X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Control%2FMonad%2FST.hs;h=397b07253343f84f0367ffc257e3ee30be861b75;hb=41e8fba828acbae1751628af50849f5352b27873;hp=2a3985ad66147d48def836a1affb8f41f8c53d05;hpb=f7a485978f04e84b086f1974b88887cc72d832d0;p=ghc-base.git

diff --git a/Control/Monad/ST.hs b/Control/Monad/ST.hs
index 2a3985a..397b072 100644
--- a/Control/Monad/ST.hs
+++ b/Control/Monad/ST.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE CPP #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Monad.ST
@@ -8,49 +10,61 @@
 -- Stability   :  experimental
 -- Portability :  non-portable (requires universal quantification for runST)
 --
--- The State Transformer Monad, ST
+-- This library provides support for /strict/ state threads, as
+-- described in the PLDI \'94 paper by John Launchbury and Simon Peyton
+-- Jones /Lazy Functional State Threads/.
 --
 -----------------------------------------------------------------------------
 
 module Control.Monad.ST
-      (
-	ST                  -- abstract, instance of Functor, Monad, Typeable.
-      , runST		    -- :: (forall s. ST s a) -> a
-      , fixST		    -- :: (a -> ST s a) -> ST s a
-      , unsafeInterleaveST  -- :: 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
 
-      , unsafeIOToST	    -- :: IO a -> ST s a
+        -- * Converting 'ST' to 'IO'
+        RealWorld,              -- abstract
+        stToIO,                 -- :: ST RealWorld a -> IO a
 
-      , RealWorld	    -- abstract
-      , stToIO		    -- :: ST RealWorld a -> IO 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.Dynamic
+#endif
 
-#ifdef __GLASGOW_HASKELL__
-import GHC.ST
-import GHC.Base		( unsafeCoerce#, RealWorld )
-import GHC.IOBase 	( IO(..), stToIO )
+#include "Typeable.h"
 
--- 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
+#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
 
-instance MonadFix (ST s) where
-	mfix = fixST
+#if defined(__HUGS__)
+INSTANCE_TYPEABLE2(ST,sTTc,"ST")
+INSTANCE_TYPEABLE0(RealWorld,realWorldTc,"RealWorld")
 
--- ---------------------------------------------------------------------------
--- Typeable instance
+fixST :: (a -> ST s a) -> ST s a
+fixST f = LazyST.lazyToStrictST (LazyST.fixST (LazyST.strictToLazyST . f))
 
-sTTc :: TyCon
-sTTc = mkTyCon "ST"
+unsafeInterleaveST :: ST s a -> ST s a
+unsafeInterleaveST =
+    LazyST.lazyToStrictST . LazyST.unsafeInterleaveST . LazyST.strictToLazyST
+#endif
+
+#if !defined(__GLASGOW_HASKELL__)
+instance MonadFix (ST s) where
+        mfix = fixST
+#endif
 
-instance (Typeable a, Typeable b) => Typeable (ST a b) where
-  typeOf st = mkAppTy sTTc [typeOf ((undefined :: ST a b -> a) st),
-			    typeOf ((undefined :: ST a b -> b) st)]