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+(***********************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team    *)
+(* <O___,, *        INRIA-Rocquencourt  &  LRI-CNRS-Orsay              *)
+(*   \VV/  *************************************************************)
+(*    //   *      This file is distributed under the terms of the      *)
+(*         *       GNU Lesser General Public License Version 2.1       *)
+(***********************************************************************)
+
+Require Import Equalities Bool SetoidList RelationPairs.
+
+(** In a BooleanEqualityType, [eqb] is compatible with [eq] *)
+
+Module BoolEqualityFacts (Import E : BooleanEqualityType).
+
+Instance eqb_compat : Proper (E.eq ==> E.eq ==> Logic.eq) eqb.
+Proof.
+intros x x' Exx' y y' Eyy'.
+apply eq_true_iff_eq.
+rewrite 2 eqb_eq, Exx', Eyy'; auto with *.
+Qed.
+
+End BoolEqualityFacts.
+
+
+(** * Keys and datas used in FMap *)
+Module KeyDecidableType(Import D:DecidableType).
+
+ Section Elt.
+ Variable elt : Type.
+ Notation key:=t.
+
+  Local Open Scope signature_scope.
+
+  Definition eqk : relation (key*elt) := eq @@1.
+  Definition eqke : relation (key*elt) := eq * Logic.eq.
+  Hint Unfold eqk eqke.
+
+  (* eqke is stricter than eqk *)
+
+  Global Instance eqke_eqk : subrelation eqke eqk.
+  Proof. firstorder. Qed.
+
+  (* eqk, eqke are equalities, ltk is a strict order *)
+
+  Global Instance eqk_equiv : Equivalence eqk.
+
+  Global Instance eqke_equiv : Equivalence eqke.
+
+  (* Additionnal facts *)
+
+  Lemma InA_eqke_eqk :
+     forall x m, InA eqke x m -> InA eqk x m.
+  Proof.
+    unfold eqke, RelProd; induction 1; firstorder.
+  Qed.
+  Hint Resolve InA_eqke_eqk.
+
+  Lemma InA_eqk : forall p q m, eqk p q -> InA eqk p m -> InA eqk q m.
+  Proof.
+   intros. rewrite <- H; auto.
+  Qed.
+
+  Definition MapsTo (k:key)(e:elt):= InA eqke (k,e).
+  Definition In k m := exists e:elt, MapsTo k e m.
+
+  Hint Unfold MapsTo In.
+
+  (* An alternative formulation for [In k l] is [exists e, InA eqk (k,e) l] *)
+
+  Lemma In_alt : forall k l, In k l <-> exists e, InA eqk (k,e) l.
+  Proof.
+  firstorder.
+  exists x; auto.
+  induction H.
+  destruct y; compute in H.
+  exists e; left; auto.
+  destruct IHInA as [e H0].
+  exists e; auto.
+  Qed.
+
+  Lemma In_alt2 : forall k l, In k l <-> Exists (fun p => eq k (fst p)) l.
+  Proof.
+  unfold In, MapsTo.
+  setoid_rewrite Exists_exists; setoid_rewrite InA_alt.
+  firstorder.
+  exists (snd x), x; auto.
+  Qed.
+
+  Lemma In_nil : forall k, In k nil <-> False.
+  Proof.
+  intros; rewrite In_alt2; apply Exists_nil.
+  Qed.
+
+  Lemma In_cons : forall k p l,
+   In k (p::l) <-> eq k (fst p) \/ In k l.
+  Proof.
+  intros; rewrite !In_alt2, Exists_cons; intuition.
+  Qed.
+
+  Global Instance MapsTo_compat :
+   Proper (eq==>Logic.eq==>equivlistA eqke==>iff) MapsTo.
+  Proof.
+  intros x x' Hx e e' He l l' Hl. unfold MapsTo.
+  rewrite Hx, He, Hl; intuition.
+  Qed.
+
+  Global Instance In_compat : Proper (eq==>equivlistA eqk==>iff) In.
+  Proof.
+  intros x x' Hx l l' Hl. rewrite !In_alt.
+  setoid_rewrite Hl. setoid_rewrite Hx. intuition.
+  Qed.
+
+  Lemma MapsTo_eq : forall l x y e, eq x y -> MapsTo x e l -> MapsTo y e l.
+  Proof. intros l x y e EQ. rewrite <- EQ; auto. Qed.
+
+  Lemma In_eq : forall l x y, eq x y -> In x l -> In y l.
+  Proof. intros l x y EQ. rewrite <- EQ; auto. Qed.
+
+  Lemma In_inv : forall k k' e l, In k ((k',e) :: l) -> eq k k' \/ In k l.
+  Proof.
+    intros; invlist In; invlist MapsTo. compute in * |- ; intuition.
+    right; exists x; auto.
+  Qed.
+
+  Lemma In_inv_2 : forall k k' e e' l,
+      InA eqk (k, e) ((k', e') :: l) -> ~ eq k k' -> InA eqk (k, e) l.
+  Proof.
+   intros; invlist InA; intuition.
+  Qed.
+
+  Lemma In_inv_3 : forall x x' l,
+      InA eqke x (x' :: l) -> ~ eqk x x' -> InA eqke x l.
+  Proof.
+   intros; invlist InA; compute in * |- ; intuition.
+  Qed.
+
+ End Elt.
+
+ Hint Unfold eqk eqke.
+ Hint Extern 2 (eqke ?a ?b) => split.
+ Hint Resolve InA_eqke_eqk.
+ Hint Unfold MapsTo In.
+ Hint Resolve In_inv_2 In_inv_3.
+
+End KeyDecidableType.
+
+
+(** * PairDecidableType 
+   
+   From two decidable types, we can build a new DecidableType
+   over their cartesian product. *)
+
+Module PairDecidableType(D1 D2:DecidableType) <: DecidableType.
+
+ Definition t := (D1.t * D2.t)%type.
+
+ Definition eq := (D1.eq * D2.eq)%signature.
+
+ Instance eq_equiv : Equivalence eq.
+
+ Definition eq_dec : forall x y, { eq x y }+{ ~eq x y }.
+ Proof.
+ intros (x1,x2) (y1,y2); unfold eq; simpl.
+ destruct (D1.eq_dec x1 y1); destruct (D2.eq_dec x2 y2);
+  compute; intuition.
+ Defined.
+
+End PairDecidableType.
+
+(** Similarly for pairs of UsualDecidableType *)
+
+Module PairUsualDecidableType(D1 D2:UsualDecidableType) <: UsualDecidableType.
+ Definition t := (D1.t * D2.t)%type.
+ Definition eq := @eq t.
+ Program Instance eq_equiv : Equivalence eq.
+ Definition eq_dec : forall x y, { eq x y }+{ ~eq x y }.
+ Proof.
+ intros (x1,x2) (y1,y2);
+ destruct (D1.eq_dec x1 y1); destruct (D2.eq_dec x2 y2);
+ unfold eq, D1.eq, D2.eq in *; simpl;
+ (left; f_equal; auto; fail) ||
+ (right; intro H; injection H; auto).
+ Defined.
+
+End PairUsualDecidableType.