proposition: Lemma diag_mx_comm n (d e : 'rV[R]_n) : comm_mx (diag_mx d) (diag_mx e).
proof: Proof. exact: diag_mxC. 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)