proposition: Lemma xcolE m n j1 j2 (A : 'M_(m, n)) : xcol j1 j2 A = A *m tperm_mx j1 j2.
proof: Proof. by rewrite /xcol col_permE tpermV. 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)