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

Lemma wordToZ_WS_1': forall sz (w: word (sz + 1)), wordToZ w~1 = (2 * wordToZ w + 1)%Z.