occupiedSessions.rs

fn session_number(line: &str) -> Option<int> {
    line.split_iter(':').next().and_then(|s| int::from_str(s))
}

fn occupied_sessions(output: ~str) -> HashSet<int> {
    let mut set = HashSet::new();
    for line in output.line_iter(){
        match session_number(line) {
            Some(n) => { set.insert(n); }
            None => ()
        }
    }
    set
}