proposition: Lemma map_diag_mx d : (diag_mx d)^f = diag_mx d^f :> 'M_n.
proof: Proof. by apply/matrixP=> i j; rewrite !mxE rmorphMn. 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)