proposition: Lemma scalar_mx_is_additive : additive (@scalar_mx V n).
proof: Proof. by move=> a b; rewrite -!diag_const_mx !raddfB. 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)