On Mon, May 16, 2005 at 03:20:25PM -0400, S. Alexander Jacobson wrote:
> I don't think that is right. concatMap has definition
>
> concatMap :: (a -> [b]) -> [a] -> [b]
> concatMap f xs = concat $ map f xs
>
> Therefore:
>
> msumMap :: (MonadPlus m) => (a1 -> m a) -> [a1] -> m a
> msumMap f list = msum $ fmap f list
>
> In contrast <<= has type
>
> (=<<) :: (Monad m) => (a -> m b) -> m a -> m b
However:
Prelude Control.Monad> concatMap (\i -> [i,i]) [1,2,3]
[1,1,2,2,3,3]
Prelude Control.Monad> (=<<) (\i -> [i,i]) [1,2,3]
[1,1,2,2,3,3]
You could define concatMap as =<<
concatMap :: (a -> [b]) -> [a] -> [b]
concatMap = (=<<)
I guess you don't want it that general.
(=<<) for IO doesn't resemble concatMap.
Best regards
Tomasz
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