proposition: Lemma CNFr_p6 f n: natp n -> CNFr_ax f n -> n <> \0c -> CNFrv f n <> \0o.
proof: Proof. move => nN ax nz rz. move: (cpred_pr nN nz) => [sa sb]. rewrite sb in ax rz. move:(CNFr_p2 sa ax); rewrite rz => /oleNgt; apply. exact: (oopow_pos (proj1 ax _ (cltS sa))). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)