occupiedSessions.rs

fn sessionNumber(line: &str) -> Option<int> {
    match(line.as_slice().split_iter(':').next()) {
        Some(first) => int::from_str(first),
        _ => None
    }
}

fn occupiedSessions(output: ~str) -> @HashSet<int> {
    let set = @HashSet::new();
    for line in output.line_iter(){
        // v-----  screams "match arms have incompatible types: expected `bool` but found `()` (expected bool but found ())"
        match sessionNumber(line) {
            Some(n) => set.insert(n),
            None => ()
        }
        ()
    }
    set
}