proposition: Lemma all_comm_mx2P f g : reflect (f *m g = g *m f) (all_comm_mx [:: f; g]).
proof: Proof. by rewrite /comm_mxb /= all2rel2 ?eqxx //; exact: eqP. 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)