, MonadFix(..)
, MonadIO(..)
+ , liftIO1, liftIO2, liftIO3, liftIO4
+
+ , zipWith3M
, mapAndUnzipM, mapAndUnzip3M, mapAndUnzip4M
, mapAccumLM
, mapSndM
, concatMapM
- , anyM
+ , mapMaybeM
+ , anyM, allM
, foldlM, foldrM
+ , maybeMapM
) where
----------------------------------------------------------------------------------------
-- Detection of available libraries
----------------------------------------------------------------------------------------
-#define HAVE_APPLICATIVE 1
-- we don't depend on MTL for now
#define HAVE_MTL 0
-- Imports
----------------------------------------------------------------------------------------
-#if HAVE_APPLICATIVE
+import Maybes
+
import Control.Applicative
-#endif
#if HAVE_MTL
import Control.Monad.Trans
#endif
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
+#if !HAVE_MTL
-infixl 4 <$>
-infixl 4 <*>
+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 ([],[],[])
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
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