Definition is_finite f :=
  match f with
  | B754_finite _ _ _ _ => true
  | B754_zero _ => true
  | _ => false
  end.Definition is_finite_FF f :=
  match f with
  | F754_finite _ _ _ => true
  | F754_zero _ => true
  | _ => false
  end.

Theorem is_finite_FF2B : forall x Hx, is_finite (FF2B x Hx) = is_finite_FF x.