, concatMapM
, mapMaybeM
, anyM, allM
- , foldlM, foldrM
+ , foldlM, foldlM_, foldrM
+ , maybeMapM
) where
----------------------------------------------------------------------------------------
foldlM :: (Monad m) => (a -> b -> m a) -> a -> [b] -> m a
foldlM = foldM
+-- | Monadic version of foldl that discards its result
+foldlM_ :: (Monad m) => (a -> b -> m a) -> a -> [b] -> m ()
+foldlM_ = foldM_
+
-- | Monadic version of foldr
foldrM :: (Monad m) => (b -> a -> m a) -> a -> [b] -> m a
foldrM _ z [] = return z
foldrM k z (x:xs) = do { r <- foldrM k z xs; k x r }
+
+-- | Monadic version of fmap specialised for Maybe
+maybeMapM :: Monad m => (a -> m b) -> (Maybe a -> m (Maybe b))
+maybeMapM _ Nothing = return Nothing
+maybeMapM m (Just x) = liftM Just $ m x