Hi, I've encountered a bug of partition in Data.List shipped with ghc-6.2 and hugs(Nov 2002) It cannot work with an infinite list. Example: > partition (==0) (cycle [0,1]) does not return and so not conform to the specification in the Haskell 98 and the library document. I found some discussion on this bug in the haskell mailing-list archive, e.g. http://www.mail-archive.com/haskell@haskell.org/msg07789.html Is there some good reason not to change this behaviour? (And if it is, I think that the library document should be fixed.) Patch: --- List.hs.orig Thu Feb 5 04:15:59 2004 +++ List.hs Thu Feb 5 04:16:31 2004 @@ -240,8 +240,8 @@ {-# INLINE partition #-} partition p xs = foldr (select p) ([],[]) xs -select p x (ts,fs) | p x = (x:ts,fs) - | otherwise = (ts, x:fs) +select p x ~(ts,fs) | p x = (x:ts,fs) + | otherwise = (ts, x:fs) -- @mapAccumL@ behaves like a combination -- of @map@ and @foldl@; --- Koji Nakahara