#![allow(unused_variables)]
fn main() {
    let mut v = [4, -5, 1, -3, 2];
    v.sort_by(|a, b| a.cmp(b));
    assert_eq!(v, [- 5, - 3, 1, 2, 4]);
    v.sort_by(|a, b| b.cmp(a));
    assert_eq!(v, [4, 2, 1, - 3, - 5]);
}