X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Control%2FMonad%2FST.hs;h=6d19b9c95f323a109744471ffd6dc68f6e3dc55e;hb=9fa9bc17072a58c0bae2cce4764d38677e96ac29;hp=7817add5362cdc80970f5f2c3f73185ef40e2ed7;hpb=77af63d30b55fd40254d0674feff81b01bc85585;p=ghc-base.git

diff --git a/Control/Monad/ST.hs b/Control/Monad/ST.hs
index 7817add..6d19b9c 100644
--- a/Control/Monad/ST.hs
+++ b/Control/Monad/ST.hs
@@ -1,14 +1,14 @@
 -----------------------------------------------------------------------------
--- 
+-- |
 -- Module      :  Control.Monad.ST
 -- Copyright   :  (c) The University of Glasgow 2001
 -- License     :  BSD-style (see the file libraries/core/LICENSE)
 -- 
 -- Maintainer  :  libraries@haskell.org
 -- Stability   :  experimental
--- Portability :  non-portable
+-- Portability :  non-portable (requires universal quantification for runST)
 --
--- $Id: ST.hs,v 1.2 2001/06/29 09:41:37 simonmar Exp $
+-- $Id: ST.hs,v 1.6 2002/04/24 16:31:38 simonmar Exp $
 --
 -- The State Transformer Monad, ST
 --
@@ -29,17 +29,24 @@ module Control.Monad.ST
 
 import Prelude
 
+import Control.Monad.Fix
 import Data.Dynamic
 
 #ifdef __GLASGOW_HASKELL__
 import GHC.ST
-import GHC.Prim		( unsafeCoerce#, RealWorld )
+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
 
+instance MonadFix (ST s) where
+	mfix = fixST
+
 -- ---------------------------------------------------------------------------
 -- Typeable instance