(* Title: HOLCF/Product_Cpo.thy
Author: Franz Regensburger
*)
header {* The cpo of cartesian products *}
theory Product_Cpo
imports Adm
begin
default_sort cpo
subsection {* Unit type is a pcpo *}
instantiation unit :: below
begin
definition
below_unit_def [simp]: "x \<sqsubseteq> (y::unit) \<longleftrightarrow> True"
instance ..
end
instance unit :: discrete_cpo
by intro_classes simp
instance unit :: finite_po ..
instance unit :: pcpo
by intro_classes simp
subsection {* Product type is a partial order *}
instantiation prod :: (below, below) below
begin
definition
below_prod_def: "(op \<sqsubseteq>) \<equiv> \<lambda>p1 p2. (fst p1 \<sqsubseteq> fst p2 \<and> snd p1 \<sqsubseteq> snd p2)"
instance ..
end
instance prod :: (po, po) po
proof
fix x :: "'a \<times> 'b"
show "x \<sqsubseteq> x"
unfolding below_prod_def by simp
next
fix x y :: "'a \<times> 'b"
assume "x \<sqsubseteq> y" "y \<sqsubseteq> x" thus "x = y"
unfolding below_prod_def Pair_fst_snd_eq
by (fast intro: below_antisym)
next
fix x y z :: "'a \<times> 'b"
assume "x \<sqsubseteq> y" "y \<sqsubseteq> z" thus "x \<sqsubseteq> z"
unfolding below_prod_def
by (fast intro: below_trans)
qed
subsection {* Monotonicity of \emph{Pair}, \emph{fst}, \emph{snd} *}
lemma prod_belowI: "\<lbrakk>fst p \<sqsubseteq> fst q; snd p \<sqsubseteq> snd q\<rbrakk> \<Longrightarrow> p \<sqsubseteq> q"
unfolding below_prod_def by simp
lemma Pair_below_iff [simp]: "(a, b) \<sqsubseteq> (c, d) \<longleftrightarrow> a \<sqsubseteq> c \<and> b \<sqsubseteq> d"
unfolding below_prod_def by simp
text {* Pair @{text "(_,_)"} is monotone in both arguments *}
lemma monofun_pair1: "monofun (\<lambda>x. (x, y))"
by (simp add: monofun_def)
lemma monofun_pair2: "monofun (\<lambda>y. (x, y))"
by (simp add: monofun_def)
lemma monofun_pair:
"\<lbrakk>x1 \<sqsubseteq> x2; y1 \<sqsubseteq> y2\<rbrakk> \<Longrightarrow> (x1, y1) \<sqsubseteq> (x2, y2)"
by simp
lemma ch2ch_Pair [simp]:
"chain X \<Longrightarrow> chain Y \<Longrightarrow> chain (\<lambda>i. (X i, Y i))"
by (rule chainI, simp add: chainE)
text {* @{term fst} and @{term snd} are monotone *}
lemma fst_monofun: "x \<sqsubseteq> y \<Longrightarrow> fst x \<sqsubseteq> fst y"
unfolding below_prod_def by simp
lemma snd_monofun: "x \<sqsubseteq> y \<Longrightarrow> snd x \<sqsubseteq> snd y"
unfolding below_prod_def by simp
lemma monofun_fst: "monofun fst"
by (simp add: monofun_def below_prod_def)
lemma monofun_snd: "monofun snd"
by (simp add: monofun_def below_prod_def)
lemmas ch2ch_fst [simp] = ch2ch_monofun [OF monofun_fst]
lemmas ch2ch_snd [simp] = ch2ch_monofun [OF monofun_snd]
lemma prod_chain_cases:
assumes "chain Y"
obtains A B
where "chain A" and "chain B" and "Y = (\<lambda>i. (A i, B i))"
proof
from `chain Y` show "chain (\<lambda>i. fst (Y i))" by (rule ch2ch_fst)
from `chain Y` show "chain (\<lambda>i. snd (Y i))" by (rule ch2ch_snd)
show "Y = (\<lambda>i. (fst (Y i), snd (Y i)))" by simp
qed
subsection {* Product type is a cpo *}
lemma is_lub_Pair:
"\<lbrakk>range A <<| x; range B <<| y\<rbrakk> \<Longrightarrow> range (\<lambda>i. (A i, B i)) <<| (x, y)"
apply (rule is_lubI [OF ub_rangeI])
apply (simp add: is_ub_lub)
apply (frule ub2ub_monofun [OF monofun_fst])
apply (drule ub2ub_monofun [OF monofun_snd])
apply (simp add: below_prod_def is_lub_lub)
done
lemma thelub_Pair:
"\<lbrakk>chain (A::nat \<Rightarrow> 'a::cpo); chain (B::nat \<Rightarrow> 'b::cpo)\<rbrakk>
\<Longrightarrow> (\<Squnion>i. (A i, B i)) = (\<Squnion>i. A i, \<Squnion>i. B i)"
by (fast intro: thelubI is_lub_Pair elim: thelubE)
lemma lub_cprod:
fixes S :: "nat \<Rightarrow> ('a::cpo \<times> 'b::cpo)"
assumes S: "chain S"
shows "range S <<| (\<Squnion>i. fst (S i), \<Squnion>i. snd (S i))"
proof -
from `chain S` have "chain (\<lambda>i. fst (S i))"
by (rule ch2ch_fst)
hence 1: "range (\<lambda>i. fst (S i)) <<| (\<Squnion>i. fst (S i))"
by (rule cpo_lubI)
from `chain S` have "chain (\<lambda>i. snd (S i))"
by (rule ch2ch_snd)
hence 2: "range (\<lambda>i. snd (S i)) <<| (\<Squnion>i. snd (S i))"
by (rule cpo_lubI)
show "range S <<| (\<Squnion>i. fst (S i), \<Squnion>i. snd (S i))"
using is_lub_Pair [OF 1 2] by simp
qed
lemma thelub_cprod:
"chain (S::nat \<Rightarrow> 'a::cpo \<times> 'b::cpo)
\<Longrightarrow> (\<Squnion>i. S i) = (\<Squnion>i. fst (S i), \<Squnion>i. snd (S i))"
by (rule lub_cprod [THEN thelubI])
instance prod :: (cpo, cpo) cpo
proof
fix S :: "nat \<Rightarrow> ('a \<times> 'b)"
assume "chain S"
hence "range S <<| (\<Squnion>i. fst (S i), \<Squnion>i. snd (S i))"
by (rule lub_cprod)
thus "\<exists>x. range S <<| x" ..
qed
instance prod :: (finite_po, finite_po) finite_po ..
instance prod :: (discrete_cpo, discrete_cpo) discrete_cpo
proof
fix x y :: "'a \<times> 'b"
show "x \<sqsubseteq> y \<longleftrightarrow> x = y"
unfolding below_prod_def Pair_fst_snd_eq
by simp
qed
subsection {* Product type is pointed *}
lemma minimal_cprod: "(\<bottom>, \<bottom>) \<sqsubseteq> p"
by (simp add: below_prod_def)
instance prod :: (pcpo, pcpo) pcpo
by intro_classes (fast intro: minimal_cprod)
lemma inst_cprod_pcpo: "\<bottom> = (\<bottom>, \<bottom>)"
by (rule minimal_cprod [THEN UU_I, symmetric])
lemma Pair_defined_iff [simp]: "(x, y) = \<bottom> \<longleftrightarrow> x = \<bottom> \<and> y = \<bottom>"
unfolding inst_cprod_pcpo by simp
lemma fst_strict [simp]: "fst \<bottom> = \<bottom>"
unfolding inst_cprod_pcpo by (rule fst_conv)
lemma snd_strict [simp]: "snd \<bottom> = \<bottom>"
unfolding inst_cprod_pcpo by (rule snd_conv)
lemma Pair_strict [simp]: "(\<bottom>, \<bottom>) = \<bottom>"
by simp
lemma split_strict [simp]: "split f \<bottom> = f \<bottom> \<bottom>"
unfolding split_def by simp
subsection {* Continuity of \emph{Pair}, \emph{fst}, \emph{snd} *}
lemma cont_pair1: "cont (\<lambda>x. (x, y))"
apply (rule contI)
apply (rule is_lub_Pair)
apply (erule cpo_lubI)
apply (rule lub_const)
done
lemma cont_pair2: "cont (\<lambda>y. (x, y))"
apply (rule contI)
apply (rule is_lub_Pair)
apply (rule lub_const)
apply (erule cpo_lubI)
done
lemma cont_fst: "cont fst"
apply (rule contI)
apply (simp add: thelub_cprod)
apply (erule cpo_lubI [OF ch2ch_fst])
done
lemma cont_snd: "cont snd"
apply (rule contI)
apply (simp add: thelub_cprod)
apply (erule cpo_lubI [OF ch2ch_snd])
done
lemma cont2cont_Pair [simp, cont2cont]:
assumes f: "cont (\<lambda>x. f x)"
assumes g: "cont (\<lambda>x. g x)"
shows "cont (\<lambda>x. (f x, g x))"
apply (rule cont_apply [OF f cont_pair1])
apply (rule cont_apply [OF g cont_pair2])
apply (rule cont_const)
done
lemmas cont2cont_fst [simp, cont2cont] = cont_compose [OF cont_fst]
lemmas cont2cont_snd [simp, cont2cont] = cont_compose [OF cont_snd]
lemma cont2cont_split:
assumes f1: "\<And>a b. cont (\<lambda>x. f x a b)"
assumes f2: "\<And>x b. cont (\<lambda>a. f x a b)"
assumes f3: "\<And>x a. cont (\<lambda>b. f x a b)"
assumes g: "cont (\<lambda>x. g x)"
shows "cont (\<lambda>x. split (\<lambda>a b. f x a b) (g x))"
unfolding split_def
apply (rule cont_apply [OF g])
apply (rule cont_apply [OF cont_fst f2])
apply (rule cont_apply [OF cont_snd f3])
apply (rule cont_const)
apply (rule f1)
done
lemma cont_fst_snd_D1:
"cont (\<lambda>p. f (fst p) (snd p)) \<Longrightarrow> cont (\<lambda>x. f x y)"
by (drule cont_compose [OF _ cont_pair1], simp)
lemma cont_fst_snd_D2:
"cont (\<lambda>p. f (fst p) (snd p)) \<Longrightarrow> cont (\<lambda>y. f x y)"
by (drule cont_compose [OF _ cont_pair2], simp)
lemma cont2cont_split' [simp, cont2cont]:
assumes f: "cont (\<lambda>p. f (fst p) (fst (snd p)) (snd (snd p)))"
assumes g: "cont (\<lambda>x. g x)"
shows "cont (\<lambda>x. split (f x) (g x))"
proof -
note f1 = f [THEN cont_fst_snd_D1]
note f2 = f [THEN cont_fst_snd_D2, THEN cont_fst_snd_D1]
note f3 = f [THEN cont_fst_snd_D2, THEN cont_fst_snd_D2]
show ?thesis
unfolding split_def
apply (rule cont_apply [OF g])
apply (rule cont_apply [OF cont_fst f2])
apply (rule cont_apply [OF cont_snd f3])
apply (rule cont_const)
apply (rule f1)
done
qed
subsection {* Compactness and chain-finiteness *}
lemma fst_below_iff: "fst (x::'a \<times> 'b) \<sqsubseteq> y \<longleftrightarrow> x \<sqsubseteq> (y, snd x)"
unfolding below_prod_def by simp
lemma snd_below_iff: "snd (x::'a \<times> 'b) \<sqsubseteq> y \<longleftrightarrow> x \<sqsubseteq> (fst x, y)"
unfolding below_prod_def by simp
lemma compact_fst: "compact x \<Longrightarrow> compact (fst x)"
by (rule compactI, simp add: fst_below_iff)
lemma compact_snd: "compact x \<Longrightarrow> compact (snd x)"
by (rule compactI, simp add: snd_below_iff)
lemma compact_Pair: "\<lbrakk>compact x; compact y\<rbrakk> \<Longrightarrow> compact (x, y)"
by (rule compactI, simp add: below_prod_def)
lemma compact_Pair_iff [simp]: "compact (x, y) \<longleftrightarrow> compact x \<and> compact y"
apply (safe intro!: compact_Pair)
apply (drule compact_fst, simp)
apply (drule compact_snd, simp)
done
instance prod :: (chfin, chfin) chfin
apply intro_classes
apply (erule compact_imp_max_in_chain)
apply (case_tac "\<Squnion>i. Y i", simp)
done
end