proposition: Lemma mulmx1 m n (A : 'M_(m, n)) : A *m 1%:M = A.
proof: Proof. by rewrite -diag_const_mx mul_mx_diag; apply/matrixP=> i j; rewrite !mxE mulr1. 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)