proposition: Lemma uniq_app : uniq (E ++ F) <-> uniq E /\ uniq F /\ disjoint E F.
proof: Proof. clear; intuition eauto using uniq_app_1, uniq_app_2, uniq_app_3, uniq_app_4. Qed.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.LibTactics Metalib.MetatheoryAtom Metalib.LibTactics