GHC.IORef

Copyright	(c) The University of Glasgow 2008
License	see libraries/base/LICENSE
Maintainer	[email protected]
Stability	internal
Portability	non-portable (GHC Extensions)
Safe Haskell	Unsafe
Language	Haskell2010

newtype IORef a Source

A mutable variable in the IO monad

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

Build a new IORef

readIORef :: IORef a -> IO a Source

Read the value of an IORef

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

Write a new value into an IORef

atomicModifyIORef2Lazy :: IORef a -> (a -> (a, b)) -> IO (a, (a, b)) Source

atomicModifyIORef2 :: IORef a -> (a -> (a, b)) -> IO (a, (a, b)) Source

atomicModifyIORefLazy_ :: IORef a -> (a -> a) -> IO (a, a) Source

Atomically apply a function to the contents of an IORef and return the old and new values. The result of the function is not forced. As this can lead to a memory leak, it is usually better to use atomicModifyIORef'_.

atomicModifyIORef'_ :: IORef a -> (a -> a) -> IO (a, a) Source

Atomically apply a function to the contents of an IORef and return the old and new values. The result of the function is forced.

atomicModifyIORefP :: IORef a -> (a -> (a, b)) -> IO b Source

A version of atomicModifyIORef that forces the (pair) result of the function.

atomicSwapIORef :: IORef a -> a -> IO a Source

Atomically replace the contents of an IORef, returning the old contents.

atomicModifyIORef' :: IORef a -> (a -> (a, b)) -> IO b Source

Strict version of atomicModifyIORef. This forces both the value stored in the IORef and the value returned. The new value is installed in the IORef before the returned value is forced. So

atomicModifyIORef' ref (x -> (x+1, undefined))

will increment the IORef and then throw an exception in the calling thread.

Since: base-4.6.0.0