(** Interval properties. *)
Remark Ztrunc_range_pos:
forall x, 0 < Ztrunc x -> (Z2R (Ztrunc x) <= x < Z2R (Ztrunc x + 1)%Z)%R.
Remark Ztrunc_range_zero:
forall x, Ztrunc x = 0 -> (-1 < x < 1)%R.

Theorem ZofB_range_pos:
forall f n, ZofB f = Some n -> 0 < n -> (Z2R n <= B2R _ _ f < Z2R (n + 1)%Z)%R.