Usually I start out writing such functions into Bool, but then end up generalizing them to Maybe, in this case isLeft :: Either a b -> Maybe a isLeft (Left a) = Just a isLeft Right{} = Nothing etc. If I really need a Bool, I can compose them with isJust/isNothing. On 07.08.13 9:18 AM, Henning Thielemann wrote:
On Wed, 7 Aug 2013, Erik de Castro Lopo wrote:
And while we're at it:
isLeft :: Either a b -> Bool isLeft (Left _) = True isLeft (Right _) = False
isRight :: Either a b -> Bool isRight (Left _) = False isRight (Right _) = True
http://www.haskell.org/pipermail/libraries/2012-November/018709.html http://www.haskell.org/pipermail/libraries/2012-December/018716.html
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