proposition: Lemma mem_Exists : forall P l x, mem x l -> P x -> Exists P l.
proof: Proof. Proof using. introv M H. rewrite* Exists_eq_exists_mem. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)