proposition: Lemma subfield_closed K : agenv K = K.
proof: Proof. by apply/eqP; rewrite eqEsubv sub_agenv agenv_sub_modr ?sub1v ?asubv. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype tuple finfun bigop ssralg countalg) mathcomp(finalg zmodp matrix vector falgebra poly polydiv) mathcomp(mxpoly generic_quotient)