On 7 August 2013 14:06, Erik de Castro Lopo
Christopher Done wrote:
How about popping these in Data.Either?
-- | Maybe get the left side of an Either. leftToMaybe :: Either a b -> Maybe a leftToMaybe = either Just (const Nothing)
-- | Maybe get the right side of an Either. rightToMaybe :: Either a b -> Maybe b rightToMaybe = either (const Nothing) Just
+1
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
If we're starting to add functions to Data.Either, I've often used something like this: mapEither :: (l -> l') -> (r -> r') -> Either l r -> Either l' r' mapEither fl fr = either (Left . fl) (Right . fr)
Erik -- ---------------------------------------------------------------------- Erik de Castro Lopo http://www.mega-nerd.com/
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