proposition: Lemma fullrowsub_unit : rowsub frf A \in unitmx.
proof: Proof. by rewrite -row_full_unit fullrowsub_full. 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)