header {* CPS conversion *}

theory Plotkin

imports Lt

begin

nominal_primrec

  CPS :: "lt \<Rightarrow> lt" ("_*" [250] 250)

where

  "atom k \<sharp> x \<Longrightarrow> (x~)* = (Abs k ((k~) $ (x~)))"

| "atom k \<sharp> (x, M) \<Longrightarrow> (Abs x M)* = Abs k (k~ $ Abs x (M*))"

| "atom k \<sharp> (M, N) \<Longrightarrow> atom m \<sharp> (N, k) \<Longrightarrow> atom n \<sharp> (k, m) \<Longrightarrow>

    (M $ N)* = Abs k (M* $ Abs m (N* $ Abs n (m~ $ n~ $ k~)))"

unfolding eqvt_def CPS_graph_def

apply (rule, perm_simp, rule, rule)

apply (simp_all add: fresh_Pair_elim)

apply (rule_tac y="x" in lt.exhaust)

apply (auto)

apply (rule_tac x="name" and ?'a="name" in obtain_fresh)

apply (simp_all add: fresh_at_base)[3]

apply (rule_tac x="(name, lt)" and ?'a="name" in obtain_fresh)

apply (simp add: fresh_Pair_elim fresh_at_base)[2]

apply (rule_tac x="(lt1, lt2)" and ?'a="name" in obtain_fresh)

apply (rule_tac x="(lt2, a)" and ?'a="name" in obtain_fresh)

apply (rule_tac x="(a, aa)" and ?'a="name" in obtain_fresh)

apply (simp add: fresh_Pair_elim fresh_at_base)

apply (simp add: Abs1_eq_iff lt.fresh fresh_at_base)

--"-"

apply(rule_tac s="[[atom ka]]lst. ka~ $ Abs x (CPS_sumC M)" in trans)

apply (case_tac "k = ka")

apply simp

apply(simp (no_asm) add: Abs1_eq_iff del:eqvts)

apply (simp del: eqvts add: lt.fresh fresh_at_base)

apply (simp only: lt.perm_simps(1) lt.perm_simps(3) flip_def[symmetric] lt.eq_iff(3))

apply (subst  flip_at_base_simps(2))

apply simp

apply (intro conjI refl)

apply (rule flip_fresh_fresh[symmetric])

apply (simp_all add: lt.fresh)

apply (metis fresh_eqvt_at lt.fsupp)

apply (case_tac "ka = x")

apply simp_all[2]

apply (metis Abs_fresh_iff(3) atom_eq_iff finite_set fresh_Cons fresh_Nil fresh_atom fresh_eqvt_at fresh_finite_atom_set fresh_set lt.fsupp)

apply (metis Abs_fresh_iff(3) atom_eq_iff finite_set fresh_Cons fresh_Nil fresh_atom fresh_eqvt_at fresh_finite_atom_set fresh_set lt.fsupp)

--"-"

apply (simp add: Abs1_eq(3))

apply (erule Abs_lst1_fcb)

apply (simp add: fresh_def supp_Abs)

apply (drule_tac a="atom xa" in fresh_eqvt_at)

apply (simp add: finite_supp)

apply assumption

apply (simp add: fresh_def supp_Abs)

apply (simp add: eqvts eqvt_at_def)

apply simp

--"-"

apply (rename_tac k' M N m' n')

apply (subgoal_tac "atom k \<sharp> CPS_sumC M \<and> atom k' \<sharp> CPS_sumC M \<and> atom k \<sharp> CPS_sumC N \<and> atom k' \<sharp> CPS_sumC N \<and>

                    atom m \<sharp> CPS_sumC N \<and> atom m' \<sharp> CPS_sumC N")

prefer 2

apply (intro conjI)

apply (erule fresh_eqvt_at, simp add: finite_supp, assumption)+

apply clarify

apply (case_tac "k = k'", case_tac [!] "m' = k",case_tac [!]"m = k'",case_tac[!] "m = m'")

apply (simp_all add: Abs1_eq_iff lt.fresh flip_def[symmetric] fresh_at_base flip_fresh_fresh permute_eq_iff)

by (metis flip_at_base_simps(3) flip_at_simps(2) flip_commute permute_flip_at)+

termination

  by (relation "measure size") (simp_all add: lt.size)

lemmas [simp] = fresh_Pair_elim CPS.simps(2,3)[simplified fresh_Pair_elim]

lemma [simp]: "supp (M*) = supp M"

  by (induct rule: CPS.induct, simp_all add: lt.supp supp_at_base fresh_at_base fresh_def supp_Pair)

     (simp_all only: atom_eq_iff[symmetric], blast+)

lemma [simp]: "x \<sharp> M* = x \<sharp> M"

  unfolding fresh_def by simp

(* Will be provided automatically by nominal_primrec *)

lemma CPS_eqvt[eqvt]:

  shows "p \<bullet> M* = (p \<bullet> M)*"

  apply (induct M rule: lt.induct)

  apply (rule_tac x="(name, p \<bullet> name, p)" and ?'a="name" in obtain_fresh)

  apply simp

  apply (simp add: Abs1_eq_iff lt.fresh flip_def[symmetric])

  apply (metis atom_eqvt flip_fresh_fresh fresh_perm atom_eq_iff fresh_at_base)

  apply (rule_tac x="(name, lt, p \<bullet> name, p \<bullet> lt, p)" and ?'a="name" in obtain_fresh)

  apply simp

  apply (metis atom_eqvt fresh_perm atom_eq_iff)

  apply (rule_tac x="(lt1, p \<bullet> lt1, lt2, p \<bullet> lt2, p)" and ?'a="name" in obtain_fresh)

  apply (rule_tac x="(a, lt2, p \<bullet> lt2, p)" and ?'a="name" in obtain_fresh)

  apply (rule_tac x="(a, aa, p)" and ?'a="name" in obtain_fresh)

  apply (simp)

  apply (simp add: Abs1_eq_iff lt.fresh flip_def[symmetric])

  apply (metis atom_eqvt fresh_perm atom_eq_iff)

  done

nominal_primrec

  convert:: "lt => lt" ("_+" [250] 250)

where

  "(Var x)+ = Var x"

| "(Abs x M)+ = Abs x (M*)"

| "(M $ N)+ = M $ N"

  unfolding convert_graph_def eqvt_def

  apply (rule, perm_simp, rule, rule)

  apply (erule lt.exhaust)

  apply (simp_all)

  apply blast

  apply (simp add: Abs1_eq_iff CPS_eqvt)

  by blast

termination

  by (relation "measure size") (simp_all add: lt.size)

lemma convert_supp[simp]:

  shows "supp (M+) = supp M"

  by (induct M rule: lt.induct, simp_all add: lt.supp)

lemma convert_fresh[simp]:

  shows "x \<sharp> (M+) = x \<sharp> M"

  unfolding fresh_def by simp

lemma convert_eqvt[eqvt]:

  shows "p \<bullet> (M+) = (p \<bullet> M)+"

  by (nominal_induct M rule: lt.strong_induct, auto simp add: CPS_eqvt)

lemma [simp]:

  shows "isValue (p \<bullet> (M::lt)) = isValue M"

  by (nominal_induct M rule: lt.strong_induct) auto

lemma [eqvt]:

  shows "p \<bullet> isValue M = isValue (p \<bullet> M)"

  by (induct M rule: lt.induct) (perm_simp, rule refl)+

nominal_primrec

  Kapply :: "lt \<Rightarrow> lt \<Rightarrow> lt"       (infixl ";" 100)

where

  "Kapply (Abs x M) K = K $ (Abs x M)+"

| "Kapply (Var x) K = K $ Var x"

| "isValue M \<Longrightarrow> isValue N \<Longrightarrow> Kapply (M $ N) K = M+ $ N+ $ K"

| "isValue M \<Longrightarrow> \<not>isValue N \<Longrightarrow> atom n \<sharp> M \<Longrightarrow> atom n \<sharp> K \<Longrightarrow>

    Kapply (M $ N) K = N; (Abs n (M+ $ Var n $ K))"

| "\<not>isValue M \<Longrightarrow> atom m \<sharp> N \<Longrightarrow> atom m \<sharp> K \<Longrightarrow> atom n \<sharp> m \<Longrightarrow> atom n \<sharp> K \<Longrightarrow>

    Kapply (M $ N) K = M; (Abs m (N*  $ (Abs n (Var m $ Var n $ K))))"

  unfolding Kapply_graph_def eqvt_def

  apply (rule, perm_simp, rule, rule)

apply (simp_all)

apply (case_tac x)

apply (rule_tac y="a" in lt.exhaust)

apply (auto)

apply (case_tac "isValue lt1")

apply (case_tac "isValue lt2")

apply (auto)[1]

apply (rule_tac x="(lt1, ba)" and ?'a="name" in obtain_fresh)

apply (simp add: fresh_Pair_elim fresh_at_base)

apply (rule_tac x="(lt2, ba)" and ?'a="name" in obtain_fresh)

apply (rule_tac x="(a, ba)" and ?'a="name" in obtain_fresh)

apply (simp add: fresh_Pair_elim fresh_at_base)

apply (auto simp add: Abs1_eq_iff eqvts)[1]

apply (rename_tac M N u K)

apply (subgoal_tac "Abs n (M+ $ n~ $ K) =  Abs u (M+ $ u~ $ K)")

apply (simp only:)

apply (auto simp add: Abs1_eq_iff flip_def[symmetric] lt.fresh fresh_at_base flip_fresh_fresh[symmetric])[1]

apply (subgoal_tac "Abs m (Na* $ Abs n (m~ $ n~ $ Ka)) = Abs ma (Na* $ Abs na (ma~ $ na~ $ Ka))")

apply (simp only:)

apply (simp add: Abs1_eq_iff flip_def[symmetric] lt.fresh fresh_at_base)

apply (subgoal_tac "Ka = (n \<leftrightarrow> na) \<bullet> Ka")

apply (subgoal_tac "Ka = (m \<leftrightarrow> ma) \<bullet> Ka")

apply (subgoal_tac "Ka = (n \<leftrightarrow> (m \<leftrightarrow> ma) \<bullet> na) \<bullet> Ka")

apply (case_tac "m = ma")

apply simp_all

apply rule

apply (auto simp add: flip_fresh_fresh[symmetric])

apply (metis flip_at_base_simps(3) flip_fresh_fresh permute_flip_at)+

done

termination

  by (relation "measure (\<lambda>(t, _). size t)") (simp_all add: lt.size)

section{* lemma related to Kapply *}

lemma [simp]: "isValue V \<Longrightarrow> V; K = K $ (V+)"

  by (nominal_induct V rule: lt.strong_induct) auto

section{* lemma related to CPS conversion *}

lemma value_CPS:

  assumes "isValue V"

  and "atom a \<sharp> V"

  shows "V* = Abs a (a~ $ V+)"

  using assms

proof (nominal_induct V avoiding: a rule: lt.strong_induct, simp_all add: lt.fresh)

  fix name :: name and lt aa

  assume a: "atom name \<sharp> aa" "\<And>b. \<lbrakk>isValue lt; atom b \<sharp> lt\<rbrakk> \<Longrightarrow> lt* = Abs b (b~ $ lt+)"

    "atom aa \<sharp> lt \<or> aa = name"

  obtain ab :: name where b: "atom ab \<sharp> (name, lt, a)" using obtain_fresh by blast

  show "Abs name lt* = Abs aa (aa~ $ Abs name (lt*))" using a b

    by (simp add: Abs1_eq_iff fresh_at_base lt.fresh)

qed

section{* first lemma CPS subst *}

lemma CPS_subst_fv:

  assumes *:"isValue V"

  shows "((M[V/x])* = (M*)[V+/x])"

using * proof (nominal_induct M avoiding: V x rule: lt.strong_induct)

  case (Var name)

  assume *: "isValue V"

  obtain a :: name where a: "atom a \<sharp> (x, name, V)" using obtain_fresh by blast

  show "((name~)[V/x])* = (name~)*[V+/x]" using a

    by (simp add: fresh_at_base * value_CPS)

next

  case (Abs name lt V x)

  assume *: "atom name \<sharp> V" "atom name \<sharp> x" "\<And>b ba. isValue b \<Longrightarrow> (lt[b/ba])* = lt*[b+/ba]"

    "isValue V"

  obtain a :: name where a: "atom a \<sharp> (name, lt, lt[V/x], x, V)" using obtain_fresh by blast

  show "(Abs name lt[V/x])* = Abs name lt*[V+/x]" using * a

    by (simp add: fresh_at_base)

next

  case (App lt1 lt2 V x)

  assume *: "\<And>b ba. isValue b \<Longrightarrow> (lt1[b/ba])* = lt1*[b+/ba]" "\<And>b ba. isValue b \<Longrightarrow> (lt2[b/ba])* = lt2*[b+/ba]"

    "isValue V"

  obtain a :: name where a: "atom a \<sharp> (lt1[V/x], lt1, lt2[V/x], lt2, V, x)" using obtain_fresh by blast

  obtain b :: name where b: "atom b \<sharp> (lt2[V/x], lt2, a, V, x)" using obtain_fresh by blast

  obtain c :: name where c: "atom c \<sharp> (a, b, V, x)" using obtain_fresh by blast

  show "((lt1 $ lt2)[V/x])* = (lt1 $ lt2)*[V+/x]" using * a b c

    by (simp add: fresh_at_base)

qed

lemma [simp]: "isValue V \<Longrightarrow> isValue (V+)"

  by (nominal_induct V rule: lt.strong_induct, auto)

lemma CPS_eval_Kapply:

  assumes a: "isValue K"

  shows "(M* $ K) \<longrightarrow>\<^isub>\<beta>\<^sup>* (M ; K)"

  using a

proof (nominal_induct M avoiding: K rule: lt.strong_induct, simp_all)

  case (Var name K)

  assume *: "isValue K"

  obtain a :: name where a: "atom a \<sharp> (name, K)" using obtain_fresh by blast

  show "(name~)* $ K \<longrightarrow>\<^isub>\<beta>\<^sup>* K $ name~" using * a

    by simp (rule evbeta', simp_all add: fresh_at_base)

next

  fix name :: name and lt K

  assume *: "atom name \<sharp> K" "\<And>b. isValue b \<Longrightarrow> lt* $ b \<longrightarrow>\<^isub>\<beta>\<^sup>* lt ; b" "isValue K"

  obtain a :: name where a: "atom a \<sharp> (name, K, lt)" using obtain_fresh by blast

  then have b: "atom name \<sharp> a" using fresh_PairD(1) fresh_at_base atom_eq_iff by metis

  show "Abs name lt* $ K \<longrightarrow>\<^isub>\<beta>\<^sup>* K $ Abs name (lt*)" using * a b

    by simp (rule evbeta', simp_all)

next

  fix lt1 lt2 K

  assume *: "\<And>b. isValue b \<Longrightarrow>  lt1* $ b \<longrightarrow>\<^isub>\<beta>\<^sup>* lt1 ; b" "\<And>b. isValue b \<Longrightarrow>  lt2* $ b \<longrightarrow>\<^isub>\<beta>\<^sup>* lt2 ; b" "isValue K"

  obtain a :: name where a: "atom a \<sharp> (lt1, lt2, K)" using obtain_fresh by blast

  obtain b :: name where b: "atom b \<sharp> (lt1, lt2, K, a)" using obtain_fresh by blast

  obtain c :: name where c: "atom c \<sharp> (lt1, lt2, K, a, b)" using obtain_fresh by blast

  have d: "atom a \<sharp> lt1" "atom a \<sharp> lt2" "atom a \<sharp> K" "atom b \<sharp> lt1" "atom b \<sharp> lt2" "atom b \<sharp> K" "atom b \<sharp> a"

    "atom c \<sharp> lt1" "atom c \<sharp> lt2" "atom c \<sharp> K" "atom c \<sharp> a" "atom c \<sharp> b" using fresh_Pair a b c by simp_all

  have "(lt1 $ lt2)* $ K \<longrightarrow>\<^isub>\<beta>\<^sup>* lt1* $ Abs b (lt2* $ Abs c (b~ $ c~ $ K))" using * d

    by (simp add: fresh_at_base) (rule evbeta', simp_all add: fresh_at_base)

  also have "... \<longrightarrow>\<^isub>\<beta>\<^sup>* lt1 $ lt2 ; K" proof (cases "isValue lt1")

    assume e: "isValue lt1"

    have "lt1* $ Abs b (lt2* $ Abs c (b~ $ c~ $ K)) \<longrightarrow>\<^isub>\<beta>\<^sup>* Abs b (lt2* $ Abs c (b~ $ c~ $ K)) $ lt1+"

      using * d e by simp

    also have "... \<longrightarrow>\<^isub>\<beta>\<^sup>* lt2* $ Abs c (lt1+ $ c~ $ K)"

      by (rule evbeta', simp_all add: * d e, metis d(12) fresh_at_base)

    also have "... \<longrightarrow>\<^isub>\<beta>\<^sup>* lt1 $ lt2 ; K" proof (cases "isValue lt2")

      assume f: "isValue lt2"

      have "lt2* $ Abs c (lt1+ $ c~ $ K) \<longrightarrow>\<^isub>\<beta>\<^sup>* Abs c (lt1+ $ c~ $ K) $ lt2+" using * d e f by simp

      also have "... \<longrightarrow>\<^isub>\<beta>\<^sup>* lt1+ $ lt2+ $ K"

        by (rule evbeta', simp_all add: d e f)

      finally show ?thesis using * d e f by simp

    next

      assume f: "\<not> isValue lt2"

      have "lt2* $ Abs c (lt1+ $ c~ $ K) \<longrightarrow>\<^isub>\<beta>\<^sup>* lt2 ; Abs c (lt1+ $ c~ $ K)" using * d e f by simp

      also have "... \<longrightarrow>\<^isub>\<beta>\<^sup>* lt2 ; Abs a (lt1+ $ a~ $ K)" using Kapply.simps(4) d e evs1 f by metis

      finally show ?thesis using * d e f by simp

    qed

    finally show ?thesis .

  qed (metis Kapply.simps(5) isValue.simps(2) * d)

  finally show "(lt1 $ lt2)* $ K \<longrightarrow>\<^isub>\<beta>\<^sup>* lt1 $ lt2 ; K" .

qed

lemma Kapply_eval:

  assumes a: "M \<longrightarrow>\<^isub>\<beta> N" "isValue K"

  shows "(M; K) \<longrightarrow>\<^isub>\<beta>\<^sup>*  (N; K)"

  using assms

proof (induct arbitrary: K rule: eval.induct)

  case (evbeta x V M)

  fix K

  assume a: "isValue K" "isValue V" "atom x \<sharp> V"

  have "Abs x (M*) $ V+ $ K \<longrightarrow>\<^isub>\<beta>\<^sup>* ((M*)[V+/x] $ K)"

    by (rule evs2,rule ev2,rule Lt.evbeta) (simp_all add: fresh_def a[simplified fresh_def] evs1)

  also have "... = ((M[V/x])* $ K)" by (simp add: CPS_subst_fv a)

  also have "... \<longrightarrow>\<^isub>\<beta>\<^sup>* (M[V/x] ; K)" by (rule CPS_eval_Kapply, simp_all add: a)

  finally show "(Abs x M $ V ; K) \<longrightarrow>\<^isub>\<beta>\<^sup>*  (M[V/x] ; K)" using a by simp

next

  case (ev1 V M N)

  fix V M N K

  assume a: "isValue V" "M \<longrightarrow>\<^isub>\<beta> N" "\<And>K. isValue K \<Longrightarrow> M ; K \<longrightarrow>\<^isub>\<beta>\<^sup>* N ; K" "isValue K"

  obtain a :: name where b: "atom a \<sharp> (V, K, M, N)" using obtain_fresh by blast

  show "V $ M ; K \<longrightarrow>\<^isub>\<beta>\<^sup>* V $ N ; K" proof (cases "isValue N")

    assume "\<not> isValue N"

    then show "V $ M ; K \<longrightarrow>\<^isub>\<beta>\<^sup>* V $ N ; K" using a b by simp

  next

    assume n: "isValue N"

    have c: "M; Abs a (V+ $ a~ $ K) \<longrightarrow>\<^isub>\<beta>\<^sup>* Abs a (V+ $ a~ $ K) $ N+" using a b by (simp add: n)

    also have d: "... \<longrightarrow>\<^isub>\<beta>\<^sup>* V+ $ N+ $ K" by (rule evbeta') (simp_all add: a b n)

    finally show "V $ M ; K \<longrightarrow>\<^isub>\<beta>\<^sup>* V $ N ; K" using a b by (simp add: n)

  qed

next

  case (ev2 M M' N)

  assume *: "M \<longrightarrow>\<^isub>\<beta> M'" "\<And>K. isValue K \<Longrightarrow>  M ; K \<longrightarrow>\<^isub>\<beta>\<^sup>* M' ; K" "isValue K"

  obtain a :: name where a: "atom a \<sharp> (K, M, N, M')" using obtain_fresh by blast

  obtain b :: name where b: "atom b \<sharp> (a, K, M, N, M', N+)" using obtain_fresh by blast

  have d: "atom a \<sharp> K" "atom a \<sharp> M" "atom a \<sharp> N" "atom a \<sharp> M'" "atom b \<sharp> a" "atom b \<sharp> K"

    "atom b \<sharp> M" "atom b \<sharp> N" "atom b \<sharp> M'" using a b fresh_Pair by simp_all

  have "M $ N ; K  \<longrightarrow>\<^isub>\<beta>\<^sup>* M' ; Abs a (N* $ Abs b (a~ $ b~ $ K))" using * d by simp

  also have "... \<longrightarrow>\<^isub>\<beta>\<^sup>* M' $ N ; K" proof (cases "isValue M'")

    assume "\<not> isValue M'"

    then show ?thesis using * d by (simp_all add: evs1)

  next

    assume e: "isValue M'"

    then have "M' ; Abs a (N* $ Abs b (a~ $ b~ $ K)) = Abs a (N* $ Abs b (a~ $ b~ $ K)) $ M'+" by simp

    also have "... \<longrightarrow>\<^isub>\<beta>\<^sup>* (N* $ Abs b (a~ $ b~ $ K))[M'+/a]"

      by (rule evbeta') (simp_all add: fresh_at_base e d)

    also have "... = N* $ Abs b (M'+ $ b~ $ K)" using * d by (simp add: fresh_at_base)

    also have "... \<longrightarrow>\<^isub>\<beta>\<^sup>* M' $ N ; K" proof (cases "isValue N")

      assume f: "isValue N"

      have "N* $ Abs b (M'+ $ b~ $ K) \<longrightarrow>\<^isub>\<beta>\<^sup>* Abs b (M'+ $ b~ $ K) $ N+"

        by (rule eval_trans, rule CPS_eval_Kapply) (simp_all add: d e f * evs1)

      also have "... \<longrightarrow>\<^isub>\<beta>\<^sup>* M' $ N ; K" by (rule evbeta') (simp_all add: d e f evs1)

      finally show ?thesis .

    next

      assume "\<not> isValue N"

      then show ?thesis using d e

        by (metis CPS_eval_Kapply Kapply.simps(4) isValue.simps(2))

    qed

    finally show ?thesis .

  qed

  finally show ?case .

qed

lemma Kapply_eval_rtrancl:

  assumes H: "M \<longrightarrow>\<^isub>\<beta>\<^sup>*  N" and "isValue K"

  shows "(M;K) \<longrightarrow>\<^isub>\<beta>\<^sup>* (N;K)"

  using H

  by (induct) (metis Kapply_eval assms(2) eval_trans evs1)+

lemma

  assumes "isValue V" "M \<longrightarrow>\<^isub>\<beta>\<^sup>* V"

  shows "M* $ (Abs x (x~)) \<longrightarrow>\<^isub>\<beta>\<^sup>* V+"

proof-

  obtain y::name where *: "atom y \<sharp> V" using obtain_fresh by blast

  have e: "Abs x (x~) = Abs y (y~)"

    by (simp add: Abs1_eq_iff lt.fresh fresh_at_base)

  have "M* $ Abs x (x~) \<longrightarrow>\<^isub>\<beta>\<^sup>* M ; Abs x (x~)"

    by(rule CPS_eval_Kapply,simp_all add: assms)

  also have "... \<longrightarrow>\<^isub>\<beta>\<^sup>* (V ; Abs x (x~))" by (rule Kapply_eval_rtrancl, simp_all add: assms)

  also have "... = V ; Abs y (y~)" using e by (simp only:)

  also have "... \<longrightarrow>\<^isub>\<beta>\<^sup>* (V+)" by (simp add: assms, rule evbeta') (simp_all add: assms *)

  finally show "M* $ (Abs x (x~)) \<longrightarrow>\<^isub>\<beta>\<^sup>* (V+)" .

qed

end