How to work around the fact that there is no Iterator::sort_by() method.

example.rs

fn compute_matches(choices: &Vec<String>, query: &str) -> Vec<String> {
    let unsorted_matches: Vec<(&String, f64)> = choices.iter().map(|choice| {
        (choice, score(choice.as_slice(), query))
    }).filter(|&(_choice, score)| {
        score > 0.0
    }).collect();

    let mut matches = unsorted_matches.clone();

    matches.sort_by(|&(_choice_a, score_a), &(_choice_b, score_b)| {
        if score_a > score_b {
            Ordering::Less
        } else if score_a < score_b {
            Ordering::Greater
        } else {
            Ordering::Equal
        }
    });

    matches.iter().map(|&(choice, _score)| {
        // TODO clone here is not ideal, but i cannot
        // yet figure out how to borrow through all of this
        // correctly
        choice.clone()
    }).collect()
}

See https://gist.github.com/hjr3/eaa3c53b29f6191ba265 for a better way