From 0fafbcb0fa66573de86c23855db77437d0ffebe8 Mon Sep 17 00:00:00 2001
From: sof <unknown>
Date: Mon, 20 Sep 1999 10:22:40 +0000
Subject: [PATCH] [project @ 1999-09-20 10:22:40 by sof] Added 'updateIORef ::
IORef a -> (a->a) -> IO ()'
---
ghc/lib/exts/IOExts.lhs | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/ghc/lib/exts/IOExts.lhs b/ghc/lib/exts/IOExts.lhs
index a0de1cc21240..0ee5a505b7ef 100644
--- a/ghc/lib/exts/IOExts.lhs
+++ b/ghc/lib/exts/IOExts.lhs
@@ -22,6 +22,7 @@ module IOExts
, newIORef
, readIORef
, writeIORef
+ , updateIORef
, mkWeakIORef
@@ -106,9 +107,9 @@ unsafePtrEq a b =
\end{code}
\begin{code}
-newIORef :: a -> IO (IORef a)
-readIORef :: IORef a -> IO a
-writeIORef :: IORef a -> a -> IO ()
+newIORef :: a -> IO (IORef a)
+readIORef :: IORef a -> IO a
+writeIORef :: IORef a -> a -> IO ()
#ifdef __HUGS__
type IORef a = STRef RealWorld a
@@ -124,6 +125,13 @@ readIORef (IORef var) = stToIO (readVar var)
writeIORef (IORef var) v = stToIO (writeVar var v)
#endif
+updateIORef :: IORef a -> (a -> a) -> IO ()
+updateIORef ref f = do
+ x <- readIORef ref
+ let x' = f x
+ writeIORef ref x'
+ -- or should we return new value ? (or old?)
+
mkWeakIORef :: IORef a -> IO () -> IO (Weak (IORef a))
mkWeakIORef r@(IORef (MutableVar r#)) f = IO $ \s ->
case mkWeak# r# r f s of (# s1, w #) -> (# s1, Weak w #)
--
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