(** Normalization on little-endian numbers *)

Fixpoint nztail d :=
  match d with
  | Nil => Nil
  | D0 d => match nztail d with Nil => Nil | d' => D0 d' end
  | D1 d => D1 (nztail d)
  | D2 d => D2 (nztail d)
  | D3 d => D3 (nztail d)
  | D4 d => D4 (nztail d)
  | D5 d => D5 (nztail d)
  | D6 d => D6 (nztail d)
  | D7 d => D7 (nztail d)
  | D8 d => D8 (nztail d)
  | D9 d => D9 (nztail d)
  | Da d => Da (nztail d)
  | Db d => Db (nztail d)
  | Dc d => Dc (nztail d)
  | Dd d => Dd (nztail d)
  | De d => De (nztail d)
  | Df d => Df (nztail d)
  end.Definition lnorm d :=
  match nztail d with
  | Nil => zero
  | d => d
  end.

(* Specifications: *)
Lemma nzhead_revapp_0 d d' : nztail d = Nil -> nzhead (revapp d d') = nzhead d'.
Lemma nzhead_revapp d d' : nztail d <> Nil -> nzhead (revapp d d') = revapp (nztail d) d'.
Lemma nzhead_rev d : nztail d <> Nil -> nzhead (rev d) = rev (nztail d).
Lemma rev_rev d : rev (rev d) = d.
Lemma rev_nztail_rev d : rev (nztail (rev d)) = nzhead d.
Lemma nzhead_D0 u : nzhead (D0 u) = nzhead u.
Lemma nzhead_iter_D0 n u : nzhead (Nat.iter n D0 u) = nzhead u.
Lemma revapp_nil_inv d d' : revapp d d' = Nil -> d = Nil /\ d' = Nil.
Lemma rev_nil_inv d : rev d = Nil -> d = Nil.
Lemma rev_lnorm_rev d : rev (lnorm (rev d)) = unorm d.
Lemma nzhead_nonzero d d' : nzhead d <> D0 d'.
Lemma unorm_0 d : unorm d = zero <-> nzhead d = Nil.
Lemma unorm_nonnil d : unorm d <> Nil.
Lemma unorm_iter_D0 n u : unorm (Nat.iter n D0 u) = unorm u.
Lemma del_head_nonnil n u : n < nb_digits u -> del_head n u <> Nil.
Lemma del_tail_nonnil n u : n < nb_digits u -> del_tail n u <> Nil.
Lemma nzhead_involutive d : nzhead (nzhead d) = nzhead d.
Lemma nztail_involutive d : nztail (nztail d) = nztail d.
Lemma unorm_involutive d : unorm (unorm d) = unorm d.
Lemma norm_involutive d : norm (norm d) = norm d.
Lemma lnzhead_neq_d0_head l l' : ~(lnzhead l = cons d0 l').
Lemma lnzhead_head_nd0 h t : h <> d0 -> lnzhead (cons h t) = cons h t.
Lemma nzhead_del_tail_nzhead_eq n u : nzhead u = u -> n < nb_digits u -> nzhead (del_tail n u) = del_tail n u.
Lemma nzhead_del_tail_nzhead n u : n < nb_digits (nzhead u) -> nzhead (del_tail n (nzhead u)) = del_tail n (nzhead u).
Lemma unorm_del_tail_unorm n u : n < nb_digits (unorm u) -> unorm (del_tail n (unorm u)) = del_tail n (unorm u).
Lemma norm_del_tail_int_norm n d : n < nb_digits (match norm d with Pos d | Neg d => d end) -> norm (del_tail_int n (norm d)) = del_tail_int n (norm d).
Lemma nzhead_app_nzhead d d' : nzhead (app (nzhead d) d') = nzhead (app d d').
Lemma unorm_app_unorm d d' : unorm (app (unorm d) d') = unorm (app d d').
Lemma norm_app_int_norm d d' : unorm d' = zero -> norm (app_int (norm d) d') = norm (app_int d d').