proposition: Lemma binds_app : binds x a (E ++ F) <-> binds x a E \/ binds x a F.
proof: Proof. clear. intuition auto using binds_app_1, binds_app_2, binds_app_3. Qed.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.LibTactics Metalib.MetatheoryAtom Metalib.LibTactics