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Language  Haskell2010 
Unlifted Control.Concurrent.Async.
Since: 0.1.0.0
Synopsis
 data Async a
 async :: MonadUnliftIO m => m a > m (Async a)
 asyncBound :: MonadUnliftIO m => m a > m (Async a)
 asyncOn :: MonadUnliftIO m => Int > m a > m (Async a)
 asyncWithUnmask :: MonadUnliftIO m => ((forall b. m b > m b) > m a) > m (Async a)
 asyncOnWithUnmask :: MonadUnliftIO m => Int > ((forall b. m b > m b) > m a) > m (Async a)
 withAsync :: MonadUnliftIO m => m a > (Async a > m b) > m b
 withAsyncBound :: MonadUnliftIO m => m a > (Async a > m b) > m b
 withAsyncOn :: MonadUnliftIO m => Int > m a > (Async a > m b) > m b
 withAsyncWithUnmask :: MonadUnliftIO m => ((forall c. m c > m c) > m a) > (Async a > m b) > m b
 withAsyncOnWithUnmask :: MonadUnliftIO m => Int > ((forall c. m c > m c) > m a) > (Async a > m b) > m b
 wait :: MonadIO m => Async a > m a
 poll :: MonadIO m => Async a > m (Maybe (Either SomeException a))
 waitCatch :: MonadIO m => Async a > m (Either SomeException a)
 cancel :: MonadIO m => Async a > m ()
 uninterruptibleCancel :: MonadIO m => Async a > m ()
 cancelWith :: (Exception e, MonadIO m) => Async a > e > m ()
 asyncThreadId :: Async a > ThreadId
 waitSTM :: Async a > STM a
 pollSTM :: Async a > STM (Maybe (Either SomeException a))
 waitCatchSTM :: Async a > STM (Either SomeException a)
 waitAny :: MonadIO m => [Async a] > m (Async a, a)
 waitAnyCatch :: MonadIO m => [Async a] > m (Async a, Either SomeException a)
 waitAnyCancel :: MonadIO m => [Async a] > m (Async a, a)
 waitAnyCatchCancel :: MonadIO m => [Async a] > m (Async a, Either SomeException a)
 waitEither :: MonadIO m => Async a > Async b > m (Either a b)
 waitEitherCatch :: MonadIO m => Async a > Async b > m (Either (Either SomeException a) (Either SomeException b))
 waitEitherCancel :: MonadIO m => Async a > Async b > m (Either a b)
 waitEitherCatchCancel :: MonadIO m => Async a > Async b > m (Either (Either SomeException a) (Either SomeException b))
 waitEither_ :: MonadIO m => Async a > Async b > m ()
 waitBoth :: MonadIO m => Async a > Async b > m (a, b)
 waitAnySTM :: [Async a] > STM (Async a, a)
 waitAnyCatchSTM :: [Async a] > STM (Async a, Either SomeException a)
 waitEitherSTM :: Async a > Async b > STM (Either a b)
 waitEitherCatchSTM :: Async a > Async b > STM (Either (Either SomeException a) (Either SomeException b))
 waitEitherSTM_ :: Async a > Async b > STM ()
 waitBothSTM :: Async a > Async b > STM (a, b)
 link :: MonadIO m => Async a > m ()
 link2 :: MonadIO m => Async a > Async b > m ()
 pooledMapConcurrentlyN :: (MonadUnliftIO m, Traversable t) => Int > (a > m b) > t a > m (t b)
 pooledMapConcurrently :: (MonadUnliftIO m, Traversable t) => (a > m b) > t a > m (t b)
 pooledMapConcurrentlyN_ :: (MonadUnliftIO m, Foldable f) => Int > (a > m b) > f a > m ()
 pooledMapConcurrently_ :: (MonadUnliftIO m, Foldable f) => (a > m b) > f a > m ()
 pooledForConcurrentlyN :: (MonadUnliftIO m, Traversable t) => Int > t a > (a > m b) > m (t b)
 pooledForConcurrently :: (MonadUnliftIO m, Traversable t) => t a > (a > m b) > m (t b)
 pooledForConcurrentlyN_ :: (MonadUnliftIO m, Foldable t) => Int > t a > (a > m b) > m ()
 pooledForConcurrently_ :: (MonadUnliftIO m, Foldable f) => f a > (a > m b) > m ()
 pooledReplicateConcurrentlyN :: MonadUnliftIO m => Int > Int > m a > m [a]
 pooledReplicateConcurrently :: MonadUnliftIO m => Int > m a > m [a]
 pooledReplicateConcurrentlyN_ :: MonadUnliftIO m => Int > Int > m a > m ()
 pooledReplicateConcurrently_ :: MonadUnliftIO m => Int > m a > m ()
 race :: MonadUnliftIO m => m a > m b > m (Either a b)
 race_ :: MonadUnliftIO m => m a > m b > m ()
 concurrently :: MonadUnliftIO m => m a > m b > m (a, b)
 concurrently_ :: MonadUnliftIO m => m a > m b > m ()
 mapConcurrently :: MonadUnliftIO m => Traversable t => (a > m b) > t a > m (t b)
 forConcurrently :: MonadUnliftIO m => Traversable t => t a > (a > m b) > m (t b)
 mapConcurrently_ :: MonadUnliftIO m => Foldable f => (a > m b) > f a > m ()
 forConcurrently_ :: MonadUnliftIO m => Foldable f => f a > (a > m b) > m ()
 replicateConcurrently :: MonadUnliftIO f => Int > f a > f [a]
 replicateConcurrently_ :: (Applicative m, MonadUnliftIO m) => Int > m a > m ()
 newtype Concurrently m a = Concurrently {
 runConcurrently :: m a
 data Conc m a
 conc :: m a > Conc m a
 runConc :: MonadUnliftIO m => Conc m a > m a
 data ConcException = EmptyWithNoAlternative
 data AsyncCancelled = AsyncCancelled
Asynchronous actions
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
).
Spawning
asyncBound :: MonadUnliftIO m => m a > m (Async a) Source #
Unlifted asyncBound
.
Since: 0.1.0.0
asyncWithUnmask :: MonadUnliftIO m => ((forall b. m b > m b) > m a) > m (Async a) Source #
Unlifted asyncWithUnmask
.
Since: 0.1.0.0
asyncOnWithUnmask :: MonadUnliftIO m => Int > ((forall b. m b > m b) > m a) > m (Async a) Source #
Unlifted asyncOnWithUnmask
.
Since: 0.1.0.0
Spawning with automatic cancel
ation
withAsync :: MonadUnliftIO m => m a > (Async a > m b) > m b Source #
Unlifted withAsync
.
Since: 0.1.0.0
withAsyncBound :: MonadUnliftIO m => m a > (Async a > m b) > m b Source #
Unlifted withAsyncBound
.
Since: 0.1.0.0
withAsyncOn :: MonadUnliftIO m => Int > m a > (Async a > m b) > m b Source #
Unlifted withAsyncOn
.
Since: 0.1.0.0
withAsyncWithUnmask :: MonadUnliftIO m => ((forall c. m c > m c) > m a) > (Async a > m b) > m b Source #
Unlifted withAsyncWithUnmask
.
Since: 0.1.0.0
withAsyncOnWithUnmask :: MonadUnliftIO m => Int > ((forall c. m c > m c) > m a) > (Async a > m b) > m b Source #
Unlifted withAsyncOnWithMask
.
Since: 0.1.0.0
Querying Async
s
poll :: MonadIO m => Async a > m (Maybe (Either SomeException a)) Source #
Lifted poll
.
Since: 0.1.0.0
waitCatch :: MonadIO m => Async a > m (Either SomeException a) Source #
Lifted waitCatch
.
Since: 0.1.0.0
uninterruptibleCancel :: MonadIO m => Async a > m () Source #
Lifted uninterruptibleCancel
.
Since: 0.1.0.0
cancelWith :: (Exception e, MonadIO m) => Async a > e > m () Source #
Lifted cancelWith
. Additionally uses toAsyncException
to
ensure async exception safety.
Since: 0.1.0.0
STM operations
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 Async
s
waitAnyCatch :: MonadIO m => [Async a] > m (Async a, Either SomeException a) Source #
Lifted waitAnyCatch
.
Since: 0.1.0.0
waitAnyCancel :: MonadIO m => [Async a] > m (Async a, a) Source #
Lifted waitAnyCancel
.
Since: 0.1.0.0
waitAnyCatchCancel :: MonadIO m => [Async a] > m (Async a, Either SomeException a) Source #
Lifted waitAnyCatchCancel
.
Since: 0.1.0.0
waitEither :: MonadIO m => Async a > Async b > m (Either a b) Source #
Lifted waitEither
.
Since: 0.1.0.0
waitEitherCatch :: MonadIO m => Async a > Async b > m (Either (Either SomeException a) (Either SomeException b)) Source #
Lifted waitEitherCatch
.
Since: 0.1.0.0
waitEitherCancel :: MonadIO m => Async a > Async b > m (Either a b) Source #
Lifted waitEitherCancel
.
Since: 0.1.0.0
waitEitherCatchCancel :: MonadIO m => Async a > Async b > m (Either (Either SomeException a) (Either SomeException b)) Source #
Lifted waitEitherCatchCancel
.
Since: 0.1.0.0
waitEither_ :: MonadIO m => Async a > Async b > m () Source #
Lifted waitEither_
.
Since: 0.1.0.0
Waiting for multiple Async
s in STM
waitAnySTM :: [Async a] > STM (Async a, a) #
A version of waitAny
that can be used inside an STM transaction.
Since: async2.1.0
waitAnyCatchSTM :: [Async a] > STM (Async a, Either SomeException a) #
A version of waitAnyCatch
that can be used inside an STM transaction.
Since: async2.1.0
waitEitherSTM :: Async a > Async b > STM (Either a b) #
A version of waitEither
that can be used inside an STM transaction.
Since: async2.1.0
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: async2.1.0
waitEitherSTM_ :: Async a > Async b > STM () #
A version of waitEither_
that can be used inside an STM transaction.
Since: async2.1.0
waitBothSTM :: Async a > Async b > STM (a, b) #
A version of waitBoth
that can be used inside an STM transaction.
Since: async2.1.0
Linking
Pooled concurrency
pooledMapConcurrentlyN Source #
:: (MonadUnliftIO m, Traversable t)  
=> Int  Max. number of threads. Should not be less than 1. 
> (a > m b)  
> t a  
> m (t b) 
Like mapConcurrently
from async, but instead of one thread per
element, it does pooling from a set of threads. This is useful in
scenarios where resource consumption is bounded and for use cases
where too many concurrent tasks aren't allowed.
Example usage
import Say action :: Int > IO Int action n = do tid < myThreadId sayString $ show tid threadDelay (2 * 10^6)  2 seconds return n main :: IO () main = do yx < pooledMapConcurrentlyN 5 (\x > action x) [1..5] print yx
On executing you can see that five threads have been spawned:
$ ./pool ThreadId 36 ThreadId 38 ThreadId 40 ThreadId 42 ThreadId 44 [1,2,3,4,5]
Let's modify the above program such that there are less threads than the number of items in the list:
import Say action :: Int > IO Int action n = do tid < myThreadId sayString $ show tid threadDelay (2 * 10^6)  2 seconds return n main :: IO () main = do yx < pooledMapConcurrentlyN 3 (\x > action x) [1..5] print yx
On executing you can see that only three threads are active totally:
$ ./pool ThreadId 35 ThreadId 37 ThreadId 39 ThreadId 35 ThreadId 39 [1,2,3,4,5]
Since: 0.2.10
pooledMapConcurrently :: (MonadUnliftIO m, Traversable t) => (a > m b) > t a > m (t b) Source #
Similar to pooledMapConcurrentlyN
but with number of threads
set from getNumCapabilities
. Usually this is useful for CPU bound
tasks.
Since: 0.2.10
pooledMapConcurrentlyN_ Source #
:: (MonadUnliftIO m, Foldable f)  
=> Int  Max. number of threads. Should not be less than 1. 
> (a > m b)  
> f a  
> m () 
Like pooledMapConcurrentlyN
but with the return value
discarded.
Since: 0.2.10
pooledMapConcurrently_ :: (MonadUnliftIO m, Foldable f) => (a > m b) > f a > m () Source #
Like pooledMapConcurrently
but with the return value discarded.
Since: 0.2.10
pooledForConcurrentlyN Source #
:: (MonadUnliftIO m, Traversable t)  
=> Int  Max. number of threads. Should not be less than 1. 
> t a  
> (a > m b)  
> m (t b) 
Similar to pooledMapConcurrentlyN
but with flipped arguments.
Since: 0.2.10
pooledForConcurrently :: (MonadUnliftIO m, Traversable t) => t a > (a > m b) > m (t b) Source #
Similar to pooledForConcurrentlyN
but with number of threads
set from getNumCapabilities
. Usually this is useful for CPU bound
tasks.
Since: 0.2.10
pooledForConcurrentlyN_ Source #
:: (MonadUnliftIO m, Foldable t)  
=> Int  Max. number of threads. Should not be less than 1. 
> t a  
> (a > m b)  
> m () 
Like pooledMapConcurrentlyN_
but with flipped arguments.
Since: 0.2.10
pooledForConcurrently_ :: (MonadUnliftIO m, Foldable f) => f a > (a > m b) > m () Source #
Like pooledMapConcurrently_
but with flipped arguments.
Since: 0.2.10
pooledReplicateConcurrentlyN Source #
:: MonadUnliftIO m  
=> Int  Max. number of threads. Should not be less than 1. 
> Int  Number of times to perform the action. 
> m a  
> m [a] 
Pooled version of replicateConcurrently
. Performs the action in
the pooled threads.
Since: 0.2.10
pooledReplicateConcurrently Source #
:: MonadUnliftIO m  
=> Int  Number of times to perform the action. 
> m a  
> m [a] 
Similar to pooledReplicateConcurrentlyN
but with number of
threads set from getNumCapabilities
. Usually this is useful for
CPU bound tasks.
Since: 0.2.10
pooledReplicateConcurrentlyN_ Source #
:: MonadUnliftIO m  
=> Int  Max. number of threads. Should not be less than 1. 
> Int  Number of times to perform the action. 
> m a  
> m () 
Pooled version of replicateConcurrently_
. Performs the action in
the pooled threads.
Since: 0.2.10
pooledReplicateConcurrently_ Source #
:: MonadUnliftIO m  
=> Int  Number of times to perform the action. 
> m a  
> m () 
Similar to pooledReplicateConcurrently_
but with number of
threads set from getNumCapabilities
. Usually this is useful for
CPU bound tasks.
Since: 0.2.10
Convenient utilities
race_ :: MonadUnliftIO m => m a > m b > m () Source #
Unlifted race_
.
Since: 0.1.0.0
concurrently :: MonadUnliftIO m => m a > m b > m (a, b) Source #
Unlifted concurrently
.
Since: 0.1.0.0
concurrently_ :: MonadUnliftIO m => m a > m b > m () Source #
Unlifted concurrently_
.
Since: 0.1.0.0
mapConcurrently :: MonadUnliftIO m => Traversable t => (a > m b) > t a > m (t b) Source #
Executes a Traversable
container of items concurrently, it uses the Flat
type internally.
Since: 0.1.0.0
forConcurrently :: MonadUnliftIO m => Traversable t => t a > (a > m b) > m (t b) Source #
Similar to mapConcurrently
but with arguments flipped
Since: 0.1.0.0
mapConcurrently_ :: MonadUnliftIO m => Foldable f => (a > m b) > f a > m () Source #
Executes a Traversable
container of items concurrently, it uses the Flat
type internally. This function ignores the results.
Since: 0.1.0.0
forConcurrently_ :: MonadUnliftIO m => Foldable f => f a > (a > m b) > m () Source #
Similar to mapConcurrently_
but with arguments flipped
Since: 0.1.0.0
replicateConcurrently :: MonadUnliftIO f => Int > f a > f [a] Source #
Unlifted replicateConcurrently
.
Since: 0.1.0.0
replicateConcurrently_ :: (Applicative m, MonadUnliftIO m) => Int > m a > m () Source #
Unlifted replicateConcurrently_
.
Since: 0.1.0.0
newtype Concurrently m a Source #
Unlifted Concurrently
.
Since: 0.1.0.0
Concurrently  

Instances
A more efficient alternative to Concurrently
, which reduces the
number of threads that need to be forked. For more information, see
this blog post.
This is provided as a separate type to Concurrently
as it has a slightly different API.
Use the conc
function to construct values of type Conc
, and
runConc
to execute the composed actions. You can use the
Applicative
instance to run different actions and wait for all of
them to complete, or the Alternative
instance to wait for the
first thread to complete.
In the event of a runtime exception thrown by any of the children
threads, or an asynchronous exception received in the parent
thread, all threads will be killed with an AsyncCancelled
exception and the original exception rethrown. If multiple
exceptions are generated by different threads, there are no
guarantees on which exception will end up getting rethrown.
For many common use cases, you may prefer using helper functions in
this module like mapConcurrently
.
There are some intentional differences in behavior to
Concurrently
:
 Children threads are always launched in an unmasked state, not the inherited state of the parent thread.
Note that it is a programmer error to use the Alternative
instance in such a way that there are no alternatives to an empty,
e.g. runConc (empty  empty)
. In such a case, a ConcException
will be thrown. If there was an Alternative
in the standard
libraries without empty
, this library would use it instead.
Since: 0.2.9.0
Instances
MonadUnliftIO m => Alternative (Conc m) Source #  Since: 0.2.9.0 
MonadUnliftIO m => Applicative (Conc m) Source #  Since: 0.2.9.0 
Functor m => Functor (Conc m) Source #  
(Monoid a, MonadUnliftIO m) => Monoid (Conc m a) Source #  Since: 0.2.9.0 
(MonadUnliftIO m, Semigroup a) => Semigroup (Conc m a) Source #  Since: 0.2.9.0 
conc :: m a > Conc m a Source #
Construct a value of type Conc
from an action. Compose these
values using the typeclass instances (most commonly Applicative
and Alternative
) and then run with runConc
.
Since: 0.2.9.0
runConc :: MonadUnliftIO m => Conc m a > m a Source #
Run a Conc
value on multiple threads.
Since: 0.2.9.0
data ConcException Source #
Things that can go wrong in the structure of a Conc
. These are
programmer errors.
Since: 0.2.9.0
Instances
Reexports
data AsyncCancelled #
The exception thrown by cancel
to terminate a thread.
Instances
Exception AsyncCancelled  
Defined in Control.Concurrent.Async  
Show AsyncCancelled  
Defined in Control.Concurrent.Async showsPrec :: Int > AsyncCancelled > ShowS # show :: AsyncCancelled > String # showList :: [AsyncCancelled] > ShowS #  
Eq AsyncCancelled  
Defined in Control.Concurrent.Async (==) :: AsyncCancelled > AsyncCancelled > Bool # (/=) :: AsyncCancelled > AsyncCancelled > Bool # 