Glorious `join with and` code

playground.rs

#![feature(slice_patterns)]

fn join_with_and(xs: &[&str]) -> String {
    match xs.split_last() {
        None => String::new(),
        Some((last, &[])) => last.to_string(),
        Some((last, &[first])) => format!("{} and {}", first, last),
        Some((last, beginning)) => format!("{}, and {}", beginning.join(", "), last),
    }
}

#[test]
fn works() {
    assert_eq!(join_with_and(&[]), "".to_string());
    assert_eq!(join_with_and(&["foo"]), "foo".to_string());
    assert_eq!(join_with_and(&["foo", "bar"]), "foo and bar".to_string());
    assert_eq!(
        join_with_and(&["twitter", "reddit", "hackernews"]),
        "twitter, reddit, and hackernews".to_string()
    );
}