proposition: Lemma divrI : {in unit, right_injective (fun x y => x / y)}.
proof: Proof. by move=> x /mulrI/inj_comp; apply; apply: invr_inj. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)