proposition: Lemma trace_map_mx (A : 'M_n) : \tr A^f = f (\tr A).
proof: Proof. by rewrite rmorph_sum; 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)