Use braces rather than angle-brackets in debug-printing for Bags

[ghc-hetmet.git] / compiler / utils / MonadUtils.hs

diff --git a/compiler/utils/MonadUtils.hs b/compiler/utils/MonadUtils.hs
index 2064657..9b364ae 100644 (file)
--- a/compiler/utils/MonadUtils.hs
+++ b/compiler/utils/MonadUtils.hs
@@ -18,7 +18,8 @@ module MonadUtils
         , concatMapM
         , mapMaybeM
         , anyM, allM
-        , foldlM, foldrM
+        , foldlM, foldlM_, foldrM
+        , maybeMapM
         ) where
 
 ----------------------------------------------------------------------------------------
@@ -145,7 +146,16 @@ allM f (b:bs) = (f b) >>= (\bv -> if bv then allM f bs else return False)
 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