End RowGroup.
Variables (gT : finGroupType) (G : {group gT}) (n' : nat).
Local Notation n := n'.+1.
Variable (rG : mx_representation F G n).
Fact GL_mx_repr : mx_repr 'GL_n[F] GLval. Proof. by []. Qed.
Canonical GLrepr := MxRepresentation GL_mx_repr.

Lemma rank_mx_group m n q : 'r([set: 'M['Z_q]_(m, n)]) = (m * n)%N.