src/HOL/Library/Multiset.thy
 author haftmann Mon, 26 Dec 2011 22:17:10 +0100 changeset 45989 b39256df5f8a parent 45866 e62b319c7696 child 46168 bef8c811df20 permissions -rw-r--r--
moved theorem requiring multisets from More_List to Multiset
```
(*  Title:      HOL/Library/Multiset.thy
Author:     Tobias Nipkow, Markus Wenzel, Lawrence C Paulson, Norbert Voelker
*)

theory Multiset
imports Main
begin

subsection {* The type of multisets *}

definition "multiset = {f :: 'a => nat. finite {x. f x > 0}}"

typedef (open) 'a multiset = "multiset :: ('a => nat) set"
morphisms count Abs_multiset
unfolding multiset_def
proof
show "(\<lambda>x. 0::nat) \<in> {f. finite {x. f x > 0}}" by simp
qed

lemmas multiset_typedef = Abs_multiset_inverse count_inverse count

abbreviation Melem :: "'a => 'a multiset => bool"  ("(_/ :# _)" [50, 51] 50) where
"a :# M == 0 < count M a"

notation (xsymbols)
Melem (infix "\<in>#" 50)

lemma multiset_eq_iff:
"M = N \<longleftrightarrow> (\<forall>a. count M a = count N a)"
by (simp only: count_inject [symmetric] fun_eq_iff)

lemma multiset_eqI:
"(\<And>x. count A x = count B x) \<Longrightarrow> A = B"
using multiset_eq_iff by auto

text {*
\medskip Preservation of the representing set @{term multiset}.
*}

lemma const0_in_multiset:
"(\<lambda>a. 0) \<in> multiset"

lemma only1_in_multiset:
"(\<lambda>b. if b = a then n else 0) \<in> multiset"

lemma union_preserves_multiset:
"M \<in> multiset \<Longrightarrow> N \<in> multiset \<Longrightarrow> (\<lambda>a. M a + N a) \<in> multiset"

lemma diff_preserves_multiset:
assumes "M \<in> multiset"
shows "(\<lambda>a. M a - N a) \<in> multiset"
proof -
have "{x. N x < M x} \<subseteq> {x. 0 < M x}"
by auto
with assms show ?thesis
by (auto simp add: multiset_def intro: finite_subset)
qed

lemma filter_preserves_multiset:
assumes "M \<in> multiset"
shows "(\<lambda>x. if P x then M x else 0) \<in> multiset"
proof -
have "{x. (P x \<longrightarrow> 0 < M x) \<and> P x} \<subseteq> {x. 0 < M x}"
by auto
with assms show ?thesis
by (auto simp add: multiset_def intro: finite_subset)
qed

lemmas in_multiset = const0_in_multiset only1_in_multiset
union_preserves_multiset diff_preserves_multiset filter_preserves_multiset

subsection {* Representing multisets *}

text {* Multiset enumeration *}

instantiation multiset :: (type) "{zero, plus}"
begin

definition Mempty_def:
"0 = Abs_multiset (\<lambda>a. 0)"

abbreviation Mempty :: "'a multiset" ("{#}") where
"Mempty \<equiv> 0"

definition union_def:
"M + N = Abs_multiset (\<lambda>a. count M a + count N a)"

instance ..

end

definition single :: "'a => 'a multiset" where
"single a = Abs_multiset (\<lambda>b. if b = a then 1 else 0)"

syntax
"_multiset" :: "args => 'a multiset"    ("{#(_)#}")
translations
"{#x, xs#}" == "{#x#} + {#xs#}"
"{#x#}" == "CONST single x"

lemma count_empty [simp]: "count {#} a = 0"
by (simp add: Mempty_def in_multiset multiset_typedef)

lemma count_single [simp]: "count {#b#} a = (if b = a then 1 else 0)"
by (simp add: single_def in_multiset multiset_typedef)

subsection {* Basic operations *}

subsubsection {* Union *}

lemma count_union [simp]: "count (M + N) a = count M a + count N a"
by (simp add: union_def in_multiset multiset_typedef)

instance multiset :: (type) cancel_comm_monoid_add proof

subsubsection {* Difference *}

instantiation multiset :: (type) minus
begin

definition diff_def:
"M - N = Abs_multiset (\<lambda>a. count M a - count N a)"

instance ..

end

lemma count_diff [simp]: "count (M - N) a = count M a - count N a"
by (simp add: diff_def in_multiset multiset_typedef)

lemma diff_empty [simp]: "M - {#} = M \<and> {#} - M = {#}"

lemma diff_cancel[simp]: "A - A = {#}"
by (rule multiset_eqI) simp

lemma diff_union_cancelR [simp]: "M + N - N = (M::'a multiset)"

lemma diff_union_cancelL [simp]: "N + M - N = (M::'a multiset)"

lemma insert_DiffM:
"x \<in># M \<Longrightarrow> {#x#} + (M - {#x#}) = M"
by (clarsimp simp: multiset_eq_iff)

lemma insert_DiffM2 [simp]:
"x \<in># M \<Longrightarrow> M - {#x#} + {#x#} = M"
by (clarsimp simp: multiset_eq_iff)

lemma diff_right_commute:
"(M::'a multiset) - N - Q = M - Q - N"

"(M::'a multiset) - (N + Q) = M - N - Q"

lemma diff_union_swap:
"a \<noteq> b \<Longrightarrow> M - {#a#} + {#b#} = M + {#b#} - {#a#}"

lemma diff_union_single_conv:
"a \<in># J \<Longrightarrow> I + J - {#a#} = I + (J - {#a#})"

subsubsection {* Equality of multisets *}

lemma single_not_empty [simp]: "{#a#} \<noteq> {#} \<and> {#} \<noteq> {#a#}"

lemma single_eq_single [simp]: "{#a#} = {#b#} \<longleftrightarrow> a = b"

lemma union_eq_empty [iff]: "M + N = {#} \<longleftrightarrow> M = {#} \<and> N = {#}"

lemma empty_eq_union [iff]: "{#} = M + N \<longleftrightarrow> M = {#} \<and> N = {#}"

lemma multi_self_add_other_not_self [simp]: "M = M + {#x#} \<longleftrightarrow> False"

lemma diff_single_trivial:
"\<not> x \<in># M \<Longrightarrow> M - {#x#} = M"

lemma diff_single_eq_union:
"x \<in># M \<Longrightarrow> M - {#x#} = N \<longleftrightarrow> M = N + {#x#}"
by auto

lemma union_single_eq_diff:
"M + {#x#} = N \<Longrightarrow> M = N - {#x#}"
by (auto dest: sym)

lemma union_single_eq_member:
"M + {#x#} = N \<Longrightarrow> x \<in># N"
by auto

lemma union_is_single:
"M + N = {#a#} \<longleftrightarrow> M = {#a#} \<and> N={#} \<or> M = {#} \<and> N = {#a#}" (is "?lhs = ?rhs")proof
assume ?rhs then show ?lhs by auto
next
assume ?lhs thus ?rhs
qed

lemma single_is_union:
"{#a#} = M + N \<longleftrightarrow> {#a#} = M \<and> N = {#} \<or> M = {#} \<and> {#a#} = N"
by (auto simp add: eq_commute [of "{#a#}" "M + N"] union_is_single)

"M + {#a#} = N + {#b#} \<longleftrightarrow> M = N \<and> a = b \<or> M = N - {#a#} + {#b#} \<and> N = M - {#b#} + {#a#}"  (is "?lhs = ?rhs")
(* shorter: by (simp add: multiset_eq_iff) fastforce *)
proof
assume ?rhs then show ?lhs
next
assume ?lhs
show ?rhs
proof (cases "a = b")
case True with `?lhs` show ?thesis by simp
next
case False
from `?lhs` have "a \<in># N + {#b#}" by (rule union_single_eq_member)
with False have "a \<in># N" by auto
moreover from `?lhs` have "M = N + {#b#} - {#a#}" by (rule union_single_eq_diff)
moreover note False
ultimately show ?thesis by (auto simp add: diff_right_commute [of _ "{#a#}"] diff_union_swap)
qed
qed

lemma insert_noteq_member:
assumes BC: "B + {#b#} = C + {#c#}"
and bnotc: "b \<noteq> c"
shows "c \<in># B"
proof -
have "c \<in># C + {#c#}" by simp
have nc: "\<not> c \<in># {#b#}" using bnotc by simp
then have "c \<in># B + {#b#}" using BC by simp
then show "c \<in># B" using nc by simp
qed

"(M + {#a#} = N + {#b#}) =
(M = N \<and> a = b \<or> (\<exists>K. M = K + {#b#} \<and> N = K + {#a#}))"

subsubsection {* Pointwise ordering induced by count *}

begin

definition less_eq_multiset :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> bool" where
mset_le_def: "A \<le> B \<longleftrightarrow> (\<forall>a. count A a \<le> count B a)"

definition less_multiset :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> bool" where
mset_less_def: "(A::'a multiset) < B \<longleftrightarrow> A \<le> B \<and> A \<noteq> B"

instance proof
qed (auto simp add: mset_le_def mset_less_def multiset_eq_iff intro: order_trans antisym)

end

lemma mset_less_eqI:
"(\<And>x. count A x \<le> count B x) \<Longrightarrow> A \<le> B"

lemma mset_le_exists_conv:
"(A::'a multiset) \<le> B \<longleftrightarrow> (\<exists>C. B = A + C)"
apply (unfold mset_le_def, rule iffI, rule_tac x = "B - A" in exI)
apply (auto intro: multiset_eq_iff [THEN iffD2])
done

"(A::'a multiset) + C \<le> B + C \<longleftrightarrow> A \<le> B"

"C + (A::'a multiset) \<le> C + B \<longleftrightarrow> A \<le> B"

"(A::'a multiset) \<le> B \<Longrightarrow> C \<le> D \<Longrightarrow> A + C \<le> B + D"

"(A::'a multiset) \<le> A + B"
unfolding mset_le_def by auto

"B \<le> (A::'a multiset) + B"
unfolding mset_le_def by auto

lemma mset_le_single:
"a :# B \<Longrightarrow> {#a#} \<le> B"

lemma multiset_diff_union_assoc:
"C \<le> B \<Longrightarrow> (A::'a multiset) + B - C = A + (B - C)"

lemma mset_le_multiset_union_diff_commute:
"B \<le> A \<Longrightarrow> (A::'a multiset) - B + C = A + C - B"

lemma diff_le_self[simp]: "(M::'a multiset) - N \<le> M"

lemma mset_lessD: "A < B \<Longrightarrow> x \<in># A \<Longrightarrow> x \<in># B"
apply (clarsimp simp: mset_le_def mset_less_def)
apply (erule_tac x=x in allE)
apply auto
done

lemma mset_leD: "A \<le> B \<Longrightarrow> x \<in># A \<Longrightarrow> x \<in># B"
apply (clarsimp simp: mset_le_def mset_less_def)
apply (erule_tac x = x in allE)
apply auto
done

lemma mset_less_insertD: "(A + {#x#} < B) \<Longrightarrow> (x \<in># B \<and> A < B)"
apply (rule conjI)
apply (clarsimp simp: mset_le_def mset_less_def)
apply safe
apply (erule_tac x = a in allE)
apply (auto split: split_if_asm)
done

lemma mset_le_insertD: "(A + {#x#} \<le> B) \<Longrightarrow> (x \<in># B \<and> A \<le> B)"
apply (rule conjI)
apply (force simp: mset_le_def mset_less_def split: split_if_asm)
done

lemma mset_less_of_empty[simp]: "A < {#} \<longleftrightarrow> False"
by (auto simp add: mset_less_def mset_le_def multiset_eq_iff)

lemma multi_psub_of_add_self[simp]: "A < A + {#x#}"
by (auto simp: mset_le_def mset_less_def)

lemma multi_psub_self[simp]: "(A::'a multiset) < A = False"
by simp

"T + {#x#} < S + {#x#} \<Longrightarrow> T < S"

lemma mset_less_empty_nonempty:
"{#} < S \<longleftrightarrow> S \<noteq> {#}"
by (auto simp: mset_le_def mset_less_def)

lemma mset_less_diff_self:
"c \<in># B \<Longrightarrow> B - {#c#} < B"
by (auto simp: mset_le_def mset_less_def multiset_eq_iff)

subsubsection {* Intersection *}

instantiation multiset :: (type) semilattice_inf
begin

definition inf_multiset :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> 'a multiset" where
multiset_inter_def: "inf_multiset A B = A - (A - B)"

instance proof -
have aux: "\<And>m n q :: nat. m \<le> n \<Longrightarrow> m \<le> q \<Longrightarrow> m \<le> n - (n - q)" by arith
show "OFCLASS('a multiset, semilattice_inf_class)" proof
qed (auto simp add: multiset_inter_def mset_le_def aux)
qed

end

abbreviation multiset_inter :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> 'a multiset" (infixl "#\<inter>" 70) where
"multiset_inter \<equiv> inf"

lemma multiset_inter_count [simp]:
"count (A #\<inter> B) x = min (count A x) (count B x)"

lemma multiset_inter_single: "a \<noteq> b \<Longrightarrow> {#a#} #\<inter> {#b#} = {#}"
by (rule multiset_eqI) (auto simp add: multiset_inter_count)

lemma multiset_union_diff_commute:
assumes "B #\<inter> C = {#}"
shows "A + B - C = A - C + B"
proof (rule multiset_eqI)
fix x
from assms have "min (count B x) (count C x) = 0"
by (auto simp add: multiset_inter_count multiset_eq_iff)
then have "count B x = 0 \<or> count C x = 0"
by auto
then show "count (A + B - C) x = count (A - C + B) x"
by auto
qed

subsubsection {* Filter (with comprehension syntax) *}

text {* Multiset comprehension *}

definition filter :: "('a \<Rightarrow> bool) \<Rightarrow> 'a multiset \<Rightarrow> 'a multiset" where
"filter P M = Abs_multiset (\<lambda>x. if P x then count M x else 0)"

hide_const (open) filter

lemma count_filter [simp]:
"count (Multiset.filter P M) a = (if P a then count M a else 0)"
by (simp add: filter_def in_multiset multiset_typedef)

lemma filter_empty [simp]:
"Multiset.filter P {#} = {#}"
by (rule multiset_eqI) simp

lemma filter_single [simp]:
"Multiset.filter P {#x#} = (if P x then {#x#} else {#})"
by (rule multiset_eqI) simp

lemma filter_union [simp]:
"Multiset.filter P (M + N) = Multiset.filter P M + Multiset.filter P N"
by (rule multiset_eqI) simp

lemma filter_diff [simp]:
"Multiset.filter P (M - N) = Multiset.filter P M - Multiset.filter P N"
by (rule multiset_eqI) simp

lemma filter_inter [simp]:
"Multiset.filter P (M #\<inter> N) = Multiset.filter P M #\<inter> Multiset.filter P N"
by (rule multiset_eqI) simp

syntax
"_MCollect" :: "pttrn \<Rightarrow> 'a multiset \<Rightarrow> bool \<Rightarrow> 'a multiset"    ("(1{# _ :# _./ _#})")
syntax (xsymbol)
"_MCollect" :: "pttrn \<Rightarrow> 'a multiset \<Rightarrow> bool \<Rightarrow> 'a multiset"    ("(1{# _ \<in># _./ _#})")
translations
"{#x \<in># M. P#}" == "CONST Multiset.filter (\<lambda>x. P) M"

subsubsection {* Set of elements *}

definition set_of :: "'a multiset => 'a set" where
"set_of M = {x. x :# M}"

lemma set_of_empty [simp]: "set_of {#} = {}"

lemma set_of_single [simp]: "set_of {#b#} = {b}"

lemma set_of_union [simp]: "set_of (M + N) = set_of M \<union> set_of N"

lemma set_of_eq_empty_iff [simp]: "(set_of M = {}) = (M = {#})"
by (auto simp add: set_of_def multiset_eq_iff)

lemma mem_set_of_iff [simp]: "(x \<in> set_of M) = (x :# M)"

lemma set_of_filter [simp]: "set_of {# x:#M. P x #} = set_of M \<inter> {x. P x}"

lemma finite_set_of [iff]: "finite (set_of M)"
using count [of M] by (simp add: multiset_def set_of_def)

subsubsection {* Size *}

instantiation multiset :: (type) size
begin

definition size_def:
"size M = setsum (count M) (set_of M)"

instance ..

end

lemma size_empty [simp]: "size {#} = 0"

lemma size_single [simp]: "size {#b#} = 1"

lemma setsum_count_Int:
"finite A ==> setsum (count N) (A \<inter> set_of N) = setsum (count N) A"
apply (induct rule: finite_induct)
apply simp
done

lemma size_union [simp]: "size (M + N::'a multiset) = size M + size N"
apply (unfold size_def)
apply (subgoal_tac "count (M + N) = (\<lambda>a. count M a + count N a)")
prefer 2
apply (rule ext, simp)
apply (subst Int_commute)
done

lemma size_eq_0_iff_empty [iff]: "(size M = 0) = (M = {#})"
by (auto simp add: size_def multiset_eq_iff)

lemma nonempty_has_size: "(S \<noteq> {#}) = (0 < size S)"
by (metis gr0I gr_implies_not0 size_empty size_eq_0_iff_empty)

lemma size_eq_Suc_imp_elem: "size M = Suc n ==> \<exists>a. a :# M"
apply (unfold size_def)
apply (drule setsum_SucD)
apply auto
done

lemma size_eq_Suc_imp_eq_union:
assumes "size M = Suc n"
shows "\<exists>a N. M = N + {#a#}"
proof -
from assms obtain a where "a \<in># M"
by (erule size_eq_Suc_imp_elem [THEN exE])
then have "M = M - {#a#} + {#a#}" by simp
then show ?thesis by blast
qed

subsection {* Induction and case splits *}

lemma setsum_decr:
"finite F ==> (0::nat) < f a ==>
setsum (f (a := f a - 1)) F = (if a\<in>F then setsum f F - 1 else setsum f F)"
apply (induct rule: finite_induct)
apply auto
apply (drule_tac a = a in mk_disjoint_insert, auto)
done

lemma rep_multiset_induct_aux:
assumes 1: "P (\<lambda>a. (0::nat))"
and 2: "!!f b. f \<in> multiset ==> P f ==> P (f (b := f b + 1))"
shows "\<forall>f. f \<in> multiset --> setsum f {x. f x \<noteq> 0} = n --> P f"
apply (unfold multiset_def)
apply (induct_tac n, simp, clarify)
apply (subgoal_tac "f = (\<lambda>a.0)")
apply simp
apply (rule 1)
apply (rule ext, force, clarify)
apply (frule setsum_SucD, clarify)
apply (rename_tac a)
apply (subgoal_tac "finite {x. (f (a := f a - 1)) x > 0}")
prefer 2
apply (rule finite_subset)
prefer 2
apply assumption
apply simp
apply blast
apply (subgoal_tac "f = (f (a := f a - 1))(a := (f (a := f a - 1)) a + 1)")
prefer 2
apply (rule ext)
apply (simp (no_asm_simp))
apply (erule ssubst, rule 2 [unfolded multiset_def], blast)
apply (erule allE, erule impE, erule_tac [2] mp, blast)
apply (simp (no_asm_simp) add: setsum_decr del: fun_upd_apply One_nat_def)
apply (subgoal_tac "{x. x \<noteq> a --> f x \<noteq> 0} = {x. f x \<noteq> 0}")
prefer 2
apply blast
apply (subgoal_tac "{x. x \<noteq> a \<and> f x \<noteq> 0} = {x. f x \<noteq> 0} - {a}")
prefer 2
apply blast
done

theorem rep_multiset_induct:
"f \<in> multiset ==> P (\<lambda>a. 0) ==>
(!!f b. f \<in> multiset ==> P f ==> P (f (b := f b + 1))) ==> P f"
using rep_multiset_induct_aux by blast

theorem multiset_induct [case_names empty add, induct type: multiset]:
assumes empty: "P {#}"
and add: "!!M x. P M ==> P (M + {#x#})"
shows "P M"
proof -
note defns = union_def single_def Mempty_def
have aux: "\<And>a::'a. count (Abs_multiset (\<lambda>b. if b = a then 1 else 0)) =
(\<lambda>b. if b = a then 1 else 0)" by (simp add: Abs_multiset_inverse in_multiset)
show ?thesis
apply (rule count_inverse [THEN subst])
apply (rule count [THEN rep_multiset_induct])
apply (rule empty [unfolded defns])
apply (subgoal_tac "f(b := f b + 1) = (\<lambda>a. f a + (if a=b then 1 else 0))")
prefer 2
apply (erule ssubst)
apply (erule Abs_multiset_inverse [THEN subst])
done
qed

lemma multi_nonempty_split: "M \<noteq> {#} \<Longrightarrow> \<exists>A a. M = A + {#a#}"
by (induct M) auto

lemma multiset_cases [cases type, case_names empty add]:
assumes em:  "M = {#} \<Longrightarrow> P"
assumes add: "\<And>N x. M = N + {#x#} \<Longrightarrow> P"
shows "P"
proof (cases "M = {#}")
assume "M = {#}" then show ?thesis using em by simp
next
assume "M \<noteq> {#}"
then obtain M' m where "M = M' + {#m#}"
by (blast dest: multi_nonempty_split)
then show ?thesis using add by simp
qed

lemma multi_member_split: "x \<in># M \<Longrightarrow> \<exists>A. M = A + {#x#}"
apply (cases M)
apply simp
apply (rule_tac x="M - {#x#}" in exI, simp)
done

lemma multi_drop_mem_not_eq: "c \<in># B \<Longrightarrow> B - {#c#} \<noteq> B"
by (cases "B = {#}") (auto dest: multi_member_split)

lemma multiset_partition: "M = {# x:#M. P x #} + {# x:#M. \<not> P x #}"
apply (subst multiset_eq_iff)
apply auto
done

lemma mset_less_size: "(A::'a multiset) < B \<Longrightarrow> size A < size B"
proof (induct A arbitrary: B)
case (empty M)
then have "M \<noteq> {#}" by (simp add: mset_less_empty_nonempty)
then obtain M' x where "M = M' + {#x#}"
by (blast dest: multi_nonempty_split)
then show ?case by simp
next
have IH: "\<And>B. S < B \<Longrightarrow> size S < size B" by fact
have SxsubT: "S + {#x#} < T" by fact
then have "x \<in># T" and "S < T" by (auto dest: mset_less_insertD)
then obtain T' where T: "T = T' + {#x#}"
by (blast dest: multi_member_split)
then have "S < T'" using SxsubT
then have "size S < size T'" using IH by simp
then show ?case using T by simp
qed

subsubsection {* Strong induction and subset induction for multisets *}

text {* Well-foundedness of proper subset operator: *}

text {* proper multiset subset *}

definition
mset_less_rel :: "('a multiset * 'a multiset) set" where
"mset_less_rel = {(A,B). A < B}"

assumes "c \<in># B" and "b \<noteq> c"
shows "B - {#c#} + {#b#} = B + {#b#} - {#c#}"
proof -
from `c \<in># B` obtain A where B: "B = A + {#c#}"
by (blast dest: multi_member_split)
have "A + {#b#} = A + {#b#} + {#c#} - {#c#}" by simp
then have "A + {#b#} = A + {#c#} + {#b#} - {#c#}"
then show ?thesis using B by simp
qed

lemma wf_mset_less_rel: "wf mset_less_rel"
apply (unfold mset_less_rel_def)
apply (rule wf_measure [THEN wf_subset, where f1=size])
apply (clarsimp simp: measure_def inv_image_def mset_less_size)
done

text {* The induction rules: *}

lemma full_multiset_induct [case_names less]:
assumes ih: "\<And>B. \<forall>(A::'a multiset). A < B \<longrightarrow> P A \<Longrightarrow> P B"
shows "P B"
apply (rule wf_mset_less_rel [THEN wf_induct])
apply (rule ih, auto simp: mset_less_rel_def)
done

lemma multi_subset_induct [consumes 2, case_names empty add]:
assumes "F \<le> A"
and empty: "P {#}"
and insert: "\<And>a F. a \<in># A \<Longrightarrow> P F \<Longrightarrow> P (F + {#a#})"
shows "P F"
proof -
from `F \<le> A`
show ?thesis
proof (induct F)
show "P {#}" by fact
next
fix x F
assume P: "F \<le> A \<Longrightarrow> P F" and i: "F + {#x#} \<le> A"
show "P (F + {#x#})"
proof (rule insert)
from i show "x \<in># A" by (auto dest: mset_le_insertD)
from i have "F \<le> A" by (auto dest: mset_le_insertD)
with P show "P F" .
qed
qed
qed

subsection {* Alternative representations *}

subsubsection {* Lists *}

primrec multiset_of :: "'a list \<Rightarrow> 'a multiset" where
"multiset_of [] = {#}" |
"multiset_of (a # x) = multiset_of x + {# a #}"

lemma in_multiset_in_set:
"x \<in># multiset_of xs \<longleftrightarrow> x \<in> set xs"
by (induct xs) simp_all

lemma count_multiset_of:
"count (multiset_of xs) x = length (filter (\<lambda>y. x = y) xs)"
by (induct xs) simp_all

lemma multiset_of_zero_iff[simp]: "(multiset_of x = {#}) = (x = [])"
by (induct x) auto

lemma multiset_of_zero_iff_right[simp]: "({#} = multiset_of x) = (x = [])"
by (induct x) auto

lemma set_of_multiset_of[simp]: "set_of (multiset_of x) = set x"
by (induct x) auto

lemma mem_set_multiset_eq: "x \<in> set xs = (x :# multiset_of xs)"
by (induct xs) auto

lemma multiset_of_append [simp]:
"multiset_of (xs @ ys) = multiset_of xs + multiset_of ys"
by (induct xs arbitrary: ys) (auto simp: add_ac)

lemma multiset_of_filter:
"multiset_of (filter P xs) = {#x :# multiset_of xs. P x #}"
by (induct xs) simp_all

lemma multiset_of_rev [simp]:
"multiset_of (rev xs) = multiset_of xs"
by (induct xs) simp_all

lemma surj_multiset_of: "surj multiset_of"
apply (unfold surj_def)
apply (rule allI)
apply (rule_tac M = y in multiset_induct)
apply auto
apply (rule_tac x = "x # xa" in exI)
apply auto
done

lemma set_count_greater_0: "set x = {a. count (multiset_of x) a > 0}"
by (induct x) auto

lemma distinct_count_atmost_1:
"distinct x = (! a. count (multiset_of x) a = (if a \<in> set x then 1 else 0))"
apply (induct x, simp, rule iffI, simp_all)
apply (rule conjI)
apply (simp_all add: set_of_multiset_of [THEN sym] del: set_of_multiset_of)
apply (erule_tac x = a in allE, simp, clarify)
apply (erule_tac x = aa in allE, simp)
done

lemma multiset_of_eq_setD:
"multiset_of xs = multiset_of ys \<Longrightarrow> set xs = set ys"
by (rule) (auto simp add:multiset_eq_iff set_count_greater_0)

lemma set_eq_iff_multiset_of_eq_distinct:
"distinct x \<Longrightarrow> distinct y \<Longrightarrow>
(set x = set y) = (multiset_of x = multiset_of y)"
by (auto simp: multiset_eq_iff distinct_count_atmost_1)

lemma set_eq_iff_multiset_of_remdups_eq:
"(set x = set y) = (multiset_of (remdups x) = multiset_of (remdups y))"
apply (rule iffI)
apply (drule distinct_remdups [THEN distinct_remdups
[THEN set_eq_iff_multiset_of_eq_distinct [THEN iffD2]]])
apply simp
done

lemma multiset_of_compl_union [simp]:
"multiset_of [x\<leftarrow>xs. P x] + multiset_of [x\<leftarrow>xs. \<not>P x] = multiset_of xs"
by (induct xs) (auto simp: add_ac)

lemma count_multiset_of_length_filter:
"count (multiset_of xs) x = length (filter (\<lambda>y. x = y) xs)"
by (induct xs) auto

lemma nth_mem_multiset_of: "i < length ls \<Longrightarrow> (ls ! i) :# multiset_of ls"
apply (induct ls arbitrary: i)
apply simp
apply (case_tac i)
apply auto
done

lemma multiset_of_remove1[simp]:
"multiset_of (remove1 a xs) = multiset_of xs - {#a#}"
by (induct xs) (auto simp add: multiset_eq_iff)

lemma multiset_of_eq_length:
assumes "multiset_of xs = multiset_of ys"
shows "length xs = length ys"
using assms proof (induct xs arbitrary: ys)
case Nil then show ?case by simp
next
case (Cons x xs)
then have "x \<in># multiset_of ys" by (simp add: union_single_eq_member)
then have "x \<in> set ys" by (simp add: in_multiset_in_set)
from Cons.prems [symmetric] have "multiset_of xs = multiset_of (remove1 x ys)"
by simp
with Cons.hyps have "length xs = length (remove1 x ys)" .
with `x \<in> set ys` show ?case
by (auto simp add: length_remove1 dest: length_pos_if_in_set)
qed

lemma multiset_of_eq_length_filter:
assumes "multiset_of xs = multiset_of ys"
shows "length (filter (\<lambda>x. z = x) xs) = length (filter (\<lambda>y. z = y) ys)"
proof (cases "z \<in># multiset_of xs")
case False
moreover have "\<not> z \<in># multiset_of ys" using assms False by simp
ultimately show ?thesis by (simp add: count_multiset_of_length_filter)
next
case True
moreover have "z \<in># multiset_of ys" using assms True by simp
show ?thesis using assms proof (induct xs arbitrary: ys)
case Nil then show ?case by simp
next
case (Cons x xs)
from `multiset_of (x # xs) = multiset_of ys` [symmetric]
have *: "multiset_of xs = multiset_of (remove1 x ys)"
and "x \<in> set ys"
from * have "length (filter (\<lambda>x. z = x) xs) = length (filter (\<lambda>y. z = y) (remove1 x ys))" by (rule Cons.hyps)
moreover from `x \<in> set ys` have "length (filter (\<lambda>y. x = y) ys) > 0" by (simp add: filter_empty_conv)
ultimately show ?case using `x \<in> set ys`
qed
qed

lemma fold_multiset_equiv:
assumes f: "\<And>x y. x \<in> set xs \<Longrightarrow> y \<in> set xs \<Longrightarrow> f x \<circ> f y = f y \<circ> f x"
and equiv: "multiset_of xs = multiset_of ys"
shows "fold f xs = fold f ys"
using f equiv [symmetric] proof (induct xs arbitrary: ys)
case Nil then show ?case by simp
next
case (Cons x xs)
then have *: "set ys = set (x # xs)" by (blast dest: multiset_of_eq_setD)
have "\<And>x y. x \<in> set ys \<Longrightarrow> y \<in> set ys \<Longrightarrow> f x \<circ> f y = f y \<circ> f x"
by (rule Cons.prems(1)) (simp_all add: *)
moreover from * have "x \<in> set ys" by simp
ultimately have "fold f ys = fold f (remove1 x ys) \<circ> f x" by (fact fold_remove1_split)
moreover from Cons.prems have "fold f xs = fold f (remove1 x ys)" by (auto intro: Cons.hyps)
ultimately show ?case by simp
qed

context linorder
begin

lemma multiset_of_insort [simp]:
"multiset_of (insort_key k x xs) = {#x#} + multiset_of xs"
by (induct xs) (simp_all add: ac_simps)

lemma multiset_of_sort [simp]:
"multiset_of (sort_key k xs) = multiset_of xs"
by (induct xs) (simp_all add: ac_simps)

text {*
This lemma shows which properties suffice to show that a function
@{text "f"} with @{text "f xs = ys"} behaves like sort.
*}

lemma properties_for_sort_key:
assumes "multiset_of ys = multiset_of xs"
and "\<And>k. k \<in> set ys \<Longrightarrow> filter (\<lambda>x. f k = f x) ys = filter (\<lambda>x. f k = f x) xs"
and "sorted (map f ys)"
shows "sort_key f xs = ys"
using assms proof (induct xs arbitrary: ys)
case Nil then show ?case by simp
next
case (Cons x xs)
from Cons.prems(2) have
"\<forall>k \<in> set ys. filter (\<lambda>x. f k = f x) (remove1 x ys) = filter (\<lambda>x. f k = f x) xs"
with Cons.prems have "sort_key f xs = remove1 x ys"
by (auto intro!: Cons.hyps simp add: sorted_map_remove1)
moreover from Cons.prems have "x \<in> set ys"
by (auto simp add: mem_set_multiset_eq intro!: ccontr)
ultimately show ?case using Cons.prems by (simp add: insort_key_remove1)
qed

lemma properties_for_sort:
assumes multiset: "multiset_of ys = multiset_of xs"
and "sorted ys"
shows "sort xs = ys"
proof (rule properties_for_sort_key)
from multiset show "multiset_of ys = multiset_of xs" .
from `sorted ys` show "sorted (map (\<lambda>x. x) ys)" by simp
from multiset have "\<And>k. length (filter (\<lambda>y. k = y) ys) = length (filter (\<lambda>x. k = x) xs)"
by (rule multiset_of_eq_length_filter)
then have "\<And>k. replicate (length (filter (\<lambda>y. k = y) ys)) k = replicate (length (filter (\<lambda>x. k = x) xs)) k"
by simp
then show "\<And>k. k \<in> set ys \<Longrightarrow> filter (\<lambda>y. k = y) ys = filter (\<lambda>x. k = x) xs"
qed

lemma sort_key_by_quicksort:
"sort_key f xs = sort_key f [x\<leftarrow>xs. f x < f (xs ! (length xs div 2))]
@ [x\<leftarrow>xs. f x = f (xs ! (length xs div 2))]
@ sort_key f [x\<leftarrow>xs. f x > f (xs ! (length xs div 2))]" (is "sort_key f ?lhs = ?rhs")
proof (rule properties_for_sort_key)
show "multiset_of ?rhs = multiset_of ?lhs"
by (rule multiset_eqI) (auto simp add: multiset_of_filter)
next
show "sorted (map f ?rhs)"
by (auto simp add: sorted_append intro: sorted_map_same)
next
fix l
assume "l \<in> set ?rhs"
let ?pivot = "f (xs ! (length xs div 2))"
have *: "\<And>x. f l = f x \<longleftrightarrow> f x = f l" by auto
have "[x \<leftarrow> sort_key f xs . f x = f l] = [x \<leftarrow> xs. f x = f l]"
unfolding filter_sort by (rule properties_for_sort_key) (auto intro: sorted_map_same)
with * have **: "[x \<leftarrow> sort_key f xs . f l = f x] = [x \<leftarrow> xs. f l = f x]" by simp
have "\<And>x P. P (f x) ?pivot \<and> f l = f x \<longleftrightarrow> P (f l) ?pivot \<and> f l = f x" by auto
then have "\<And>P. [x \<leftarrow> sort_key f xs . P (f x) ?pivot \<and> f l = f x] =
[x \<leftarrow> sort_key f xs. P (f l) ?pivot \<and> f l = f x]" by simp
note *** = this [of "op <"] this [of "op >"] this [of "op ="]
show "[x \<leftarrow> ?rhs. f l = f x] = [x \<leftarrow> ?lhs. f l = f x]"
proof (cases "f l" ?pivot rule: linorder_cases)
case less then moreover have "f l \<noteq> ?pivot" and "\<not> f l > ?pivot" by auto
ultimately show ?thesis
by (simp add: filter_sort [symmetric] ** ***)
next
case equal then show ?thesis
next
case greater then moreover have "f l \<noteq> ?pivot" and "\<not> f l < ?pivot" by auto
ultimately show ?thesis
by (simp add: filter_sort [symmetric] ** ***)
qed
qed

lemma sort_by_quicksort:
"sort xs = sort [x\<leftarrow>xs. x < xs ! (length xs div 2)]
@ [x\<leftarrow>xs. x = xs ! (length xs div 2)]
@ sort [x\<leftarrow>xs. x > xs ! (length xs div 2)]" (is "sort ?lhs = ?rhs")
using sort_key_by_quicksort [of "\<lambda>x. x", symmetric] by simp

text {* A stable parametrized quicksort *}

definition part :: "('b \<Rightarrow> 'a) \<Rightarrow> 'a \<Rightarrow> 'b list \<Rightarrow> 'b list \<times> 'b list \<times> 'b list" where
"part f pivot xs = ([x \<leftarrow> xs. f x < pivot], [x \<leftarrow> xs. f x = pivot], [x \<leftarrow> xs. pivot < f x])"

lemma part_code [code]:
"part f pivot [] = ([], [], [])"
"part f pivot (x # xs) = (let (lts, eqs, gts) = part f pivot xs; x' = f x in
if x' < pivot then (x # lts, eqs, gts)
else if x' > pivot then (lts, eqs, x # gts)
else (lts, x # eqs, gts))"
by (auto simp add: part_def Let_def split_def)

lemma sort_key_by_quicksort_code [code]:
"sort_key f xs = (case xs of [] \<Rightarrow> []
| [x] \<Rightarrow> xs
| [x, y] \<Rightarrow> (if f x \<le> f y then xs else [y, x])
| _ \<Rightarrow> (let (lts, eqs, gts) = part f (f (xs ! (length xs div 2))) xs
in sort_key f lts @ eqs @ sort_key f gts))"
proof (cases xs)
case Nil then show ?thesis by simp
next
case (Cons _ ys) note hyps = Cons show ?thesis proof (cases ys)
case Nil with hyps show ?thesis by simp
next
case (Cons _ zs) note hyps = hyps Cons show ?thesis proof (cases zs)
case Nil with hyps show ?thesis by auto
next
case Cons
from sort_key_by_quicksort [of f xs]
have "sort_key f xs = (let (lts, eqs, gts) = part f (f (xs ! (length xs div 2))) xs
in sort_key f lts @ eqs @ sort_key f gts)"
by (simp only: split_def Let_def part_def fst_conv snd_conv)
with hyps Cons show ?thesis by (simp only: list.cases)
qed
qed
qed

end

hide_const (open) part

lemma multiset_of_remdups_le: "multiset_of (remdups xs) \<le> multiset_of xs"
by (induct xs) (auto intro: order_trans)

lemma multiset_of_update:
"i < length ls \<Longrightarrow> multiset_of (ls[i := v]) = multiset_of ls - {#ls ! i#} + {#v#}"
proof (induct ls arbitrary: i)
case Nil then show ?case by simp
next
case (Cons x xs)
show ?case
proof (cases i)
case 0 then show ?thesis by simp
next
case (Suc i')
with Cons show ?thesis
apply simp
apply (subst add_commute [of "{#v#}" "{#x#}"])
apply simp
apply (rule mset_le_multiset_union_diff_commute)
done
qed
qed

lemma multiset_of_swap:
"i < length ls \<Longrightarrow> j < length ls \<Longrightarrow>
multiset_of (ls[j := ls ! i, i := ls ! j]) = multiset_of ls"
by (cases "i = j") (simp_all add: multiset_of_update nth_mem_multiset_of)

subsubsection {* Association lists -- including rudimentary code generation *}

definition count_of :: "('a \<times> nat) list \<Rightarrow> 'a \<Rightarrow> nat" where
"count_of xs x = (case map_of xs x of None \<Rightarrow> 0 | Some n \<Rightarrow> n)"

lemma count_of_multiset:
"count_of xs \<in> multiset"
proof -
let ?A = "{x::'a. 0 < (case map_of xs x of None \<Rightarrow> 0\<Colon>nat | Some (n\<Colon>nat) \<Rightarrow> n)}"
have "?A \<subseteq> dom (map_of xs)"
proof
fix x
assume "x \<in> ?A"
then have "0 < (case map_of xs x of None \<Rightarrow> 0\<Colon>nat | Some (n\<Colon>nat) \<Rightarrow> n)" by simp
then have "map_of xs x \<noteq> None" by (cases "map_of xs x") auto
then show "x \<in> dom (map_of xs)" by auto
qed
with finite_dom_map_of [of xs] have "finite ?A"
by (auto intro: finite_subset)
then show ?thesis
by (simp add: count_of_def fun_eq_iff multiset_def)
qed

lemma count_simps [simp]:
"count_of [] = (\<lambda>_. 0)"
"count_of ((x, n) # xs) = (\<lambda>y. if x = y then n else count_of xs y)"

lemma count_of_empty:
"x \<notin> fst ` set xs \<Longrightarrow> count_of xs x = 0"
by (induct xs) (simp_all add: count_of_def)

lemma count_of_filter:
"count_of (filter (P \<circ> fst) xs) x = (if P x then count_of xs x else 0)"
by (induct xs) auto

definition Bag :: "('a \<times> nat) list \<Rightarrow> 'a multiset" where
"Bag xs = Abs_multiset (count_of xs)"

code_datatype Bag

lemma count_Bag [simp, code]:
"count (Bag xs) = count_of xs"
by (simp add: Bag_def count_of_multiset Abs_multiset_inverse)

lemma Mempty_Bag [code]:
"{#} = Bag []"

lemma single_Bag [code]:
"{#x#} = Bag [(x, 1)]"

lemma filter_Bag [code]:
"Multiset.filter P (Bag xs) = Bag (filter (P \<circ> fst) xs)"
by (rule multiset_eqI) (simp add: count_of_filter)

lemma mset_less_eq_Bag [code]:
"Bag xs \<le> A \<longleftrightarrow> (\<forall>(x, n) \<in> set xs. count_of xs x \<le> count A x)"
(is "?lhs \<longleftrightarrow> ?rhs")
proof
assume ?lhs then show ?rhs
by (auto simp add: mset_le_def count_Bag)
next
assume ?rhs
show ?lhs
proof (rule mset_less_eqI)
fix x
from `?rhs` have "count_of xs x \<le> count A x"
by (cases "x \<in> fst ` set xs") (auto simp add: count_of_empty)
then show "count (Bag xs) x \<le> count A x"
qed
qed

instantiation multiset :: (equal) equal
begin

definition
[code]: "HOL.equal A B \<longleftrightarrow> (A::'a multiset) \<le> B \<and> B \<le> A"

instance proof

end

lemma [code nbe]:
"HOL.equal (A :: 'a::equal multiset) A \<longleftrightarrow> True"
by (fact equal_refl)

definition (in term_syntax)
bagify :: "('a\<Colon>typerep \<times> nat) list \<times> (unit \<Rightarrow> Code_Evaluation.term)
\<Rightarrow> 'a multiset \<times> (unit \<Rightarrow> Code_Evaluation.term)" where
[code_unfold]: "bagify xs = Code_Evaluation.valtermify Bag {\<cdot>} xs"

notation fcomp (infixl "\<circ>>" 60)
notation scomp (infixl "\<circ>\<rightarrow>" 60)

instantiation multiset :: (random) random
begin

definition
"Quickcheck.random i = Quickcheck.random i \<circ>\<rightarrow> (\<lambda>xs. Pair (bagify xs))"

instance ..

end

no_notation fcomp (infixl "\<circ>>" 60)
no_notation scomp (infixl "\<circ>\<rightarrow>" 60)

hide_const (open) bagify

subsection {* The multiset order *}

subsubsection {* Well-foundedness *}

definition mult1 :: "('a \<times> 'a) set => ('a multiset \<times> 'a multiset) set" where
"mult1 r = {(N, M). \<exists>a M0 K. M = M0 + {#a#} \<and> N = M0 + K \<and>
(\<forall>b. b :# K --> (b, a) \<in> r)}"

definition mult :: "('a \<times> 'a) set => ('a multiset \<times> 'a multiset) set" where
"mult r = (mult1 r)\<^sup>+"

lemma not_less_empty [iff]: "(M, {#}) \<notin> mult1 r"

lemma less_add: "(N, M0 + {#a#}) \<in> mult1 r ==>
(\<exists>M. (M, M0) \<in> mult1 r \<and> N = M + {#a#}) \<or>
(\<exists>K. (\<forall>b. b :# K --> (b, a) \<in> r) \<and> N = M0 + K)"
(is "_ \<Longrightarrow> ?case1 (mult1 r) \<or> ?case2")
proof (unfold mult1_def)
let ?r = "\<lambda>K a. \<forall>b. b :# K --> (b, a) \<in> r"
let ?R = "\<lambda>N M. \<exists>a M0 K. M = M0 + {#a#} \<and> N = M0 + K \<and> ?r K a"
let ?case1 = "?case1 {(N, M). ?R N M}"

assume "(N, M0 + {#a#}) \<in> {(N, M). ?R N M}"
then have "\<exists>a' M0' K.
M0 + {#a#} = M0' + {#a'#} \<and> N = M0' + K \<and> ?r K a'" by simp
then show "?case1 \<or> ?case2"
proof (elim exE conjE)
fix a' M0' K
assume N: "N = M0' + K" and r: "?r K a'"
assume "M0 + {#a#} = M0' + {#a'#}"
then have "M0 = M0' \<and> a = a' \<or>
(\<exists>K'. M0 = K' + {#a'#} \<and> M0' = K' + {#a#})"
then show ?thesis
proof (elim disjE conjE exE)
assume "M0 = M0'" "a = a'"
with N r have "?r K a \<and> N = M0 + K" by simp
then have ?case2 .. then show ?thesis ..
next
fix K'
assume "M0' = K' + {#a#}"
with N have n: "N = K' + K + {#a#}" by (simp add: add_ac)

assume "M0 = K' + {#a'#}"
with r have "?R (K' + K) M0" by blast
with n have ?case1 by simp then show ?thesis ..
qed
qed
qed

lemma all_accessible: "wf r ==> \<forall>M. M \<in> acc (mult1 r)"
proof
let ?R = "mult1 r"
let ?W = "acc ?R"
{
fix M M0 a
assume M0: "M0 \<in> ?W"
and wf_hyp: "!!b. (b, a) \<in> r ==> (\<forall>M \<in> ?W. M + {#b#} \<in> ?W)"
and acc_hyp: "\<forall>M. (M, M0) \<in> ?R --> M + {#a#} \<in> ?W"
have "M0 + {#a#} \<in> ?W"
proof (rule accI [of "M0 + {#a#}"])
fix N
assume "(N, M0 + {#a#}) \<in> ?R"
then have "((\<exists>M. (M, M0) \<in> ?R \<and> N = M + {#a#}) \<or>
(\<exists>K. (\<forall>b. b :# K --> (b, a) \<in> r) \<and> N = M0 + K))"
then show "N \<in> ?W"
proof (elim exE disjE conjE)
fix M assume "(M, M0) \<in> ?R" and N: "N = M + {#a#}"
from acc_hyp have "(M, M0) \<in> ?R --> M + {#a#} \<in> ?W" ..
from this and `(M, M0) \<in> ?R` have "M + {#a#} \<in> ?W" ..
then show "N \<in> ?W" by (simp only: N)
next
fix K
assume N: "N = M0 + K"
assume "\<forall>b. b :# K --> (b, a) \<in> r"
then have "M0 + K \<in> ?W"
proof (induct K)
case empty
from M0 show "M0 + {#} \<in> ?W" by simp
next
from add.prems have "(x, a) \<in> r" by simp
with wf_hyp have "\<forall>M \<in> ?W. M + {#x#} \<in> ?W" by blast
moreover from add have "M0 + K \<in> ?W" by simp
ultimately have "(M0 + K) + {#x#} \<in> ?W" ..
then show "M0 + (K + {#x#}) \<in> ?W" by (simp only: add_assoc)
qed
then show "N \<in> ?W" by (simp only: N)
qed
qed
} note tedious_reasoning = this

assume wf: "wf r"
fix M
show "M \<in> ?W"
proof (induct M)
show "{#} \<in> ?W"
proof (rule accI)
fix b assume "(b, {#}) \<in> ?R"
with not_less_empty show "b \<in> ?W" by contradiction
qed

fix M a assume "M \<in> ?W"
from wf have "\<forall>M \<in> ?W. M + {#a#} \<in> ?W"
proof induct
fix a
assume r: "!!b. (b, a) \<in> r ==> (\<forall>M \<in> ?W. M + {#b#} \<in> ?W)"
show "\<forall>M \<in> ?W. M + {#a#} \<in> ?W"
proof
fix M assume "M \<in> ?W"
then show "M + {#a#} \<in> ?W"
by (rule acc_induct) (rule tedious_reasoning [OF _ r])
qed
qed
from this and `M \<in> ?W` show "M + {#a#} \<in> ?W" ..
qed
qed

theorem wf_mult1: "wf r ==> wf (mult1 r)"
by (rule acc_wfI) (rule all_accessible)

theorem wf_mult: "wf r ==> wf (mult r)"
unfolding mult_def by (rule wf_trancl) (rule wf_mult1)

subsubsection {* Closure-free presentation *}

text {* One direction. *}

lemma mult_implies_one_step:
"trans r ==> (M, N) \<in> mult r ==>
\<exists>I J K. N = I + J \<and> M = I + K \<and> J \<noteq> {#} \<and>
(\<forall>k \<in> set_of K. \<exists>j \<in> set_of J. (k, j) \<in> r)"
apply (unfold mult_def mult1_def set_of_def)
apply (erule converse_trancl_induct, clarify)
apply (rule_tac x = M0 in exI, simp, clarify)
apply (case_tac "a :# K")
apply (rule_tac x = I in exI)
apply (simp (no_asm))
apply (rule_tac x = "(K - {#a#}) + Ka" in exI)
apply (drule_tac f = "\<lambda>M. M - {#a#}" in arg_cong)
apply blast
apply (subgoal_tac "a :# I")
apply (rule_tac x = "I - {#a#}" in exI)
apply (rule_tac x = "J + {#a#}" in exI)
apply (rule_tac x = "K + Ka" in exI)
apply (rule conjI)
apply (simp add: multiset_eq_iff split: nat_diff_split)
apply (rule conjI)
apply (drule_tac f = "\<lambda>M. M - {#a#}" in arg_cong, simp)
apply (simp add: multiset_eq_iff split: nat_diff_split)
apply blast
apply (subgoal_tac "a :# (M0 + {#a#})")
apply simp
apply (simp (no_asm))
done

lemma one_step_implies_mult_aux:
"trans r ==>
\<forall>I J K. (size J = n \<and> J \<noteq> {#} \<and> (\<forall>k \<in> set_of K. \<exists>j \<in> set_of J. (k, j) \<in> r))
--> (I + K, I + J) \<in> mult r"
apply (induct_tac n, auto)
apply (frule size_eq_Suc_imp_eq_union, clarify)
apply (rename_tac "J'", simp)
apply (erule notE, auto)
apply (case_tac "J' = {#}")
apply (rule r_into_trancl)
apply (simp add: mult1_def set_of_def, blast)
txt {* Now we know @{term "J' \<noteq> {#}"}. *}
apply (cut_tac M = K and P = "\<lambda>x. (x, a) \<in> r" in multiset_partition)
apply (erule_tac P = "\<forall>k \<in> set_of K. ?P k" in rev_mp)
apply (erule ssubst)
apply (subgoal_tac
"((I + {# x :# K. (x, a) \<in> r #}) + {# x :# K. (x, a) \<notin> r #},
(I + {# x :# K. (x, a) \<in> r #}) + J') \<in> mult r")
prefer 2
apply force
apply (erule trancl_trans)
apply (rule r_into_trancl)
apply (rule_tac x = a in exI)
apply (rule_tac x = "I + J'" in exI)
done

lemma one_step_implies_mult:
"trans r ==> J \<noteq> {#} ==> \<forall>k \<in> set_of K. \<exists>j \<in> set_of J. (k, j) \<in> r
==> (I + K, I + J) \<in> mult r"
using one_step_implies_mult_aux by blast

subsubsection {* Partial-order properties *}

definition less_multiset :: "'a\<Colon>order multiset \<Rightarrow> 'a multiset \<Rightarrow> bool" (infix "<#" 50) where
"M' <# M \<longleftrightarrow> (M', M) \<in> mult {(x', x). x' < x}"

definition le_multiset :: "'a\<Colon>order multiset \<Rightarrow> 'a multiset \<Rightarrow> bool" (infix "<=#" 50) where
"M' <=# M \<longleftrightarrow> M' <# M \<or> M' = M"

notation (xsymbols) less_multiset (infix "\<subset>#" 50)
notation (xsymbols) le_multiset (infix "\<subseteq>#" 50)

interpretation multiset_order: order le_multiset less_multiset
proof -
have irrefl: "\<And>M :: 'a multiset. \<not> M \<subset># M"
proof
fix M :: "'a multiset"
assume "M \<subset># M"
then have MM: "(M, M) \<in> mult {(x, y). x < y}" by (simp add: less_multiset_def)
have "trans {(x'::'a, x). x' < x}"
by (rule transI) simp
moreover note MM
ultimately have "\<exists>I J K. M = I + J \<and> M = I + K
\<and> J \<noteq> {#} \<and> (\<forall>k\<in>set_of K. \<exists>j\<in>set_of J. (k, j) \<in> {(x, y). x < y})"
by (rule mult_implies_one_step)
then obtain I J K where "M = I + J" and "M = I + K"
and "J \<noteq> {#}" and "(\<forall>k\<in>set_of K. \<exists>j\<in>set_of J. (k, j) \<in> {(x, y). x < y})" by blast
then have aux1: "K \<noteq> {#}" and aux2: "\<forall>k\<in>set_of K. \<exists>j\<in>set_of K. k < j" by auto
have "finite (set_of K)" by simp
moreover note aux2
ultimately have "set_of K = {}"
by (induct rule: finite_induct) (auto intro: order_less_trans)
with aux1 show False by simp
qed
have trans: "\<And>K M N :: 'a multiset. K \<subset># M \<Longrightarrow> M \<subset># N \<Longrightarrow> K \<subset># N"
unfolding less_multiset_def mult_def by (blast intro: trancl_trans)
show "class.order (le_multiset :: 'a multiset \<Rightarrow> _) less_multiset" proof
qed (auto simp add: le_multiset_def irrefl dest: trans)
qed

lemma mult_less_irrefl [elim!]:
"M \<subset># (M::'a::order multiset) ==> R"

subsubsection {* Monotonicity of multiset union *}

lemma mult1_union:
"(B, D) \<in> mult1 r ==> (C + B, C + D) \<in> mult1 r"
apply (unfold mult1_def)
apply auto
apply (rule_tac x = a in exI)
apply (rule_tac x = "C + M0" in exI)
done

lemma union_less_mono2: "B \<subset># D ==> C + B \<subset># C + (D::'a::order multiset)"
apply (unfold less_multiset_def mult_def)
apply (erule trancl_induct)
apply (blast intro: mult1_union)
apply (blast intro: mult1_union trancl_trans)
done

lemma union_less_mono1: "B \<subset># D ==> B + C \<subset># D + (C::'a::order multiset)"
apply (subst add_commute [of B C])
apply (subst add_commute [of D C])
apply (erule union_less_mono2)
done

lemma union_less_mono:
"A \<subset># C ==> B \<subset># D ==> A + B \<subset># C + (D::'a::order multiset)"
by (blast intro!: union_less_mono1 union_less_mono2 multiset_order.less_trans)

interpretation multiset_order: ordered_ab_semigroup_add plus le_multiset less_multiset
proof
qed (auto simp add: le_multiset_def intro: union_less_mono2)

subsection {* The fold combinator *}

text {*
The intended behaviour is
@{text "fold_mset f z {#x\<^isub>1, ..., x\<^isub>n#} = f x\<^isub>1 (\<dots> (f x\<^isub>n z)\<dots>)"}
if @{text f} is associative-commutative.
*}

text {*
The graph of @{text "fold_mset"}, @{text "z"}: the start element,
@{text "f"}: folding function, @{text "A"}: the multiset, @{text
"y"}: the result.
*}
inductive
fold_msetG :: "('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a multiset \<Rightarrow> 'b \<Rightarrow> bool"
for f :: "'a \<Rightarrow> 'b \<Rightarrow> 'b"
and z :: 'b
where
emptyI [intro]:  "fold_msetG f z {#} z"
| insertI [intro]: "fold_msetG f z A y \<Longrightarrow> fold_msetG f z (A + {#x#}) (f x y)"

inductive_cases empty_fold_msetGE [elim!]: "fold_msetG f z {#} x"
inductive_cases insert_fold_msetGE: "fold_msetG f z (A + {#}) y"

definition
fold_mset :: "('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a multiset \<Rightarrow> 'b" where
"fold_mset f z A = (THE x. fold_msetG f z A x)"

lemma Diff1_fold_msetG:
"fold_msetG f z (A - {#x#}) y \<Longrightarrow> x \<in># A \<Longrightarrow> fold_msetG f z A (f x y)"
apply (frule_tac x = x in fold_msetG.insertI)
apply auto
done

lemma fold_msetG_nonempty: "\<exists>x. fold_msetG f z A x"
apply (induct A)
apply blast
apply clarsimp
apply (drule_tac x = x in fold_msetG.insertI)
apply auto
done

lemma fold_mset_empty[simp]: "fold_mset f z {#} = z"
unfolding fold_mset_def by blast

context comp_fun_commute
begin

lemma fold_msetG_determ:
"fold_msetG f z A x \<Longrightarrow> fold_msetG f z A y \<Longrightarrow> y = x"
proof (induct arbitrary: x y z rule: full_multiset_induct)
case (less M x\<^isub>1 x\<^isub>2 Z)
have IH: "\<forall>A. A < M \<longrightarrow>
(\<forall>x x' x''. fold_msetG f x'' A x \<longrightarrow> fold_msetG f x'' A x'
\<longrightarrow> x' = x)" by fact
have Mfoldx\<^isub>1: "fold_msetG f Z M x\<^isub>1" and Mfoldx\<^isub>2: "fold_msetG f Z M x\<^isub>2" by fact+
show ?case
proof (rule fold_msetG.cases [OF Mfoldx\<^isub>1])
assume "M = {#}" and "x\<^isub>1 = Z"
then show ?case using Mfoldx\<^isub>2 by auto
next
fix B b u
assume "M = B + {#b#}" and "x\<^isub>1 = f b u" and Bu: "fold_msetG f Z B u"
then have MBb: "M = B + {#b#}" and x\<^isub>1: "x\<^isub>1 = f b u" by auto
show ?case
proof (rule fold_msetG.cases [OF Mfoldx\<^isub>2])
assume "M = {#}" "x\<^isub>2 = Z"
then show ?case using Mfoldx\<^isub>1 by auto
next
fix C c v
assume "M = C + {#c#}" and "x\<^isub>2 = f c v" and Cv: "fold_msetG f Z C v"
then have MCc: "M = C + {#c#}" and x\<^isub>2: "x\<^isub>2 = f c v" by auto
then have CsubM: "C < M" by simp
from MBb have BsubM: "B < M" by simp
show ?case
proof cases
assume "b=c"
then moreover have "B = C" using MBb MCc by auto
ultimately show ?thesis using Bu Cv x\<^isub>1 x\<^isub>2 CsubM IH by auto
next
assume diff: "b \<noteq> c"
let ?D = "B - {#c#}"
have cinB: "c \<in># B" and binC: "b \<in># C" using MBb MCc diff
by (auto intro: insert_noteq_member dest: sym)
have "B - {#c#} < B" using cinB by (rule mset_less_diff_self)
then have DsubM: "?D < M" using BsubM by (blast intro: order_less_trans)
from MBb MCc have "B + {#b#} = C + {#c#}" by blast
then have [simp]: "B + {#b#} - {#c#} = C"
using MBb MCc binC cinB by auto
have B: "B = ?D + {#c#}" and C: "C = ?D + {#b#}"
using MBb MCc diff binC cinB
then obtain d where Dfoldd: "fold_msetG f Z ?D d"
using fold_msetG_nonempty by iprover
then have "fold_msetG f Z B (f c d)" using cinB
by (rule Diff1_fold_msetG)
then have "f c d = u" using IH BsubM Bu by blast
moreover
have "fold_msetG f Z C (f b d)" using binC cinB diff Dfoldd
dest: fold_msetG.insertI [where x=b])
then have "f b d = v" using IH CsubM Cv by blast
ultimately show ?thesis using x\<^isub>1 x\<^isub>2
by (auto simp: fun_left_comm)
qed
qed
qed
qed

lemma fold_mset_insert_aux:
"(fold_msetG f z (A + {#x#}) v) =
(\<exists>y. fold_msetG f z A y \<and> v = f x y)"
apply (rule iffI)
prefer 2
apply blast
apply (rule_tac A1=A and f1=f in fold_msetG_nonempty [THEN exE])
apply (blast intro: fold_msetG_determ)
done

lemma fold_mset_equality: "fold_msetG f z A y \<Longrightarrow> fold_mset f z A = y"
unfolding fold_mset_def by (blast intro: fold_msetG_determ)

lemma fold_mset_insert:
"fold_mset f z (A + {#x#}) = f x (fold_mset f z A)"
apply (rule the_equality)
simp add: fold_mset_def [symmetric] fold_mset_equality fold_msetG_nonempty)
done

lemma fold_mset_commute: "f x (fold_mset f z A) = fold_mset f (f x z) A"
by (induct A) (auto simp: fold_mset_insert fun_left_comm [of x])

lemma fold_mset_single [simp]: "fold_mset f z {#x#} = f x z"
using fold_mset_insert [of z "{#}"] by simp

lemma fold_mset_union [simp]:
"fold_mset f z (A+B) = fold_mset f (fold_mset f z A) B"
proof (induct A)
case empty then show ?case by simp
next
have "A + {#x#} + B = (A+B) + {#x#}" by (simp add: add_ac)
then have "fold_mset f z (A + {#x#} + B) = f x (fold_mset f z (A + B))"
also have "\<dots> = fold_mset f (fold_mset f z (A + {#x#})) B"
finally show ?case .
qed

lemma fold_mset_fusion:
assumes "comp_fun_commute g"
shows "(\<And>x y. h (g x y) = f x (h y)) \<Longrightarrow> h (fold_mset g w A) = fold_mset f (h w) A" (is "PROP ?P")
proof -
interpret comp_fun_commute g by (fact assms)
show "PROP ?P" by (induct A) auto
qed

lemma fold_mset_rec:
assumes "a \<in># A"
shows "fold_mset f z A = f a (fold_mset f z (A - {#a#}))"
proof -
from assms obtain A' where "A = A' + {#a#}"
by (blast dest: multi_member_split)
then show ?thesis by simp
qed

end

text {*
A note on code generation: When defining some function containing a
subterm @{term"fold_mset F"}, code generation is not automatic. When
interpreting locale @{text left_commutative} with @{text F}, the
would be code thms for @{const fold_mset} become thms like
@{term"fold_mset F z {#} = z"} where @{text F} is not a pattern but
contains defined symbols, i.e.\ is not a code thm. Hence a separate
constant with its own code thms needs to be introduced for @{text
F}. See the image operator below.
*}

subsection {* Image *}

definition image_mset :: "('a \<Rightarrow> 'b) \<Rightarrow> 'a multiset \<Rightarrow> 'b multiset" where
"image_mset f = fold_mset (op + o single o f) {#}"

interpretation image_fun_commute: comp_fun_commute "op + o single o f" for f

lemma image_mset_empty [simp]: "image_mset f {#} = {#}"

lemma image_mset_single [simp]: "image_mset f {#x#} = {#f x#}"

lemma image_mset_insert:
"image_mset f (M + {#a#}) = image_mset f M + {#f a#}"

lemma image_mset_union [simp]:
"image_mset f (M+N) = image_mset f M + image_mset f N"
apply (induct N)
apply simp
done

lemma size_image_mset [simp]: "size (image_mset f M) = size M"
by (induct M) simp_all

lemma image_mset_is_empty_iff [simp]: "image_mset f M = {#} \<longleftrightarrow> M = {#}"
by (cases M) auto

syntax
"_comprehension1_mset" :: "'a \<Rightarrow> 'b \<Rightarrow> 'b multiset \<Rightarrow> 'a multiset"
("({#_/. _ :# _#})")
translations
"{#e. x:#M#}" == "CONST image_mset (%x. e) M"

syntax
"_comprehension2_mset" :: "'a \<Rightarrow> 'b \<Rightarrow> 'b multiset \<Rightarrow> bool \<Rightarrow> 'a multiset"
("({#_/ | _ :# _./ _#})")
translations
"{#e | x:#M. P#}" => "{#e. x :# {# x:#M. P#}#}"

text {*
This allows to write not just filters like @{term "{#x:#M. x<c#}"}
but also images like @{term "{#x+x. x:#M #}"} and @{term [source]
"{#x+x|x:#M. x<c#}"}, where the latter is currently displayed as
@{term "{#x+x|x:#M. x<c#}"}.
*}

enriched_type image_mset: image_mset proof -
fix f g
show "image_mset f \<circ> image_mset g = image_mset (f \<circ> g)"
proof
fix A
show "(image_mset f \<circ> image_mset g) A = image_mset (f \<circ> g) A"
by (induct A) simp_all
qed
next
show "image_mset id = id"
proof
fix A
show "image_mset id A = id A"
by (induct A) simp_all
qed
qed

subsection {* Termination proofs with multiset orders *}

lemma multi_member_skip: "x \<in># XS \<Longrightarrow> x \<in># {# y #} + XS"
and multi_member_this: "x \<in># {# x #} + XS"
and multi_member_last: "x \<in># {# x #}"
by auto

definition "ms_strict = mult pair_less"
definition "ms_weak = ms_strict \<union> Id"

lemma ms_reduction_pair: "reduction_pair (ms_strict, ms_weak)"
unfolding reduction_pair_def ms_strict_def ms_weak_def pair_less_def
by (auto intro: wf_mult1 wf_trancl simp: mult_def)

lemma smsI:
"(set_of A, set_of B) \<in> max_strict \<Longrightarrow> (Z + A, Z + B) \<in> ms_strict"
unfolding ms_strict_def
by (rule one_step_implies_mult) (auto simp add: max_strict_def pair_less_def elim!:max_ext.cases)

lemma wmsI:
"(set_of A, set_of B) \<in> max_strict \<or> A = {#} \<and> B = {#}
\<Longrightarrow> (Z + A, Z + B) \<in> ms_weak"
unfolding ms_weak_def ms_strict_def
by (auto simp add: pair_less_def max_strict_def elim!:max_ext.cases intro: one_step_implies_mult)

inductive pw_leq
where
pw_leq_empty: "pw_leq {#} {#}"
| pw_leq_step:  "\<lbrakk>(x,y) \<in> pair_leq; pw_leq X Y \<rbrakk> \<Longrightarrow> pw_leq ({#x#} + X) ({#y#} + Y)"

lemma pw_leq_lstep:
"(x, y) \<in> pair_leq \<Longrightarrow> pw_leq {#x#} {#y#}"
by (drule pw_leq_step) (rule pw_leq_empty, simp)

lemma pw_leq_split:
assumes "pw_leq X Y"
shows "\<exists>A B Z. X = A + Z \<and> Y = B + Z \<and> ((set_of A, set_of B) \<in> max_strict \<or> (B = {#} \<and> A = {#}))"
using assms
proof (induct)
case pw_leq_empty thus ?case by auto
next
case (pw_leq_step x y X Y)
then obtain A B Z where
[simp]: "X = A + Z" "Y = B + Z"
and 1[simp]: "(set_of A, set_of B) \<in> max_strict \<or> (B = {#} \<and> A = {#})"
by auto
from pw_leq_step have "x = y \<or> (x, y) \<in> pair_less"
unfolding pair_leq_def by auto
thus ?case
proof
assume [simp]: "x = y"
have
"{#x#} + X = A + ({#y#}+Z)
\<and> {#y#} + Y = B + ({#y#}+Z)
\<and> ((set_of A, set_of B) \<in> max_strict \<or> (B = {#} \<and> A = {#}))"
thus ?case by (intro exI)
next
assume A: "(x, y) \<in> pair_less"
let ?A' = "{#x#} + A" and ?B' = "{#y#} + B"
have "{#x#} + X = ?A' + Z"
"{#y#} + Y = ?B' + Z"
moreover have
"(set_of ?A', set_of ?B') \<in> max_strict"
using 1 A unfolding max_strict_def
by (auto elim!: max_ext.cases)
ultimately show ?thesis by blast
qed
qed

lemma
assumes pwleq: "pw_leq Z Z'"
shows ms_strictI: "(set_of A, set_of B) \<in> max_strict \<Longrightarrow> (Z + A, Z' + B) \<in> ms_strict"
and   ms_weakI1:  "(set_of A, set_of B) \<in> max_strict \<Longrightarrow> (Z + A, Z' + B) \<in> ms_weak"
and   ms_weakI2:  "(Z + {#}, Z' + {#}) \<in> ms_weak"
proof -
from pw_leq_split[OF pwleq]
obtain A' B' Z''
where [simp]: "Z = A' + Z''" "Z' = B' + Z''"
and mx_or_empty: "(set_of A', set_of B') \<in> max_strict \<or> (A' = {#} \<and> B' = {#})"
by blast
{
assume max: "(set_of A, set_of B) \<in> max_strict"
from mx_or_empty
have "(Z'' + (A + A'), Z'' + (B + B')) \<in> ms_strict"
proof
assume max': "(set_of A', set_of B') \<in> max_strict"
with max have "(set_of (A + A'), set_of (B + B')) \<in> max_strict"
by (auto simp: max_strict_def intro: max_ext_additive)
thus ?thesis by (rule smsI)
next
assume [simp]: "A' = {#} \<and> B' = {#}"
show ?thesis by (rule smsI) (auto intro: max)
qed
thus "(Z + A, Z' + B) \<in> ms_strict" by (simp add:add_ac)
thus "(Z + A, Z' + B) \<in> ms_weak" by (simp add: ms_weak_def)
}
from mx_or_empty
have "(Z'' + A', Z'' + B') \<in> ms_weak" by (rule wmsI)
thus "(Z + {#}, Z' + {#}) \<in> ms_weak" by (simp add:add_ac)
qed

lemma empty_neutral: "{#} + x = x" "x + {#} = x"
and nonempty_plus: "{# x #} + rs \<noteq> {#}"
and nonempty_single: "{# x #} \<noteq> {#}"
by auto

setup {*
let
fun msetT T = Type (@{type_name multiset}, [T]);

fun mk_mset T [] = Const (@{const_abbrev Mempty}, msetT T)
| mk_mset T [x] = Const (@{const_name single}, T --> msetT T) \$ x
| mk_mset T (x :: xs) =
Const (@{const_name plus}, msetT T --> msetT T --> msetT T) \$
mk_mset T [x] \$ mk_mset T xs

fun mset_member_tac m i =
(if m <= 0 then
rtac @{thm multi_member_this} i ORELSE rtac @{thm multi_member_last} i
else
rtac @{thm multi_member_skip} i THEN mset_member_tac (m - 1) i)

val mset_nonempty_tac =
rtac @{thm nonempty_plus} ORELSE' rtac @{thm nonempty_single}

val regroup_munion_conv =
Function_Lib.regroup_conv @{const_abbrev Mempty} @{const_name plus}
(map (fn t => t RS eq_reflection) (@{thms add_ac} @ @{thms empty_neutral}))

fun unfold_pwleq_tac i =
(rtac @{thm pw_leq_step} i THEN (fn st => unfold_pwleq_tac (i + 1) st))
ORELSE (rtac @{thm pw_leq_lstep} i)
ORELSE (rtac @{thm pw_leq_empty} i)

val set_of_simps = [@{thm set_of_empty}, @{thm set_of_single}, @{thm set_of_union},
@{thm Un_insert_left}, @{thm Un_empty_left}]
in
ScnpReconstruct.multiset_setup (ScnpReconstruct.Multiset
{
msetT=msetT, mk_mset=mk_mset, mset_regroup_conv=regroup_munion_conv,
mset_member_tac=mset_member_tac, mset_nonempty_tac=mset_nonempty_tac,
mset_pwleq_tac=unfold_pwleq_tac, set_of_simps=set_of_simps,
smsI'= @{thm ms_strictI}, wmsI2''= @{thm ms_weakI2}, wmsI1= @{thm ms_weakI1},
reduction_pair= @{thm ms_reduction_pair}
})
end
*}

subsection {* Legacy theorem bindings *}

lemmas multi_count_eq = multiset_eq_iff [symmetric]

lemma union_commute: "M + N = N + (M::'a multiset)"

lemma union_assoc: "(M + N) + K = M + (N + (K::'a multiset))"

lemma union_lcomm: "M + (N + K) = N + (M + (K::'a multiset))"

lemmas union_ac = union_assoc union_commute union_lcomm

lemma union_right_cancel: "M + K = N + K \<longleftrightarrow> M = (N::'a multiset)"

lemma union_left_cancel: "K + M = K + N \<longleftrightarrow> M = (N::'a multiset)"

lemma multi_union_self_other_eq: "(A::'a multiset) + X = A + Y \<Longrightarrow> X = Y"

lemma mset_less_trans: "(M::'a multiset) < K \<Longrightarrow> K < N \<Longrightarrow> M < N"
by (fact order_less_trans)

lemma multiset_inter_commute: "A #\<inter> B = B #\<inter> A"
by (fact inf.commute)

lemma multiset_inter_assoc: "A #\<inter> (B #\<inter> C) = A #\<inter> B #\<inter> C"
by (fact inf.assoc [symmetric])

lemma multiset_inter_left_commute: "A #\<inter> (B #\<inter> C) = B #\<inter> (A #\<inter> C)"
by (fact inf.left_commute)

lemmas multiset_inter_ac =
multiset_inter_commute
multiset_inter_assoc
multiset_inter_left_commute

lemma mult_less_not_refl:
"\<not> M \<subset># (M::'a::order multiset)"
by (fact multiset_order.less_irrefl)

lemma mult_less_trans:
"K \<subset># M ==> M \<subset># N ==> K \<subset># (N::'a::order multiset)"
by (fact multiset_order.less_trans)

lemma mult_less_not_sym:
"M \<subset># N ==> \<not> N \<subset># (M::'a::order multiset)"
by (fact multiset_order.less_not_sym)

lemma mult_less_asym:
"M \<subset># N ==> (\<not> P ==> N \<subset># (M::'a::order multiset)) ==> P"
by (fact multiset_order.less_asym)

ML {*
fun multiset_postproc _ maybe_name all_values (T as Type (_, [elem_T]))
(Const _ \$ t') =
let
val (maybe_opt, ps) =
Nitpick_Model.dest_plain_fun t' ||> op ~~
||> map (apsnd (snd o HOLogic.dest_number))
fun elems_for t =
case AList.lookup (op =) ps t of
SOME n => replicate n t
| NONE => [Const (maybe_name, elem_T --> elem_T) \$ t]
in
case maps elems_for (all_values elem_T) @
(if maybe_opt then [Const (Nitpick_Model.unrep (), elem_T)]
else []) of
[] => Const (@{const_name zero_class.zero}, T)
| ts => foldl1 (fn (t1, t2) =>
Const (@{const_name plus_class.plus}, T --> T --> T)
\$ t1 \$ t2)
(map (curry (op \$) (Const (@{const_name single},
elem_T --> T))) ts)
end
| multiset_postproc _ _ _ _ t = t
*}

declaration {*
Nitpick_Model.register_term_postprocessor @{typ "'a multiset"}
multiset_postproc
*}

end
```