+++ /dev/null
--- (c) The University of Glasgow 2002
---
--- The IO Monad with an environment
---
-
-module IOEnv (
- 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_,
-
- -- Getting at the environment
- getEnv, setEnv, updEnv,
-
- runIOEnv, unsafeInterleaveM,
- tryM, tryAllM, fixM,
-
- -- I/O operations
- ioToIOEnv,
- IORef, newMutVar, readMutVar, writeMutVar, updMutVar
- ) where
-#include "HsVersions.h"
-
-import Panic ( try, tryUser, Exception(..) )
-import DATA_IOREF ( IORef, newIORef, readIORef, writeIORef )
-import UNSAFE_IO ( unsafeInterleaveIO )
-import FIX_IO ( fixIO )
-
-
-----------------------------------------------------------------------
--- Defining the monad type
-----------------------------------------------------------------------
-
-
-newtype IOEnv env a = IOEnv (env -> IO a)
-unIOEnv (IOEnv m) = m
-
-instance Monad (IOEnv m) where
- (>>=) = thenM
- (>>) = thenM_
- return = returnM
- fail s = failM -- Ignore the string
-
-returnM :: a -> IOEnv env a
-returnM a = IOEnv (\ env -> 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 })
-
-thenM_ :: IOEnv env a -> IOEnv env b -> IOEnv env b
-thenM_ (IOEnv m) f = IOEnv (\ env -> do { m env ; unIOEnv f env })
-
-failM :: IOEnv env a
-failM = IOEnv (\ env -> ioError (userError "IOEnv failure"))
-
-failWithM :: String -> IOEnv env a
-failWithM s = IOEnv (\ env -> ioError (userError s))
-
-
-
-----------------------------------------------------------------------
--- Fundmantal combinators specific to the monad
-----------------------------------------------------------------------
-
-
----------------------------
-runIOEnv :: env -> IOEnv env a -> IO a
-runIOEnv env (IOEnv m) = m env
-
-
----------------------------
-{-# NOINLINE fixM #-}
- -- Aargh! Not inlining fixTc alleviates a space leak problem.
- -- Normally fixTc is used with a lazy tuple match: if the optimiser is
- -- shown the definition of fixTc, it occasionally transforms the code
- -- in such a way that the code generator doesn't spot the selector
- -- thunks. Sigh.
-
-fixM :: (a -> IOEnv env a) -> IOEnv env a
-fixM f = IOEnv (\ env -> fixIO (\ r -> unIOEnv (f r) env))
-
-
----------------------------
-tryM :: IOEnv env r -> IOEnv env (Either Exception r)
--- Reflect UserError exceptions into IOEnv monad
--- 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
--- begin compiled!
-tryM (IOEnv thing) = IOEnv (\ env -> tryUser (thing env))
-
-tryAllM :: IOEnv env r -> IOEnv env (Either Exception 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))
-
----------------------------
-unsafeInterleaveM :: IOEnv env a -> IOEnv env a
-unsafeInterleaveM (IOEnv m) = IOEnv (\ env -> unsafeInterleaveIO (m env))
-
-
-----------------------------------------------------------------------
--- Accessing input/output
-----------------------------------------------------------------------
-
-ioToIOEnv :: IO a -> IOEnv env a
-ioToIOEnv io = IOEnv (\ env -> io)
-
-newMutVar :: a -> IOEnv env (IORef a)
-newMutVar val = IOEnv (\ env -> newIORef val)
-
-writeMutVar :: IORef a -> a -> IOEnv env ()
-writeMutVar var val = IOEnv (\ env -> writeIORef var val)
-
-readMutVar :: IORef a -> IOEnv env a
-readMutVar var = IOEnv (\ env -> readIORef var)
-
-updMutVar :: IORef a -> (a->a) -> IOEnv env ()
-updMutVar var upd_fn = IOEnv (\ env -> do { v <- readIORef var; writeIORef var (upd_fn v) })
-
-
-----------------------------------------------------------------------
--- Accessing the environment
-----------------------------------------------------------------------
-
-getEnv :: IOEnv env env
-{-# INLINE getEnv #-}
-getEnv = IOEnv (\ env -> return env)
-
-setEnv :: env' -> IOEnv env' a -> IOEnv env a
-{-# INLINE setEnv #-}
-setEnv new_env (IOEnv m) = IOEnv (\ env -> m new_env)
-
-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)
-----------------------------------------------------------------------
-
-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 ()
projects / ghc-hetmet.git / blobdiff