fn cartesian<I, J, T, U>(x: I, y: J) -> Vec<(T, U)>
where
    I: IntoIterator<Item=T>,
    T: Clone,
    J: IntoIterator<Item=U>,
    J::IntoIter: Clone,
    U: Clone,
{
    let y = y.into_iter();
    x.into_iter().map(
        |xp| y.clone().map(
            move |yp| (xp.clone(), yp)
        )
    ).flat_map(|i| i).collect()
}

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

    let it = cartesian(v1.iter(), v2.iter());

    for item in it {
        let (s1, s2) = item;
        println!("{} {}", s1, s2)
    }
}