[Haskell-cafe] A function for Maybes

[J. Garrett Morris]

fmap.  e.g.:

Prelude> fmap ('c':) (Just "a")
Just "ca"
Prelude> fmap ('c':) Nothing
Nothing
Prelude>

 /g

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
> Nothing
>
> If so what is it?
>
> If not, what should I call it?
>
> Thanks
>
> -John
>
>
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