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