leftToMaybe/rightToMaybe

[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


Erik
-- 
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Erik de Castro Lopo
http://www.mega-nerd.com/