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