G'day all.
Quoting [EMAIL PROTECTED]:
> Until then, this is what I use.
Second time lucky.
Cheers,
Andrew Bromage
-----------------------------------------------------------------------------
-- |
-- Module : Data.IOStableRef
-- Copyright : (c) Andrew Bromage 2002
-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : [EMAIL PROTECTED]
-- Stability : experimental
-- Portability : portable
--
-- Mutable references in the IO monad, with stable orderings.
--
-----------------------------------------------------------------------------
module Data.IOStableRef
(
IOStableRef, -- abstract, instance of: Eq, Ord, Typeable
newIOStableRef, -- :: a -> IO (IOStableRef a)
readIOStableRef, -- :: IOStableRef a -> IO a
writeIOStableRef, -- :: IOStableRef a -> a -> IO ()
modifyIOStableRef, -- :: IOStableRef a -> (a -> a) -> IO ()
hashIOStableRef, -- :: IOStableRef a -> Int
) where
import Prelude
import Data.IORef
import Data.Unique
data IOStableRef a
= IOStableRef !Unique !(IORef a)
instance Eq (IOStableRef a) where
IOStableRef u1 _ == IOStableRef u2 _ = u1 == u2
instance Ord (IOStableRef a) where
IOStableRef u1 _ < IOStableRef u2 _ = u1 < u2
IOStableRef u1 _ <= IOStableRef u2 _ = u1 <= u2
IOStableRef u1 _ > IOStableRef u2 _ = u1 > u2
IOStableRef u1 _ >= IOStableRef u2 _ = u1 >= u2
compare (IOStableRef u1 _) (IOStableRef u2 _) = compare u1 u2
hashIOStableRef :: IOStableRef a -> Int
hashIOStableRef (IOStableRef u _)
= hashUnique u
newIOStableRef :: a -> IO (IOStableRef a)
newIOStableRef x
= newUnique >>= \u -> newIORef x >>= \r -> return (IOStableRef u r)
readIOStableRef :: IOStableRef a -> IO a
readIOStableRef (IOStableRef _ r)
= readIORef r
writeIOStableRef :: IOStableRef a -> a -> IO ()
writeIOStableRef (IOStableRef _ r)
= writeIORef r
modifyIOStableRef :: IOStableRef a -> (a -> a) -> IO ()
modifyIOStableRef (IOStableRef _ r) f
= modifyIORef r f
#include "Dynamic.h"
INSTANCE_TYPEABLE1(IOStableRef,ioStableRefTc,"IOStableRef")
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