--- a/src/HOL/Inductive.thy Tue Jan 30 18:53:46 2001 +0100
+++ b/src/HOL/Inductive.thy Tue Jan 30 18:57:24 2001 +0100
@@ -75,7 +75,7 @@
setup PrimrecPackage.setup
theorems basic_monos [mono] =
- subset_refl imp_refl disj_mono conj_mono ex_mono all_mono
+ subset_refl imp_refl disj_mono conj_mono ex_mono all_mono if_def2
Collect_mono in_mono vimage_mono
imp_conv_disj not_not de_Morgan_disj de_Morgan_conj
not_all not_ex
--- a/src/HOL/simpdata.ML Tue Jan 30 18:53:46 2001 +0100
+++ b/src/HOL/simpdata.ML Tue Jan 30 18:57:24 2001 +0100
@@ -233,6 +233,8 @@
bind_thms ("if_splits", [split_if, split_if_asm]);
+bind_thm ("if_def2", read_instantiate [("P","\\<lambda>x. x")] split_if);
+
Goal "(if c then x else x) = x";
by (stac split_if 1);
by (Blast_tac 1);