src/HOL/Enum.thy
 author bulwahn Mon, 30 Jan 2012 13:55:22 +0100 changeset 46359 9bc43dc49d0a parent 46358 b2a936486685 child 46361 87d5d36a9005 permissions -rw-r--r--
adding code equation for rtranclp in Enum
```
(* Author: Florian Haftmann, TU Muenchen *)

header {* Finite types as explicit enumerations *}

theory Enum
imports Map String
begin

subsection {* Class @{text enum} *}

class enum =
fixes enum :: "'a list"
fixes enum_all :: "('a \<Rightarrow> bool) \<Rightarrow> bool"
fixes enum_ex  :: "('a \<Rightarrow> bool) \<Rightarrow> bool"
assumes UNIV_enum: "UNIV = set enum"
and enum_distinct: "distinct enum"
assumes enum_all : "enum_all P = (\<forall> x. P x)"
assumes enum_ex  : "enum_ex P = (\<exists> x. P x)"
begin

subclass finite proof

lemma enum_UNIV: "set enum = UNIV" unfolding UNIV_enum ..

lemma in_enum: "x \<in> set enum"
unfolding enum_UNIV by auto

lemma enum_eq_I:
assumes "\<And>x. x \<in> set xs"
shows "set enum = set xs"
proof -
from assms UNIV_eq_I have "UNIV = set xs" by auto
with enum_UNIV show ?thesis by simp
qed

end

subsection {* Equality and order on functions *}

instantiation "fun" :: (enum, equal) equal
begin

definition
"HOL.equal f g \<longleftrightarrow> (\<forall>x \<in> set enum. f x = g x)"

instance proof
qed (simp_all add: equal_fun_def enum_UNIV fun_eq_iff)

end

lemma [code]:
"HOL.equal f g \<longleftrightarrow> enum_all (%x. f x = g x)"
by (auto simp add: equal enum_all fun_eq_iff)

lemma [code nbe]:
"HOL.equal (f :: _ \<Rightarrow> _) f \<longleftrightarrow> True"
by (fact equal_refl)

lemma order_fun [code]:
fixes f g :: "'a\<Colon>enum \<Rightarrow> 'b\<Colon>order"
shows "f \<le> g \<longleftrightarrow> enum_all (\<lambda>x. f x \<le> g x)"
and "f < g \<longleftrightarrow> f \<le> g \<and> enum_ex (\<lambda>x. f x \<noteq> g x)"
by (simp_all add: enum_all enum_ex fun_eq_iff le_fun_def order_less_le)

subsection {* Quantifiers *}

lemma all_code [code]: "(\<forall>x. P x) \<longleftrightarrow> enum_all P"

lemma exists_code [code]: "(\<exists>x. P x) \<longleftrightarrow> enum_ex P"

lemma exists1_code[code]: "(\<exists>!x. P x) \<longleftrightarrow> list_ex1 P enum"
unfolding list_ex1_iff enum_UNIV by auto

subsection {* Default instances *}

primrec n_lists :: "nat \<Rightarrow> 'a list \<Rightarrow> 'a list list" where
"n_lists 0 xs = [[]]"
| "n_lists (Suc n) xs = concat (map (\<lambda>ys. map (\<lambda>y. y # ys) xs) (n_lists n xs))"

lemma n_lists_Nil [simp]: "n_lists n [] = (if n = 0 then [[]] else [])"
by (induct n) simp_all

lemma length_n_lists: "length (n_lists n xs) = length xs ^ n"
by (induct n) (auto simp add: length_concat o_def listsum_triv)

lemma length_n_lists_elem: "ys \<in> set (n_lists n xs) \<Longrightarrow> length ys = n"
by (induct n arbitrary: ys) auto

lemma set_n_lists: "set (n_lists n xs) = {ys. length ys = n \<and> set ys \<subseteq> set xs}"
proof (rule set_eqI)
fix ys :: "'a list"
show "ys \<in> set (n_lists n xs) \<longleftrightarrow> ys \<in> {ys. length ys = n \<and> set ys \<subseteq> set xs}"
proof -
have "ys \<in> set (n_lists n xs) \<Longrightarrow> length ys = n"
by (induct n arbitrary: ys) auto
moreover have "\<And>x. ys \<in> set (n_lists n xs) \<Longrightarrow> x \<in> set ys \<Longrightarrow> x \<in> set xs"
by (induct n arbitrary: ys) auto
moreover have "set ys \<subseteq> set xs \<Longrightarrow> ys \<in> set (n_lists (length ys) xs)"
by (induct ys) auto
ultimately show ?thesis by auto
qed
qed

lemma distinct_n_lists:
assumes "distinct xs"
shows "distinct (n_lists n xs)"
proof (rule card_distinct)
from assms have card_length: "card (set xs) = length xs" by (rule distinct_card)
have "card (set (n_lists n xs)) = card (set xs) ^ n"
proof (induct n)
case 0 then show ?case by simp
next
case (Suc n)
moreover have "card (\<Union>ys\<in>set (n_lists n xs). (\<lambda>y. y # ys) ` set xs)
= (\<Sum>ys\<in>set (n_lists n xs). card ((\<lambda>y. y # ys) ` set xs))"
by (rule card_UN_disjoint) auto
moreover have "\<And>ys. card ((\<lambda>y. y # ys) ` set xs) = card (set xs)"
by (rule card_image) (simp add: inj_on_def)
ultimately show ?case by auto
qed
also have "\<dots> = length xs ^ n" by (simp add: card_length)
finally show "card (set (n_lists n xs)) = length (n_lists n xs)"
qed

lemma map_of_zip_enum_is_Some:
assumes "length ys = length (enum \<Colon> 'a\<Colon>enum list)"
shows "\<exists>y. map_of (zip (enum \<Colon> 'a\<Colon>enum list) ys) x = Some y"
proof -
from assms have "x \<in> set (enum \<Colon> 'a\<Colon>enum list) \<longleftrightarrow>
(\<exists>y. map_of (zip (enum \<Colon> 'a\<Colon>enum list) ys) x = Some y)"
by (auto intro!: map_of_zip_is_Some)
then show ?thesis using enum_UNIV by auto
qed

lemma map_of_zip_enum_inject:
fixes xs ys :: "'b\<Colon>enum list"
assumes length: "length xs = length (enum \<Colon> 'a\<Colon>enum list)"
"length ys = length (enum \<Colon> 'a\<Colon>enum list)"
and map_of: "the \<circ> map_of (zip (enum \<Colon> 'a\<Colon>enum list) xs) = the \<circ> map_of (zip (enum \<Colon> 'a\<Colon>enum list) ys)"
shows "xs = ys"
proof -
have "map_of (zip (enum \<Colon> 'a list) xs) = map_of (zip (enum \<Colon> 'a list) ys)"
proof
fix x :: 'a
from length map_of_zip_enum_is_Some obtain y1 y2
where "map_of (zip (enum \<Colon> 'a list) xs) x = Some y1"
and "map_of (zip (enum \<Colon> 'a list) ys) x = Some y2" by blast
moreover from map_of have "the (map_of (zip (enum \<Colon> 'a\<Colon>enum list) xs) x) = the (map_of (zip (enum \<Colon> 'a\<Colon>enum list) ys) x)"
by (auto dest: fun_cong)
ultimately show "map_of (zip (enum \<Colon> 'a\<Colon>enum list) xs) x = map_of (zip (enum \<Colon> 'a\<Colon>enum list) ys) x"
by simp
qed
with length enum_distinct show "xs = ys" by (rule map_of_zip_inject)
qed

definition
all_n_lists :: "(('a :: enum) list \<Rightarrow> bool) \<Rightarrow> nat \<Rightarrow> bool"
where
"all_n_lists P n = (\<forall>xs \<in> set (n_lists n enum). P xs)"

lemma [code]:
"all_n_lists P n = (if n = 0 then P [] else enum_all (%x. all_n_lists (%xs. P (x # xs)) (n - 1)))"
unfolding all_n_lists_def enum_all
by (cases n) (auto simp add: enum_UNIV)

definition
ex_n_lists :: "(('a :: enum) list \<Rightarrow> bool) \<Rightarrow> nat \<Rightarrow> bool"
where
"ex_n_lists P n = (\<exists>xs \<in> set (n_lists n enum). P xs)"

lemma [code]:
"ex_n_lists P n = (if n = 0 then P [] else enum_ex (%x. ex_n_lists (%xs. P (x # xs)) (n - 1)))"
unfolding ex_n_lists_def enum_ex
by (cases n) (auto simp add: enum_UNIV)

instantiation "fun" :: (enum, enum) enum
begin

definition
"enum = map (\<lambda>ys. the o map_of (zip (enum\<Colon>'a list) ys)) (n_lists (length (enum\<Colon>'a\<Colon>enum list)) enum)"

definition
"enum_all P = all_n_lists (\<lambda>bs. P (the o map_of (zip enum bs))) (length (enum :: 'a list))"

definition
"enum_ex P = ex_n_lists (\<lambda>bs. P (the o map_of (zip enum bs))) (length (enum :: 'a list))"

instance proof
show "UNIV = set (enum \<Colon> ('a \<Rightarrow> 'b) list)"
proof (rule UNIV_eq_I)
fix f :: "'a \<Rightarrow> 'b"
have "f = the \<circ> map_of (zip (enum \<Colon> 'a\<Colon>enum list) (map f enum))"
by (auto simp add: map_of_zip_map fun_eq_iff intro: in_enum)
then show "f \<in> set enum"
by (auto simp add: enum_fun_def set_n_lists intro: in_enum)
qed
next
from map_of_zip_enum_inject
show "distinct (enum \<Colon> ('a \<Rightarrow> 'b) list)"
by (auto intro!: inj_onI simp add: enum_fun_def
distinct_map distinct_n_lists enum_distinct set_n_lists enum_all)
next
fix P
show "enum_all (P :: ('a \<Rightarrow> 'b) \<Rightarrow> bool) = (\<forall>x. P x)"
proof
assume "enum_all P"
show "\<forall>x. P x"
proof
fix f :: "'a \<Rightarrow> 'b"
have f: "f = the \<circ> map_of (zip (enum \<Colon> 'a\<Colon>enum list) (map f enum))"
by (auto simp add: map_of_zip_map fun_eq_iff intro: in_enum)
from `enum_all P` have "P (the \<circ> map_of (zip enum (map f enum)))"
unfolding enum_all_fun_def all_n_lists_def
apply (erule_tac x="map f enum" in allE)
apply (auto intro!: in_enum)
done
from this f show "P f" by auto
qed
next
assume "\<forall>x. P x"
from this show "enum_all P"
unfolding enum_all_fun_def all_n_lists_def by auto
qed
next
fix P
show "enum_ex (P :: ('a \<Rightarrow> 'b) \<Rightarrow> bool) = (\<exists>x. P x)"
proof
assume "enum_ex P"
from this show "\<exists>x. P x"
unfolding enum_ex_fun_def ex_n_lists_def by auto
next
assume "\<exists>x. P x"
from this obtain f where "P f" ..
have f: "f = the \<circ> map_of (zip (enum \<Colon> 'a\<Colon>enum list) (map f enum))"
by (auto simp add: map_of_zip_map fun_eq_iff intro: in_enum)
from `P f` this have "P (the \<circ> map_of (zip (enum \<Colon> 'a\<Colon>enum list) (map f enum)))"
by auto
from  this show "enum_ex P"
unfolding enum_ex_fun_def ex_n_lists_def
apply (rule_tac x="map f enum" in exI)
apply (auto intro!: in_enum)
done
qed
qed

end

lemma enum_fun_code [code]: "enum = (let enum_a = (enum \<Colon> 'a\<Colon>{enum, equal} list)
in map (\<lambda>ys. the o map_of (zip enum_a ys)) (n_lists (length enum_a) enum))"

lemma enum_all_fun_code [code]:
"enum_all P = (let enum_a = (enum :: 'a::{enum, equal} list)
in all_n_lists (\<lambda>bs. P (the o map_of (zip enum_a bs))) (length enum_a))"

lemma enum_ex_fun_code [code]:
"enum_ex P = (let enum_a = (enum :: 'a::{enum, equal} list)
in ex_n_lists (\<lambda>bs. P (the o map_of (zip enum_a bs))) (length enum_a))"

instantiation unit :: enum
begin

definition
"enum = [()]"

definition
"enum_all P = P ()"

definition
"enum_ex P = P ()"

instance proof
qed (auto simp add: enum_unit_def UNIV_unit enum_all_unit_def enum_ex_unit_def intro: unit.exhaust)

end

instantiation bool :: enum
begin

definition
"enum = [False, True]"

definition
"enum_all P = (P False \<and> P True)"

definition
"enum_ex P = (P False \<or> P True)"

instance proof
fix P
show "enum_all (P :: bool \<Rightarrow> bool) = (\<forall>x. P x)"
unfolding enum_all_bool_def by (auto, case_tac x) auto
next
fix P
show "enum_ex (P :: bool \<Rightarrow> bool) = (\<exists>x. P x)"
unfolding enum_ex_bool_def by (auto, case_tac x) auto
qed (auto simp add: enum_bool_def UNIV_bool)

end

primrec product :: "'a list \<Rightarrow> 'b list \<Rightarrow> ('a \<times> 'b) list" where
"product [] _ = []"
| "product (x#xs) ys = map (Pair x) ys @ product xs ys"

lemma product_list_set:
"set (product xs ys) = set xs \<times> set ys"
by (induct xs) auto

lemma distinct_product:
assumes "distinct xs" and "distinct ys"
shows "distinct (product xs ys)"
using assms by (induct xs)
(auto intro: inj_onI simp add: product_list_set distinct_map)

instantiation prod :: (enum, enum) enum
begin

definition
"enum = product enum enum"

definition
"enum_all P = enum_all (%x. enum_all (%y. P (x, y)))"

definition
"enum_ex P = enum_ex (%x. enum_ex (%y. P (x, y)))"

instance by default
enum_UNIV enum_distinct enum_all_prod_def enum_all enum_ex_prod_def enum_ex)

end

instantiation sum :: (enum, enum) enum
begin

definition
"enum = map Inl enum @ map Inr enum"

definition
"enum_all P = (enum_all (%x. P (Inl x)) \<and> enum_all (%x. P (Inr x)))"

definition
"enum_ex P = (enum_ex (%x. P (Inl x)) \<or> enum_ex (%x. P (Inr x)))"

instance proof
fix P
show "enum_all (P :: ('a + 'b) \<Rightarrow> bool) = (\<forall>x. P x)"
unfolding enum_all_sum_def enum_all
by (auto, case_tac x) auto
next
fix P
show "enum_ex (P :: ('a + 'b) \<Rightarrow> bool) = (\<exists>x. P x)"
unfolding enum_ex_sum_def enum_ex
by (auto, case_tac x) auto
qed (auto simp add: enum_UNIV enum_sum_def, case_tac x, auto intro: inj_onI simp add: distinct_map enum_distinct)

end

instantiation nibble :: enum
begin

definition
"enum = [Nibble0, Nibble1, Nibble2, Nibble3, Nibble4, Nibble5, Nibble6, Nibble7,
Nibble8, Nibble9, NibbleA, NibbleB, NibbleC, NibbleD, NibbleE, NibbleF]"

definition
"enum_all P = (P Nibble0 \<and> P Nibble1 \<and> P Nibble2 \<and> P Nibble3 \<and> P Nibble4 \<and> P Nibble5 \<and> P Nibble6 \<and> P Nibble7
\<and> P Nibble8 \<and> P Nibble9 \<and> P NibbleA \<and> P NibbleB \<and> P NibbleC \<and> P NibbleD \<and> P NibbleE \<and> P NibbleF)"

definition
"enum_ex P = (P Nibble0 \<or> P Nibble1 \<or> P Nibble2 \<or> P Nibble3 \<or> P Nibble4 \<or> P Nibble5 \<or> P Nibble6 \<or> P Nibble7
\<or> P Nibble8 \<or> P Nibble9 \<or> P NibbleA \<or> P NibbleB \<or> P NibbleC \<or> P NibbleD \<or> P NibbleE \<or> P NibbleF)"

instance proof
fix P
show "enum_all (P :: nibble \<Rightarrow> bool) = (\<forall>x. P x)"
unfolding enum_all_nibble_def
by (auto, case_tac x) auto
next
fix P
show "enum_ex (P :: nibble \<Rightarrow> bool) = (\<exists>x. P x)"
unfolding enum_ex_nibble_def
by (auto, case_tac x) auto

end

instantiation char :: enum
begin

definition
"enum = map (split Char) (product enum enum)"

lemma enum_chars [code]:
"enum = chars"
unfolding enum_char_def chars_def enum_nibble_def by simp

definition
"enum_all P = list_all P chars"

definition
"enum_ex P = list_ex P chars"

lemma set_enum_char: "set (enum :: char list) = UNIV"
by (auto intro: char.exhaust simp add: enum_char_def product_list_set enum_UNIV full_SetCompr_eq [symmetric])

instance proof
fix P
show "enum_all (P :: char \<Rightarrow> bool) = (\<forall>x. P x)"
unfolding enum_all_char_def enum_chars[symmetric]
by (auto simp add: list_all_iff set_enum_char)
next
fix P
show "enum_ex (P :: char \<Rightarrow> bool) = (\<exists>x. P x)"
unfolding enum_ex_char_def enum_chars[symmetric]
by (auto simp add: list_ex_iff set_enum_char)
next
show "distinct (enum :: char list)"
by (auto intro: inj_onI simp add: enum_char_def product_list_set distinct_map distinct_product enum_distinct)

end

instantiation option :: (enum) enum
begin

definition
"enum = None # map Some enum"

definition
"enum_all P = (P None \<and> enum_all (%x. P (Some x)))"

definition
"enum_ex P = (P None \<or> enum_ex (%x. P (Some x)))"

instance proof
fix P
show "enum_all (P :: 'a option \<Rightarrow> bool) = (\<forall>x. P x)"
unfolding enum_all_option_def enum_all
by (auto, case_tac x) auto
next
fix P
show "enum_ex (P :: 'a option \<Rightarrow> bool) = (\<exists>x. P x)"
unfolding enum_ex_option_def enum_ex
by (auto, case_tac x) auto
qed (auto simp add: enum_UNIV enum_option_def, rule option.exhaust, auto intro: simp add: distinct_map enum_distinct)
end

primrec sublists :: "'a list \<Rightarrow> 'a list list" where
"sublists [] = [[]]"
| "sublists (x#xs) = (let xss = sublists xs in map (Cons x) xss @ xss)"

lemma length_sublists:
"length (sublists xs) = Suc (Suc (0\<Colon>nat)) ^ length xs"
by (induct xs) (simp_all add: Let_def)

lemma sublists_powset:
"set ` set (sublists xs) = Pow (set xs)"
proof -
have aux: "\<And>x A. set ` Cons x ` A = insert x ` set ` A"
have "set (map set (sublists xs)) = Pow (set xs)"
by (induct xs)
(simp_all add: aux Let_def Pow_insert Un_commute comp_def del: map_map)
then show ?thesis by simp
qed

lemma distinct_set_sublists:
assumes "distinct xs"
shows "distinct (map set (sublists xs))"
proof (rule card_distinct)
have "finite (set xs)" by rule
then have "card (Pow (set xs)) = Suc (Suc 0) ^ card (set xs)" by (rule card_Pow)
with assms distinct_card [of xs]
have "card (Pow (set xs)) = Suc (Suc 0) ^ length xs" by simp
then show "card (set (map set (sublists xs))) = length (map set (sublists xs))"
qed

instantiation set :: (enum) enum
begin

definition
"enum = map set (sublists enum)"

definition
"enum_all P \<longleftrightarrow> (\<forall>A\<in>set enum. P (A::'a set))"

definition
"enum_ex P \<longleftrightarrow> (\<exists>A\<in>set enum. P (A::'a set))"

instance proof
qed (simp_all add: enum_set_def enum_all_set_def enum_ex_set_def sublists_powset distinct_set_sublists
enum_distinct enum_UNIV)

end

subsection {* Small finite types *}

text {* We define small finite types for the use in Quickcheck *}

datatype finite_1 = a\<^isub>1

notation (output) a\<^isub>1  ("a\<^isub>1")

instantiation finite_1 :: enum
begin

definition
"enum = [a\<^isub>1]"

definition
"enum_all P = P a\<^isub>1"

definition
"enum_ex P = P a\<^isub>1"

instance proof
fix P
show "enum_all (P :: finite_1 \<Rightarrow> bool) = (\<forall>x. P x)"
unfolding enum_all_finite_1_def
by (auto, case_tac x) auto
next
fix P
show "enum_ex (P :: finite_1 \<Rightarrow> bool) = (\<exists>x. P x)"
unfolding enum_ex_finite_1_def
by (auto, case_tac x) auto
qed (auto simp add: enum_finite_1_def intro: finite_1.exhaust)

end

instantiation finite_1 :: linorder
begin

definition less_eq_finite_1 :: "finite_1 \<Rightarrow> finite_1 \<Rightarrow> bool"
where
"less_eq_finite_1 x y = True"

definition less_finite_1 :: "finite_1 \<Rightarrow> finite_1 \<Rightarrow> bool"
where
"less_finite_1 x y = False"

instance
apply (intro_classes)
apply (auto simp add: less_finite_1_def less_eq_finite_1_def)
apply (metis finite_1.exhaust)
done

end

hide_const (open) a\<^isub>1

datatype finite_2 = a\<^isub>1 | a\<^isub>2

notation (output) a\<^isub>1  ("a\<^isub>1")
notation (output) a\<^isub>2  ("a\<^isub>2")

instantiation finite_2 :: enum
begin

definition
"enum = [a\<^isub>1, a\<^isub>2]"

definition
"enum_all P = (P a\<^isub>1 \<and> P a\<^isub>2)"

definition
"enum_ex P = (P a\<^isub>1 \<or> P a\<^isub>2)"

instance proof
fix P
show "enum_all (P :: finite_2 \<Rightarrow> bool) = (\<forall>x. P x)"
unfolding enum_all_finite_2_def
by (auto, case_tac x) auto
next
fix P
show "enum_ex (P :: finite_2 \<Rightarrow> bool) = (\<exists>x. P x)"
unfolding enum_ex_finite_2_def
by (auto, case_tac x) auto
qed (auto simp add: enum_finite_2_def intro: finite_2.exhaust)

end

instantiation finite_2 :: linorder
begin

definition less_finite_2 :: "finite_2 \<Rightarrow> finite_2 \<Rightarrow> bool"
where
"less_finite_2 x y = ((x = a\<^isub>1) & (y = a\<^isub>2))"

definition less_eq_finite_2 :: "finite_2 \<Rightarrow> finite_2 \<Rightarrow> bool"
where
"less_eq_finite_2 x y = ((x = y) \<or> (x < y))"

instance
apply (intro_classes)
apply (auto simp add: less_finite_2_def less_eq_finite_2_def)
apply (metis finite_2.distinct finite_2.nchotomy)+
done

end

hide_const (open) a\<^isub>1 a\<^isub>2

datatype finite_3 = a\<^isub>1 | a\<^isub>2 | a\<^isub>3

notation (output) a\<^isub>1  ("a\<^isub>1")
notation (output) a\<^isub>2  ("a\<^isub>2")
notation (output) a\<^isub>3  ("a\<^isub>3")

instantiation finite_3 :: enum
begin

definition
"enum = [a\<^isub>1, a\<^isub>2, a\<^isub>3]"

definition
"enum_all P = (P a\<^isub>1 \<and> P a\<^isub>2 \<and> P a\<^isub>3)"

definition
"enum_ex P = (P a\<^isub>1 \<or> P a\<^isub>2 \<or> P a\<^isub>3)"

instance proof
fix P
show "enum_all (P :: finite_3 \<Rightarrow> bool) = (\<forall>x. P x)"
unfolding enum_all_finite_3_def
by (auto, case_tac x) auto
next
fix P
show "enum_ex (P :: finite_3 \<Rightarrow> bool) = (\<exists>x. P x)"
unfolding enum_ex_finite_3_def
by (auto, case_tac x) auto
qed (auto simp add: enum_finite_3_def intro: finite_3.exhaust)

end

instantiation finite_3 :: linorder
begin

definition less_finite_3 :: "finite_3 \<Rightarrow> finite_3 \<Rightarrow> bool"
where
"less_finite_3 x y = (case x of a\<^isub>1 => (y \<noteq> a\<^isub>1)
| a\<^isub>2 => (y = a\<^isub>3)| a\<^isub>3 => False)"

definition less_eq_finite_3 :: "finite_3 \<Rightarrow> finite_3 \<Rightarrow> bool"
where
"less_eq_finite_3 x y = ((x = y) \<or> (x < y))"

instance proof (intro_classes)
qed (auto simp add: less_finite_3_def less_eq_finite_3_def split: finite_3.split_asm)

end

hide_const (open) a\<^isub>1 a\<^isub>2 a\<^isub>3

datatype finite_4 = a\<^isub>1 | a\<^isub>2 | a\<^isub>3 | a\<^isub>4

notation (output) a\<^isub>1  ("a\<^isub>1")
notation (output) a\<^isub>2  ("a\<^isub>2")
notation (output) a\<^isub>3  ("a\<^isub>3")
notation (output) a\<^isub>4  ("a\<^isub>4")

instantiation finite_4 :: enum
begin

definition
"enum = [a\<^isub>1, a\<^isub>2, a\<^isub>3, a\<^isub>4]"

definition
"enum_all P = (P a\<^isub>1 \<and> P a\<^isub>2 \<and> P a\<^isub>3 \<and> P a\<^isub>4)"

definition
"enum_ex P = (P a\<^isub>1 \<or> P a\<^isub>2 \<or> P a\<^isub>3 \<or> P a\<^isub>4)"

instance proof
fix P
show "enum_all (P :: finite_4 \<Rightarrow> bool) = (\<forall>x. P x)"
unfolding enum_all_finite_4_def
by (auto, case_tac x) auto
next
fix P
show "enum_ex (P :: finite_4 \<Rightarrow> bool) = (\<exists>x. P x)"
unfolding enum_ex_finite_4_def
by (auto, case_tac x) auto
qed (auto simp add: enum_finite_4_def intro: finite_4.exhaust)

end

hide_const (open) a\<^isub>1 a\<^isub>2 a\<^isub>3 a\<^isub>4

datatype finite_5 = a\<^isub>1 | a\<^isub>2 | a\<^isub>3 | a\<^isub>4 | a\<^isub>5

notation (output) a\<^isub>1  ("a\<^isub>1")
notation (output) a\<^isub>2  ("a\<^isub>2")
notation (output) a\<^isub>3  ("a\<^isub>3")
notation (output) a\<^isub>4  ("a\<^isub>4")
notation (output) a\<^isub>5  ("a\<^isub>5")

instantiation finite_5 :: enum
begin

definition
"enum = [a\<^isub>1, a\<^isub>2, a\<^isub>3, a\<^isub>4, a\<^isub>5]"

definition
"enum_all P = (P a\<^isub>1 \<and> P a\<^isub>2 \<and> P a\<^isub>3 \<and> P a\<^isub>4 \<and> P a\<^isub>5)"

definition
"enum_ex P = (P a\<^isub>1 \<or> P a\<^isub>2 \<or> P a\<^isub>3 \<or> P a\<^isub>4 \<or> P a\<^isub>5)"

instance proof
fix P
show "enum_all (P :: finite_5 \<Rightarrow> bool) = (\<forall>x. P x)"
unfolding enum_all_finite_5_def
by (auto, case_tac x) auto
next
fix P
show "enum_ex (P :: finite_5 \<Rightarrow> bool) = (\<exists>x. P x)"
unfolding enum_ex_finite_5_def
by (auto, case_tac x) auto
qed (auto simp add: enum_finite_5_def intro: finite_5.exhaust)

end

hide_const (open) a\<^isub>1 a\<^isub>2 a\<^isub>3 a\<^isub>4 a\<^isub>5

subsection {* An executable THE operator on finite types *}

definition
[code del]: "enum_the P = The P"

lemma [code]:
"The P = (case filter P enum of [x] => x | _ => enum_the P)"
proof -
{
fix a
assume filter_enum: "filter P enum = [a]"
have "The P = a"
proof (rule the_equality)
fix x
assume "P x"
show "x = a"
proof (rule ccontr)
assume "x \<noteq> a"
from filter_enum obtain us vs
where enum_eq: "enum = us @ [a] @ vs"
and "\<forall> x \<in> set us. \<not> P x"
and "\<forall> x \<in> set vs. \<not> P x"
and "P a"
by (auto simp add: filter_eq_Cons_iff) (simp only: filter_empty_conv[symmetric])
with `P x` in_enum[of x, unfolded enum_eq] `x \<noteq> a` show "False" by auto
qed
next
from filter_enum show "P a" by (auto simp add: filter_eq_Cons_iff)
qed
}
from this show ?thesis
unfolding enum_the_def by (auto split: list.split)
qed

code_abort enum_the
code_const enum_the (Eval "(fn p => raise Match)")

subsection {* Further operations on finite types *}

lemma [code]:
"Collect P = set (filter P enum)"

lemma tranclp_unfold [code, no_atp]:
"tranclp r a b \<equiv> (a, b) \<in> trancl {(x, y). r x y}"

lemma rtranclp_rtrancl_eq[code, no_atp]:
"rtranclp r x y = ((x, y) : rtrancl {(x, y). r x y})"
unfolding rtrancl_def by auto

lemma max_ext_eq[code]:
"max_ext R = {(X, Y). finite X & finite Y & Y ~={} & (ALL x. x : X --> (EX xa : Y. (x, xa) : R))}"

subsection {* Executable accessible part *}
(* FIXME: should be moved somewhere else !? *)

subsubsection {* Finite monotone eventually stable sequences *}

lemma finite_mono_remains_stable_implies_strict_prefix:
fixes f :: "nat \<Rightarrow> 'a::order"
assumes S: "finite (range f)" "mono f" and eq: "\<forall>n. f n = f (Suc n) \<longrightarrow> f (Suc n) = f (Suc (Suc n))"
shows "\<exists>N. (\<forall>n\<le>N. \<forall>m\<le>N. m < n \<longrightarrow> f m < f n) \<and> (\<forall>n\<ge>N. f N = f n)"
using assms
proof -
have "\<exists>n. f n = f (Suc n)"
proof (rule ccontr)
assume "\<not> ?thesis"
then have "\<And>n. f n \<noteq> f (Suc n)" by auto
then have "\<And>n. f n < f (Suc n)"
using  `mono f` by (auto simp: le_less mono_iff_le_Suc)
with lift_Suc_mono_less_iff[of f]
have "\<And>n m. n < m \<Longrightarrow> f n < f m" by auto
then have "inj f"
by (auto simp: inj_on_def) (metis linorder_less_linear order_less_imp_not_eq)
with `finite (range f)` have "finite (UNIV::nat set)"
by (rule finite_imageD)
then show False by simp
qed
then guess n .. note n = this
def N \<equiv> "LEAST n. f n = f (Suc n)"
have N: "f N = f (Suc N)"
unfolding N_def using n by (rule LeastI)
show ?thesis
proof (intro exI[of _ N] conjI allI impI)
fix n assume "N \<le> n"
then have "\<And>m. N \<le> m \<Longrightarrow> m \<le> n \<Longrightarrow> f m = f N"
proof (induct rule: dec_induct)
case (step n) then show ?case
using eq[rule_format, of "n - 1"] N
by (cases n) (auto simp add: le_Suc_eq)
qed simp
from this[of n] `N \<le> n` show "f N = f n" by auto
next
fix n m :: nat assume "m < n" "n \<le> N"
then show "f m < f n"
proof (induct rule: less_Suc_induct[consumes 1])
case (1 i)
then have "i < N" by simp
then have "f i \<noteq> f (Suc i)"
unfolding N_def by (rule not_less_Least)
with `mono f` show ?case by (simp add: mono_iff_le_Suc less_le)
qed auto
qed
qed

lemma finite_mono_strict_prefix_implies_finite_fixpoint:
fixes f :: "nat \<Rightarrow> 'a set"
assumes S: "\<And>i. f i \<subseteq> S" "finite S"
and inj: "\<exists>N. (\<forall>n\<le>N. \<forall>m\<le>N. m < n \<longrightarrow> f m \<subset> f n) \<and> (\<forall>n\<ge>N. f N = f n)"
shows "f (card S) = (\<Union>n. f n)"
proof -
from inj obtain N where inj: "(\<forall>n\<le>N. \<forall>m\<le>N. m < n \<longrightarrow> f m \<subset> f n)" and eq: "(\<forall>n\<ge>N. f N = f n)" by auto

{ fix i have "i \<le> N \<Longrightarrow> i \<le> card (f i)"
proof (induct i)
case 0 then show ?case by simp
next
case (Suc i)
with inj[rule_format, of "Suc i" i]
have "(f i) \<subset> (f (Suc i))" by auto
moreover have "finite (f (Suc i))" using S by (rule finite_subset)
ultimately have "card (f i) < card (f (Suc i))" by (intro psubset_card_mono)
with Suc show ?case using inj by auto
qed
}
then have "N \<le> card (f N)" by simp
also have "\<dots> \<le> card S" using S by (intro card_mono)
finally have "f (card S) = f N" using eq by auto
then show ?thesis using eq inj[rule_format, of N]
apply auto
apply (case_tac "n < N")
apply (auto simp: not_less)
done
qed

subsubsection {* Bounded accessible part *}

fun bacc :: "('a * 'a) set => nat => 'a set"
where
"bacc r 0 = {x. \<forall> y. (y, x) \<notin> r}"
| "bacc r (Suc n) = (bacc r n Un {x. \<forall> y. (y, x) : r --> y : bacc r n})"

lemma bacc_subseteq_acc:
"bacc r n \<subseteq> acc r"
by (induct n) (auto intro: acc.intros)

lemma bacc_mono:
"n <= m ==> bacc r n \<subseteq> bacc r m"
by (induct rule: dec_induct) auto

lemma bacc_upper_bound:
"bacc (r :: ('a * 'a) set)  (card (UNIV :: ('a :: enum) set)) = (UN n. bacc r n)"
proof -
have "mono (bacc r)" unfolding mono_def by (simp add: bacc_mono)
moreover have "\<forall>n. bacc r n = bacc r (Suc n) \<longrightarrow> bacc r (Suc n) = bacc r (Suc (Suc n))" by auto
moreover have "finite (range (bacc r))" by auto
ultimately show ?thesis
by (intro finite_mono_strict_prefix_implies_finite_fixpoint)
(auto intro: finite_mono_remains_stable_implies_strict_prefix  simp add: enum_UNIV)
qed

lemma acc_subseteq_bacc:
assumes "finite r"
shows "acc r \<subseteq> (UN n. bacc r n)"
proof
fix x
assume "x : acc r"
from this have "\<exists> n. x : bacc r n"
proof (induct x arbitrary: n rule: acc.induct)
case (accI x)
from accI have "\<forall> y. \<exists> n. (y, x) \<in> r --> y : bacc r n" by simp
from choice[OF this] guess n .. note n = this
have "\<exists> n. \<forall>y. (y, x) : r --> y : bacc r n"
proof (safe intro!: exI[of _ "Max ((%(y,x). n y)`r)"])
fix y assume y: "(y, x) : r"
with n have "y : bacc r (n y)" by auto
moreover have "n y <= Max ((%(y, x). n y) ` r)"
using y `finite r` by (auto intro!: Max_ge)
note bacc_mono[OF this, of r]
ultimately show "y : bacc r (Max ((%(y, x). n y) ` r))" by auto
qed
from this guess n ..
from this show ?case
by (auto simp add: Let_def intro!: exI[of _ "Suc n"])
qed
thus "x : (UN n. bacc r n)" by auto
qed

lemma acc_bacc_eq: "acc ((set xs) :: (('a :: enum) * 'a) set) = bacc (set xs) (card (UNIV :: 'a set))"
by (metis acc_subseteq_bacc bacc_subseteq_acc bacc_upper_bound finite_set order_eq_iff)

definition
[code del]: "card_UNIV = card UNIV"

lemma [code]:
"card_UNIV TYPE('a :: enum) = card (set (Enum.enum :: 'a list))"
unfolding card_UNIV_def enum_UNIV ..

declare acc_bacc_eq[folded card_UNIV_def, code]

lemma [code_unfold]: "accp r = (%x. x : acc {(x, y). r x y})"
unfolding acc_def by simp

subsection {* Closing up *}

hide_type (open) finite_1 finite_2 finite_3 finite_4 finite_5
hide_const (open) enum enum_all enum_ex n_lists all_n_lists ex_n_lists product ntrancl

end
```