diff -r 1dfdbd66093a -r ae8d187600e7 src/FOL/ex/Iff_Oracle.thy
--- a/src/FOL/ex/Iff_Oracle.thy	Fri Oct 29 17:15:28 2010 -0700
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,76 +0,0 @@
-(*  Title:      FOL/ex/Iff_Oracle.thy
-    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
-    Copyright   1996  University of Cambridge
-*)
-
-header {* Example of Declaring an Oracle *}
-
-theory Iff_Oracle
-imports FOL
-begin
-
-subsection {* Oracle declaration *}
-
-text {*
-  This oracle makes tautologies of the form @{text "P <-> P <-> P <-> P"}.
-  The length is specified by an integer, which is checked to be even
-  and positive.
-*}
-
-oracle iff_oracle = {*
-  let
-    fun mk_iff 1 = Var (("P", 0), @{typ o})
-      | mk_iff n = FOLogic.iff $ Var (("P", 0), @{typ o}) $ mk_iff (n - 1);
-  in
-    fn (thy, n) =>
-      if n > 0 andalso n mod 2 = 0
-      then Thm.cterm_of thy (FOLogic.mk_Trueprop (mk_iff n))
-      else raise Fail ("iff_oracle: " ^ string_of_int n)
-  end
-*}
-
-
-subsection {* Oracle as low-level rule *}
-
-ML {* iff_oracle (@{theory}, 2) *}
-ML {* iff_oracle (@{theory}, 10) *}
-ML {* Thm.proof_body_of (iff_oracle (@{theory}, 10)) *}
-
-text {* These oracle calls had better fail. *}
-
-ML {*
-  (iff_oracle (@{theory}, 5); error "?")
-    handle Fail _ => warning "Oracle failed, as expected"
-*}
-
-ML {*
-  (iff_oracle (@{theory}, 1); error "?")
-    handle Fail _ => warning "Oracle failed, as expected"
-*}
-
-
-subsection {* Oracle as proof method *}
-
-method_setup iff = {*
-  Scan.lift Parse.nat >> (fn n => fn ctxt =>
-    SIMPLE_METHOD
-      (HEADGOAL (Tactic.rtac (iff_oracle (ProofContext.theory_of ctxt, n)))
-        handle Fail _ => no_tac))
-*} "iff oracle"
-
-
-lemma "A <-> A"
-  by (iff 2)
-
-lemma "A <-> A <-> A <-> A <-> A <-> A <-> A <-> A <-> A <-> A"
-  by (iff 10)
-
-lemma "A <-> A <-> A <-> A <-> A"
-  apply (iff 5)?
-  oops
-
-lemma A
-  apply (iff 1)?
-  oops
-
-end