diff -r 722bf1319be5 -r fd1be45b64bf IOA/meta_theory/Option.thy
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/IOA/meta_theory/Option.thy	Wed Nov 02 11:50:09 1994 +0100
@@ -0,0 +1,3 @@
+Option = Arith +
+datatype 'a option = None | Some('a)
+end