proposition: Lemma divIr : {in unit, left_injective (fun x y => x / y)}.
proof: Proof. by move=> x; rewrite -unitrV => /mulIr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)