--
-- The IO Monad with an environment
--
+{-# LANGUAGE UndecidableInstances #-}
module IOEnv (
- IOEnv, -- Instance of Monad
+ IOEnv, -- Instance of Monad
- -- Standard combinators, specialised
- returnM, thenM, thenM_, failM, failWithM,
- mappM, mappM_, mapSndM, sequenceM, sequenceM_,
- foldlM, foldrM,
- mapAndUnzipM, mapAndUnzip3M,
- checkM, ifM, zipWithM, zipWithM_,
+ -- Monad utilities
+ module MonadUtils,
- -- Getting at the environment
- getEnv, setEnv, updEnv,
+ -- Errors
+ failM, failWithM,
+ IOEnvFailure(..),
- runIOEnv, unsafeInterleaveM,
- tryM, tryAllM, tryMostM, fixM,
+ -- Getting at the environment
+ getEnv, setEnv, updEnv,
- -- I/O operations
- ioToIOEnv,
- IORef, newMutVar, readMutVar, writeMutVar, updMutVar
- ) where
-#include "HsVersions.h"
+ runIOEnv, unsafeInterleaveM,
+ tryM, tryAllM, tryMostM, fixM,
-import Panic ( try, tryUser, tryMost, Exception(..) )
+ -- I/O operations
+ IORef, newMutVar, readMutVar, writeMutVar, updMutVar,
+ atomicUpdMutVar, atomicUpdMutVar'
+ ) where
-import Data.IORef ( IORef, newIORef, readIORef, writeIORef )
-import System.IO.Unsafe ( unsafeInterleaveIO )
-import System.IO ( fixIO )
+import Exception
+import Panic
+import Data.IORef ( IORef, newIORef, readIORef, writeIORef, modifyIORef,
+ atomicModifyIORef )
+import Data.Typeable
+import System.IO.Unsafe ( unsafeInterleaveIO )
+import System.IO ( fixIO )
+import Control.Monad
+import MonadUtils
----------------------------------------------------------------------
--- Defining the monad type
+-- Defining the monad type
----------------------------------------------------------------------
newtype IOEnv env a = IOEnv (env -> IO a)
+
+unIOEnv :: IOEnv env a -> (env -> IO a)
unIOEnv (IOEnv m) = m
instance Monad (IOEnv m) where
- (>>=) = thenM
- (>>) = thenM_
- return = returnM
- fail s = failM -- Ignore the string
+ (>>=) = thenM
+ (>>) = thenM_
+ return = returnM
+ fail _ = failM -- Ignore the string
+
+instance Applicative (IOEnv m) where
+ pure = returnM
+ IOEnv f <*> IOEnv x = IOEnv (\ env -> f env <*> x env )
+
+instance Functor (IOEnv m) where
+ fmap f (IOEnv m) = IOEnv (\ env -> fmap f (m env))
returnM :: a -> IOEnv env a
-returnM a = IOEnv (\ env -> return a)
+returnM a = IOEnv (\ _ -> return a)
thenM :: IOEnv env a -> (a -> IOEnv env b) -> IOEnv env b
thenM (IOEnv m) f = IOEnv (\ env -> do { r <- m env ;
- unIOEnv (f r) env })
+ unIOEnv (f r) env })
thenM_ :: IOEnv env a -> IOEnv env b -> IOEnv env b
-thenM_ (IOEnv m) f = IOEnv (\ env -> do { m env ; unIOEnv f env })
+thenM_ (IOEnv m) f = IOEnv (\ env -> do { _ <- m env ; unIOEnv f env })
failM :: IOEnv env a
-failM = IOEnv (\ env -> ioError (userError "IOEnv failure"))
+failM = IOEnv (\ _ -> throwIO IOEnvFailure)
failWithM :: String -> IOEnv env a
-failWithM s = IOEnv (\ env -> ioError (userError s))
+failWithM s = IOEnv (\ _ -> ioError (userError s))
+
+data IOEnvFailure = IOEnvFailure
+ deriving Typeable
+instance Show IOEnvFailure where
+ show IOEnvFailure = "IOEnv failure"
+instance Exception IOEnvFailure
----------------------------------------------------------------------
--- Fundmantal combinators specific to the monad
+-- Fundmantal combinators specific to the monad
----------------------------------------------------------------------
---------------------------
-tryM :: IOEnv env r -> IOEnv env (Either Exception r)
--- Reflect UserError exceptions into IOEnv monad
+tryM :: IOEnv env r -> IOEnv env (Either IOEnvFailure r)
+-- Reflect UserError exceptions (only) into IOEnv monad
+-- Other exceptions are not caught; they are simply propagated as exns
+--
-- The idea is that errors in the program being compiled will give rise
-- to UserErrors. But, say, pattern-match failures in GHC itself should
--- not be caught here, else they'll be reported as errors in the program
+-- not be caught here, else they'll be reported as errors in the program
-- begin compiled!
-tryM (IOEnv thing) = IOEnv (\ env -> tryUser (thing env))
+tryM (IOEnv thing) = IOEnv (\ env -> tryIOEnvFailure (thing env))
-tryAllM :: IOEnv env r -> IOEnv env (Either Exception r)
+tryIOEnvFailure :: IO a -> IO (Either IOEnvFailure a)
+tryIOEnvFailure = try
+
+-- XXX We shouldn't be catching everything, e.g. timeouts
+tryAllM :: IOEnv env r -> IOEnv env (Either SomeException r)
-- Catch *all* exceptions
-- This is used when running a Template-Haskell splice, when
-- even a pattern-match failure is a programmer error
tryAllM (IOEnv thing) = IOEnv (\ env -> try (thing env))
-tryMostM :: IOEnv env r -> IOEnv env (Either Exception r)
+tryMostM :: IOEnv env r -> IOEnv env (Either SomeException r)
tryMostM (IOEnv thing) = IOEnv (\ env -> tryMost (thing env))
---------------------------
----------------------------------------------------------------------
--- Accessing input/output
+-- MonadPlus
+----------------------------------------------------------------------
+
+-- For use if the user has imported Control.Monad.Error from MTL
+-- Requires UndecidableInstances
+instance MonadPlus IO => MonadPlus (IOEnv env) where
+ mzero = IOEnv (const mzero)
+ m `mplus` n = IOEnv (\env -> unIOEnv m env `mplus` unIOEnv n env)
+
+----------------------------------------------------------------------
+-- Accessing input/output
----------------------------------------------------------------------
-ioToIOEnv :: IO a -> IOEnv env a
-ioToIOEnv io = IOEnv (\ env -> io)
+instance MonadIO (IOEnv env) where
+ liftIO io = IOEnv (\ _ -> io)
newMutVar :: a -> IOEnv env (IORef a)
-newMutVar val = IOEnv (\ env -> newIORef val)
+newMutVar val = liftIO (newIORef val)
writeMutVar :: IORef a -> a -> IOEnv env ()
-writeMutVar var val = IOEnv (\ env -> writeIORef var val)
+writeMutVar var val = liftIO (writeIORef var val)
readMutVar :: IORef a -> IOEnv env a
-readMutVar var = IOEnv (\ env -> readIORef var)
+readMutVar var = liftIO (readIORef var)
+
+updMutVar :: IORef a -> (a -> a) -> IOEnv env ()
+updMutVar var upd = liftIO (modifyIORef var upd)
-updMutVar :: IORef a -> (a->a) -> IOEnv env ()
-updMutVar var upd_fn = IOEnv (\ env -> do { v <- readIORef var; writeIORef var (upd_fn v) })
+-- | Atomically update the reference. Does not force the evaluation of the
+-- new variable contents. For strict update, use 'atomicUpdMutVar''.
+atomicUpdMutVar :: IORef a -> (a -> (a, b)) -> IOEnv env b
+atomicUpdMutVar var upd = liftIO (atomicModifyIORef var upd)
+-- | Strict variant of 'atomicUpdMutVar'.
+atomicUpdMutVar' :: IORef a -> (a -> (a, b)) -> IOEnv env b
+atomicUpdMutVar' var upd = do
+ r <- atomicUpdMutVar var upd
+ _ <- liftIO . evaluate =<< readMutVar var
+ return r
----------------------------------------------------------------------
--- Accessing the environment
+-- Accessing the environment
----------------------------------------------------------------------
getEnv :: IOEnv env env
{-# INLINE getEnv #-}
getEnv = IOEnv (\ env -> return env)
+-- | Perform a computation with a different environment
setEnv :: env' -> IOEnv env' a -> IOEnv env a
{-# INLINE setEnv #-}
-setEnv new_env (IOEnv m) = IOEnv (\ env -> m new_env)
+setEnv new_env (IOEnv m) = IOEnv (\ _ -> m new_env)
+-- | Perform a computation with an altered environment
updEnv :: (env -> env') -> IOEnv env' a -> IOEnv env a
{-# INLINE updEnv #-}
updEnv upd (IOEnv m) = IOEnv (\ env -> m (upd env))
----------------------------------------------------------------------
--- Standard combinators, but specialised for this monad
--- (for efficiency)
+-- Standard combinators, but specialised for this monad
+-- (for efficiency)
----------------------------------------------------------------------
-mappM :: (a -> IOEnv env b) -> [a] -> IOEnv env [b]
-mappM_ :: (a -> IOEnv env b) -> [a] -> IOEnv env ()
-mapSndM :: (b -> IOEnv env c) -> [(a,b)] -> IOEnv env [(a,c)]
- -- Funny names to avoid clash with Prelude
-sequenceM :: [IOEnv env a] -> IOEnv env [a]
-sequenceM_ :: [IOEnv env a] -> IOEnv env ()
-foldlM :: (a -> b -> IOEnv env a) -> a -> [b] -> IOEnv env a
-foldrM :: (b -> a -> IOEnv env a) -> a -> [b] -> IOEnv env a
-mapAndUnzipM :: (a -> IOEnv env (b,c)) -> [a] -> IOEnv env ([b],[c])
-mapAndUnzip3M :: (a -> IOEnv env (b,c,d)) -> [a] -> IOEnv env ([b],[c],[d])
-checkM :: Bool -> IOEnv env a -> IOEnv env () -- Perform arg if bool is False
-ifM :: Bool -> IOEnv env a -> IOEnv env () -- Perform arg if bool is True
-
-mappM f [] = return []
-mappM f (x:xs) = do { r <- f x; rs <- mappM f xs; return (r:rs) }
-
-mapSndM f [] = return []
-mapSndM f ((a,b):xs) = do { c <- f b; rs <- mapSndM f xs; return ((a,c):rs) }
-
-mappM_ f [] = return ()
-mappM_ f (x:xs) = f x >> mappM_ f xs
-
-zipWithM :: (a -> b -> IOEnv env c) -> [a] -> [b] -> IOEnv env [c]
-zipWithM f [] bs = return []
-zipWithM f as [] = return []
-zipWithM f (a:as) (b:bs) = do { r <- f a b; rs <- zipWithM f as bs; return (r:rs) }
-
-zipWithM_ :: (a -> b -> IOEnv env c) -> [a] -> [b] -> IOEnv env ()
-zipWithM_ f [] bs = return ()
-zipWithM_ f as [] = return ()
-zipWithM_ f (a:as) (b:bs) = do { f a b; zipWithM_ f as bs }
-
-sequenceM [] = return []
-sequenceM (x:xs) = do { r <- x; rs <- sequenceM xs; return (r:rs) }
-
-sequenceM_ [] = return ()
-sequenceM_ (x:xs) = do { x; sequenceM_ xs }
-
-foldlM k z [] = return z
-foldlM k z (x:xs) = do { r <- k z x; foldlM k r xs }
-
-foldrM k z [] = return z
-foldrM k z (x:xs) = do { r <- foldrM k z xs; k x r }
-
-mapAndUnzipM f [] = return ([],[])
-mapAndUnzipM f (x:xs) = do { (r,s) <- f x;
- (rs,ss) <- mapAndUnzipM f xs;
- return (r:rs, s:ss) }
-
-mapAndUnzip3M f [] = return ([],[], [])
-mapAndUnzip3M f (x:xs) = do { (r,s,t) <- f x;
- (rs,ss,ts) <- mapAndUnzip3M f xs;
- return (r:rs, s:ss, t:ts) }
-
-checkM True err = return ()
-checkM False err = do { err; return () }
-
-ifM True do_it = do { do_it; return () }
-ifM False do_it = return ()
+-- {-# SPECIALIZE mapM :: (a -> IOEnv env b) -> [a] -> IOEnv env [b] #-}
+-- {-# SPECIALIZE mapM_ :: (a -> IOEnv env b) -> [a] -> IOEnv env () #-}
+-- {-# SPECIALIZE mapSndM :: (b -> IOEnv env c) -> [(a,b)] -> IOEnv env [(a,c)] #-}
+-- {-# SPECIALIZE sequence :: [IOEnv env a] -> IOEnv env [a] #-}
+-- {-# SPECIALIZE sequence_ :: [IOEnv env a] -> IOEnv env () #-}
+-- {-# SPECIALIZE foldlM :: (a -> b -> IOEnv env a) -> a -> [b] -> IOEnv env a #-}
+-- {-# SPECIALIZE foldrM :: (b -> a -> IOEnv env a) -> a -> [b] -> IOEnv env a #-}
+-- {-# SPECIALIZE mapAndUnzipM :: (a -> IOEnv env (b,c)) -> [a] -> IOEnv env ([b],[c]) #-}
+-- {-# SPECIALIZE mapAndUnzip3M :: (a -> IOEnv env (b,c,d)) -> [a] -> IOEnv env ([b],[c],[d]) #-}
+-- {-# SPECIALIZE zipWithM :: (a -> b -> IOEnv env c) -> [a] -> [b] -> IOEnv env [c] #-}
+-- {-# SPECIALIZE zipWithM_ :: (a -> b -> IOEnv env c) -> [a] -> [b] -> IOEnv env () #-}
+-- {-# SPECIALIZE anyM :: (a -> IOEnv env Bool) -> [a] -> IOEnv env Bool #-}
+-- {-# SPECIALIZE when :: Bool -> IOEnv env a -> IOEnv env () #-}
+-- {-# SPECIALIZE unless :: Bool -> IOEnv env a -> IOEnv env () #-}
projects / ghc-hetmet.git / blobdiff