proposition: Lemma z_omega_limit: limit_ordinal z_omega /\ forall z, limit_ordinal z -> z_omega <=o z.
proof: Proof. move: z_omega_prop z_omega_ordinal =>[ [qa qb] qc] oo. split; first by split. by move => y [pa pb pc]; split => //; apply: qc. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)