proposition: Lemma combine_last : forall x r y s, length r = length s -> combine (r&x) (s&y) = (combine r s)&(x,y).
proof: Proof. Proof using. introv E. applys~ combine_app. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)