leftToMaybe/rightToMaybe

[John Wiegley]

>>>>> Erik de Castro Lopo <mle+hs at mega-nerd.com> writes:

> 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

And what about:

fromLeft :: a -> Either a b -> a
fromLeft _ (Left x) = x
fromLeft x _ = x

fromRight :: b -> Either a b -> b
fromRight _ (Right x) = x
fromRight x _ = x

-- 
John Wiegley
FP Complete                         Haskell tools, training and consulting
http://fpcomplete.com               johnw on #haskell/irc.freenode.net