proposition: Lemma app_r_eq_self_inv : forall l1 l2, l1 ++ l2 = l2 -> l1 = nil.
proof: Proof. Proof using. introv E. apply length_zero_inv. lets: (args_eq_1 (@length A) E). rew_list in H. math. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)