proposition: Lemma mem_rev_eq : forall l x, mem x (rev l) = mem x l.
proof: Proof. Proof using. extens. iff M. { lets H: mem_rev M. rewrite~ rev_rev in H. } { apply* mem_rev. } Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)