proposition: Lemma row_id n i (V : 'rV_n) : row i V = V.
proof: Proof. by apply/rowP=> j; rewrite mxE [i]ord1. 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)