diff -r 21291189b51e -r 9f35f2744fa8 prod.thy
--- a/prod.thy	Wed Mar 02 12:26:55 1994 +0100
+++ b/prod.thy	Thu Mar 17 11:27:29 1994 +0100
@@ -13,7 +13,7 @@
 Prod = Set +
 types   
 	"*"  2        (infixr 20)
-        unit 0
+        unit
 arities 
    "*"      :: (term,term)term
    unit     :: term