header {* The type of lifted values *}
theory Up
imports Bifinite
begin
defaultsort cpo
subsection {* Definition of new type for lifting *}
datatype 'a u = Ibottom | Iup 'a
syntax (xsymbols)
"u" :: "type => type" ("(_⊥)" [1000] 999)
consts
Ifup :: "('a -> 'b::pcpo) => 'a u => 'b"
primrec
"Ifup f Ibottom = ⊥"
"Ifup f (Iup x) = f·x"
subsection {* Ordering on lifted cpo *}
instantiation u :: (cpo) sq_ord
begin
definition
less_up_def:
"(op \<sqsubseteq>) ≡ (λx y. case x of Ibottom => True | Iup a =>
(case y of Ibottom => False | Iup b => a \<sqsubseteq> b))"
instance ..
end
lemma minimal_up [iff]: "Ibottom \<sqsubseteq> z"
by (simp add: less_up_def)
lemma not_Iup_less [iff]: "¬ Iup x \<sqsubseteq> Ibottom"
by (simp add: less_up_def)
lemma Iup_less [iff]: "(Iup x \<sqsubseteq> Iup y) = (x \<sqsubseteq> y)"
by (simp add: less_up_def)
subsection {* Lifted cpo is a partial order *}
instance u :: (cpo) po
proof
fix x :: "'a u"
show "x \<sqsubseteq> x"
unfolding less_up_def by (simp split: u.split)
next
fix x y :: "'a u"
assume "x \<sqsubseteq> y" "y \<sqsubseteq> x" thus "x = y"
unfolding less_up_def
by (auto split: u.split_asm intro: antisym_less)
next
fix x y z :: "'a u"
assume "x \<sqsubseteq> y" "y \<sqsubseteq> z" thus "x \<sqsubseteq> z"
unfolding less_up_def
by (auto split: u.split_asm intro: trans_less)
qed
lemma u_UNIV: "UNIV = insert Ibottom (range Iup)"
by (auto, case_tac x, auto)
instance u :: (finite_po) finite_po
by (intro_classes, simp add: u_UNIV)
subsection {* Lifted cpo is a cpo *}
lemma is_lub_Iup:
"range S <<| x ==> range (λi. Iup (S i)) <<| Iup x"
apply (rule is_lubI)
apply (rule ub_rangeI)
apply (subst Iup_less)
apply (erule is_ub_lub)
apply (case_tac u)
apply (drule ub_rangeD)
apply simp
apply simp
apply (erule is_lub_lub)
apply (rule ub_rangeI)
apply (drule_tac i=i in ub_rangeD)
apply simp
done
text {* Now some lemmas about chains of @{typ "'a u"} elements *}
lemma up_lemma1: "z ≠ Ibottom ==> Iup (THE a. Iup a = z) = z"
by (case_tac z, simp_all)
lemma up_lemma2:
"[|chain Y; Y j ≠ Ibottom|] ==> Y (i + j) ≠ Ibottom"
apply (erule contrapos_nn)
apply (drule_tac i="j" and j="i + j" in chain_mono)
apply (rule le_add2)
apply (case_tac "Y j")
apply assumption
apply simp
done
lemma up_lemma3:
"[|chain Y; Y j ≠ Ibottom|] ==> Iup (THE a. Iup a = Y (i + j)) = Y (i + j)"
by (rule up_lemma1 [OF up_lemma2])
lemma up_lemma4:
"[|chain Y; Y j ≠ Ibottom|] ==> chain (λi. THE a. Iup a = Y (i + j))"
apply (rule chainI)
apply (rule Iup_less [THEN iffD1])
apply (subst up_lemma3, assumption+)+
apply (simp add: chainE)
done
lemma up_lemma5:
"[|chain Y; Y j ≠ Ibottom|] ==>
(λi. Y (i + j)) = (λi. Iup (THE a. Iup a = Y (i + j)))"
by (rule ext, rule up_lemma3 [symmetric])
lemma up_lemma6:
"[|chain Y; Y j ≠ Ibottom|]
==> range Y <<| Iup (\<Squnion>i. THE a. Iup a = Y(i + j))"
apply (rule_tac j1 = j in is_lub_range_shift [THEN iffD1])
apply assumption
apply (subst up_lemma5, assumption+)
apply (rule is_lub_Iup)
apply (rule cpo_lubI)
apply (erule (1) up_lemma4)
done
lemma up_chain_lemma:
"chain Y ==>
(∃A. chain A ∧ (\<Squnion>i. Y i) = Iup (\<Squnion>i. A i) ∧
(∃j. ∀i. Y (i + j) = Iup (A i))) ∨ (Y = (λi. Ibottom))"
apply (rule disjCI)
apply (simp add: expand_fun_eq)
apply (erule exE, rename_tac j)
apply (rule_tac x="λi. THE a. Iup a = Y (i + j)" in exI)
apply (simp add: up_lemma4)
apply (simp add: up_lemma6 [THEN thelubI])
apply (rule_tac x=j in exI)
apply (simp add: up_lemma3)
done
lemma cpo_up: "chain (Y::nat => 'a u) ==> ∃x. range Y <<| x"
apply (frule up_chain_lemma, safe)
apply (rule_tac x="Iup (\<Squnion>i. A i)" in exI)
apply (erule_tac j="j" in is_lub_range_shift [THEN iffD1, standard])
apply (simp add: is_lub_Iup cpo_lubI)
apply (rule exI, rule lub_const)
done
instance u :: (cpo) cpo
by intro_classes (rule cpo_up)
subsection {* Lifted cpo is pointed *}
lemma least_up: "∃x::'a u. ∀y. x \<sqsubseteq> y"
apply (rule_tac x = "Ibottom" in exI)
apply (rule minimal_up [THEN allI])
done
instance u :: (cpo) pcpo
by intro_classes (rule least_up)
text {* for compatibility with old HOLCF-Version *}
lemma inst_up_pcpo: "⊥ = Ibottom"
by (rule minimal_up [THEN UU_I, symmetric])
subsection {* Continuity of @{term Iup} and @{term Ifup} *}
text {* continuity for @{term Iup} *}
lemma cont_Iup: "cont Iup"
apply (rule contI)
apply (rule is_lub_Iup)
apply (erule cpo_lubI)
done
text {* continuity for @{term Ifup} *}
lemma cont_Ifup1: "cont (λf. Ifup f x)"
by (induct x, simp_all)
lemma monofun_Ifup2: "monofun (λx. Ifup f x)"
apply (rule monofunI)
apply (case_tac x, simp)
apply (case_tac y, simp)
apply (simp add: monofun_cfun_arg)
done
lemma cont_Ifup2: "cont (λx. Ifup f x)"
apply (rule contI)
apply (frule up_chain_lemma, safe)
apply (rule_tac j="j" in is_lub_range_shift [THEN iffD1, standard])
apply (erule monofun_Ifup2 [THEN ch2ch_monofun])
apply (simp add: cont_cfun_arg)
apply (simp add: lub_const)
done
subsection {* Continuous versions of constants *}
definition
up :: "'a -> 'a u" where
"up = (Λ x. Iup x)"
definition
fup :: "('a -> 'b::pcpo) -> 'a u -> 'b" where
"fup = (Λ f p. Ifup f p)"
translations
"case l of XCONST up·x => t" == "CONST fup·(Λ x. t)·l"
"Λ(XCONST up·x). t" == "CONST fup·(Λ x. t)"
text {* continuous versions of lemmas for @{typ "('a)u"} *}
lemma Exh_Up: "z = ⊥ ∨ (∃x. z = up·x)"
apply (induct z)
apply (simp add: inst_up_pcpo)
apply (simp add: up_def cont_Iup)
done
lemma up_eq [simp]: "(up·x = up·y) = (x = y)"
by (simp add: up_def cont_Iup)
lemma up_inject: "up·x = up·y ==> x = y"
by simp
lemma up_defined [simp]: "up·x ≠ ⊥"
by (simp add: up_def cont_Iup inst_up_pcpo)
lemma not_up_less_UU: "¬ up·x \<sqsubseteq> ⊥"
by simp
lemma up_less [simp]: "(up·x \<sqsubseteq> up·y) = (x \<sqsubseteq> y)"
by (simp add: up_def cont_Iup)
lemma upE [cases type: u]: "[|p = ⊥ ==> Q; !!x. p = up·x ==> Q|] ==> Q"
apply (cases p)
apply (simp add: inst_up_pcpo)
apply (simp add: up_def cont_Iup)
done
lemma up_induct [induct type: u]: "[|P ⊥; !!x. P (up·x)|] ==> P x"
by (cases x, simp_all)
text {* lifting preserves chain-finiteness *}
lemma up_chain_cases:
"chain Y ==>
(∃A. chain A ∧ (\<Squnion>i. Y i) = up·(\<Squnion>i. A i) ∧
(∃j. ∀i. Y (i + j) = up·(A i))) ∨ Y = (λi. ⊥)"
by (simp add: inst_up_pcpo up_def cont_Iup up_chain_lemma)
lemma compact_up: "compact x ==> compact (up·x)"
apply (rule compactI2)
apply (drule up_chain_cases, safe)
apply (drule (1) compactD2, simp)
apply (erule exE, rule_tac x="i + j" in exI)
apply simp
apply simp
done
lemma compact_upD: "compact (up·x) ==> compact x"
unfolding compact_def
by (drule adm_subst [OF cont_Rep_CFun2 [where f=up]], simp)
lemma compact_up_iff [simp]: "compact (up·x) = compact x"
by (safe elim!: compact_up compact_upD)
instance u :: (chfin) chfin
apply intro_classes
apply (erule compact_imp_max_in_chain)
apply (rule_tac p="\<Squnion>i. Y i" in upE, simp_all)
done
text {* properties of fup *}
lemma fup1 [simp]: "fup·f·⊥ = ⊥"
by (simp add: fup_def cont_Ifup1 cont_Ifup2 inst_up_pcpo cont2cont_LAM)
lemma fup2 [simp]: "fup·f·(up·x) = f·x"
by (simp add: up_def fup_def cont_Iup cont_Ifup1 cont_Ifup2 cont2cont_LAM)
lemma fup3 [simp]: "fup·up·x = x"
by (cases x, simp_all)
subsection {* Lifted cpo is a bifinite domain *}
instantiation u :: (profinite) bifinite
begin
definition
approx_up_def:
"approx = (λn. fup·(Λ x. up·(approx n·x)))"
instance proof
fix i :: nat and x :: "'a u"
show "chain (approx :: nat => 'a u -> 'a u)"
unfolding approx_up_def by simp
show "(\<Squnion>i. approx i·x) = x"
unfolding approx_up_def
by (simp add: lub_distribs eta_cfun)
show "approx i·(approx i·x) = approx i·x"
unfolding approx_up_def
by (induct x, simp, simp)
have "{x::'a u. approx i·x = x} ⊆
insert ⊥ ((λx. up·x) ` {x::'a. approx i·x = x})"
unfolding approx_up_def
by (rule subsetI, case_tac x, simp_all)
thus "finite {x::'a u. approx i·x = x}"
by (rule finite_subset, simp add: finite_fixes_approx)
qed
end
lemma approx_up [simp]: "approx i·(up·x) = up·(approx i·x)"
unfolding approx_up_def by simp
end