[Haskell-cafe] A function for Maybes
wagner.andrew at gmail.com
Thu Jan 25 09:22:54 EST 2007
forall r (m :: * -> *) a1. (Monad m) => (a1 -> r) -> m a1 -> m r
> liftM (+2) (Just 3
liftM (+2) Nothing
(Thanks to allbery_b for contributing to the discussion on #haskell)
On 1/25/07, John Ky <newhoggy at gmail.com> wrote:
> Is there a built-in function that already does this?
> foo :: (a -> b) -> Maybe a -> Maybe b
> foo f m
> | isNothing m = Nothing
> | otherwise = Just (f (fromJust m))
> *Main> foo (+2) (Just 3)
> Just 5
> *Main> foo (+2) Nothing
> If so what is it?
> If not, what should I call it?
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