proposition: Fact subvs_mulA : associative subvs_mul.
proof: Proof. by move=> x y z; apply/val_inj/mulrA. 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)