[project @ 2005-02-18 15:06:45 by simonmar]

[ghc-base.git] / Data / STRef.hs

diff --git a/Data/STRef.hs b/Data/STRef.hs
index 2331ef9..b185493 100644 (file)
--- a/Data/STRef.hs
+++ b/Data/STRef.hs
@@ -8,11 +8,12 @@
 -- Stability   :  experimental
 -- Portability :  non-portable (requires non-portable module ST)
 --
--- Mutable references in the ST monad.
+-- Mutable references in the (strict) ST monad.
 --
 -----------------------------------------------------------------------------
 
 module Data.STRef (
+       -- * STRefs
        STRef,          -- abstract, instance Eq
        newSTRef,       -- :: a -> ST s (STRef s a)
        readSTRef,      -- :: STRef s a -> ST s a
@@ -23,10 +24,18 @@ module Data.STRef (
 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