proposition: Lemma OS_ord_powa a b: ordinalp a -> ordinalp b -> ordinalp (a ^O b).
proof: Proof. by move=> oa ob; apply: OS_ordinal; apply: olexp_worder; apply: ordinal_o_wor. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)