blob: 851a20f9fc3c343cf3e318e89efa6bc93ad7fecb (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
|
{-# LANGUAGE Trustworthy #-}
{-# LANGUAGE CPP #-}
-----------------------------------------------------------------------------
-- |
-- Module : Data.STRef
-- Copyright : (c) The University of Glasgow 2001
-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : libraries@haskell.org
-- Stability : experimental
-- Portability : non-portable (uses Control.Monad.ST)
--
-- 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
writeSTRef, -- :: STRef s a -> a -> ST s ()
modifySTRef -- :: STRef s a -> (a -> a) -> ST s ()
) where
import Prelude
#ifdef __GLASGOW_HASKELL__
import GHC.ST
import GHC.STRef
#endif
#ifdef __HUGS__
import Hugs.ST
import Data.Typeable
#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
|
