base-3.0.2.0: Basic librariesSource codeContentsIndex
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 aSource
A mutable variable in the IO monad
show/hide 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 MVar instead is a good idea.

mkWeakIORef :: IORef a -> IO () -> IO (Weak (IORef a))Source
Make a Weak pointer to an IORef
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