# HG changeset patch # User paulson # Date 828101798 -3600 # Node ID 26570790f089b7dc55f896f16e7baed8049109d2 # Parent 8c84606672fe922825e001be2025b3b932806279 new lemma for mutilated chess board diff -r 8c84606672fe -r 26570790f089 src/HOL/subset.ML --- a/src/HOL/subset.ML Fri Mar 29 11:38:47 1996 +0100 +++ b/src/HOL/subset.ML Fri Mar 29 13:16:38 1996 +0100 @@ -16,6 +16,9 @@ by (fast_tac set_cs 1); qed "subset_insert"; +qed_goal "subset_empty_iff" Set.thy "(A<={}) = (A={})" + (fn _=> [ (fast_tac (set_cs addIs [equalityI]) 1) ]); + (*** Big Union -- least upper bound of a set ***) val prems = goal Set.thy