proposition: Theorem evalZltOr : forall v : rZ, evalZ v = v \/ rZlt (evalZ v) v.
proof: Proof. intros v; case v; simpl in |- *; auto with stalmarck; intros a; unfold evalN in |- *; generalize (fun s : rZ => wfPd _ War a s); case (rArrayGet _ Ar a); intros r H'; auto with stalmarck; right. lapply (H' r); auto with stalmarck. apply rZltEqComp with (a := r) (b := rZMinus a); auto with stalmarck. lapply (H' r); auto with stalmarck. Qed.