Remark two_power_nat_infinity:
  forall x, 0 <= x -> exists n, x < two_power_nat n.

(* Specifications: *)
Lemma equal_same_bits: forall x y, (forall i, 0 <= i -> Z.testbit x i = Z.testbit y i) -> x = y.
Lemma Z_one_complement: forall i, 0 <= i -> forall x, Z.testbit (-x-1) i = negb (Z.testbit x i).
Lemma Ztestbit_above: forall n x i, 0 <= x < two_power_nat n -> i >= Z.of_nat n -> Z.testbit x i = false.
Lemma Ztestbit_above_neg: forall n x i, -two_power_nat n <= x < 0 -> i >= Z.of_nat n -> Z.testbit x i = true.
Lemma Zsign_bit: forall n x, 0 <= x < two_power_nat (S n) -> Z.testbit x (Z.of_nat n) = if zlt x (two_power_nat n) then false else true.
Lemma Zshiftin_ind: forall (P: Z -> Prop), P 0 -> (forall b x, 0 <= x -> P x -> P (Zshiftin b x)) -> forall x, 0 <= x -> P x.
Lemma Zshiftin_pos_ind: forall (P: Z -> Prop), P 1 -> (forall b x, 0 < x -> P x -> P (Zshiftin b x)) -> forall x, 0 < x -> P x.
Lemma Ztestbit_le: forall x y, 0 <= y -> (forall i, 0 <= i -> Z.testbit x i = true -> Z.testbit y i = true) -> x <= y.