Ltac wlt_ind :=
  match goal with
  | [ |- forall (n: word ?len), ?P ] =>
    refine (well_founded_ind (@wlt_wf len) (fun n => P) _)
  end.

Lemma natToWord_Z_to_nat: forall sz n, (0 <= n)%Z -> natToWord sz (Z.to_nat n) = ZToWord sz n.