[project @ 2002-10-09 17:08:18 by malcolm]
[packages/base.git] / Data / IORef.hs
1 -----------------------------------------------------------------------------
2 -- |
3 -- Module : Data.IORef
4 -- Copyright : (c) The University of Glasgow 2001
5 -- License : BSD-style (see the file libraries/base/LICENSE)
6 --
7 -- Maintainer : libraries@haskell.org
8 -- Stability : experimental
9 -- Portability : portable
10 --
11 -- Mutable references in the IO monad.
12 --
13 -----------------------------------------------------------------------------
14
15 module Data.IORef
16 (
17 -- * IORefs
18 IORef, -- abstract, instance of: Eq, Typeable
19 newIORef, -- :: a -> IO (IORef a)
20 readIORef, -- :: IORef a -> IO a
21 writeIORef, -- :: IORef a -> a -> IO ()
22 modifyIORef, -- :: IORef a -> (a -> a) -> IO ()
23
24 #if !defined(__PARALLEL_HASKELL__) && defined(__GLASGOW_HASKELL__)
25 mkWeakIORef, -- :: IORef a -> IO () -> IO (Weak (IORef a))
26 #endif
27 ) where
28
29 import Prelude
30
31 #ifdef __HUGS__
32 import Hugs.IORef
33 #endif
34
35 #ifdef __GLASGOW_HASKELL__
36 import GHC.Base ( mkWeak# )
37 import GHC.STRef
38 import GHC.IOBase
39 #if !defined(__PARALLEL_HASKELL__)
40 import GHC.Weak
41 #endif
42 #endif /* __GLASGOW_HASKELL__ */
43
44 #ifdef __NHC__
45 import NHC.IOExtras
46 ( IORef
47 , newIORef
48 , readIORef
49 , writeIORef
50 )
51 #endif
52
53 #ifndef __NHC__
54 import Data.Dynamic
55 #endif
56
57 #if defined(__GLASGOW_HASKELL__) && !defined(__PARALLEL_HASKELL__)
58 -- |Make a 'Weak' pointer to an 'IORef'
59 mkWeakIORef :: IORef a -> IO () -> IO (Weak (IORef a))
60 mkWeakIORef r@(IORef (STRef r#)) f = IO $ \s ->
61 case mkWeak# r# r f s of (# s1, w #) -> (# s1, Weak w #)
62 #endif
63
64 -- |Mutate the contents of an 'IORef'
65 modifyIORef :: IORef a -> (a -> a) -> IO ()
66 modifyIORef ref f = writeIORef ref . f =<< readIORef ref
67
68 #ifndef __NHC__
69 #include "Dynamic.h"
70 INSTANCE_TYPEABLE1(IORef,ioRefTc,"IORef")
71 #endif