proposition: Lemma tr_mxblock {T : Type} {p q : nat} {p_ : 'I_p -> nat} {q_ : 'I_q -> nat} (B_ : forall i j, 'M[T]_(p_ i, q_ j)) : (\mxblock_(i, j) B_ i j)^T = \mxblock_(i, j) (B_ j 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)