From Undecidability.L.Tactics Require Export LClos.
Open Scope LClos.
(* *** Closure calculus interpreter *)
Definition CompBeta s t :=
match s,t with
|CompClos (lam ls) A,CompClos (lam lt) B => Some (CompClos ls (CompClos (lam lt) B::A))
|_,_ => None
end.
Definition CompAppCount j u v :=
match u,v with
(l,u),(k,v) => (j+(l+k),CompApp u v)
end.
Fixpoint CompSeval n (u: nat * Comp) : nat * Comp:=
match n with
S n =>
match u with
| (l,CompApp s t) =>
match CompBeta s t with
| Some u => CompSeval n (S l,u)
| None => CompSeval n (CompAppCount l (CompSeval n (0,s)) (CompSeval n (0,t)))
end
| (l,CompClos (app s t) A) => CompSeval n (l,(CompClos s A) (CompClos t A))
| (l,CompClos (var x) A) => (l,nth x A (CompVar x))
| u => u
end
| _ => u
end.
Proof with repeat (auto || congruence || subst || simpl in * || intuition).
intros vs vt eq. inv vs; inv vt... destruct s0... destruct s,s0... inv eq. repeat constructor... inv H1...
Qed.
Proof with repeat (apply validCompApp ||apply validCompClos || eauto || congruence || subst || simpl in * || intuition).
revert s k. induction n; intros s k vs... inv vs...
case_eq (CompBeta s0 t);intros...
-apply CompBeta_validComp in H1...
-assert (IHn1 := IHn s0 0 H). assert (IHn2 := IHn t 0 H0).
unfold snd in *. do 2 destruct ((CompSeval n (_,_)))...
-destruct s0...
Qed.
Hint Resolve CompSeval_validComp : core.
Proof with repeat (auto || congruence || subst || simpl in * || intuition).
intros eq. destruct s,t... destruct s... destruct s... destruct s... destruct s0... inv eq. repeat constructor...
Qed.
Functional Scheme CompSeval_ind := Induction for CompSeval Sort Prop.
Proof with (repeat inv_validComp;repeat (constructor || intuition|| subst ; eauto using star || rewrite Nat.sub_diag||cbn in *)).
pose (p:= (l,s)).
change (let (k, t) := CompSeval n p in k >= fst p /\ (snd p) >[(k-(fst p))] t).
generalize p. clear l s p. intros p.
functional induction (CompSeval n p); intros;cbn...
-apply CompBeta_sound in e2. destruct (CompSeval _ _);split... eapply CPow_trans;try  eassumption. lia.
-repeat destruct (CompSeval _ _)... eapply CPow_trans...
-repeat destruct (CompSeval _ _)... eapply CPow_trans...
Qed.

Lemma CompSeval_sound (n k:nat) s t : CompSeval n (0,s) = (k,t) -> s >[(k)] t.