proposition: Lemma lin_mulmxr_is_linear : linear lin_mulmxr.
proof: Proof. move=> a A B; apply/row_matrixP; case/mxvec_indexP=> i j. rewrite linearP /= !rowE !mul_rV_lin /= vec_mx_delta -linearP mulmxDr. congr (mxvec (_ + _)); apply/row_matrixP=> k. rewrite linearZ /= !row_mul rowE mul_delta_mx_cond. by case: (k == i); [rewrite -!rowE linearZ | rewrite !mul0mx raddf0]. 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)