Control.Concurrent.Async.Lifted

This is a wrapped version of Control.Concurrent.Async with types generalized from IO to all monads in either MonadBase or MonadBaseControl.

All the functions restore the monadic effects in the forked computation unless specified otherwise.

If your monad stack satisfies StM m a ~ a (e.g. the reader monad), consider using Control.Concurrent.Async.Lifted.Safe module, which prevents you from messing up monadic effects.

Asynchronous actions

data Async a :: * -> *

An asynchronous action spawned by async or withAsync. Asynchronous actions are executed in a separate thread, and operations are provided for waiting for asynchronous actions to complete and obtaining their results (see e.g. wait).

Instances

Functor Async

Eq (Async a)

Ord (Async a)

Spawning

async :: MonadBaseControl IO m => m a -> m (Async (StM m a))

Generalized version of async.

asyncBound :: MonadBaseControl IO m => m a -> m (Async (StM m a))

Generalized version of asyncBound.

asyncOn :: MonadBaseControl IO m => Int -> m a -> m (Async (StM m a))

Generalized version of asyncOn.

asyncWithUnmask :: MonadBaseControl IO m => ((forall b. m b -> m b) -> m a) -> m (Async (StM m a))

Generalized version of asyncWithUnmask.

asyncOnWithUnmask :: MonadBaseControl IO m => Int -> ((forall b. m b -> m b) -> m a) -> m (Async (StM m a))

Generalized version of asyncOnWithUnmask.

Spawning with automatic cancelation

withAsync :: MonadBaseControl IO m => m a -> (Async (StM m a) -> m b) -> m b

Generalized version of withAsync.

withAsyncBound :: MonadBaseControl IO m => m a -> (Async (StM m a) -> m b) -> m b

Generalized version of withAsyncBound.

withAsyncOn :: MonadBaseControl IO m => Int -> m a -> (Async (StM m a) -> m b) -> m b

Generalized version of withAsyncOn.

withAsyncWithUnmask :: MonadBaseControl IO m => ((forall c. m c -> m c) -> m a) -> (Async (StM m a) -> m b) -> m b

Generalized version of withAsyncWithUnmask.

withAsyncOnWithUnmask :: MonadBaseControl IO m => Int -> ((forall c. m c -> m c) -> m a) -> (Async (StM m a) -> m b) -> m b

Generalized version of withAsyncOnWithUnmask.

Quering Asyncs

wait :: MonadBaseControl IO m => Async (StM m a) -> m a

Generalized version of wait.

poll :: MonadBaseControl IO m => Async (StM m a) -> m (Maybe (Either SomeException a))

Generalized version of poll.

waitCatch :: MonadBaseControl IO m => Async (StM m a) -> m (Either SomeException a)

Generalized version of waitCatch.

cancel :: MonadBase IO m => Async a -> m ()

Generalized version of cancel.

NOTE: This function discards the monadic effects besides IO in the forked computation.

cancelWith :: (MonadBase IO m, Exception e) => Async a -> e -> m ()

Generalized version of cancelWith.

NOTE: This function discards the monadic effects besides IO in the forked computation.

asyncThreadId :: Async a -> ThreadId

Returns the ThreadId of the thread running the given Async.

STM operations

waitSTM :: Async a -> STM a

A version of wait that can be used inside an STM transaction.

pollSTM :: Async a -> STM (Maybe (Either SomeException a))

A version of poll that can be used inside an STM transaction.

waitCatchSTM :: Async a -> STM (Either SomeException a)

A version of waitCatch that can be used inside an STM transaction.

Waiting for multiple Asyncs

waitAny :: MonadBaseControl IO m => [Async (StM m a)] -> m (Async (StM m a), a)

Generalized version of waitAny.

waitAnyCatch :: MonadBaseControl IO m => [Async (StM m a)] -> m (Async (StM m a), Either SomeException a)

Generalized version of waitAnyCatch.

waitAnyCancel :: MonadBaseControl IO m => [Async (StM m a)] -> m (Async (StM m a), a)

Generalized version of waitAnyCancel.

waitAnyCatchCancel :: MonadBaseControl IO m => [Async (StM m a)] -> m (Async (StM m a), Either SomeException a)

Generalized version of waitAnyCatchCancel.

waitEither :: MonadBaseControl IO m => Async (StM m a) -> Async (StM m b) -> m (Either a b)

Generalized version of waitEither.

waitEitherCatch :: MonadBaseControl IO m => Async (StM m a) -> Async (StM m b) -> m (Either (Either SomeException a) (Either SomeException b))

Generalized version of waitEitherCatch.

waitEitherCancel :: MonadBaseControl IO m => Async (StM m a) -> Async (StM m b) -> m (Either a b)

Generalized version of waitEitherCancel.

waitEitherCatchCancel :: MonadBaseControl IO m => Async (StM m a) -> Async (StM m b) -> m (Either (Either SomeException a) (Either SomeException b))

Generalized version of waitEitherCatchCancel.

waitEither_ :: MonadBase IO m => Async a -> Async b -> m ()

Generalized version of waitEither_.

NOTE: This function discards the monadic effects besides IO in the forked computation.

waitBoth :: MonadBaseControl IO m => Async (StM m a) -> Async (StM m b) -> m (a, b)

Generalized version of waitBoth.

Waiting for multiple Asyncs in STM

waitAnySTM :: [Async a] -> STM (Async a, a)

A version of waitAny that can be used inside an STM transaction.

Since: 2.1.0

waitAnyCatchSTM :: [Async a] -> STM (Async a, Either SomeException a)

A version of waitAnyCatch that can be used inside an STM transaction.

Since: 2.1.0

waitEitherSTM :: Async a -> Async b -> STM (Either a b)

A version of waitEither that can be used inside an STM transaction.

Since: 2.1.0

waitEitherCatchSTM :: Async a -> Async b -> STM (Either (Either SomeException a) (Either SomeException b))

A version of waitEitherCatch that can be used inside an STM transaction.

Since: 2.1.0

waitEitherSTM_ :: Async a -> Async b -> STM ()

A version of waitEither_ that can be used inside an STM transaction.

Since: 2.1.0

waitBothSTM :: Async a -> Async b -> STM (a, b)

A version of waitBoth that can be used inside an STM transaction.

Since: 2.1.0

Linking

link :: MonadBase IO m => Async a -> m ()

Generalized version of link.

link2 :: MonadBase IO m => Async a -> Async b -> m ()

Generalized version of link2.

Convenient utilities

race :: MonadBaseControl IO m => m a -> m b -> m (Either a b)

Generalized version of race.

race_ :: MonadBaseControl IO m => m a -> m b -> m ()

Generalized version of race_.

NOTE: This function discards the monadic effects besides IO in the forked computation.

concurrently :: MonadBaseControl IO m => m a -> m b -> m (a, b)

Generalized version of concurrently.

mapConcurrently :: (Traversable t, MonadBaseControl IO m) => (a -> m b) -> t a -> m (t b)

Generalized version of mapConcurrently.

forConcurrently :: (Traversable t, MonadBaseControl IO m) => t a -> (a -> m b) -> m (t b)

Generalized version of forConcurrently.

newtype Concurrently m a

Generalized version of Concurrently.

A value of type Concurrently m a is an IO-based operation that can be composed with other Concurrently values, using the Applicative and Alternative instances.

Calling runConcurrently on a value of type Concurrently m a will execute the IO-based lifted operations it contains concurrently, before delivering the result of type a.

For example

  (page1, page2, page3) <- runConcurrently $ (,,)
    <$> Concurrently (getURL "url1")
    <*> Concurrently (getURL "url2")
    <*> Concurrently (getURL "url3")

Constructors

Concurrently

Fields

runConcurrently :: m a

Instances

Functor m => Functor (Concurrently m)

MonadBaseControl IO m => Applicative (Concurrently m)

MonadBaseControl IO m => Alternative (Concurrently m)

(MonadBaseControl IO m, Monoid a) => Monoid (Concurrently m a)