*)
(* Lemma Forall_isbyte_repr_unsigned: forall l: list int, map Int.repr (map Int.unsigned l) = l.  Lemma map_unsigned_repr_isbyte: forall l : list Z , Forall isbyteZ l -> map Int.unsigned (map Int.repr l) = l. *)

Lemma int_unsigned_inj: forall a b, Int.unsigned a = Int.unsigned b -> a=b.