testmp.rs

enum State {
    Even(~int),
    Odd(~int)
}

struct MyNumber {
    num: State
}

impl MyNumber {
    fn new() -> MyNumber {
        MyNumber {
            num: Even(~0)
        }
    }
    fn next(&mut self) -> bool {
        let (next, ret) = match self.num {
            Even(ref x) => (Odd(~(**x + 1)), true),
            Odd(ref y) => (Even(~(**y + 1)), false)
        };
        self.num = next;
        ret
    }    
}

fn main() {
}