(* Title: ZF/Coind/Language.ML
ID: $Id$
Author: Jacob Frost, Cambridge University Computer Laboratory
Copyright 1995 University of Cambridge
*)
(* ############################################################ *)
(* General lemmas *)
(* ############################################################ *)
goal ZF.thy "!!a.~a=b ==> ~a:{b}";
by (fast_tac ZF_cs 1);
qed "notsingletonI";
goal ZF.thy "!!a.~a:{b} ==> ~a=b";
by (fast_tac ZF_cs 1);
qed "notsingletonD";
val prems = goal ZF.thy "[| a~:{b}; a~=b ==> P |] ==> P";
by (cut_facts_tac prems 1);
by (resolve_tac prems 1);
by (fast_tac ZF_cs 1);
qed "notsingletonE";
goal ZF.thy "!!x. x : A Un B ==> x: B Un A";
by (fast_tac ZF_cs 1);
qed "lem_fix";
goal ZF.thy "!!A.[| x~:A; x=y |] ==> y~:A";
by (fast_tac ZF_cs 1);
qed "map_lem1";
open Language;