[Haskell-cafe] generic filter through MonadPlus

[Sebastian Fischer]

On May 22, 2009, at 4:13 AM, Jason Dusek wrote:

> I'd like to know what folks think about the use of `MonadPlus` in  
> this case.

The |guard| function is almost |filter|:

 > import Control.Monad ( MonadPlus, guard )
 >
 > filter :: MonadPlus m => (a -> Bool) -> m a -> m a
 > filter p m = do a <- m
 >                 guard (p a)
 >                 return a

Cheers,
Sebastian

-- 
Underestimating the novelty of the future is a time-honored tradition.
(D.G.)



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