From 8881e203658bb17d37bdea24ea3e104d0466e2e8 Mon Sep 17 00:00:00 2001
From: Stefano Zacchiroli <zack@upsilon.cc>
Date: Mon, 7 Nov 2005 10:04:22 +0000
Subject: [PATCH] added bool_elim (elimination which preserves infos on the
 eliminated value)

---
 helm/matita/library/datatypes/bool.ma | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/helm/matita/library/datatypes/bool.ma b/helm/matita/library/datatypes/bool.ma
index a4667da30..11f1d7a8c 100644
--- a/helm/matita/library/datatypes/bool.ma
+++ b/helm/matita/library/datatypes/bool.ma
@@ -19,7 +19,18 @@ include "logic/equality.ma".
 inductive bool : Set \def 
   | true : bool
   | false : bool.
-  
+
+theorem bool_elim: \forall P:bool \to Prop. \forall b:bool.
+  (b = true \to P true)
+  \to (b = false \to P false)
+  \to P b.
+  intros 2 (P b).
+  elim b;
+  [ apply H; reflexivity
+  | apply H1; reflexivity
+  ]
+qed.
+
 theorem not_eq_true_false : true \neq false.
 simplify.intro.
 change with 
-- 
2.39.2