Data.MRef.Instances

This module exports no new symbols of its own. It defines basic class instances for creating, reading, and writing MVars, and re-exports MVar.

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

Eq (MVar a)

DefaultMRef (MVar a) IO a

MonadIO m => PutMRef (MVar a) m a

MonadIO m => TakeMRef (MVar a) m a

MonadIO m => NewMRef (MVar a) m a

MonadIO m => NewRef (MVar a) m (Maybe a)

class Monad m => MonadIO m where

Methods

liftIO :: IO a -> m a

Instances

MonadIO IO

data STM a

A monad supporting atomic memory transactions.

Instances

Monad STM

Functor STM

Typeable1 STM

MonadPlus STM

DefaultMRef (TMVar a) STM a

PutMRef (TVar (Maybe a)) STM a

PutMRef (TMVar a) STM a

TakeMRef (TVar (Maybe a)) STM a

TakeMRef (TMVar a) STM a

NewMRef (TVar (Maybe a)) STM a

NewMRef (TMVar a) STM a

DefaultStateRef (TVar a) STM a

ModifyRef (TVar a) STM a

MonadIO m => ReadRef (STM a) m a

ReadRef (STM a) STM a

ReadRef (TVar a) STM a

WriteRef (TVar a) STM a

NewRef (TVar a) STM a

ReadRef (TMVar a) STM (Maybe a)

NewRef (TMVar a) STM (Maybe a)

data TMVar a

A TMVar is a synchronising variable, used for communication between concurrent threads. It can be thought of as a box, which may be empty or full.

Instances

Typeable1 TMVar

Eq (TMVar a)

DefaultMRef (TMVar a) STM a

PutMRef (TMVar a) IO a

PutMRef (TMVar a) STM a

TakeMRef (TMVar a) IO a

TakeMRef (TMVar a) STM a

NewMRef (TMVar a) IO a

NewMRef (TMVar a) STM a

MonadIO m => ReadRef (TMVar a) m (Maybe a)

ReadRef (TMVar a) STM (Maybe a)

MonadIO m => NewRef (TMVar a) m (Maybe a)

NewRef (TMVar a) STM (Maybe a)

data TVar a

Shared memory locations that support atomic memory transactions.

Instances

Typeable1 TVar

Eq (TVar a)

PutMRef (TVar (Maybe a)) IO a

PutMRef (TVar (Maybe a)) STM a

TakeMRef (TVar (Maybe a)) IO a

TakeMRef (TVar (Maybe a)) STM a

NewMRef (TVar (Maybe a)) IO a

NewMRef (TVar (Maybe a)) STM a

DefaultStateRef (TVar a) STM a

MonadIO m => ModifyRef (TVar a) m a

ModifyRef (TVar a) STM a

MonadIO m => ReadRef (TVar a) m a

ReadRef (TVar a) STM a

MonadIO m => WriteRef (TVar a) m a

WriteRef (TVar a) STM a

MonadIO m => NewRef (TVar a) m a

NewRef (TVar a) STM a

atomically :: STM a -> IO a

Perform a series of STM actions atomically.

You cannot use atomically inside an unsafePerformIO or unsafeInterleaveIO. Any attempt to do so will result in a runtime error. (Reason: allowing this would effectively allow a transaction inside a transaction, depending on exactly when the thunk is evaluated.)

However, see newTVarIO, which can be called inside unsafePerformIO, and which allows top-level TVars to be allocated.