trait noisy { fn speak(); } struct cat : noisy { priv { let mut meows : uint; fn meow() { error!("Meow"); self.meows += 1u; if self.meows % 5u == 0u { self.how_hungry += 1; } } } let mut how_hungry : int; let name : ~str; new(in_x : uint, in_y : int, in_name: ~str) { self.meows = in_x; self.how_hungry = in_y; self.name = in_name; } fn speak() { self.meow(); } fn eat() -> bool { if self.how_hungry > 0 { error!("OM NOM NOM"); self.how_hungry -= 2; return true; } else { error!("Not hungry!"); return false; } } } fn main() { let nyan : noisy = cat(0u, 2, ~"nyan") as noisy; nyan.speak(); }