everlang solution in rust

everlang.rs

fn main() {
    for (io::stdin() as io::ReaderUtil).each_line |line| {
        for str::words_each(line) |message| {
            io::print(message);
            io::print(" ");
            if is_valid_message(str::chars(message)) {
                io::println("VALID");
            }
            else {
                io::println("INVALID");
            }
        }
    }
}

fn is_valid_message(message: &[char]) -> bool {
    let len = message.len();
    if len == 0 {
        return false;
    }

    match message[0] {
        'Z' => return is_valid_message(message.view(1, len)),
        'K' | 'M' | 'P' | 'Q' => {
            for uint::range(2, len - 1) |midpoint| {
                if is_valid_message(message.view(1, midpoint)) &&
                        is_valid_message(message.view(midpoint, len)) {
                    return true;
                }
            }
            return false;
        }
        _ => return len == 1 && 'a' <= message[0] && message[0] <= 'j',
    }
}