--- a/src/HOL/ex/While_Combinator_Example.thy Wed Jan 10 15:21:49 2018 +0100
+++ b/src/HOL/ex/While_Combinator_Example.thy Wed Jan 10 15:25:09 2018 +0100
@@ -17,7 +17,7 @@
lfp f = fst (while (\<lambda>(A, fA). A \<noteq> fA) (\<lambda>(A, fA). (fA, f fA)) ({}, f {}))"
apply (rule_tac P = "\<lambda>(A, B). (A \<subseteq> U \<and> B = f A \<and> A \<subseteq> B \<and> B \<subseteq> lfp f)" and
r = "((Pow U \<times> UNIV) \<times> (Pow U \<times> UNIV)) \<inter>
- inv_image finite_psubset (op - U o fst)" in while_rule)
+ inv_image finite_psubset ((-) U o fst)" in while_rule)
apply (subst lfp_unfold)
apply assumption
apply (simp add: monoD)