fibonacci input stuff

use std::iter::Unfold;
use std::os::args;

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

fn main() {
    let argsV = args();
    let argI = argsV.iter().idx(1).map_or(20, |arg0| {from_str(arg0.clone()).unwrap_or(2)});

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