(* * Implementation of [ϕ] (aka SplitBody) *)
From Undecidability.TM.L Require Import Alphabets CaseCom.
Local Arguments plus : simpl never.
Local Arguments mult : simpl never.
(* The [JumpTarget] machine only operates on programs. Thus we define [JumpTarget] on the alphabet [sigPro^+]. *)
(* This is the only way we can encode [nat] on [sigPro]: as a variable token. *)
Definition retr_nat_prog : Retract sigNat sigPro := Retract_sigList_X _.
(* append a token to the token list *)
Definition App_ACom (t : ACom) : pTM sigPro^+ unit 2 :=
WriteValue [ACom2Com t] @ [|Fin1|];;
App _.
Definition App_ACom_size (t : ACom) (Q : list Tok) : Vector.t (nat->nat) 2 :=
[| id; WriteValue_size [ACom2Com t] |] >>> App_size Q [ACom2Com t].
Definition App_ACom_Rel (t : ACom) : pRel sigPro^+ unit 2 :=
ignoreParam (
fun tin tout =>
forall (Q : list Tok) (s0 s1:nat),
tin[@Fin0] ≃(;s0) Q ->
isVoid_size tin[@Fin1] s1 ->
tout[@Fin0] ≃(;App_ACom_size t Q @>Fin0 s0) Q ++ [ACom2Com t] /\
isVoid_size tout[@Fin1] (App_ACom_size t Q @>Fin1 s1)
).
Arguments App_ACom_size : simpl never.
Definition App_ACom_steps (Q: Pro) (t: ACom) := 1 + WriteValue_steps (size [ACom2Com t]) + App_steps Q [ACom2Com t].
Definition App_ACom_T (t: ACom) : tRel sigPro^+ 2 :=
fun tin k => exists (Q: list Tok), tin[@Fin0] ≃ Q /\ isVoid tin[@Fin1] /\ App_ACom_steps Q t <= k.
(* Add a singleton list of tokes to [Q] *)
Definition App_Com : pTM sigPro^+ (FinType(EqType unit)) 3 :=
Constr_nil _ @ [|Fin2|];;
Constr_cons _@ [|Fin2; Fin1|];;
App _ @ [|Fin0; Fin2|];;
Reset _ @ [|Fin1|].
Definition App_Com_size (Q : list Tok) (t : Tok) : Vector.t (nat->nat) 3 :=
[| App_size Q [t] @>Fin0; Reset_size t; pred >> Constr_cons_size t >> App_size Q [t] @>Fin1 |].
Definition App_Com_Rel : pRel sigPro^+ (FinType(EqType unit)) 3 :=
ignoreParam (
fun tin tout =>
forall (Q : list Tok) (t : Tok) (s0 s1 s2 : nat),
tin[@Fin0] ≃(;s0) Q ->
tin[@Fin1] ≃(;s1) t ->
isVoid_size tin[@Fin2] s2 ->
tout[@Fin0] ≃(;App_Com_size Q t @>Fin0 s0) Q ++ [t] /\
isVoid_size tout[@Fin1] (App_Com_size Q t @>Fin1 s1) /\
isVoid_size tout[@Fin2] (App_Com_size Q t @>Fin2 s2)
).
Arguments App_Com_size : simpl never.
Definition App_Com_steps (Q: Pro) (t:Tok) :=
3 + Constr_nil_steps + Constr_cons_steps t + App_steps Q [t] + Reset_steps t.
Definition App_Com_T : tRel sigPro^+ 3 :=
fun tin k => exists (Q: list Tok) (t: Tok), tin[@Fin0] ≃ Q /\ tin[@Fin1] ≃ t /\ isVoid tin[@Fin2] /\ App_Com_steps Q t <= k.
Definition JumpTarget_Step : pTM sigPro^+ (option bool) 5 :=
If (CaseList sigCom_fin @ [|Fin0; Fin3|])
(Switch (ChangeAlphabet CaseCom _ @ [|Fin3|])
(fun t : option ACom =>
match t with
| Some retAT =>
If (CaseNat ⇑ retr_nat_prog @ [|Fin2|])
(Return (App_ACom retAT @ [|Fin1; Fin4|]) None) (* continue *)
(Return (ResetEmpty1 _ @ [|Fin2|]) (Some true)) (* return true *)
| Some lamAT =>
Return (Constr_S ⇑ retr_nat_prog @ [|Fin2|];;
App_ACom lamAT @ [|Fin1; Fin4|])
None (* continue *)
| Some appAT =>
Return (App_ACom appAT @ [|Fin1;Fin4|])
None (* continue *)
| None => (* Variable *)
Return (Constr_varT ⇑ _ @ [|Fin3|];;
App_Com @ [|Fin1; Fin3; Fin4|])
None (* continue *)
end))
(Return Nop (Some false)) (* return false *)
.
Definition JumpTarget_Step_size (P Q : Pro) (k : nat) : Vector.t (nat->nat) 5 :=
match P with
| retT :: _ =>
match k with
| S _ =>
[| (*0*) CaseList_size0 retT; (*1*) App_ACom_size retAT Q @>Fin0; (*2*) S;                (*3*) CaseList_size1 retT >> CaseCom_size retT; (*4*) App_ACom_size retAT Q @>Fin1 |]
| 0 =>
[| (*0*) CaseList_size0 retT; (*1*) id;                           (*2*) ResetEmpty1_size; (*3*) CaseList_size1 retT >> CaseCom_size retT; (*4*) id |]
end
| lamT :: _ =>
[| (*0*) CaseList_size0 lamT; (*1*) App_ACom_size lamAT Q @>Fin0; (*2*) pred; (*3*) CaseList_size1 lamT >> CaseCom_size lamT; (*4*) App_ACom_size lamAT Q @>Fin1 |]
| appT :: _ =>
[| (*0*) CaseList_size0 appT; (*1*) App_ACom_size appAT Q @>Fin0; (*2*) id; (*3*) CaseList_size1 retT >> CaseCom_size appT; (*4*) App_ACom_size appAT Q @>Fin1 |]
| varT n :: _ =>
[| (*0*) CaseList_size0 (varT n); (*1*) App_Com_size Q (varT n) @>Fin0; (*2*) id; (*3*) CaseList_size1 (varT n) >> CaseCom_size (varT n) >> pred >> App_Com_size Q (varT n) @>Fin1; (*4*) App_Com_size Q (varT n) @>Fin2 |]
| nil => Vector.const id _
end.
Definition JumpTarget_Step_Rel : pRel sigPro^+ (option bool) 5 :=
fun tin '(yout, tout) =>
forall (P Q : Pro) (k : nat) (s0 s1 s2 s3 s4 : nat),
let size := JumpTarget_Step_size P Q k in
tin[@Fin0] ≃(;s0) P ->
tin[@Fin1] ≃(;s1) Q ->
tin[@Fin2] ≃(;s2) k ->
isVoid_size tin[@Fin3] s3 -> isVoid_size tin[@Fin4] s4 ->
match yout, P with
| _, retT :: P =>
match yout, k with
| Some true, O => (* return true *)
tout[@Fin0] ≃(;size @>Fin0 s0) P /\
tout[@Fin1] ≃(;size @>Fin1 s1) Q /\
isVoid_size tout[@Fin2] (size @>Fin2 s2)
| None, S k' => (* continue *)
tout[@Fin0] ≃(;size @>Fin0 s0) P /\
tout[@Fin1] ≃(;size @>Fin1 s1) Q ++ [retT] /\
tout[@Fin2] ≃(;size @>Fin2 s2) k'
| _, _ => False (* not the case *)
end
| None, lamT :: P => (* continue *)
tout[@Fin0] ≃(;size@>Fin0 s0) P /\
tout[@Fin1] ≃(;size@>Fin1 s1) Q ++ [lamT] /\
tout[@Fin2] ≃(;size@>Fin2 s2) S k
| None, t :: P => (* continue *)
tout[@Fin0] ≃(;size@>Fin0 s0) P /\
tout[@Fin1] ≃(;size@>Fin1 s1) Q ++ [t] /\
tout[@Fin2] ≃(;size@>Fin2 s2) k
| Some false, nil => (* return false *)
True
| _, _ => False (* not the case *)
end /\
isVoid_size tout[@Fin3] (size@>Fin3 s3) /\
isVoid_size tout[@Fin4] (size@>Fin4 s4).

Lemma JumpTarget_Step_Realise : JumpTarget_Step ⊨ JumpTarget_Step_Rel.