fact: Fixpoint diff (s : t) : t -> t := match s with | nil => fun _ => nil | x :: l => (fix diff_aux (s' : t) : t := match s' with | nil => s | x' :: l' => match X.compare x x' with | Lt => x :: diff l s' | Eq => diff l l' | Gt => diff_aux l' end end) end.
imports: MSetInterface OrdersFacts OrdersLists