Definition Fopp (x : float) := Float (- Fnum x) (Fexp x).

(* Specifications: *)
Theorem Fopp_correct : forall x : float, Fopp x = (- x)%R :>R.
Theorem Fopp_Fopp : forall p : float, Fopp (Fopp p) = p.
Theorem Fzero_opp : forall f : float, ~ is_Fzero f -> ~ is_Fzero (Fopp f).
Theorem Fdigit_opp : forall x : float, Fdigit radix (Fopp x) = Fdigit radix x.