repeat rewrite wordToN_nat; repeat rewrite NToWord_nat.
rewrite nat_of_Nmult.
repeat rewrite nat_of_N_of_nat.
reflexivity.
Qed.

(* Specifications: *)
Theorem wneg_alt : forall sz (x : word sz), wneg x = wnegN x.
unfold wnegN, wneg; intros.