intros p r H'; split.
apply oppBounded; auto.
case H'; auto.
intros f H'0.
rewrite Fopp_correct.
replace (- FtoR radix p - - r)%R with (- (FtoR radix p - r))%R;
[ idtac | ring ].
replace (FtoR radix f - - r)%R with (- (- FtoR radix f - r))%R;
[ idtac | ring ].
rewrite <- Fopp_correct.
repeat rewrite Rabs_Ropp.
case H'; auto with float.
Qed.

Theorem ClosestFabs :
forall (p : float) (r : R),
Closest b radix r p -> Closest b radix (Rabs r) (Fabs p).