proposition: Lemma mem_filter : forall x P l, mem x l -> P x -> mem x (filter P l).
proof: Proof. Proof using. intros. rewrite* mem_filter_eq. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)