X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Futils%2FMonadUtils.hs;h=9b364aebb7901d8cd289e5cec7c400edb825f7bc;hp=b1882c349fc5ada3bc96d0acc30a9154205494f6;hb=4fa44a3ae9c36222ccb460ba3ed24e46bf7c70ae;hpb=e4fa0854318cde1a317727ab3d29edc0ca772e9d

diff --git a/compiler/utils/MonadUtils.hs b/compiler/utils/MonadUtils.hs
index b1882c3..9b364ae 100644
--- a/compiler/utils/MonadUtils.hs
+++ b/compiler/utils/MonadUtils.hs
@@ -9,23 +9,23 @@ module MonadUtils
         , MonadFix(..)
         , MonadIO(..)
         
+        , liftIO1, liftIO2, liftIO3, liftIO4
+
+        , zipWith3M        
         , mapAndUnzipM, mapAndUnzip3M, mapAndUnzip4M
         , mapAccumLM
         , mapSndM
         , concatMapM
-        , anyM
-        , foldlM, foldrM
+        , mapMaybeM
+        , anyM, allM
+        , foldlM, foldlM_, foldrM
+        , maybeMapM
         ) where
 
 ----------------------------------------------------------------------------------------
 -- 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 +33,9 @@ module MonadUtils
 -- Imports
 ----------------------------------------------------------------------------------------
 
-#if HAVE_APPLICATIVE
+import Maybes
+
 import Control.Applicative
-#endif
 #if HAVE_MTL
 import Control.Monad.Trans
 #endif
@@ -43,43 +43,53 @@ 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
 
-#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
 ----------------------------------------------------------------------------------------
 
+zipWith3M :: Monad m => (a -> b -> c -> m d) -> [a] -> [b] -> [c] -> m [d]
+zipWith3M _ []     _      _      = return []
+zipWith3M _ _      []     _      = return []
+zipWith3M _ _      _      []     = return []
+zipWith3M f (x:xs) (y:ys) (z:zs) 
+  = do { r  <- f x y z
+       ; rs <- zipWith3M f xs ys zs
+       ; return $ r:rs
+       }
+
 -- | mapAndUnzipM for triples
 mapAndUnzip3M :: Monad m => (a -> m (b,c,d)) -> [a] -> m ([b],[c],[d])
 mapAndUnzip3M _ []     = return ([],[],[])
@@ -116,18 +126,36 @@ 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 'any', aborts the computation at the first False value
+-- | 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
 anyM f (x:xs) = do b <- f x
                    if b then return True 
                         else anyM f xs
 
+-- | Monad version of 'all', aborts the computation at the first @False@ value
+allM :: Monad m => (a -> m Bool) -> [a] -> m Bool
+allM _ []     = return True
+allM f (b:bs) = (f b) >>= (\bv -> if bv then allM f bs else return False)
+
 -- | Monadic version of foldl
 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