add a left and right tactic for classical logic

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@7234 85f007b7-540e-0410-9357-904b9bb8a0f7

3 files changed, 16 insertions, 2 deletions

diff --git a/CHANGES b/CHANGES
index 8369a25850..dcd395e68a 100644
--- a/CHANGES
+++ b/CHANGES
@@ -45,6 +45,8 @@ Tactics
 - Added "autorewrite with ... in hyp [using ...]" (doc TODO).
 - Added entry constr_may_eval for tactic extensions (new syntax).
 - Fixed a "fold" bug (non critical and possible source of incompatibilities).
+- Added classical_left and classical_right which transforms |- A \/ B into 
+  ~B |- A and ~A |- B respectively.
 
 Modules
 
diff --git a/theories/Logic/Classical.v b/theories/Logic/Classical.v
index 9dd9d4d913..1c2b97ce76 100755
--- a/theories/Logic/Classical.v
+++ b/theories/Logic/Classical.v
@@ -11,4 +11,5 @@
 (** Classical Logic *)
 
 Require Export Classical_Prop.
-Require Export Classical_Pred_Type.
\ No newline at end of file
+Require Export Classical_Pred_Type.
+
diff --git a/theories/Logic/Classical_Prop.v b/theories/Logic/Classical_Prop.v
index fa509a3c02..1df6a354bd 100755
--- a/theories/Logic/Classical_Prop.v
+++ b/theories/Logic/Classical_Prop.v
@@ -82,4 +82,15 @@ simple induction 2; auto.
 Qed.
 
 Lemma proof_irrelevance : forall (P:Prop) (p1 p2:P), p1 = p2.
-Proof proof_irrelevance_cci classic.
\ No newline at end of file
+Proof proof_irrelevance_cci classic.
+
+(* classical_left  transforms |- A \/ B into ~B |- A *)
+(* classical_right transforms |- A \/ B into ~A |- B *)
+
+Ltac classical_right :=  match goal with 
+ | _:_ |-?X1 \/ _ => (elim (classic X1);intro;[left;trivial|right])
+end.
+
+Ltac classical_left := match goal with 
+| _:_ |- _ \/?X1 => (elim (classic X1);intro;[right;trivial|left])
+end.
\ No newline at end of file