#![allow(dead_code, deprecated, unused_variables, unused_mut)]
#![feature(iter_order_by)]
use std::cmp::Ordering;
fn main() {
    let xs = [1, 2, 3, 4];
    let ys = [1, 4, 9, 16];
    assert_eq!(xs.into_iter().cmp_by(ys, | x, y | x.cmp(& y)), Ordering::Less);
    assert_eq!(xs.into_iter().cmp_by(ys, | x, y | (x * x).cmp(& y)), Ordering::Equal);
    assert_eq!(xs.into_iter().cmp_by(ys, | x, y | (2 * x).cmp(& y)), Ordering::Greater);
}