►The Racket Reference
►10 Concurrency and Parallelism
▼10.2 Synchronization
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channel?
make-channel
channel-get
channel-try-get
channel-put
channel-put-evt
channel-put-evt?
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10.2.2 Channels

A channel both synchronizes a pair of threads and passes a value from one to the other. Channels are synchronous; both the sender and the receiver must block until the (atomic) transaction is complete. Multiple senders and receivers can access a channel at once, but a single sender and receiver is selected for each transaction.

Channel synchronization is fair: if a thread is blocked on a channel and transaction opportunities for the channel occur infinitely often, then the thread eventually participates in a transaction.

For buffered asynchronous channels, see Buffered Asynchronous Channels.

procedure

(channel? v) → boolean?

  v : any/c
Returns #t if v is a channel, #f otherwise.

procedure

(make-channel) → channel?

Creates and returns a new channel. The channel can be used with channel-get, with channel-try-get, or as a synchronizable event (see Events) to receive a value through the channel. The channel can be used with channel-put or through the result of channel-put-evt to send a value through the channel.

procedure

(channel-get ch) → any

  ch : channel?
Blocks until a sender is ready to provide a value through ch. The result is the sent value.

procedure

(channel-try-get ch) → any

  ch : channel?
Receives and returns a value from ch if a sender is immediately ready, otherwise returns #f.

procedure

(channel-put ch v) → void?

  ch : channel?
  v : any/c
Blocks until a receiver is ready to accept the value v through ch.

procedure

(channel-put-evt ch v) → channel-put-evt?

  ch : channel?
  v : any/c
Returns a fresh synchronizable event for use with sync. The event is ready when (channel-put ch v) would not block, and the event’s synchronization result is the event itself.

procedure

(channel-put-evt? v) → boolean?

  v : any/c
Returns #t if v is a channel-put event produced by channel-put-evt, #f otherwise.

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