enum pattern { tabby, tortoiseshell, calico }
enum breed { beagle, rottweiler, pug }
type name = str;
enum ear_kind { lop, upright }
enum animal { cat(pattern), dog(breed), rabbit(name, ear_kind), tiger }

fn noise(a: animal) -> option<str> {
    alt a {
      cat(*)    { some("meow") }
      dog(*)    { some("woof") }
      rabbit(*) { none }
      tiger(*)  { some("roar") }
    }
}

fn main() {
    assert noise(cat(tabby)) == some("meow");
    assert noise(dog(pug)) == some("woof");
    assert noise(rabbit("Hilbert", upright)) == none;
    assert noise(tiger) == some("roar");
}