changeset 63040 | eb4ddd18d635 |
parent 62481 | b5d8e57826df |
child 63092 | a949b2a5f51d |
--- a/src/HOL/Groups_Big.thy Sun Apr 24 21:31:14 2016 +0200 +++ b/src/HOL/Groups_Big.thy Mon Apr 25 16:09:26 2016 +0200 @@ -1137,7 +1137,7 @@ case True with insert show ?thesis by simp next case False with insert have "a \<in> B" by simp - def C \<equiv> "B - {a}" + define C where "C = B - {a}" with \<open>finite B\<close> \<open>a \<in> B\<close> have *: "B = insert a C" "finite C" "a \<notin> C" by auto with insert show ?thesis by (auto simp add: insert_commute ac_simps)