Definition lognat(n : nat) : nat := 
  N.size_nat (N.of_nat n).Definition bvToNat(k : nat)(v : Bvector k) :=
  N.to_nat (Bv2N k v).

(* Specifications: *)
Lemma Bv2N_zero : forall (n : nat), Bv2N n (Bvect_false n) = N0.
Lemma bvNat_zero : forall n, bvToNat (Bvect_false n) = O.