How to chan_select over multiple chans that will terminate? about chan

[BurntSushi]

My primary problem with this issue is that you've built a contrived example. Because of that, it's super hard to give you a good answer. It would be much better if you could focus on the specific problem you want to solve. I'll try, though...

In this case, you really need to build termination into the logic of your program. Since the value received by each channel is an option, you can quit your loop once both channels have been closed.

This is what I came up with:

#[macro_use]
extern crate chan;

use std::thread;

fn main() {
    let (s1, r1) = chan::async();
    let (s2, r2) = chan::async();

    thread::spawn(move || run(5, s1));
    thread::spawn(move || run(10, s2));

    let mut found1 = 0;
    let mut found2 = 0;

    let (mut r1closed, mut r2closed) = (false, false);
    while !r1closed || !r2closed {
        chan_select! {
            r1.recv() -> n => {
                found1 += 1;
                println!("Got r1: {:?} ({})", n, found1);
                if n.is_none() {
                    r1closed = true;
                }
            },
            r2.recv() -> n => {
                found2 += 1;
                println!("Got r2: {:?} ({})", n, found2);
                if n.is_none() {
                    r2closed = true;
                }
            },
        }
    }

    // We'll obviously never get here
    println!("R1s: {} / R2s: {}", found1, found2);
}

fn run(n: u8, s: chan::Sender<u8>) {
    for i in 0..n {
        s.send(i * n);
    }
}

I don't quit grok your concerns about CPU usage. Certainly, in the specific code you've given me, it's not a problem.