proposition: Lemma rV0Pn n (v : 'rV_n) : reflect (exists i, v 0 i != 0) (v != 0).
proof: Proof. apply: (iffP (matrix0Pn _)) => [[i [j]]|[j]]; last by exists 0, j. by rewrite ord1; exists j. 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)