#![feature(conservative_impl_trait)]

fn main() {
    for num in fibonacci_gen(10) {
        println!("{}", num);
    }
}

fn fibonacci_gen(terms: i32) -> impl Iterator<Item=u64> {
    let sqrt_5 = 5.0f64.sqrt();
    let p  = (1.0 + sqrt_5) / 2.0;
    let q = 1.0/p;
    (1..terms).map(move |n| ((p.powi(n) + q.powi(n)) / sqrt_5 + 0.5) as u64)
}