add final newlines

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

diff --git a/compiler/utils/MonadUtils.hs b/compiler/utils/MonadUtils.hs
index 85d8642..4ddd4ea 100644 (file)
--- a/compiler/utils/MonadUtils.hs
+++ b/compiler/utils/MonadUtils.hs
@@ -9,10 +9,13 @@ module MonadUtils
         , MonadFix(..)
         , MonadIO(..)
         
+        , liftIO1, liftIO2, liftIO3, liftIO4
+        
         , mapAndUnzipM, mapAndUnzip3M, mapAndUnzip4M
         , mapAccumLM
         , mapSndM
         , concatMapM
+        , mapMaybeM
         , anyM, allM
         , foldlM, foldrM
         ) where
@@ -21,11 +24,6 @@ module MonadUtils
 -- Detection of available libraries
 ----------------------------------------------------------------------------------------
 
-#if __GLASGOW_HASKELL__ >= 606
-#define HAVE_APPLICATIVE 1
-#else
-#define HAVE_APPLICATIVE 0
-#endif
 -- we don't depend on MTL for now
 #define HAVE_MTL 0
 
@@ -33,9 +31,9 @@ module MonadUtils
 -- Imports
 ----------------------------------------------------------------------------------------
 
-#if HAVE_APPLICATIVE
+import Maybes
+
 import Control.Applicative
-#endif
 #if HAVE_MTL
 import Control.Monad.Trans
 #endif
@@ -43,42 +41,41 @@ import Control.Monad
 import Control.Monad.Fix
 
 ----------------------------------------------------------------------------------------
--- Applicative
+-- MTL
 ----------------------------------------------------------------------------------------
 
-#if !HAVE_APPLICATIVE
-
-class Functor f => Applicative f where
-    pure  :: a -> f a
-    (<*>) :: f (a -> b) -> f a -> f b
-
-(<$>) :: Functor f => (a -> b) -> (f a -> f b)
-(<$>) = fmap
-
-infixl 4 <$>
-infixl 4 <*>
+#if !HAVE_MTL
 
-instance Applicative IO where
-       pure = return
-       (<*>) = ap
+class Monad m => MonadIO m where
+    liftIO :: IO a -> m a
 
+instance MonadIO IO where liftIO = id
 #endif
 
 ----------------------------------------------------------------------------------------
--- MTL
+-- Lift combinators
+--  These are used throughout the compiler
 ----------------------------------------------------------------------------------------
 
-#if !HAVE_MTL
+-- | Lift an 'IO' operation with 1 argument into another monad
+liftIO1 :: MonadIO m => (a -> IO b) -> a -> m b
+liftIO1 = (.) liftIO
 
-class Monad m => MonadIO m where
-    liftIO :: IO a -> m a
+-- | Lift an 'IO' operation with 2 arguments into another monad
+liftIO2 :: MonadIO m => (a -> b -> IO c) -> a -> b -> m c
+liftIO2 = ((.).(.)) liftIO
 
-instance MonadIO IO where liftIO = id
-#endif
+-- | Lift an 'IO' operation with 3 arguments into another monad
+liftIO3 :: MonadIO m => (a -> b -> c -> IO d) -> a -> b -> c -> m d
+liftIO3 = ((.).((.).(.))) liftIO
+
+-- | Lift an 'IO' operation with 4 arguments into another monad
+liftIO4 :: MonadIO m => (a -> b -> c -> d -> IO e) -> a -> b -> c -> d -> m e
+liftIO4 = (((.).(.)).((.).(.))) liftIO
 
 ----------------------------------------------------------------------------------------
 -- Common functions
---  These are used throught the compiler
+--  These are used throughout the compiler
 ----------------------------------------------------------------------------------------
 
 -- | mapAndUnzipM for triples
@@ -117,6 +114,10 @@ mapSndM f ((a,b):xs) = do { c <- f b; rs <- mapSndM f xs; return ((a,c):rs) }
 concatMapM :: Monad m => (a -> m [b]) -> [a] -> m [b]
 concatMapM f xs = liftM concat (mapM f xs)
 
+-- | Monadic version of mapMaybe
+mapMaybeM :: (Monad m) => (a -> m (Maybe b)) -> [a] -> m [b]
+mapMaybeM f = liftM catMaybes . mapM f
+
 -- | Monadic version of 'any', aborts the computation at the first @True@ value
 anyM :: Monad m => (a -> m Bool) -> [a] -> m Bool
 anyM _ []     = return False