fn main() {
    fn first<T>(items: &[T]) -> Option<&T> { items.first() }
    assert_eq!(first(&[3,5,8]), Some(&3));
    assert_eq!(first(&["north","south"]), Some(&"north"));
    assert_eq!(first::<u32>(&[]), None);
    println!("Generic borrowed lookup handles numbers, text and empty input");
}