(* 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 Union_spec: forall A (v: A) P Q, Union _ P Q v <-> P v \/ Q v.