proposition: Lemma uniq_app_2 : uniq (E ++ F) -> uniq F.
proof: Proof. clear. intros H; induction E as [ | a E']. apply H. inversion H; subst. auto. inversion H; subst. auto. Qed.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.LibTactics Metalib.MetatheoryAtom Metalib.LibTactics