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patrickt/either.hs

Created June 3, 2014 18:56
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either.hs
data Either a b = Left a | Right b
isLeft :: Either a b -> Bool
isLeft (Left _) = True
isLeft _ = False
either :: (a -> c) -> (b -> c) -> Either a b -> c
either f _ (Left x) = f x
either _ g (Right y) = g y
lefts :: [Either a b] -> [a]
lefts x = [a | Left a <- x]
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