induction n; intros.
rewrite (eq_nil x), (eq_nil y)...
rewrite (eq_cons x), (eq_cons y) in *...
inversion H.
rewrite (IHn (tail x) (tail y))...
Qed.

(* Specifications: *)
Lemma eq_list A (l: List.list A) (v: Vector.t A (List.length l)): from_list l = v -> l = to_list v.
Proof with auto.