[project @ 2003-05-12 08:48:09 by ross]

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

diff --git a/Data/STRef.hs b/Data/STRef.hs
index e25e8b5..a48e29a 100644 (file)
--- a/Data/STRef.hs
+++ b/Data/STRef.hs
@@ -24,6 +24,7 @@ module Data.STRef (
 import Prelude
 
 #ifdef __GLASGOW_HASKELL__
+import GHC.ST
 import GHC.STRef
 #endif
 
@@ -35,3 +36,7 @@ import Data.Dynamic
 
 #include "Dynamic.h"
 INSTANCE_TYPEABLE2(STRef,stRefTc,"STRef")
+
+-- |Mutate the contents of an 'STRef'
+modifySTRef :: STRef s a -> (a -> a) -> ST s ()
+modifySTRef ref f = writeSTRef ref . f =<< readSTRef ref