fn main() {
    let x = vec!["i", "hate", "scala"];
    let y = x.into_iter().scan(1.., |i, s| {
        let mut r = String::from(s);
        for n in i.by_ref().take(s.len()) {
            r.push_str(&format!("-{}", n))
        }
        Some(r)
    });
    println!("{:?}", y.collect::<Vec<_>>())
}