proposition: Lemma tr_mxcol n (B_ : forall i, 'M[T]_(p_ i, n)) : (\mxcol_i B_ i)^T = \mxrow_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)