X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Futils%2FMonadUtils.hs;h=733eda17005dbac5ba482493241ca368735915d1;hb=01f842b978c903595d4b3184a0761d04a02e5b09;hp=28613a4284c483c46abf7ddc80f2bbc503b0b3e5;hpb=9bcd95bad83ee937c178970e8b729732e680fe1e;p=ghc-hetmet.git

diff --git a/compiler/utils/MonadUtils.hs b/compiler/utils/MonadUtils.hs
index 28613a4..733eda1 100644
--- a/compiler/utils/MonadUtils.hs
+++ b/compiler/utils/MonadUtils.hs
@@ -10,7 +10,8 @@ module MonadUtils
         , MonadIO(..)
         
         , liftIO1, liftIO2, liftIO3, liftIO4
-        
+
+        , zipWith3M        
         , mapAndUnzipM, mapAndUnzip3M, mapAndUnzip4M
         , mapAccumLM
         , mapSndM
@@ -18,17 +19,13 @@ module MonadUtils
         , mapMaybeM
         , anyM, allM
         , 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
 
@@ -38,9 +35,7 @@ module MonadUtils
 
 import Maybes
 
-#if HAVE_APPLICATIVE
 import Control.Applicative
-#endif
 #if HAVE_MTL
 import Control.Monad.Trans
 #endif
@@ -48,28 +43,6 @@ import Control.Monad
 import Control.Monad.Fix
 
 ----------------------------------------------------------------------------------------
--- Applicative
-----------------------------------------------------------------------------------------
-
-#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 <*>
-
-instance Applicative IO where
-	pure = return
-	(<*>) = ap
-
-#endif
-
-----------------------------------------------------------------------------------------
 -- MTL
 ----------------------------------------------------------------------------------------
 
@@ -107,6 +80,16 @@ liftIO4 = (((.).(.)).((.).(.))) liftIO
 --  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 ([],[],[])
@@ -166,4 +149,9 @@ 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 }
\ No newline at end of file
+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