fn bump_smaller(x: &mut i32, y: &mut i32) {
    if *x <= *y {
        *x += 1;
    } else {
        *y += 1;
    }
}

fn main() {
    // example with variables
    let mut x = 5;
    let mut y = 6;
    bump_smaller(&mut x, &mut y);
    assert_eq!(x, y);

    // example with fields
    struct Pair {
        x: i32,
        y: i32,
    }
    let mut pair = Pair { x: 5, y: 6 };
    bump_smaller(&mut pair.x, &mut pair.y);
    assert_eq!(pair.x, pair.y);

    // Getting two &mut references into a Vec is a little trickier. The obvious
    // approach leads to a compiler error:
    //     let mut vec = vec![5, 6];
    //     bump_smaller(&mut vec[0], &mut vec[1]);
    // error[E0499]: cannot borrow `vec` as mutable more than once at a time

    // example with Vec using split_at_mut
    let mut vec = vec![5, 6];
    let (left, right) = vec.split_at_mut(1);
    bump_smaller(&mut left[0], &mut right[0]);
    assert_eq!(vec[0], vec[1]);

    // example with Vec using a match pattern
    let mut vec = vec![5, 6];
    match &mut vec[..] {
        [x, y] => bump_smaller(x, y),
        _ => unreachable!(),
    }
    assert_eq!(vec[0], vec[1]);
}