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-rw-r--r--theories/Structures/Equalities.v13
1 files changed, 13 insertions, 0 deletions
diff --git a/theories/Structures/Equalities.v b/theories/Structures/Equalities.v
index 14d34f1eb..8e72bd611 100644
--- a/theories/Structures/Equalities.v
+++ b/theories/Structures/Equalities.v
@@ -7,6 +7,7 @@
(***********************************************************************)
Require Export RelationClasses.
+Require Import Bool Morphisms Setoid.
Set Implicit Arguments.
Unset Strict Implicit.
@@ -165,6 +166,18 @@ Module Dec2Bool (E:DecidableType) <: BooleanDecidableType
Module Bool2Dec (E:BooleanEqualityType) <: BooleanDecidableType
:= E <+ HasEqBool2Dec.
+(** 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.
+now rewrite 2 eqb_eq, Exx', Eyy'.
+Qed.
+
+End BoolEqualityFacts.
(** * UsualDecidableType