proposition: Fact mulq_subdefC : commutative mulq_subdef.
proof: Proof. by move=> x y; rewrite !mulq_subdefE mulrC [_ * x.2]mulrC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order ssralg countalg div ssrnum) mathcomp(ssrint prime archimedean)