taneb.rs

use std::iter::Unfold;

fn next(arg: &mut (int, int)) -> Option<int> {
        let (lo, hi) = *arg;
        *arg = (hi, lo + hi);
        Some(lo)
}

fn main() {
    for fib in Unfold::new((0,1), next).take(20) {
        println!("{}", fib);
    };
}