proposition: Lemma length_zero_eq_eq_nil : forall l, (length l = 0) = (l = nil).
proof: Proof. Proof using. extens. iff M. destruct l; rew_list; auto_false*. { subst*. } Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)