proposition: Lemma rowP (u v : 'rV[R]_n) : u 0 =1 v 0 <-> u = v.
proof: Proof. by split=> [eq_uv | -> //]; apply/matrixP=> i; rewrite 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)