Haskell Hierarchical Libraries (base package)ContentsIndex
Data.IORef
Portabilityportable
Stabilityexperimental
Maintainerlibraries@haskell.org
Contents
IORefs
Description
Mutable references in the IO monad.
Synopsis
data IORef a
newIORef :: a -> IO (IORef a)
readIORef :: IORef a -> IO a
writeIORef :: IORef a -> a -> IO ()
modifyIORef :: IORef a -> (a -> a) -> IO ()
atomicModifyIORef :: IORef a -> (a -> (a, b)) -> IO b
mkWeakIORef :: IORef a -> IO () -> IO (Weak (IORef a))
IORefs
data IORef a
A mutable variable in the IO monad
show/hide Instances
newIORef :: a -> IO (IORef a)
Build a new IORef
readIORef :: IORef a -> IO a
Read the value of an IORef
writeIORef :: IORef a -> a -> IO ()
Write a new value into an IORef
modifyIORef :: IORef a -> (a -> a) -> IO ()
Mutate the contents of an IORef
atomicModifyIORef :: IORef a -> (a -> (a, b)) -> IO b

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 MVar instead is a good idea.

mkWeakIORef :: IORef a -> IO () -> IO (Weak (IORef a))
Make a Weak pointer to an IORef
Produced by Haddock version 0.7