strict-io-0.2.1: A library wrapping standard IO modules to provide strict IO.

MaintainerNicolas Pouillard <>
Safe HaskellSafe-Infered



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.



data IORef a

A mutable variable in the IO monad


Eq (IORef a) 

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

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

readIORef :: IORef a -> SIO aSource

Read the value of an IORef

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

Deeply force a value and write it into an IORef

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

Mutate the contents of an IORef

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

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.

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

Make a Weak pointer to an IORef