Module NBaseProp (Import N : NAxiomsMiniSig').
(** First, we import all known facts about both natural numbers and integers. *)
Include NZProp N.
(** From [pred_0] and order facts, we can prove that 0 isn't a successor. *)
(** Next, we show that all numbers are nonnegative and recover regular induction from the bidirectional induction on NZ *)

Theorem le_0_l : forall n, 0 <= n.