#![allow(dead_code, deprecated, unused_variables, unused_mut)]
fn main() {
    let a = ["1", "two", "NaN", "four", "5"];
    let mut iter = a.iter().filter_map(|s| s.parse().ok());
    assert_eq!(iter.next(), Some(1));
    assert_eq!(iter.next(), Some(5));
    assert_eq!(iter.next(), None);
}