proposition: Lemma row_rowsub m1 m2 n (f : 'I_m2 -> 'I_m1) (A : 'M_(m1, n)) i : row i (rowsub f A) = row (f i) A.
proof: Proof. by rewrite row_mxsub mxsub_id. 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)