red in |- *; red in |- *; intros.
inversion_clear H.
Qed.
End Beta_Reduction.
Hint Resolve beta_intro: pts.
Section Delta_Reduction.
Inductive delta : env -> term -> term -> Prop :=
delta_intro :
forall (e : env) (n : nat) (d T : term),
item (Def d T) e n -> delta e (Ref n) (lift (S n) d).

Lemma delta_rule : Basic_rule.
apply Build_Basic_rule with delta.