Definition numbers := 3 :: 2 :: 5 :: 9 :: 7 :: 6 :: 1 :: 0 :: 4 :: 8 :: nil.

Lemma vec_sorted_impl (X: Set) (P Q: relation X): (forall x y, P x y -> Q x y) -> forall n (l: Vector.t X n), vec.sorted P l -> vec.sorted Q l.