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|
{-# OPTIONS_GHC -XNoImplicitPrelude -funbox-strict-fields #-}
{-# OPTIONS_HADDOCK hide #-}
-----------------------------------------------------------------------------
-- |
-- Module : GHC.IORef
-- Copyright : (c) The University of Glasgow 2008
-- License : see libraries/base/LICENSE
--
-- Maintainer : cvs-ghc@haskell.org
-- Stability : internal
-- Portability : non-portable (GHC Extensions)
--
-- The IORef type
--
-----------------------------------------------------------------------------
module GHC.IORef (
IORef(..),
newIORef, readIORef, writeIORef, atomicModifyIORef
) where
import GHC.Base
import GHC.STRef
import GHC.IO
-- ---------------------------------------------------------------------------
-- IORefs
-- |A mutable variable in the 'IO' monad
newtype IORef a = IORef (STRef RealWorld a)
-- explicit instance because Haddock can't figure out a derived one
instance Eq (IORef a) where
IORef x == IORef y = x == y
-- |Build a new 'IORef'
newIORef :: a -> IO (IORef a)
newIORef v = stToIO (newSTRef v) >>= \ var -> return (IORef var)
-- |Read the value of an 'IORef'
readIORef :: IORef a -> IO a
readIORef (IORef var) = stToIO (readSTRef var)
-- |Write a new value into an 'IORef'
writeIORef :: IORef a -> a -> IO ()
writeIORef (IORef var) v = stToIO (writeSTRef var v)
atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
atomicModifyIORef (IORef (STRef r#)) f = IO $ \s -> atomicModifyMutVar# r# f s
|
