Haskell Code by HsColour

{-# OPTIONS_GHC -fno-warn-orphans #-}
-----------------------------------------------------------------------------
-- |
-- Module : Control.Monad.ST
-- Copyright : (c) The University of Glasgow 2001
-- License : BSD-style (see the file libraries/base/LICENSE)
-- 
-- Maintainer : libraries@haskell.org
-- Stability : experimental
-- Portability : non-portable (requires universal quantification for runST)
--
-- 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
 (
 -- * 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
 unsafeSTToIO -- :: ST s a -> IO a
 ) where

import Prelude

import Control.Monad.Fix

#include "Typeable.h"

#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, unsafeSTToIO )
#endif

instance MonadFix (ST s) where
 mfix = fixST