#![allow(dead_code, deprecated, unused_variables, unused_mut)]
#![feature(iter_map_windows)]
fn main() {
    let mut it = [1, 3, 8, 1].iter().map_windows(|&[a, b]| a + b);
    assert_eq!(it.next(), Some(4));
    assert_eq!(it.next(), Some(11));
    assert_eq!(it.next(), Some(9));
    assert_eq!(it.next(), None);
}