Definition diff : arity Tpoint 2 := fun A B : Tpoint => A <> B.

(* Specifications: *)
Lemma diff_perm_1 : forall A B, app_1_n diff A B -> app_n_1 diff B A.
Lemma diff_perm_2 : forall A B (X : cartesianPower Tpoint 0), app_2_n diff A B X -> app_2_n diff B A X.