DrIFT-cabalized-2.2.3.1: code/FunctorM.hs

module FunctorM where

import Array (array, assocs, bounds, Array(), Ix())

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