proposition: Lemma tr_mxrow n (B_ : forall j, 'M[T]_(n, p_ j)) : (\mxrow_j B_ j)^T = \mxcol_i (B_ i)^T.
proof: Proof. by apply/matrixP => i j; rewrite !mxE. 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)