base-4.3.0.0: Basic libraries

Portabilityportable
Stabilityexperimental
Maintainerlibraries@haskell.org

Data.IORef

Contents

Description

Mutable references in the IO monad.

Synopsis

IORefs

data IORef a Source

A mutable variable in the IO monad

Instances

newIORef :: a -> IO (IORef a)Source

Build a new IORef

readIORef :: IORef a -> IO aSource

Read the value of an IORef

writeIORef :: IORef a -> a -> IO ()Source

Write a new value into an IORef

modifyIORef :: IORef a -> (a -> a) -> IO ()Source

Mutate the contents of an IORef

atomicModifyIORef :: IORef a -> (a -> (a, b)) -> IO bSource

Atomically modifies the contents of an IORef.

This function is useful for using IORef in a safe way in a multithreaded program. If you only have one IORef, then using atomicModifyIORef to access and modify it will prevent race conditions.

Extending the atomicity to multiple IORefs is problematic, so it is recommended that if you need to do anything more complicated then using Control.Concurrent.MVar.MVar instead is a good idea.

mkWeakIORef :: IORef a -> IO () -> IO (Weak (IORef a))Source

Make a Weak pointer to an IORef