Use explicit language extensions & remove extension fields from base.cabal

[ghc-base.git] / Control / Monad / ST.hs

diff --git a/Control/Monad/ST.hs b/Control/Monad/ST.hs
index 705787e..397b072 100644 (file)
--- a/Control/Monad/ST.hs
+++ b/Control/Monad/ST.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE CPP #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Monad.ST
@@ -10,34 +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
 
-#ifdef __HUGS__
+#include "Typeable.h"
+
+#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))
@@ -47,27 +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
-
-sTTc :: TyCon
-sTTc = mkTyCon "ST"
+        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)]