proposition: Lemma app_last_l : forall x l1 l2, (l1 & x) ++ l2 = l1 ++ (x::l2).
proof: Proof. Proof using. intros. rewrite~ <- app_cons_r. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)