[Haskell-cafe] A function for Maybes

Brandon S. Allbery KF8NH allbery at ece.cmu.edu
Thu Jan 25 09:22:49 EST 2007

On Jan 25, 2007, at 9:15 , John Ky 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))

Nothing specific to Maybe, because the more general liftM (over  
monads) or fmap (over functors) already does it.

brandon s. allbery    [linux,solaris,freebsd,perl]     allbery at kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery at ece.cmu.edu
electrical and computer engineering, carnegie mellon university    KF8NH

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