Module OrderedPositive <: OrderedType.
Definition t := positive.
Definition eq (x y: t) := x = y.
Definition lt := Plt.
Proof (@eq_refl t).
Proof (@eq_sym t).
Proof (@eq_trans t).
Proof Plt_trans.
Proof Plt_ne.

Lemma eq_sym : forall x y : t, eq x y -> eq y x.