proposition: Lemma comm_scalar_mx n a (A : 'M[R]_n) : comm_mx a%:M A.
proof: Proof. exact/comm_mx_sym/comm_mx_scalar. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg countalg finalg zmodp)