..

gistfile1.rs

use task::spawn;
use uint::range;
use io::println;
use pipes::{stream, Port, Chan};

const N: uint = 100;

fn main() {
    let mut chans: ~[mut (Chan<uint>, Port<uint>)] = ~[mut];
    for range(0, N) |_i| {
        vec::push(chans, stream());
    }
    for range(0, N) |i| {
        let input = &chans[i].second();
        if i == N - 1 {
            let output = &chans[0].first();
            do spawn { node(input, output); }
        } else {
            let output = &chans[i + 1].first();
            do spawn { node(input, output); }
        }
    }
}

fn node(input: &Port<uint>, output: &Chan<uint>) {
    let mut n: uint;
    loop {
        n = input.recv();
        if n == 0 {
            output.send(0);
            break;
        }
        output.send(n - 1);
    }
}