proposition: Lemma mxtrace_is_additive : additive (@mxtrace V n).
proof: Proof. move=>A B; rewrite -sumrN -big_split /=. by apply: eq_bigr=> i _; rewrite !mxE. 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)