1 files changed, 96 insertions, 0 deletions
diff --git a/theories/Structures/DecidableTypeEx.v b/theories/Structures/DecidableTypeEx.v
new file mode 100644
index 00000000..4407ead4
--- /dev/null
+++ b/theories/Structures/DecidableTypeEx.v
@@ -0,0 +1,96 @@
+(***********************************************************************)
+(*  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       *)
+(***********************************************************************)
+
+(* $Id$ *)
+
+Require Import DecidableType OrderedType OrderedTypeEx.
+Set Implicit Arguments.
+Unset Strict Implicit.
+
+(** NB: This file is here only for compatibility with earlier version of
+    [FSets] and [FMap]. Please use [Structures/Equalities.v] directly now. *)
+
+(** * Examples of Decidable Type structures. *)
+
+(** A particular case of [DecidableType] where
+    the equality is the usual one of Coq. *)
+
+Module Type UsualDecidableType := Equalities.UsualDecidableTypeOrig.
+
+(** a [UsualDecidableType] is in particular an [DecidableType]. *)
+
+Module UDT_to_DT (U:UsualDecidableType) <: DecidableType := U.
+
+(** an shortcut for easily building a UsualDecidableType *)
+
+Module Type MiniDecidableType := Equalities.MiniDecidableType.
+
+Module Make_UDT (M:MiniDecidableType) <: UsualDecidableType
+ := Equalities.Make_UDT M.
+
+(** An OrderedType can now directly be seen as a DecidableType *)
+
+Module OT_as_DT (O:OrderedType) <: DecidableType := O.
+
+(** (Usual) Decidable Type for [nat], [positive], [N], [Z] *)
+
+Module Nat_as_DT <: UsualDecidableType := Nat_as_OT.
+Module Positive_as_DT <: UsualDecidableType := Positive_as_OT.
+Module N_as_DT <: UsualDecidableType := N_as_OT.
+Module Z_as_DT <: UsualDecidableType := Z_as_OT.
+
+(** From two decidable types, we can build a new DecidableType
+   over their cartesian product. *)
+
+Module PairDecidableType(D1 D2:DecidableType) <: DecidableType.
+
+ Definition t := prod D1.t D2.t.
+
+ Definition eq x y := D1.eq (fst x) (fst y) /\ D2.eq (snd x) (snd y).
+
+ Lemma eq_refl : forall x : t, eq x x.
+ Proof.
+ intros (x1,x2); red; simpl; auto.
+ Qed.
+
+ Lemma eq_sym : forall x y : t, eq x y -> eq y x.
+ Proof.
+ intros (x1,x2) (y1,y2); unfold eq; simpl; intuition.
+ Qed.
+
+ Lemma eq_trans : forall x y z : t, eq x y -> eq y z -> eq x z.
+ Proof.
+ intros (x1,x2) (y1,y2) (z1,z2); unfold eq; simpl; intuition eauto.
+ Qed.
+
+ 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); intuition.
+ Defined.
+
+End PairDecidableType.
+
+(** Similarly for pairs of UsualDecidableType *)
+
+Module PairUsualDecidableType(D1 D2:UsualDecidableType) <: UsualDecidableType.
+ Definition t := prod D1.t D2.t.
+ Definition eq := @eq t.
+ Definition eq_refl := @refl_equal t.
+ Definition eq_sym := @sym_eq t.
+ Definition eq_trans := @trans_eq t.
+ 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.