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//! Using `select!` to send and receive on the same channel at the same time.
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//!
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//! This example is based on the following program in Go.
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//!
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//! Source:
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//! - https://web.archive.org/web/20171209034309/https://www.nada.kth.se/~snilsson/concurrency
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//! - http://www.nada.kth.se/~snilsson/concurrency/src/matching.go
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//!
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//! Copyright & License:
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//! - Stefan Nilsson
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//! - Creative Commons Attribution 3.0 Unported License
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//! - https://creativecommons.org/licenses/by/3.0/
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//!
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//! ```go
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//! func main() {
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//! people := []string{"Anna", "Bob", "Cody", "Dave", "Eva"}
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//! match := make(chan string, 1) // Make room for one unmatched send.
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//! wg := new(sync.WaitGroup)
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//! for _, name := range people {
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//! wg.Add(1)
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//! go Seek(name, match, wg)
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//! }
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//! wg.Wait()
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//! select {
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//! case name := <-match:
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//! fmt.Printf("No one received %s’s message.\n", name)
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//! default:
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//! // There was no pending send operation.
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//! }
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//! }
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//!
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//! // Seek either sends or receives, whichever possible, a name on the match
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//! // channel and notifies the wait group when done.
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//! func Seek(name string, match chan string, wg *sync.WaitGroup) {
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//! select {
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//! case peer := <-match:
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//! fmt.Printf("%s received a message from %s.\n", name, peer)
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//! case match <- name:
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//! // Wait for someone to receive my message.
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//! }
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//! wg.Done()
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//! }
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//! ```
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use crossbeam_channel::{bounded, select};
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use crossbeam_utils::thread;
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fn main() {
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let people = vec!["Anna", "Bob", "Cody", "Dave", "Eva"];
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let (s, r) = bounded(1); // Make room for one unmatched send.
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// Either send my name into the channel or receive someone else's, whatever happens first.
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let seek = |name, s, r| {
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select! {
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recv(r) -> peer => println!("{} received a message from {}.", name, peer.unwrap()),
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send(s, name) -> _ => {}, // Wait for someone to receive my message.
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}
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};
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thread::scope(|scope| {
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for name in people {
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let (s, r) = (s.clone(), r.clone());
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scope.spawn(move |_| seek(name, s, r));
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}
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})
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.unwrap();
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// Check if there is a pending send operation.
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if let Ok(name) = r.try_recv() {
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println!("No one received {}’s message.", name);
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}
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}
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