GHC.IORef

The IORef type

Documentation

newtype IORef a

A mutable variable in the IO monad

Constructors

IORef (STRef RealWorld a)

Instances

Eq (IORef a)

Pointer equality.

Since: base-4.0.0.0

Defined in GHC.IORef

Methods

(==) :: IORef a -> IORef a -> Bool

(/=) :: IORef a -> IORef a -> Bool

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

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

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

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

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)

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

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

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

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

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

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