proposition: Lemma row_permEsub s : row_perm s = rowsub s.
proof: Proof. by rewrite /row_perm /mxsub !unlock. 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)