fn main() {
    let v1 = vec![String::from("foo"), String::from("bar")];
    let v2 = vec![String::from("baz"), String::from("qux")];

    let it = v1.iter().map(|s1| v2.iter().map(|s2| s1.clone() + &s2)).flat_map(|x| x);

    for item in it {
        println!("{}", item)
    }
}