proposition: Lemma mxrank_unit n (A : 'M_n) : A \in unitmx -> \rank A = n.
proof: Proof. by rewrite -row_full_unit => /eqnP. 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)