On Thu, 9 Nov 2006, Ross Paterson wrote:
On Fri, Nov 03, 2006 at 09:57:35AM -0500, roconnor@theorem.ca wrote:
I have attached a new patch to the trac that now uses the identifier partitionEithers.
I'd suggest also having the following variant, by analogy with mapMaybe:
-- | Map values and separate the 'Left' and 'Right' results. mapEither :: (a -> Either b c) -> [a] -> ([b], [c]) mapEither f = foldr (add . f) ([], []) where add (Left b) (bs, cs) = (b:bs, cs) add (Right c) (bs, cs) = (bs, c:cs)
After my turnaround http://www.haskell.org/pipermail/libraries/2006-November/006204.html that's what I called partitionEither. From a 'map' function I expect a similarity to 'fmap', e.g. that the main input and the output have the same type constructor (here []).