(* fracions form an abelian group *)
Definition frac_zmodMixin :=  ZmodMixin addA addC add0_l addN_l.Canonical frac_zmodType := Eval hnf in ZmodType type frac_zmodMixin.

(* Specifications: *)
Lemma mulA : associative mul.
Lemma mulC : commutative mul.
Lemma mul1_l : left_id 1%:F mul.
Lemma mul_addl : left_distributive mul add.