X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Control%2FMonad%2FST.hs;h=397b07253343f84f0367ffc257e3ee30be861b75;hb=41e8fba828acbae1751628af50849f5352b27873;hp=5ea105224babbd25198d67fa10cbb38cd154f694;hpb=037da109abc1f2fa1b33cf441663039751eaae46;p=ghc-base.git

diff --git a/Control/Monad/ST.hs b/Control/Monad/ST.hs
index 5ea1052..397b072 100644
--- a/Control/Monad/ST.hs
+++ b/Control/Monad/ST.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE CPP #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Monad.ST
@@ -10,36 +12,48 @@
 --
 -- This library provides support for /strict/ state threads, as
 -- described in the PLDI \'94 paper by John Launchbury and Simon Peyton
--- Jones /Lazy State Threads/.
+-- Jones /Lazy Functional State Threads/.
 --
 -----------------------------------------------------------------------------
 
 module Control.Monad.ST
   (
-	-- * The 'ST' Monad
-	ST,		-- abstract, instance of Functor, Monad, Typeable.
-	runST,		-- :: (forall s. ST s a) -> a
-	fixST,		-- :: (a -> ST s a) -> ST s a
+        -- * The 'ST' Monad
+        ST,             -- abstract, instance of Functor, Monad, Typeable.
+        runST,          -- :: (forall s. ST s a) -> a
+        fixST,          -- :: (a -> ST s a) -> ST s a
 
-	-- * Converting 'ST' to 'IO'
-	RealWorld,		-- abstract
-	stToIO,			-- :: ST RealWorld a -> IO a
+        -- * Converting 'ST' to 'IO'
+        RealWorld,              -- abstract
+        stToIO,                 -- :: ST RealWorld a -> IO a
 
-	-- * Unsafe operations
-	unsafeInterleaveST,  	-- :: ST s a -> ST s a
-	unsafeIOToST		-- :: IO a -> ST s a
+        -- * Unsafe operations
+        unsafeInterleaveST,     -- :: ST s a -> ST s a
+        unsafeIOToST,           -- :: IO a -> ST s a
+        unsafeSTToIO            -- :: ST s a -> IO a
       ) where
 
-import Prelude
-
+#if defined(__GLASGOW_HASKELL__)
+import Control.Monad.Fix ()
+#else
 import Control.Monad.Fix
-import Data.Typeable
+#endif
 
 #include "Typeable.h"
 
-#ifdef __HUGS__
+#if defined(__GLASGOW_HASKELL__)
+import GHC.ST           ( ST, runST, fixST, unsafeInterleaveST )
+import GHC.Base         ( RealWorld )
+import GHC.IO           ( stToIO, unsafeIOToST, unsafeSTToIO )
+#elif defined(__HUGS__)
+import Data.Typeable
 import Hugs.ST
 import qualified Hugs.LazyST as LazyST
+#endif
+
+#if defined(__HUGS__)
+INSTANCE_TYPEABLE2(ST,sTTc,"ST")
+INSTANCE_TYPEABLE0(RealWorld,realWorldTc,"RealWorld")
 
 fixST :: (a -> ST s a) -> ST s a
 fixST f = LazyST.lazyToStrictST (LazyST.fixST (LazyST.strictToLazyST . f))
@@ -49,22 +63,8 @@ unsafeInterleaveST =
     LazyST.lazyToStrictST . LazyST.unsafeInterleaveST . LazyST.strictToLazyST
 #endif
 
-#ifdef __GLASGOW_HASKELL__
-import GHC.ST
-import GHC.Base		( unsafeCoerce#, RealWorld )
-import GHC.IOBase 	( IO(..), stToIO )
-
--- This relies on IO and ST having the same representation modulo the
--- constraint on the type of the state
---
-unsafeIOToST        :: IO a -> ST s a
-unsafeIOToST (IO io) = ST $ \ s -> (unsafeCoerce# io) s
-#endif
-
+#if !defined(__GLASGOW_HASKELL__)
 instance MonadFix (ST s) where
-	mfix = fixST
-
--- ---------------------------------------------------------------------------
--- Typeable instance
+        mfix = fixST
+#endif
 
-INSTANCE_TYPEABLE2(ST,sTTc,"ST")