#![allow(dead_code, deprecated, unused_variables, unused_mut)]
fn main() {
    let s = "Per Martin-Löf";
    let (first, last) = s.split_at_checked(3).unwrap();
    assert_eq!("Per", first);
    assert_eq!(" Martin-Löf", last);
    assert_eq!(None, s.split_at_checked(13));
    assert_eq!(None, s.split_at_checked(16));
}