1.1 --- a/src/HOL/ex/Higher_Order_Logic.thy Thu Dec 20 21:14:59 2001 +0100
1.2 +++ b/src/HOL/ex/Higher_Order_Logic.thy Thu Dec 20 21:15:37 2001 +0100
1.3 @@ -308,4 +308,15 @@
1.4 qed
1.5 qed
1.6
1.7 +lemma (in classical) "(\<not> A \<Longrightarrow> A) \<Longrightarrow> A" (* FIXME *)
1.8 +proof -
1.9 + assume r: "\<not> A \<Longrightarrow> A"
1.10 + show A
1.11 + proof (rule classical_cases)
1.12 + assume A thus A .
1.13 + next
1.14 + assume "\<not> A" thus A by (rule r)
1.15 + qed
1.16 +qed
1.17 +
1.18 end