Definition Vector_0_is_nil (T : Type) (v : Vector.t T 0) : v = Vector.nil T :=
  match v with Vector.nil => eq_refl end.

Theorem VectorToList_append {A}: forall (m:nat) (v2:Vector.t A m) (n : nat) (v1 : Vector.t A n), (Vector.to_list v1) ++ (Vector.to_list v2) = Vector.to_list (Vector.append v1 v2).