Notation false_xorb := xorb_false_l (only parsing).
(** [true] is "complementing" for [xorb] *)

(* Specifications: *)
Lemma xorb_true_r : forall b:bool, xorb b true = negb b.
Lemma xorb_true_l : forall b:bool, xorb true b = negb b.
Notation xorb_true := xorb_true_r (only parsing).