intros x H' H'0; unfold FPred in |- *.
generalize (Z_eq_bool_correct (Fnum x) (- pPred (vNum b)));
case (Z_eq_bool (Fnum x) (- pPred (vNum b))); auto.
intros H'1; Contradict H'; auto.
intros H'1;
generalize (Z_eq_bool_correct (Fnum x) (nNormMin radix precision));
case (Z_eq_bool (Fnum x) (nNormMin radix precision));
auto.
intros H'2; Contradict H'0; auto.
Qed.

Theorem FPredFopFSucc :
forall x : float, FPred x = Fopp (FSucc b radix precision (Fopp x)).