#[global]
Instance succ_wd : Proper (Z.eq ==> Z.eq) Z.succ.
#[global]
Instance pred_wd : Proper (Z.eq ==> Z.eq) Z.pred.
#[global]
Instance add_wd : Proper (Z.eq ==> Z.eq ==> Z.eq) Z.add.
#[global]
Instance opp_wd : Proper (Z.eq ==> Z.eq) Z.opp.
#[global]
Instance sub_wd : Proper (Z.eq ==> Z.eq ==> Z.eq) Z.sub.

(* Specifications: *)
Lemma mul_comm : forall n m, n*m == m*n.
#[global]
Instance mul_wd : Proper (Z.eq ==> Z.eq ==> Z.eq) Z.mul.