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Diffstat (limited to 'doc/sphinx/language')
| -rw-r--r-- | doc/sphinx/language/cic.rst | 542 | ||||
| -rw-r--r-- | doc/sphinx/language/coq-library.rst | 54 | ||||
| -rw-r--r-- | doc/sphinx/language/gallina-extensions.rst | 1168 | ||||
| -rw-r--r-- | doc/sphinx/language/gallina-specification-language.rst | 1543 | ||||
| -rw-r--r-- | doc/sphinx/language/module-system.rst | 3 |
5 files changed, 2410 insertions, 900 deletions
diff --git a/doc/sphinx/language/cic.rst b/doc/sphinx/language/cic.rst index 7ed6524095..cc5d9d6205 100644 --- a/doc/sphinx/language/cic.rst +++ b/doc/sphinx/language/cic.rst @@ -1,6 +1,3 @@ -.. include:: ../preamble.rst -.. include:: ../replaces.rst - .. _calculusofinductiveconstructions: @@ -96,8 +93,9 @@ constraints between the universe variables is maintained globally. To ensure the existence of a mapping of the universes to the positive integers, the graph of constraints must remain acyclic. Typing expressions that violate the acyclicity of the graph of constraints -results in a Universe inconsistency error (see also Section -:ref:`TODO-2.10`). +results in a Universe inconsistency error. + +.. seealso:: Section :ref:`printing-universes`. .. _Terms: @@ -373,19 +371,22 @@ following rules. -**Remark**: **Prod-Prop** and **Prod-Set** typing-rules make sense if we consider the -semantic difference between :math:`\Prop` and :math:`\Set`: +.. note:: + **Prod-Prop** and **Prod-Set** typing-rules make sense if we consider the + semantic difference between :math:`\Prop` and :math:`\Set`: -+ All values of a type that has a sort :math:`\Set` are extractable. -+ No values of a type that has a sort :math:`\Prop` are extractable. + + All values of a type that has a sort :math:`\Set` are extractable. + + No values of a type that has a sort :math:`\Prop` are extractable. -**Remark**: We may have :math:`\letin{x}{t:T}{u}` well-typed without having -:math:`((λ x:T.u) t)` well-typed (where :math:`T` is a type of -:math:`t`). This is because the value :math:`t` associated to -:math:`x` may be used in a conversion rule (see Section :ref:`Conversion-rules`). +.. note:: + We may have :math:`\letin{x}{t:T}{u}` well-typed without having + :math:`((λ x:T.u) t)` well-typed (where :math:`T` is a type of + :math:`t`). This is because the value :math:`t` associated to + :math:`x` may be used in a conversion rule + (see Section :ref:`Conversion-rules`). .. _Conversion-rules: @@ -398,9 +399,11 @@ can decide if two programs are *intentionally* equal (one says *convertible*). Convertibility is described in this section. -.. _β-reduction: +.. _beta-reduction: + +β-reduction +~~~~~~~~~~~ -**β-reduction.** We want to be able to identify some terms as we can identify the application of a function to a given argument with its result. For instance the identity function over a given type T can be written @@ -424,9 +427,11 @@ theoretically of great importance but we will not detail them here and refer the interested reader to :cite:`Coq85`. -.. _ι-reduction: +.. _iota-reduction: + +ι-reduction +~~~~~~~~~~~ -**ι-reduction.** A specific conversion rule is associated to the inductive objects in the global environment. We shall give later on (see Section :ref:`Well-formed-inductive-definitions`) the precise rules but it @@ -435,9 +440,11 @@ constructor behaves as expected. This reduction is called ι-reduction and is more precisely studied in :cite:`Moh93,Wer94`. -.. _δ-reduction: +.. _delta-reduction: + +δ-reduction +~~~~~~~~~~~ -**δ-reduction.** We may have variables defined in local contexts or constants defined in the global environment. It is legal to identify such a reference with its value, that is to expand (or unfold) it into its value. This @@ -458,9 +465,11 @@ reduction is called δ-reduction and shows as follows. E[Γ] ⊢ c~\triangleright_δ~t -.. _ζ-reduction: +.. _zeta-reduction: + +ζ-reduction +~~~~~~~~~~~ -**ζ-reduction.** |Coq| allows also to remove local definitions occurring in terms by replacing the defined variable by its value. The declaration being destroyed, this reduction differs from δ-reduction. It is called @@ -475,9 +484,11 @@ destroyed, this reduction differs from δ-reduction. It is called E[Γ] ⊢ \letin{x}{u}{t}~\triangleright_ζ~\subst{t}{x}{u} -.. _η-expansion: +.. _eta-expansion: + +η-expansion +~~~~~~~~~~~ -**η-expansion.** Another important concept is η-expansion. It is legal to identify any term :math:`t` of functional type :math:`∀ x:T, U` with its so-called η-expansion @@ -487,41 +498,45 @@ term :math:`t` of functional type :math:`∀ x:T, U` with its so-called η-expan for :math:`x` an arbitrary variable name fresh in :math:`t`. -**Remark**: We deliberately do not define η-reduction: +.. note:: -.. math:: - λ x:T. (t~x) \not\triangleright_η t + We deliberately do not define η-reduction: + + .. math:: + λ x:T. (t~x) \not\triangleright_η t -This is because, in general, the type of :math:`t` need not to be convertible -to the type of :math:`λ x:T. (t~x)`. E.g., if we take :math:`f` such that: + This is because, in general, the type of :math:`t` need not to be convertible + to the type of :math:`λ x:T. (t~x)`. E.g., if we take :math:`f` such that: -.. math:: - f : ∀ x:\Type(2),\Type(1) + .. math:: + f : ∀ x:\Type(2),\Type(1) -then + then -.. math:: - λ x:\Type(1),(f~x) : ∀ x:\Type(1),\Type(1) + .. math:: + λ x:\Type(1),(f~x) : ∀ x:\Type(1),\Type(1) -We could not allow + We could not allow -.. math:: - λ x:Type(1),(f x) \triangleright_η f + .. math:: + λ x:Type(1),(f x) \triangleright_η f -because the type of the reduced term :math:`∀ x:\Type(2),\Type(1)` would not be -convertible to the type of the original term :math:`∀ x:\Type(1),\Type(1).` + because the type of the reduced term :math:`∀ x:\Type(2),\Type(1)` would not be + convertible to the type of the original term :math:`∀ x:\Type(1),\Type(1).` -.. _Convertibility: +.. _convertibility: + +Convertibility +~~~~~~~~~~~~~~ -**Convertibility.** Let us write :math:`E[Γ] ⊢ t \triangleright u` for the contextual closure of the relation :math:`t` reduces to :math:`u` in the global environment :math:`E` and local context :math:`Γ` with one of the previous -reductions β, ι, δ or ζ. +reductions β, δ, ι or ζ. We say that two terms :math:`t_1` and :math:`t_2` are -*βιδζη-convertible*, or simply *convertible*, or *equivalent*, in the +*βδιζη-convertible*, or simply *convertible*, or *equivalent*, in the global environment :math:`E` and local context :math:`Γ` iff there exist terms :math:`u_1` and :math:`u_2` such that :math:`E[Γ] ⊢ t_1 \triangleright … \triangleright u_1` and :math:`E[Γ] ⊢ t_2 \triangleright … \triangleright u_2` and either :math:`u_1` and @@ -587,7 +602,7 @@ Subtyping rules At the moment, we did not take into account one rule between universes which says that any term in a universe of index i is also a term in -the universe of index i+1 (this is the *cumulativity* rule of|Cic|). +the universe of index i+1 (this is the *cumulativity* rule of |Cic|). This property extends the equivalence relation of convertibility into a *subtyping* relation inductively defined by: @@ -622,7 +637,7 @@ a *subtyping* relation inductively defined by: respectively then .. math:: - E[Γ] ⊢ t~w_1 … w_m ≤_{βδιζη} t~w_1' … w_m' + E[Γ] ⊢ t~w_1 … w_m ≤_{βδιζη} t'~w_1' … w_m' (notice that :math:`t` and :math:`t'` are both fully applied, i.e., they have a sort as a type) if @@ -663,7 +678,7 @@ form*. There are several ways (or strategies) to apply the reduction rules. Among them, we have to mention the *head reduction* which will play an important role (see Chapter :ref:`tactics`). Any term :math:`t` can be written as :math:`λ x_1 :T_1 . … λ x_k :T_k . (t_0~t_1 … t_n )` where :math:`t_0` is not an -application. We say then that :math:`t~0` is the *head of* :math:`t`. If we assume +application. We say then that :math:`t_0` is the *head of* :math:`t`. If we assume that :math:`t_0` is :math:`λ x:T. u_0` then one step of β-head reduction of :math:`t` is: .. math:: @@ -705,68 +720,70 @@ each :math:`T` in :math:`(t:T)∈Γ_I` can be written as: :math:`∀Γ_P,∀Γ_{ :math:`Γ_{\mathit{Arr}(t)}` is called the *Arity* of the inductive type t and :math:`S` is called the sort of the inductive type t (not to be confused with :math:`\Sort` which is the set of sorts). +.. example:: -** Examples** The declaration for parameterized lists is: + The declaration for parameterized lists is: -.. math:: - \ind{1}{[\List:\Set→\Set]}{\left[\begin{array}{rcl} - \Nil & : & \forall A:\Set,\List~A \\ - \cons & : & \forall A:\Set, A→ \List~A→ \List~A - \end{array} - \right]} + .. math:: + \ind{1}{[\List:\Set→\Set]}{\left[\begin{array}{rcl} + \Nil & : & \forall A:\Set,\List~A \\ + \cons & : & \forall A:\Set, A→ \List~A→ \List~A + \end{array} + \right]} + + which corresponds to the result of the |Coq| declaration: + + .. coqtop:: in -which corresponds to the result of the |Coq| declaration: + Inductive list (A:Set) : Set := + | nil : list A + | cons : A -> list A -> list A. .. example:: - .. coqtop:: in - - Inductive list (A:Set) : Set := - | nil : list A - | cons : A -> list A -> list A. -The declaration for a mutual inductive definition of tree and forest -is: + The declaration for a mutual inductive definition of tree and forest + is: -.. math:: - \ind{~}{\left[\begin{array}{rcl}\tree&:&\Set\\\forest&:&\Set\end{array}\right]} - {\left[\begin{array}{rcl} - \node &:& \forest → \tree\\ - \emptyf &:& \forest\\ - \consf &:& \tree → \forest → \forest\\ - \end{array}\right]} + .. math:: + \ind{0}{\left[\begin{array}{rcl}\tree&:&\Set\\\forest&:&\Set\end{array}\right]} + {\left[\begin{array}{rcl} + \node &:& \forest → \tree\\ + \emptyf &:& \forest\\ + \consf &:& \tree → \forest → \forest\\ + \end{array}\right]} -which corresponds to the result of the |Coq| declaration: + which corresponds to the result of the |Coq| declaration: -.. example:: - .. coqtop:: in + .. coqtop:: in + + Inductive tree : Set := + | node : forest -> tree + with forest : Set := + | emptyf : forest + | consf : tree -> forest -> forest. - Inductive tree : Set := - | node : forest -> tree - with forest : Set := - | emptyf : forest - | consf : tree -> forest -> forest. +.. example:: -The declaration for a mutual inductive definition of even and odd is: + The declaration for a mutual inductive definition of even and odd is: -.. math:: - \ind{1}{\left[\begin{array}{rcl}\even&:&\nat → \Prop \\ - \odd&:&\nat → \Prop \end{array}\right]} - {\left[\begin{array}{rcl} - \evenO &:& \even~0\\ - \evenS &:& \forall n, \odd~n -> \even~(\kw{S}~n)\\ - \oddS &:& \forall n, \even~n -> \odd~(\kw{S}~n) - \end{array}\right]} + .. math:: + \ind{0}{\left[\begin{array}{rcl}\even&:&\nat → \Prop \\ + \odd&:&\nat → \Prop \end{array}\right]} + {\left[\begin{array}{rcl} + \evenO &:& \even~0\\ + \evenS &:& \forall n, \odd~n → \even~(\kw{S}~n)\\ + \oddS &:& \forall n, \even~n → \odd~(\kw{S}~n) + \end{array}\right]} -which corresponds to the result of the |Coq| declaration: + which corresponds to the result of the |Coq| declaration: -.. example:: - .. coqtop:: in + .. coqtop:: in - Inductive even : nat -> prop := - | even_O : even 0 - | even_S : forall n, odd n -> even (S n) - with odd : nat -> prop := - | odd_S : forall n, even n -> odd (S n). + Inductive even : nat -> Prop := + | even_O : even 0 + | even_S : forall n, odd n -> even (S n) + with odd : nat -> prop := + | odd_S : forall n, even n -> odd (S n). @@ -794,18 +811,19 @@ contains an inductive declaration. --------------------- E[Γ] ⊢ c : C -**Example.** -Provided that our environment :math:`E` contains inductive definitions we showed before, -these two inference rules above enable us to conclude that: +.. example:: -.. math:: - \begin{array}{l} + Provided that our environment :math:`E` contains inductive definitions we showed before, + these two inference rules above enable us to conclude that: + + .. math:: + \begin{array}{l} E[Γ] ⊢ \even : \nat→\Prop\\ E[Γ] ⊢ \odd : \nat→\Prop\\ E[Γ] ⊢ \even\_O : \even~O\\ E[Γ] ⊢ \even\_S : \forall~n:\nat, \odd~n → \even~(S~n)\\ E[Γ] ⊢ \odd\_S : \forall~n:\nat, \even~n → \odd~(S~n) - \end{array} + \end{array} @@ -820,10 +838,11 @@ to inconsistent systems. We restrict ourselves to definitions which satisfy a syntactic criterion of positivity. Before giving the formal rules, we need a few definitions: +Arity of a given sort ++++++++++++++++++++++ -**Type is an Arity of Sort S.** -A type :math:`T` is an *arity of sort s* if it converts to the sort s or to a -product :math:`∀ x:T,U` with :math:`U` an arity of sort s. +A type :math:`T` is an *arity of sort* :math:`s` if it converts to the sort :math:`s` or to a +product :math:`∀ x:T,U` with :math:`U` an arity of sort :math:`s`. .. example:: @@ -831,9 +850,10 @@ product :math:`∀ x:T,U` with :math:`U` an arity of sort s. :math:`\Prop`. -**Type is an Arity.** +Arity ++++++ A type :math:`T` is an *arity* if there is a :math:`s∈ \Sort` such that :math:`T` is an arity of -sort s. +sort :math:`s`. .. example:: @@ -841,32 +861,34 @@ sort s. :math:`A→ Set` and :math:`∀ A:\Prop,A→ \Prop` are arities. -**Type of Constructor of I.** +Type constructor +++++++++++++++++ We say that T is a *type of constructor of I* in one of the following two cases: - + :math:`T` is :math:`(I~t_1 … t_n )` + :math:`T` is :math:`∀ x:U,T'` where :math:`T'` is also a type of constructor of :math:`I` - - .. example:: :math:`\nat` and :math:`\nat→\nat` are types of constructor of :math:`\nat`. :math:`∀ A:Type,\List~A` and :math:`∀ A:Type,A→\List~A→\List~A` are types of constructor of :math:`\List`. -**Positivity Condition.** +.. _positivity: + +Positivity Condition +++++++++++++++++++++ + The type of constructor :math:`T` will be said to *satisfy the positivity condition* for a constant :math:`X` in the following cases: - + :math:`T=(X~t_1 … t_n )` and :math:`X` does not occur free in any :math:`t_i` + :math:`T=∀ x:U,V` and :math:`X` occurs only strictly positively in :math:`U` and the type :math:`V` satisfies the positivity condition for :math:`X`. - -**Occurs Strictly Positively.** +Strict positivity ++++++++++++++++++ + The constant :math:`X` *occurs strictly positively* in :math:`T` in the following cases: @@ -886,63 +908,52 @@ cases: any of the :math:`t_i`, and the (instantiated) types of constructor :math:`\subst{C_i}{p_j}{a_j}_{j=1… m}` of :math:`I` satisfy the nested positivity condition for :math:`X` -**Nested Positivity Condition.** +Nested Positivity ++++++++++++++++++ + The type of constructor :math:`T` of :math:`I` *satisfies the nested positivity condition* for a constant :math:`X` in the following cases: - + :math:`T=(I~b_1 … b_m~u_1 … u_p)`, :math:`I` is an inductive definition with :math:`m` parameters and :math:`X` does not occur in any :math:`u_i` + :math:`T=∀ x:U,V` and :math:`X` occurs only strictly positively in :math:`U` and the type :math:`V` satisfies the nested positivity condition for :math:`X` -For instance, if one considers the type - .. example:: - .. coqtop:: all - Module TreeExample. - Inductive tree (A:Type) : Type := - | leaf : tree A - | node : A -> (nat -> tree A) -> tree A. - End TreeExample. - -:: + For instance, if one considers the following variant of a tree type + branching over the natural numbers: - [TODO Note: This commentary does not seem to correspond to the - preceding example. Instead it is referring to the first example - in Inductive Definitions section. It seems we should either - delete the preceding example and refer the the example above of - type `list A`, or else we should rewrite the commentary below.] - - Then every instantiated constructor of list A satisfies the nested positivity - condition for list - │ - ├─ concerning type list A of constructor nil: - │ Type list A of constructor nil satisfies the positivity condition for list - │ because list does not appear in any (real) arguments of the type of that - | constructor (primarily because list does not have any (real) - | arguments) ... (bullet 1) - │ - ╰─ concerning type ∀ A → list A → list A of constructor cons: - Type ∀ A : Type, A → list A → list A of constructor cons - satisfies the positivity condition for list because: - │ - ├─ list occurs only strictly positively in Type ... (bullet 3) - │ - ├─ list occurs only strictly positively in A ... (bullet 3) - │ - ├─ list occurs only strictly positively in list A ... (bullet 4) - │ - ╰─ list satisfies the positivity condition for list A ... (bullet 1) + .. coqtop:: in + + Inductive nattree (A:Type) : Type := + | leaf : nattree A + | node : A -> (nat -> nattree A) -> nattree A. + End TreeExample. + + Then every instantiated constructor of ``nattree A`` satisfies the nested positivity + condition for ``nattree``: + + + Type ``nattree A`` of constructor ``leaf`` satisfies the positivity condition for + ``nattree`` because ``nattree`` does not appear in any (real) arguments of the + type of that constructor (primarily because ``nattree`` does not have any (real) + arguments) ... (bullet 1) + + Type ``A → (nat → nattree A) → nattree A`` of constructor ``node`` satisfies the + positivity condition for ``nattree`` because: + - ``nattree`` occurs only strictly positively in ``A`` ... (bullet 3) + - ``nattree`` occurs only strictly positively in ``nat → nattree A`` ... (bullet 3 + 2) + + - ``nattree`` satisfies the positivity condition for ``nattree A`` ... (bullet 1) .. _Correctness-rules: -**Correctness rules.** +Correctness rules ++++++++++++++++++ + We shall now describe the rules allowing the introduction of a new inductive definition. @@ -953,7 +964,7 @@ such that :math:`Γ_I` is :math:`[I_1 :∀ Γ_P ,A_1 ;…;I_k :∀ Γ_P ,A_k]`, .. inference:: W-Ind \WFE{Γ_P} - (E[Γ_P ] ⊢ A_j : s_j' )_{j=1… k} + (E[Γ_P ] ⊢ A_j : s_j )_{j=1… k} (E[Γ_I ;Γ_P ] ⊢ C_i : s_{q_i} )_{i=1… n} ------------------------------------------ \WF{E;\ind{p}{Γ_I}{Γ_C}}{Γ} @@ -971,35 +982,34 @@ provided that the following side conditions hold: One can remark that there is a constraint between the sort of the arity of the inductive type and the sort of the type of its constructors which will always be satisfied for the impredicative -sortProp but may fail to define inductive definition on sort Set and +sort :math:`\Prop` but may fail to define inductive definition on sort :math:`\Set` and generate constraints between universes for inductive definitions in the Type hierarchy. -**Examples**. It is well known that the existential quantifier can be encoded as an -inductive definition. The following declaration introduces the second- -order existential quantifier :math:`∃ X.P(X)`. - .. example:: + + It is well known that the existential quantifier can be encoded as an + inductive definition. The following declaration introduces the second- + order existential quantifier :math:`∃ X.P(X)`. + .. coqtop:: in - + Inductive exProp (P:Prop->Prop) : Prop := | exP_intro : forall X:Prop, P X -> exProp P. -The same definition on Set is not allowed and fails: + The same definition on :math:`\Set` is not allowed and fails: -.. example:: .. coqtop:: all Fail Inductive exSet (P:Set->Prop) : Set := exS_intro : forall X:Set, P X -> exSet P. -It is possible to declare the same inductive definition in the -universe Type. The exType inductive definition has type -:math:`(\Type(i)→\Prop)→\Type(j)` with the constraint that the parameter :math:`X` of :math:`\kw{exT_intro}` -has type :math:`\Type(k)` with :math:`k<j` and :math:`k≤ i`. + It is possible to declare the same inductive definition in the + universe :math:`\Type`. The :g:`exType` inductive definition has type + :math:`(\Type(i)→\Prop)→\Type(j)` with the constraint that the parameter :math:`X` of :math:`\kw{exT}_{\kw{intro}}` + has type :math:`\Type(k)` with :math:`k<j` and :math:`k≤ i`. -.. example:: .. coqtop:: all Inductive exType (P:Type->Prop) : Type := @@ -1009,10 +1019,30 @@ has type :math:`\Type(k)` with :math:`k<j` and :math:`k≤ i`. .. _Template-polymorphism: -**Template polymorphism.** -Inductive types declared in Type are polymorphic over their arguments -in Type. If :math:`A` is an arity of some sort and s is a sort, we write :math:`A_{/s}` -for the arity obtained from :math:`A` by replacing its sort with s. +Template polymorphism ++++++++++++++++++++++ + +Inductive types can be made polymorphic over their arguments +in :math:`\Type`. + +.. flag:: Auto Template Polymorphism + + This option, enabled by default, makes every inductive type declared + at level :math:`Type` (without annotations or hiding it behind a + definition) template polymorphic. + + This can be prevented using the ``notemplate`` attribute. + + An inductive type can be forced to be template polymorphic using the + ``template`` attribute. + + Template polymorphism and universe polymorphism (see Chapter + :ref:`polymorphicuniverses`) are incompatible, so if the later is + enabled it will prevail over automatic template polymorphism and + cause an error when using the ``template`` attribute. + +If :math:`A` is an arity of some sort and :math:`s` is a sort, we write :math:`A_{/s}` +for the arity obtained from :math:`A` by replacing its sort with :math:`s`. Especially, if :math:`A` is well-typed in some global environment and local context, then :math:`A_{/s}` is typable by typability of all products in the Calculus of Inductive Constructions. The following typing rule is @@ -1053,7 +1083,7 @@ provided that the following side conditions hold: we have :math:`(E[Γ_{I′} ;Γ_{P′}] ⊢ C_i : s_{q_i})_{i=1… n}` ; + the sorts :math:`s_i` are such that all eliminations, to :math:`\Prop`, :math:`\Set` and :math:`\Type(j)`, are allowed - (see Section Destructors_). + (see Section :ref:`Destructors`). @@ -1083,17 +1113,18 @@ The sorts :math:`s_j` are chosen canonically so that each :math:`s_j` is minimal respect to the hierarchy :math:`\Prop ⊂ \Set_p ⊂ \Type` where :math:`\Set_p` is predicative :math:`\Set`. More precisely, an empty or small singleton inductive definition (i.e. an inductive definition of which all inductive types are -singleton – see paragraph Destructors_) is set in :math:`\Prop`, a small non-singleton +singleton – see Section :ref:`Destructors`) is set in :math:`\Prop`, a small non-singleton inductive type is set in :math:`\Set` (even in case :math:`\Set` is impredicative – see Section The-Calculus-of-Inductive-Construction-with-impredicative-Set_), and otherwise in the Type hierarchy. Note that the side-condition about allowed elimination sorts in the rule **Ind-Family** is just to avoid to recompute the allowed elimination -sorts at each instance of a pattern-matching (see section Destructors_). As +sorts at each instance of a pattern matching (see Section :ref:`Destructors`). As an example, let us consider the following definition: .. example:: + .. coqtop:: in Inductive option (A:Type) : Type := @@ -1106,10 +1137,11 @@ in the Type hierarchy. Here, the parameter :math:`A` has this property, hence, if :g:`option` is applied to a type in :math:`\Set`, the result is in :math:`\Set`. Note that if :g:`option` is applied to a type in :math:`\Prop`, then, the result is not set in :math:`\Prop` but in :math:`\Set` still. This is because :g:`option` is not a singleton type -(see section Destructors_) and it would lose the elimination to :math:`\Set` and :math:`\Type` +(see Section :ref:`Destructors`) and it would lose the elimination to :math:`\Set` and :math:`\Type` if set in :math:`\Prop`. .. example:: + .. coqtop:: all Check (fun A:Set => option A). @@ -1118,6 +1150,7 @@ if set in :math:`\Prop`. Here is another example. .. example:: + .. coqtop:: in Inductive prod (A B:Type) : Type := pair : A -> B -> prod A B. @@ -1128,6 +1161,7 @@ none in :math:`\Type`, and in :math:`\Type` otherwise. In all cases, the three k eliminations schemes are allowed. .. example:: + .. coqtop:: all Check (fun A:Set => prod A). @@ -1135,9 +1169,10 @@ eliminations schemes are allowed. Check (fun (A:Prop) (B:Set) => prod A B). Check (fun (A:Type) (B:Prop) => prod A B). -Remark: Template polymorphism used to be called “sort-polymorphism of -inductive types” before universe polymorphism (see Chapter :ref:`polymorphicuniverses`) was -introduced. +.. note:: + Template polymorphism used to be called “sort-polymorphism of + inductive types” before universe polymorphism + (see Chapter :ref:`polymorphicuniverses`) was introduced. .. _Destructors: @@ -1166,7 +1201,7 @@ ourselves to primitive recursive functions and functionals. For instance, assuming a parameter :g:`A:Set` exists in the local context, we want to build a function length of type :g:`list A -> nat` which computes -the length of the list, so such that :g:`(length (nil A)) = O` and :g:`(length +the length of the list, such that :g:`(length (nil A)) = O` and :g:`(length (cons A a l)) = (S (length l))`. We want these equalities to be recognized implicitly and taken into account in the conversion rule. @@ -1209,13 +1244,15 @@ primitive recursion over the structure. But this operator is rather tedious to implement and use. We choose in this version of |Coq| to factorize the operator for primitive recursion into two more primitive operations as was first suggested by Th. -Coquand in :cite:`Coq92`. One is the definition by pattern-matching. The +Coquand in :cite:`Coq92`. One is the definition by pattern matching. The second one is a definition by guarded fixpoints. -.. _The-match…with-end-construction: +.. _match-construction: + +The match ... with ... end construction ++++++++++++++++++++++++++++++++++++++++ -**The match…with …end construction** The basic idea of this operator is that we have an object :math:`m` in an inductive type :math:`I` and we want to prove a property which possibly depends on :math:`m`. For this, it is enough to prove the property for @@ -1224,14 +1261,14 @@ The |Coq| term for this proof will be written: .. math:: - \Match~m~\with~(c_1~x_{11} ... x_{1p_1} ) ⇒ f_1 | … | (c_n~x_{n1} ... x_{np_n} ) ⇒ f_n \endkw + \Match~m~\with~(c_1~x_{11} ... x_{1p_1} ) ⇒ f_1 | … | (c_n~x_{n1} ... x_{np_n} ) ⇒ f_n \kwend In this expression, if :math:`m` eventually happens to evaluate to :math:`(c_i~u_1 … u_{p_i})` then the expression will behave as specified in its :math:`i`-th branch and it will reduce to :math:`f_i` where the :math:`x_{i1} …x_{ip_i}` are replaced by the :math:`u_1 … u_{p_i}` according to the ι-reduction. -Actually, for type-checking a :math:`\Match…\with…\endkw` expression we also need +Actually, for type checking a :math:`\Match…\with…\kwend` expression we also need to know the predicate P to be proved by case analysis. In the general case where :math:`I` is an inductively defined :math:`n`-ary relation, :math:`P` is a predicate over :math:`n+1` arguments: the :math:`n` first ones correspond to the arguments of :math:`I` @@ -1245,7 +1282,7 @@ using the syntax: .. math:: \Match~m~\as~x~\In~I~\_~a~\return~P~\with~ (c_1~x_{11} ... x_{1p_1} ) ⇒ f_1 | … - | (c_n~x_{n1} ... x_{np_n} ) ⇒ f_n~\endkw + | (c_n~x_{n1} ... x_{np_n} ) ⇒ f_n~\kwend The :math:`\as` part can be omitted if either the result type does not depend on :math:`m` (non-dependent elimination) or :math:`m` is a variable (in this case, :math:`m` @@ -1272,7 +1309,7 @@ and :math:`I:A` and :math:`λ a x . P : B` then by :math:`[I:A|B]` we mean that :math:`λ a x . P` with :math:`m` in the above match-construct. -.. _Notations: +.. _cic_notations: **Notations.** The :math:`[I:A|B]` is defined as the smallest relation satisfying the following rules: We write :math:`[I|B]` for :math:`[I:A|B]` where :math:`A` is the type of :math:`I`. @@ -1313,6 +1350,7 @@ the extraction mechanism. Assume :math:`A` and :math:`B` are two propositions, a logical disjunction :math:`A ∨ B` is defined inductively by: .. example:: + .. coqtop:: in Inductive or (A B:Prop) : Prop := @@ -1323,6 +1361,7 @@ The following definition which computes a boolean value by case over the proof of :g:`or A B` is not accepted: .. example:: + .. coqtop:: all Fail Definition choice (A B: Prop) (x:or A B) := @@ -1346,6 +1385,7 @@ property which are provably different, contradicting the proof- irrelevance property which is sometimes a useful axiom: .. example:: + .. coqtop:: all Axiom proof_irrelevance : forall (P : Prop) (x y : P), x=y. @@ -1353,7 +1393,7 @@ irrelevance property which is sometimes a useful axiom: The elimination of an inductive definition of type :math:`\Prop` on a predicate :math:`P` of type :math:`I→ Type` leads to a paradox when applied to impredicative inductive definition like the second-order existential quantifier -:g:`exProp` defined above, because it give access to the two projections on +:g:`exProp` defined above, because it gives access to the two projections on this type. @@ -1370,15 +1410,16 @@ this type. [I:Prop|I→ s] A *singleton definition* has only one constructor and all the -arguments of this constructor have type Prop. In that case, there is a +arguments of this constructor have type :math:`\Prop`. In that case, there is a canonical way to interpret the informative extraction on an object in that type, such that the elimination on any sort :math:`s` is legal. Typical examples are the conjunction of non-informative propositions and the -equality. If there is an hypothesis :math:`h:a=b` in the local context, it can +equality. If there is a hypothesis :math:`h:a=b` in the local context, it can be used for rewriting not only in logical propositions but also in any type. .. example:: + .. coqtop:: all Print eq_rec. @@ -1409,45 +1450,48 @@ corresponding to the :math:`c:C` constructor. We write :math:`\{c\}^P` for :math:`\{c:C\}^P` with :math:`C` the type of :math:`c`. -**Example.** -The following term in concrete syntax:: +.. example:: - match t as l return P' with - | nil _ => t1 - | cons _ hd tl => t2 - end + The following term in concrete syntax:: + match t as l return P' with + | nil _ => t1 + | cons _ hd tl => t2 + end -can be represented in abstract syntax as -.. math:: - \case(t,P,f 1 | f 2 ) + can be represented in abstract syntax as -where + .. math:: + \case(t,P,f 1 | f 2 ) -.. math:: - \begin{eqnarray*} - P & = & \lambda~l~.~P^\prime\\ - f_1 & = & t_1\\ - f_2 & = & \lambda~(hd:\nat)~.~\lambda~(tl:\List~\nat)~.~t_2 - \end{eqnarray*} + where -According to the definition: + .. math:: + :nowrap: -.. math:: - \{(\kw{nil}~\nat)\}^P ≡ \{(\kw{nil}~\nat) : (\List~\nat)\}^P ≡ (P~(\kw{nil}~\nat)) + \begin{eqnarray*} + P & = & \lambda~l~.~P^\prime\\ + f_1 & = & t_1\\ + f_2 & = & \lambda~(hd:\nat)~.~\lambda~(tl:\List~\nat)~.~t_2 + \end{eqnarray*} -.. math:: - - \begin{array}{rl} - \{(\kw{cons}~\nat)\}^P & ≡\{(\kw{cons}~\nat) : (\nat→\List~\nat→\List~\nat)\}^P \\ - & ≡∀ n:\nat, \{(\kw{cons}~\nat~n) : \List~\nat→\List~\nat)\}^P \\ - & ≡∀ n:\nat, ∀ l:\List~\nat, \{(\kw{cons}~\nat~n~l) : \List~\nat)\}^P \\ - & ≡∀ n:\nat, ∀ l:\List~\nat,(P~(\kw{cons}~\nat~n~l)). - \end{array} + According to the definition: -Given some :math:`P` then :math:`\{(\kw{nil}~\nat)\}^P` represents the expected type of :math:`f_1` , -and :math:`\{(\kw{cons}~\nat)\}^P` represents the expected type of :math:`f_2`. + .. math:: + \{(\kw{nil}~\nat)\}^P ≡ \{(\kw{nil}~\nat) : (\List~\nat)\}^P ≡ (P~(\kw{nil}~\nat)) + + .. math:: + + \begin{array}{rl} + \{(\kw{cons}~\nat)\}^P & ≡\{(\kw{cons}~\nat) : (\nat→\List~\nat→\List~\nat)\}^P \\ + & ≡∀ n:\nat, \{(\kw{cons}~\nat~n) : \List~\nat→\List~\nat)\}^P \\ + & ≡∀ n:\nat, ∀ l:\List~\nat, \{(\kw{cons}~\nat~n~l) : \List~\nat)\}^P \\ + & ≡∀ n:\nat, ∀ l:\List~\nat,(P~(\kw{cons}~\nat~n~l)). + \end{array} + + Given some :math:`P` then :math:`\{(\kw{nil}~\nat)\}^P` represents the expected type of :math:`f_1` , + and :math:`\{(\kw{cons}~\nat)\}^P` represents the expected type of :math:`f_2`. .. _Typing-rule: @@ -1473,20 +1517,21 @@ definition :math:`\ind{r}{Γ_I}{Γ_C}` with :math:`Γ_C = [c_1 :C_1 ;…;c_n :C_ -**Example.** -Below is a typing rule for the term shown in the previous example: +.. example:: -.. inference:: list example + Below is a typing rule for the term shown in the previous example: - \begin{array}{l} - E[Γ] ⊢ t : (\List ~\nat) \\ - E[Γ] ⊢ P : B \\ - [(\List ~\nat)|B] \\ - E[Γ] ⊢ f_1 : {(\kw{nil} ~\nat)}^P \\ - E[Γ] ⊢ f_2 : {(\kw{cons} ~\nat)}^P - \end{array} - ------------------------------------------------ - E[Γ] ⊢ \case(t,P,f_1 |f_2 ) : (P~t) + .. inference:: list example + + \begin{array}{l} + E[Γ] ⊢ t : (\List ~\nat) \\ + E[Γ] ⊢ P : B \\ + [(\List ~\nat)|B] \\ + E[Γ] ⊢ f_1 : {(\kw{nil} ~\nat)}^P \\ + E[Γ] ⊢ f_2 : {(\kw{cons} ~\nat)}^P + \end{array} + ------------------------------------------------ + E[Γ] ⊢ \case(t,P,f_1 |f_2 ) : (P~t) .. _Definition-of-ι-reduction: @@ -1602,7 +1647,7 @@ then the recursive arguments will correspond to :math:`T_i` in which one of the :math:`I_l` occurs. The main rules for being structurally smaller are the following. -Given a variable :math:`y` of type an inductive definition in a declaration +Given a variable :math:`y` of an inductively defined type in a declaration :math:`\ind{r}{Γ_I}{Γ_C}` where :math:`Γ_I` is :math:`[I_1 :A_1 ;…;I_k :A_k]`, and :math:`Γ_C` is :math:`[c_1 :C_1 ;…;c_n :C_n ]`, the terms structurally smaller than :math:`y` are: @@ -1614,16 +1659,16 @@ Given a variable :math:`y` of type an inductive definition in a declaration Each :math:`f_i` corresponds to a type of constructor :math:`C_q ≡ ∀ p_1 :P_1 ,…,∀ p_r :P_r , ∀ y_1 :B_1 , … ∀ y_k :B_k , (I~a_1 … a_k )` and can consequently be written :math:`λ y_1 :B_1' . … λ y_k :B_k'. g_i`. (:math:`B_i'` is - obtained from :math:`B_i` by substituting parameters variables) the variables + obtained from :math:`B_i` by substituting parameters for variables) the variables :math:`y_j` occurring in :math:`g_i` corresponding to recursive arguments :math:`B_i` (the ones in which one of the :math:`I_l` occurs) are structurally smaller than y. -The following definitions are correct, we enter them using the ``Fixpoint`` -command as described in Section :ref:`TODO-1.3.4` and show the internal -representation. +The following definitions are correct, we enter them using the :cmd:`Fixpoint` +command and show the internal representation. .. example:: + .. coqtop:: all Fixpoint plus (n m:nat) {struct n} : nat := @@ -1665,20 +1710,22 @@ for primitive recursive operators. The following reductions are now possible: .. math:: - \def\plus{\mathsf{plus}} - \def\tri{\triangleright_\iota} - \begin{eqnarray*} - \plus~(\nS~(\nS~\nO))~(\nS~\nO) & \tri & \nS~(\plus~(\nS~\nO)~(\nS~\nO))\\ - & \tri & \nS~(\nS~(\plus~\nO~(\nS~\nO)))\\ - & \tri & \nS~(\nS~(\nS~\nO))\\ - \end{eqnarray*} + :nowrap: + + {\def\plus{\mathsf{plus}} + \def\tri{\triangleright_\iota} + \begin{eqnarray*} + \plus~(\nS~(\nS~\nO))~(\nS~\nO) & \tri & \nS~(\plus~(\nS~\nO)~(\nS~\nO))\\ + & \tri & \nS~(\nS~(\plus~\nO~(\nS~\nO)))\\ + & \tri & \nS~(\nS~(\nS~\nO))\\ + \end{eqnarray*}} .. _Mutual-induction: **Mutual induction** The principles of mutual induction can be automatically generated -using the Scheme command described in Section :ref:`TODO-13.1`. +using the Scheme command described in Section :ref:`proofschemes-induction-principles`. .. _Admissible-rules-for-global-environments: @@ -1791,24 +1838,25 @@ definitions can be found in :cite:`Gimenez95b,Gim98,GimCas05`. .. _The-Calculus-of-Inductive-Construction-with-impredicative-Set: -The Calculus of Inductive Construction with impredicative Set +The Calculus of Inductive Constructions with impredicative Set ----------------------------------------------------------------- -|Coq| can be used as a type-checker for the Calculus of Inductive +|Coq| can be used as a type checker for the Calculus of Inductive Constructions with an impredicative sort :math:`\Set` by using the compiler option ``-impredicative-set``. For example, using the ordinary `coqtop` command, the following is rejected, .. example:: + .. coqtop:: all Fail Definition id: Set := forall X:Set,X->X. -while it will type-check, if one uses instead the `coqtop` +while it will type check, if one uses instead the `coqtop` ``-impredicative-set`` option.. The major change in the theory concerns the rule for product formation -in the sort Set, which is extended to a domain in any sort: +in the sort :math:`\Set`, which is extended to a domain in any sort: .. inference:: ProdImp @@ -1821,11 +1869,11 @@ in the sort Set, which is extended to a domain in any sort: This extension has consequences on the inductive definitions which are allowed. In the impredicative system, one can build so-called *large inductive definitions* like the example of second-order existential -quantifier (exSet). +quantifier (:g:`exSet`). There should be restrictions on the eliminations which can be -performed on such definitions. The eliminations rules in the -impredicative system for sort Set become: +performed on such definitions. The elimination rules in the +impredicative system for sort :math:`\Set` become: diff --git a/doc/sphinx/language/coq-library.rst b/doc/sphinx/language/coq-library.rst index 29053d6a57..85474a3e98 100644 --- a/doc/sphinx/language/coq-library.rst +++ b/doc/sphinx/language/coq-library.rst @@ -1,13 +1,8 @@ -.. include:: ../replaces.rst - .. _thecoqlibrary: The |Coq| library ================= -:Source: https://coq.inria.fr/distrib/current/refman/stdlib.html -:Converted by: Pierre Letouzey - .. index:: single: Theories @@ -22,7 +17,7 @@ The |Coq| library is structured into two parts: developments of |Coq| axiomatizations about sets, lists, sorting, arithmetic, etc. This library comes with the system and its modules are directly accessible through the ``Require`` command (see - Section :ref:`TODO-6.5.1-Require`); + Section :ref:`compiled-files`); In addition, user-provided libraries or developments are provided by |Coq| users' community. These libraries and developments are available @@ -51,6 +46,7 @@ at the |Coq| root directory; this includes the modules ``Tactics``. Module ``Logic_Type`` also makes it in the initial state. +.. _init-notations: Notations ~~~~~~~~~ @@ -93,6 +89,8 @@ Notation Precedence Associativity ``_ ^ _`` 30 right ================ ============ =============== +.. _coq-library-logic: + Logic ~~~~~ @@ -200,6 +198,8 @@ The following abbreviations are allowed: The type annotation ``:A`` can be omitted when ``A`` can be synthesized by the system. +.. _coq-equality: + Equality ++++++++ @@ -524,7 +524,7 @@ provides a scope ``nat_scope`` gathering standard notations for common operations (``+``, ``*``) and a decimal notation for numbers, allowing for instance to write ``3`` for :g:`S (S (S O)))`. This also works on the left hand side of a ``match`` expression (see for example -section :ref:`TODO-refine-example`). This scope is opened by default. +section :tacn:`refine`). This scope is opened by default. .. example:: @@ -618,7 +618,7 @@ Finally, it gives the definition of the usual orderings ``le``, Properties of these relations are not initially known, but may be required by the user from modules ``Le`` and ``Lt``. Finally, -``Peano`` gives some lemmas allowing pattern-matching, and a double +``Peano`` gives some lemmas allowing pattern matching, and a double induction principle. .. index:: @@ -703,21 +703,29 @@ fixpoint equation can be proved. Accessing the Type level ~~~~~~~~~~~~~~~~~~~~~~~~ -The basic library includes the definitions of the counterparts of some data-types and logical -quantifiers at the ``Type``: level: negation, pair, and properties -of ``identity``. This is the module ``Logic_Type.v``. +The standard library includes ``Type`` level definitions of counterparts of some +logic concepts and basic lemmas about them. + +The module ``Datatypes`` defines ``identity``, which is the ``Type`` level counterpart +of equality: + +.. index:: + single: identity (term) + +.. coqtop:: in + + Inductive identity (A:Type) (a:A) : A -> Type := + identity_refl : identity a a. + +Some properties of ``identity`` are proved in the module ``Logic_Type``, which also +provides the definition of ``Type`` level negation: .. index:: single: notT (term) - single: prodT (term) - single: pairT (term) .. coqtop:: in Definition notT (A:Type) := A -> False. - Inductive prodT (A B:Type) : Type := pairT (_:A) (_:B). - -At the end, it defines data-types at the ``Type`` level. Tactics ~~~~~~~ @@ -756,7 +764,7 @@ subdirectories: These directories belong to the initial load path of the system, and the modules they provide are compiled at installation time. So they are directly accessible with the command ``Require`` (see -Section :ref:`TODO-6.5.1-Require`). +Section :ref:`compiled-files`). The different modules of the |Coq| standard library are documented online at http://coq.inria.fr/stdlib. @@ -838,6 +846,7 @@ Notation Interpretation Precedence Associativity .. example:: + .. coqtop:: all reset Require Import ZArith. @@ -877,6 +886,7 @@ Notation Interpretation =============== =================== .. example:: + .. coqtop:: all reset Require Import Reals. @@ -887,7 +897,7 @@ Notation Interpretation Some tactics for real numbers +++++++++++++++++++++++++++++ -In addition to the powerful ``ring``, ``field`` and ``fourier`` +In addition to the powerful ``ring``, ``field`` and ``lra`` tactics (see Chapter :ref:`tactics`), there are also: .. tacn:: discrR @@ -896,6 +906,7 @@ tactics (see Chapter :ref:`tactics`), there are also: Proves that two real integer constants are different. .. example:: + .. coqtop:: all reset Require Import DiscrR. @@ -909,6 +920,7 @@ tactics (see Chapter :ref:`tactics`), there are also: Allows unfolding the ``Rabs`` constant and splits corresponding conjunctions. .. example:: + .. coqtop:: all reset Require Import Reals. @@ -923,6 +935,7 @@ tactics (see Chapter :ref:`tactics`), there are also: corresponding to the condition on each operand of the product. .. example:: + .. coqtop:: all reset Require Import Reals. @@ -930,9 +943,8 @@ tactics (see Chapter :ref:`tactics`), there are also: Goal forall x y z:R, x * y * z <> 0. intros; split_Rmult. -These tactics has been written with the tactic language Ltac -described in Chapter :ref:`thetacticlanguage`. - +These tactics has been written with the tactic language |Ltac| +described in Chapter :ref:`ltac`. List library ~~~~~~~~~~~~ diff --git a/doc/sphinx/language/gallina-extensions.rst b/doc/sphinx/language/gallina-extensions.rst index 68066faa30..562ed48171 100644 --- a/doc/sphinx/language/gallina-extensions.rst +++ b/doc/sphinx/language/gallina-extensions.rst @@ -1,5 +1,3 @@ -.. include:: ../replaces.rst - .. _extensionsofgallina: Extensions of |Gallina| @@ -13,43 +11,41 @@ Extensions of |Gallina| Record types ---------------- -The ``Record`` construction is a macro allowing the definition of +The :cmd:`Record` construction is a macro allowing the definition of records as is done in many programming languages. Its syntax is -described in the grammar below. In fact, the ``Record`` macro is more general +described in the grammar below. In fact, the :cmd:`Record` macro is more general than the usual record types, since it allows also for “manifest” -expressions. In this sense, the ``Record`` construction allows defining +expressions. In this sense, the :cmd:`Record` construction allows defining “signatures”. .. _record_grammar: - .. productionlist:: `sentence` - record : `record_keyword` ident [binders] [: sort] := [ident] { [`field` ; … ; `field`] }. + .. productionlist:: sentence + record : `record_keyword` `record_body` with … with `record_body` record_keyword : Record | Inductive | CoInductive - field : name [binders] : type [ where notation ] - : | name [binders] [: term] := term - -In the expression: + record_body : `ident` [ `binders` ] [: `sort` ] := [ `ident` ] { [ `field` ; … ; `field` ] }. + field : `ident` [ `binders` ] : `type` [ where `notation` ] + : | `ident` [ `binders` ] [: `type` ] := `term` -.. cmd:: Record @ident {* @param } {? : @sort} := {? @ident} { {*; @ident {* @binder } : @term } }. +.. cmd:: Record @ident @binders {? : @sort} := {? @ident} { {*; @ident @binders : @type } } -the first identifier `ident` is the name of the defined record and `sort` is its -type. The optional identifier following ``:=`` is the name of its constructor. If it is omitted, -the default name ``Build_``\ `ident`, where `ident` is the record name, is used. If `sort` is -omitted, the default sort is `\Type`. The identifiers inside the brackets are the names of -fields. For a given field `ident`, its type is :g:`forall binder …, term`. -Remark that the type of a particular identifier may depend on a previously-given identifier. Thus the -order of the fields is important. Finally, each `param` is a parameter of the record. + The first identifier :token:`ident` is the name of the defined record and :token:`sort` is its + type. The optional identifier following ``:=`` is the name of its constructor. If it is omitted, + the default name :n:`Build_@ident`, where :token:`ident` is the record name, is used. If :token:`sort` is + omitted, the default sort is :math:`\Type`. The identifiers inside the brackets are the names of + fields. For a given field :token:`ident`, its type is :n:`forall @binders, @type`. + Remark that the type of a particular identifier may depend on a previously-given identifier. Thus the + order of the fields is important. Finally, :token:`binders` are parameters of the record. More generally, a record may have explicitly defined (a.k.a. manifest) -fields. For instance, we might have:: - - Record ident param : sort := { ident₁ : type₁ ; ident₂ := term₂ ; ident₃ : type₃ }. - -in which case the correctness of |type_3| may rely on the instance |term_2| of |ident_2| and |term_2| in turn -may depend on |ident_1|. +fields. For instance, we might have: +:n:`Record @ident @binders : @sort := { @ident__1 : @type__1 ; @ident__2 := @term__2 ; @ident__3 : @type__3 }`. +in which case the correctness of :n:`@type__3` may rely on the instance :n:`@term__2` of :n:`@ident__2` and :n:`@term__2` may in turn depend on :n:`@ident__1`. .. example:: + The set of rational numbers may be defined as: + .. coqtop:: reset all Record Rat : Set := mkRat @@ -65,13 +61,14 @@ depends on both ``top`` and ``bottom``. Let us now see the work done by the ``Record`` macro. First the macro generates a variant type definition with just one constructor: +:n:`Variant @ident {? @binders } : @sort := @ident₀ {? @binders }`. -.. cmd:: Variant @ident {* @params} : @sort := @ident {* (@ident : @term_1)}. +To build an object of type :n:`@ident`, one should provide the constructor +:n:`@ident₀` with the appropriate number of terms filling the fields of the record. -To build an object of type `ident`, one should provide the constructor -|ident_0| with the appropriate number of terms filling the fields of the record. +.. example:: -.. example:: Let us define the rational :math:`1/2`: + Let us define the rational :math:`1/2`: .. coqtop:: in @@ -81,11 +78,13 @@ To build an object of type `ident`, one should provide the constructor Definition half := mkRat true 1 2 (O_S 1) one_two_irred. Check half. +.. FIXME: move this to the main grammar in the spec chapter + .. _record-named-fields-grammar: .. productionlist:: - term : {| [`field_def` ; … ; `field_def`] |} - field_def : name [binders] := `term` + record_term : {| [`field_def` ; … ; `field_def`] |} + field_def : name [binders] := `record_term` Alternatively, the following syntax allows creating objects by using named fields, as shown in this grammar. The fields do not have to be in any particular order, nor do they have @@ -99,19 +98,25 @@ to be all present if the missing ones can be inferred or prompted for Rat_bottom_cond := O_S 1; Rat_irred_cond := one_two_irred |}. -This syntax can be disabled globally for printing by +The following settings let you control the display format for types: + +.. flag:: Printing Records -.. cmd:: Unset Printing Records. + If set, use the record syntax (shown above) as the default display format. -For a given type, one can override this using either +You can override the display format for specified types by adding entries to these tables: -.. cmd:: Add Printing Record @ident. +.. table:: Printing Record @qualid + :name: Printing Record -to get record syntax or + Specifies a set of qualids which are displayed as records. Use the + :cmd:`Add @table` and :cmd:`Remove @table` commands to update the set of qualids. -.. cmd:: Add Printing Constructor @ident. +.. table:: Printing Constructor @qualid + :name: Printing Constructor -to get constructor syntax. + Specifies a set of qualids which are displayed as constructors. Use the + :cmd:`Add @table` and :cmd:`Remove @table` commands to update the set of qualids. This syntax can also be used for pattern matching. @@ -142,23 +147,25 @@ available: Eval compute in half.(top). -It can be activated for printing with +.. flag:: Printing Projections -.. cmd:: Set Printing Projections. + This flag activates the dot notation for printing. -.. example:: + .. example:: - .. coqtop:: all + .. coqtop:: all + + Set Printing Projections. + Check top half. - Set Printing Projections. - Check top half. +.. FIXME: move this to the main grammar in the spec chapter .. _record_projections_grammar: .. productionlist:: terms - term : term `.` ( qualid ) - : | term `.` ( qualid arg … arg ) - : | term `.` ( @`qualid` `term` … `term` ) + projection : projection `.` ( `qualid` ) + : | projection `.` ( `qualid` `arg` … `arg` ) + : | projection `.` ( @`qualid` `term` … `term` ) Syntax of Record projections @@ -169,19 +176,20 @@ and the syntax `term.(@qualid` |term_1| |term_n| `)` to `@qualid` |term_1| `…` In each case, `term` is the object projected and the other arguments are the parameters of the inductive type. -.. note::. Records defined with the ``Record`` keyword are not allowed to be + +.. note:: Records defined with the ``Record`` keyword are not allowed to be recursive (references to the record's name in the type of its field raises an error). To define recursive records, one can use the ``Inductive`` and ``CoInductive`` keywords, resulting in an inductive or co-inductive record. - A *caveat*, however, is that records cannot appear in mutually inductive - (or co-inductive) definitions. + Definition of mutal inductive or co-inductive records are also allowed, as long + as all of the types in the block are records. .. note:: Induction schemes are automatically generated for inductive records. Automatic generation of induction schemes for non-recursive records defined with the ``Record`` keyword can be activated with the - ``Nonrecursive Elimination Schemes`` option (see :ref:`TODO-13.1.1-nonrecursive-elimination-schemes`). + ``Nonrecursive Elimination Schemes`` option (see :ref:`proofschemes-induction-principles`). -.. note::``Structure`` is a synonym of the keyword ``Record``. +.. note:: ``Structure`` is a synonym of the keyword ``Record``. .. warn:: @ident cannot be defined. @@ -189,9 +197,9 @@ other arguments are the parameters of the inductive type. This message is followed by an explanation of this impossibility. There may be three reasons: - #. The name `ident` already exists in the environment (see Section :ref:`TODO-1.3.1-axioms`). + #. The name `ident` already exists in the environment (see :cmd:`Axiom`). #. The body of `ident` uses an incorrect elimination for - `ident` (see Sections :ref:`TODO-1.3.4-fixpoint` and :ref:`TODO-4.5.3-case-expr`). + `ident` (see :cmd:`Fixpoint` and :ref:`Destructors`). #. The type of the projections `ident` depends on previous projections which themselves could not be defined. @@ -208,48 +216,56 @@ other arguments are the parameters of the inductive type. During the definition of the one-constructor inductive definition, all the errors of inductive definitions, as described in Section -:ref:`TODO-1.3.3-inductive-definitions`, may also occur. +:ref:`gallina-inductive-definitions`, may also occur. -**See also** Coercions and records in Section :ref:`TODO-18.9-coercions-and-records` of the chapter devoted to coercions. +.. seealso:: Coercions and records in section :ref:`coercions-classes-as-records` of the chapter devoted to coercions. .. _primitive_projections: Primitive Projections ~~~~~~~~~~~~~~~~~~~~~ -The option ``Set Primitive Projections`` turns on the use of primitive -projections when defining subsequent records (even through the ``Inductive`` -and ``CoInductive`` commands). Primitive projections -extended the Calculus of Inductive Constructions with a new binary -term constructor `r.(p)` representing a primitive projection `p` applied -to a record object `r` (i.e., primitive projections are always applied). -Even if the record type has parameters, these do not appear at -applications of the projection, considerably reducing the sizes of -terms when manipulating parameterized records and typechecking time. -On the user level, primitive projections can be used as a replacement -for the usual defined ones, although there are a few notable differences. - -The internally omitted parameters can be reconstructed at printing time -even though they are absent in the actual AST manipulated by the kernel. This -can be obtained by setting the ``Printing Primitive Projection Parameters`` -flag. Another compatibility printing can be activated thanks to the -``Printing Primitive Projection Compatibility`` option which governs the -printing of pattern-matching over primitive records. +.. flag:: Primitive Projections + + Turns on the use of primitive + projections when defining subsequent records (even through the ``Inductive`` + and ``CoInductive`` commands). Primitive projections + extended the Calculus of Inductive Constructions with a new binary + term constructor `r.(p)` representing a primitive projection `p` applied + to a record object `r` (i.e., primitive projections are always applied). + Even if the record type has parameters, these do not appear at + applications of the projection, considerably reducing the sizes of + terms when manipulating parameterized records and type checking time. + On the user level, primitive projections can be used as a replacement + for the usual defined ones, although there are a few notable differences. + +.. flag:: Printing Primitive Projection Parameters + + This compatibility option reconstructs internally omitted parameters at + printing time (even though they are absent in the actual AST manipulated + by the kernel). + +.. flag:: Printing Primitive Projection Compatibility + + This compatibility option (on by default) governs the + printing of pattern matching over primitive records. Primitive Record Types ++++++++++++++++++++++ -When the ``Set Primitive Projections`` option is on, definitions of +When the :flag:`Primitive Projections` option is on, definitions of record types change meaning. When a type is declared with primitive projections, its :g:`match` construct is disabled (see :ref:`primitive_projections` though). To eliminate the (co-)inductive type, one must use its defined primitive projections. +.. The following paragraph is quite redundant with what is above + For compatibility, the parameters still appear to the user when printing terms even though they are absent in the actual AST manipulated by the kernel. This can be changed by unsetting the -``Printing Primitive Projection Parameters`` flag. Further compatibility +:flag:`Printing Primitive Projection Parameters` flag. Further compatibility printing can be deactivated thanks to the ``Printing Primitive Projection -Compatibility`` option which governs the printing of pattern-matching +Compatibility`` option which governs the printing of pattern matching over primitive records. There are currently two ways to introduce primitive records types: @@ -279,7 +295,7 @@ the folded version delta-reduces to the unfolded version. This allows to precisely mimic the usual unfolding rules of constants. Projections obey the usual ``simpl`` flags of the ``Arguments`` command in particular. There is currently no way to input unfolded primitive projections at the -user-level, and one must use the ``Printing Primitive Projection Compatibility`` +user-level, and one must use the :flag:`Printing Primitive Projection Compatibility` to display unfolded primitive projections as matches and distinguish them from folded ones. @@ -292,7 +308,7 @@ an object of the record type as arguments, and whose body is an application of the unfolded primitive projection of the same name. These constants are used when elaborating partial applications of the projection. One can distinguish them from applications of the primitive -projection if the ``Printing Primitive Projection Parameters`` option +projection if the :flag`Printing Primitive Projection Parameters` option is off: For a primitive projection application, parameters are printed as underscores while for the compatibility projections they are printed as usual. @@ -304,27 +320,28 @@ printed back as :g:`match` constructs. Variants and extensions of :g:`match` ------------------------------------- -.. _extended pattern-matching: +.. _mult-match: -Multiple and nested pattern-matching +Multiple and nested pattern matching ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -The basic version of :g:`match` allows pattern-matching on simple +The basic version of :g:`match` allows pattern matching on simple patterns. As an extension, multiple nested patterns or disjunction of patterns are allowed, as in ML-like languages. The extension just acts as a macro that is expanded during parsing into a sequence of match on simple patterns. Especially, a construction defined using the extended match is generally printed -under its expanded form (see ``Set Printing Matching`` in :ref:`controlling-match-pp`). +under its expanded form (see :flag:`Printing Matching`). -See also: :ref:`extended pattern-matching`. +.. seealso:: :ref:`extendedpatternmatching`. +.. _if-then-else: Pattern-matching on boolean values: the if expression ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -For inductive types with exactly two constructors and for pattern-matching +For inductive types with exactly two constructors and for pattern matching expressions that do not depend on the arguments of the constructors, it is possible to use a ``if … then … else`` notation. For instance, the definition @@ -366,6 +383,7 @@ we have the following equivalence Notice that the printing uses the :g:`if` syntax because `sumbool` is declared as such (see :ref:`controlling-match-pp`). +.. _irrefutable-patterns: Irrefutable patterns: the destructuring let variants ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -462,176 +480,93 @@ of :g:`match` expressions. Printing nested patterns +++++++++++++++++++++++++ -The Calculus of Inductive Constructions knows pattern-matching only -over simple patterns. It is however convenient to re-factorize nested -pattern-matching into a single pattern-matching over a nested -pattern. |Coq|’s printer tries to do such limited re-factorization. +.. flag:: Printing Matching -.. cmd:: Set Printing Matching. + The Calculus of Inductive Constructions knows pattern matching only + over simple patterns. It is however convenient to re-factorize nested + pattern matching into a single pattern matching over a nested + pattern. -This tells |Coq| to try to use nested patterns. This is the default -behavior. + When this option is on (default), |Coq|’s printer tries to do such + limited re-factorization. + Turning it off tells |Coq| to print only simple pattern matching problems + in the same way as the |Coq| kernel handles them. -.. cmd:: Unset Printing Matching. - -This tells |Coq| to print only simple pattern-matching problems in the -same way as the |Coq| kernel handles them. - -.. cmd:: Test Printing Matching. - -This tells if the printing matching mode is on or off. The default is -on. Factorization of clauses with same right-hand side ++++++++++++++++++++++++++++++++++++++++++++++++++ -When several patterns share the same right-hand side, it is additionally -possible to share the clauses using disjunctive patterns. Assuming that the -printing matching mode is on, whether |Coq|'s printer shall try to do this kind -of factorization is governed by the following commands: - -.. cmd:: Set Printing Factorizable Match Patterns. - -This tells |Coq|'s printer to try to use disjunctive patterns. This is the -default behavior. - -.. cmd:: Unset Printing Factorizable Match Patterns. +.. flag:: Printing Factorizable Match Patterns -This tells |Coq|'s printer not to try to use disjunctive patterns. - -.. cmd:: Test Printing Factorizable Match Patterns. - -This tells if the factorization of clauses with same right-hand side is on or -off. + When several patterns share the same right-hand side, it is additionally + possible to share the clauses using disjunctive patterns. Assuming that the + printing matching mode is on, this option (on by default) tells |Coq|'s + printer to try to do this kind of factorization. Use of a default clause +++++++++++++++++++++++ -When several patterns share the same right-hand side which do not depend on the -arguments of the patterns, yet an extra factorization is possible: the -disjunction of patterns can be replaced with a `_` default clause. Assuming that -the printing matching mode and the factorization mode are on, whether |Coq|'s -printer shall try to use a default clause is governed by the following commands: - -.. cmd:: Set Printing Allow Default Clause. - -This tells |Coq|'s printer to use a default clause when relevant. This is the -default behavior. - -.. cmd:: Unset Printing Allow Default Clause. - -This tells |Coq|'s printer not to use a default clause. - -.. cmd:: Test Printing Allow Default Clause. +.. flag:: Printing Allow Match Default Clause -This tells if the use of a default clause is allowed. + When several patterns share the same right-hand side which do not depend on the + arguments of the patterns, yet an extra factorization is possible: the + disjunction of patterns can be replaced with a `_` default clause. Assuming that + the printing matching mode and the factorization mode are on, this option (on by + default) tells |Coq|'s printer to use a default clause when relevant. Printing of wildcard patterns ++++++++++++++++++++++++++++++ -Some variables in a pattern may not occur in the right-hand side of -the pattern-matching clause. There are options to control the display -of these variables. +.. flag:: Printing Wildcard -.. cmd:: Set Printing Wildcard. - -The variables having no occurrences in the right-hand side of the -pattern-matching clause are just printed using the wildcard symbol -“_”. - -.. cmd:: Unset Printing Wildcard. - -The variables, even useless, are printed using their usual name. But -some non-dependent variables have no name. These ones are still -printed using a “_”. - -.. cmd:: Test Printing Wildcard. - -This tells if the wildcard printing mode is on or off. The default is -to print wildcard for useless variables. + Some variables in a pattern may not occur in the right-hand side of + the pattern matching clause. When this option is on (default), the + variables having no occurrences in the right-hand side of the + pattern matching clause are just printed using the wildcard symbol + “_”. Printing of the elimination predicate +++++++++++++++++++++++++++++++++++++ -In most of the cases, the type of the result of a matched term is -mechanically synthesizable. Especially, if the result type does not -depend of the matched term. - -.. cmd:: Set Printing Synth. +.. flag:: Printing Synth -The result type is not printed when |Coq| knows that it can re- -synthesize it. - -.. cmd:: Unset Printing Synth. - -This forces the result type to be always printed. - -.. cmd:: Test Printing Synth. - -This tells if the non-printing of synthesizable types is on or off. -The default is to not print synthesizable types. + In most of the cases, the type of the result of a matched term is + mechanically synthesizable. Especially, if the result type does not + depend of the matched term. When this option is on (default), + the result type is not printed when |Coq| knows that it can re- + synthesize it. Printing matching on irrefutable patterns ++++++++++++++++++++++++++++++++++++++++++ -If an inductive type has just one constructor, pattern-matching can be +If an inductive type has just one constructor, pattern matching can be written using the first destructuring let syntax. -.. cmd:: Add Printing Let @ident. - - This adds `ident` to the list of inductive types for which pattern-matching - is written using a let expression. - -.. cmd:: Remove Printing Let @ident. +.. table:: Printing Let @qualid + :name: Printing Let - This removes ident from this list. Note that removing an inductive - type from this list has an impact only for pattern-matching written - using :g:`match`. Pattern-matching explicitly written using a destructuring - :g:`let` are not impacted. - -.. cmd:: Test Printing Let for @ident. - - This tells if `ident` belongs to the list. - -.. cmd:: Print Table Printing Let. - - This prints the list of inductive types for which pattern-matching is - written using a let expression. - - The list of inductive types for which pattern-matching is written - using a :g:`let` expression is managed synchronously. This means that it is - sensitive to the command ``Reset``. + Specifies a set of qualids for which pattern matching is displayed using a let expression. + Note that this only applies to pattern matching instances entered with :g:`match`. + It doesn't affect pattern matching explicitly entered with a destructuring + :g:`let`. + Use the :cmd:`Add @table` and :cmd:`Remove @table` commands to update this set. Printing matching on booleans +++++++++++++++++++++++++++++ -If an inductive type is isomorphic to the boolean type, pattern-matching -can be written using ``if`` … ``then`` … ``else`` …: - -.. cmd:: Add Printing If @ident. +If an inductive type is isomorphic to the boolean type, pattern matching +can be written using ``if`` … ``then`` … ``else`` …. This table controls +which types are written this way: - This adds ident to the list of inductive types for which pattern-matching is - written using an if expression. +.. table:: Printing If @qualid + :name: Printing If -.. cmd:: Remove Printing If @ident. - - This removes ident from this list. - -.. cmd:: Test Printing If for @ident. - - This tells if ident belongs to the list. - -.. cmd:: Print Table Printing If. - - This prints the list of inductive types for which pattern-matching is - written using an if expression. - -The list of inductive types for which pattern-matching is written -using an ``if`` expression is managed synchronously. This means that it is -sensitive to the command ``Reset``. + Specifies a set of qualids for which pattern matching is displayed using + ``if`` … ``then`` … ``else`` …. Use the :cmd:`Add @table` and :cmd:`Remove @table` + commands to update this set. This example emphasizes what the printing options offer. @@ -662,26 +597,26 @@ Advanced recursive functions The following experimental command is available when the ``FunInd`` library has been loaded via ``Require Import FunInd``: -.. cmd:: Function @ident {* @binder} { @decrease_annot } : @type := @term. +.. cmd:: Function @ident {* @binder} { @decrease_annot } : @type := @term -This command can be seen as a generalization of ``Fixpoint``. It is actually a wrapper -for several ways of defining a function *and other useful related -objects*, namely: an induction principle that reflects the recursive -structure of the function (see Section :ref:`TODO-8.5.5-functional-induction`) and its fixpoint equality. -The meaning of this declaration is to define a function ident, -similarly to ``Fixpoint`. Like in ``Fixpoint``, the decreasing argument must -be given (unless the function is not recursive), but it might not -necessarily be *structurally* decreasing. The point of the {} annotation -is to name the decreasing argument *and* to describe which kind of -decreasing criteria must be used to ensure termination of recursive -calls. + This command can be seen as a generalization of ``Fixpoint``. It is actually a wrapper + for several ways of defining a function *and other useful related + objects*, namely: an induction principle that reflects the recursive + structure of the function (see :tacn:`function induction`) and its fixpoint equality. + The meaning of this declaration is to define a function ident, + similarly to ``Fixpoint``. Like in ``Fixpoint``, the decreasing argument must + be given (unless the function is not recursive), but it might not + necessarily be *structurally* decreasing. The point of the {} annotation + is to name the decreasing argument *and* to describe which kind of + decreasing criteria must be used to ensure termination of recursive + calls. The ``Function`` construction also enjoys the ``with`` extension to define mutually recursive definitions. However, this feature does not work for non structurally recursive functions. -See the documentation of functional induction (:ref:`TODO-8.5.5-functional-induction`) -and ``Functional Scheme`` (:ref:`TODO-13.2-functional-scheme`) for how to use +See the documentation of functional induction (:tacn:`function induction`) +and ``Functional Scheme`` (:ref:`functional-scheme`) for how to use the induction principle to easily reason about the function. Remark: To obtain the right principle, it is better to put rigid @@ -713,7 +648,7 @@ than like this: *Limitations* -|term_0| must be built as a *pure pattern-matching tree* (:g:`match … with`) +|term_0| must be built as a *pure pattern matching tree* (:g:`match … with`) with applications only *at the end* of each branch. Function does not support partial application of the function being @@ -729,30 +664,35 @@ presence of partial application of `wrong` in the body of For now, dependent cases are not treated for non structurally terminating functions. -.. exn:: The recursive argument must be specified -.. exn:: No argument name @ident -.. exn:: Cannot use mutual definition with well-founded recursion or measure +.. exn:: The recursive argument must be specified. + :undocumented: -.. warn:: Cannot define graph for @ident +.. exn:: No argument name @ident. + :undocumented: - The generation of the graph relation (`R_ident`) used to compute the induction scheme of ident - raised a typing error. Only `ident` is defined; the induction scheme - will not be generated. This error happens generally when: +.. exn:: Cannot use mutual definition with well-founded recursion or measure. + :undocumented: - - the definition uses pattern matching on dependent types, - which ``Function`` cannot deal with yet. - - the definition is not a *pattern-matching tree* as explained above. +.. warn:: Cannot define graph for @ident. -.. warn:: Cannot define principle(s) for @ident + The generation of the graph relation (:n:`R_@ident`) used to compute the induction scheme of ident + raised a typing error. Only :token:`ident` is defined; the induction scheme + will not be generated. This error happens generally when: - The generation of the graph relation (`R_ident`) succeeded but the induction principle - could not be built. Only `ident` is defined. Please report. + - the definition uses pattern matching on dependent types, + which ``Function`` cannot deal with yet. + - the definition is not a *pattern matching tree* as explained above. -.. warn:: Cannot build functional inversion principle +.. warn:: Cannot define principle(s) for @ident. - `functional inversion` will not be available for the function. + The generation of the graph relation (:n:`R_@ident`) succeeded but the induction principle + could not be built. Only :token:`ident` is defined. Please report. -See also: :ref:`TODO-13.2-generating-ind-principles` and ref:`TODO-8.5.5-functional-induction` +.. warn:: Cannot build functional inversion principle. + + :tacn:`functional inversion` will not be available for the function. + +.. seealso:: :ref:`functional-scheme` and :tacn:`function induction` Depending on the ``{…}`` annotation, different definition mechanisms are used by ``Function``. A more precise description is given below. @@ -763,7 +703,7 @@ used by ``Function``. A more precise description is given below. the following are defined: + `ident_rect`, `ident_rec` and `ident_ind`, which reflect the pattern - matching structure of `term` (see the documentation of :ref:`TODO-1.3.3-Inductive`); + matching structure of `term` (see :cmd:`Inductive`); + The inductive `R_ident` corresponding to the graph of `ident` (silently); + `ident_complete` and `ident_correct` which are inversion information linking the function and its graph. @@ -776,7 +716,7 @@ used by ``Function``. A more precise description is given below. + The fixpoint equation of `ident`: `ident_equation`. .. cmdv:: Function @ident {* @binder } { measure @term @ident } : @type := @term -.. cmdv:: Function @ident {* @binder } { wf @term @ident } : @type := @term + Function @ident {* @binder } { wf @term @ident } : @type := @term Defines a recursive function by well-founded recursion. The module ``Recdef`` of the standard library must be loaded for this feature. The ``{}`` @@ -812,21 +752,23 @@ used by ``Function``. A more precise description is given below. hand. Remark: Proof obligations are presented as several subgoals belonging to a Lemma `ident`\ :math:`_{\sf tcc}`. +.. _section-mechanism: Section mechanism ----------------- The sectioning mechanism can be used to to organize a proof in structured sections. Then local declarations become available (see -Section :ref:`TODO-1.3.2-Definitions`). +Section :ref:`gallina-definitions`). -.. cmd:: Section @ident. +.. cmd:: Section @ident - This command is used to open a section named `ident`. + This command is used to open a section named :token:`ident`. + Section names do not need to be unique. -.. cmd:: End @ident. +.. cmd:: End @ident This command closes the section named `ident`. After closing of the section, the local declarations (variables and local definitions) get @@ -859,11 +801,11 @@ Section :ref:`TODO-1.3.2-Definitions`). Notice the difference between the value of `x’` and `x’’` inside section `s1` and outside. - .. exn:: This is not the last opened section - -**Remarks:** + .. exn:: This is not the last opened section. + :undocumented: -#. Most commands, like ``Hint``, ``Notation``, option management, … which +.. note:: + Most commands, like ``Hint``, ``Notation``, option management, … which appear inside a section are canceled when the section is closed. @@ -888,44 +830,44 @@ together, as well as a means of massive abstraction. In the syntax of module application, the ! prefix indicates that any `Inline` directive in the type of the functor arguments will be ignored -(see :ref:`named_module_type` below). +(see the ``Module Type`` command below). -.. cmd:: Module @ident. +.. cmd:: Module @ident This command is used to start an interactive module named `ident`. -.. cmdv:: Module @ident {* @module_binding}. +.. cmdv:: Module @ident {* @module_binding} Starts an interactive functor with parameters given by module_bindings. -.. cmdv:: Module @ident : @module_type. +.. cmdv:: Module @ident : @module_type Starts an interactive module specifying its module type. -.. cmdv:: Module @ident {* @module_binding} : @module_type. +.. cmdv:: Module @ident {* @module_binding} : @module_type Starts an interactive functor with parameters given by the list of `module binding`, and output module type `module_type`. -.. cmdv:: Module @ident <: {+<: @module_type }. +.. cmdv:: Module @ident <: {+<: @module_type } Starts an interactive module satisfying each `module_type`. - .. cmdv:: Module @ident {* @module_binding} <: {+<; @module_type }. + .. cmdv:: Module @ident {* @module_binding} <: {+<: @module_type }. Starts an interactive functor with parameters given by the list of `module_binding`. The output module type is verified against each `module_type`. -.. cmdv:: Module [ Import | Export ]. +.. cmdv:: Module [ Import | Export ] Behaves like ``Module``, but automatically imports or exports the module. Reserved commands inside an interactive module ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -.. cmd:: Include @module. +.. cmd:: Include @module Includes the content of module in the current interactive module. Here module can be a module expression or a module @@ -933,101 +875,104 @@ Reserved commands inside an interactive module expression then the system tries to instantiate module by the current interactive module. -.. cmd:: Include {+<+ @module}. +.. cmd:: Include {+<+ @module} - is a shortcut for the commands ``Include`` `module` for each `module`. + is a shortcut for the commands :n:`Include @module` for each :token:`module`. -.. cmd:: End @ident. +.. cmd:: End @ident - This command closes the interactive module `ident`. If the module type + This command closes the interactive module :token:`ident`. If the module type was given the content of the module is matched against it and an error is signaled if the matching fails. If the module is basic (is not a functor) its components (constants, inductive types, submodules etc.) are now available through the dot notation. - .. exn:: No such label @ident + .. exn:: No such label @ident. + :undocumented: - .. exn:: Signature components for label @ident do not match + .. exn:: Signature components for label @ident do not match. + :undocumented: - .. exn:: This is not the last opened module + .. exn:: This is not the last opened module. + :undocumented: -.. cmd:: Module @ident := @module_expression. +.. cmd:: Module @ident := @module_expression - This command defines the module identifier `ident` to be equal - to `module_expression`. + This command defines the module identifier :token:`ident` to be equal + to :token:`module_expression`. - .. cmdv:: Module @ident {* @module_binding} := @module_expression. + .. cmdv:: Module @ident {* @module_binding} := @module_expression - Defines a functor with parameters given by the list of `module_binding` and body `module_expression`. + Defines a functor with parameters given by the list of :token:`module_binding` and body :token:`module_expression`. - .. cmdv:: Module @ident {* @module_binding} : @module_type := @module_expression. + .. cmdv:: Module @ident {* @module_binding} : @module_type := @module_expression - Defines a functor with parameters given by the list of `module_binding` (possibly none), and output module type `module_type`, - with body `module_expression`. + Defines a functor with parameters given by the list of :token:`module_binding` (possibly none), and output module type :token:`module_type`, + with body :token:`module_expression`. - .. cmdv:: Module @ident {* @module_binding} <: {+<: @module_type} := @module_expression. + .. cmdv:: Module @ident {* @module_binding} <: {+<: @module_type} := @module_expression - Defines a functor with parameters given by module_bindings (possibly none) with body `module_expression`. + Defines a functor with parameters given by module_bindings (possibly none) with body :token:`module_expression`. The body is checked against each |module_type_i|. - .. cmdv:: Module @ident {* @module_binding} := {+<+ @module_expression}. + .. cmdv:: Module @ident {* @module_binding} := {+<+ @module_expression} - is equivalent to an interactive module where each `module_expression` is included. + is equivalent to an interactive module where each :token:`module_expression` is included. -.. _named_module_type: +.. cmd:: Module Type @ident -.. cmd:: Module Type @ident. + This command is used to start an interactive module type :token:`ident`. -This command is used to start an interactive module type `ident`. + .. cmdv:: Module Type @ident {* @module_binding} - .. cmdv:: Module Type @ident {* @module_binding}. - - Starts an interactive functor type with parameters given by `module_bindings`. + Starts an interactive functor type with parameters given by :token:`module_bindings`. Reserved commands inside an interactive module type: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -.. cmd:: Include @module. +.. cmd:: Include @module Same as ``Include`` inside a module. -.. cmd:: Include {+<+ @module}. +.. cmd:: Include {+<+ @module} - is a shortcut for the command ``Include`` `module` for each `module`. + This is a shortcut for the command :n:`Include @module` for each :token:`module`. -.. cmd:: @assumption_keyword Inline @assums. +.. cmd:: @assumption_keyword Inline @assums + :name: Inline The instance of this assumption will be automatically expanded at functor application, except when this functor application is prefixed by a ``!`` annotation. -.. cmd:: End @ident. +.. cmd:: End @ident - This command closes the interactive module type `ident`. + This command closes the interactive module type :token:`ident`. - .. exn:: This is not the last opened module type + .. exn:: This is not the last opened module type. + :undocumented: -.. cmd:: Module Type @ident := @module_type. +.. cmd:: Module Type @ident := @module_type - Defines a module type `ident` equal to `module_type`. + Defines a module type :token:`ident` equal to :token:`module_type`. - .. cmdv:: Module Type @ident {* @module_binding} := @module_type. + .. cmdv:: Module Type @ident {* @module_binding} := @module_type - Defines a functor type `ident` specifying functors taking arguments `module_bindings` and - returning `module_type`. + Defines a functor type :token:`ident` specifying functors taking arguments :token:`module_bindings` and + returning :token:`module_type`. - .. cmdv:: Module Type @ident {* @module_binding} := {+<+ @module_type }. + .. cmdv:: Module Type @ident {* @module_binding} := {+<+ @module_type } - is equivalent to an interactive module type were each `module_type` is included. + is equivalent to an interactive module type were each :token:`module_type` is included. -.. cmd:: Declare Module @ident : @module_type. +.. cmd:: Declare Module @ident : @module_type - Declares a module `ident` of type `module_type`. + Declares a module :token:`ident` of type :token:`module_type`. - .. cmdv:: Declare Module @ident {* @module_binding} : @module_type. + .. cmdv:: Declare Module @ident {* @module_binding} : @module_type - Declares a functor with parameters given by the list of `module_binding` and output module type - `module_type`. + Declares a functor with parameters given by the list of :token:`module_binding` and output module type + :token:`module_type`. .. example:: @@ -1122,7 +1067,7 @@ The definition of ``N`` using the module type expression ``SIG`` with Module N : SIG' := M. -If we just want to be sure that the our implementation satisfies a +If we just want to be sure that our implementation satisfies a given module type without restricting the interface, we can use a transparent constraint @@ -1188,107 +1133,109 @@ some of the fields and give one of its possible implementations: Notice that ``M`` is a correct body for the component ``M2`` since its ``T`` component is equal ``nat`` and hence ``M1.T`` as specified. -**Remarks:** +.. note:: -#. Modules and module types can be nested components of each other. -#. One can have sections inside a module or a module type, but not a - module or a module type inside a section. -#. Commands like ``Hint`` or ``Notation`` can also appear inside modules and - module types. Note that in case of a module definition like: + #. Modules and module types can be nested components of each other. + #. One can have sections inside a module or a module type, but not a + module or a module type inside a section. + #. Commands like ``Hint`` or ``Notation`` can also appear inside modules and + module types. Note that in case of a module definition like: -:: + :: - Module N : SIG := M. + Module N : SIG := M. -or:: + or:: - Module N : SIG. … End N. + Module N : SIG. … End N. -hints and the like valid for ``N`` are not those defined in ``M`` (or the module body) but the ones defined -in ``SIG``. + hints and the like valid for ``N`` are not those defined in ``M`` + (or the module body) but the ones defined in ``SIG``. .. _import_qualid: -.. cmd:: Import @qualid. +.. cmd:: Import @qualid If `qualid` denotes a valid basic module (i.e. its module type is a signature), makes its components available by their short names. -.. example:: + .. example:: - .. coqtop:: reset all + .. coqtop:: reset all - Module Mod. + Module Mod. - Definition T:=nat. + Definition T:=nat. - Check T. + Check T. - End Mod. + End Mod. - Check Mod.T. + Check Mod.T. - Fail Check T. + Fail Check T. - Import Mod. + Import Mod. - Check T. + Check T. -Some features defined in modules are activated only when a module is -imported. This is for instance the case of notations (see :ref:`TODO-12.1-Notations`). + Some features defined in modules are activated only when a module is + imported. This is for instance the case of notations (see :ref:`Notations`). -Declarations made with the Local flag are never imported by theImport -command. Such declarations are only accessible through their fully -qualified name. + Declarations made with the ``Local`` flag are never imported by the :cmd:`Import` + command. Such declarations are only accessible through their fully + qualified name. -.. example:: + .. example:: - .. coqtop:: all + .. coqtop:: all - Module A. + Module A. - Module B. + Module B. - Local Definition T := nat. + Local Definition T := nat. - End B. + End B. - End A. + End A. - Import A. + Import A. - Fail Check B.T. + Fail Check B.T. .. cmdv:: Export @qualid + :name: Export When the module containing the command Export qualid is imported, qualid is imported as well. - .. exn:: @qualid is not a module + .. exn:: @qualid is not a module. + :undocumented: .. warn:: Trying to mask the absolute name @qualid! + :undocumented: -.. cmd:: Print Module @ident. - - Prints the module type and (optionally) the body of the module `ident`. +.. cmd:: Print Module @ident -.. cmd:: Print Module Type @ident. + Prints the module type and (optionally) the body of the module :n:`@ident`. - Prints the module type corresponding to `ident`. +.. cmd:: Print Module Type @ident -.. opt:: Short Module Printing + Prints the module type corresponding to :n:`@ident`. - This option (off by default) disables the printing of the types of fields, - leaving only their names, for the commands ``Print Module`` and ``Print Module Type``. +.. flag:: Short Module Printing -.. cmd:: Locate Module @qualid. - - Prints the full name of the module `qualid`. + This option (off by default) disables the printing of the types of fields, + leaving only their names, for the commands :cmd:`Print Module` and + :cmd:`Print Module Type`. Libraries and qualified names --------------------------------- +.. _names-of-libraries: + Names of libraries ~~~~~~~~~~~~~~~~~~ @@ -1296,15 +1243,16 @@ The theories developed in |Coq| are stored in *library files* which are hierarchically classified into *libraries* and *sublibraries*. To express this hierarchy, library names are represented by qualified identifiers qualid, i.e. as list of identifiers separated by dots (see -:ref:`TODO-1.2.3-identifiers`). For instance, the library file ``Mult`` of the standard +:ref:`gallina-identifiers`). For instance, the library file ``Mult`` of the standard |Coq| library ``Arith`` is named ``Coq.Arith.Mult``. The identifier that starts the name of a library is called a *library root*. All library files of the standard library of |Coq| have the reserved root |Coq| but library -file names based on other roots can be obtained by using |Coq| commands -(coqc, coqtop, coqdep, …) options ``-Q`` or ``-R`` (see :ref:`TODO-14.3.3-command-line-options`). +filenames based on other roots can be obtained by using |Coq| commands +(coqc, coqtop, coqdep, …) options ``-Q`` or ``-R`` (see :ref:`command-line-options`). Also, when an interactive |Coq| session starts, a library of root ``Top`` is -started, unless option ``-top`` or ``-notop`` is set (see :ref:`TODO-14.3.3-command-line-options`). +started, unless option ``-top`` or ``-notop`` is set (see :ref:`command-line-options`). +.. _qualified-names: Qualified names ~~~~~~~~~~~~~~~ @@ -1333,19 +1281,19 @@ short name (or even same partially qualified names as soon as the full names are different). Notice that the notion of absolute, partially qualified and short -names also applies to library file names. +names also applies to library filenames. **Visibility** |Coq| maintains a table called the name table which maps partially qualified names of constructions to absolute names. This table is updated by the -commands ``Require`` (see :ref:`TODO-6.5.1-Require`), Import and Export (see :ref:`import_qualid`) and +commands :cmd:`Require`, :cmd:`Import` and :cmd:`Export` and also each time a new declaration is added to the context. An absolute name is called visible from a given short or partially qualified name when this latter name is enough to denote it. This means that the short or partially qualified name is mapped to the absolute name in |Coq| name table. Definitions flagged as Local are only accessible with -their fully qualified name (see :ref:`TODO-1.3.2-definitions`). +their fully qualified name (see :ref:`gallina-definitions`). It may happen that a visible name is hidden by the short name or a qualified name of another construction. In this case, the name that @@ -1367,16 +1315,15 @@ accessible, absolute names can never be hidden. Locate nat. -See also: Command Locate in :ref:`TODO-6.3.10-locate-qualid` and Locate Library in -:ref:`TODO-6.6.11-locate-library`. +.. seealso:: Commands :cmd:`Locate` and :cmd:`Locate Library`. +.. _libraries-and-filesystem: Libraries and filesystem ~~~~~~~~~~~~~~~~~~~~~~~~ -Please note that the questions described here have been subject to -redesign in |Coq| v8.5. Former versions of |Coq| use the same terminology -to describe slightly different things. +.. note:: The questions described here have been subject to redesign in |Coq| 8.5. + Former versions of |Coq| use the same terminology to describe slightly different things. Compiled files (``.vo`` and ``.vio``) store sub-libraries. In order to refer to them inside |Coq|, a translation from file-system names to |Coq| names @@ -1392,7 +1339,7 @@ folder ``path/fOO/Bar`` maps to ``Lib.fOO.Bar``. Subdirectories corresponding to invalid |Coq| identifiers are skipped, and, by convention, subdirectories named ``CVS`` or ``_darcs`` are skipped too. -Thanks to this mechanism, .vo files are made available through the +Thanks to this mechanism, ``.vo`` files are made available through the logical name of the folder they are in, extended with their own basename. For example, the name associated to the file ``path/fOO/Bar/File.vo`` is ``Lib.fOO.Bar.File``. The same caveat applies for @@ -1403,24 +1350,24 @@ wrong loadpath afterwards. Some folders have a special status and are automatically put in the path. |Coq| commands associate automatically a logical path to files in the repository trees rooted at the directory from where the command is -launched, coqlib/user-contrib/, the directories listed in the -`$COQPATH`, `${XDG_DATA_HOME}/coq/` and `${XDG_DATA_DIRS}/coq/` -environment variables (see`http://standards.freedesktop.org/basedir- -spec/basedir-spec-latest.html`_) with the same physical-to-logical -translation and with an empty logical prefix. +launched, ``coqlib/user-contrib/``, the directories listed in the +``$COQPATH``, ``${XDG_DATA_HOME}/coq/`` and ``${XDG_DATA_DIRS}/coq/`` +environment variables (see `XDG base directory specification +<http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html>`_) +with the same physical-to-logical translation and with an empty logical prefix. The command line option ``-R`` is a variant of ``-Q`` which has the strictly same behavior regarding loadpaths, but which also makes the corresponding ``.vo`` files available through their short names in a way -not unlike the ``Import`` command (see :ref:`import_qualid`). For instance, ``-R`` `path` ``Lib`` -associates to the ``filepath/fOO/Bar/File.vo`` the logical name +not unlike the ``Import`` command (see :ref:`here <import_qualid>`). For instance, ``-R`` `path` ``Lib`` +associates to the file path `path`\ ``/path/fOO/Bar/File.vo`` the logical name ``Lib.fOO.Bar.File``, but allows this file to be accessed through the short names ``fOO.Bar.File,Bar.File`` and ``File``. If several files with identical base name are present in different subdirectories of a recursive loadpath, which of these files is found first may be system- dependent and explicit qualification is recommended. The ``From`` argument of the ``Require`` command can be used to bypass the implicit shortening -by providing an absolute root to the required file (see :ref:`TODO-6.5.1-require-qualid`). +by providing an absolute root to the required file (see :ref:`compiled-files`). There also exists another independent loadpath mechanism attached to OCaml object files (``.cmo`` or ``.cmxs``) rather than |Coq| object @@ -1428,11 +1375,12 @@ files as described above. The OCaml loadpath is managed using the option ``-I`` `path` (in the OCaml world, there is neither a notion of logical name prefix nor a way to access files in subdirectories of path). See the command ``Declare`` ``ML`` ``Module`` in -:ref:`TODO-6.5-compiled-files` to understand the need of the OCaml loadpath. +:ref:`compiled-files` to understand the need of the OCaml loadpath. -See :ref:`TODO-14.3.3-command-line-options` for a more general view over the |Coq| command +See :ref:`command-line-options` for a more general view over the |Coq| command line options. +.. _ImplicitArguments: Implicit arguments ------------------ @@ -1477,7 +1425,9 @@ For instance, the first argument of in module ``List.v`` is strict because :g:`list` is an inductive type and :g:`A` will always be inferable from the type :g:`list A` of the third argument of -:g:`cons`. On the contrary, the second argument of a term of type +:g:`cons`. Also, the first argument of :g:`cons` is strict with respect to the second one, +since the first argument is exactly the type of the second argument. +On the contrary, the second argument of a term of type :: forall P:nat->Prop, forall n:nat, P n -> ex nat P @@ -1548,11 +1498,11 @@ inserted. In the second case, the function is considered to be implicitly applied to the implicit arguments it is waiting for: one says that the implicit argument is maximally inserted. -Each implicit argument can be declared to have to be inserted -maximally or non maximally. This can be governed argument per argument -by the command ``Implicit Arguments`` (see Section :ref:`declare-implicit-args`) or globally by the -command ``Set Maximal Implicit Insertion`` (see Section :ref:`controlling-insertion-implicit-args`). -See also :ref:`displaying-implicit-args`. +Each implicit argument can be declared to have to be inserted maximally or non +maximally. This can be governed argument per argument by the command +:cmd:`Arguments (implicits)` or globally by the :flag:`Maximal Implicit Insertion` option. + +.. seealso:: :ref:`displaying-implicit-args`. Casual use of implicit arguments @@ -1564,6 +1514,8 @@ force the given argument to be guessed by replacing it by “_”. If possible, the correct argument will be automatically generated. .. exn:: Cannot infer a term for this placeholder. + :name: Cannot infer a term for this placeholder. (Casual use of implicit arguments) + :undocumented: |Coq| was not able to deduce an instantiation of a “_”. @@ -1603,7 +1555,7 @@ absent in every situation but still be able to specify it if needed: The syntax is supported in all top-level definitions: -``Definition``, ``Fixpoint``, ``Lemma`` and so on. For (co-)inductive datatype +:cmd:`Definition`, :cmd:`Fixpoint`, :cmd:`Lemma` and so on. For (co-)inductive datatype declarations, the semantics are the following: an inductive parameter declared as an implicit argument need not be repeated in the inductive definition but will become implicit for the constructors of the @@ -1624,37 +1576,39 @@ usual implicit arguments disambiguation syntax. Declaring Implicit Arguments ++++++++++++++++++++++++++++ -To set implicit arguments *a posteriori*, one can use the command: -.. cmd:: Arguments @qualid {* @possibly_bracketed_ident }. -where the list of `possibly_bracketed_ident` is a prefix of the list of -arguments of `qualid` where the ones to be declared implicit are -surrounded by square brackets and the ones to be declared as maximally -inserted implicits are surrounded by curly braces. +.. cmd:: Arguments @qualid {* [ @ident ] | @ident } + :name: Arguments (implicits) -After the above declaration is issued, implicit arguments can just -(and have to) be skipped in any expression involving an application -of `qualid`. + This command is used to set implicit arguments *a posteriori*, + where the list of possibly bracketed :token:`ident` is a prefix of the list of + arguments of :token:`qualid` where the ones to be declared implicit are + surrounded by square brackets and the ones to be declared as maximally + inserted implicits are surrounded by curly braces. -Implicit arguments can be cleared with the following syntax: + After the above declaration is issued, implicit arguments can just + (and have to) be skipped in any expression involving an application + of :token:`qualid`. -.. cmd:: Arguments @qualid : clear implicits. +.. cmd:: Arguments @qualid : clear implicits -.. cmdv:: Global Arguments @qualid {* @possibly_bracketed_ident } + This command clears implicit arguments. - Says to recompute the implicit arguments of - `qualid` after ending of the current section if any, enforcing the +.. cmdv:: Global Arguments @qualid {* [ @ident ] | @ident } + + This command is used to recompute the implicit arguments of + :token:`qualid` after ending of the current section if any, enforcing the implicit arguments known from inside the section to be the ones declared by the command. -.. cmdv:: Local Arguments @qualid {* @possibly_bracketed_ident }. +.. cmdv:: Local Arguments @qualid {* [ @ident ] | @ident } When in a module, tell not to activate the - implicit arguments ofqualid declared by this command to contexts that + implicit arguments of :token:`qualid` declared by this command to contexts that require the module. -.. cmdv:: {? Global | Local } Arguments @qualid {*, {+ @possibly_bracketed_ident } }. +.. cmdv:: {? Global | Local } Arguments @qualid {*, {+ [ @ident ] | @ident } } For names of constants, inductive types, constructors, lemmas which can only be applied to a fixed number of @@ -1696,33 +1650,34 @@ Implicit arguments can be cleared with the following syntax: Check (fun l => map length l = map (list nat) nat length l). -Remark: To know which are the implicit arguments of an object, use the -command ``Print Implicit`` (see :ref:`displaying-implicit-args`). +.. note:: + To know which are the implicit arguments of an object, use the + command :cmd:`Print Implicit` (see :ref:`displaying-implicit-args`). Automatic declaration of implicit arguments ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -|Coq| can also automatically detect what are the implicit arguments of a -defined object. The command is just +.. cmd:: Arguments @qualid : default implicits -.. cmd:: Arguments @qualid : default implicits. + This command tells |Coq| to automatically detect what are the implicit arguments of a + defined object. -The auto-detection is governed by options telling if strict, -contextual, or reversible-pattern implicit arguments must be -considered or not (see :ref:`controlling-strict-implicit-args`, :ref:`controlling-strict-implicit-args`, -:ref:`controlling-rev-pattern-implicit-args`, and also :ref:`controlling-insertion-implicit-args`). + The auto-detection is governed by options telling if strict, + contextual, or reversible-pattern implicit arguments must be + considered or not (see :ref:`controlling-strict-implicit-args`, :ref:`controlling-strict-implicit-args`, + :ref:`controlling-rev-pattern-implicit-args`, and also :ref:`controlling-insertion-implicit-args`). -.. cmdv:: Global Arguments @qualid : default implicits + .. cmdv:: Global Arguments @qualid : default implicits - Tell to recompute the - implicit arguments of qualid after ending of the current section if - any. + Tell to recompute the + implicit arguments of qualid after ending of the current section if + any. -.. cmdv:: Local Arguments @qualid : default implicits + .. cmdv:: Local Arguments @qualid : default implicits - When in a module, tell not to activate the implicit arguments of `qualid` computed by this - declaration to contexts that requires the module. + When in a module, tell not to activate the implicit arguments of :token:`qualid` computed by this + declaration to contexts that requires the module. .. example:: @@ -1780,92 +1735,67 @@ appear strictly in the body of the type, they are implicit. Mode for automatic declaration of implicit arguments ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -In case one wants to systematically declare implicit the arguments -detectable as such, one may switch to the automatic declaration of -implicit arguments mode by using the command: - -.. cmd:: Set Implicit Arguments. +.. flag:: Implicit Arguments -Conversely, one may unset the mode by using ``Unset Implicit Arguments``. -The mode is off by default. Auto-detection of implicit arguments is -governed by options controlling whether strict and contextual implicit -arguments have to be considered or not. + This option (off by default) allows to systematically declare implicit + the arguments detectable as such. Auto-detection of implicit arguments is + governed by options controlling whether strict and contextual implicit + arguments have to be considered or not. .. _controlling-strict-implicit-args: Controlling strict implicit arguments ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -When the mode for automatic declaration of implicit arguments is on, -the default is to automatically set implicit only the strict implicit -arguments plus, for historical reasons, a small subset of the non-strict -implicit arguments. To relax this constraint and to set -implicit all non strict implicit arguments by default, use the command: - -.. cmd:: Unset Strict Implicit. +.. flag:: Strict Implicit -Conversely, use the command ``Set Strict Implicit`` to restore the -original mode that declares implicit only the strict implicit -arguments plus a small subset of the non strict implicit arguments. + When the mode for automatic declaration of implicit arguments is on, + the default is to automatically set implicit only the strict implicit + arguments plus, for historical reasons, a small subset of the non-strict + implicit arguments. To relax this constraint and to set + implicit all non strict implicit arguments by default, you can turn this + option off. -In the other way round, to capture exactly the strict implicit -arguments and no more than the strict implicit arguments, use the -command +.. flag:: Strongly Strict Implicit -.. cmd:: Set Strongly Strict Implicit. - -Conversely, use the command ``Unset Strongly Strict Implicit`` to let the -option “Strict Implicit” decide what to do. - -Remark: In versions of |Coq| prior to version 8.0, the default was to -declare the strict implicit arguments as implicit. + Use this option (off by default) to capture exactly the strict implicit + arguments and no more than the strict implicit arguments. .. _controlling-contextual-implicit-args: Controlling contextual implicit arguments ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -By default, |Coq| does not automatically set implicit the contextual -implicit arguments. To tell |Coq| to infer also contextual implicit -argument, use command - -.. cmd:: Set Contextual Implicit. +.. flag:: Contextual Implicit -Conversely, use command ``Unset Contextual Implicit`` to unset the -contextual implicit mode. + By default, |Coq| does not automatically set implicit the contextual + implicit arguments. You can turn this option on to tell |Coq| to also + infer contextual implicit argument. .. _controlling-rev-pattern-implicit-args: Controlling reversible-pattern implicit arguments ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -By default, |Coq| does not automatically set implicit the reversible-pattern -implicit arguments. To tell |Coq| to infer also reversible- -pattern implicit argument, use command +.. flag:: Reversible Pattern Implicit -.. cmd:: Set Reversible Pattern Implicit. - -Conversely, use command ``Unset Reversible Pattern Implicit`` to unset the -reversible-pattern implicit mode. + By default, |Coq| does not automatically set implicit the reversible-pattern + implicit arguments. You can turn this option on to tell |Coq| to also infer + reversible-pattern implicit argument. .. _controlling-insertion-implicit-args: Controlling the insertion of implicit arguments not followed by explicit arguments ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Implicit arguments can be declared to be automatically inserted when a -function is partially applied and the next argument of the function is -an implicit one. In case the implicit arguments are automatically -declared (with the command ``Set Implicit Arguments``), the command - -.. cmd:: Set Maximal Implicit Insertion. +.. flag:: Maximal Implicit Insertion -is used to tell to declare the implicit arguments with a maximal -insertion status. By default, automatically declared implicit -arguments are not declared to be insertable maximally. To restore the -default mode for maximal insertion, use the command + Assuming the implicit argument mode is on, this option (off by default) + declares implicit arguments to be automatically inserted when a + function is partially applied and the next argument of the function is + an implicit one. -.. cmd:: Unset Maximal Implicit Insertion. +.. _explicit-applications: Explicit applications ~~~~~~~~~~~~~~~~~~~~~ @@ -1902,9 +1832,9 @@ This syntax extension is given in the following grammar: Renaming implicit arguments ~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Implicit arguments names can be redefined using the following syntax: +.. cmd:: Arguments @qualid {* @name} : @rename -.. cmd:: Arguments @qualid {* @name} : @rename. + This command is used to redefine the names of implicit arguments. With the assert flag, ``Arguments`` can be used to assert that a given object has the expected number of arguments and that these arguments @@ -1912,51 +1842,44 @@ are named as expected. .. example:: (continued) -.. coqtop:: all + .. coqtop:: all - Arguments p [s t] _ [u] _: rename. + Arguments p [s t] _ [u] _: rename. - Check (p r1 (u:=c)). + Check (p r1 (u:=c)). - Check (p (s:=a) (t:=b) r1 (u:=c) r2). + Check (p (s:=a) (t:=b) r1 (u:=c) r2). - Fail Arguments p [s t] _ [w] _ : assert. + Fail Arguments p [s t] _ [w] _ : assert. .. _displaying-implicit-args: Displaying what the implicit arguments are ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -To display the implicit arguments associated to an object, and to know -if each of them is to be used maximally or not, use the command +.. cmd:: Print Implicit @qualid + + Use this command to display the implicit arguments associated to an object, + and to know if each of them is to be used maximally or not. -.. cmd:: Print Implicit @qualid. Explicit displaying of implicit arguments for pretty-printing ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -By default the basic pretty-printing rules hide the inferable implicit -arguments of an application. To force printing all implicit arguments, -use command - -.. cmd:: Set Printing Implicit. - -Conversely, to restore the hiding of implicit arguments, use command +.. flag:: Printing Implicit -.. cmd:: Unset Printing Implicit. + By default, the basic pretty-printing rules hide the inferable implicit + arguments of an application. Turn this option on to force printing all + implicit arguments. -By default the basic pretty-printing rules display the implicit -arguments that are not detected as strict implicit arguments. This -“defensive” mode can quickly make the display cumbersome so this can -be deactivated by using the command +.. flag:: Printing Implicit Defensive -.. cmd:: Unset Printing Implicit Defensive. + By default, the basic pretty-printing rules display the implicit + arguments that are not detected as strict implicit arguments. This + “defensive” mode can quickly make the display cumbersome so this can + be deactivated by turning this option off. -Conversely, to force the display of non strict arguments, use command - -.. cmd:: Set Printing Implicit Defensive. - -See also: ``Set Printing All`` in :ref:`printing_constructions_full`. +.. seealso:: :flag:`Printing All`. Interaction with subtyping ~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -1981,17 +1904,14 @@ but succeeds in Deactivation of implicit arguments for parsing ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Use of implicit arguments can be deactivated by issuing the command: - -.. cmd:: Set Parsing Explicit. +.. flag:: Parsing Explicit -In this case, all arguments of constants, inductive types, -constructors, etc, including the arguments declared as implicit, have -to be given as if none arguments were implicit. By symmetry, this also -affects printing. To restore parsing and normal printing of implicit -arguments, use: + Turning this option on (it is off by default) deactivates the use of implicit arguments. -.. cmd:: Unset Parsing Explicit. + In this case, all arguments of constants, inductive types, + constructors, etc, including the arguments declared as implicit, have + to be given as if no arguments were implicit. By symmetry, this also + affects printing. Canonical structures ~~~~~~~~~~~~~~~~~~~~ @@ -2002,90 +1922,91 @@ applied to an unknown structure instance (an implicit argument) and a value. The complete documentation of canonical structures can be found in :ref:`canonicalstructures`; here only a simple example is given. -Assume that `qualid` denotes an object ``(Build_struc`` |c_1| … |c_n| ``)`` in the -structure *struct* of which the fields are |x_1|, …, |x_n|. Assume that -`qualid` is declared as a canonical structure using the command +.. cmd:: Canonical Structure @qualid -.. cmd:: Canonical Structure @qualid. + This command declares :token:`qualid` as a canonical structure. -Then, each time an equation of the form ``(``\ |x_i| ``_)`` |eq_beta_delta_iota_zeta| |c_i| has to be -solved during the type-checking process, `qualid` is used as a solution. -Otherwise said, `qualid` is canonically used to extend the field |c_i| -into a complete structure built on |c_i|. + Assume that :token:`qualid` denotes an object ``(Build_struct`` |c_1| … |c_n| ``)`` in the + structure :g:`struct` of which the fields are |x_1|, …, |x_n|. + Then, each time an equation of the form ``(``\ |x_i| ``_)`` |eq_beta_delta_iota_zeta| |c_i| has to be + solved during the type checking process, :token:`qualid` is used as a solution. + Otherwise said, :token:`qualid` is canonically used to extend the field |c_i| + into a complete structure built on |c_i|. -Canonical structures are particularly useful when mixed with coercions -and strict implicit arguments. Here is an example. + Canonical structures are particularly useful when mixed with coercions + and strict implicit arguments. -.. coqtop:: all + .. example:: - Require Import Relations. + Here is an example. - Require Import EqNat. + .. coqtop:: all - Set Implicit Arguments. + Require Import Relations. - Unset Strict Implicit. + Require Import EqNat. - Structure Setoid : Type := {Carrier :> Set; Equal : relation Carrier; - Prf_equiv : equivalence Carrier Equal}. + Set Implicit Arguments. - Definition is_law (A B:Setoid) (f:A -> B) := forall x y:A, Equal x y -> Equal (f x) (f y). + Unset Strict Implicit. - Axiom eq_nat_equiv : equivalence nat eq_nat. + Structure Setoid : Type := {Carrier :> Set; Equal : relation Carrier; + Prf_equiv : equivalence Carrier Equal}. - Definition nat_setoid : Setoid := Build_Setoid eq_nat_equiv. + Definition is_law (A B:Setoid) (f:A -> B) := forall x y:A, Equal x y -> Equal (f x) (f y). - Canonical Structure nat_setoid. + Axiom eq_nat_equiv : equivalence nat eq_nat. -Thanks to ``nat_setoid`` declared as canonical, the implicit arguments ``A`` -and ``B`` can be synthesized in the next statement. + Definition nat_setoid : Setoid := Build_Setoid eq_nat_equiv. -.. coqtop:: all + Canonical Structure nat_setoid. - Lemma is_law_S : is_law S. + Thanks to :g:`nat_setoid` declared as canonical, the implicit arguments :g:`A` + and :g:`B` can be synthesized in the next statement. -Remark: If a same field occurs in several canonical structure, then -only the structure declared first as canonical is considered. + .. coqtop:: all -.. cmdv:: Canonical Structure @ident := @term : @type. + Lemma is_law_S : is_law S. -.. cmdv:: Canonical Structure @ident := @term. + .. note:: + If a same field occurs in several canonical structures, then + only the structure declared first as canonical is considered. -.. cmdv:: Canonical Structure @ident : @type := @term. + .. cmdv:: Canonical Structure @ident {? : @type } := @term -These are equivalent to a regular definition of `ident` followed by the declaration -``Canonical Structure`` `ident`. + This is equivalent to a regular definition of :token:`ident` followed by the + declaration :n:`Canonical Structure @ident`. -See also: more examples in user contribution category (Rocq/ALGEBRA). +.. cmd:: Print Canonical Projections -Print Canonical Projections. -++++++++++++++++++++++++++++ + This displays the list of global names that are components of some + canonical structure. For each of them, the canonical structure of + which it is a projection is indicated. -This displays the list of global names that are components of some -canonical structure. For each of them, the canonical structure of -which it is a projection is indicated. For instance, the above example -gives the following output: + .. example:: -.. coqtop:: all + For instance, the above example gives the following output: + + .. coqtop:: all - Print Canonical Projections. + Print Canonical Projections. Implicit types of variables ~~~~~~~~~~~~~~~~~~~~~~~~~~~ It is possible to bind variable names to a given type (e.g. in a -development using arithmetic, it may be convenient to bind the names `n` -or `m` to the type ``nat`` of natural numbers). The command for that is +development using arithmetic, it may be convenient to bind the names :g:`n` +or :g:`m` to the type :g:`nat` of natural numbers). -.. cmd:: Implicit Types {+ @ident } : @type. +.. cmd:: Implicit Types {+ @ident } : @type -The effect of the command is to automatically set the type of bound -variables starting with `ident` (either `ident` itself or `ident` followed by -one or more single quotes, underscore or digits) to be `type` (unless -the bound variable is already declared with an explicit type in which -case, this latter type is considered). + The effect of the command is to automatically set the type of bound + variables starting with :token:`ident` (either :token:`ident` itself or + :token:`ident` followed by one or more single quotes, underscore or + digits) to be :token:`type` (unless the bound variable is already declared + with an explicit type in which case, this latter type is considered). .. example:: @@ -2101,7 +2022,7 @@ case, this latter type is considered). Lemma cons_inj_bool : forall (m n:bool) l, n :: l = m :: l -> n = m. -.. cmdv:: Implicit Type @ident : @type. +.. cmdv:: Implicit Type @ident : @type This is useful for declaring the implicit type of a single variable. @@ -2140,7 +2061,7 @@ the ``Generalizable`` vernacular command to avoid unexpected generalizations when mistyping identifiers. There are several commands that specify which variables should be generalizable. -.. cmd:: Generalizable All Variables. +.. cmd:: Generalizable All Variables All variables are candidate for generalization if they appear free in the context under a @@ -2148,16 +2069,16 @@ that specify which variables should be generalizable. of typos. In such cases, the context will probably contain some unexpected generalized variable. -.. cmd:: Generalizable No Variables. +.. cmd:: Generalizable No Variables Disable implicit generalization entirely. This is the default behavior. -.. cmd:: Generalizable (Variable | Variables) {+ @ident }. +.. cmd:: Generalizable (Variable | Variables) {+ @ident } Allow generalization of the given identifiers only. Calling this command multiple times adds to the allowed identifiers. -.. cmd:: Global Generalizable. +.. cmd:: Global Generalizable Allows exporting the choice of generalizable variables. @@ -2177,6 +2098,7 @@ implicitly, as maximally-inserted arguments. In these binders, the binding name for the bound object is optional, whereas the type is mandatory, dually to regular binders. +.. _Coercions: Coercions --------- @@ -2191,12 +2113,7 @@ an inductive type or any constant with a type of the form Then the user is able to apply an object that is not a function, but can be coerced to a function, and more generally to consider that a term of type ``A`` is of type ``B`` provided that there is a declared coercion -between ``A`` and ``B``. The main command is - -.. cmd:: Coercion @qualid : @class >-> @class. - -which declares the construction denoted by qualid as a coercion -between the two given classes. +between ``A`` and ``B``. More details and examples, and a description of the commands related to coercions are provided in :ref:`implicitcoercions`. @@ -2206,56 +2123,58 @@ to coercions are provided in :ref:`implicitcoercions`. Printing constructions in full ------------------------------ -Coercions, implicit arguments, the type of pattern-matching, but also -notations (see :ref:`syntaxextensionsandinterpretationscopes`) can obfuscate the behavior of some -tactics (typically the tactics applying to occurrences of subterms are -sensitive to the implicit arguments). The command - -.. cmd:: Set Printing All. +.. flag:: Printing All -deactivates all high-level printing features such as coercions, -implicit arguments, returned type of pattern-matching, notations and -various syntactic sugar for pattern-matching or record projections. -Otherwise said, ``Set Printing All`` includes the effects of the commands -``Set Printing Implicit``, ``Set Printing Coercions``, ``Set Printing Synth``, -``Unset Printing Projections``, and ``Unset Printing Notations``. To reactivate -the high-level printing features, use the command + Coercions, implicit arguments, the type of pattern matching, but also + notations (see :ref:`syntaxextensionsandinterpretationscopes`) can obfuscate the behavior of some + tactics (typically the tactics applying to occurrences of subterms are + sensitive to the implicit arguments). Turning this option on + deactivates all high-level printing features such as coercions, + implicit arguments, returned type of pattern matching, notations and + various syntactic sugar for pattern matching or record projections. + Otherwise said, :flag:`Printing All` includes the effects of the options + :flag:`Printing Implicit`, :flag:`Printing Coercions`, :flag:`Printing Synth`, + :flag:`Printing Projections`, and :flag:`Printing Notations`. To reactivate + the high-level printing features, use the command ``Unset Printing All``. -.. cmd:: Unset Printing All. +.. _printing-universes: Printing universes ------------------ -The following command: +.. flag:: Printing Universes -.. cmd:: Set Printing Universes. + Turn this option on to activate the display of the actual level of each + occurrence of :g:`Type`. See :ref:`Sorts` for details. This wizard option, in + combination with :flag:`Printing All` can help to diagnose failures to unify + terms apparently identical but internally different in the Calculus of Inductive + Constructions. -activates the display of the actual level of each occurrence of ``Type``. -See :ref:`TODO-4.1.1-sorts` for details. This wizard option, in combination -with ``Set Printing All`` (see :ref:`printing_constructions_full`) can help to diagnose failures -to unify terms apparently identical but internally different in the -Calculus of Inductive Constructions. To reactivate the display of the -actual level of the occurrences of Type, use +.. cmd:: Print {? Sorted} Universes + :name: Print Universes -.. cmd:: Unset Printing Universes. + This command can be used to print the constraints on the internal level + of the occurrences of :math:`\Type` (see :ref:`Sorts`). -The constraints on the internal level of the occurrences of Type -(see :ref:`TODO-4.1.1-sorts`) can be printed using the command + If the optional ``Sorted`` option is given, each universe will be made + equivalent to a numbered label reflecting its level (with a linear + ordering) in the universe hierarchy. -.. cmd:: Print {? Sorted} Universes. + .. cmdv:: Print {? Sorted} Universes @string -If the optional ``Sorted`` option is given, each universe will be made -equivalent to a numbered label reflecting its level (with a linear -ordering) in the universe hierarchy. + This variant accepts an optional output filename. -This command also accepts an optional output filename: + If :token:`string` ends in ``.dot`` or ``.gv``, the constraints are printed in the DOT + language, and can be processed by Graphviz tools. The format is + unspecified if `string` doesn’t end in ``.dot`` or ``.gv``. -.. cmd:: Print {? Sorted} Universes @string. +.. cmdv:: Print Universes Subgraph(@names) -If `string` ends in ``.dot`` or ``.gv``, the constraints are printed in the DOT -language, and can be processed by Graphviz tools. The format is -unspecified if `string` doesn’t end in ``.dot`` or ``.gv``. + Prints the graph restricted to the requested names (adjusting + constraints to preserve the implied transitive constraints between + kept universes). +.. _existential-variables: Existential variables --------------------- @@ -2265,9 +2184,9 @@ subterms to eventually be replaced by actual subterms. Existential variables are generated in place of unsolvable implicit arguments or “_” placeholders when using commands such as ``Check`` (see -Section :ref:`TODO-6.3.1-check`) or when using tactics such as ``refine`` (see Section -:ref:`TODO-8.2.3-refine`), as well as in place of unsolvable instances when using -tactics such that ``eapply`` (see Section :ref:`TODO-8.2.4-apply`). An existential +Section :ref:`requests-to-the-environment`) or when using tactics such as +:tacn:`refine`, as well as in place of unsolvable instances when using +tactics such that :tacn:`eapply`. An existential variable is defined in a context, which is the context of variables of the placeholder which generated the existential variable, and a type, which is the expected type of the placeholder. @@ -2297,7 +2216,7 @@ form is appending to its name, indicating how the variables of its defining context are instantiated. The variables of the context of the existential variables which are -instantiated by themselves are not written, unless the flag ``Printing Existential Instances`` +instantiated by themselves are not written, unless the flag :flag:`Printing Existential Instances` is on (see Section :ref:`explicit-display-existentials`), and this is why an existential variable used in the same context as its context of definition is written with no instance. @@ -2310,27 +2229,22 @@ existential variable used in the same context as its context of definition is wr Check (fun x y => _) 0 1. Existential variables can be named by the user upon creation using -the syntax ``?``\ `ident`. This is useful when the existential +the syntax :n:`?[@ident]`. This is useful when the existential variable needs to be explicitly handled later in the script (e.g. -with a named-goal selector, see :ref:`TODO-9.2-goal-selectors`). +with a named-goal selector, see :ref:`goal-selectors`). .. _explicit-display-existentials: Explicit displaying of existential instances for pretty-printing ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -The command: - -.. cmd:: Set Printing Existential Instances. +.. flag:: Printing Existential Instances -activates the full display of how the context of an existential -variable is instantiated at each of the occurrences of the existential -variable. + This option (off by default) activates the full display of how the + context of an existential variable is instantiated at each of the + occurrences of the existential variable. -To deactivate the full display of the instances of existential -variables, use - -.. cmd:: Unset Printing Existential Instances. +.. _tactics-in-terms: Solving existential variables using tactics ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -2343,7 +2257,7 @@ is not specified and is implementation-dependent. The inner tactic may use any variable defined in its scope, including repeated alternations between variables introduced by term binding as well as those introduced by tactic binding. The expression `tacexpr` can be any tactic -expression as described in :ref:`thetacticlanguage`. +expression as described in :ref:`ltac`. .. coqtop:: all @@ -2352,7 +2266,3 @@ expression as described in :ref:`thetacticlanguage`. This construction is useful when one wants to define complicated terms using highly automated tactics without resorting to writing the proof-term by means of the interactive proof engine. - -This mechanism is comparable to the ``Declare Implicit Tactic`` command -defined at :ref:`TODO-8.9.7-implicit-automation`, except that the used -tactic is local to each hole instead of being declared globally. diff --git a/doc/sphinx/language/gallina-specification-language.rst b/doc/sphinx/language/gallina-specification-language.rst new file mode 100644 index 0000000000..1a33a9a46e --- /dev/null +++ b/doc/sphinx/language/gallina-specification-language.rst @@ -0,0 +1,1543 @@ +.. _gallinaspecificationlanguage: + +------------------------------------ + The Gallina specification language +------------------------------------ + +This chapter describes Gallina, the specification language of Coq. It allows +developing mathematical theories and to prove specifications of programs. The +theories are built from axioms, hypotheses, parameters, lemmas, theorems and +definitions of constants, functions, predicates and sets. The syntax of logical +objects involved in theories is described in Section :ref:`term`. The +language of commands, called *The Vernacular* is described in Section +:ref:`vernacular`. + +In Coq, logical objects are typed to ensure their logical correctness. The +rules implemented by the typing algorithm are described in Chapter :ref:`calculusofinductiveconstructions`. + + +About the grammars in the manual +================================ + +Grammars are presented in Backus-Naur form (BNF). Terminal symbols are +set in black ``typewriter font``. In addition, there are special notations for +regular expressions. + +An expression enclosed in square brackets ``[…]`` means at most one +occurrence of this expression (this corresponds to an optional +component). + +The notation “``entry sep … sep entry``” stands for a non empty sequence +of expressions parsed by entry and separated by the literal “``sep``” [1]_. + +Similarly, the notation “``entry … entry``” stands for a non empty +sequence of expressions parsed by the “``entry``” entry, without any +separator between. + +At the end, the notation “``[entry sep … sep entry]``” stands for a +possibly empty sequence of expressions parsed by the “``entry``” entry, +separated by the literal “``sep``”. + +.. _lexical-conventions: + +Lexical conventions +=================== + +Blanks + Space, newline and horizontal tabulation are considered as blanks. + Blanks are ignored but they separate tokens. + +Comments + Comments in Coq are enclosed between ``(*`` and ``*)``, and can be nested. + They can contain any character. However, :token:`string` literals must be + correctly closed. Comments are treated as blanks. + +Identifiers and access identifiers + Identifiers, written :token:`ident`, are sequences of letters, digits, ``_`` and + ``'``, that do not start with a digit or ``'``. That is, they are + recognized by the following lexical class: + + .. productionlist:: coq + first_letter : a..z ∣ A..Z ∣ _ ∣ unicode-letter + subsequent_letter : a..z ∣ A..Z ∣ 0..9 ∣ _ ∣ ' ∣ unicode-letter ∣ unicode-id-part + ident : `first_letter`[`subsequent_letter`…`subsequent_letter`] + access_ident : .`ident` + + All characters are meaningful. In particular, identifiers are case-sensitive. + The entry ``unicode-letter`` non-exhaustively includes Latin, + Greek, Gothic, Cyrillic, Arabic, Hebrew, Georgian, Hangul, Hiragana + and Katakana characters, CJK ideographs, mathematical letter-like + symbols, hyphens, non-breaking space, … The entry ``unicode-id-part`` + non-exhaustively includes symbols for prime letters and subscripts. + + Access identifiers, written :token:`access_ident`, are identifiers prefixed by + `.` (dot) without blank. They are used in the syntax of qualified + identifiers. + +Natural numbers and integers + Numerals are sequences of digits. Integers are numerals optionally + preceded by a minus sign. + + .. productionlist:: coq + digit : 0..9 + num : `digit`…`digit` + integer : [-]`num` + +Strings + Strings are delimited by ``"`` (double quote), and enclose a sequence of + any characters different from ``"`` or the sequence ``""`` to denote the + double quote character. In grammars, the entry for quoted strings is + :production:`string`. + +Keywords + The following identifiers are reserved keywords, and cannot be + employed otherwise:: + + _ as at cofix else end exists exists2 fix for + forall fun if IF in let match mod Prop return + Set then Type using where with + +Special tokens + The following sequences of characters are special tokens:: + + ! % & && ( () ) * + ++ , - -> . .( .. + / /\ : :: :< := :> ; < <- <-> <: <= <> = + => =_D > >-> >= ? ?= @ [ \/ ] ^ { | |- + || } ~ #[ + + Lexical ambiguities are resolved according to the “longest match” + rule: when a sequence of non alphanumerical characters can be + decomposed into several different ways, then the first token is the + longest possible one (among all tokens defined at this moment), and so + on. + +.. _term: + +Terms +===== + +Syntax of terms +--------------- + +The following grammars describe the basic syntax of the terms of the +*Calculus of Inductive Constructions* (also called Cic). The formal +presentation of Cic is given in Chapter :ref:`calculusofinductiveconstructions`. Extensions of this syntax +are given in Chapter :ref:`extensionsofgallina`. How to customize the syntax +is described in Chapter :ref:`syntaxextensionsandinterpretationscopes`. + +.. productionlist:: coq + term : forall `binders` , `term` + : | fun `binders` => `term` + : | fix `fix_bodies` + : | cofix `cofix_bodies` + : | let `ident` [`binders`] [: `term`] := `term` in `term` + : | let fix `fix_body` in `term` + : | let cofix `cofix_body` in `term` + : | let ( [`name` , … , `name`] ) [`dep_ret_type`] := `term` in `term` + : | let ' `pattern` [in `term`] := `term` [`return_type`] in `term` + : | if `term` [`dep_ret_type`] then `term` else `term` + : | `term` : `term` + : | `term` <: `term` + : | `term` :> + : | `term` -> `term` + : | `term` `arg` … `arg` + : | @ `qualid` [`term` … `term`] + : | `term` % `ident` + : | match `match_item` , … , `match_item` [`return_type`] with + : [[|] `equation` | … | `equation`] end + : | `qualid` + : | `sort` + : | `num` + : | _ + : | ( `term` ) + arg : `term` + : | ( `ident` := `term` ) + binders : `binder` … `binder` + binder : `name` + : | ( `name` … `name` : `term` ) + : | ( `name` [: `term`] := `term` ) + : | ' `pattern` + name : `ident` | _ + qualid : `ident` | `qualid` `access_ident` + sort : Prop | Set | Type + fix_bodies : `fix_body` + : | `fix_body` with `fix_body` with … with `fix_body` for `ident` + cofix_bodies : `cofix_body` + : | `cofix_body` with `cofix_body` with … with `cofix_body` for `ident` + fix_body : `ident` `binders` [`annotation`] [: `term`] := `term` + cofix_body : `ident` [`binders`] [: `term`] := `term` + annotation : { struct `ident` } + match_item : `term` [as `name`] [in `qualid` [`pattern` … `pattern`]] + dep_ret_type : [as `name`] `return_type` + return_type : return `term` + equation : `mult_pattern` | … | `mult_pattern` => `term` + mult_pattern : `pattern` , … , `pattern` + pattern : `qualid` `pattern` … `pattern` + : | @ `qualid` `pattern` … `pattern` + : | `pattern` as `ident` + : | `pattern` % `ident` + : | `qualid` + : | _ + : | `num` + : | ( `or_pattern` , … , `or_pattern` ) + or_pattern : `pattern` | … | `pattern` + + +Types +----- + +Coq terms are typed. Coq types are recognized by the same syntactic +class as :token:`term`. We denote by :production:`type` the semantic subclass +of types inside the syntactic class :token:`term`. + +.. _gallina-identifiers: + +Qualified identifiers and simple identifiers +-------------------------------------------- + +*Qualified identifiers* (:token:`qualid`) denote *global constants* +(definitions, lemmas, theorems, remarks or facts), *global variables* +(parameters or axioms), *inductive types* or *constructors of inductive +types*. *Simple identifiers* (or shortly :token:`ident`) are a syntactic subset +of qualified identifiers. Identifiers may also denote *local variables*, +while qualified identifiers do not. + +Numerals +-------- + +Numerals have no definite semantics in the calculus. They are mere +notations that can be bound to objects through the notation mechanism +(see Chapter :ref:`syntaxextensionsandinterpretationscopes` for details). +Initially, numerals are bound to Peano’s representation of natural +numbers (see :ref:`datatypes`). + +.. note:: + + Negative integers are not at the same level as :token:`num`, for this + would make precedence unnatural. + +.. index:: + single: Set (sort) + single: Prop + single: Type + +Sorts +----- + +There are three sorts :g:`Set`, :g:`Prop` and :g:`Type`. + +- :g:`Prop` is the universe of *logical propositions*. The logical propositions + themselves are typing the proofs. We denote propositions by :production:`form`. + This constitutes a semantic subclass of the syntactic class :token:`term`. + +- :g:`Set` is is the universe of *program types* or *specifications*. The + specifications themselves are typing the programs. We denote + specifications by :production:`specif`. This constitutes a semantic subclass of + the syntactic class :token:`term`. + +- :g:`Type` is the type of :g:`Prop` and :g:`Set` + +More on sorts can be found in Section :ref:`sorts`. + +.. _binders: + +Binders +------- + +Various constructions such as :g:`fun`, :g:`forall`, :g:`fix` and :g:`cofix` +*bind* variables. A binding is represented by an identifier. If the binding +variable is not used in the expression, the identifier can be replaced by the +symbol :g:`_`. When the type of a bound variable cannot be synthesized by the +system, it can be specified with the notation :n:`(@ident : @type)`. There is also +a notation for a sequence of binding variables sharing the same type: +:n:`({+ @ident} : @type)`. A +binder can also be any pattern prefixed by a quote, e.g. :g:`'(x,y)`. + +Some constructions allow the binding of a variable to value. This is +called a “let-binder”. The entry :token:`binder` of the grammar accepts +either an assumption binder as defined above or a let-binder. The notation in +the latter case is :n:`(@ident := @term)`. In a let-binder, only one +variable can be introduced at the same time. It is also possible to give +the type of the variable as follows: +:n:`(@ident : @type := @term)`. + +Lists of :token:`binder` are allowed. In the case of :g:`fun` and :g:`forall`, +it is intended that at least one binder of the list is an assumption otherwise +fun and forall gets identical. Moreover, parentheses can be omitted in +the case of a single sequence of bindings sharing the same type (e.g.: +:g:`fun (x y z : A) => t` can be shortened in :g:`fun x y z : A => t`). + +.. index:: fun ... => ... + +Abstractions +------------ + +The expression :n:`fun @ident : @type => @term` defines the +*abstraction* of the variable :token:`ident`, of type :token:`type`, over the term +:token:`term`. It denotes a function of the variable :token:`ident` that evaluates to +the expression :token:`term` (e.g. :g:`fun x : A => x` denotes the identity +function on type :g:`A`). The keyword :g:`fun` can be followed by several +binders as given in Section :ref:`binders`. Functions over +several variables are equivalent to an iteration of one-variable +functions. For instance the expression +“fun :token:`ident`\ :math:`_{1}` … :token:`ident`\ :math:`_{n}` +: :token:`type` => :token:`term`” +denotes the same function as “ fun :token:`ident`\ +:math:`_{1}` : :token:`type` => … +fun :token:`ident`\ :math:`_{n}` : :token:`type` => :token:`term`”. If +a let-binder occurs in +the list of binders, it is expanded to a let-in definition (see +Section :ref:`let-in`). + +.. index:: forall + +Products +-------- + +The expression :n:`forall @ident : @type, @term` denotes the +*product* of the variable :token:`ident` of type :token:`type`, over the term :token:`term`. +As for abstractions, :g:`forall` is followed by a binder list, and products +over several variables are equivalent to an iteration of one-variable +products. Note that :token:`term` is intended to be a type. + +If the variable :token:`ident` occurs in :token:`term`, the product is called +*dependent product*. The intention behind a dependent product +:g:`forall x : A, B` is twofold. It denotes either +the universal quantification of the variable :g:`x` of type :g:`A` +in the proposition :g:`B` or the functional dependent product from +:g:`A` to :g:`B` (a construction usually written +:math:`\Pi_{x:A}.B` in set theory). + +Non dependent product types have a special notation: :g:`A -> B` stands for +:g:`forall _ : A, B`. The *non dependent product* is used both to denote +the propositional implication and function types. + +Applications +------------ + +The expression :token:`term`\ :math:`_0` :token:`term`\ :math:`_1` denotes the +application of :token:`term`\ :math:`_0` to :token:`term`\ :math:`_1`. + +The expression :token:`term`\ :math:`_0` :token:`term`\ :math:`_1` ... +:token:`term`\ :math:`_n` denotes the application of the term +:token:`term`\ :math:`_0` to the arguments :token:`term`\ :math:`_1` ... then +:token:`term`\ :math:`_n`. It is equivalent to ( … ( :token:`term`\ :math:`_0` +:token:`term`\ :math:`_1` ) … ) :token:`term`\ :math:`_n` : associativity is to the +left. + +The notation :n:`(@ident := @term)` for arguments is used for making +explicit the value of implicit arguments (see +Section :ref:`explicit-applications`). + +.. index:: + single: ... : ... (type cast) + single: ... <: ... + single: ... <<: ... + +Type cast +--------- + +The expression :n:`@term : @type` is a type cast expression. It enforces +the type of :token:`term` to be :token:`type`. + +:n:`@term <: @type` locally sets up the virtual machine for checking that +:token:`term` has type :token:`type`. + +:n:`@term <<: @type` uses native compilation for checking that :token:`term` +has type :token:`type`. + +.. index:: _ + +Inferable subterms +------------------ + +Expressions often contain redundant pieces of information. Subterms that can be +automatically inferred by Coq can be replaced by the symbol ``_`` and Coq will +guess the missing piece of information. + +.. index:: let ... := ... (term) + +.. _let-in: + +Let-in definitions +------------------ + +:n:`let @ident := @term in @term’` +denotes the local binding of :token:`term` to the variable +:token:`ident` in :token:`term`’. There is a syntactic sugar for let-in +definition of functions: :n:`let @ident {+ @binder} := @term in @term’` +stands for :n:`let @ident := fun {+ @binder} => @term in @term’`. + +.. index:: match ... with ... + +Definition by case analysis +--------------------------- + +Objects of inductive types can be destructurated by a case-analysis +construction called *pattern matching* expression. A pattern matching +expression is used to analyze the structure of an inductive object and +to apply specific treatments accordingly. + +This paragraph describes the basic form of pattern matching. See +Section :ref:`Mult-match` and Chapter :ref:`extendedpatternmatching` for the description +of the general form. The basic form of pattern matching is characterized +by a single :token:`match_item` expression, a :token:`mult_pattern` restricted to a +single :token:`pattern` and :token:`pattern` restricted to the form +:n:`@qualid {* @ident}`. + +The expression match ":token:`term`:math:`_0` :token:`return_type` with +:token:`pattern`:math:`_1` => :token:`term`:math:`_1` :math:`|` … :math:`|` +:token:`pattern`:math:`_n` => :token:`term`:math:`_n` end" denotes a +*pattern matching* over the term :token:`term`:math:`_0` (expected to be +of an inductive type :math:`I`). The terms :token:`term`:math:`_1`\ …\ +:token:`term`:math:`_n` are the *branches* of the pattern matching +expression. Each of :token:`pattern`:math:`_i` has a form :token:`qualid` +:token:`ident` where :token:`qualid` must denote a constructor. There should be +exactly one branch for every constructor of :math:`I`. + +The :token:`return_type` expresses the type returned by the whole match +expression. There are several cases. In the *non dependent* case, all +branches have the same type, and the :token:`return_type` is the common type of +branches. In this case, :token:`return_type` can usually be omitted as it can be +inferred from the type of the branches [2]_. + +In the *dependent* case, there are three subcases. In the first subcase, +the type in each branch may depend on the exact value being matched in +the branch. In this case, the whole pattern matching itself depends on +the term being matched. This dependency of the term being matched in the +return type is expressed with an “as :token:`ident`” clause where :token:`ident` +is dependent in the return type. For instance, in the following example: + +.. coqtop:: in + + Inductive bool : Type := true : bool | false : bool. + Inductive eq (A:Type) (x:A) : A -> Prop := eq_refl : eq A x x. + Inductive or (A:Prop) (B:Prop) : Prop := + | or_introl : A -> or A B + | or_intror : B -> or A B. + + Definition bool_case (b:bool) : or (eq bool b true) (eq bool b false) := + match b as x return or (eq bool x true) (eq bool x false) with + | true => or_introl (eq bool true true) (eq bool true false) (eq_refl bool true) + | false => or_intror (eq bool false true) (eq bool false false) (eq_refl bool false) + end. + +the branches have respective types ":g:`or (eq bool true true) (eq bool true false)`" +and ":g:`or (eq bool false true) (eq bool false false)`" while the whole +pattern matching expression has type ":g:`or (eq bool b true) (eq bool b false)`", +the identifier :g:`b` being used to represent the dependency. + +.. note:: + + When the term being matched is a variable, the ``as`` clause can be + omitted and the term being matched can serve itself as binding name in + the return type. For instance, the following alternative definition is + accepted and has the same meaning as the previous one. + + .. coqtop:: in + + Definition bool_case (b:bool) : or (eq bool b true) (eq bool b false) := + match b return or (eq bool b true) (eq bool b false) with + | true => or_introl (eq bool true true) (eq bool true false) (eq_refl bool true) + | false => or_intror (eq bool false true) (eq bool false false) (eq_refl bool false) + end. + +The second subcase is only relevant for annotated inductive types such +as the equality predicate (see Section :ref:`coq-equality`), +the order predicate on natural numbers or the type of lists of a given +length (see Section :ref:`matching-dependent`). In this configuration, the +type of each branch can depend on the type dependencies specific to the +branch and the whole pattern matching expression has a type determined +by the specific dependencies in the type of the term being matched. This +dependency of the return type in the annotations of the inductive type +is expressed using a “:g:`in` :math:`I` :g:`_ … _` :token:`pattern`:math:`_1` … +:token:`pattern`:math:`_n`” clause, where + +- :math:`I` is the inductive type of the term being matched; + +- the :g:`_` are matching the parameters of the inductive type: the + return type is not dependent on them. + +- the :token:`pattern`:math:`_i` are matching the annotations of the + inductive type: the return type is dependent on them + +- in the basic case which we describe below, each :token:`pattern`:math:`_i` + is a name :token:`ident`:math:`_i`; see :ref:`match-in-patterns` for the + general case + +For instance, in the following example: + +.. coqtop:: in + + Definition eq_sym (A:Type) (x y:A) (H:eq A x y) : eq A y x := + match H in eq _ _ z return eq A z x with + | eq_refl _ => eq_refl A x + end. + +the type of the branch is :g:`eq A x x` because the third argument of +:g:`eq` is :g:`x` in the type of the pattern :g:`eq_refl`. On the contrary, the +type of the whole pattern matching expression has type :g:`eq A y x` because the +third argument of eq is y in the type of H. This dependency of the case analysis +in the third argument of :g:`eq` is expressed by the identifier :g:`z` in the +return type. + +Finally, the third subcase is a combination of the first and second +subcase. In particular, it only applies to pattern matching on terms in +a type with annotations. For this third subcase, both the clauses ``as`` and +``in`` are available. + +There are specific notations for case analysis on types with one or two +constructors: ``if … then … else …`` and ``let (…,…) := … in …`` (see +Sections :ref:`if-then-else` and :ref:`irrefutable-patterns`). + +.. index:: + single: fix + single: cofix + +Recursive functions +------------------- + +The expression “``fix`` :token:`ident`:math:`_1` :token:`binder`:math:`_1` ``:`` +:token:`type`:math:`_1` ``:=`` :token:`term`:math:`_1` ``with … with`` +:token:`ident`:math:`_n` :token:`binder`:math:`_n` : :token:`type`:math:`_n` +``:=`` :token:`term`:math:`_n` ``for`` :token:`ident`:math:`_i`” denotes the +:math:`i`-th component of a block of functions defined by mutual structural +recursion. It is the local counterpart of the :cmd:`Fixpoint` command. When +:math:`n=1`, the “``for`` :token:`ident`:math:`_i`” clause is omitted. + +The expression “``cofix`` :token:`ident`:math:`_1` :token:`binder`:math:`_1` ``:`` +:token:`type`:math:`_1` ``with … with`` :token:`ident`:math:`_n` :token:`binder`:math:`_n` +: :token:`type`:math:`_n` ``for`` :token:`ident`:math:`_i`” denotes the +:math:`i`-th component of a block of terms defined by a mutual guarded +co-recursion. It is the local counterpart of the :cmd:`CoFixpoint` command. When +:math:`n=1`, the “``for`` :token:`ident`:math:`_i`” clause is omitted. + +The association of a single fixpoint and a local definition have a special +syntax: :n:`let fix @ident @binders := @term in` stands for +:n:`let @ident := fix @ident @binders := @term in`. The same applies for co-fixpoints. + +.. _vernacular: + +The Vernacular +============== + +.. productionlist:: coq + decorated-sentence : [ `decoration` … `decoration` ] `sentence` + sentence : `assumption` + : | `definition` + : | `inductive` + : | `fixpoint` + : | `assertion` `proof` + assumption : `assumption_keyword` `assums`. + assumption_keyword : Axiom | Conjecture + : | Parameter | Parameters + : | Variable | Variables + : | Hypothesis | Hypotheses + assums : `ident` … `ident` : `term` + : | ( `ident` … `ident` : `term` ) … ( `ident` … `ident` : `term` ) + definition : [Local] Definition `ident` [`binders`] [: `term`] := `term` . + : | Let `ident` [`binders`] [: `term`] := `term` . + inductive : Inductive `ind_body` with … with `ind_body` . + : | CoInductive `ind_body` with … with `ind_body` . + ind_body : `ident` [`binders`] : `term` := + : [[|] `ident` [`binders`] [:`term`] | … | `ident` [`binders`] [:`term`]] + fixpoint : Fixpoint `fix_body` with … with `fix_body` . + : | CoFixpoint `cofix_body` with … with `cofix_body` . + assertion : `assertion_keyword` `ident` [`binders`] : `term` . + assertion_keyword : Theorem | Lemma + : | Remark | Fact + : | Corollary | Proposition + : | Definition | Example + proof : Proof . … Qed . + : | Proof . … Defined . + : | Proof . … Admitted . + decoration : #[ `attributes` ] + attributes : [`attribute`, … , `attribute`] + attribute : `ident` + :| `ident` = `string` + :| `ident` ( `attributes` ) + +.. todo:: This use of … in this grammar is inconsistent + What about removing the proof part of this grammar from this chapter + and putting it somewhere where top-level tactics can be described as well? + See also #7583. + +This grammar describes *The Vernacular* which is the language of +commands of Gallina. A sentence of the vernacular language, like in +many natural languages, begins with a capital letter and ends with a +dot. + +Sentences may be *decorated* with so-called *attributes*, +which are described in the corresponding section (:ref:`gallina-attributes`). + +The different kinds of command are described hereafter. They all suppose +that the terms occurring in the sentences are well-typed. + +.. _gallina-assumptions: + +Assumptions +----------- + +Assumptions extend the environment with axioms, parameters, hypotheses +or variables. An assumption binds an :token:`ident` to a :token:`type`. It is accepted +by Coq if and only if this :token:`type` is a correct type in the environment +preexisting the declaration and if :token:`ident` was not previously defined in +the same module. This :token:`type` is considered to be the type (or +specification, or statement) assumed by :token:`ident` and we say that :token:`ident` +has type :token:`type`. + +.. _Axiom: + +.. cmd:: Parameter @ident : @type + + This command links :token:`type` to the name :token:`ident` as its specification in + the global context. The fact asserted by :token:`type` is thus assumed as a + postulate. + + .. exn:: @ident already exists. + :name: @ident already exists. (Axiom) + :undocumented: + + .. cmdv:: Parameter {+ @ident } : @type + + Adds several parameters with specification :token:`type`. + + .. cmdv:: Parameter {+ ( {+ @ident } : @type ) } + + Adds blocks of parameters with different specifications. + + .. cmdv:: Local Parameter {+ ( {+ @ident } : @type ) } + :name: Local Parameter + + Such parameters are never made accessible through their unqualified name by + :cmd:`Import` and its variants. You have to explicitly give their fully + qualified name to refer to them. + + .. cmdv:: {? Local } Parameters {+ ( {+ @ident } : @type ) } + {? Local } Axiom {+ ( {+ @ident } : @type ) } + {? Local } Axioms {+ ( {+ @ident } : @type ) } + {? Local } Conjecture {+ ( {+ @ident } : @type ) } + {? Local } Conjectures {+ ( {+ @ident } : @type ) } + :name: Parameters; Axiom; Axioms; Conjecture; Conjectures + + These variants are synonyms of :n:`{? Local } Parameter {+ ( {+ @ident } : @type ) }`. + +.. cmd:: Variable @ident : @type + + This command links :token:`type` to the name :token:`ident` in the context of + the current section (see Section :ref:`section-mechanism` for a description of + the section mechanism). When the current section is closed, name :token:`ident` + will be unknown and every object using this variable will be explicitly + parametrized (the variable is *discharged*). Using the :cmd:`Variable` command out + of any section is equivalent to using :cmd:`Local Parameter`. + + .. exn:: @ident already exists. + :name: @ident already exists. (Variable) + :undocumented: + + .. cmdv:: Variable {+ @ident } : @term + + Links :token:`type` to each :token:`ident`. + + .. cmdv:: Variable {+ ( {+ @ident } : @term ) } + + Adds blocks of variables with different specifications. + + .. cmdv:: Variables {+ ( {+ @ident } : @term) } + Hypothesis {+ ( {+ @ident } : @term) } + Hypotheses {+ ( {+ @ident } : @term) } + :name: Variables; Hypothesis; Hypotheses + + These variants are synonyms of :n:`Variable {+ ( {+ @ident } : @term) }`. + +.. note:: + It is advised to use the commands :cmd:`Axiom`, :cmd:`Conjecture` and + :cmd:`Hypothesis` (and their plural forms) for logical postulates (i.e. when + the assertion :token:`type` is of sort :g:`Prop`), and to use the commands + :cmd:`Parameter` and :cmd:`Variable` (and their plural forms) in other cases + (corresponding to the declaration of an abstract mathematical entity). + +.. _gallina-definitions: + +Definitions +----------- + +Definitions extend the environment with associations of names to terms. +A definition can be seen as a way to give a meaning to a name or as a +way to abbreviate a term. In any case, the name can later be replaced at +any time by its definition. + +The operation of unfolding a name into its definition is called +:math:`\delta`-conversion (see Section :ref:`delta-reduction`). A +definition is accepted by the system if and only if the defined term is +well-typed in the current context of the definition and if the name is +not already used. The name defined by the definition is called a +*constant* and the term it refers to is its *body*. A definition has a +type which is the type of its body. + +A formal presentation of constants and environments is given in +Section :ref:`typing-rules`. + +.. cmd:: Definition @ident := @term + + This command binds :token:`term` to the name :token:`ident` in the environment, + provided that :token:`term` is well-typed. + + .. exn:: @ident already exists. + :name: @ident already exists. (Definition) + :undocumented: + + .. cmdv:: Definition @ident : @type := @term + + This variant checks that the type of :token:`term` is definitionally equal to + :token:`type`, and registers :token:`ident` as being of type + :token:`type`, and bound to value :token:`term`. + + .. exn:: The term @term has type @type while it is expected to have type @type'. + :undocumented: + + .. cmdv:: Definition @ident @binders {? : @term } := @term + + This is equivalent to + :n:`Definition @ident : forall @binders, @term := fun @binders => @term`. + + .. cmdv:: Local Definition @ident {? @binders } {? : @type } := @term + :name: Local Definition + + Such definitions are never made accessible through their + unqualified name by :cmd:`Import` and its variants. + You have to explicitly give their fully qualified name to refer to them. + + .. cmdv:: {? Local } Example @ident {? @binders } {? : @type } := @term + :name: Example + + This is equivalent to :cmd:`Definition`. + +.. seealso:: :cmd:`Opaque`, :cmd:`Transparent`, :tacn:`unfold`. + +.. cmd:: Let @ident := @term + + This command binds the value :token:`term` to the name :token:`ident` in the + environment of the current section. The name :token:`ident` disappears when the + current section is eventually closed, and all persistent objects (such + as theorems) defined within the section and depending on :token:`ident` are + prefixed by the let-in definition :n:`let @ident := @term in`. + Using the :cmd:`Let` command out of any section is equivalent to using + :cmd:`Local Definition`. + + .. exn:: @ident already exists. + :name: @ident already exists. (Let) + :undocumented: + + .. cmdv:: Let @ident {? @binders } {? : @type } := @term + :undocumented: + + .. cmdv:: Let Fixpoint @ident @fix_body {* with @fix_body} + :name: Let Fixpoint + :undocumented: + + .. cmdv:: Let CoFixpoint @ident @cofix_body {* with @cofix_body} + :name: Let CoFixpoint + :undocumented: + +.. seealso:: Section :ref:`section-mechanism`, commands :cmd:`Opaque`, + :cmd:`Transparent`, and tactic :tacn:`unfold`. + +.. _gallina-inductive-definitions: + +Inductive definitions +--------------------- + +We gradually explain simple inductive types, simple annotated inductive +types, simple parametric inductive types, mutually inductive types. We +explain also co-inductive types. + +Simple inductive types +~~~~~~~~~~~~~~~~~~~~~~ + +.. cmd:: Inductive @ident : {? @sort } := {? | } @ident : @type {* | @ident : @type } + + This command defines a simple inductive type and its constructors. + The first :token:`ident` is the name of the inductively defined type + and :token:`sort` is the universe where it lives. The next :token:`ident`\s + are the names of its constructors and :token:`type` their respective types. + Depending on the universe where the inductive type :token:`ident` lives + (e.g. its type :token:`sort`), Coq provides a number of destructors. + Destructors are named :token:`ident`\ ``_ind``, :token:`ident`\ ``_rec`` + or :token:`ident`\ ``_rect`` which respectively correspond to elimination + principles on :g:`Prop`, :g:`Set` and :g:`Type`. + The type of the destructors expresses structural induction/recursion + principles over objects of type :token:`ident`. + The constant :token:`ident`\ ``_ind`` is always provided, + whereas :token:`ident`\ ``_rec`` and :token:`ident`\ ``_rect`` can be + impossible to derive (for example, when :token:`ident` is a proposition). + + .. exn:: Non strictly positive occurrence of @ident in @type. + + The types of the constructors have to satisfy a *positivity condition* + (see Section :ref:`positivity`). This condition ensures the soundness of + the inductive definition. + + .. exn:: The conclusion of @type is not valid; it must be built from @ident. + + The conclusion of the type of the constructors must be the inductive type + :token:`ident` being defined (or :token:`ident` applied to arguments in + the case of annotated inductive types — cf. next section). + + .. example:: + + The set of natural numbers is defined as: + + .. coqtop:: all + + Inductive nat : Set := + | O : nat + | S : nat -> nat. + + The type nat is defined as the least :g:`Set` containing :g:`O` and closed by + the :g:`S` constructor. The names :g:`nat`, :g:`O` and :g:`S` are added to the + environment. + + Now let us have a look at the elimination principles. They are three of them: + :g:`nat_ind`, :g:`nat_rec` and :g:`nat_rect`. The type of :g:`nat_ind` is: + + .. coqtop:: all + + Check nat_ind. + + This is the well known structural induction principle over natural + numbers, i.e. the second-order form of Peano’s induction principle. It + allows proving some universal property of natural numbers (:g:`forall + n:nat, P n`) by induction on :g:`n`. + + The types of :g:`nat_rec` and :g:`nat_rect` are similar, except that they pertain + to :g:`(P:nat->Set)` and :g:`(P:nat->Type)` respectively. They correspond to + primitive induction principles (allowing dependent types) respectively + over sorts ``Set`` and ``Type``. + + .. cmdv:: Inductive @ident {? : @sort } := {? | } {*| @ident {? @binders } {? : @type } } + + Constructors :token:`ident`\s can come with :token:`binders` in which case, + the actual type of the constructor is :n:`forall @binders, @type`. + + In the case where inductive types have no annotations (next section + gives an example of such annotations), a constructor can be defined + by only giving the type of its arguments. + + .. example:: + + .. coqtop:: in + + Inductive nat : Set := O | S (_:nat). + + +Simple annotated inductive types +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In an annotated inductive types, the universe where the inductive type +is defined is no longer a simple sort, but what is called an arity, +which is a type whose conclusion is a sort. + +.. example:: + + As an example of annotated inductive types, let us define the + :g:`even` predicate: + + .. coqtop:: all + + Inductive even : nat -> Prop := + | even_0 : even O + | even_SS : forall n:nat, even n -> even (S (S n)). + + The type :g:`nat->Prop` means that even is a unary predicate (inductively + defined) over natural numbers. The type of its two constructors are the + defining clauses of the predicate even. The type of :g:`even_ind` is: + + .. coqtop:: all + + Check even_ind. + + From a mathematical point of view it asserts that the natural numbers satisfying + the predicate even are exactly in the smallest set of naturals satisfying the + clauses :g:`even_0` or :g:`even_SS`. This is why, when we want to prove any + predicate :g:`P` over elements of :g:`even`, it is enough to prove it for :g:`O` + and to prove that if any natural number :g:`n` satisfies :g:`P` its double + successor :g:`(S (S n))` satisfies also :g:`P`. This is indeed analogous to the + structural induction principle we got for :g:`nat`. + +Parametrized inductive types +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. cmdv:: Inductive @ident @binders {? : @type } := {? | } @ident : @type {* | @ident : @type} + + In the previous example, each constructor introduces a different + instance of the predicate :g:`even`. In some cases, all the constructors + introduce the same generic instance of the inductive definition, in + which case, instead of an annotation, we use a context of parameters + which are :token:`binders` shared by all the constructors of the definition. + + Parameters differ from inductive type annotations in the fact that the + conclusion of each type of constructor invoke the inductive type with + the same values of parameters as its specification. + + .. example:: + + A typical example is the definition of polymorphic lists: + + .. coqtop:: in + + Inductive list (A:Set) : Set := + | nil : list A + | cons : A -> list A -> list A. + + In the type of :g:`nil` and :g:`cons`, we write :g:`(list A)` and not + just :g:`list`. The constructors :g:`nil` and :g:`cons` will have respectively + types: + + .. coqtop:: all + + Check nil. + Check cons. + + Types of destructors are also quantified with :g:`(A:Set)`. + + Once again, it is possible to specify only the type of the arguments + of the constructors, and to omit the type of the conclusion: + + .. coqtop:: in + + Inductive list (A:Set) : Set := nil | cons (_:A) (_:list A). + +.. note:: + + It is possible in the type of a constructor, to + invoke recursively the inductive definition on an argument which is not + the parameter itself. + + One can define : + + .. coqtop:: all + + Inductive list2 (A:Set) : Set := + | nil2 : list2 A + | cons2 : A -> list2 (A*A) -> list2 A. + + that can also be written by specifying only the type of the arguments: + + .. coqtop:: all reset + + Inductive list2 (A:Set) : Set := nil2 | cons2 (_:A) (_:list2 (A*A)). + + But the following definition will give an error: + + .. coqtop:: all + + Fail Inductive listw (A:Set) : Set := + | nilw : listw (A*A) + | consw : A -> listw (A*A) -> listw (A*A). + + because the conclusion of the type of constructors should be :g:`listw A` + in both cases. + + + A parametrized inductive definition can be defined using annotations + instead of parameters but it will sometimes give a different (bigger) + sort for the inductive definition and will produce a less convenient + rule for case elimination. + +.. flag:: Uniform Inductive Parameters + + When this option is set (it is off by default), + inductive definitions are abstracted over their parameters + before type checking constructors, allowing to write: + + .. coqtop:: all undo + + Set Uniform Inductive Parameters. + Inductive list3 (A:Set) : Set := + | nil3 : list3 + | cons3 : A -> list3 -> list3. + + This behavior is essentially equivalent to starting a new section + and using :cmd:`Context` to give the uniform parameters, like so + (cf. :ref:`section-mechanism`): + + .. coqtop:: all undo + + Section list3. + Context (A:Set). + Inductive list3 : Set := + | nil3 : list3 + | cons3 : A -> list3 -> list3. + End list3. + +.. seealso:: + Section :ref:`inductive-definitions` and the :tacn:`induction` tactic. + +Variants +~~~~~~~~ + +.. cmd:: Variant @ident @binders {? : @type } := {? | } @ident : @type {* | @ident : @type} + + The :cmd:`Variant` command is identical to the :cmd:`Inductive` command, except + that it disallows recursive definition of types (for instance, lists cannot + be defined using :cmd:`Variant`). No induction scheme is generated for + this variant, unless option :flag:`Nonrecursive Elimination Schemes` is on. + + .. exn:: The @num th argument of @ident must be @ident in @type. + :undocumented: + +Mutually defined inductive types +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. cmdv:: Inductive @ident {? : @type } := {? | } {*| @ident : @type } {* with {? | } {*| @ident {? : @type } } } + + This variant allows defining a block of mutually inductive types. + It has the same semantics as the above :cmd:`Inductive` definition for each + :token:`ident`. All :token:`ident` are simultaneously added to the environment. + Then well-typing of constructors can be checked. Each one of the :token:`ident` + can be used on its own. + + .. cmdv:: Inductive @ident @binders {? : @type } := {? | } {*| @ident : @type } {* with {? | } {*| @ident @binders {? : @type } } } + + In this variant, the inductive definitions are parametrized + with :token:`binders`. However, parameters correspond to a local context + in which the whole set of inductive declarations is done. For this + reason, the parameters must be strictly the same for each inductive types. + +.. example:: + + The typical example of a mutual inductive data type is the one for trees and + forests. We assume given two types :g:`A` and :g:`B` as variables. It can + be declared the following way. + + .. coqtop:: in + + Variables A B : Set. + + Inductive tree : Set := node : A -> forest -> tree + + with forest : Set := + | leaf : B -> forest + | cons : tree -> forest -> forest. + + This declaration generates automatically six induction principles. They are + respectively called :g:`tree_rec`, :g:`tree_ind`, :g:`tree_rect`, + :g:`forest_rec`, :g:`forest_ind`, :g:`forest_rect`. These ones are not the most + general ones but are just the induction principles corresponding to each + inductive part seen as a single inductive definition. + + To illustrate this point on our example, we give the types of :g:`tree_rec` + and :g:`forest_rec`. + + .. coqtop:: all + + Check tree_rec. + + Check forest_rec. + + Assume we want to parametrize our mutual inductive definitions with the + two type variables :g:`A` and :g:`B`, the declaration should be + done the following way: + + .. coqtop:: in + + Inductive tree (A B:Set) : Set := node : A -> forest A B -> tree A B + + with forest (A B:Set) : Set := + | leaf : B -> forest A B + | cons : tree A B -> forest A B -> forest A B. + + Assume we define an inductive definition inside a section + (cf. :ref:`section-mechanism`). When the section is closed, the variables + declared in the section and occurring free in the declaration are added as + parameters to the inductive definition. + +.. seealso:: + A generic command :cmd:`Scheme` is useful to build automatically various + mutual induction principles. + +.. _coinductive-types: + +Co-inductive types +~~~~~~~~~~~~~~~~~~ + +The objects of an inductive type are well-founded with respect to the +constructors of the type. In other words, such objects contain only a +*finite* number of constructors. Co-inductive types arise from relaxing +this condition, and admitting types whose objects contain an infinity of +constructors. Infinite objects are introduced by a non-ending (but +effective) process of construction, defined in terms of the constructors +of the type. + +.. cmd:: CoInductive @ident @binders {? : @type } := {? | } @ident : @type {* | @ident : @type} + + This command introduces a co-inductive type. + The syntax of the command is the same as the command :cmd:`Inductive`. + No principle of induction is derived from the definition of a co-inductive + type, since such principles only make sense for inductive types. + For co-inductive types, the only elimination principle is case analysis. + +.. example:: + + An example of a co-inductive type is the type of infinite sequences of + natural numbers, usually called streams. + + .. coqtop:: in + + CoInductive Stream : Set := Seq : nat -> Stream -> Stream. + + The usual destructors on streams :g:`hd:Stream->nat` and :g:`tl:Str->Str` + can be defined as follows: + + .. coqtop:: in + + Definition hd (x:Stream) := let (a,s) := x in a. + Definition tl (x:Stream) := let (a,s) := x in s. + +Definition of co-inductive predicates and blocks of mutually +co-inductive definitions are also allowed. + +.. example:: + + An example of a co-inductive predicate is the extensional equality on + streams: + + .. coqtop:: in + + CoInductive EqSt : Stream -> Stream -> Prop := + eqst : forall s1 s2:Stream, + hd s1 = hd s2 -> EqSt (tl s1) (tl s2) -> EqSt s1 s2. + + In order to prove the extensional equality of two streams :g:`s1` and :g:`s2` + we have to construct an infinite proof of equality, that is, an infinite + object of type :g:`(EqSt s1 s2)`. We will see how to introduce infinite + objects in Section :ref:`cofixpoint`. + +Caveat +++++++ + +The ability to define co-inductive types by constructors, hereafter called +*positive co-inductive types*, is known to break subject reduction. The story is +a bit long: this is due to dependent pattern-matching which implies +propositional η-equality, which itself would require full η-conversion for +subject reduction to hold, but full η-conversion is not acceptable as it would +make type-checking undecidable. + +Since the introduction of primitive records in Coq 8.5, an alternative +presentation is available, called *negative co-inductive types*. This consists +in defining a co-inductive type as a primitive record type through its +projections. Such a technique is akin to the *co-pattern* style that can be +found in e.g. Agda, and preserves subject reduction. + +The above example can be rewritten in the following way. + +.. coqtop:: all + + Set Primitive Projections. + CoInductive Stream : Set := Seq { hd : nat; tl : Stream }. + CoInductive EqSt (s1 s2: Stream) : Prop := eqst { + eqst_hd : hd s1 = hd s2; + eqst_tl : EqSt (tl s1) (tl s2); + }. + +Some properties that hold over positive streams are lost when going to the +negative presentation, typically when they imply equality over streams. +For instance, propositional η-equality is lost when going to the negative +presentation. It is nonetheless logically consistent to recover it through an +axiom. + +.. coqtop:: all + + Axiom Stream_eta : forall s: Stream, s = cons (hs s) (tl s). + +More generally, as in the case of positive coinductive types, it is consistent +to further identify extensional equality of coinductive types with propositional +equality: + +.. coqtop:: all + + Axiom Stream_ext : forall (s1 s2: Stream), EqSt s1 s2 -> s1 = s2. + +As of Coq 8.9, it is now advised to use negative co-inductive types rather than +their positive counterparts. + +.. seealso:: + :ref:`primitive_projections` for more information about negative + records and primitive projections. + + +Definition of recursive functions +--------------------------------- + +Definition of functions by recursion over inductive objects +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +This section describes the primitive form of definition by recursion over +inductive objects. See the :cmd:`Function` command for more advanced +constructions. + +.. _Fixpoint: + +.. cmd:: Fixpoint @ident @binders {? {struct @ident} } {? : @type } := @term + + This command allows defining functions by pattern matching over inductive + objects using a fixed point construction. The meaning of this declaration is + to define :token:`ident` a recursive function with arguments specified by + the :token:`binders` such that :token:`ident` applied to arguments + corresponding to these :token:`binders` has type :token:`type`, and is + equivalent to the expression :token:`term`. The type of :token:`ident` is + consequently :n:`forall @binders, @type` and its value is equivalent + to :n:`fun @binders => @term`. + + To be accepted, a :cmd:`Fixpoint` definition has to satisfy some syntactical + constraints on a special argument called the decreasing argument. They + are needed to ensure that the :cmd:`Fixpoint` definition always terminates. + The point of the :n:`{struct @ident}` annotation is to let the user tell the + system which argument decreases along the recursive calls. + + The :n:`{struct @ident}` annotation may be left implicit, in this case the + system tries successively arguments from left to right until it finds one + that satisfies the decreasing condition. + + .. note:: + + + Some fixpoints may have several arguments that fit as decreasing + arguments, and this choice influences the reduction of the fixpoint. + Hence an explicit annotation must be used if the leftmost decreasing + argument is not the desired one. Writing explicit annotations can also + speed up type checking of large mutual fixpoints. + + + In order to keep the strong normalization property, the fixed point + reduction will only be performed when the argument in position of the + decreasing argument (which type should be in an inductive definition) + starts with a constructor. + + + .. example:: + + One can define the addition function as : + + .. coqtop:: all + + Fixpoint add (n m:nat) {struct n} : nat := + match n with + | O => m + | S p => S (add p m) + end. + + The match operator matches a value (here :g:`n`) with the various + constructors of its (inductive) type. The remaining arguments give the + respective values to be returned, as functions of the parameters of the + corresponding constructor. Thus here when :g:`n` equals :g:`O` we return + :g:`m`, and when :g:`n` equals :g:`(S p)` we return :g:`(S (add p m))`. + + The match operator is formally described in + Section :ref:`match-construction`. + The system recognizes that in the inductive call :g:`(add p m)` the first + argument actually decreases because it is a *pattern variable* coming + from :g:`match n with`. + + .. example:: + + The following definition is not correct and generates an error message: + + .. coqtop:: all + + Fail Fixpoint wrongplus (n m:nat) {struct n} : nat := + match m with + | O => n + | S p => S (wrongplus n p) + end. + + because the declared decreasing argument :g:`n` does not actually + decrease in the recursive call. The function computing the addition over + the second argument should rather be written: + + .. coqtop:: all + + Fixpoint plus (n m:nat) {struct m} : nat := + match m with + | O => n + | S p => S (plus n p) + end. + + .. example:: + + The recursive call may not only be on direct subterms of the recursive + variable :g:`n` but also on a deeper subterm and we can directly write + the function :g:`mod2` which gives the remainder modulo 2 of a natural + number. + + .. coqtop:: all + + Fixpoint mod2 (n:nat) : nat := + match n with + | O => O + | S p => match p with + | O => S O + | S q => mod2 q + end + end. + + + .. cmdv:: Fixpoint @ident @binders {? {struct @ident} } {? : @type } := @term {* with @ident @binders {? : @type } := @term } + + This variant allows defining simultaneously several mutual fixpoints. + It is especially useful when defining functions over mutually defined + inductive types. + + .. example:: + + The size of trees and forests can be defined the following way: + + .. coqtop:: all + + Fixpoint tree_size (t:tree) : nat := + match t with + | node a f => S (forest_size f) + end + with forest_size (f:forest) : nat := + match f with + | leaf b => 1 + | cons t f' => (tree_size t + forest_size f') + end. + +.. _cofixpoint: + +Definitions of recursive objects in co-inductive types +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. cmd:: CoFixpoint @ident {? @binders } {? : @type } := @term + + This command introduces a method for constructing an infinite object of a + coinductive type. For example, the stream containing all natural numbers can + be introduced applying the following method to the number :g:`O` (see + Section :ref:`coinductive-types` for the definition of :g:`Stream`, :g:`hd` + and :g:`tl`): + + .. coqtop:: all + + CoFixpoint from (n:nat) : Stream := Seq n (from (S n)). + + Oppositely to recursive ones, there is no decreasing argument in a + co-recursive definition. To be admissible, a method of construction must + provide at least one extra constructor of the infinite object for each + iteration. A syntactical guard condition is imposed on co-recursive + definitions in order to ensure this: each recursive call in the + definition must be protected by at least one constructor, and only by + constructors. That is the case in the former definition, where the single + recursive call of :g:`from` is guarded by an application of :g:`Seq`. + On the contrary, the following recursive function does not satisfy the + guard condition: + + .. coqtop:: all + + Fail CoFixpoint filter (p:nat -> bool) (s:Stream) : Stream := + if p (hd s) then Seq (hd s) (filter p (tl s)) else filter p (tl s). + + The elimination of co-recursive definition is done lazily, i.e. the + definition is expanded only when it occurs at the head of an application + which is the argument of a case analysis expression. In any other + context, it is considered as a canonical expression which is completely + evaluated. We can test this using the command :cmd:`Eval`, which computes + the normal forms of a term: + + .. coqtop:: all + + Eval compute in (from 0). + Eval compute in (hd (from 0)). + Eval compute in (tl (from 0)). + + .. cmdv:: CoFixpoint @ident {? @binders } {? : @type } := @term {* with @ident {? @binders } : {? @type } := @term } + + As in the :cmd:`Fixpoint` command, it is possible to introduce a block of + mutually dependent methods. + +.. _Assertions: + +Assertions and proofs +--------------------- + +An assertion states a proposition (or a type) of which the proof (or an +inhabitant of the type) is interactively built using tactics. The interactive +proof mode is described in Chapter :ref:`proofhandling` and the tactics in +Chapter :ref:`Tactics`. The basic assertion command is: + +.. cmd:: Theorem @ident {? @binders } : @type + + After the statement is asserted, Coq needs a proof. Once a proof of + :token:`type` under the assumptions represented by :token:`binders` is given and + validated, the proof is generalized into a proof of :n:`forall @binders, @type` and + the theorem is bound to the name :token:`ident` in the environment. + + .. exn:: The term @term has type @type which should be Set, Prop or Type. + :undocumented: + + .. exn:: @ident already exists. + :name: @ident already exists. (Theorem) + + The name you provided is already defined. You have then to choose + another name. + + .. exn:: Nested proofs are not allowed unless you turn option Nested Proofs Allowed on. + + You are asserting a new statement while already being in proof editing mode. + This feature, called nested proofs, is disabled by default. + To activate it, turn option :flag:`Nested Proofs Allowed` on. + + .. cmdv:: Lemma @ident {? @binders } : @type + Remark @ident {? @binders } : @type + Fact @ident {? @binders } : @type + Corollary @ident {? @binders } : @type + Proposition @ident {? @binders } : @type + :name: Lemma; Remark; Fact; Corollary; Proposition + + These commands are all synonyms of :n:`Theorem @ident {? @binders } : type`. + +.. cmdv:: Theorem @ident {? @binders } : @type {* with @ident {? @binders } : @type} + + This command is useful for theorems that are proved by simultaneous induction + over a mutually inductive assumption, or that assert mutually dependent + statements in some mutual co-inductive type. It is equivalent to + :cmd:`Fixpoint` or :cmd:`CoFixpoint` but using tactics to build the proof of + the statements (or the body of the specification, depending on the point of + view). The inductive or co-inductive types on which the induction or + coinduction has to be done is assumed to be non ambiguous and is guessed by + the system. + + Like in a :cmd:`Fixpoint` or :cmd:`CoFixpoint` definition, the induction hypotheses + have to be used on *structurally smaller* arguments (for a :cmd:`Fixpoint`) or + be *guarded by a constructor* (for a :cmd:`CoFixpoint`). The verification that + recursive proof arguments are correct is done only at the time of registering + the lemma in the environment. To know if the use of induction hypotheses is + correct at some time of the interactive development of a proof, use the + command :cmd:`Guarded`. + + The command can be used also with :cmd:`Lemma`, :cmd:`Remark`, etc. instead of + :cmd:`Theorem`. + +.. cmdv:: Definition @ident {? @binders } : @type + + This allows defining a term of type :token:`type` using the proof editing + mode. It behaves as :cmd:`Theorem` but is intended to be used in conjunction with + :cmd:`Defined` in order to define a constant of which the computational + behavior is relevant. + + The command can be used also with :cmd:`Example` instead of :cmd:`Definition`. + + .. seealso:: :cmd:`Opaque`, :cmd:`Transparent`, :tacn:`unfold`. + +.. cmdv:: Let @ident {? @binders } : @type + + Like :n:`Definition @ident {? @binders } : @type` except that the definition is + turned into a let-in definition generalized over the declarations depending + on it after closing the current section. + +.. cmdv:: Fixpoint @ident @binders : @type {* with @ident @binders : @type} + + This generalizes the syntax of :cmd:`Fixpoint` so that one or more bodies + can be defined interactively using the proof editing mode (when a + body is omitted, its type is mandatory in the syntax). When the block + of proofs is completed, it is intended to be ended by :cmd:`Defined`. + +.. cmdv:: CoFixpoint @ident {? @binders } : @type {* with @ident {? @binders } : @type} + + This generalizes the syntax of :cmd:`CoFixpoint` so that one or more bodies + can be defined interactively using the proof editing mode. + +A proof starts by the keyword :cmd:`Proof`. Then Coq enters the proof editing mode +until the proof is completed. The proof editing mode essentially contains +tactics that are described in chapter :ref:`Tactics`. Besides tactics, there +are commands to manage the proof editing mode. They are described in Chapter +:ref:`proofhandling`. + +When the proof is completed it should be validated and put in the environment +using the keyword :cmd:`Qed`. + +.. note:: + + #. Several statements can be simultaneously asserted provided option + :flag:`Nested Proofs Allowed` was turned on. + + #. Not only other assertions but any vernacular command can be given + while in the process of proving a given assertion. In this case, the + command is understood as if it would have been given before the + statements still to be proved. Nonetheless, this practice is discouraged + and may stop working in future versions. + + #. Proofs ended by :cmd:`Qed` are declared opaque. Their content cannot be + unfolded (see :ref:`performingcomputations`), thus + realizing some form of *proof-irrelevance*. To be able to unfold a + proof, the proof should be ended by :cmd:`Defined`. + + #. :cmd:`Proof` is recommended but can currently be omitted. On the opposite + side, :cmd:`Qed` (or :cmd:`Defined`) is mandatory to validate a proof. + + #. One can also use :cmd:`Admitted` in place of :cmd:`Qed` to turn the + current asserted statement into an axiom and exit the proof editing mode. + +.. _gallina-attributes: + +Attributes +----------- + +Any vernacular command can be decorated with a list of attributes, enclosed +between ``#[`` (hash and opening square bracket) and ``]`` (closing square bracket) +and separated by commas ``,``. Multiple space-separated blocks may be provided. + +Each attribute has a name (an identifier) and may have a value. +A value is either a :token:`string` (in which case it is specified with an equal ``=`` sign), +or a list of attributes, enclosed within brackets. + +Currently, +the following attributes names are recognized: + +``monomorphic``, ``polymorphic`` + Take no value, analogous to the ``Monomorphic`` and ``Polymorphic`` flags + (see :ref:`polymorphicuniverses`). + +``program`` + Takes no value, analogous to the ``Program`` flag + (see :ref:`programs`). + +``global``, ``local`` + Take no value, analogous to the ``Global`` and ``Local`` flags + (see :ref:`controlling-locality-of-commands`). + +``deprecated`` + Takes as value the optional attributes ``since`` and ``note``; + both have a string value. + + This attribute can trigger the following warnings: + + .. warn:: Tactic @qualid is deprecated since @string. @string. + :undocumented: + + .. warn:: Tactic Notation @qualid is deprecated since @string. @string. + :undocumented: + +.. example:: + + .. coqtop:: all reset + + From Coq Require Program. + #[program] Definition one : nat := S _. + Next Obligation. + exact O. + Defined. + + #[deprecated(since="8.9.0", note="Use idtac instead.")] + Ltac foo := idtac. + + Goal True. + Proof. + now foo. + Abort. + +.. [1] + This is similar to the expression “*entry* :math:`\{` sep *entry* + :math:`\}`” in standard BNF, or “*entry* :math:`(` sep *entry* + :math:`)`\ \*” in the syntax of regular expressions. + +.. [2] + Except if the inductive type is empty in which case there is no + equation that can be used to infer the return type. diff --git a/doc/sphinx/language/module-system.rst b/doc/sphinx/language/module-system.rst index e6a6736654..15fee91245 100644 --- a/doc/sphinx/language/module-system.rst +++ b/doc/sphinx/language/module-system.rst @@ -1,6 +1,3 @@ -.. include:: ../preamble.rst -.. include:: ../replaces.rst - .. _themodulesystem: The Module System |