proposition: Fact mul_subdefA : associative mulq_subdef.
proof: Proof. by move=> x y z; rewrite !mulq_subdefE !mulrA. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order ssralg countalg div ssrnum) mathcomp(ssrint prime archimedean)