(* This file is copied from RamifyCoq project. *)
Require Coq.Setoids.Setoid.
Require Export Coq.Classes.Equivalence.
Require Export Coq.Sets.Ensembles.
intros.
split; intros [].
Qed.

Lemma Disjoint_spec: forall A P Q, Disjoint A P Q <-> (forall x, P x -> Q x -> False).