--- a/src/FOL/ex/if.ML Sat Apr 05 16:00:00 2003 +0200
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,64 +0,0 @@
-(* Title: FOL/ex/if
- ID: $Id$
- Author: Lawrence C Paulson, Cambridge University Computer Laboratory
- Copyright 1991 University of Cambridge
-
-For ex/if.thy. First-Order Logic: the 'if' example
-*)
-
-open If;
-open Cla; (*in case structure Int is open!*)
-
-val prems = goalw If.thy [if_def]
- "[| P ==> Q; ~P ==> R |] ==> if(P,Q,R)";
-by (fast_tac (FOL_cs addIs prems) 1);
-val ifI = result();
-
-val major::prems = goalw If.thy [if_def]
- "[| if(P,Q,R); [| P; Q |] ==> S; [| ~P; R |] ==> S |] ==> S";
-by (cut_facts_tac [major] 1);
-by (fast_tac (FOL_cs addIs prems) 1);
-val ifE = result();
-
-
-goal If.thy
- "if(P, if(Q,A,B), if(Q,C,D)) <-> if(Q, if(P,A,C), if(P,B,D))";
-by (resolve_tac [iffI] 1);
-by (eresolve_tac [ifE] 1);
-by (eresolve_tac [ifE] 1);
-by (resolve_tac [ifI] 1);
-by (resolve_tac [ifI] 1);
-
-choplev 0;
-val if_cs = FOL_cs addSIs [ifI] addSEs[ifE];
-by (fast_tac if_cs 1);
-val if_commute = result();
-
-
-goal If.thy "if(if(P,Q,R), A, B) <-> if(P, if(Q,A,B), if(R,A,B))";
-by (fast_tac if_cs 1);
-val nested_ifs = result();
-
-choplev 0;
-by (rewrite_goals_tac [if_def]);
-by (fast_tac FOL_cs 1);
-result();
-
-
-(*An invalid formula. High-level rules permit a simpler diagnosis*)
-goal If.thy "if(if(P,Q,R), A, B) <-> if(P, if(Q,A,B), if(R,B,A))";
-by (fast_tac if_cs 1) handle ERROR => writeln"Failed, as expected";
-(*Check that subgoals remain: proof failed.*)
-getgoal 1;
-by (REPEAT (step_tac if_cs 1));
-
-choplev 0;
-by (rewrite_goals_tac [if_def]);
-by (fast_tac FOL_cs 1) handle ERROR => writeln"Failed, as expected";
-(*Check that subgoals remain: proof failed.*)
-getgoal 1;
-by (REPEAT (step_tac FOL_cs 1));
-
-
-
-writeln"Reached end of file.";