proposition: Lemma mem_Exists_eq : forall P l x, mem x l = Exists (= x) l.
proof: Proof. Proof using. intros. extens. rewrite* Exists_eq_exists_mem. iff M (y&?&?); subst*. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)