proposition: Lemma subv_adjoin U x : (U <= <<U; x>>)%VS.
proof: Proof. by rewrite (subv_trans (sub_agenv _)) ?agenvS ?addvSl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype div tuple finfun bigop ssralg) mathcomp(finalg zmodp matrix vector poly)