proposition: Lemma mulKr : {in unit, left_loop (@inv R) *%R}.
proof: Proof. by move=> x Ux y; rewrite mulrA mulVr ?mul1r. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)