--- a/src/HOL/ex/Puzzle.thy Fri Nov 12 18:16:48 1999 +0100
+++ b/src/HOL/ex/Puzzle.thy Mon Nov 15 09:41:06 1999 +0100
@@ -6,7 +6,7 @@
A question from "Bundeswettbewerb Mathematik"
*)
-Puzzle = Nat +
+Puzzle = Main +
consts f :: nat => nat
rules f_ax "f(f(n)) < f(Suc(n))"
end