Module NZQuot := Nop <+ NZDivProp A Quot2Div B.
End Private_Div.
Ltac pos_or_neg a :=
let LT := fresh "LT" in
let LE := fresh "LE" in
destruct (le_gt_cases 0 a) as [LE|LT]; [|rewrite <- opp_pos_neg in LT].
(** Another formulation of the main equation *)
(** A few sign rules (simple ones) *)
(** A division of a small number by a bigger one yields zero. *)

Lemma rem_0_l: forall a, a~=0 -> 0 rem a == 0.