#[global]
Instance quotsSpec : BinOpSpec quots :=
  {| BPred := fun x d r : Z =>
       ((x = -4611686018427387904 /\ d = -1 /\ r = -4611686018427387904)
       \/ ((x <> -4611686018427387904 \/ d <> -1) /\ r = Z.quot x d))%Z;
     BSpec := quots_spec |}.#[global]
Instance Op_of_Z : UnOp of_Z :=
  { TUOp := fun x => cmodwB x; TUOpInj := of_Z_spec }.#[global]
Instance Op_to_Z : UnOp to_Z :=
  { TUOp := fun x => x ; TUOpInj := fun x : int => eq_refl }.

Lemma is_zeroE : forall n : int, is_zero n = (to_Z n =? 0)%Z.