In which I learn to use the ref keyword.

list.rs

enum List {
  Nil,
  Node(int, ~List)
}

fn walk(l: &List) -> ~str {
  match *l {
    Node(i, ref rest) => fmt!("%d %s", i, walk(*rest)),
    Nil => ~"end"
  }
}

fn main() {
  let list = Node(5, ~Node(4, ~Node(3, ~Node(2, ~Nil))));
  println(walk(&list));
}