Module NAddProp (Import N : NAxiomsMiniSig').
Include NBaseProp N.
(** For theorems about [add] that are both valid for [N] and [Z], see [NZAdd] *)
(** Now comes theorems valid for natural numbers but not for Z *)

Theorem add_pred_l : forall n m, n ~= 0 -> P n + m == P (n + m).