proposition: Lemma scalar_mx_is_semi_additive : semi_additive scalar_mx.
proof: Proof. by split=> [|a b]; rewrite -!diag_const_mx ?raddf0// !raddfD. 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)