HORIZON HASKELLDocslts/ghc-10.0.x8fef28d2026-11-02Search packagesCtrl K
Theme: |

GHC 10.0.0.20260917 · lts/ghc-10.0.x · 8fef28d · 2026-11-02

Moduleconcurrent-extra-0.7.0.12Haskell98

Control.Concurrent.Broadcast

A Broadcast is a mechanism for communication between threads. Multiple listeners wait until a broadcaster broadcasts a value. The listeners block until the value is received. When the broadcaster broadcasts a value all listeners are woken.

All functions are exception safe. Throwing asynchronous exceptions will not compromise the internal state of a broadcast.

This module is designed to be imported qualified. We suggest importing it like:

import           Control.Concurrent.Broadcast              ( Broadcast )
import qualified Control.Concurrent.Broadcast as Broadcast ( ... )
Contents
  1. Creating broadcasts
  2. Listening to broadcasts
  3. Broadcasting
Synopsis
newtypenewtype Broadcast a
Source#

A broadcast is in one of two possible states:

  • "Silent": listening to the broadcast will block until a value is broadcasted.

  • "Broadcasting x": listening to the broadcast will return the value x without blocking.

Instances1Eq
  • Eq (Broadcast a)Defined in concurrent-extra-0.7.0.12 · Control.Concurrent.Broadcast

Creating broadcasts

Listening to broadcasts

valuelisten :: Broadcast a -> IO a
Source#

Listen to a broadcast.

  • If the broadcast is "broadcasting x", listen will return x immediately.

  • If the broadcast is "silent", listen will block until another thread broadcasts a value to the broadcast.

valuetryListen :: Broadcast a -> IO (Maybe a)
Source#

Try to listen to a broadcast; non blocking.

  • If the broadcast is "broadcasting x", tryListen will return Just x immediately.

  • If the broadcast is "silent", tryListen returns Nothing immediately.

valuelistenTimeout :: Broadcast a -> Integer -> IO (Maybe a)
Source#

Listen to a broadcast if it is available within a given amount of time.

Like listen, but with a timeout. A return value of Nothing indicates a timeout occurred.

The timeout is specified in microseconds.

If the broadcast is "silent" and a timeout of 0 μs is specified the function returns Nothing without blocking.

Negative timeouts are treated the same as a timeout of 0 μs.

Broadcasting

valuebroadcast :: Broadcast a -> a -> IO ()
Source#

Broadcast a value.

broadcast b x changes the state of the broadcast b to "broadcasting x".

If the broadcast was "silent" all threads that are listening to the broadcast will be woken.

valuesignal :: Broadcast a -> a -> IO ()
Source#

Broadcast a value before becoming "silent".

The state of the broadcast is changed to "silent" after all threads that are listening to the broadcast are woken and resume with the signalled value.

The semantics of signal are equivalent to the following definition:

  signal b x = block $ broadcast b x >> silence b