Definition opt_eq (ox oy: option L.t) : Prop :=
  match ox, oy with
  | None, None => True
  | Some x, Some y => L.eq x y
  | _, _ => False
  end.

(* Specifications: *)
Lemma opt_eq_refl: forall ox, opt_eq ox ox.
Lemma opt_eq_sym: forall ox oy, opt_eq ox oy -> opt_eq oy ox.
Lemma opt_eq_trans: forall ox oy oz, opt_eq ox oy -> opt_eq oy oz -> opt_eq ox oz.