proposition: Lemma comm_horner_mx2 A p q : GRing.comm (horner_mx A p) (horner_mx A q).
proof: Proof. exact/comm_mx_horner/comm_horner_mx. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(div fintype tuple finfun bigop fingroup perm) mathcomp(ssralg zmodp matrix mxalgebra poly polydiv)