diff options
Diffstat (limited to 'theories/Logic/Decidable.v')
| -rw-r--r-- | theories/Logic/Decidable.v | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/theories/Logic/Decidable.v b/theories/Logic/Decidable.v index a7c098e8..00d63252 100644 --- a/theories/Logic/Decidable.v +++ b/theories/Logic/Decidable.v @@ -5,7 +5,7 @@ (* // * This file is distributed under the terms of the *) (* * GNU Lesser General Public License Version 2.1 *) (************************************************************************) -(*i $Id: Decidable.v 10500 2008-02-02 15:51:00Z letouzey $ i*) +(*i $Id: Decidable.v 11735 2009-01-02 17:22:31Z herbelin $ i*) (** Properties of decidable propositions *) @@ -80,6 +80,13 @@ Proof. unfold decidable; tauto. Qed. +Theorem not_iff : + forall A B:Prop, decidable A -> decidable B -> + ~ (A <-> B) -> (A /\ ~ B) \/ (~ A /\ B). +Proof. +unfold decidable; tauto. +Qed. + (** Results formulated with iff, used in FSetDecide. Negation are expanded since it is unclear whether setoid rewrite will always perform conversion. *) |