diff -r 5e59af604d4f -r 8161f137b0e9 src/HOLCF/CompactBasis.thy
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOLCF/CompactBasis.thy	Mon Jan 14 19:26:41 2008 +0100
@@ -0,0 +1,686 @@
+(*  Title:      HOLCF/CompactBasis.thy
+    ID:         $Id$
+    Author:     Brian Huffman
+*)
+
+header {* Compact bases of domains *}
+
+theory CompactBasis
+imports Bifinite SetPcpo
+begin
+
+subsection {* Ideals over a preorder *}
+
+locale preorder =
+  fixes r :: "'a::type \<Rightarrow> 'a \<Rightarrow> bool"
+  assumes refl: "r x x"
+  assumes trans: "\<lbrakk>r x y; r y z\<rbrakk> \<Longrightarrow> r x z"
+begin
+
+definition
+  ideal :: "'a set \<Rightarrow> bool" where
+  "ideal A = ((\<exists>x. x \<in> A) \<and> (\<forall>x\<in>A. \<forall>y\<in>A. \<exists>z\<in>A. r x z \<and> r y z) \<and>
+    (\<forall>x y. r x y \<longrightarrow> y \<in> A \<longrightarrow> x \<in> A))"
+
+lemma idealI:
+  assumes "\<exists>x. x \<in> A"
+  assumes "\<And>x y. \<lbrakk>x \<in> A; y \<in> A\<rbrakk> \<Longrightarrow> \<exists>z\<in>A. r x z \<and> r y z"
+  assumes "\<And>x y. \<lbrakk>r x y; y \<in> A\<rbrakk> \<Longrightarrow> x \<in> A"
+  shows "ideal A"
+unfolding ideal_def using prems by fast
+
+lemma idealD1:
+  "ideal A \<Longrightarrow> \<exists>x. x \<in> A"
+unfolding ideal_def by fast
+
+lemma idealD2:
+  "\<lbrakk>ideal A; x \<in> A; y \<in> A\<rbrakk> \<Longrightarrow> \<exists>z\<in>A. r x z \<and> r y z"
+unfolding ideal_def by fast
+
+lemma idealD3:
+  "\<lbrakk>ideal A; r x y; y \<in> A\<rbrakk> \<Longrightarrow> x \<in> A"
+unfolding ideal_def by fast
+
+lemma ideal_directed_finite:
+  assumes A: "ideal A"
+  shows "\<lbrakk>finite U; U \<subseteq> A\<rbrakk> \<Longrightarrow> \<exists>z\<in>A. \<forall>x\<in>U. r x z"
+apply (induct U set: finite)
+apply (simp add: idealD1 [OF A])
+apply (simp, clarify, rename_tac y)
+apply (drule (1) idealD2 [OF A])
+apply (clarify, erule_tac x=z in rev_bexI)
+apply (fast intro: trans)
+done
+
+lemma ideal_principal: "ideal {x. r x z}"
+apply (rule idealI)
+apply (rule_tac x=z in exI)
+apply (fast intro: refl)
+apply (rule_tac x=z in bexI, fast)
+apply (fast intro: refl)
+apply (fast intro: trans)
+done
+
+lemma directed_image_ideal:
+  assumes A: "ideal A"
+  assumes f: "\<And>x y. r x y \<Longrightarrow> f x \<sqsubseteq> f y"
+  shows "directed (f ` A)"
+apply (rule directedI)
+apply (cut_tac idealD1 [OF A], fast)
+apply (clarify, rename_tac a b)
+apply (drule (1) idealD2 [OF A])
+apply (clarify, rename_tac c)
+apply (rule_tac x="f c" in rev_bexI)
+apply (erule imageI)
+apply (simp add: f)
+done
+
+lemma adm_ideal: "adm (\<lambda>A. ideal A)"
+unfolding ideal_def by (intro adm_lemmas adm_set_lemmas)
+
+end
+
+subsection {* Defining functions in terms of basis elements *}
+
+lemma (in preorder) lub_image_principal:
+  assumes f: "\<And>x y. r x y \<Longrightarrow> f x \<sqsubseteq> f y"
+  shows "(\<Squnion>x\<in>{x. r x y}. f x) = f y"
+apply (rule thelubI)
+apply (rule is_lub_maximal)
+apply (rule ub_imageI)
+apply (simp add: f)
+apply (rule imageI)
+apply (simp add: refl)
+done
+
+lemma finite_directed_has_lub: "\<lbrakk>finite S; directed S\<rbrakk> \<Longrightarrow> \<exists>u. S <<| u"
+apply (drule (1) directed_finiteD, rule subset_refl)
+apply (erule bexE)
+apply (rule_tac x=z in exI)
+apply (erule (1) is_lub_maximal)
+done
+
+lemma is_ub_thelub0: "\<lbrakk>\<exists>u. S <<| u; x \<in> S\<rbrakk> \<Longrightarrow> x \<sqsubseteq> lub S"
+apply (erule exE, drule lubI)
+apply (drule is_lubD1)
+apply (erule (1) is_ubD)
+done
+
+lemma is_lub_thelub0: "\<lbrakk>\<exists>u. S <<| u; S <| x\<rbrakk> \<Longrightarrow> lub S \<sqsubseteq> x"
+by (erule exE, drule lubI, erule is_lub_lub)
+
+locale bifinite_basis = preorder +
+  fixes principal :: "'a::type \<Rightarrow> 'b::cpo"
+  fixes approxes :: "'b::cpo \<Rightarrow> 'a::type set"
+  assumes ideal_approxes: "\<And>x. preorder.ideal r (approxes x)"
+  assumes cont_approxes: "cont approxes"
+  assumes approxes_principal: "\<And>a. approxes (principal a) = {b. r b a}"
+  assumes subset_approxesD: "\<And>x y. approxes x \<subseteq> approxes y \<Longrightarrow> x \<sqsubseteq> y"
+
+  fixes take :: "nat \<Rightarrow> 'a::type \<Rightarrow> 'a"
+  assumes take_less: "r (take n a) a"
+  assumes take_take: "take n (take n a) = take n a"
+  assumes take_mono: "r a b \<Longrightarrow> r (take n a) (take n b)"
+  assumes take_chain: "r (take n a) (take (Suc n) a)"
+  assumes finite_range_take: "finite (range (take n))"
+  assumes take_covers: "\<exists>n. take n a = a"
+begin
+
+lemma finite_take_approxes: "finite (take n ` approxes x)"
+by (rule finite_subset [OF image_mono [OF subset_UNIV] finite_range_take])
+
+lemma basis_fun_lemma0:
+  fixes f :: "'a::type \<Rightarrow> 'c::cpo"
+  assumes f_mono: "\<And>a b. r a b \<Longrightarrow> f a \<sqsubseteq> f b"
+  shows "\<exists>u. f ` take i ` approxes x <<| u"
+apply (rule finite_directed_has_lub)
+apply (rule finite_imageI)
+apply (rule finite_take_approxes)
+apply (subst image_image)
+apply (rule directed_image_ideal)
+apply (rule ideal_approxes)
+apply (rule f_mono)
+apply (erule take_mono)
+done
+
+lemma basis_fun_lemma1:
+  fixes f :: "'a::type \<Rightarrow> 'c::cpo"
+  assumes f_mono: "\<And>a b. r a b \<Longrightarrow> f a \<sqsubseteq> f b"
+  shows "chain (\<lambda>i. lub (f ` take i ` approxes x))"
+ apply (rule chainI)
+ apply (rule is_lub_thelub0)
+  apply (rule basis_fun_lemma0, erule f_mono)
+ apply (rule is_ubI, clarsimp, rename_tac a)
+ apply (rule trans_less [OF f_mono [OF take_chain]])
+ apply (rule is_ub_thelub0)
+  apply (rule basis_fun_lemma0, erule f_mono)
+ apply simp
+done
+
+lemma basis_fun_lemma2:
+  fixes f :: "'a::type \<Rightarrow> 'c::cpo"
+  assumes f_mono: "\<And>a b. r a b \<Longrightarrow> f a \<sqsubseteq> f b"
+  shows "f ` approxes x <<| (\<Squnion>i. lub (f ` take i ` approxes x))"
+ apply (rule is_lubI)
+ apply (rule ub_imageI, rename_tac a)
+  apply (cut_tac a=a in take_covers, erule exE, rename_tac i)
+  apply (erule subst)
+  apply (rule rev_trans_less)
+   apply (rule_tac x=i in is_ub_thelub)
+   apply (rule basis_fun_lemma1, erule f_mono)
+  apply (rule is_ub_thelub0)
+   apply (rule basis_fun_lemma0, erule f_mono)
+  apply simp
+ apply (rule is_lub_thelub [OF _ ub_rangeI])
+  apply (rule basis_fun_lemma1, erule f_mono)
+ apply (rule is_lub_thelub0)
+  apply (rule basis_fun_lemma0, erule f_mono)
+ apply (rule is_ubI, clarsimp, rename_tac a)
+ apply (rule trans_less [OF f_mono [OF take_less]])
+ apply (erule (1) ub_imageD)
+done
+
+lemma basis_fun_lemma:
+  fixes f :: "'a::type \<Rightarrow> 'c::cpo"
+  assumes f_mono: "\<And>a b. r a b \<Longrightarrow> f a \<sqsubseteq> f b"
+  shows "\<exists>u. f ` approxes x <<| u"
+by (rule exI, rule basis_fun_lemma2, erule f_mono)
+
+lemma approxes_mono: "x \<sqsubseteq> y \<Longrightarrow> approxes x \<subseteq> approxes y"
+apply (drule cont_approxes [THEN cont2mono, THEN monofunE])
+apply (simp add: set_cpo_simps)
+done
+
+lemma approxes_contlub:
+  "chain Y \<Longrightarrow> approxes (\<Squnion>i. Y i) = (\<Union>i. approxes (Y i))"
+by (simp add: cont2contlubE [OF cont_approxes] set_cpo_simps)
+
+lemma less_def: "(x \<sqsubseteq> y) = (approxes x \<subseteq> approxes y)"
+by (rule iffI [OF approxes_mono subset_approxesD])
+
+lemma approxes_eq: "approxes x = {a. principal a \<sqsubseteq> x}"
+unfolding less_def approxes_principal
+apply safe
+apply (erule (1) idealD3 [OF ideal_approxes])
+apply (erule subsetD, simp add: refl)
+done
+
+lemma mem_approxes_iff: "(a \<in> approxes x) = (principal a \<sqsubseteq> x)"
+by (simp add: approxes_eq)
+
+lemma principal_less_iff: "(principal a \<sqsubseteq> x) = (a \<in> approxes x)"
+by (simp add: approxes_eq)
+
+lemma approxesD: "a \<in> approxes x \<Longrightarrow> principal a \<sqsubseteq> x"
+by (simp add: approxes_eq)
+
+lemma principal_mono: "r a b \<Longrightarrow> principal a \<sqsubseteq> principal b"
+by (rule approxesD, simp add: approxes_principal)
+
+lemma lessI: "(\<And>a. principal a \<sqsubseteq> x \<Longrightarrow> principal a \<sqsubseteq> u) \<Longrightarrow> x \<sqsubseteq> u"
+unfolding principal_less_iff
+by (simp add: less_def subset_def)
+
+lemma lub_principal_approxes: "principal ` approxes x <<| x"
+apply (rule is_lubI)
+apply (rule ub_imageI)
+apply (erule approxesD)
+apply (subst less_def)
+apply (rule subsetI)
+apply (drule (1) ub_imageD)
+apply (simp add: approxes_eq)
+done
+
+definition
+  basis_fun :: "('a::type \<Rightarrow> 'c::cpo) \<Rightarrow> 'b \<rightarrow> 'c" where
+  "basis_fun = (\<lambda>f. (\<Lambda> x. lub (f ` approxes x)))"
+
+lemma basis_fun_beta:
+  fixes f :: "'a::type \<Rightarrow> 'c::cpo"
+  assumes f_mono: "\<And>a b. r a b \<Longrightarrow> f a \<sqsubseteq> f b"
+  shows "basis_fun f\<cdot>x = lub (f ` approxes x)"
+unfolding basis_fun_def
+proof (rule beta_cfun)
+  have lub: "\<And>x. \<exists>u. f ` approxes x <<| u"
+    using f_mono by (rule basis_fun_lemma)
+  show cont: "cont (\<lambda>x. lub (f ` approxes x))"
+    apply (rule contI2)
+     apply (rule monofunI)
+     apply (rule is_lub_thelub0 [OF lub ub_imageI])
+     apply (rule is_ub_thelub0 [OF lub imageI])
+     apply (erule (1) subsetD [OF approxes_mono])
+    apply (rule is_lub_thelub0 [OF lub ub_imageI])
+    apply (simp add: approxes_contlub, clarify)
+    apply (erule rev_trans_less [OF is_ub_thelub])
+    apply (erule is_ub_thelub0 [OF lub imageI])
+    done
+qed
+
+lemma basis_fun_principal:
+  fixes f :: "'a::type \<Rightarrow> 'c::cpo"
+  assumes f_mono: "\<And>a b. r a b \<Longrightarrow> f a \<sqsubseteq> f b"
+  shows "basis_fun f\<cdot>(principal a) = f a"
+apply (subst basis_fun_beta, erule f_mono)
+apply (subst approxes_principal)
+apply (rule lub_image_principal, erule f_mono)
+done
+
+lemma basis_fun_mono:
+  assumes f_mono: "\<And>a b. r a b \<Longrightarrow> f a \<sqsubseteq> f b"
+  assumes g_mono: "\<And>a b. r a b \<Longrightarrow> g a \<sqsubseteq> g b"
+  assumes less: "\<And>a. f a \<sqsubseteq> g a"
+  shows "basis_fun f \<sqsubseteq> basis_fun g"
+ apply (rule less_cfun_ext)
+ apply (simp only: basis_fun_beta f_mono g_mono)
+ apply (rule is_lub_thelub0)
+  apply (rule basis_fun_lemma, erule f_mono)
+ apply (rule ub_imageI, rename_tac a)
+ apply (rule trans_less [OF less])
+ apply (rule is_ub_thelub0)
+  apply (rule basis_fun_lemma, erule g_mono)
+ apply (erule imageI)
+done
+
+lemma compact_principal: "compact (principal a)"
+by (rule compactI2, simp add: principal_less_iff approxes_contlub)
+
+lemma chain_basis_fun_take:
+  "chain (\<lambda>i. basis_fun (\<lambda>a. principal (take i a)))"
+apply (rule chainI)
+apply (rule basis_fun_mono)
+apply (erule principal_mono [OF take_mono])
+apply (erule principal_mono [OF take_mono])
+apply (rule principal_mono [OF take_chain])
+done
+
+lemma lub_basis_fun_take:
+  "(\<Squnion>i. basis_fun (\<lambda>a. principal (take i a))\<cdot>x) = x"
+ apply (simp add: basis_fun_beta principal_mono take_mono)
+ apply (subst image_image [where f=principal, symmetric])
+ apply (rule unique_lub [OF _ lub_principal_approxes])
+ apply (rule basis_fun_lemma2, erule principal_mono)
+done
+
+lemma finite_directed_contains_lub:
+  "\<lbrakk>finite S; directed S\<rbrakk> \<Longrightarrow> \<exists>u\<in>S. S <<| u"
+apply (drule (1) directed_finiteD, rule subset_refl)
+apply (erule bexE)
+apply (rule rev_bexI, assumption)
+apply (erule (1) is_lub_maximal)
+done
+
+lemma lub_finite_directed_in_self:
+  "\<lbrakk>finite S; directed S\<rbrakk> \<Longrightarrow> lub S \<in> S"
+apply (drule (1) directed_finiteD, rule subset_refl)
+apply (erule bexE)
+apply (drule (1) is_lub_maximal)
+apply (drule thelubI)
+apply simp
+done
+
+lemma basis_fun_take_eq_principal:
+  "\<exists>a\<in>approxes x.
+    basis_fun (\<lambda>a. principal (take i a))\<cdot>x = principal (take i a)"
+ apply (simp add: basis_fun_beta principal_mono take_mono)
+ apply (subst image_image [where f=principal, symmetric])
+ apply (subgoal_tac "finite (principal ` take i ` approxes x)")
+  apply (subgoal_tac "directed (principal ` take i ` approxes x)")
+   apply (drule (1) lub_finite_directed_in_self, fast)
+  apply (subst image_image)
+  apply (rule directed_image_ideal)
+   apply (rule ideal_approxes)
+  apply (erule principal_mono [OF take_mono])
+ apply (rule finite_imageI)
+ apply (rule finite_take_approxes)
+done
+
+lemma principal_induct:
+  assumes adm: "adm P"
+  assumes P: "\<And>a. P (principal a)"
+  shows "P x"
+ apply (subgoal_tac "P (\<Squnion>i. basis_fun (\<lambda>a. principal (take i a))\<cdot>x)")
+ apply (simp add: lub_basis_fun_take)
+ apply (rule admD [rule_format, OF adm])
+  apply (simp add: chain_basis_fun_take)
+ apply (cut_tac x=x and i=i in basis_fun_take_eq_principal)
+ apply (clarify, simp add: P)
+done
+
+lemma finite_fixes_basis_fun_take:
+  "finite {x. basis_fun (\<lambda>a. principal (take i a))\<cdot>x = x}" (is "finite ?S")
+apply (subgoal_tac "?S \<subseteq> principal ` range (take i)")
+apply (erule finite_subset)
+apply (rule finite_imageI)
+apply (rule finite_range_take)
+apply (clarify, erule subst)
+apply (cut_tac x=x and i=i in basis_fun_take_eq_principal)
+apply fast
+done
+
+end
+
+
+subsection {* Compact bases of bifinite domains *}
+
+defaultsort bifinite
+
+typedef (open) 'a compact_basis = "{x::'a::bifinite. compact x}"
+by (fast intro: compact_approx)
+
+lemma compact_Rep_compact_basis [simp]: "compact (Rep_compact_basis a)"
+by (rule Rep_compact_basis [simplified])
+
+lemma Rep_Abs_compact_basis_approx [simp]:
+  "Rep_compact_basis (Abs_compact_basis (approx n\<cdot>x)) = approx n\<cdot>x"
+by (rule Abs_compact_basis_inverse, simp)
+
+lemma compact_imp_Rep_compact_basis:
+  "compact x \<Longrightarrow> \<exists>y. x = Rep_compact_basis y"
+by (rule exI, rule Abs_compact_basis_inverse [symmetric], simp)
+
+definition
+  compact_le :: "'a compact_basis \<Rightarrow> 'a compact_basis \<Rightarrow> bool" where
+  "compact_le = (\<lambda>x y. Rep_compact_basis x \<sqsubseteq> Rep_compact_basis y)"
+
+lemma compact_le_refl: "compact_le x x"
+unfolding compact_le_def by (rule refl_less)
+
+lemma compact_le_trans: "\<lbrakk>compact_le x y; compact_le y z\<rbrakk> \<Longrightarrow> compact_le x z"
+unfolding compact_le_def by (rule trans_less)
+
+lemma compact_le_antisym: "\<lbrakk>compact_le x y; compact_le y x\<rbrakk> \<Longrightarrow> x = y"
+unfolding compact_le_def
+apply (rule Rep_compact_basis_inject [THEN iffD1])
+apply (erule (1) antisym_less)
+done
+
+interpretation compact_le: preorder [compact_le]
+by (rule preorder.intro, rule compact_le_refl, rule compact_le_trans)
+
+text {* minimal compact element *}
+
+definition
+  compact_bot :: "'a compact_basis" where
+  "compact_bot = Abs_compact_basis \<bottom>"
+
+lemma Rep_compact_bot: "Rep_compact_basis compact_bot = \<bottom>"
+unfolding compact_bot_def by (simp add: Abs_compact_basis_inverse)
+
+lemma compact_minimal [simp]: "compact_le compact_bot a"
+unfolding compact_le_def Rep_compact_bot by simp
+
+text {* compacts *}
+
+definition
+  compacts :: "'a \<Rightarrow> 'a compact_basis set" where
+  "compacts = (\<lambda>x. {a. Rep_compact_basis a \<sqsubseteq> x})"
+
+lemma ideal_compacts: "compact_le.ideal (compacts w)"
+unfolding compacts_def
+ apply (rule compact_le.idealI)
+   apply (rule_tac x="Abs_compact_basis (approx 0\<cdot>w)" in exI)
+   apply (simp add: approx_less)
+  apply simp
+  apply (cut_tac a=x in compact_Rep_compact_basis)
+  apply (cut_tac a=y in compact_Rep_compact_basis)
+  apply (drule bifinite_compact_eq_approx)
+  apply (drule bifinite_compact_eq_approx)
+  apply (clarify, rename_tac i j)
+  apply (rule_tac x="Abs_compact_basis (approx (max i j)\<cdot>w)" in exI)
+  apply (simp add: approx_less compact_le_def)
+  apply (erule subst, erule subst)
+  apply (simp add: monofun_cfun chain_mono3 [OF chain_approx])
+ apply (simp add: compact_le_def)
+ apply (erule (1) trans_less)
+done
+
+lemma compacts_Rep_compact_basis:
+  "compacts (Rep_compact_basis b) = {a. compact_le a b}"
+unfolding compacts_def compact_le_def ..
+
+lemma cont_compacts: "cont compacts"
+unfolding compacts_def
+apply (rule contI2)
+apply (rule monofunI)
+apply (simp add: set_cpo_simps)
+apply (fast intro: trans_less)
+apply (simp add: set_cpo_simps)
+apply clarify
+apply simp
+apply (erule (1) compactD2 [OF compact_Rep_compact_basis])
+done
+
+lemma compacts_lessD: "compacts x \<subseteq> compacts y \<Longrightarrow> x \<sqsubseteq> y"
+apply (subgoal_tac "(\<Squnion>i. approx i\<cdot>x) \<sqsubseteq> y", simp)
+apply (rule admD [rule_format], simp, simp)
+apply (drule_tac c="Abs_compact_basis (approx i\<cdot>x)" in subsetD)
+apply (simp add: compacts_def Abs_compact_basis_inverse approx_less)
+apply (simp add: compacts_def Abs_compact_basis_inverse)
+done
+
+lemma compacts_mono: "x \<sqsubseteq> y \<Longrightarrow> compacts x \<subseteq> compacts y"
+unfolding compacts_def by (fast intro: trans_less)
+
+lemma less_compact_basis_iff: "(x \<sqsubseteq> y) = (compacts x \<subseteq> compacts y)"
+by (rule iffI [OF compacts_mono compacts_lessD])
+
+lemma compact_basis_induct:
+  "\<lbrakk>adm P; \<And>a. P (Rep_compact_basis a)\<rbrakk> \<Longrightarrow> P x"
+apply (erule approx_induct)
+apply (drule_tac x="Abs_compact_basis (approx n\<cdot>x)" in meta_spec)
+apply (simp add: Abs_compact_basis_inverse)
+done
+
+text {* approximation on compact bases *}
+
+definition
+  compact_approx :: "nat \<Rightarrow> 'a compact_basis \<Rightarrow> 'a compact_basis" where
+  "compact_approx = (\<lambda>n a. Abs_compact_basis (approx n\<cdot>(Rep_compact_basis a)))"
+
+lemma Rep_compact_approx:
+  "Rep_compact_basis (compact_approx n a) = approx n\<cdot>(Rep_compact_basis a)"
+unfolding compact_approx_def
+by (simp add: Abs_compact_basis_inverse)
+
+lemmas approx_Rep_compact_basis = Rep_compact_approx [symmetric]
+
+lemma compact_approx_le:
+  "compact_le (compact_approx n a) a"
+unfolding compact_le_def
+by (simp add: Rep_compact_approx approx_less)
+
+lemma compact_approx_mono1:
+  "i \<le> j \<Longrightarrow> compact_le (compact_approx i a) (compact_approx j a)"
+unfolding compact_le_def
+apply (simp add: Rep_compact_approx)
+apply (rule chain_mono3, simp, assumption)
+done
+
+lemma compact_approx_mono:
+  "compact_le a b \<Longrightarrow> compact_le (compact_approx n a) (compact_approx n b)"
+unfolding compact_le_def
+apply (simp add: Rep_compact_approx)
+apply (erule monofun_cfun_arg)
+done
+
+lemma ex_compact_approx_eq: "\<exists>n. compact_approx n a = a"
+apply (simp add: Rep_compact_basis_inject [symmetric])
+apply (simp add: Rep_compact_approx)
+apply (rule bifinite_compact_eq_approx)
+apply (rule compact_Rep_compact_basis)
+done
+
+lemma compact_approx_idem:
+  "compact_approx n (compact_approx n a) = compact_approx n a"
+apply (rule Rep_compact_basis_inject [THEN iffD1])
+apply (simp add: Rep_compact_approx)
+done
+
+lemma finite_fixes_compact_approx: "finite {a. compact_approx n a = a}"
+apply (subgoal_tac "finite (Rep_compact_basis ` {a. compact_approx n a = a})")
+apply (erule finite_imageD)
+apply (rule inj_onI, simp add: Rep_compact_basis_inject)
+apply (rule finite_subset [OF _ finite_fixes_approx [where i=n]])
+apply (rule subsetI, clarify, rename_tac a)
+apply (simp add: Rep_compact_basis_inject [symmetric])
+apply (simp add: Rep_compact_approx)
+done
+
+lemma finite_range_compact_approx: "finite (range (compact_approx n))"
+apply (cut_tac n=n in finite_fixes_compact_approx)
+apply (simp add: idem_fixes_eq_range compact_approx_idem)
+apply (simp add: image_def)
+done
+
+interpretation compact_basis:
+  bifinite_basis [compact_le Rep_compact_basis compacts compact_approx]
+apply unfold_locales
+apply (rule ideal_compacts)
+apply (rule cont_compacts)
+apply (rule compacts_Rep_compact_basis)
+apply (erule compacts_lessD)
+apply (rule compact_approx_le)
+apply (rule compact_approx_idem)
+apply (erule compact_approx_mono)
+apply (rule compact_approx_mono1, simp)
+apply (rule finite_range_compact_approx)
+apply (rule ex_compact_approx_eq)
+done
+
+
+subsection {* A compact basis for powerdomains *}
+
+typedef 'a pd_basis =
+  "{S::'a::bifinite compact_basis set. finite S \<and> S \<noteq> {}}"
+by (rule_tac x="{arbitrary}" in exI, simp)
+
+lemma finite_Rep_pd_basis [simp]: "finite (Rep_pd_basis u)"
+by (insert Rep_pd_basis [of u, unfolded pd_basis_def]) simp
+
+lemma Rep_pd_basis_nonempty [simp]: "Rep_pd_basis u \<noteq> {}"
+by (insert Rep_pd_basis [of u, unfolded pd_basis_def]) simp
+
+text {* unit and plus *}
+
+definition
+  PDUnit :: "'a compact_basis \<Rightarrow> 'a pd_basis" where
+  "PDUnit = (\<lambda>x. Abs_pd_basis {x})"
+
+definition
+  PDPlus :: "'a pd_basis \<Rightarrow> 'a pd_basis \<Rightarrow> 'a pd_basis" where
+  "PDPlus t u = Abs_pd_basis (Rep_pd_basis t \<union> Rep_pd_basis u)"
+
+lemma Rep_PDUnit:
+  "Rep_pd_basis (PDUnit x) = {x}"
+unfolding PDUnit_def by (rule Abs_pd_basis_inverse) (simp add: pd_basis_def)
+
+lemma Rep_PDPlus:
+  "Rep_pd_basis (PDPlus u v) = Rep_pd_basis u \<union> Rep_pd_basis v"
+unfolding PDPlus_def by (rule Abs_pd_basis_inverse) (simp add: pd_basis_def)
+
+lemma PDUnit_inject [simp]: "(PDUnit a = PDUnit b) = (a = b)"
+unfolding Rep_pd_basis_inject [symmetric] Rep_PDUnit by simp
+
+lemma PDPlus_assoc: "PDPlus (PDPlus t u) v = PDPlus t (PDPlus u v)"
+unfolding Rep_pd_basis_inject [symmetric] Rep_PDPlus by (rule Un_assoc)
+
+lemma PDPlus_commute: "PDPlus t u = PDPlus u t"
+unfolding Rep_pd_basis_inject [symmetric] Rep_PDPlus by (rule Un_commute)
+
+lemma PDPlus_absorb: "PDPlus t t = t"
+unfolding Rep_pd_basis_inject [symmetric] Rep_PDPlus by (rule Un_absorb)
+
+lemma pd_basis_induct1:
+  assumes PDUnit: "\<And>a. P (PDUnit a)"
+  assumes PDPlus: "\<And>a t. P t \<Longrightarrow> P (PDPlus (PDUnit a) t)"
+  shows "P x"
+apply (induct x, unfold pd_basis_def, clarify)
+apply (erule (1) finite_ne_induct)
+apply (cut_tac a=x in PDUnit)
+apply (simp add: PDUnit_def)
+apply (drule_tac a=x in PDPlus)
+apply (simp add: PDUnit_def PDPlus_def Abs_pd_basis_inverse [unfolded pd_basis_def])
+done
+
+lemma pd_basis_induct:
+  assumes PDUnit: "\<And>a. P (PDUnit a)"
+  assumes PDPlus: "\<And>t u. \<lbrakk>P t; P u\<rbrakk> \<Longrightarrow> P (PDPlus t u)"
+  shows "P x"
+apply (induct x rule: pd_basis_induct1)
+apply (rule PDUnit, erule PDPlus [OF PDUnit])
+done
+
+text {* fold-pd *}
+
+definition
+  fold_pd ::
+    "('a compact_basis \<Rightarrow> 'b::type) \<Rightarrow> ('b \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'a pd_basis \<Rightarrow> 'b"
+  where "fold_pd g f t = fold1 f (g ` Rep_pd_basis t)"
+
+lemma (in ACIf) fold_pd_PDUnit:
+  "fold_pd g f (PDUnit x) = g x"
+unfolding fold_pd_def Rep_PDUnit by simp
+
+lemma (in ACIf) fold_pd_PDPlus:
+  "fold_pd g f (PDPlus t u) = f (fold_pd g f t) (fold_pd g f u)"
+unfolding fold_pd_def Rep_PDPlus by (simp add: image_Un fold1_Un2)
+
+text {* approx-pd *}
+
+definition
+  approx_pd :: "nat \<Rightarrow> 'a pd_basis \<Rightarrow> 'a pd_basis" where
+  "approx_pd n = (\<lambda>t. Abs_pd_basis (compact_approx n ` Rep_pd_basis t))"
+
+lemma Rep_approx_pd:
+  "Rep_pd_basis (approx_pd n t) = compact_approx n ` Rep_pd_basis t"
+unfolding approx_pd_def
+apply (rule Abs_pd_basis_inverse)
+apply (simp add: pd_basis_def)
+done
+
+lemma approx_pd_simps [simp]:
+  "approx_pd n (PDUnit a) = PDUnit (compact_approx n a)"
+  "approx_pd n (PDPlus t u) = PDPlus (approx_pd n t) (approx_pd n u)"
+apply (simp_all add: Rep_pd_basis_inject [symmetric])
+apply (simp_all add: Rep_approx_pd Rep_PDUnit Rep_PDPlus image_Un)
+done
+
+lemma approx_pd_idem: "approx_pd n (approx_pd n t) = approx_pd n t"
+apply (induct t rule: pd_basis_induct)
+apply (simp add: compact_approx_idem)
+apply simp
+done
+
+lemma range_image_f: "range (image f) = Pow (range f)"
+apply (safe, fast)
+apply (rule_tac x="f -` x" in range_eqI)
+apply (simp, fast)
+done
+
+lemma finite_range_approx_pd: "finite (range (approx_pd n))"
+apply (subgoal_tac "finite (Rep_pd_basis ` range (approx_pd n))")
+apply (erule finite_imageD)
+apply (rule inj_onI, simp add: Rep_pd_basis_inject)
+apply (subst image_image)
+apply (subst Rep_approx_pd)
+apply (simp only: range_composition)
+apply (rule finite_subset [OF image_mono [OF subset_UNIV]])
+apply (simp add: range_image_f)
+apply (rule finite_range_compact_approx)
+done
+
+lemma ex_approx_pd_eq: "\<exists>n. approx_pd n t = t"
+apply (subgoal_tac "\<exists>n. \<forall>m\<ge>n. approx_pd m t = t", fast)
+apply (induct t rule: pd_basis_induct)
+apply (cut_tac a=a in ex_compact_approx_eq)
+apply (clarify, rule_tac x=n in exI)
+apply (clarify, simp)
+apply (rule compact_le_antisym)
+apply (rule compact_approx_le)
+apply (drule_tac a=a in compact_approx_mono1)
+apply simp
+apply (clarify, rename_tac i j)
+apply (rule_tac x="max i j" in exI, simp)
+done
+
+end