rust/src/test/bench/shootout-ackermann.rs

use std;

fn ack(m: int, n: int) -> int {
    if m == 0 {
        ret n + 1
    } else {
        if n == 0 {
            ret ack(m - 1, 1);
        } else {
            ret ack(m - 1, ack(m, n - 1));
        }
    }
}

fn main(args: ~[~str]) {
    let args = if os::getenv(~"RUST_BENCH").is_some() {
        ~[~"", ~"12"]
    } else if args.len() <= 1u {
        ~[~"", ~"8"]
    } else {
        args
    };
    let n = int::from_str(args[1]).get();
    io::println(fmt!{"Ack(3,%d): %d\n", n, ack(3, n)});
}