taneb3.rs

use std::iter::Unfold;

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

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

trait AnotherSillyUnfold<'a, A, St> {
    fn unfold(self, f: 'a |&mut St| -> Option<A>) -> Unfold<'a, A, St>;
}

impl<'a, A, St> AnotherSillyUnfold<'a, A, St> for St {
    fn unfold(self, f: 'a |&mut St| -> Option<A>) -> Unfold<'a, A, St> {
        Unfold::new(self, f)
    }
}