Commit a5b8386a authored by simonpj@microsoft.com's avatar simonpj@microsoft.com
Browse files

Add fmapMaybeM and fmapEitherM

parent 12da626e
......@@ -19,6 +19,7 @@ module MonadUtils
, mapSndM
, concatMapM
, mapMaybeM
, fmapMaybeM, fmapEitherM
, anyM, allM
, foldlM, foldlM_, foldrM
, maybeMapM
......@@ -148,6 +149,16 @@ concatMapM f xs = liftM concat (mapM f xs)
mapMaybeM :: (Monad m) => (a -> m (Maybe b)) -> [a] -> m [b]
mapMaybeM f = liftM catMaybes . mapM f
-- | Monadic version of fmap
fmapMaybeM :: (Monad m) => (a -> m b) -> Maybe a -> m (Maybe b)
fmapMaybeM _ Nothing = return Nothing
fmapMaybeM f (Just x) = f x >>= (return . Just)
-- | Monadic version of fmap
fmapEitherM :: Monad m => (a -> m b) -> (c -> m d) -> Either a c -> m (Either b d)
fmapEitherM fl _ (Left a) = fl a >>= (return . Left)
fmapEitherM _ fr (Right b) = fr b >>= (return . Right)
-- | Monadic version of 'any', aborts the computation at the first @True@ value
anyM :: Monad m => (a -> m Bool) -> [a] -> m Bool
anyM _ [] = return False
......
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