header {* CPS transformation of Danvy and Nielsen *}

theory DanvyNielsen

imports Lt

begin

nominal_datatype cpsctxt =

  Hole

| CFun cpsctxt lt

| CArg lt cpsctxt

| CAbs x::name c::cpsctxt bind x in c

nominal_primrec

  fill   :: "cpsctxt \<Rightarrow> lt \<Rightarrow> lt"         ("_<_>" [200, 200] 100)

where

  fill_hole : "Hole<M> = M"

| fill_fun  : "(CFun C N)<M> = (C<M>) $ N"

| fill_arg  : "(CArg N C)<M> = N $ (C<M>)"

| fill_abs  : "atom x \<sharp> M \<Longrightarrow> (CAbs x C)<M> = Abs x (C<M>)"

  unfolding eqvt_def fill_graph_def

  apply perm_simp

  apply auto

  apply (rule_tac y="a" and c="b" in cpsctxt.strong_exhaust)

  apply (auto simp add: fresh_star_def)

  apply (erule Abs_lst1_fcb)

  apply (simp_all add: Abs_fresh_iff)

  apply (erule fresh_eqvt_at)

  apply (simp add: finite_supp)

  apply (simp add: fresh_Pair)

  apply (simp add: eqvt_at_def swap_fresh_fresh)

  done

termination

  by (relation "measure (\<lambda>(x, _). size x)") (auto simp add: cpsctxt.size)

lemma [eqvt]: "p \<bullet> fill c t = fill (p \<bullet> c) (p \<bullet> t)"

  by (nominal_induct c avoiding: t rule: cpsctxt.strong_induct) simp_all

nominal_primrec

  ccomp :: "cpsctxt => cpsctxt => cpsctxt"

where

  "ccomp Hole C  = C"

| "atom x \<sharp> C' \<Longrightarrow> ccomp (CAbs x C) C' = CAbs x (ccomp C C')"

| "ccomp (CArg N C) C' = CArg N (ccomp C C')"

| "ccomp (CFun C N) C'  = CFun (ccomp C C') N"

  unfolding eqvt_def ccomp_graph_def

  apply perm_simp

  apply auto

  apply (rule_tac y="a" and c="b" in cpsctxt.strong_exhaust)

  apply (auto simp add: fresh_star_def)

  apply blast+

  apply (erule Abs_lst1_fcb)

  apply (simp_all add: Abs_fresh_iff)

  apply (erule fresh_eqvt_at)

  apply (simp add: finite_supp)

  apply (simp add: fresh_Pair)

  apply (simp add: eqvt_at_def swap_fresh_fresh)

  done

termination

  by (relation "measure (\<lambda>(x, _). size x)") (auto simp add: cpsctxt.size)

lemma [eqvt]: "p \<bullet> ccomp c c' = ccomp (p \<bullet> c) (p \<bullet> c')"

  by (nominal_induct c avoiding: c' rule: cpsctxt.strong_induct) simp_all

nominal_primrec

    CPSv :: "lt => lt"

and CPS :: "lt => cpsctxt" where

  "CPSv (Var x) = x~"

| "CPS (Var x) = CFun Hole (x~)"

| "atom b \<sharp> M \<Longrightarrow> CPSv (Abs y M) = Abs y (Abs b ((CPS M)<Var b>))"

| "atom b \<sharp> M \<Longrightarrow> CPS (Abs y M) = CFun Hole (Abs y (Abs b ((CPS M)<Var b>)))"

| "CPSv (M $ N) = Abs x (Var x)"

| "isValue M \<Longrightarrow> isValue N \<Longrightarrow> CPS (M $ N) = CArg (CPSv M $ CPSv N) Hole"

| "isValue M \<Longrightarrow> ~isValue N \<Longrightarrow> atom a \<sharp> N \<Longrightarrow> CPS (M $ N) =

     ccomp (CPS N) (CAbs a (CArg (CPSv M $ Var a) Hole))"

| "~isValue M \<Longrightarrow> isValue N \<Longrightarrow> atom a \<sharp> N \<Longrightarrow> CPS (M $ N) =

     ccomp (CPS M) (CAbs a (CArg (Var a $ (CPSv N)) Hole))"

| "~isValue M \<Longrightarrow> ~isValue N \<Longrightarrow> atom a \<sharp> (N, b) \<Longrightarrow> CPS (M $ N) =

     ccomp (CPS M) (CAbs a (ccomp (CPS N) (CAbs b (CArg (Var a $ Var b) Hole))))"

  apply auto

  oops --"The goals seem reasonable"

end