--- a/src/HOL/Library/Code_Natural.thy Thu Aug 26 12:19:50 2010 +0200
+++ b/src/HOL/Library/Code_Natural.thy Thu Aug 26 13:25:14 2010 +0200
@@ -9,7 +9,9 @@
section {* Alternative representation of @{typ code_numeral} for @{text Haskell} and @{text Scala} *}
code_include Haskell "Natural"
-{*newtype Natural = Natural Integer deriving (Eq, Show, Read);
+{*import Data.Array.ST;
+
+newtype Natural = Natural Integer deriving (Eq, Show, Read);
instance Num Natural where {
fromInteger k = Natural (if k >= 0 then k else 0);