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

Lemma Intsize_monotone a b: 0 <= Int.unsigned (Int.repr a) <= Int.unsigned (Int.repr b) -> Int.size (Int.repr a) <= Int.size (Int.repr b).