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

Lemma wmsb_false_split2_wzero: forall sz (w: word (sz + 1)) b, wmsb w b = false -> wzero 1 = split2 sz 1 w.