FunctorM

[Graham Klyne]

I think this would be a good idea.  I find it's both simple and useful.  I 
use a module [1] almost identical to this for accumulating values from an 
RDF graph.  I also have fmapM_ defined.

#g
--

[1] http://www.ninebynine.org/Software/HaskellUtils/FunctorM.hs


At 17:11 27/05/04 -0700, John Meacham wrote:
>Pretty simple, and quite useful. perhaps it could be added as
>Control.FunctorM ?
>
>just as Functor generalises 'map', FunctorM generalises 'mapM'.
>
>there are probably some instances I missed. note that unlike Functor, an
>instance for IO cannot be written for FunctorM.
>
>module FunctorM where
>
>import Array
>
>class FunctorM f where
>     fmapM :: Monad m => (a -> m b) -> f a -> m (f b)
>
>
>instance FunctorM [] where
>     fmapM f xs = mapM f xs
>
>instance FunctorM Maybe where
>     fmapM _ Nothing = return Nothing
>     fmapM f (Just x) = f x >>= return . Just
>
>instance Ix i => FunctorM (Array i) where
>     fmapM f a = sequence [ f e >>= return . (,) i | (i,e) <- assocs 
> a] >>= return . array b  where
>         b = bounds a
>
>
>
>--
>John Meacham - ⑆repetae.net⑆john⑈
>_______________________________________________
>Libraries mailing list
>Libraries at haskell.org
>http://www.haskell.org/mailman/listinfo/libraries

------------
Graham Klyne
For email:
http://www.ninebynine.org/#Contact