(* Contribution to the Coq Library   V6.3 (July 1999)                    *)
Inductive Z : Set :=
| OZ : Z
| pos : nat -> Z
| neg : nat -> Z.
Definition IZ := pos 0.
Definition is_posn (x y : Z) :=
match x, y with
| pos n, pos m => n = m
| _, _ => False
end.

Lemma tech_pos_not_posZ : forall n m : nat, n <> m -> pos n <> pos m.
unfold not in |- *; intros.