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/[EMAIL PROTECTED]/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
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