X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Control%2FMonad%2FST.hs;h=0e3485725e40d34c4a1f141a7ee0686d535d3c27;hb=6d89a2fe861274e66e6fa0a5cdd48b1161b33b75;hp=2a3985ad66147d48def836a1affb8f41f8c53d05;hpb=f7a485978f04e84b086f1974b88887cc72d832d0;p=ghc-base.git

diff --git a/Control/Monad/ST.hs b/Control/Monad/ST.hs
index 2a3985a..0e34857 100644
--- a/Control/Monad/ST.hs
+++ b/Control/Monad/ST.hs
@@ -8,49 +8,56 @@
 -- 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 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
-
-      , unsafeIOToST	    -- :: IO a -> ST s a
-
-      , RealWorld	    -- abstract
-      , stToIO		    -- :: ST RealWorld a -> IO 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
+
+	-- * Unsafe operations
+	unsafeInterleaveST,  	-- :: ST s a -> ST s a
+	unsafeIOToST		-- :: IO a -> ST s a
       ) where
 
 import Prelude
 
 import Control.Monad.Fix
-import Data.Dynamic
 
-#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
+#ifdef __HUGS__
+import Data.Typeable
+import Hugs.ST
+import qualified Hugs.LazyST as LazyST
+
+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))
+
+unsafeInterleaveST :: ST s a -> ST s a
+unsafeInterleaveST =
+    LazyST.lazyToStrictST . LazyST.unsafeInterleaveST . LazyST.strictToLazyST
+#endif
+
+#ifdef __GLASGOW_HASKELL__
+import GHC.ST		( ST, runST, fixST, unsafeInterleaveST )
+import GHC.Base		( RealWorld )
+import GHC.IOBase 	( stToIO, unsafeIOToST )
 #endif
 
 instance MonadFix (ST s) where
 	mfix = fixST
 
--- ---------------------------------------------------------------------------
--- Typeable instance
-
-sTTc :: TyCon
-sTTc = mkTyCon "ST"
-
-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)]