Data.IORef.Strict

Mutable references of strict values in the SIO monad.

The type of references remains the same as in the IO monad and is just re-exported here.

Documentation

data IORef a :: * -> *

A mutable variable in the IO monad

Instances

Eq (IORef a)

Methods

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

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

NFData (IORef a)

NOTE: Only strict in the reference and not the referenced value.

Since: 1.4.2.0

Methods

rnf :: IORef a -> ()

newIORef :: NFData sa => sa -> SIO (IORef sa)

Build a new IORef, but deeply force the value before storing it.

readIORef :: IORef a -> SIO a

Read the value of an IORef

writeIORef :: NFData sa => IORef sa -> sa -> SIO ()

Deeply force a value and write it into an IORef

modifyIORef :: NFData sa => IORef sa -> (sa -> sa) -> SIO ()

Mutate the contents of an IORef

atomicModifyIORef :: (NFData sa, NFData sb) => IORef sa -> (sa -> (sa, sb)) -> SIO sb

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.

Internally this function is using Data.IORef.atomicModifyIORef'.

mkWeakIORef :: IORef a -> SIO () -> SIO (Weak (IORef a))

Make a Weak pointer to an IORef