proposition: Lemma eqmx_rowsub (m n p q : nat) (h : 'I_n -> 'I_p) f g (A : 'M_(m, q)) : injective h -> p <= n -> f =1 g \o h -> (rowsub f A :=: rowsub g A)%MS.
proof: Proof. by move=> leq_pn h_inj /eq_rowsub->; apply: eqmx_rowsub_comp. 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 finalg zmodp matrix)