X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Data%2FSTRef.hs;h=5002ee7fde742a459ae9ff28ca891e15572d46c7;hb=HEAD;hp=01e5cb0fa6728f89ec25881886220942287b4edd;hpb=7f1f4e7a695c402ddd3a1dc2cc7114e649a78ebc;p=ghc-base.git

diff --git a/Data/STRef.hs b/Data/STRef.hs
index 01e5cb0..5002ee7 100644
--- a/Data/STRef.hs
+++ b/Data/STRef.hs
@@ -1,33 +1,43 @@
+{-# LANGUAGE CPP #-}
+
 -----------------------------------------------------------------------------
--- 
+-- |
 -- Module      :  Data.STRef
 -- Copyright   :  (c) The University of Glasgow 2001
--- License     :  BSD-style (see the file libraries/core/LICENSE)
+-- License     :  BSD-style (see the file libraries/base/LICENSE)
 -- 
 -- Maintainer  :  libraries@haskell.org
 -- Stability   :  experimental
--- Portability :  non-portable
---
--- $Id: STRef.hs,v 1.1 2001/06/28 14:15:02 simonmar Exp $
+-- Portability :  non-portable (uses Control.Monad.ST)
 --
--- Mutable references in the ST monad.
+-- Mutable references in the (strict) ST monad.
 --
 -----------------------------------------------------------------------------
 
 module Data.STRef (
-	STRef,		-- abstract, instance Eq
-	newSTRef,	-- :: a -> ST s (STRef s a)
-	readSTRef,	-- :: STRef s a -> ST s a
-	writeSTRef	-- :: STRef s a -> a -> ST s ()
+        -- * STRefs
+        STRef,          -- abstract, instance Eq
+        newSTRef,       -- :: a -> ST s (STRef s a)
+        readSTRef,      -- :: STRef s a -> ST s a
+        writeSTRef,     -- :: STRef s a -> a -> ST s ()
+        modifySTRef     -- :: STRef s a -> (a -> a) -> ST s ()
  ) where
 
 import Prelude
 
 #ifdef __GLASGOW_HASKELL__
+import GHC.ST
 import GHC.STRef
 #endif
 
-import Data.Dynamic
+#ifdef __HUGS__
+import Hugs.ST
+import Data.Typeable
 
-#include "Dynamic.h"
+#include "Typeable.h"
 INSTANCE_TYPEABLE2(STRef,stRefTc,"STRef")
+#endif
+
+-- |Mutate the contents of an 'STRef'
+modifySTRef :: STRef s a -> (a -> a) -> ST s ()
+modifySTRef ref f = writeSTRef ref . f =<< readSTRef ref