struct NodeUnit;
struct Node<S> {
    stack: S
}

impl<S> Node<S> {
    fn init() -> Node<()> {
        Node { stack: (()) }
    }
}



impl<C, P> Node<(C, P)> {
    fn push<N>(self, next: N) -> Node<(N, (C, P))> {
        Node { stack: (next, self.stack) }
    }

    fn peek(&self) -> &C {
        &self.stack.0
    }

    fn pop(self) -> Node<P> {
        Node { stack: self.stack.1 }
    }
}

fn main() {
    let n = Node::init();
    /*
    let n2 = n.push(0u8);
    let n3 = n2.push(1u16);
    println!("{}", n3.peek());

    let n2 = n3.pop();
    println!("{}", n2.peek());
    */
}