(*6.7*)

Fixpoint lendian (l:list byte): Z :=
  match l with
    nil => 0
  | h::t => Byte.unsigned h + 2^8 * lendian t
  end.

Lemma lendian_app: forall l1 l2, lendian (l1++l2) = lendian l1 + 2^(8*Zlength l1) * lendian l2.