Control.Monad.MVar

Lift MVar operations so you can do them within monads stacked on top of IO. Analogous to MonadIO

Documentation

data MVar a

An MVar (pronounced "em-var") is a synchronising variable, used for communication between concurrent threads. It can be thought of as a a box, which may be empty or full.

Instances

Typeable1 MVar

Eq (MVar a)

newEmptyMVar :: MonadIO m => m (MVar a)

newMVar :: MonadIO m => a -> m (MVar a)

takeMVar :: MonadIO m => MVar a -> m a

putMVar :: MonadIO m => MVar a -> a -> m ()

readMVar :: MonadIO m => MVar a -> m a

swapMVar :: MonadIO m => MVar a -> a -> m a

tryTakeMVar :: MonadIO m => MVar a -> m (Maybe a)

tryPutMVar :: MonadIO m => MVar a -> a -> m Bool

isEmptyMVar :: MonadIO m => MVar a -> m Bool

class MonadIO m => MonadMVar m where

Methods

modifyMVar :: MVar a -> (a -> m (a, b)) -> m b

addMVarFinalizer :: MVar a -> m () -> m ()

Instances

MonadMVar IO

(MonadMVar m, Error e) => MonadMVar (ErrorT e m)

MonadMVar m => MonadMVar (ReaderT r m)

MonadMVar m => MonadMVar (StateT s m)

modifyMVar_ :: MonadMVar m => MVar a -> (a -> m a) -> m ()

withMVar :: MonadMVar m => MVar a -> (a -> m b) -> m b

liftIO :: MonadIO m => forall a. IO a -> m a

Lift a computation from the IO monad.