt zarith} with a high-cost - hint that calls {\tt omega} on equations and inequalities in {\tt - nat} or {\tt Z}. +This kind of inversion has nothing to do with the tactic +\texttt{inversion} above. This tactic does \texttt{change (\ident\ + t)}, where \texttt{t} is a term built in order to ensure the +convertibility. In other words, it does inversion of the function +\ident. This function must be a fixpoint on a simple recursive +datatype: see~\ref{quote-examples} for the full details. -\item[\tt bool] contains lemmas about booleans, mostly from directory - \texttt{theories/Bool}. +\begin{ErrMsgs} +\item \errindex{quote: not a simple fixpoint}\\ + Happens when \texttt{quote} is not able to perform inversion properly. +\end{ErrMsgs} -\item[\tt datatypes] is for lemmas about lists, streams and so on that - are mainly proved in the \texttt{Lists} subdirectory. +\begin{Variants} +\item \texttt{quote {\ident} [ \ident$_1$ \dots \ident$_n$ ]}\\ + All terms that are built only with \ident$_1$ \dots \ident$_n$ will be + considered by \texttt{quote} as constants rather than variables. +\end{Variants} -\item[\tt sets] contains lemmas about sets and relations from the - directories \texttt{Sets} and \texttt{Relations}. +% En attente d'un moyen de valoriser les fichiers de demos +% \SeeAlso file \texttt{theories/DEMOS/DemoQuote.v} in the distribution -\item[\tt typeclass\_instances] contains all the type class instances - declared in the environment, including those used for \texttt{setoid\_rewrite}, - from the \texttt{Classes} directory. -\end{description} +\section[Classical tactics]{Classical tactics\label{ClassicalTactics}} -There is also a special database called {\tt v62}. It collects all -hints that were declared in the versions of {\Coq} prior to version -6.2.4 when the databases {\tt core}, {\tt arith}, and so on were -introduced. The purpose of the database {\tt v62} is to ensure -compatibility with further versions of {\Coq} for developments done in -versions prior to 6.2.4 ({\tt auto} being replaced by {\tt auto with v62}). -The database {\tt v62} is intended not to be extended (!). It is not -included in the hint databases list used in the {\tt auto with *} tactic. +In order to ease the proving process, when the {\tt Classical} module is loaded. A few more tactics are available. Make sure to load the module using the \texttt{Require Import} command. -Furthermore, you are advised not to put your own hints in the -{\tt core} database, but use one or several databases specific to your -development. +\subsection{{\tt classical\_left, classical\_right} \tacindex{classical\_left} \tacindex{classical\_right}} -\subsection{\tt Print Hint -\label{PrintHint} -\comindex{Print Hint}} +The tactics \texttt{classical\_left} and \texttt{classical\_right} are the analog of the \texttt{left} and \texttt{right} but using classical logic. They can only be used for disjunctions. +Use \texttt{classical\_left} to prove the left part of the disjunction with the assumption that the negation of right part holds. +Use \texttt{classical\_right} to prove the right part of the disjunction with the assumption that the negation of left part holds. -This command displays all hints that apply to the current goal. It -fails if no proof is being edited, while the two variants can be used at -every moment. +\section{Automatizing +\label{Automatizing}} -\begin{Variants} +% EXISTE ENCORE ? +% +% \subsection{\tt Prolog [ \term$_1$ \dots\ \term$_n$ ] \num} +% \tacindex{Prolog}\label{Prolog} +% This tactic, implemented by Chet Murthy, is based upon the concept of +% existential variables of Gilles Dowek, stating that resolution is a +% kind of unification. It tries to solve the current goal using the {\tt +% Assumption} tactic, the {\tt intro} tactic, and applying hypotheses +% of the local context and terms of the given list {\tt [ \term$_1$ +% \dots\ \term$_n$\ ]}. It is more powerful than {\tt auto} since it +% may apply to any theorem, even those of the form {\tt (x:A)(P x) -> Q} +% where {\tt x} does not appear free in {\tt Q}. The maximal search +% depth is {\tt \num}. -\item {\tt Print Hint {\ident} } +% \begin{ErrMsgs} +% \item \errindex{Prolog failed}\\ +% The Prolog tactic was not able to prove the subgoal. +% \end{ErrMsgs} + + +%% \subsection{{\tt jp} {\em (Jprover)} +%% \tacindex{jp} +%% \label{jprover}} - This command displays only tactics associated with \ident\ in the - hints list. This is independent of the goal being edited, so this - command will not fail if no goal is being edited. +%% The tactic \texttt{jp}, due to Huang Guan-Shieng, is an experimental +%% port of the {\em Jprover}\cite{SLKN01} semi-decision procedure for +%% first-order intuitionistic logic implemented in {\em +%% NuPRL}\cite{Kre02}. -\item {\tt Print Hint *} +%% The tactic \texttt{jp}, due to Huang Guan-Shieng, is an {\it +%% experimental} port of the {\em Jprover}\cite{SLKN01} semi-decision +%% procedure for first-order intuitionistic logic implemented in {\em +%% NuPRL}\cite{Kre02}. - This command displays all declared hints. +%% Search may optionnaly be bounded by a multiplicity parameter +%% indicating how many (at most) copies of a formula may be used in +%% the proof process, its absence may lead to non-termination of the tactic. -\item {\tt Print HintDb {\ident} } -\label{PrintHintDb} -\comindex{Print HintDb} +%% %\begin{coq_eval} +%% %Variable S:Set. +%% %Variables P Q:S->Prop. +%% %Variable f:S->S. +%% %\end{coq_eval} - This command displays all hints from database \ident. +%% %\begin{coq_example*} +%% %Lemma example: (exists x |P x\/Q x)->(exists x |P x)\/(exists x |Q x). +%% %jp. +%% %Qed. -\end{Variants} +%% %Lemma example2: (forall x ,P x->P (f x))->forall x,P x->P (f(f x)). +%% %jp. +%% %Qed. +%% %\end{coq_example*} -\subsection{\tt Hint Rewrite \term$_1$ \dots \term$_n$ : \ident -\label{HintRewrite} -\comindex{Hint Rewrite}} +%% \begin{Variants} +%% \item {\tt jp $n$}\\ +%% \tacindex{jp $n$} +%% Tries the {\em Jprover} procedure with multiplicities up to $n$, +%% starting from 1. +%% \item {\tt jp}\\ +%% Tries the {\em Jprover} procedure without multiplicity bound, +%% possibly running forever. +%% \end{Variants} -This vernacular command adds the terms {\tt \term$_1$ \dots \term$_n$} -(their types must be equalities) in the rewriting base {\tt \ident} -with the default orientation (left to right). Notice that the -rewriting bases are distinct from the {\tt auto} hint bases and that -{\tt auto} does not take them into account. +%% \begin{ErrMsgs} +%% \item \errindex{multiplicity limit reached}\\ +%% The procedure tried all multiplicities below the limit and +%% failed. Goal might be solved by increasing the multiplicity limit. +%% \item \errindex{formula is not provable}\\ +%% The procedure determined that goal was not provable in +%% intuitionistic first-order logic, no matter how big the +%% multiplicity is. +%% \end{ErrMsgs} -This command is synchronous with the section mechanism (see \ref{Section}): -when closing a section, all aliases created by \texttt{Hint Rewrite} in that -section are lost. Conversely, when loading a module, all \texttt{Hint Rewrite} -declarations at the global level of that module are loaded. -\begin{Variants} -\item {\tt Hint Rewrite -> \term$_1$ \dots \term$_n$ : \ident}\\ -This is strictly equivalent to the command above (we only make explicit the -orientation which otherwise defaults to {\tt ->}). +% \subsection[\tt Linear]{\tt Linear\tacindex{Linear}\label{Linear}} +% The tactic \texttt{Linear}, due to Jean-Christophe Filli{\^a}atre +% \cite{Fil94}, implements a decision procedure for {\em Direct +% Predicate Calculus}, that is first-order Gentzen's Sequent Calculus +% without contraction rules \cite{KeWe84,BeKe92}. Intuitively, a +% first-order goal is provable in Direct Predicate Calculus if it can be +% proved using each hypothesis at most once. -\item {\tt Hint Rewrite <- \term$_1$ \dots \term$_n$ : \ident}\\ -Adds the rewriting rules {\tt \term$_1$ \dots \term$_n$} with a right-to-left -orientation in the base {\tt \ident}. +% Unlike the previous tactics, the \texttt{Linear} tactic does not belong +% to the initial state of the system, and it must be loaded explicitly +% with the command -\item {\tt Hint Rewrite \term$_1$ \dots \term$_n$ using {\tac} : {\ident}}\\ -When the rewriting rules {\tt \term$_1$ \dots \term$_n$} in {\tt \ident} will -be used, the tactic {\tt \tac} will be applied to the generated subgoals, the -main subgoal excluded. +% \begin{coq_example*} +% Require Linear. +% \end{coq_example*} -%% \item -%% {\tt Hint Rewrite [ \term$_1$ \dots \term$_n$ ] in \ident}\\ -%% {\tt Hint Rewrite [ \term$_1$ \dots \term$_n$ ] in {\ident} using {\tac}}\\ -%% These are deprecated syntactic variants for -%% {\tt Hint Rewrite \term$_1$ \dots \term$_n$ : \ident} and -%% {\tt Hint Rewrite \term$_1$ \dots \term$_n$ using {\tac} : {\ident}}. +% For instance, assuming that \texttt{even} and \texttt{odd} are two +% predicates on natural numbers, and \texttt{a} of type \texttt{nat}, the +% tactic \texttt{Linear} solves the following goal -\item \texttt{Print Rewrite HintDb {\ident}} +% \begin{coq_eval} +% Variables even,odd : nat -> Prop. +% Variable a:nat. +% \end{coq_eval} - This command displays all rewrite hints contained in {\ident}. +% \begin{coq_example*} +% Lemma example : (even a) +% -> ((x:nat)((even x)->(odd (S x)))) +% -> (EX y | (odd y)). +% \end{coq_example*} -\end{Variants} +% You can find examples of the use of \texttt{Linear} in +% \texttt{theories/DEMOS/DemoLinear.v}. +% \begin{coq_eval} +% Abort. +% \end{coq_eval} -\subsection{Hints and sections -\label{Hint-and-Section}} +% \begin{Variants} +% \item {\tt Linear with \ident$_1$ \dots\ \ident$_n$}\\ +% \tacindex{Linear with} +% Is equivalent to apply first {\tt generalize \ident$_1$ \dots +% \ident$_n$} (see Section~\ref{generalize}) then the \texttt{Linear} +% tactic. So one can use axioms, lemmas or hypotheses of the local +% context with \texttt{Linear} in this way. +% \end{Variants} -Hints provided by the \texttt{Hint} commands are erased when closing a -section. Conversely, all hints of a module \texttt{A} that are not -defined inside a section (and not defined with option {\tt Local}) become -available when the module {\tt A} is imported (using -e.g. \texttt{Require Import A.}). +% \begin{ErrMsgs} +% \item \errindex{Not provable in Direct Predicate Calculus} +% \item \errindex{Found $n$ classical proof(s) but no intuitionistic one}\\ +% The decision procedure looks actually for classical proofs of the +% goals, and then checks that they are intuitionistic. In that case, +% classical proofs have been found, which do not correspond to +% intuitionistic ones. +% \end{ErrMsgs} -\subsection{Setting implicit automation tactics} -\subsubsection[\tt Proof with {\tac}.]{\tt Proof with {\tac}.\label{ProofWith} -\comindex{Proof with}} +\subsection{\tt btauto +\tacindex{btauto} +\label{btauto}} - This command may be used to start a proof. It defines a default - tactic to be used each time a tactic command {\tac$_1$} is ended by - ``\verb#...#''. In this case the tactic command typed by the user is - equivalent to \tac$_1$;{\tac}. +The tactic \texttt{btauto} implements a reflexive solver for boolean tautologies. It +solves goals of the form {\tt t = u} where {\tt t} and {\tt u} are constructed +over the following grammar: -\SeeAlso {\tt Proof.} in Section~\ref{BeginProof}. +$$\mathtt{t} ::= x \mid \mathtt{true} \mid \mathtt{false}\mid \mathtt{orb\ t_1\ t_2} +\mid \mathtt{andb\ t_1\ t_2} \mid\mathtt{xorb\ t_1\ t_2} \mid\mathtt{negb\ t} +\mid\mathtt{if\ t_1\ then\ t_2\ else\ t_3} +$$ -\begin{Variants} -\item {\tt Proof with {\tac} using {\ident$_1$ \dots {\ident$_n$}}} - Combines in a single line {\tt Proof with} and {\tt Proof using}, - see~\ref{ProofUsing} -\item {\tt Proof using {\ident$_1$ \dots {\ident$_n$}} with {\tac}} - Combines in a single line {\tt Proof with} and {\tt Proof using}, - see~\ref{ProofUsing} +Whenever the formula supplied is not a tautology, it also provides a counter-example. -\end{Variants} +Internally, it uses a system very similar to the one of the {\tt ring} tactic. -\subsubsection[\tt Declare Implicit Tactic {\tac}.]{\tt Declare Implicit Tactic {\tac}.\comindex{Declare Implicit Tactic}} +\subsection{\tt omega +\tacindex{omega} +\label{omega}} -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. +The tactic \texttt{omega}, due to Pierre Cr{\'e}gut, +is an automatic decision procedure for Presburger +arithmetic. It solves quantifier-free +formulas built with \verb|~|, \verb|\/|, \verb|/\|, +\verb|->| on top of equalities, inequalities and disequalities on +both the type \texttt{nat} of natural numbers and \texttt{Z} of binary +integers. This tactic must be loaded by the command \texttt{Require Import + Omega}. See the additional documentation about \texttt{omega} +(see Chapter~\ref{OmegaChapter}). -Here is an example: +\subsection{{\tt ring} and {\tt ring\_simplify \term$_1$ \dots\ \term$_n$} +\tacindex{ring} +\tacindex{ring\_simplify} +\comindex{Add Ring}} -\begin{coq_example} -Parameter quo : nat -> forall n:nat, n<>0 -> nat. -Notation "x // y" := (quo x y _) (at level 40). +The {\tt 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) and comparing syntactically the +results. -Declare Implicit Tactic assumption. -Goal forall n m, m<>0 -> { q:nat & { r | q * m + r = n } }. -intros. -exists (n // m). -\end{coq_example} +{\tt 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 {\tt exists (n // m)} did not fail. The hole was solved by -{\tt assumption} so that it behaved as {\tt exists (quo n m H)}. +See Chapter~\ref{ring} for more information on the tactic and how to +declare new ring structures. -\section{Generation of induction principles with {\tt Scheme} -\label{Scheme} -\index{Schemes} -\comindex{Scheme}} +\subsection{{\tt field}, {\tt field\_simplify \term$_1$\dots\ \term$_n$} + and {\tt field\_simplify\_eq} +\tacindex{field} +\tacindex{field\_simplify} +\tacindex{field\_simplify\_eq} +\comindex{Add Field}} -The {\tt Scheme} command is a high-level tool for generating -automatically (possibly mutual) induction principles for given types -and sorts. Its syntax follows the schema: -\begin{quote} -{\tt Scheme {\ident$_1$} := Induction for \ident'$_1$ Sort {\sort$_1$} \\ - with\\ - \mbox{}\hspace{0.1cm} \dots\\ - with {\ident$_m$} := Induction for {\ident'$_m$} Sort - {\sort$_m$}} -\end{quote} -where \ident'$_1$ \dots\ \ident'$_m$ are different inductive type -identifiers belonging to the same package of mutual inductive -definitions. This command generates {\ident$_1$}\dots{} {\ident$_m$} -to be mutually recursive definitions. Each term {\ident$_i$} proves a -general principle of mutual induction for objects in type {\term$_i$}. +The {\tt field} tactic is built on the same ideas as {\tt ring}: this +is a reflexive tactic that solves or simplifies equations in a field +structure. The main idea is to reduce a field expression (which is an +extension of ring expressions with the inverse and division +operations) to a fraction made of two polynomial expressions. -\begin{Variants} -\item {\tt Scheme {\ident$_1$} := Minimality for \ident'$_1$ Sort {\sort$_1$} \\ - with\\ - \mbox{}\hspace{0.1cm} \dots\ \\ - with {\ident$_m$} := Minimality for {\ident'$_m$} Sort - {\sort$_m$}} +Tactic {\tt field} is used to solve subgoals, whereas {\tt + field\_simplify \term$_1$\dots\term$_n$} replaces the provided terms +by their reduced fraction. {\tt field\_simplify\_eq} applies when the +conclusion is an equation: it simplifies both hand sides and multiplies +so as to cancel denominators. So it produces an equation without +division nor inverse. - Same as before but defines a non-dependent elimination principle more - natural in case of inductively defined relations. +All of these 3 tactics may generate a subgoal in order to prove that +denominators are different from zero. -\item {\tt Scheme Equality for \ident$_1$\comindex{Scheme Equality}} +See Chapter~\ref{ring} for more information on the tactic and how to +declare new field structures. - Tries to generate a boolean equality and a proof of the - decidability of the usual equality. If \ident$_i$ involves - some other inductive types, their equality has to be defined first. +\Example +\begin{coq_example*} +Require Import Reals. +Goal forall x y:R, + (x * y > 0)%R -> + (x * (1 / x + x / (x + y)))%R = + ((- 1 / y) * y * (- x * (x / (x + y)) - 1))%R. +\end{coq_example*} -\item {\tt Scheme Induction for \ident$_1$ Sort {\sort$_1$} \\ - with\\ - \mbox{}\hspace{0.1cm} \dots\\ - with Induction for {\ident$_m$} Sort - {\sort$_m$}} +\begin{coq_example} +intros; field. +\end{coq_example} - If you do not provide the name of the schemes, they will be automatically - computed from the sorts involved (works also with Minimality). +\begin{coq_eval} +Reset Initial. +\end{coq_eval} -\end{Variants} +\SeeAlso file {\tt plugins/setoid\_ring/RealField.v} for an example of instantiation,\\ +\phantom{\SeeAlso}theory {\tt theories/Reals} for many examples of use of {\tt +field}. -\SeeAlso Section~\ref{Scheme-examples} - -\subsection{Automatic declaration of schemes} -\comindex{Set Equality Schemes} -\comindex{Set Elimination Schemes} -It is possible to deactivate the automatic declaration of the induction - principles when defining a new inductive type with the - {\tt Unset Elimination Schemes} command. It may be -reactivated at any time with {\tt Set Elimination Schemes}. -\\ - -You can also activate the automatic declaration of those boolean equalities -(see the second variant of {\tt Scheme}) with the {\tt Set Equality Schemes} - command. 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. - -\subsection{\tt Combined Scheme\label{CombinedScheme} -\comindex{Combined Scheme}} -The {\tt Combined Scheme} command is a tool for combining -induction principles generated by the {\tt Scheme} command. -Its syntax follows the schema : - -\noindent -{\tt Combined Scheme {\ident$_0$} from {\ident$_1$}, .., {\ident$_n$}}\\ -\ident$_1$ {\ldots} \ident$_n$ are different inductive principles that must belong to -the same package of mutual inductive principle definitions. This command -generates {\ident$_0$} to be the conjunction of the principles: it is -built from the common premises of the principles and concluded by the -conjunction of their conclusions. - -\SeeAlso Section~\ref{CombinedScheme-examples} - -\section{Generation of induction principles with {\tt Functional Scheme} -\label{FunScheme} -\comindex{Functional Scheme}} - -The {\tt Functional Scheme} command is a high-level experimental -tool for generating automatically induction principles -corresponding to (possibly mutually recursive) functions. Its -syntax follows the schema: -\begin{quote} -{\tt Functional Scheme {\ident$_1$} := Induction for \ident'$_1$ Sort {\sort$_1$} \\ - with\\ - \mbox{}\hspace{0.1cm} \dots\ \\ - with {\ident$_m$} := Induction for {\ident'$_m$} Sort - {\sort$_m$}} -\end{quote} -where \ident'$_1$ \dots\ \ident'$_m$ are different mutually defined function -names (they must be in the same order as when they were defined). -This command generates the induction principles -\ident$_1$\dots\ident$_m$, following the recursive structure and case -analyses of the functions \ident'$_1$ \dots\ \ident'$_m$. +\subsection{\tt fourier +\tacindex{fourier}} +This tactic written by Lo{\"\i}c Pottier solves linear inequalities on +real numbers using Fourier's method~\cite{Fourier}. This tactic must +be loaded by {\tt Require Import Fourier}. -\paragraph{\texttt{Functional Scheme}} -There is a difference between obtaining an induction scheme by using -\texttt{Functional Scheme} on a function defined by \texttt{Function} -or not. Indeed \texttt{Function} generally produces smaller -principles, closer to the definition written by the user. +\Example +\begin{coq_example*} +Require Import Reals. +Require Import Fourier. +Goal forall x y:R, (x < y)%R -> (y + 1 >= x - 1)%R. +\end{coq_example*} +\begin{coq_example} +intros; fourier. +\end{coq_example} -\SeeAlso Section~\ref{FunScheme-examples} +\begin{coq_eval} +Reset Initial. +\end{coq_eval} \section{Simple tactic macros @@ -4433,7 +4542,7 @@ principles, closer to the definition written by the user. \comindex{Tactic Definition} \label{TacticDefinition}} -A simple example has more value than a long explanation: +A simple example has more value than a long explanation: \begin{coq_example} Ltac Solve := simpl; intros; auto. @@ -4443,7 +4552,7 @@ Ltac ElimBoolRewrite b H1 H2 := 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{Section}) +when you close the section (see also \ref{Section}) 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. @@ -4452,8 +4561,8 @@ Chapter~\ref{TacticLanguage} gives examples of more complex user-defined tactics. -%%% Local Variables: +%%% Local Variables: %%% mode: latex %%% TeX-master: "Reference-Manual" %%% TeX-master: "Reference-Manual" -%%% End: +%%% End: diff --git a/doc/refman/RefMan-tacex.tex b/doc/refman/RefMan-tacex.tex index 91ff3d5ece..463e2b81a5 100644 --- a/doc/refman/RefMan-tacex.tex +++ b/doc/refman/RefMan-tacex.tex @@ -3,590 +3,6 @@ This chapter presents detailed examples of certain tactics, to illustrate their behavior. -\section[\tt refine]{\tt refine\tacindex{refine} -\label{refine-example}} - -This tactic applies to any goal. It behaves like {\tt exact} with a -big difference : the user can leave some holes (denoted by \texttt{\_} or -{\tt (\_:}{\it type}{\tt )}) in the term. -{\tt refine} will generate as many -subgoals as they are holes in the term. The type of holes must be -either synthesized by the system or declared by an -explicit cast like \verb|(\_:nat->Prop)|. This low-level -tactic can be useful to advanced users. - -%\firstexample -\Example - -\begin{coq_example*} -Inductive Option : Set := - | Fail : Option - | Ok : bool -> Option. -\end{coq_example} -\begin{coq_example} -Definition get : forall x:Option, x <> Fail -> bool. -refine - (fun x:Option => - match x return x <> Fail -> bool with - | Fail => _ - | Ok b => fun _ => b - end). -intros; absurd (Fail = Fail); trivial. -\end{coq_example} -\begin{coq_example*} -Defined. -\end{coq_example*} - -% \example{Using Refine to build a poor-man's ``Cases'' tactic} - -% \texttt{Refine} is actually the only way for the user to do -% a proof with the same structure as a {\tt Cases} definition. Actually, -% the tactics \texttt{case} (see \ref{case}) and \texttt{Elim} (see -% \ref{elim}) only allow one step of elementary induction. - -% \begin{coq_example*} -% Require Bool. -% Require Arith. -% \end{coq_example*} -% %\begin{coq_eval} -% %Abort. -% %\end{coq_eval} -% \begin{coq_example} -% Definition one_two_or_five := [x:nat] -% Cases x of -% (1) => true -% | (2) => true -% | (5) => true -% | _ => false -% end. -% Goal (x:nat)(Is_true (one_two_or_five x)) -> x=(1)\/x=(2)\/x=(5). -% \end{coq_example} - -% A traditional script would be the following: - -% \begin{coq_example*} -% Destruct x. -% Tauto. -% Destruct n. -% Auto. -% Destruct n0. -% Auto. -% Destruct n1. -% Tauto. -% Destruct n2. -% Tauto. -% Destruct n3. -% Auto. -% Intros; Inversion H. -% \end{coq_example*} - -% With the tactic \texttt{Refine}, it becomes quite shorter: - -% \begin{coq_example*} -% Restart. -% \end{coq_example*} -% \begin{coq_example} -% Refine [x:nat] -% <[y:nat](Is_true (one_two_or_five y))->(y=(1)\/y=(2)\/y=(5))> -% Cases x of -% (1) => [H]? -% | (2) => [H]? -% | (5) => [H]? -% | n => [H](False_ind ? H) -% end; Auto. -% \end{coq_example} -% \begin{coq_eval} -% Abort. -% \end{coq_eval} - -\section[\tt eapply]{\tt eapply\tacindex{eapply} -\label{eapply-example}} -\Example -Assume we have a relation on {\tt nat} which is transitive: - -\begin{coq_example*} -Variable R : nat -> nat -> Prop. -Hypothesis Rtrans : forall x y z:nat, R x y -> R y z -> R x z. -Variables n m p : nat. -Hypothesis Rnm : R n m. -Hypothesis Rmp : R m p. -\end{coq_example*} - -Consider the goal {\tt (R n p)} provable using the transitivity of -{\tt R}: - -\begin{coq_example*} -Goal R n p. -\end{coq_example*} - -The direct application of {\tt Rtrans} with {\tt apply} fails because -no value for {\tt y} in {\tt Rtrans} is found by {\tt apply}: - -\begin{coq_eval} -Set Printing Depth 50. -(********** The following is not correct and should produce **********) -(**** Error: generated subgoal (R n ?17) has metavariables in it *****) -\end{coq_eval} -\begin{coq_example} -apply Rtrans. -\end{coq_example} - -A solution is to rather apply {\tt (Rtrans n m p)}. - -\begin{coq_example} -apply (Rtrans n m p). -\end{coq_example} - -\begin{coq_eval} -Undo. -\end{coq_eval} - -More elegantly, {\tt apply Rtrans with (y:=m)} allows to only mention -the unknown {\tt m}: - -\begin{coq_example} - - apply Rtrans with (y := m). -\end{coq_example} - -\begin{coq_eval} -Undo. -\end{coq_eval} - -Another solution is to mention the proof of {\tt (R x y)} in {\tt -Rtrans}... - -\begin{coq_example} - - apply Rtrans with (1 := Rnm). -\end{coq_example} - -\begin{coq_eval} -Undo. -\end{coq_eval} - -... or the proof of {\tt (R y z)}: - -\begin{coq_example} - - apply Rtrans with (2 := Rmp). -\end{coq_example} - -\begin{coq_eval} -Undo. -\end{coq_eval} - -On the opposite, one can use {\tt eapply} which postpone the problem -of finding {\tt m}. Then one can apply the hypotheses {\tt Rnm} and {\tt -Rmp}. This instantiates the existential variable and completes the proof. - -\begin{coq_example} -eapply Rtrans. -apply Rnm. -apply Rmp. -\end{coq_example} - -\begin{coq_eval} -Reset R. -\end{coq_eval} - -\section[{\tt Scheme}]{{\tt Scheme}\comindex{Scheme} -\label{Scheme-examples}} - -\firstexample -\example{Induction scheme for \texttt{tree} and \texttt{forest}} - -The definition of principle of mutual induction for {\tt tree} and -{\tt forest} over the sort {\tt Set} is defined by the command: - -\begin{coq_eval} -Reset Initial. -Variables A B : - Set. -\end{coq_eval} - -\begin{coq_example*} -Inductive tree : Set := - node : A -> forest -> tree -with forest : Set := - | leaf : B -> forest - | cons : tree -> forest -> forest. - -Scheme tree_forest_rec := Induction for tree Sort Set - with forest_tree_rec := Induction for forest Sort Set. -\end{coq_example*} - -You may now look at the type of {\tt tree\_forest\_rec}: - -\begin{coq_example} -Check tree_forest_rec. -\end{coq_example} - -This principle involves two different predicates for {\tt trees} and -{\tt forests}; it also has three premises each one corresponding to a -constructor of one of the inductive definitions. - -The principle {\tt forest\_tree\_rec} shares exactly the same -premises, only the conclusion now refers to the property of forests. - -\begin{coq_example} -Check forest_tree_rec. -\end{coq_example} - -\example{Predicates {\tt odd} and {\tt even} on naturals} - -Let {\tt odd} and {\tt even} be inductively defined as: - -% Reset Initial. -\begin{coq_eval} -Open Scope nat_scope. -\end{coq_eval} - -\begin{coq_example*} -Inductive odd : nat -> Prop := - oddS : forall n:nat, even n -> odd (S n) -with even : nat -> Prop := - | evenO : even 0 - | evenS : forall n:nat, odd n -> even (S n). -\end{coq_example*} - -The following command generates a powerful elimination -principle: - -\begin{coq_example} -Scheme odd_even := Minimality for odd Sort Prop - with even_odd := Minimality for even Sort Prop. -\end{coq_example} - -The type of {\tt odd\_even} for instance will be: - -\begin{coq_example} -Check odd_even. -\end{coq_example} - -The type of {\tt even\_odd} shares the same premises but the -conclusion is {\tt (n:nat)(even n)->(Q n)}. - -\subsection[{\tt Combined Scheme}]{{\tt Combined Scheme}\comindex{Combined Scheme} -\label{CombinedScheme-examples}} - -We can define the induction principles for trees and forests using: -\begin{coq_example} -Scheme tree_forest_ind := Induction for tree Sort Prop - with forest_tree_ind := Induction for forest Sort Prop. -\end{coq_example} - -Then we can build the combined induction principle which gives the -conjunction of the conclusions of each individual principle: -\begin{coq_example} -Combined Scheme tree_forest_mutind from tree_forest_ind, forest_tree_ind. -\end{coq_example} - -The type of {\tt tree\_forest\_mutrec} will be: -\begin{coq_example} -Check tree_forest_mutind. -\end{coq_example} - -\section[{\tt Functional Scheme} and {\tt functional induction}]{{\tt Functional Scheme} and {\tt functional induction}\comindex{Functional Scheme}\tacindex{functional induction} -\label{FunScheme-examples}} - -\firstexample -\example{Induction scheme for \texttt{div2}} - -We define the function \texttt{div2} as follows: - -\begin{coq_eval} -Reset Initial. -\end{coq_eval} - -\begin{coq_example*} -Require Import Arith. -Fixpoint div2 (n:nat) : nat := - match n with - | O => 0 - | S O => 0 - | S (S n') => S (div2 n') - end. -\end{coq_example*} - -The definition of a principle of induction corresponding to the -recursive structure of \texttt{div2} is defined by the command: - -\begin{coq_example} -Functional Scheme div2_ind := Induction for div2 Sort Prop. -\end{coq_example} - -You may now look at the type of {\tt div2\_ind}: - -\begin{coq_example} -Check div2_ind. -\end{coq_example} - -We can now prove the following lemma using this principle: - - -\begin{coq_example*} -Lemma div2_le' : forall n:nat, div2 n <= n. -intro n. - pattern n , (div2 n). -\end{coq_example*} - - -\begin{coq_example} -apply div2_ind; intros. -\end{coq_example} - -\begin{coq_example*} -auto with arith. -auto with arith. -simpl; auto with arith. -Qed. -\end{coq_example*} - -We can use directly the \texttt{functional induction} -(\ref{FunInduction}) tactic instead of the pattern/apply trick: - -\begin{coq_example*} -Reset div2_le'. -Lemma div2_le : forall n:nat, div2 n <= n. -intro n. -\end{coq_example*} - -\begin{coq_example} -functional induction (div2 n). -\end{coq_example} - -\begin{coq_example*} -auto with arith. -auto with arith. -auto with arith. -Qed. -\end{coq_example*} - -\Rem There is a difference between obtaining an induction scheme for a -function by using \texttt{Function} (see Section~\ref{Function}) and by -using \texttt{Functional Scheme} after a normal definition using -\texttt{Fixpoint} or \texttt{Definition}. See \ref{Function} for -details. - - -\example{Induction scheme for \texttt{tree\_size}} - -\begin{coq_eval} -Reset Initial. -\end{coq_eval} - -We define trees by the following mutual inductive type: - -\begin{coq_example*} -Variable A : Set. -Inductive tree : Set := - node : A -> forest -> tree -with forest : Set := - | empty : forest - | cons : tree -> forest -> forest. -\end{coq_example*} - -We define the function \texttt{tree\_size} that computes the size -of a tree or a forest. Note that we use \texttt{Function} which -generally produces better principles. - -\begin{coq_example*} -Function 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 - | empty => 0 - | cons t f' => (tree_size t + forest_size f') - end. -\end{coq_example*} - -Remark: \texttt{Function} generates itself non mutual induction -principles {\tt tree\_size\_ind} and {\tt forest\_size\_ind}: - -\begin{coq_example} -Check tree_size_ind. -\end{coq_example} - -The definition of mutual induction principles following the recursive -structure of \texttt{tree\_size} and \texttt{forest\_size} is defined -by the command: - -\begin{coq_example*} -Functional Scheme tree_size_ind2 := Induction for tree_size Sort Prop -with forest_size_ind2 := Induction for forest_size Sort Prop. -\end{coq_example*} - -You may now look at the type of {\tt tree\_size\_ind2}: - -\begin{coq_example} -Check tree_size_ind2. -\end{coq_example} - - - - -\section[{\tt inversion}]{{\tt inversion}\tacindex{inversion} -\label{inversion-examples}} - -\subsection*{Generalities about inversion} - -When working with (co)inductive predicates, we are very often faced to -some of these situations: -\begin{itemize} -\item we have an inconsistent instance of an inductive predicate in the - local context of hypotheses. Thus, the current goal can be trivially - proved by absurdity. -\item we have a hypothesis that is an instance of an inductive - predicate, and the instance has some variables whose constraints we - would like to derive. -\end{itemize} - -The inversion tactics are very useful to simplify the work in these -cases. Inversion tools can be classified in three groups: - -\begin{enumerate} -\item tactics for inverting an instance without stocking the inversion - lemma in the context; this includes the tactics - (\texttt{dependent}) \texttt{inversion} and - (\texttt{dependent}) \texttt{inversion\_clear}. -\item commands for generating and stocking in the context the inversion - lemma corresponding to an instance; this includes \texttt{Derive} - (\texttt{Dependent}) \texttt{Inversion} and \texttt{Derive} - (\texttt{Dependent}) \texttt{Inversion\_clear}. -\item tactics for inverting an instance using an already defined - inversion lemma; this includes the tactic \texttt{inversion \ldots using}. -\end{enumerate} - -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. - -\firstexample -\example{Non-dependent inversion} - -Let's consider the relation \texttt{Le} over natural numbers and the -following variables: - -\begin{coq_eval} -Reset Initial. -\end{coq_eval} - -\begin{coq_example*} -Inductive Le : nat -> nat -> Set := - | LeO : forall n:nat, Le 0 n - | LeS : forall n m:nat, Le n m -> Le (S n) (S m). -Variable P : nat -> nat -> Prop. -Variable Q : forall n m:nat, Le n m -> Prop. -\end{coq_example*} - -For example, consider the goal: - -\begin{coq_eval} -Lemma ex : forall n m:nat, Le (S n) m -> P n m. -intros. -\end{coq_eval} - -\begin{coq_example} -Show. -\end{coq_example} - -To prove the goal we may need to reason by cases on \texttt{H} and to - derive that \texttt{m} is necessarily of -the form $(S~m_0)$ for certain $m_0$ and that $(Le~n~m_0)$. -Deriving these conditions corresponds to prove that the -only possible constructor of \texttt{(Le (S n) m)} is -\texttt{LeS} and that we can invert the -\texttt{->} in the type of \texttt{LeS}. -This inversion is possible because \texttt{Le} is the smallest set closed by -the constructors \texttt{LeO} and \texttt{LeS}. - -\begin{coq_example} -inversion_clear H. -\end{coq_example} - -Note that \texttt{m} has been substituted in the goal for \texttt{(S m0)} -and that the hypothesis \texttt{(Le n m0)} has been added to the -context. - -Sometimes it is -interesting to have the equality \texttt{m=(S m0)} in the -context to use it after. In that case we can use \texttt{inversion} that -does not clear the equalities: - -\begin{coq_example*} -Undo. -\end{coq_example*} - -\begin{coq_example} -inversion H. -\end{coq_example} - -\begin{coq_eval} -Undo. -\end{coq_eval} - -\example{Dependent Inversion} - -Let us consider the following goal: - -\begin{coq_eval} -Lemma ex_dep : forall (n m:nat) (H:Le (S n) m), Q (S n) m H. -intros. -\end{coq_eval} - -\begin{coq_example} -Show. -\end{coq_example} - -As \texttt{H} occurs in the goal, we may want to reason by cases on its -structure and so, we would like inversion tactics to -substitute \texttt{H} by the corresponding term in constructor form. -Neither \texttt{Inversion} nor {\tt Inversion\_clear} make such a -substitution. -To have such a behavior we use the dependent inversion tactics: - -\begin{coq_example} -dependent inversion_clear H. -\end{coq_example} - -Note that \texttt{H} has been substituted by \texttt{(LeS n m0 l)} and -\texttt{m} by \texttt{(S m0)}. - -\example{using already defined inversion lemmas} - -\begin{coq_eval} -Abort. -\end{coq_eval} - -For example, to generate the inversion lemma for the instance -\texttt{(Le (S n) m)} and the sort \texttt{Prop} we do: - -\begin{coq_example*} -Derive Inversion_clear leminv with (forall n m:nat, Le (S n) m) Sort - Prop. -\end{coq_example*} - -\begin{coq_example} -Check leminv. -\end{coq_example} - -Then we can use the proven inversion lemma: - -\begin{coq_example} -Show. -\end{coq_example} - -\begin{coq_example} -inversion H using leminv. -\end{coq_example} - -\begin{coq_eval} -Reset Initial. -\end{coq_eval} - \section[\tt dependent induction]{\tt dependent induction\label{dependent-induction-example}} \def\depind{{\tt dependent induction}~} \def\depdestr{{\tt dependent destruction}~} diff --git a/doc/refman/Reference-Manual.tex b/doc/refman/Reference-Manual.tex index 4736012e8f..4380f5442b 100644 --- a/doc/refman/Reference-Manual.tex +++ b/doc/refman/Reference-Manual.tex @@ -95,8 +95,9 @@ Options A and B of the licence are {\em not} elected.} \include{RefMan-decl.v}% The mathematical proof language \part{User extensions} -\include{RefMan-syn.v}% The Syntax and the Grammad commands +\include{RefMan-syn.v}% The Syntax and the Grammar commands %%SUPPRIME \include{RefMan-tus.v}% Writing tactics +\include{RefMan-sch.v}% The Scheme commands \part{Practical tools} \include{RefMan-com}% The coq commands (coqc coqtop) -- cgit v1.2.3