proposition: Lemma tr_mxdiag (B_ : forall i, 'M[V]_(p_ i)) : (\mxdiag_i B_ i)^T = \mxdiag_i (B_ i)^T.
proof: Proof. rewrite tr_mxblock; apply/eq_mxblock => i j. by case: eqVneq => [->|]; rewrite ?trmx_conform ?trmx0. 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)