src/HOL/Library/Multiset.thy
 author wenzelm Mon Dec 28 01:28:28 2015 +0100 (2015-12-28) changeset 61945 1135b8de26c3 parent 61890 f6ded81f5690 child 61955 e96292f32c3c permissions -rw-r--r--
more symbols;
```     1 (*  Title:      HOL/Library/Multiset.thy
```
```     2     Author:     Tobias Nipkow, Markus Wenzel, Lawrence C Paulson, Norbert Voelker
```
```     3     Author:     Andrei Popescu, TU Muenchen
```
```     4     Author:     Jasmin Blanchette, Inria, LORIA, MPII
```
```     5     Author:     Dmitriy Traytel, TU Muenchen
```
```     6     Author:     Mathias Fleury, MPII
```
```     7 *)
```
```     8
```
```     9 section \<open>(Finite) multisets\<close>
```
```    10
```
```    11 theory Multiset
```
```    12 imports Main
```
```    13 begin
```
```    14
```
```    15 subsection \<open>The type of multisets\<close>
```
```    16
```
```    17 definition "multiset = {f :: 'a \<Rightarrow> nat. finite {x. f x > 0}}"
```
```    18
```
```    19 typedef 'a multiset = "multiset :: ('a \<Rightarrow> nat) set"
```
```    20   morphisms count Abs_multiset
```
```    21   unfolding multiset_def
```
```    22 proof
```
```    23   show "(\<lambda>x. 0::nat) \<in> {f. finite {x. f x > 0}}" by simp
```
```    24 qed
```
```    25
```
```    26 setup_lifting type_definition_multiset
```
```    27
```
```    28 abbreviation Melem :: "'a \<Rightarrow> 'a multiset \<Rightarrow> bool"  ("(_/ :# _)" [50, 51] 50) where
```
```    29   "a :# M == 0 < count M a"
```
```    30
```
```    31 notation (xsymbols)
```
```    32   Melem (infix "\<in>#" 50)
```
```    33
```
```    34 lemma multiset_eq_iff: "M = N \<longleftrightarrow> (\<forall>a. count M a = count N a)"
```
```    35   by (simp only: count_inject [symmetric] fun_eq_iff)
```
```    36
```
```    37 lemma multiset_eqI: "(\<And>x. count A x = count B x) \<Longrightarrow> A = B"
```
```    38   using multiset_eq_iff by auto
```
```    39
```
```    40 text \<open>Preservation of the representing set @{term multiset}.\<close>
```
```    41
```
```    42 lemma const0_in_multiset: "(\<lambda>a. 0) \<in> multiset"
```
```    43   by (simp add: multiset_def)
```
```    44
```
```    45 lemma only1_in_multiset: "(\<lambda>b. if b = a then n else 0) \<in> multiset"
```
```    46   by (simp add: multiset_def)
```
```    47
```
```    48 lemma union_preserves_multiset: "M \<in> multiset \<Longrightarrow> N \<in> multiset \<Longrightarrow> (\<lambda>a. M a + N a) \<in> multiset"
```
```    49   by (simp add: multiset_def)
```
```    50
```
```    51 lemma diff_preserves_multiset:
```
```    52   assumes "M \<in> multiset"
```
```    53   shows "(\<lambda>a. M a - N a) \<in> multiset"
```
```    54 proof -
```
```    55   have "{x. N x < M x} \<subseteq> {x. 0 < M x}"
```
```    56     by auto
```
```    57   with assms show ?thesis
```
```    58     by (auto simp add: multiset_def intro: finite_subset)
```
```    59 qed
```
```    60
```
```    61 lemma filter_preserves_multiset:
```
```    62   assumes "M \<in> multiset"
```
```    63   shows "(\<lambda>x. if P x then M x else 0) \<in> multiset"
```
```    64 proof -
```
```    65   have "{x. (P x \<longrightarrow> 0 < M x) \<and> P x} \<subseteq> {x. 0 < M x}"
```
```    66     by auto
```
```    67   with assms show ?thesis
```
```    68     by (auto simp add: multiset_def intro: finite_subset)
```
```    69 qed
```
```    70
```
```    71 lemmas in_multiset = const0_in_multiset only1_in_multiset
```
```    72   union_preserves_multiset diff_preserves_multiset filter_preserves_multiset
```
```    73
```
```    74
```
```    75 subsection \<open>Representing multisets\<close>
```
```    76
```
```    77 text \<open>Multiset enumeration\<close>
```
```    78
```
```    79 instantiation multiset :: (type) cancel_comm_monoid_add
```
```    80 begin
```
```    81
```
```    82 lift_definition zero_multiset :: "'a multiset" is "\<lambda>a. 0"
```
```    83 by (rule const0_in_multiset)
```
```    84
```
```    85 abbreviation Mempty :: "'a multiset" ("{#}") where
```
```    86   "Mempty \<equiv> 0"
```
```    87
```
```    88 lift_definition plus_multiset :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> 'a multiset" is "\<lambda>M N. (\<lambda>a. M a + N a)"
```
```    89 by (rule union_preserves_multiset)
```
```    90
```
```    91 lift_definition minus_multiset :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> 'a multiset" is "\<lambda> M N. \<lambda>a. M a - N a"
```
```    92 by (rule diff_preserves_multiset)
```
```    93
```
```    94 instance
```
```    95   by (standard; transfer; simp add: fun_eq_iff)
```
```    96
```
```    97 end
```
```    98
```
```    99 lift_definition single :: "'a \<Rightarrow> 'a multiset" is "\<lambda>a b. if b = a then 1 else 0"
```
```   100 by (rule only1_in_multiset)
```
```   101
```
```   102 syntax
```
```   103   "_multiset" :: "args \<Rightarrow> 'a multiset"    ("{#(_)#}")
```
```   104 translations
```
```   105   "{#x, xs#}" == "{#x#} + {#xs#}"
```
```   106   "{#x#}" == "CONST single x"
```
```   107
```
```   108 lemma count_empty [simp]: "count {#} a = 0"
```
```   109   by (simp add: zero_multiset.rep_eq)
```
```   110
```
```   111 lemma count_single [simp]: "count {#b#} a = (if b = a then 1 else 0)"
```
```   112   by (simp add: single.rep_eq)
```
```   113
```
```   114
```
```   115 subsection \<open>Basic operations\<close>
```
```   116
```
```   117 subsubsection \<open>Union\<close>
```
```   118
```
```   119 lemma count_union [simp]: "count (M + N) a = count M a + count N a"
```
```   120   by (simp add: plus_multiset.rep_eq)
```
```   121
```
```   122
```
```   123 subsubsection \<open>Difference\<close>
```
```   124
```
```   125 instantiation multiset :: (type) comm_monoid_diff
```
```   126 begin
```
```   127
```
```   128 instance
```
```   129   by (standard; transfer; simp add: fun_eq_iff)
```
```   130
```
```   131 end
```
```   132
```
```   133 lemma count_diff [simp]: "count (M - N) a = count M a - count N a"
```
```   134   by (simp add: minus_multiset.rep_eq)
```
```   135
```
```   136 lemma diff_empty [simp]: "M - {#} = M \<and> {#} - M = {#}"
```
```   137   by rule (fact Groups.diff_zero, fact Groups.zero_diff)
```
```   138
```
```   139 lemma diff_cancel[simp]: "A - A = {#}"
```
```   140   by (fact Groups.diff_cancel)
```
```   141
```
```   142 lemma diff_union_cancelR [simp]: "M + N - N = (M::'a multiset)"
```
```   143   by (fact add_diff_cancel_right')
```
```   144
```
```   145 lemma diff_union_cancelL [simp]: "N + M - N = (M::'a multiset)"
```
```   146   by (fact add_diff_cancel_left')
```
```   147
```
```   148 lemma diff_right_commute:
```
```   149   fixes M N Q :: "'a multiset"
```
```   150   shows "M - N - Q = M - Q - N"
```
```   151   by (fact diff_right_commute)
```
```   152
```
```   153 lemma diff_add:
```
```   154   fixes M N Q :: "'a multiset"
```
```   155   shows "M - (N + Q) = M - N - Q"
```
```   156   by (rule sym) (fact diff_diff_add)
```
```   157
```
```   158 lemma insert_DiffM: "x \<in># M \<Longrightarrow> {#x#} + (M - {#x#}) = M"
```
```   159   by (clarsimp simp: multiset_eq_iff)
```
```   160
```
```   161 lemma insert_DiffM2 [simp]: "x \<in># M \<Longrightarrow> M - {#x#} + {#x#} = M"
```
```   162   by (clarsimp simp: multiset_eq_iff)
```
```   163
```
```   164 lemma diff_union_swap: "a \<noteq> b \<Longrightarrow> M - {#a#} + {#b#} = M + {#b#} - {#a#}"
```
```   165   by (auto simp add: multiset_eq_iff)
```
```   166
```
```   167 lemma diff_union_single_conv: "a \<in># J \<Longrightarrow> I + J - {#a#} = I + (J - {#a#})"
```
```   168   by (simp add: multiset_eq_iff)
```
```   169
```
```   170
```
```   171 subsubsection \<open>Equality of multisets\<close>
```
```   172
```
```   173 lemma single_not_empty [simp]: "{#a#} \<noteq> {#} \<and> {#} \<noteq> {#a#}"
```
```   174   by (simp add: multiset_eq_iff)
```
```   175
```
```   176 lemma single_eq_single [simp]: "{#a#} = {#b#} \<longleftrightarrow> a = b"
```
```   177   by (auto simp add: multiset_eq_iff)
```
```   178
```
```   179 lemma union_eq_empty [iff]: "M + N = {#} \<longleftrightarrow> M = {#} \<and> N = {#}"
```
```   180   by (auto simp add: multiset_eq_iff)
```
```   181
```
```   182 lemma empty_eq_union [iff]: "{#} = M + N \<longleftrightarrow> M = {#} \<and> N = {#}"
```
```   183   by (auto simp add: multiset_eq_iff)
```
```   184
```
```   185 lemma multi_self_add_other_not_self [simp]: "M = M + {#x#} \<longleftrightarrow> False"
```
```   186   by (auto simp add: multiset_eq_iff)
```
```   187
```
```   188 lemma diff_single_trivial: "\<not> x \<in># M \<Longrightarrow> M - {#x#} = M"
```
```   189   by (auto simp add: multiset_eq_iff)
```
```   190
```
```   191 lemma diff_single_eq_union: "x \<in># M \<Longrightarrow> M - {#x#} = N \<longleftrightarrow> M = N + {#x#}"
```
```   192   by auto
```
```   193
```
```   194 lemma union_single_eq_diff: "M + {#x#} = N \<Longrightarrow> M = N - {#x#}"
```
```   195   by (auto dest: sym)
```
```   196
```
```   197 lemma union_single_eq_member: "M + {#x#} = N \<Longrightarrow> x \<in># N"
```
```   198   by auto
```
```   199
```
```   200 lemma union_is_single: "M + N = {#a#} \<longleftrightarrow> M = {#a#} \<and> N={#} \<or> M = {#} \<and> N = {#a#}"
```
```   201   (is "?lhs = ?rhs")
```
```   202 proof
```
```   203   show ?lhs if ?rhs using that by auto
```
```   204   show ?rhs if ?lhs
```
```   205     using that by (simp add: multiset_eq_iff split: if_splits) (metis add_is_1)
```
```   206 qed
```
```   207
```
```   208 lemma single_is_union: "{#a#} = M + N \<longleftrightarrow> {#a#} = M \<and> N = {#} \<or> M = {#} \<and> {#a#} = N"
```
```   209   by (auto simp add: eq_commute [of "{#a#}" "M + N"] union_is_single)
```
```   210
```
```   211 lemma add_eq_conv_diff:
```
```   212   "M + {#a#} = N + {#b#} \<longleftrightarrow> M = N \<and> a = b \<or> M = N - {#a#} + {#b#} \<and> N = M - {#b#} + {#a#}"
```
```   213   (is "?lhs \<longleftrightarrow> ?rhs")
```
```   214 (* shorter: by (simp add: multiset_eq_iff) fastforce *)
```
```   215 proof
```
```   216   show ?lhs if ?rhs
```
```   217     using that
```
```   218     by (auto simp add: add.assoc add.commute [of "{#b#}"])
```
```   219       (drule sym, simp add: add.assoc [symmetric])
```
```   220   show ?rhs if ?lhs
```
```   221   proof (cases "a = b")
```
```   222     case True with \<open>?lhs\<close> show ?thesis by simp
```
```   223   next
```
```   224     case False
```
```   225     from \<open>?lhs\<close> have "a \<in># N + {#b#}" by (rule union_single_eq_member)
```
```   226     with False have "a \<in># N" by auto
```
```   227     moreover from \<open>?lhs\<close> have "M = N + {#b#} - {#a#}" by (rule union_single_eq_diff)
```
```   228     moreover note False
```
```   229     ultimately show ?thesis by (auto simp add: diff_right_commute [of _ "{#a#}"] diff_union_swap)
```
```   230   qed
```
```   231 qed
```
```   232
```
```   233 lemma insert_noteq_member:
```
```   234   assumes BC: "B + {#b#} = C + {#c#}"
```
```   235    and bnotc: "b \<noteq> c"
```
```   236   shows "c \<in># B"
```
```   237 proof -
```
```   238   have "c \<in># C + {#c#}" by simp
```
```   239   have nc: "\<not> c \<in># {#b#}" using bnotc by simp
```
```   240   then have "c \<in># B + {#b#}" using BC by simp
```
```   241   then show "c \<in># B" using nc by simp
```
```   242 qed
```
```   243
```
```   244 lemma add_eq_conv_ex:
```
```   245   "(M + {#a#} = N + {#b#}) =
```
```   246     (M = N \<and> a = b \<or> (\<exists>K. M = K + {#b#} \<and> N = K + {#a#}))"
```
```   247   by (auto simp add: add_eq_conv_diff)
```
```   248
```
```   249 lemma multi_member_split: "x \<in># M \<Longrightarrow> \<exists>A. M = A + {#x#}"
```
```   250   by (rule exI [where x = "M - {#x#}"]) simp
```
```   251
```
```   252 lemma multiset_add_sub_el_shuffle:
```
```   253   assumes "c \<in># B"
```
```   254     and "b \<noteq> c"
```
```   255   shows "B - {#c#} + {#b#} = B + {#b#} - {#c#}"
```
```   256 proof -
```
```   257   from \<open>c \<in># B\<close> obtain A where B: "B = A + {#c#}"
```
```   258     by (blast dest: multi_member_split)
```
```   259   have "A + {#b#} = A + {#b#} + {#c#} - {#c#}" by simp
```
```   260   then have "A + {#b#} = A + {#c#} + {#b#} - {#c#}"
```
```   261     by (simp add: ac_simps)
```
```   262   then show ?thesis using B by simp
```
```   263 qed
```
```   264
```
```   265
```
```   266 subsubsection \<open>Pointwise ordering induced by count\<close>
```
```   267
```
```   268 definition subseteq_mset :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> bool" (infix "<=#" 50) where
```
```   269 "subseteq_mset A B = (\<forall>a. count A a \<le> count B a)"
```
```   270
```
```   271 definition subset_mset :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> bool" (infix "<#" 50) where
```
```   272 "subset_mset A B = (A <=# B \<and> A \<noteq> B)"
```
```   273
```
```   274 notation subseteq_mset (infix "\<le>#" 50)
```
```   275 notation (xsymbols) subseteq_mset (infix "\<subseteq>#" 50)
```
```   276
```
```   277 notation (xsymbols) subset_mset (infix "\<subset>#" 50)
```
```   278
```
```   279 interpretation subset_mset: ordered_ab_semigroup_add_imp_le "op +" "op -" "op \<subseteq>#" "op \<subset>#"
```
```   280   by standard (auto simp add: subset_mset_def subseteq_mset_def multiset_eq_iff intro: order_trans antisym)
```
```   281
```
```   282 lemma mset_less_eqI: "(\<And>x. count A x \<le> count B x) \<Longrightarrow> A \<le># B"
```
```   283   by (simp add: subseteq_mset_def)
```
```   284
```
```   285 lemma mset_le_exists_conv: "(A::'a multiset) \<le># B \<longleftrightarrow> (\<exists>C. B = A + C)"
```
```   286   unfolding subseteq_mset_def
```
```   287   apply (rule iffI)
```
```   288    apply (rule exI [where x = "B - A"])
```
```   289    apply (auto intro: multiset_eq_iff [THEN iffD2])
```
```   290   done
```
```   291
```
```   292 interpretation subset_mset: ordered_cancel_comm_monoid_diff  "op +" "op -" 0 "op \<le>#" "op <#"
```
```   293   by standard (simp, fact mset_le_exists_conv)
```
```   294
```
```   295 lemma mset_le_mono_add_right_cancel [simp]: "(A::'a multiset) + C \<le># B + C \<longleftrightarrow> A \<le># B"
```
```   296   by (fact subset_mset.add_le_cancel_right)
```
```   297
```
```   298 lemma mset_le_mono_add_left_cancel [simp]: "C + (A::'a multiset) \<le># C + B \<longleftrightarrow> A \<le># B"
```
```   299   by (fact subset_mset.add_le_cancel_left)
```
```   300
```
```   301 lemma mset_le_mono_add: "(A::'a multiset) \<le># B \<Longrightarrow> C \<le># D \<Longrightarrow> A + C \<le># B + D"
```
```   302   by (fact subset_mset.add_mono)
```
```   303
```
```   304 lemma mset_le_add_left [simp]: "(A::'a multiset) \<le># A + B"
```
```   305   unfolding subseteq_mset_def by auto
```
```   306
```
```   307 lemma mset_le_add_right [simp]: "B \<le># (A::'a multiset) + B"
```
```   308   unfolding subseteq_mset_def by auto
```
```   309
```
```   310 lemma mset_le_single: "a \<in># B \<Longrightarrow> {#a#} \<le># B"
```
```   311   by (simp add: subseteq_mset_def)
```
```   312
```
```   313 lemma multiset_diff_union_assoc:
```
```   314   fixes A B C D :: "'a multiset"
```
```   315   shows "C \<le># B \<Longrightarrow> A + B - C = A + (B - C)"
```
```   316   by (simp add: subset_mset.diff_add_assoc)
```
```   317
```
```   318 lemma mset_le_multiset_union_diff_commute:
```
```   319   fixes A B C D :: "'a multiset"
```
```   320   shows "B \<le># A \<Longrightarrow> A - B + C = A + C - B"
```
```   321 by (simp add: subset_mset.add_diff_assoc2)
```
```   322
```
```   323 lemma diff_le_self[simp]: "(M::'a multiset) - N \<le># M"
```
```   324 by(simp add: subseteq_mset_def)
```
```   325
```
```   326 lemma mset_lessD: "A <# B \<Longrightarrow> x \<in># A \<Longrightarrow> x \<in># B"
```
```   327 apply (clarsimp simp: subset_mset_def subseteq_mset_def)
```
```   328 apply (erule allE [where x = x])
```
```   329 apply auto
```
```   330 done
```
```   331
```
```   332 lemma mset_leD: "A \<le># B \<Longrightarrow> x \<in># A \<Longrightarrow> x \<in># B"
```
```   333 apply (clarsimp simp: subset_mset_def subseteq_mset_def)
```
```   334 apply (erule allE [where x = x])
```
```   335 apply auto
```
```   336 done
```
```   337
```
```   338 lemma mset_less_insertD: "(A + {#x#} <# B) \<Longrightarrow> (x \<in># B \<and> A <# B)"
```
```   339 apply (rule conjI)
```
```   340  apply (simp add: mset_lessD)
```
```   341 apply (clarsimp simp: subset_mset_def subseteq_mset_def)
```
```   342 apply safe
```
```   343  apply (erule_tac x = a in allE)
```
```   344  apply (auto split: split_if_asm)
```
```   345 done
```
```   346
```
```   347 lemma mset_le_insertD: "(A + {#x#} \<le># B) \<Longrightarrow> (x \<in># B \<and> A \<le># B)"
```
```   348 apply (rule conjI)
```
```   349  apply (simp add: mset_leD)
```
```   350 apply (force simp: subset_mset_def subseteq_mset_def split: split_if_asm)
```
```   351 done
```
```   352
```
```   353 lemma mset_less_of_empty[simp]: "A <# {#} \<longleftrightarrow> False"
```
```   354   by (auto simp add: subseteq_mset_def subset_mset_def multiset_eq_iff)
```
```   355
```
```   356 lemma empty_le[simp]: "{#} \<le># A"
```
```   357   unfolding mset_le_exists_conv by auto
```
```   358
```
```   359 lemma le_empty[simp]: "(M \<le># {#}) = (M = {#})"
```
```   360   unfolding mset_le_exists_conv by auto
```
```   361
```
```   362 lemma multi_psub_of_add_self[simp]: "A <# A + {#x#}"
```
```   363   by (auto simp: subset_mset_def subseteq_mset_def)
```
```   364
```
```   365 lemma multi_psub_self[simp]: "(A::'a multiset) <# A = False"
```
```   366   by simp
```
```   367
```
```   368 lemma mset_less_add_bothsides: "N + {#x#} <# M + {#x#} \<Longrightarrow> N <# M"
```
```   369   by (fact subset_mset.add_less_imp_less_right)
```
```   370
```
```   371 lemma mset_less_empty_nonempty: "{#} <# S \<longleftrightarrow> S \<noteq> {#}"
```
```   372   by (auto simp: subset_mset_def subseteq_mset_def)
```
```   373
```
```   374 lemma mset_less_diff_self: "c \<in># B \<Longrightarrow> B - {#c#} <# B"
```
```   375   by (auto simp: subset_mset_def subseteq_mset_def multiset_eq_iff)
```
```   376
```
```   377
```
```   378 subsubsection \<open>Intersection\<close>
```
```   379
```
```   380 definition inf_subset_mset :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> 'a multiset" (infixl "#\<inter>" 70) where
```
```   381   multiset_inter_def: "inf_subset_mset A B = A - (A - B)"
```
```   382
```
```   383 interpretation subset_mset: semilattice_inf inf_subset_mset "op \<le>#" "op <#"
```
```   384 proof -
```
```   385   have [simp]: "m \<le> n \<Longrightarrow> m \<le> q \<Longrightarrow> m \<le> n - (n - q)" for m n q :: nat
```
```   386     by arith
```
```   387   show "class.semilattice_inf op #\<inter> op \<le># op <#"
```
```   388     by standard (auto simp add: multiset_inter_def subseteq_mset_def)
```
```   389 qed
```
```   390
```
```   391
```
```   392 lemma multiset_inter_count [simp]:
```
```   393   fixes A B :: "'a multiset"
```
```   394   shows "count (A #\<inter> B) x = min (count A x) (count B x)"
```
```   395   by (simp add: multiset_inter_def)
```
```   396
```
```   397 lemma multiset_inter_single: "a \<noteq> b \<Longrightarrow> {#a#} #\<inter> {#b#} = {#}"
```
```   398   by (rule multiset_eqI) auto
```
```   399
```
```   400 lemma multiset_union_diff_commute:
```
```   401   assumes "B #\<inter> C = {#}"
```
```   402   shows "A + B - C = A - C + B"
```
```   403 proof (rule multiset_eqI)
```
```   404   fix x
```
```   405   from assms have "min (count B x) (count C x) = 0"
```
```   406     by (auto simp add: multiset_eq_iff)
```
```   407   then have "count B x = 0 \<or> count C x = 0"
```
```   408     by auto
```
```   409   then show "count (A + B - C) x = count (A - C + B) x"
```
```   410     by auto
```
```   411 qed
```
```   412
```
```   413 lemma empty_inter [simp]: "{#} #\<inter> M = {#}"
```
```   414   by (simp add: multiset_eq_iff)
```
```   415
```
```   416 lemma inter_empty [simp]: "M #\<inter> {#} = {#}"
```
```   417   by (simp add: multiset_eq_iff)
```
```   418
```
```   419 lemma inter_add_left1: "\<not> x \<in># N \<Longrightarrow> (M + {#x#}) #\<inter> N = M #\<inter> N"
```
```   420   by (simp add: multiset_eq_iff)
```
```   421
```
```   422 lemma inter_add_left2: "x \<in># N \<Longrightarrow> (M + {#x#}) #\<inter> N = (M #\<inter> (N - {#x#})) + {#x#}"
```
```   423   by (simp add: multiset_eq_iff)
```
```   424
```
```   425 lemma inter_add_right1: "\<not> x \<in># N \<Longrightarrow> N #\<inter> (M + {#x#}) = N #\<inter> M"
```
```   426   by (simp add: multiset_eq_iff)
```
```   427
```
```   428 lemma inter_add_right2: "x \<in># N \<Longrightarrow> N #\<inter> (M + {#x#}) = ((N - {#x#}) #\<inter> M) + {#x#}"
```
```   429   by (simp add: multiset_eq_iff)
```
```   430
```
```   431
```
```   432 subsubsection \<open>Bounded union\<close>
```
```   433
```
```   434 definition sup_subset_mset :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> 'a multiset"(infixl "#\<union>" 70)
```
```   435   where "sup_subset_mset A B = A + (B - A)"
```
```   436
```
```   437 interpretation subset_mset: semilattice_sup sup_subset_mset "op \<le>#" "op <#"
```
```   438 proof -
```
```   439   have [simp]: "m \<le> n \<Longrightarrow> q \<le> n \<Longrightarrow> m + (q - m) \<le> n" for m n q :: nat
```
```   440     by arith
```
```   441   show "class.semilattice_sup op #\<union> op \<le># op <#"
```
```   442     by standard (auto simp add: sup_subset_mset_def subseteq_mset_def)
```
```   443 qed
```
```   444
```
```   445 lemma sup_subset_mset_count [simp]: "count (A #\<union> B) x = max (count A x) (count B x)"
```
```   446   by (simp add: sup_subset_mset_def)
```
```   447
```
```   448 lemma empty_sup [simp]: "{#} #\<union> M = M"
```
```   449   by (simp add: multiset_eq_iff)
```
```   450
```
```   451 lemma sup_empty [simp]: "M #\<union> {#} = M"
```
```   452   by (simp add: multiset_eq_iff)
```
```   453
```
```   454 lemma sup_add_left1: "\<not> x \<in># N \<Longrightarrow> (M + {#x#}) #\<union> N = (M #\<union> N) + {#x#}"
```
```   455   by (simp add: multiset_eq_iff)
```
```   456
```
```   457 lemma sup_add_left2: "x \<in># N \<Longrightarrow> (M + {#x#}) #\<union> N = (M #\<union> (N - {#x#})) + {#x#}"
```
```   458   by (simp add: multiset_eq_iff)
```
```   459
```
```   460 lemma sup_add_right1: "\<not> x \<in># N \<Longrightarrow> N #\<union> (M + {#x#}) = (N #\<union> M) + {#x#}"
```
```   461   by (simp add: multiset_eq_iff)
```
```   462
```
```   463 lemma sup_add_right2: "x \<in># N \<Longrightarrow> N #\<union> (M + {#x#}) = ((N - {#x#}) #\<union> M) + {#x#}"
```
```   464   by (simp add: multiset_eq_iff)
```
```   465
```
```   466 subsubsection \<open>Subset is an order\<close>
```
```   467 interpretation subset_mset: order "op \<le>#" "op <#" by unfold_locales auto
```
```   468
```
```   469 subsubsection \<open>Filter (with comprehension syntax)\<close>
```
```   470
```
```   471 text \<open>Multiset comprehension\<close>
```
```   472
```
```   473 lift_definition filter_mset :: "('a \<Rightarrow> bool) \<Rightarrow> 'a multiset \<Rightarrow> 'a multiset"
```
```   474 is "\<lambda>P M. \<lambda>x. if P x then M x else 0"
```
```   475 by (rule filter_preserves_multiset)
```
```   476
```
```   477 lemma count_filter_mset [simp]: "count (filter_mset P M) a = (if P a then count M a else 0)"
```
```   478   by (simp add: filter_mset.rep_eq)
```
```   479
```
```   480 lemma filter_empty_mset [simp]: "filter_mset P {#} = {#}"
```
```   481   by (rule multiset_eqI) simp
```
```   482
```
```   483 lemma filter_single_mset [simp]: "filter_mset P {#x#} = (if P x then {#x#} else {#})"
```
```   484   by (rule multiset_eqI) simp
```
```   485
```
```   486 lemma filter_union_mset [simp]: "filter_mset P (M + N) = filter_mset P M + filter_mset P N"
```
```   487   by (rule multiset_eqI) simp
```
```   488
```
```   489 lemma filter_diff_mset [simp]: "filter_mset P (M - N) = filter_mset P M - filter_mset P N"
```
```   490   by (rule multiset_eqI) simp
```
```   491
```
```   492 lemma filter_inter_mset [simp]: "filter_mset P (M #\<inter> N) = filter_mset P M #\<inter> filter_mset P N"
```
```   493   by (rule multiset_eqI) simp
```
```   494
```
```   495 lemma multiset_filter_subset[simp]: "filter_mset f M \<le># M"
```
```   496   by (simp add: mset_less_eqI)
```
```   497
```
```   498 lemma multiset_filter_mono:
```
```   499   assumes "A \<le># B"
```
```   500   shows "filter_mset f A \<le># filter_mset f B"
```
```   501 proof -
```
```   502   from assms[unfolded mset_le_exists_conv]
```
```   503   obtain C where B: "B = A + C" by auto
```
```   504   show ?thesis unfolding B by auto
```
```   505 qed
```
```   506
```
```   507 syntax
```
```   508   "_MCollect" :: "pttrn \<Rightarrow> 'a multiset \<Rightarrow> bool \<Rightarrow> 'a multiset"    ("(1{# _ :# _./ _#})")
```
```   509 syntax (xsymbol)
```
```   510   "_MCollect" :: "pttrn \<Rightarrow> 'a multiset \<Rightarrow> bool \<Rightarrow> 'a multiset"    ("(1{# _ \<in># _./ _#})")
```
```   511 translations
```
```   512   "{#x \<in># M. P#}" == "CONST filter_mset (\<lambda>x. P) M"
```
```   513
```
```   514
```
```   515 subsubsection \<open>Set of elements\<close>
```
```   516
```
```   517 definition set_mset :: "'a multiset \<Rightarrow> 'a set"
```
```   518   where "set_mset M = {x. x \<in># M}"
```
```   519
```
```   520 lemma set_mset_empty [simp]: "set_mset {#} = {}"
```
```   521 by (simp add: set_mset_def)
```
```   522
```
```   523 lemma set_mset_single [simp]: "set_mset {#b#} = {b}"
```
```   524 by (simp add: set_mset_def)
```
```   525
```
```   526 lemma set_mset_union [simp]: "set_mset (M + N) = set_mset M \<union> set_mset N"
```
```   527 by (auto simp add: set_mset_def)
```
```   528
```
```   529 lemma set_mset_eq_empty_iff [simp]: "(set_mset M = {}) = (M = {#})"
```
```   530 by (auto simp add: set_mset_def multiset_eq_iff)
```
```   531
```
```   532 lemma mem_set_mset_iff [simp]: "(x \<in> set_mset M) = (x \<in># M)"
```
```   533 by (auto simp add: set_mset_def)
```
```   534
```
```   535 lemma set_mset_filter [simp]: "set_mset {# x\<in>#M. P x #} = set_mset M \<inter> {x. P x}"
```
```   536 by (auto simp add: set_mset_def)
```
```   537
```
```   538 lemma finite_set_mset [iff]: "finite (set_mset M)"
```
```   539   using count [of M] by (simp add: multiset_def set_mset_def)
```
```   540
```
```   541 lemma finite_Collect_mem [iff]: "finite {x. x \<in># M}"
```
```   542   unfolding set_mset_def[symmetric] by simp
```
```   543
```
```   544 lemma set_mset_mono: "A \<le># B \<Longrightarrow> set_mset A \<subseteq> set_mset B"
```
```   545   by (metis mset_leD subsetI mem_set_mset_iff)
```
```   546
```
```   547 lemma ball_set_mset_iff: "(\<forall>x \<in> set_mset M. P x) \<longleftrightarrow> (\<forall>x. x \<in># M \<longrightarrow> P x)"
```
```   548   by auto
```
```   549
```
```   550
```
```   551 subsubsection \<open>Size\<close>
```
```   552
```
```   553 definition wcount where "wcount f M = (\<lambda>x. count M x * Suc (f x))"
```
```   554
```
```   555 lemma wcount_union: "wcount f (M + N) a = wcount f M a + wcount f N a"
```
```   556   by (auto simp: wcount_def add_mult_distrib)
```
```   557
```
```   558 definition size_multiset :: "('a \<Rightarrow> nat) \<Rightarrow> 'a multiset \<Rightarrow> nat" where
```
```   559   "size_multiset f M = setsum (wcount f M) (set_mset M)"
```
```   560
```
```   561 lemmas size_multiset_eq = size_multiset_def[unfolded wcount_def]
```
```   562
```
```   563 instantiation multiset :: (type) size
```
```   564 begin
```
```   565
```
```   566 definition size_multiset where
```
```   567   size_multiset_overloaded_def: "size_multiset = Multiset.size_multiset (\<lambda>_. 0)"
```
```   568 instance ..
```
```   569
```
```   570 end
```
```   571
```
```   572 lemmas size_multiset_overloaded_eq =
```
```   573   size_multiset_overloaded_def[THEN fun_cong, unfolded size_multiset_eq, simplified]
```
```   574
```
```   575 lemma size_multiset_empty [simp]: "size_multiset f {#} = 0"
```
```   576 by (simp add: size_multiset_def)
```
```   577
```
```   578 lemma size_empty [simp]: "size {#} = 0"
```
```   579 by (simp add: size_multiset_overloaded_def)
```
```   580
```
```   581 lemma size_multiset_single [simp]: "size_multiset f {#b#} = Suc (f b)"
```
```   582 by (simp add: size_multiset_eq)
```
```   583
```
```   584 lemma size_single [simp]: "size {#b#} = 1"
```
```   585 by (simp add: size_multiset_overloaded_def)
```
```   586
```
```   587 lemma setsum_wcount_Int:
```
```   588   "finite A \<Longrightarrow> setsum (wcount f N) (A \<inter> set_mset N) = setsum (wcount f N) A"
```
```   589 apply (induct rule: finite_induct)
```
```   590  apply simp
```
```   591 apply (simp add: Int_insert_left set_mset_def wcount_def)
```
```   592 done
```
```   593
```
```   594 lemma size_multiset_union [simp]:
```
```   595   "size_multiset f (M + N::'a multiset) = size_multiset f M + size_multiset f N"
```
```   596 apply (simp add: size_multiset_def setsum_Un_nat setsum.distrib setsum_wcount_Int wcount_union)
```
```   597 apply (subst Int_commute)
```
```   598 apply (simp add: setsum_wcount_Int)
```
```   599 done
```
```   600
```
```   601 lemma size_union [simp]: "size (M + N::'a multiset) = size M + size N"
```
```   602 by (auto simp add: size_multiset_overloaded_def)
```
```   603
```
```   604 lemma size_multiset_eq_0_iff_empty [iff]: "(size_multiset f M = 0) = (M = {#})"
```
```   605 by (auto simp add: size_multiset_eq multiset_eq_iff)
```
```   606
```
```   607 lemma size_eq_0_iff_empty [iff]: "(size M = 0) = (M = {#})"
```
```   608 by (auto simp add: size_multiset_overloaded_def)
```
```   609
```
```   610 lemma nonempty_has_size: "(S \<noteq> {#}) = (0 < size S)"
```
```   611 by (metis gr0I gr_implies_not0 size_empty size_eq_0_iff_empty)
```
```   612
```
```   613 lemma size_eq_Suc_imp_elem: "size M = Suc n \<Longrightarrow> \<exists>a. a \<in># M"
```
```   614 apply (unfold size_multiset_overloaded_eq)
```
```   615 apply (drule setsum_SucD)
```
```   616 apply auto
```
```   617 done
```
```   618
```
```   619 lemma size_eq_Suc_imp_eq_union:
```
```   620   assumes "size M = Suc n"
```
```   621   shows "\<exists>a N. M = N + {#a#}"
```
```   622 proof -
```
```   623   from assms obtain a where "a \<in># M"
```
```   624     by (erule size_eq_Suc_imp_elem [THEN exE])
```
```   625   then have "M = M - {#a#} + {#a#}" by simp
```
```   626   then show ?thesis by blast
```
```   627 qed
```
```   628
```
```   629 lemma size_mset_mono:
```
```   630   fixes A B :: "'a multiset"
```
```   631   assumes "A \<le># B"
```
```   632   shows "size A \<le> size B"
```
```   633 proof -
```
```   634   from assms[unfolded mset_le_exists_conv]
```
```   635   obtain C where B: "B = A + C" by auto
```
```   636   show ?thesis unfolding B by (induct C) auto
```
```   637 qed
```
```   638
```
```   639 lemma size_filter_mset_lesseq[simp]: "size (filter_mset f M) \<le> size M"
```
```   640 by (rule size_mset_mono[OF multiset_filter_subset])
```
```   641
```
```   642 lemma size_Diff_submset:
```
```   643   "M \<le># M' \<Longrightarrow> size (M' - M) = size M' - size(M::'a multiset)"
```
```   644 by (metis add_diff_cancel_left' size_union mset_le_exists_conv)
```
```   645
```
```   646 subsection \<open>Induction and case splits\<close>
```
```   647
```
```   648 theorem multiset_induct [case_names empty add, induct type: multiset]:
```
```   649   assumes empty: "P {#}"
```
```   650   assumes add: "\<And>M x. P M \<Longrightarrow> P (M + {#x#})"
```
```   651   shows "P M"
```
```   652 proof (induct n \<equiv> "size M" arbitrary: M)
```
```   653   case 0 thus "P M" by (simp add: empty)
```
```   654 next
```
```   655   case (Suc k)
```
```   656   obtain N x where "M = N + {#x#}"
```
```   657     using \<open>Suc k = size M\<close> [symmetric]
```
```   658     using size_eq_Suc_imp_eq_union by fast
```
```   659   with Suc add show "P M" by simp
```
```   660 qed
```
```   661
```
```   662 lemma multi_nonempty_split: "M \<noteq> {#} \<Longrightarrow> \<exists>A a. M = A + {#a#}"
```
```   663 by (induct M) auto
```
```   664
```
```   665 lemma multiset_cases [cases type]:
```
```   666   obtains (empty) "M = {#}"
```
```   667     | (add) N x where "M = N + {#x#}"
```
```   668   using assms by (induct M) simp_all
```
```   669
```
```   670 lemma multi_drop_mem_not_eq: "c \<in># B \<Longrightarrow> B - {#c#} \<noteq> B"
```
```   671 by (cases "B = {#}") (auto dest: multi_member_split)
```
```   672
```
```   673 lemma multiset_partition: "M = {# x\<in>#M. P x #} + {# x\<in>#M. \<not> P x #}"
```
```   674 apply (subst multiset_eq_iff)
```
```   675 apply auto
```
```   676 done
```
```   677
```
```   678 lemma mset_less_size: "(A::'a multiset) <# B \<Longrightarrow> size A < size B"
```
```   679 proof (induct A arbitrary: B)
```
```   680   case (empty M)
```
```   681   then have "M \<noteq> {#}" by (simp add: mset_less_empty_nonempty)
```
```   682   then obtain M' x where "M = M' + {#x#}"
```
```   683     by (blast dest: multi_nonempty_split)
```
```   684   then show ?case by simp
```
```   685 next
```
```   686   case (add S x T)
```
```   687   have IH: "\<And>B. S <# B \<Longrightarrow> size S < size B" by fact
```
```   688   have SxsubT: "S + {#x#} <# T" by fact
```
```   689   then have "x \<in># T" and "S <# T" by (auto dest: mset_less_insertD)
```
```   690   then obtain T' where T: "T = T' + {#x#}"
```
```   691     by (blast dest: multi_member_split)
```
```   692   then have "S <# T'" using SxsubT
```
```   693     by (blast intro: mset_less_add_bothsides)
```
```   694   then have "size S < size T'" using IH by simp
```
```   695   then show ?case using T by simp
```
```   696 qed
```
```   697
```
```   698
```
```   699 lemma size_1_singleton_mset: "size M = 1 \<Longrightarrow> \<exists>a. M = {#a#}"
```
```   700 by (cases M) auto
```
```   701
```
```   702 subsubsection \<open>Strong induction and subset induction for multisets\<close>
```
```   703
```
```   704 text \<open>Well-foundedness of strict subset relation\<close>
```
```   705
```
```   706 lemma wf_less_mset_rel: "wf {(M, N :: 'a multiset). M <# N}"
```
```   707 apply (rule wf_measure [THEN wf_subset, where f1=size])
```
```   708 apply (clarsimp simp: measure_def inv_image_def mset_less_size)
```
```   709 done
```
```   710
```
```   711 lemma full_multiset_induct [case_names less]:
```
```   712 assumes ih: "\<And>B. \<forall>(A::'a multiset). A <# B \<longrightarrow> P A \<Longrightarrow> P B"
```
```   713 shows "P B"
```
```   714 apply (rule wf_less_mset_rel [THEN wf_induct])
```
```   715 apply (rule ih, auto)
```
```   716 done
```
```   717
```
```   718 lemma multi_subset_induct [consumes 2, case_names empty add]:
```
```   719   assumes "F \<le># A"
```
```   720     and empty: "P {#}"
```
```   721     and insert: "\<And>a F. a \<in># A \<Longrightarrow> P F \<Longrightarrow> P (F + {#a#})"
```
```   722   shows "P F"
```
```   723 proof -
```
```   724   from \<open>F \<le># A\<close>
```
```   725   show ?thesis
```
```   726   proof (induct F)
```
```   727     show "P {#}" by fact
```
```   728   next
```
```   729     fix x F
```
```   730     assume P: "F \<le># A \<Longrightarrow> P F" and i: "F + {#x#} \<le># A"
```
```   731     show "P (F + {#x#})"
```
```   732     proof (rule insert)
```
```   733       from i show "x \<in># A" by (auto dest: mset_le_insertD)
```
```   734       from i have "F \<le># A" by (auto dest: mset_le_insertD)
```
```   735       with P show "P F" .
```
```   736     qed
```
```   737   qed
```
```   738 qed
```
```   739
```
```   740
```
```   741 subsection \<open>The fold combinator\<close>
```
```   742
```
```   743 definition fold_mset :: "('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a multiset \<Rightarrow> 'b"
```
```   744 where
```
```   745   "fold_mset f s M = Finite_Set.fold (\<lambda>x. f x ^^ count M x) s (set_mset M)"
```
```   746
```
```   747 lemma fold_mset_empty [simp]: "fold_mset f s {#} = s"
```
```   748   by (simp add: fold_mset_def)
```
```   749
```
```   750 context comp_fun_commute
```
```   751 begin
```
```   752
```
```   753 lemma fold_mset_insert: "fold_mset f s (M + {#x#}) = f x (fold_mset f s M)"
```
```   754 proof -
```
```   755   interpret mset: comp_fun_commute "\<lambda>y. f y ^^ count M y"
```
```   756     by (fact comp_fun_commute_funpow)
```
```   757   interpret mset_union: comp_fun_commute "\<lambda>y. f y ^^ count (M + {#x#}) y"
```
```   758     by (fact comp_fun_commute_funpow)
```
```   759   show ?thesis
```
```   760   proof (cases "x \<in> set_mset M")
```
```   761     case False
```
```   762     then have *: "count (M + {#x#}) x = 1" by simp
```
```   763     from False have "Finite_Set.fold (\<lambda>y. f y ^^ count (M + {#x#}) y) s (set_mset M) =
```
```   764       Finite_Set.fold (\<lambda>y. f y ^^ count M y) s (set_mset M)"
```
```   765       by (auto intro!: Finite_Set.fold_cong comp_fun_commute_funpow)
```
```   766     with False * show ?thesis
```
```   767       by (simp add: fold_mset_def del: count_union)
```
```   768   next
```
```   769     case True
```
```   770     def N \<equiv> "set_mset M - {x}"
```
```   771     from N_def True have *: "set_mset M = insert x N" "x \<notin> N" "finite N" by auto
```
```   772     then have "Finite_Set.fold (\<lambda>y. f y ^^ count (M + {#x#}) y) s N =
```
```   773       Finite_Set.fold (\<lambda>y. f y ^^ count M y) s N"
```
```   774       by (auto intro!: Finite_Set.fold_cong comp_fun_commute_funpow)
```
```   775     with * show ?thesis by (simp add: fold_mset_def del: count_union) simp
```
```   776   qed
```
```   777 qed
```
```   778
```
```   779 corollary fold_mset_single [simp]: "fold_mset f s {#x#} = f x s"
```
```   780 proof -
```
```   781   have "fold_mset f s ({#} + {#x#}) = f x s" by (simp only: fold_mset_insert) simp
```
```   782   then show ?thesis by simp
```
```   783 qed
```
```   784
```
```   785 lemma fold_mset_fun_left_comm: "f x (fold_mset f s M) = fold_mset f (f x s) M"
```
```   786   by (induct M) (simp_all add: fold_mset_insert fun_left_comm)
```
```   787
```
```   788 lemma fold_mset_union [simp]: "fold_mset f s (M + N) = fold_mset f (fold_mset f s M) N"
```
```   789 proof (induct M)
```
```   790   case empty then show ?case by simp
```
```   791 next
```
```   792   case (add M x)
```
```   793   have "M + {#x#} + N = (M + N) + {#x#}"
```
```   794     by (simp add: ac_simps)
```
```   795   with add show ?case by (simp add: fold_mset_insert fold_mset_fun_left_comm)
```
```   796 qed
```
```   797
```
```   798 lemma fold_mset_fusion:
```
```   799   assumes "comp_fun_commute g"
```
```   800     and *: "\<And>x y. h (g x y) = f x (h y)"
```
```   801   shows "h (fold_mset g w A) = fold_mset f (h w) A"
```
```   802 proof -
```
```   803   interpret comp_fun_commute g by (fact assms)
```
```   804   from * show ?thesis by (induct A) auto
```
```   805 qed
```
```   806
```
```   807 end
```
```   808
```
```   809 text \<open>
```
```   810   A note on code generation: When defining some function containing a
```
```   811   subterm @{term "fold_mset F"}, code generation is not automatic. When
```
```   812   interpreting locale \<open>left_commutative\<close> with \<open>F\<close>, the
```
```   813   would be code thms for @{const fold_mset} become thms like
```
```   814   @{term "fold_mset F z {#} = z"} where \<open>F\<close> is not a pattern but
```
```   815   contains defined symbols, i.e.\ is not a code thm. Hence a separate
```
```   816   constant with its own code thms needs to be introduced for \<open>F\<close>. See the image operator below.
```
```   817 \<close>
```
```   818
```
```   819
```
```   820 subsection \<open>Image\<close>
```
```   821
```
```   822 definition image_mset :: "('a \<Rightarrow> 'b) \<Rightarrow> 'a multiset \<Rightarrow> 'b multiset" where
```
```   823   "image_mset f = fold_mset (plus \<circ> single \<circ> f) {#}"
```
```   824
```
```   825 lemma comp_fun_commute_mset_image: "comp_fun_commute (plus \<circ> single \<circ> f)"
```
```   826 proof
```
```   827 qed (simp add: ac_simps fun_eq_iff)
```
```   828
```
```   829 lemma image_mset_empty [simp]: "image_mset f {#} = {#}"
```
```   830   by (simp add: image_mset_def)
```
```   831
```
```   832 lemma image_mset_single [simp]: "image_mset f {#x#} = {#f x#}"
```
```   833 proof -
```
```   834   interpret comp_fun_commute "plus \<circ> single \<circ> f"
```
```   835     by (fact comp_fun_commute_mset_image)
```
```   836   show ?thesis by (simp add: image_mset_def)
```
```   837 qed
```
```   838
```
```   839 lemma image_mset_union [simp]: "image_mset f (M + N) = image_mset f M + image_mset f N"
```
```   840 proof -
```
```   841   interpret comp_fun_commute "plus \<circ> single \<circ> f"
```
```   842     by (fact comp_fun_commute_mset_image)
```
```   843   show ?thesis by (induct N) (simp_all add: image_mset_def ac_simps)
```
```   844 qed
```
```   845
```
```   846 corollary image_mset_insert: "image_mset f (M + {#a#}) = image_mset f M + {#f a#}"
```
```   847   by simp
```
```   848
```
```   849 lemma set_image_mset [simp]: "set_mset (image_mset f M) = image f (set_mset M)"
```
```   850   by (induct M) simp_all
```
```   851
```
```   852 lemma size_image_mset [simp]: "size (image_mset f M) = size M"
```
```   853   by (induct M) simp_all
```
```   854
```
```   855 lemma image_mset_is_empty_iff [simp]: "image_mset f M = {#} \<longleftrightarrow> M = {#}"
```
```   856   by (cases M) auto
```
```   857
```
```   858 syntax
```
```   859   "_comprehension1_mset" :: "'a \<Rightarrow> 'b \<Rightarrow> 'b multiset \<Rightarrow> 'a multiset"
```
```   860       ("({#_/. _ :# _#})")
```
```   861 translations
```
```   862   "{#e. x:#M#}" == "CONST image_mset (\<lambda>x. e) M"
```
```   863
```
```   864 syntax (xsymbols)
```
```   865   "_comprehension2_mset" :: "'a \<Rightarrow> 'b \<Rightarrow> 'b multiset \<Rightarrow> 'a multiset"
```
```   866       ("({#_/. _ \<in># _#})")
```
```   867 translations
```
```   868   "{#e. x \<in># M#}" == "CONST image_mset (\<lambda>x. e) M"
```
```   869
```
```   870 syntax
```
```   871   "_comprehension3_mset" :: "'a \<Rightarrow> 'b \<Rightarrow> 'b multiset \<Rightarrow> bool \<Rightarrow> 'a multiset"
```
```   872       ("({#_/ | _ :# _./ _#})")
```
```   873 translations
```
```   874   "{#e | x:#M. P#}" \<rightharpoonup> "{#e. x :# {# x:#M. P#}#}"
```
```   875
```
```   876 syntax
```
```   877   "_comprehension4_mset" :: "'a \<Rightarrow> 'b \<Rightarrow> 'b multiset \<Rightarrow> bool \<Rightarrow> 'a multiset"
```
```   878       ("({#_/ | _ \<in># _./ _#})")
```
```   879 translations
```
```   880   "{#e | x\<in>#M. P#}" \<rightharpoonup> "{#e. x \<in># {# x\<in>#M. P#}#}"
```
```   881
```
```   882 text \<open>
```
```   883   This allows to write not just filters like @{term "{#x\<in>#M. x<c#}"}
```
```   884   but also images like @{term "{#x+x. x\<in>#M #}"} and @{term [source]
```
```   885   "{#x+x|x\<in>#M. x<c#}"}, where the latter is currently displayed as
```
```   886   @{term "{#x+x|x\<in>#M. x<c#}"}.
```
```   887 \<close>
```
```   888
```
```   889 lemma in_image_mset: "y \<in># {#f x. x \<in># M#} \<longleftrightarrow> y \<in> f ` set_mset M"
```
```   890 by (metis mem_set_mset_iff set_image_mset)
```
```   891
```
```   892 functor image_mset: image_mset
```
```   893 proof -
```
```   894   fix f g show "image_mset f \<circ> image_mset g = image_mset (f \<circ> g)"
```
```   895   proof
```
```   896     fix A
```
```   897     show "(image_mset f \<circ> image_mset g) A = image_mset (f \<circ> g) A"
```
```   898       by (induct A) simp_all
```
```   899   qed
```
```   900   show "image_mset id = id"
```
```   901   proof
```
```   902     fix A
```
```   903     show "image_mset id A = id A"
```
```   904       by (induct A) simp_all
```
```   905   qed
```
```   906 qed
```
```   907
```
```   908 declare
```
```   909   image_mset.id [simp]
```
```   910   image_mset.identity [simp]
```
```   911
```
```   912 lemma image_mset_id[simp]: "image_mset id x = x"
```
```   913   unfolding id_def by auto
```
```   914
```
```   915 lemma image_mset_cong: "(\<And>x. x \<in># M \<Longrightarrow> f x = g x) \<Longrightarrow> {#f x. x \<in># M#} = {#g x. x \<in># M#}"
```
```   916   by (induct M) auto
```
```   917
```
```   918 lemma image_mset_cong_pair:
```
```   919   "(\<forall>x y. (x, y) \<in># M \<longrightarrow> f x y = g x y) \<Longrightarrow> {#f x y. (x, y) \<in># M#} = {#g x y. (x, y) \<in># M#}"
```
```   920   by (metis image_mset_cong split_cong)
```
```   921
```
```   922
```
```   923 subsection \<open>Further conversions\<close>
```
```   924
```
```   925 primrec mset :: "'a list \<Rightarrow> 'a multiset" where
```
```   926   "mset [] = {#}" |
```
```   927   "mset (a # x) = mset x + {# a #}"
```
```   928
```
```   929 lemma in_multiset_in_set:
```
```   930   "x \<in># mset xs \<longleftrightarrow> x \<in> set xs"
```
```   931   by (induct xs) simp_all
```
```   932
```
```   933 lemma count_mset:
```
```   934   "count (mset xs) x = length (filter (\<lambda>y. x = y) xs)"
```
```   935   by (induct xs) simp_all
```
```   936
```
```   937 lemma mset_zero_iff[simp]: "(mset x = {#}) = (x = [])"
```
```   938   by (induct x) auto
```
```   939
```
```   940 lemma mset_zero_iff_right[simp]: "({#} = mset x) = (x = [])"
```
```   941 by (induct x) auto
```
```   942
```
```   943 lemma set_mset_mset[simp]: "set_mset (mset x) = set x"
```
```   944 by (induct x) auto
```
```   945
```
```   946 lemma mem_set_multiset_eq: "x \<in> set xs = (x \<in># mset xs)"
```
```   947 by (induct xs) auto
```
```   948
```
```   949 lemma size_mset [simp]: "size (mset xs) = length xs"
```
```   950   by (induct xs) simp_all
```
```   951
```
```   952 lemma mset_append [simp]: "mset (xs @ ys) = mset xs + mset ys"
```
```   953   by (induct xs arbitrary: ys) (auto simp: ac_simps)
```
```   954
```
```   955 lemma mset_filter: "mset (filter P xs) = {#x \<in># mset xs. P x #}"
```
```   956   by (induct xs) simp_all
```
```   957
```
```   958 lemma mset_rev [simp]:
```
```   959   "mset (rev xs) = mset xs"
```
```   960   by (induct xs) simp_all
```
```   961
```
```   962 lemma surj_mset: "surj mset"
```
```   963 apply (unfold surj_def)
```
```   964 apply (rule allI)
```
```   965 apply (rule_tac M = y in multiset_induct)
```
```   966  apply auto
```
```   967 apply (rule_tac x = "x # xa" in exI)
```
```   968 apply auto
```
```   969 done
```
```   970
```
```   971 lemma set_count_greater_0: "set x = {a. count (mset x) a > 0}"
```
```   972 by (induct x) auto
```
```   973
```
```   974 lemma distinct_count_atmost_1:
```
```   975   "distinct x = (\<forall>a. count (mset x) a = (if a \<in> set x then 1 else 0))"
```
```   976   apply (induct x, simp, rule iffI, simp_all)
```
```   977   subgoal for a b
```
```   978     apply (rule conjI)
```
```   979     apply (simp_all add: set_mset_mset [symmetric] del: set_mset_mset)
```
```   980     apply (erule_tac x = a in allE, simp)
```
```   981     apply clarify
```
```   982     apply (erule_tac x = aa in allE, simp)
```
```   983     done
```
```   984   done
```
```   985
```
```   986 lemma mset_eq_setD: "mset xs = mset ys \<Longrightarrow> set xs = set ys"
```
```   987 by (rule) (auto simp add:multiset_eq_iff set_count_greater_0)
```
```   988
```
```   989 lemma set_eq_iff_mset_eq_distinct:
```
```   990   "distinct x \<Longrightarrow> distinct y \<Longrightarrow>
```
```   991     (set x = set y) = (mset x = mset y)"
```
```   992 by (auto simp: multiset_eq_iff distinct_count_atmost_1)
```
```   993
```
```   994 lemma set_eq_iff_mset_remdups_eq:
```
```   995    "(set x = set y) = (mset (remdups x) = mset (remdups y))"
```
```   996 apply (rule iffI)
```
```   997 apply (simp add: set_eq_iff_mset_eq_distinct[THEN iffD1])
```
```   998 apply (drule distinct_remdups [THEN distinct_remdups
```
```   999       [THEN set_eq_iff_mset_eq_distinct [THEN iffD2]]])
```
```  1000 apply simp
```
```  1001 done
```
```  1002
```
```  1003 lemma mset_compl_union [simp]: "mset [x\<leftarrow>xs. P x] + mset [x\<leftarrow>xs. \<not>P x] = mset xs"
```
```  1004   by (induct xs) (auto simp: ac_simps)
```
```  1005
```
```  1006 lemma nth_mem_mset: "i < length ls \<Longrightarrow> (ls ! i) \<in># mset ls"
```
```  1007 proof (induct ls arbitrary: i)
```
```  1008   case Nil
```
```  1009   then show ?case by simp
```
```  1010 next
```
```  1011   case Cons
```
```  1012   then show ?case by (cases i) auto
```
```  1013 qed
```
```  1014
```
```  1015 lemma mset_remove1[simp]: "mset (remove1 a xs) = mset xs - {#a#}"
```
```  1016   by (induct xs) (auto simp add: multiset_eq_iff)
```
```  1017
```
```  1018 lemma mset_eq_length:
```
```  1019   assumes "mset xs = mset ys"
```
```  1020   shows "length xs = length ys"
```
```  1021   using assms by (metis size_mset)
```
```  1022
```
```  1023 lemma mset_eq_length_filter:
```
```  1024   assumes "mset xs = mset ys"
```
```  1025   shows "length (filter (\<lambda>x. z = x) xs) = length (filter (\<lambda>y. z = y) ys)"
```
```  1026   using assms by (metis count_mset)
```
```  1027
```
```  1028 lemma fold_multiset_equiv:
```
```  1029   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"
```
```  1030     and equiv: "mset xs = mset ys"
```
```  1031   shows "List.fold f xs = List.fold f ys"
```
```  1032   using f equiv [symmetric]
```
```  1033 proof (induct xs arbitrary: ys)
```
```  1034   case Nil
```
```  1035   then show ?case by simp
```
```  1036 next
```
```  1037   case (Cons x xs)
```
```  1038   then have *: "set ys = set (x # xs)"
```
```  1039     by (blast dest: mset_eq_setD)
```
```  1040   have "\<And>x y. x \<in> set ys \<Longrightarrow> y \<in> set ys \<Longrightarrow> f x \<circ> f y = f y \<circ> f x"
```
```  1041     by (rule Cons.prems(1)) (simp_all add: *)
```
```  1042   moreover from * have "x \<in> set ys"
```
```  1043     by simp
```
```  1044   ultimately have "List.fold f ys = List.fold f (remove1 x ys) \<circ> f x"
```
```  1045     by (fact fold_remove1_split)
```
```  1046   moreover from Cons.prems have "List.fold f xs = List.fold f (remove1 x ys)"
```
```  1047     by (auto intro: Cons.hyps)
```
```  1048   ultimately show ?case by simp
```
```  1049 qed
```
```  1050
```
```  1051 lemma mset_insort [simp]: "mset (insort x xs) = mset xs + {#x#}"
```
```  1052   by (induct xs) (simp_all add: ac_simps)
```
```  1053
```
```  1054 lemma mset_map: "mset (map f xs) = image_mset f (mset xs)"
```
```  1055   by (induct xs) simp_all
```
```  1056
```
```  1057 global_interpretation mset_set: folding "\<lambda>x M. {#x#} + M" "{#}"
```
```  1058   defines mset_set = "folding.F (\<lambda>x M. {#x#} + M) {#}"
```
```  1059   by standard (simp add: fun_eq_iff ac_simps)
```
```  1060
```
```  1061 lemma count_mset_set [simp]:
```
```  1062   "finite A \<Longrightarrow> x \<in> A \<Longrightarrow> count (mset_set A) x = 1" (is "PROP ?P")
```
```  1063   "\<not> finite A \<Longrightarrow> count (mset_set A) x = 0" (is "PROP ?Q")
```
```  1064   "x \<notin> A \<Longrightarrow> count (mset_set A) x = 0" (is "PROP ?R")
```
```  1065 proof -
```
```  1066   have *: "count (mset_set A) x = 0" if "x \<notin> A" for A
```
```  1067   proof (cases "finite A")
```
```  1068     case False then show ?thesis by simp
```
```  1069   next
```
```  1070     case True from True \<open>x \<notin> A\<close> show ?thesis by (induct A) auto
```
```  1071   qed
```
```  1072   then show "PROP ?P" "PROP ?Q" "PROP ?R"
```
```  1073   by (auto elim!: Set.set_insert)
```
```  1074 qed \<comment> \<open>TODO: maybe define @{const mset_set} also in terms of @{const Abs_multiset}\<close>
```
```  1075
```
```  1076 lemma elem_mset_set[simp, intro]: "finite A \<Longrightarrow> x \<in># mset_set A \<longleftrightarrow> x \<in> A"
```
```  1077   by (induct A rule: finite_induct) simp_all
```
```  1078
```
```  1079 context linorder
```
```  1080 begin
```
```  1081
```
```  1082 definition sorted_list_of_multiset :: "'a multiset \<Rightarrow> 'a list"
```
```  1083 where
```
```  1084   "sorted_list_of_multiset M = fold_mset insort [] M"
```
```  1085
```
```  1086 lemma sorted_list_of_multiset_empty [simp]:
```
```  1087   "sorted_list_of_multiset {#} = []"
```
```  1088   by (simp add: sorted_list_of_multiset_def)
```
```  1089
```
```  1090 lemma sorted_list_of_multiset_singleton [simp]:
```
```  1091   "sorted_list_of_multiset {#x#} = [x]"
```
```  1092 proof -
```
```  1093   interpret comp_fun_commute insort by (fact comp_fun_commute_insort)
```
```  1094   show ?thesis by (simp add: sorted_list_of_multiset_def)
```
```  1095 qed
```
```  1096
```
```  1097 lemma sorted_list_of_multiset_insert [simp]:
```
```  1098   "sorted_list_of_multiset (M + {#x#}) = List.insort x (sorted_list_of_multiset M)"
```
```  1099 proof -
```
```  1100   interpret comp_fun_commute insort by (fact comp_fun_commute_insort)
```
```  1101   show ?thesis by (simp add: sorted_list_of_multiset_def)
```
```  1102 qed
```
```  1103
```
```  1104 end
```
```  1105
```
```  1106 lemma mset_sorted_list_of_multiset [simp]:
```
```  1107   "mset (sorted_list_of_multiset M) = M"
```
```  1108 by (induct M) simp_all
```
```  1109
```
```  1110 lemma sorted_list_of_multiset_mset [simp]:
```
```  1111   "sorted_list_of_multiset (mset xs) = sort xs"
```
```  1112 by (induct xs) simp_all
```
```  1113
```
```  1114 lemma finite_set_mset_mset_set[simp]:
```
```  1115   "finite A \<Longrightarrow> set_mset (mset_set A) = A"
```
```  1116 by (induct A rule: finite_induct) simp_all
```
```  1117
```
```  1118 lemma infinite_set_mset_mset_set:
```
```  1119   "\<not> finite A \<Longrightarrow> set_mset (mset_set A) = {}"
```
```  1120 by simp
```
```  1121
```
```  1122 lemma set_sorted_list_of_multiset [simp]:
```
```  1123   "set (sorted_list_of_multiset M) = set_mset M"
```
```  1124 by (induct M) (simp_all add: set_insort)
```
```  1125
```
```  1126 lemma sorted_list_of_mset_set [simp]:
```
```  1127   "sorted_list_of_multiset (mset_set A) = sorted_list_of_set A"
```
```  1128 by (cases "finite A") (induct A rule: finite_induct, simp_all add: ac_simps)
```
```  1129
```
```  1130
```
```  1131 subsection \<open>Replicate operation\<close>
```
```  1132
```
```  1133 definition replicate_mset :: "nat \<Rightarrow> 'a \<Rightarrow> 'a multiset" where
```
```  1134   "replicate_mset n x = ((op + {#x#}) ^^ n) {#}"
```
```  1135
```
```  1136 lemma replicate_mset_0[simp]: "replicate_mset 0 x = {#}"
```
```  1137   unfolding replicate_mset_def by simp
```
```  1138
```
```  1139 lemma replicate_mset_Suc[simp]: "replicate_mset (Suc n) x = replicate_mset n x + {#x#}"
```
```  1140   unfolding replicate_mset_def by (induct n) (auto intro: add.commute)
```
```  1141
```
```  1142 lemma in_replicate_mset[simp]: "x \<in># replicate_mset n y \<longleftrightarrow> n > 0 \<and> x = y"
```
```  1143   unfolding replicate_mset_def by (induct n) simp_all
```
```  1144
```
```  1145 lemma count_replicate_mset[simp]: "count (replicate_mset n x) y = (if y = x then n else 0)"
```
```  1146   unfolding replicate_mset_def by (induct n) simp_all
```
```  1147
```
```  1148 lemma set_mset_replicate_mset_subset[simp]: "set_mset (replicate_mset n x) = (if n = 0 then {} else {x})"
```
```  1149   by (auto split: if_splits)
```
```  1150
```
```  1151 lemma size_replicate_mset[simp]: "size (replicate_mset n M) = n"
```
```  1152   by (induct n, simp_all)
```
```  1153
```
```  1154 lemma count_le_replicate_mset_le: "n \<le> count M x \<longleftrightarrow> replicate_mset n x \<le># M"
```
```  1155   by (auto simp add: assms mset_less_eqI) (metis count_replicate_mset subseteq_mset_def)
```
```  1156
```
```  1157 lemma filter_eq_replicate_mset: "{#y \<in># D. y = x#} = replicate_mset (count D x) x"
```
```  1158   by (induct D) simp_all
```
```  1159
```
```  1160 lemma replicate_count_mset_eq_filter_eq:
```
```  1161   "replicate (count (mset xs) k) k = filter (HOL.eq k) xs"
```
```  1162   by (induct xs) auto
```
```  1163
```
```  1164
```
```  1165 subsection \<open>Big operators\<close>
```
```  1166
```
```  1167 no_notation times (infixl "*" 70)
```
```  1168 no_notation Groups.one ("1")
```
```  1169
```
```  1170 locale comm_monoid_mset = comm_monoid
```
```  1171 begin
```
```  1172
```
```  1173 definition F :: "'a multiset \<Rightarrow> 'a"
```
```  1174   where eq_fold: "F M = fold_mset f 1 M"
```
```  1175
```
```  1176 lemma empty [simp]: "F {#} = 1"
```
```  1177   by (simp add: eq_fold)
```
```  1178
```
```  1179 lemma singleton [simp]: "F {#x#} = x"
```
```  1180 proof -
```
```  1181   interpret comp_fun_commute
```
```  1182     by standard (simp add: fun_eq_iff left_commute)
```
```  1183   show ?thesis by (simp add: eq_fold)
```
```  1184 qed
```
```  1185
```
```  1186 lemma union [simp]: "F (M + N) = F M * F N"
```
```  1187 proof -
```
```  1188   interpret comp_fun_commute f
```
```  1189     by standard (simp add: fun_eq_iff left_commute)
```
```  1190   show ?thesis
```
```  1191     by (induct N) (simp_all add: left_commute eq_fold)
```
```  1192 qed
```
```  1193
```
```  1194 end
```
```  1195
```
```  1196 lemma comp_fun_commute_plus_mset[simp]: "comp_fun_commute (op + :: 'a multiset \<Rightarrow> _ \<Rightarrow> _)"
```
```  1197   by standard (simp add: add_ac comp_def)
```
```  1198
```
```  1199 declare comp_fun_commute.fold_mset_insert[OF comp_fun_commute_plus_mset, simp]
```
```  1200
```
```  1201 lemma in_mset_fold_plus_iff[iff]: "x \<in># fold_mset (op +) M NN \<longleftrightarrow> x \<in># M \<or> (\<exists>N. N \<in># NN \<and> x \<in># N)"
```
```  1202   by (induct NN) auto
```
```  1203
```
```  1204 notation times (infixl "*" 70)
```
```  1205 notation Groups.one ("1")
```
```  1206
```
```  1207 context comm_monoid_add
```
```  1208 begin
```
```  1209
```
```  1210 sublocale msetsum: comm_monoid_mset plus 0
```
```  1211   defines msetsum = msetsum.F ..
```
```  1212
```
```  1213 lemma (in semiring_1) msetsum_replicate_mset [simp]:
```
```  1214   "msetsum (replicate_mset n a) = of_nat n * a"
```
```  1215   by (induct n) (simp_all add: algebra_simps)
```
```  1216
```
```  1217 lemma setsum_unfold_msetsum:
```
```  1218   "setsum f A = msetsum (image_mset f (mset_set A))"
```
```  1219   by (cases "finite A") (induct A rule: finite_induct, simp_all)
```
```  1220
```
```  1221 end
```
```  1222
```
```  1223 lemma msetsum_diff:
```
```  1224   fixes M N :: "('a :: ordered_cancel_comm_monoid_diff) multiset"
```
```  1225   shows "N \<le># M \<Longrightarrow> msetsum (M - N) = msetsum M - msetsum N"
```
```  1226   by (metis add_diff_cancel_right' msetsum.union subset_mset.diff_add)
```
```  1227
```
```  1228 lemma size_eq_msetsum: "size M = msetsum (image_mset (\<lambda>_. 1) M)"
```
```  1229 proof (induct M)
```
```  1230   case empty then show ?case by simp
```
```  1231 next
```
```  1232   case (add M x) then show ?case
```
```  1233     by (cases "x \<in> set_mset M")
```
```  1234       (simp_all del: mem_set_mset_iff add: size_multiset_overloaded_eq setsum.distrib setsum.delta' insert_absorb, simp)
```
```  1235 qed
```
```  1236
```
```  1237
```
```  1238 abbreviation Union_mset :: "'a multiset multiset \<Rightarrow> 'a multiset" where
```
```  1239   "Union_mset MM \<equiv> msetsum MM"
```
```  1240
```
```  1241 notation (xsymbols) Union_mset ("\<Union>#_" [900] 900)
```
```  1242
```
```  1243 lemma set_mset_Union_mset[simp]: "set_mset (\<Union># MM) = (\<Union>M \<in> set_mset MM. set_mset M)"
```
```  1244   by (induct MM) auto
```
```  1245
```
```  1246 lemma in_Union_mset_iff[iff]: "x \<in># \<Union># MM \<longleftrightarrow> (\<exists>M. M \<in># MM \<and> x \<in># M)"
```
```  1247   by (induct MM) auto
```
```  1248
```
```  1249 syntax
```
```  1250   "_msetsum_image" :: "pttrn \<Rightarrow> 'b set \<Rightarrow> 'a \<Rightarrow> 'a::comm_monoid_add"
```
```  1251       ("(3SUM _:#_. _)" [0, 51, 10] 10)
```
```  1252 syntax (xsymbols)
```
```  1253   "_msetsum_image" :: "pttrn \<Rightarrow> 'b set \<Rightarrow> 'a \<Rightarrow> 'a::comm_monoid_add"
```
```  1254       ("(3\<Sum>_\<in>#_. _)" [0, 51, 10] 10)
```
```  1255 translations
```
```  1256   "SUM i :# A. b" == "CONST msetsum (CONST image_mset (\<lambda>i. b) A)"
```
```  1257
```
```  1258 context comm_monoid_mult
```
```  1259 begin
```
```  1260
```
```  1261 sublocale msetprod: comm_monoid_mset times 1
```
```  1262   defines msetprod = msetprod.F ..
```
```  1263
```
```  1264 lemma msetprod_empty:
```
```  1265   "msetprod {#} = 1"
```
```  1266   by (fact msetprod.empty)
```
```  1267
```
```  1268 lemma msetprod_singleton:
```
```  1269   "msetprod {#x#} = x"
```
```  1270   by (fact msetprod.singleton)
```
```  1271
```
```  1272 lemma msetprod_Un:
```
```  1273   "msetprod (A + B) = msetprod A * msetprod B"
```
```  1274   by (fact msetprod.union)
```
```  1275
```
```  1276 lemma msetprod_replicate_mset [simp]:
```
```  1277   "msetprod (replicate_mset n a) = a ^ n"
```
```  1278   by (induct n) (simp_all add: ac_simps)
```
```  1279
```
```  1280 lemma setprod_unfold_msetprod:
```
```  1281   "setprod f A = msetprod (image_mset f (mset_set A))"
```
```  1282   by (cases "finite A") (induct A rule: finite_induct, simp_all)
```
```  1283
```
```  1284 lemma msetprod_multiplicity:
```
```  1285   "msetprod M = setprod (\<lambda>x. x ^ count M x) (set_mset M)"
```
```  1286   by (simp add: fold_mset_def setprod.eq_fold msetprod.eq_fold funpow_times_power comp_def)
```
```  1287
```
```  1288 end
```
```  1289
```
```  1290 syntax
```
```  1291   "_msetprod_image" :: "pttrn \<Rightarrow> 'b set \<Rightarrow> 'a \<Rightarrow> 'a::comm_monoid_mult"
```
```  1292       ("(3PROD _:#_. _)" [0, 51, 10] 10)
```
```  1293 syntax (xsymbols)
```
```  1294   "_msetprod_image" :: "pttrn \<Rightarrow> 'b set \<Rightarrow> 'a \<Rightarrow> 'a::comm_monoid_mult"
```
```  1295       ("(3\<Prod>_\<in>#_. _)" [0, 51, 10] 10)
```
```  1296 translations
```
```  1297   "PROD i :# A. b" == "CONST msetprod (CONST image_mset (\<lambda>i. b) A)"
```
```  1298
```
```  1299 lemma (in comm_semiring_1) dvd_msetprod:
```
```  1300   assumes "x \<in># A"
```
```  1301   shows "x dvd msetprod A"
```
```  1302 proof -
```
```  1303   from assms have "A = (A - {#x#}) + {#x#}" by simp
```
```  1304   then obtain B where "A = B + {#x#}" ..
```
```  1305   then show ?thesis by simp
```
```  1306 qed
```
```  1307
```
```  1308
```
```  1309 subsection \<open>Alternative representations\<close>
```
```  1310
```
```  1311 subsubsection \<open>Lists\<close>
```
```  1312
```
```  1313 context linorder
```
```  1314 begin
```
```  1315
```
```  1316 lemma mset_insort [simp]:
```
```  1317   "mset (insort_key k x xs) = {#x#} + mset xs"
```
```  1318   by (induct xs) (simp_all add: ac_simps)
```
```  1319
```
```  1320 lemma mset_sort [simp]:
```
```  1321   "mset (sort_key k xs) = mset xs"
```
```  1322   by (induct xs) (simp_all add: ac_simps)
```
```  1323
```
```  1324 text \<open>
```
```  1325   This lemma shows which properties suffice to show that a function
```
```  1326   \<open>f\<close> with \<open>f xs = ys\<close> behaves like sort.
```
```  1327 \<close>
```
```  1328
```
```  1329 lemma properties_for_sort_key:
```
```  1330   assumes "mset ys = mset xs"
```
```  1331     and "\<And>k. k \<in> set ys \<Longrightarrow> filter (\<lambda>x. f k = f x) ys = filter (\<lambda>x. f k = f x) xs"
```
```  1332     and "sorted (map f ys)"
```
```  1333   shows "sort_key f xs = ys"
```
```  1334   using assms
```
```  1335 proof (induct xs arbitrary: ys)
```
```  1336   case Nil then show ?case by simp
```
```  1337 next
```
```  1338   case (Cons x xs)
```
```  1339   from Cons.prems(2) have
```
```  1340     "\<forall>k \<in> set ys. filter (\<lambda>x. f k = f x) (remove1 x ys) = filter (\<lambda>x. f k = f x) xs"
```
```  1341     by (simp add: filter_remove1)
```
```  1342   with Cons.prems have "sort_key f xs = remove1 x ys"
```
```  1343     by (auto intro!: Cons.hyps simp add: sorted_map_remove1)
```
```  1344   moreover from Cons.prems have "x \<in> set ys"
```
```  1345     by (auto simp add: mem_set_multiset_eq intro!: ccontr)
```
```  1346   ultimately show ?case using Cons.prems by (simp add: insort_key_remove1)
```
```  1347 qed
```
```  1348
```
```  1349 lemma properties_for_sort:
```
```  1350   assumes multiset: "mset ys = mset xs"
```
```  1351     and "sorted ys"
```
```  1352   shows "sort xs = ys"
```
```  1353 proof (rule properties_for_sort_key)
```
```  1354   from multiset show "mset ys = mset xs" .
```
```  1355   from \<open>sorted ys\<close> show "sorted (map (\<lambda>x. x) ys)" by simp
```
```  1356   from multiset have "length (filter (\<lambda>y. k = y) ys) = length (filter (\<lambda>x. k = x) xs)" for k
```
```  1357     by (rule mset_eq_length_filter)
```
```  1358   then have "replicate (length (filter (\<lambda>y. k = y) ys)) k =
```
```  1359     replicate (length (filter (\<lambda>x. k = x) xs)) k" for k
```
```  1360     by simp
```
```  1361   then show "k \<in> set ys \<Longrightarrow> filter (\<lambda>y. k = y) ys = filter (\<lambda>x. k = x) xs" for k
```
```  1362     by (simp add: replicate_length_filter)
```
```  1363 qed
```
```  1364
```
```  1365 lemma sort_key_inj_key_eq:
```
```  1366   assumes mset_equal: "mset xs = mset ys"
```
```  1367     and "inj_on f (set xs)"
```
```  1368     and "sorted (map f ys)"
```
```  1369   shows "sort_key f xs = ys"
```
```  1370 proof (rule properties_for_sort_key)
```
```  1371   from mset_equal
```
```  1372   show "mset ys = mset xs" by simp
```
```  1373   from \<open>sorted (map f ys)\<close>
```
```  1374   show "sorted (map f ys)" .
```
```  1375   show "[x\<leftarrow>ys . f k = f x] = [x\<leftarrow>xs . f k = f x]" if "k \<in> set ys" for k
```
```  1376   proof -
```
```  1377     from mset_equal
```
```  1378     have set_equal: "set xs = set ys" by (rule mset_eq_setD)
```
```  1379     with that have "insert k (set ys) = set ys" by auto
```
```  1380     with \<open>inj_on f (set xs)\<close> have inj: "inj_on f (insert k (set ys))"
```
```  1381       by (simp add: set_equal)
```
```  1382     from inj have "[x\<leftarrow>ys . f k = f x] = filter (HOL.eq k) ys"
```
```  1383       by (auto intro!: inj_on_filter_key_eq)
```
```  1384     also have "\<dots> = replicate (count (mset ys) k) k"
```
```  1385       by (simp add: replicate_count_mset_eq_filter_eq)
```
```  1386     also have "\<dots> = replicate (count (mset xs) k) k"
```
```  1387       using mset_equal by simp
```
```  1388     also have "\<dots> = filter (HOL.eq k) xs"
```
```  1389       by (simp add: replicate_count_mset_eq_filter_eq)
```
```  1390     also have "\<dots> = [x\<leftarrow>xs . f k = f x]"
```
```  1391       using inj by (auto intro!: inj_on_filter_key_eq [symmetric] simp add: set_equal)
```
```  1392     finally show ?thesis .
```
```  1393   qed
```
```  1394 qed
```
```  1395
```
```  1396 lemma sort_key_eq_sort_key:
```
```  1397   assumes "mset xs = mset ys"
```
```  1398     and "inj_on f (set xs)"
```
```  1399   shows "sort_key f xs = sort_key f ys"
```
```  1400   by (rule sort_key_inj_key_eq) (simp_all add: assms)
```
```  1401
```
```  1402 lemma sort_key_by_quicksort:
```
```  1403   "sort_key f xs = sort_key f [x\<leftarrow>xs. f x < f (xs ! (length xs div 2))]
```
```  1404     @ [x\<leftarrow>xs. f x = f (xs ! (length xs div 2))]
```
```  1405     @ sort_key f [x\<leftarrow>xs. f x > f (xs ! (length xs div 2))]" (is "sort_key f ?lhs = ?rhs")
```
```  1406 proof (rule properties_for_sort_key)
```
```  1407   show "mset ?rhs = mset ?lhs"
```
```  1408     by (rule multiset_eqI) (auto simp add: mset_filter)
```
```  1409   show "sorted (map f ?rhs)"
```
```  1410     by (auto simp add: sorted_append intro: sorted_map_same)
```
```  1411 next
```
```  1412   fix l
```
```  1413   assume "l \<in> set ?rhs"
```
```  1414   let ?pivot = "f (xs ! (length xs div 2))"
```
```  1415   have *: "\<And>x. f l = f x \<longleftrightarrow> f x = f l" by auto
```
```  1416   have "[x \<leftarrow> sort_key f xs . f x = f l] = [x \<leftarrow> xs. f x = f l]"
```
```  1417     unfolding filter_sort by (rule properties_for_sort_key) (auto intro: sorted_map_same)
```
```  1418   with * have **: "[x \<leftarrow> sort_key f xs . f l = f x] = [x \<leftarrow> xs. f l = f x]" by simp
```
```  1419   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
```
```  1420   then have "\<And>P. [x \<leftarrow> sort_key f xs . P (f x) ?pivot \<and> f l = f x] =
```
```  1421     [x \<leftarrow> sort_key f xs. P (f l) ?pivot \<and> f l = f x]" by simp
```
```  1422   note *** = this [of "op <"] this [of "op >"] this [of "op ="]
```
```  1423   show "[x \<leftarrow> ?rhs. f l = f x] = [x \<leftarrow> ?lhs. f l = f x]"
```
```  1424   proof (cases "f l" ?pivot rule: linorder_cases)
```
```  1425     case less
```
```  1426     then have "f l \<noteq> ?pivot" and "\<not> f l > ?pivot" by auto
```
```  1427     with less show ?thesis
```
```  1428       by (simp add: filter_sort [symmetric] ** ***)
```
```  1429   next
```
```  1430     case equal then show ?thesis
```
```  1431       by (simp add: * less_le)
```
```  1432   next
```
```  1433     case greater
```
```  1434     then have "f l \<noteq> ?pivot" and "\<not> f l < ?pivot" by auto
```
```  1435     with greater show ?thesis
```
```  1436       by (simp add: filter_sort [symmetric] ** ***)
```
```  1437   qed
```
```  1438 qed
```
```  1439
```
```  1440 lemma sort_by_quicksort:
```
```  1441   "sort xs = sort [x\<leftarrow>xs. x < xs ! (length xs div 2)]
```
```  1442     @ [x\<leftarrow>xs. x = xs ! (length xs div 2)]
```
```  1443     @ sort [x\<leftarrow>xs. x > xs ! (length xs div 2)]" (is "sort ?lhs = ?rhs")
```
```  1444   using sort_key_by_quicksort [of "\<lambda>x. x", symmetric] by simp
```
```  1445
```
```  1446 text \<open>A stable parametrized quicksort\<close>
```
```  1447
```
```  1448 definition part :: "('b \<Rightarrow> 'a) \<Rightarrow> 'a \<Rightarrow> 'b list \<Rightarrow> 'b list \<times> 'b list \<times> 'b list" where
```
```  1449   "part f pivot xs = ([x \<leftarrow> xs. f x < pivot], [x \<leftarrow> xs. f x = pivot], [x \<leftarrow> xs. pivot < f x])"
```
```  1450
```
```  1451 lemma part_code [code]:
```
```  1452   "part f pivot [] = ([], [], [])"
```
```  1453   "part f pivot (x # xs) = (let (lts, eqs, gts) = part f pivot xs; x' = f x in
```
```  1454      if x' < pivot then (x # lts, eqs, gts)
```
```  1455      else if x' > pivot then (lts, eqs, x # gts)
```
```  1456      else (lts, x # eqs, gts))"
```
```  1457   by (auto simp add: part_def Let_def split_def)
```
```  1458
```
```  1459 lemma sort_key_by_quicksort_code [code]:
```
```  1460   "sort_key f xs =
```
```  1461     (case xs of
```
```  1462       [] \<Rightarrow> []
```
```  1463     | [x] \<Rightarrow> xs
```
```  1464     | [x, y] \<Rightarrow> (if f x \<le> f y then xs else [y, x])
```
```  1465     | _ \<Rightarrow>
```
```  1466         let (lts, eqs, gts) = part f (f (xs ! (length xs div 2))) xs
```
```  1467         in sort_key f lts @ eqs @ sort_key f gts)"
```
```  1468 proof (cases xs)
```
```  1469   case Nil then show ?thesis by simp
```
```  1470 next
```
```  1471   case (Cons _ ys) note hyps = Cons show ?thesis
```
```  1472   proof (cases ys)
```
```  1473     case Nil with hyps show ?thesis by simp
```
```  1474   next
```
```  1475     case (Cons _ zs) note hyps = hyps Cons show ?thesis
```
```  1476     proof (cases zs)
```
```  1477       case Nil with hyps show ?thesis by auto
```
```  1478     next
```
```  1479       case Cons
```
```  1480       from sort_key_by_quicksort [of f xs]
```
```  1481       have "sort_key f xs = (let (lts, eqs, gts) = part f (f (xs ! (length xs div 2))) xs
```
```  1482         in sort_key f lts @ eqs @ sort_key f gts)"
```
```  1483       by (simp only: split_def Let_def part_def fst_conv snd_conv)
```
```  1484       with hyps Cons show ?thesis by (simp only: list.cases)
```
```  1485     qed
```
```  1486   qed
```
```  1487 qed
```
```  1488
```
```  1489 end
```
```  1490
```
```  1491 hide_const (open) part
```
```  1492
```
```  1493 lemma mset_remdups_le: "mset (remdups xs) \<le># mset xs"
```
```  1494   by (induct xs) (auto intro: subset_mset.order_trans)
```
```  1495
```
```  1496 lemma mset_update:
```
```  1497   "i < length ls \<Longrightarrow> mset (ls[i := v]) = mset ls - {#ls ! i#} + {#v#}"
```
```  1498 proof (induct ls arbitrary: i)
```
```  1499   case Nil then show ?case by simp
```
```  1500 next
```
```  1501   case (Cons x xs)
```
```  1502   show ?case
```
```  1503   proof (cases i)
```
```  1504     case 0 then show ?thesis by simp
```
```  1505   next
```
```  1506     case (Suc i')
```
```  1507     with Cons show ?thesis
```
```  1508       apply simp
```
```  1509       apply (subst add.assoc)
```
```  1510       apply (subst add.commute [of "{#v#}" "{#x#}"])
```
```  1511       apply (subst add.assoc [symmetric])
```
```  1512       apply simp
```
```  1513       apply (rule mset_le_multiset_union_diff_commute)
```
```  1514       apply (simp add: mset_le_single nth_mem_mset)
```
```  1515       done
```
```  1516   qed
```
```  1517 qed
```
```  1518
```
```  1519 lemma mset_swap:
```
```  1520   "i < length ls \<Longrightarrow> j < length ls \<Longrightarrow>
```
```  1521     mset (ls[j := ls ! i, i := ls ! j]) = mset ls"
```
```  1522   by (cases "i = j") (simp_all add: mset_update nth_mem_mset)
```
```  1523
```
```  1524
```
```  1525 subsection \<open>The multiset order\<close>
```
```  1526
```
```  1527 subsubsection \<open>Well-foundedness\<close>
```
```  1528
```
```  1529 definition mult1 :: "('a \<times> 'a) set \<Rightarrow> ('a multiset \<times> 'a multiset) set" where
```
```  1530   "mult1 r = {(N, M). \<exists>a M0 K. M = M0 + {#a#} \<and> N = M0 + K \<and>
```
```  1531       (\<forall>b. b \<in># K \<longrightarrow> (b, a) \<in> r)}"
```
```  1532
```
```  1533 definition mult :: "('a \<times> 'a) set \<Rightarrow> ('a multiset \<times> 'a multiset) set" where
```
```  1534   "mult r = (mult1 r)\<^sup>+"
```
```  1535
```
```  1536 lemma not_less_empty [iff]: "(M, {#}) \<notin> mult1 r"
```
```  1537 by (simp add: mult1_def)
```
```  1538
```
```  1539 lemma less_add:
```
```  1540   assumes mult1: "(N, M0 + {#a#}) \<in> mult1 r"
```
```  1541   shows
```
```  1542     "(\<exists>M. (M, M0) \<in> mult1 r \<and> N = M + {#a#}) \<or>
```
```  1543      (\<exists>K. (\<forall>b. b \<in># K \<longrightarrow> (b, a) \<in> r) \<and> N = M0 + K)"
```
```  1544 proof -
```
```  1545   let ?r = "\<lambda>K a. \<forall>b. b \<in># K \<longrightarrow> (b, a) \<in> r"
```
```  1546   let ?R = "\<lambda>N M. \<exists>a M0 K. M = M0 + {#a#} \<and> N = M0 + K \<and> ?r K a"
```
```  1547   obtain a' M0' K where M0: "M0 + {#a#} = M0' + {#a'#}"
```
```  1548     and N: "N = M0' + K"
```
```  1549     and r: "?r K a'"
```
```  1550     using mult1 unfolding mult1_def by auto
```
```  1551   show ?thesis (is "?case1 \<or> ?case2")
```
```  1552   proof -
```
```  1553     from M0 consider "M0 = M0'" "a = a'"
```
```  1554       | K' where "M0 = K' + {#a'#}" "M0' = K' + {#a#}"
```
```  1555       by atomize_elim (simp only: add_eq_conv_ex)
```
```  1556     then show ?thesis
```
```  1557     proof cases
```
```  1558       case 1
```
```  1559       with N r have "?r K a \<and> N = M0 + K" by simp
```
```  1560       then have ?case2 ..
```
```  1561       then show ?thesis ..
```
```  1562     next
```
```  1563       case 2
```
```  1564       from N 2(2) have n: "N = K' + K + {#a#}" by (simp add: ac_simps)
```
```  1565       with r 2(1) have "?R (K' + K) M0" by blast
```
```  1566       with n have ?case1 by (simp add: mult1_def)
```
```  1567       then show ?thesis ..
```
```  1568     qed
```
```  1569   qed
```
```  1570 qed
```
```  1571
```
```  1572 lemma all_accessible:
```
```  1573   assumes "wf r"
```
```  1574   shows "\<forall>M. M \<in> Wellfounded.acc (mult1 r)"
```
```  1575 proof
```
```  1576   let ?R = "mult1 r"
```
```  1577   let ?W = "Wellfounded.acc ?R"
```
```  1578   {
```
```  1579     fix M M0 a
```
```  1580     assume M0: "M0 \<in> ?W"
```
```  1581       and wf_hyp: "\<And>b. (b, a) \<in> r \<Longrightarrow> (\<forall>M \<in> ?W. M + {#b#} \<in> ?W)"
```
```  1582       and acc_hyp: "\<forall>M. (M, M0) \<in> ?R \<longrightarrow> M + {#a#} \<in> ?W"
```
```  1583     have "M0 + {#a#} \<in> ?W"
```
```  1584     proof (rule accI [of "M0 + {#a#}"])
```
```  1585       fix N
```
```  1586       assume "(N, M0 + {#a#}) \<in> ?R"
```
```  1587       then consider M where "(M, M0) \<in> ?R" "N = M + {#a#}"
```
```  1588         | K where "\<forall>b. b \<in># K \<longrightarrow> (b, a) \<in> r" "N = M0 + K"
```
```  1589         by atomize_elim (rule less_add)
```
```  1590       then show "N \<in> ?W"
```
```  1591       proof cases
```
```  1592         case 1
```
```  1593         from acc_hyp have "(M, M0) \<in> ?R \<longrightarrow> M + {#a#} \<in> ?W" ..
```
```  1594         from this and \<open>(M, M0) \<in> ?R\<close> have "M + {#a#} \<in> ?W" ..
```
```  1595         then show "N \<in> ?W" by (simp only: \<open>N = M + {#a#}\<close>)
```
```  1596       next
```
```  1597         case 2
```
```  1598         from this(1) have "M0 + K \<in> ?W"
```
```  1599         proof (induct K)
```
```  1600           case empty
```
```  1601           from M0 show "M0 + {#} \<in> ?W" by simp
```
```  1602         next
```
```  1603           case (add K x)
```
```  1604           from add.prems have "(x, a) \<in> r" by simp
```
```  1605           with wf_hyp have "\<forall>M \<in> ?W. M + {#x#} \<in> ?W" by blast
```
```  1606           moreover from add have "M0 + K \<in> ?W" by simp
```
```  1607           ultimately have "(M0 + K) + {#x#} \<in> ?W" ..
```
```  1608           then show "M0 + (K + {#x#}) \<in> ?W" by (simp only: add.assoc)
```
```  1609         qed
```
```  1610         then show "N \<in> ?W" by (simp only: 2(2))
```
```  1611       qed
```
```  1612     qed
```
```  1613   } note tedious_reasoning = this
```
```  1614
```
```  1615   show "M \<in> ?W" for M
```
```  1616   proof (induct M)
```
```  1617     show "{#} \<in> ?W"
```
```  1618     proof (rule accI)
```
```  1619       fix b assume "(b, {#}) \<in> ?R"
```
```  1620       with not_less_empty show "b \<in> ?W" by contradiction
```
```  1621     qed
```
```  1622
```
```  1623     fix M a assume "M \<in> ?W"
```
```  1624     from \<open>wf r\<close> have "\<forall>M \<in> ?W. M + {#a#} \<in> ?W"
```
```  1625     proof induct
```
```  1626       fix a
```
```  1627       assume r: "\<And>b. (b, a) \<in> r \<Longrightarrow> (\<forall>M \<in> ?W. M + {#b#} \<in> ?W)"
```
```  1628       show "\<forall>M \<in> ?W. M + {#a#} \<in> ?W"
```
```  1629       proof
```
```  1630         fix M assume "M \<in> ?W"
```
```  1631         then show "M + {#a#} \<in> ?W"
```
```  1632           by (rule acc_induct) (rule tedious_reasoning [OF _ r])
```
```  1633       qed
```
```  1634     qed
```
```  1635     from this and \<open>M \<in> ?W\<close> show "M + {#a#} \<in> ?W" ..
```
```  1636   qed
```
```  1637 qed
```
```  1638
```
```  1639 theorem wf_mult1: "wf r \<Longrightarrow> wf (mult1 r)"
```
```  1640 by (rule acc_wfI) (rule all_accessible)
```
```  1641
```
```  1642 theorem wf_mult: "wf r \<Longrightarrow> wf (mult r)"
```
```  1643 unfolding mult_def by (rule wf_trancl) (rule wf_mult1)
```
```  1644
```
```  1645
```
```  1646 subsubsection \<open>Closure-free presentation\<close>
```
```  1647
```
```  1648 text \<open>One direction.\<close>
```
```  1649
```
```  1650 lemma mult_implies_one_step:
```
```  1651   "trans r \<Longrightarrow> (M, N) \<in> mult r \<Longrightarrow>
```
```  1652     \<exists>I J K. N = I + J \<and> M = I + K \<and> J \<noteq> {#} \<and>
```
```  1653     (\<forall>k \<in> set_mset K. \<exists>j \<in> set_mset J. (k, j) \<in> r)"
```
```  1654 apply (unfold mult_def mult1_def set_mset_def)
```
```  1655 apply (erule converse_trancl_induct, clarify)
```
```  1656  apply (rule_tac x = M0 in exI, simp, clarify)
```
```  1657 apply (case_tac "a \<in># K")
```
```  1658  apply (rule_tac x = I in exI)
```
```  1659  apply (simp (no_asm))
```
```  1660  apply (rule_tac x = "(K - {#a#}) + Ka" in exI)
```
```  1661  apply (simp (no_asm_simp) add: add.assoc [symmetric])
```
```  1662  apply (drule_tac f = "\<lambda>M. M - {#a#}" and x="S + T" for S T in arg_cong)
```
```  1663  apply (simp add: diff_union_single_conv)
```
```  1664  apply (simp (no_asm_use) add: trans_def)
```
```  1665  apply blast
```
```  1666 apply (subgoal_tac "a \<in># I")
```
```  1667  apply (rule_tac x = "I - {#a#}" in exI)
```
```  1668  apply (rule_tac x = "J + {#a#}" in exI)
```
```  1669  apply (rule_tac x = "K + Ka" in exI)
```
```  1670  apply (rule conjI)
```
```  1671   apply (simp add: multiset_eq_iff split: nat_diff_split)
```
```  1672  apply (rule conjI)
```
```  1673   apply (drule_tac f = "\<lambda>M. M - {#a#}" and x="S + T" for S T in arg_cong, simp)
```
```  1674   apply (simp add: multiset_eq_iff split: nat_diff_split)
```
```  1675  apply (simp (no_asm_use) add: trans_def)
```
```  1676  apply blast
```
```  1677 apply (subgoal_tac "a \<in># (M0 + {#a#})")
```
```  1678  apply simp
```
```  1679 apply (simp (no_asm))
```
```  1680 done
```
```  1681
```
```  1682 lemma one_step_implies_mult_aux:
```
```  1683   "\<forall>I J K. size J = n \<and> J \<noteq> {#} \<and> (\<forall>k \<in> set_mset K. \<exists>j \<in> set_mset J. (k, j) \<in> r)
```
```  1684     \<longrightarrow> (I + K, I + J) \<in> mult r"
```
```  1685 apply (induct n)
```
```  1686  apply auto
```
```  1687 apply (frule size_eq_Suc_imp_eq_union, clarify)
```
```  1688 apply (rename_tac "J'", simp)
```
```  1689 apply (erule notE, auto)
```
```  1690 apply (case_tac "J' = {#}")
```
```  1691  apply (simp add: mult_def)
```
```  1692  apply (rule r_into_trancl)
```
```  1693  apply (simp add: mult1_def set_mset_def, blast)
```
```  1694 txt \<open>Now we know @{term "J' \<noteq> {#}"}.\<close>
```
```  1695 apply (cut_tac M = K and P = "\<lambda>x. (x, a) \<in> r" in multiset_partition)
```
```  1696 apply (erule_tac P = "\<forall>k \<in> set_mset K. P k" for P in rev_mp)
```
```  1697 apply (erule ssubst)
```
```  1698 apply (simp add: Ball_def, auto)
```
```  1699 apply (subgoal_tac
```
```  1700   "((I + {# x \<in># K. (x, a) \<in> r #}) + {# x \<in># K. (x, a) \<notin> r #},
```
```  1701     (I + {# x \<in># K. (x, a) \<in> r #}) + J') \<in> mult r")
```
```  1702  prefer 2
```
```  1703  apply force
```
```  1704 apply (simp (no_asm_use) add: add.assoc [symmetric] mult_def)
```
```  1705 apply (erule trancl_trans)
```
```  1706 apply (rule r_into_trancl)
```
```  1707 apply (simp add: mult1_def set_mset_def)
```
```  1708 apply (rule_tac x = a in exI)
```
```  1709 apply (rule_tac x = "I + J'" in exI)
```
```  1710 apply (simp add: ac_simps)
```
```  1711 done
```
```  1712
```
```  1713 lemma one_step_implies_mult:
```
```  1714   "trans r \<Longrightarrow> J \<noteq> {#} \<Longrightarrow> \<forall>k \<in> set_mset K. \<exists>j \<in> set_mset J. (k, j) \<in> r
```
```  1715     \<Longrightarrow> (I + K, I + J) \<in> mult r"
```
```  1716 using one_step_implies_mult_aux by blast
```
```  1717
```
```  1718
```
```  1719 subsubsection \<open>Partial-order properties\<close>
```
```  1720
```
```  1721 definition less_multiset :: "'a::order multiset \<Rightarrow> 'a multiset \<Rightarrow> bool" (infix "#<#" 50) where
```
```  1722   "M' #<# M \<longleftrightarrow> (M', M) \<in> mult {(x', x). x' < x}"
```
```  1723
```
```  1724 definition le_multiset :: "'a::order multiset \<Rightarrow> 'a multiset \<Rightarrow> bool" (infix "#<=#" 50) where
```
```  1725   "M' #<=# M \<longleftrightarrow> M' #<# M \<or> M' = M"
```
```  1726
```
```  1727 notation (xsymbols) less_multiset (infix "#\<subset>#" 50)
```
```  1728 notation (xsymbols) le_multiset (infix "#\<subseteq>#" 50)
```
```  1729
```
```  1730 interpretation multiset_order: order le_multiset less_multiset
```
```  1731 proof -
```
```  1732   have irrefl: "\<not> M #\<subset># M" for M :: "'a multiset"
```
```  1733   proof
```
```  1734     assume "M #\<subset># M"
```
```  1735     then have MM: "(M, M) \<in> mult {(x, y). x < y}" by (simp add: less_multiset_def)
```
```  1736     have "trans {(x'::'a, x). x' < x}"
```
```  1737       by (rule transI) simp
```
```  1738     moreover note MM
```
```  1739     ultimately have "\<exists>I J K. M = I + J \<and> M = I + K
```
```  1740       \<and> J \<noteq> {#} \<and> (\<forall>k\<in>set_mset K. \<exists>j\<in>set_mset J. (k, j) \<in> {(x, y). x < y})"
```
```  1741       by (rule mult_implies_one_step)
```
```  1742     then obtain I J K where "M = I + J" and "M = I + K"
```
```  1743       and "J \<noteq> {#}" and "(\<forall>k\<in>set_mset K. \<exists>j\<in>set_mset J. (k, j) \<in> {(x, y). x < y})" by blast
```
```  1744     then have *: "K \<noteq> {#}" and **: "\<forall>k\<in>set_mset K. \<exists>j\<in>set_mset K. k < j" by auto
```
```  1745     have "finite (set_mset K)" by simp
```
```  1746     moreover note **
```
```  1747     ultimately have "set_mset K = {}"
```
```  1748       by (induct rule: finite_induct) (auto intro: order_less_trans)
```
```  1749     with * show False by simp
```
```  1750   qed
```
```  1751   have trans: "K #\<subset># M \<Longrightarrow> M #\<subset># N \<Longrightarrow> K #\<subset># N" for K M N :: "'a multiset"
```
```  1752     unfolding less_multiset_def mult_def by (blast intro: trancl_trans)
```
```  1753   show "class.order (le_multiset :: 'a multiset \<Rightarrow> _) less_multiset"
```
```  1754     by standard (auto simp add: le_multiset_def irrefl dest: trans)
```
```  1755 qed
```
```  1756
```
```  1757 lemma mult_less_irrefl [elim!]:
```
```  1758   fixes M :: "'a::order multiset"
```
```  1759   shows "M #\<subset># M \<Longrightarrow> R"
```
```  1760   by simp
```
```  1761
```
```  1762
```
```  1763 subsubsection \<open>Monotonicity of multiset union\<close>
```
```  1764
```
```  1765 lemma mult1_union: "(B, D) \<in> mult1 r \<Longrightarrow> (C + B, C + D) \<in> mult1 r"
```
```  1766 apply (unfold mult1_def)
```
```  1767 apply auto
```
```  1768 apply (rule_tac x = a in exI)
```
```  1769 apply (rule_tac x = "C + M0" in exI)
```
```  1770 apply (simp add: add.assoc)
```
```  1771 done
```
```  1772
```
```  1773 lemma union_less_mono2: "B #\<subset># D \<Longrightarrow> C + B #\<subset># C + (D::'a::order multiset)"
```
```  1774 apply (unfold less_multiset_def mult_def)
```
```  1775 apply (erule trancl_induct)
```
```  1776  apply (blast intro: mult1_union)
```
```  1777 apply (blast intro: mult1_union trancl_trans)
```
```  1778 done
```
```  1779
```
```  1780 lemma union_less_mono1: "B #\<subset># D \<Longrightarrow> B + C #\<subset># D + (C::'a::order multiset)"
```
```  1781 apply (subst add.commute [of B C])
```
```  1782 apply (subst add.commute [of D C])
```
```  1783 apply (erule union_less_mono2)
```
```  1784 done
```
```  1785
```
```  1786 lemma union_less_mono:
```
```  1787   fixes A B C D :: "'a::order multiset"
```
```  1788   shows "A #\<subset># C \<Longrightarrow> B #\<subset># D \<Longrightarrow> A + B #\<subset># C + D"
```
```  1789   by (blast intro!: union_less_mono1 union_less_mono2 multiset_order.less_trans)
```
```  1790
```
```  1791 interpretation multiset_order: ordered_ab_semigroup_add plus le_multiset less_multiset
```
```  1792   by standard (auto simp add: le_multiset_def intro: union_less_mono2)
```
```  1793
```
```  1794
```
```  1795 subsubsection \<open>Termination proofs with multiset orders\<close>
```
```  1796
```
```  1797 lemma multi_member_skip: "x \<in># XS \<Longrightarrow> x \<in># {# y #} + XS"
```
```  1798   and multi_member_this: "x \<in># {# x #} + XS"
```
```  1799   and multi_member_last: "x \<in># {# x #}"
```
```  1800   by auto
```
```  1801
```
```  1802 definition "ms_strict = mult pair_less"
```
```  1803 definition "ms_weak = ms_strict \<union> Id"
```
```  1804
```
```  1805 lemma ms_reduction_pair: "reduction_pair (ms_strict, ms_weak)"
```
```  1806 unfolding reduction_pair_def ms_strict_def ms_weak_def pair_less_def
```
```  1807 by (auto intro: wf_mult1 wf_trancl simp: mult_def)
```
```  1808
```
```  1809 lemma smsI:
```
```  1810   "(set_mset A, set_mset B) \<in> max_strict \<Longrightarrow> (Z + A, Z + B) \<in> ms_strict"
```
```  1811   unfolding ms_strict_def
```
```  1812 by (rule one_step_implies_mult) (auto simp add: max_strict_def pair_less_def elim!:max_ext.cases)
```
```  1813
```
```  1814 lemma wmsI:
```
```  1815   "(set_mset A, set_mset B) \<in> max_strict \<or> A = {#} \<and> B = {#}
```
```  1816   \<Longrightarrow> (Z + A, Z + B) \<in> ms_weak"
```
```  1817 unfolding ms_weak_def ms_strict_def
```
```  1818 by (auto simp add: pair_less_def max_strict_def elim!:max_ext.cases intro: one_step_implies_mult)
```
```  1819
```
```  1820 inductive pw_leq
```
```  1821 where
```
```  1822   pw_leq_empty: "pw_leq {#} {#}"
```
```  1823 | pw_leq_step:  "\<lbrakk>(x,y) \<in> pair_leq; pw_leq X Y \<rbrakk> \<Longrightarrow> pw_leq ({#x#} + X) ({#y#} + Y)"
```
```  1824
```
```  1825 lemma pw_leq_lstep:
```
```  1826   "(x, y) \<in> pair_leq \<Longrightarrow> pw_leq {#x#} {#y#}"
```
```  1827 by (drule pw_leq_step) (rule pw_leq_empty, simp)
```
```  1828
```
```  1829 lemma pw_leq_split:
```
```  1830   assumes "pw_leq X Y"
```
```  1831   shows "\<exists>A B Z. X = A + Z \<and> Y = B + Z \<and> ((set_mset A, set_mset B) \<in> max_strict \<or> (B = {#} \<and> A = {#}))"
```
```  1832   using assms
```
```  1833 proof induct
```
```  1834   case pw_leq_empty thus ?case by auto
```
```  1835 next
```
```  1836   case (pw_leq_step x y X Y)
```
```  1837   then obtain A B Z where
```
```  1838     [simp]: "X = A + Z" "Y = B + Z"
```
```  1839       and 1[simp]: "(set_mset A, set_mset B) \<in> max_strict \<or> (B = {#} \<and> A = {#})"
```
```  1840     by auto
```
```  1841   from pw_leq_step consider "x = y" | "(x, y) \<in> pair_less"
```
```  1842     unfolding pair_leq_def by auto
```
```  1843   thus ?case
```
```  1844   proof cases
```
```  1845     case [simp]: 1
```
```  1846     have "{#x#} + X = A + ({#y#}+Z) \<and> {#y#} + Y = B + ({#y#}+Z) \<and>
```
```  1847       ((set_mset A, set_mset B) \<in> max_strict \<or> (B = {#} \<and> A = {#}))"
```
```  1848       by (auto simp: ac_simps)
```
```  1849     thus ?thesis by blast
```
```  1850   next
```
```  1851     case 2
```
```  1852     let ?A' = "{#x#} + A" and ?B' = "{#y#} + B"
```
```  1853     have "{#x#} + X = ?A' + Z"
```
```  1854       "{#y#} + Y = ?B' + Z"
```
```  1855       by (auto simp add: ac_simps)
```
```  1856     moreover have
```
```  1857       "(set_mset ?A', set_mset ?B') \<in> max_strict"
```
```  1858       using 1 2 unfolding max_strict_def
```
```  1859       by (auto elim!: max_ext.cases)
```
```  1860     ultimately show ?thesis by blast
```
```  1861   qed
```
```  1862 qed
```
```  1863
```
```  1864 lemma
```
```  1865   assumes pwleq: "pw_leq Z Z'"
```
```  1866   shows ms_strictI: "(set_mset A, set_mset B) \<in> max_strict \<Longrightarrow> (Z + A, Z' + B) \<in> ms_strict"
```
```  1867     and ms_weakI1:  "(set_mset A, set_mset B) \<in> max_strict \<Longrightarrow> (Z + A, Z' + B) \<in> ms_weak"
```
```  1868     and ms_weakI2:  "(Z + {#}, Z' + {#}) \<in> ms_weak"
```
```  1869 proof -
```
```  1870   from pw_leq_split[OF pwleq]
```
```  1871   obtain A' B' Z''
```
```  1872     where [simp]: "Z = A' + Z''" "Z' = B' + Z''"
```
```  1873     and mx_or_empty: "(set_mset A', set_mset B') \<in> max_strict \<or> (A' = {#} \<and> B' = {#})"
```
```  1874     by blast
```
```  1875   {
```
```  1876     assume max: "(set_mset A, set_mset B) \<in> max_strict"
```
```  1877     from mx_or_empty
```
```  1878     have "(Z'' + (A + A'), Z'' + (B + B')) \<in> ms_strict"
```
```  1879     proof
```
```  1880       assume max': "(set_mset A', set_mset B') \<in> max_strict"
```
```  1881       with max have "(set_mset (A + A'), set_mset (B + B')) \<in> max_strict"
```
```  1882         by (auto simp: max_strict_def intro: max_ext_additive)
```
```  1883       thus ?thesis by (rule smsI)
```
```  1884     next
```
```  1885       assume [simp]: "A' = {#} \<and> B' = {#}"
```
```  1886       show ?thesis by (rule smsI) (auto intro: max)
```
```  1887     qed
```
```  1888     thus "(Z + A, Z' + B) \<in> ms_strict" by (simp add: ac_simps)
```
```  1889     thus "(Z + A, Z' + B) \<in> ms_weak" by (simp add: ms_weak_def)
```
```  1890   }
```
```  1891   from mx_or_empty
```
```  1892   have "(Z'' + A', Z'' + B') \<in> ms_weak" by (rule wmsI)
```
```  1893   thus "(Z + {#}, Z' + {#}) \<in> ms_weak" by (simp add:ac_simps)
```
```  1894 qed
```
```  1895
```
```  1896 lemma empty_neutral: "{#} + x = x" "x + {#} = x"
```
```  1897 and nonempty_plus: "{# x #} + rs \<noteq> {#}"
```
```  1898 and nonempty_single: "{# x #} \<noteq> {#}"
```
```  1899 by auto
```
```  1900
```
```  1901 setup \<open>
```
```  1902   let
```
```  1903     fun msetT T = Type (@{type_name multiset}, [T]);
```
```  1904
```
```  1905     fun mk_mset T [] = Const (@{const_abbrev Mempty}, msetT T)
```
```  1906       | mk_mset T [x] = Const (@{const_name single}, T --> msetT T) \$ x
```
```  1907       | mk_mset T (x :: xs) =
```
```  1908             Const (@{const_name plus}, msetT T --> msetT T --> msetT T) \$
```
```  1909                   mk_mset T [x] \$ mk_mset T xs
```
```  1910
```
```  1911     fun mset_member_tac ctxt m i =
```
```  1912       if m <= 0 then
```
```  1913         resolve_tac ctxt @{thms multi_member_this} i ORELSE
```
```  1914         resolve_tac ctxt @{thms multi_member_last} i
```
```  1915       else
```
```  1916         resolve_tac ctxt @{thms multi_member_skip} i THEN mset_member_tac ctxt (m - 1) i
```
```  1917
```
```  1918     fun mset_nonempty_tac ctxt =
```
```  1919       resolve_tac ctxt @{thms nonempty_plus} ORELSE'
```
```  1920       resolve_tac ctxt @{thms nonempty_single}
```
```  1921
```
```  1922     fun regroup_munion_conv ctxt =
```
```  1923       Function_Lib.regroup_conv ctxt @{const_abbrev Mempty} @{const_name plus}
```
```  1924         (map (fn t => t RS eq_reflection) (@{thms ac_simps} @ @{thms empty_neutral}))
```
```  1925
```
```  1926     fun unfold_pwleq_tac ctxt i =
```
```  1927       (resolve_tac ctxt @{thms pw_leq_step} i THEN (fn st => unfold_pwleq_tac ctxt (i + 1) st))
```
```  1928         ORELSE (resolve_tac ctxt @{thms pw_leq_lstep} i)
```
```  1929         ORELSE (resolve_tac ctxt @{thms pw_leq_empty} i)
```
```  1930
```
```  1931     val set_mset_simps = [@{thm set_mset_empty}, @{thm set_mset_single}, @{thm set_mset_union},
```
```  1932                         @{thm Un_insert_left}, @{thm Un_empty_left}]
```
```  1933   in
```
```  1934     ScnpReconstruct.multiset_setup (ScnpReconstruct.Multiset
```
```  1935     {
```
```  1936       msetT=msetT, mk_mset=mk_mset, mset_regroup_conv=regroup_munion_conv,
```
```  1937       mset_member_tac=mset_member_tac, mset_nonempty_tac=mset_nonempty_tac,
```
```  1938       mset_pwleq_tac=unfold_pwleq_tac, set_of_simps=set_mset_simps,
```
```  1939       smsI'= @{thm ms_strictI}, wmsI2''= @{thm ms_weakI2}, wmsI1= @{thm ms_weakI1},
```
```  1940       reduction_pair = @{thm ms_reduction_pair}
```
```  1941     })
```
```  1942   end
```
```  1943 \<close>
```
```  1944
```
```  1945
```
```  1946 subsection \<open>Legacy theorem bindings\<close>
```
```  1947
```
```  1948 lemmas multi_count_eq = multiset_eq_iff [symmetric]
```
```  1949
```
```  1950 lemma union_commute: "M + N = N + (M::'a multiset)"
```
```  1951   by (fact add.commute)
```
```  1952
```
```  1953 lemma union_assoc: "(M + N) + K = M + (N + (K::'a multiset))"
```
```  1954   by (fact add.assoc)
```
```  1955
```
```  1956 lemma union_lcomm: "M + (N + K) = N + (M + (K::'a multiset))"
```
```  1957   by (fact add.left_commute)
```
```  1958
```
```  1959 lemmas union_ac = union_assoc union_commute union_lcomm
```
```  1960
```
```  1961 lemma union_right_cancel: "M + K = N + K \<longleftrightarrow> M = (N::'a multiset)"
```
```  1962   by (fact add_right_cancel)
```
```  1963
```
```  1964 lemma union_left_cancel: "K + M = K + N \<longleftrightarrow> M = (N::'a multiset)"
```
```  1965   by (fact add_left_cancel)
```
```  1966
```
```  1967 lemma multi_union_self_other_eq: "(A::'a multiset) + X = A + Y \<Longrightarrow> X = Y"
```
```  1968   by (fact add_left_imp_eq)
```
```  1969
```
```  1970 lemma mset_less_trans: "(M::'a multiset) <# K \<Longrightarrow> K <# N \<Longrightarrow> M <# N"
```
```  1971   by (fact subset_mset.less_trans)
```
```  1972
```
```  1973 lemma multiset_inter_commute: "A #\<inter> B = B #\<inter> A"
```
```  1974   by (fact subset_mset.inf.commute)
```
```  1975
```
```  1976 lemma multiset_inter_assoc: "A #\<inter> (B #\<inter> C) = A #\<inter> B #\<inter> C"
```
```  1977   by (fact subset_mset.inf.assoc [symmetric])
```
```  1978
```
```  1979 lemma multiset_inter_left_commute: "A #\<inter> (B #\<inter> C) = B #\<inter> (A #\<inter> C)"
```
```  1980   by (fact subset_mset.inf.left_commute)
```
```  1981
```
```  1982 lemmas multiset_inter_ac =
```
```  1983   multiset_inter_commute
```
```  1984   multiset_inter_assoc
```
```  1985   multiset_inter_left_commute
```
```  1986
```
```  1987 lemma mult_less_not_refl: "\<not> M #\<subset># (M::'a::order multiset)"
```
```  1988   by (fact multiset_order.less_irrefl)
```
```  1989
```
```  1990 lemma mult_less_trans: "K #\<subset># M \<Longrightarrow> M #\<subset># N \<Longrightarrow> K #\<subset># (N::'a::order multiset)"
```
```  1991   by (fact multiset_order.less_trans)
```
```  1992
```
```  1993 lemma mult_less_not_sym: "M #\<subset># N \<Longrightarrow> \<not> N #\<subset># (M::'a::order multiset)"
```
```  1994   by (fact multiset_order.less_not_sym)
```
```  1995
```
```  1996 lemma mult_less_asym: "M #\<subset># N \<Longrightarrow> (\<not> P \<Longrightarrow> N #\<subset># (M::'a::order multiset)) \<Longrightarrow> P"
```
```  1997   by (fact multiset_order.less_asym)
```
```  1998
```
```  1999 declaration \<open>
```
```  2000   let
```
```  2001     fun multiset_postproc _ maybe_name all_values (T as Type (_, [elem_T])) (Const _ \$ t') =
```
```  2002           let
```
```  2003             val (maybe_opt, ps) =
```
```  2004               Nitpick_Model.dest_plain_fun t'
```
```  2005               ||> op ~~
```
```  2006               ||> map (apsnd (snd o HOLogic.dest_number))
```
```  2007             fun elems_for t =
```
```  2008               (case AList.lookup (op =) ps t of
```
```  2009                 SOME n => replicate n t
```
```  2010               | NONE => [Const (maybe_name, elem_T --> elem_T) \$ t])
```
```  2011           in
```
```  2012             (case maps elems_for (all_values elem_T) @
```
```  2013                  (if maybe_opt then [Const (Nitpick_Model.unrep_mixfix (), elem_T)] else []) of
```
```  2014               [] => Const (@{const_name zero_class.zero}, T)
```
```  2015             | ts =>
```
```  2016                 foldl1 (fn (t1, t2) =>
```
```  2017                     Const (@{const_name plus_class.plus}, T --> T --> T) \$ t1 \$ t2)
```
```  2018                   (map (curry (op \$) (Const (@{const_name single}, elem_T --> T))) ts))
```
```  2019           end
```
```  2020       | multiset_postproc _ _ _ _ t = t
```
```  2021   in Nitpick_Model.register_term_postprocessor @{typ "'a multiset"} multiset_postproc end
```
```  2022 \<close>
```
```  2023
```
```  2024
```
```  2025 subsection \<open>Naive implementation using lists\<close>
```
```  2026
```
```  2027 code_datatype mset
```
```  2028
```
```  2029 lemma [code]: "{#} = mset []"
```
```  2030   by simp
```
```  2031
```
```  2032 lemma [code]: "{#x#} = mset [x]"
```
```  2033   by simp
```
```  2034
```
```  2035 lemma union_code [code]: "mset xs + mset ys = mset (xs @ ys)"
```
```  2036   by simp
```
```  2037
```
```  2038 lemma [code]: "image_mset f (mset xs) = mset (map f xs)"
```
```  2039   by (simp add: mset_map)
```
```  2040
```
```  2041 lemma [code]: "filter_mset f (mset xs) = mset (filter f xs)"
```
```  2042   by (simp add: mset_filter)
```
```  2043
```
```  2044 lemma [code]: "mset xs - mset ys = mset (fold remove1 ys xs)"
```
```  2045   by (rule sym, induct ys arbitrary: xs) (simp_all add: diff_add diff_right_commute)
```
```  2046
```
```  2047 lemma [code]:
```
```  2048   "mset xs #\<inter> mset ys =
```
```  2049     mset (snd (fold (\<lambda>x (ys, zs).
```
```  2050       if x \<in> set ys then (remove1 x ys, x # zs) else (ys, zs)) xs (ys, [])))"
```
```  2051 proof -
```
```  2052   have "\<And>zs. mset (snd (fold (\<lambda>x (ys, zs).
```
```  2053     if x \<in> set ys then (remove1 x ys, x # zs) else (ys, zs)) xs (ys, zs))) =
```
```  2054       (mset xs #\<inter> mset ys) + mset zs"
```
```  2055     by (induct xs arbitrary: ys)
```
```  2056       (auto simp add: mem_set_multiset_eq inter_add_right1 inter_add_right2 ac_simps)
```
```  2057   then show ?thesis by simp
```
```  2058 qed
```
```  2059
```
```  2060 lemma [code]:
```
```  2061   "mset xs #\<union> mset ys =
```
```  2062     mset (case_prod append (fold (\<lambda>x (ys, zs). (remove1 x ys, x # zs)) xs (ys, [])))"
```
```  2063 proof -
```
```  2064   have "\<And>zs. mset (case_prod append (fold (\<lambda>x (ys, zs). (remove1 x ys, x # zs)) xs (ys, zs))) =
```
```  2065       (mset xs #\<union> mset ys) + mset zs"
```
```  2066     by (induct xs arbitrary: ys) (simp_all add: multiset_eq_iff)
```
```  2067   then show ?thesis by simp
```
```  2068 qed
```
```  2069
```
```  2070 declare in_multiset_in_set [code_unfold]
```
```  2071
```
```  2072 lemma [code]: "count (mset xs) x = fold (\<lambda>y. if x = y then Suc else id) xs 0"
```
```  2073 proof -
```
```  2074   have "\<And>n. fold (\<lambda>y. if x = y then Suc else id) xs n = count (mset xs) x + n"
```
```  2075     by (induct xs) simp_all
```
```  2076   then show ?thesis by simp
```
```  2077 qed
```
```  2078
```
```  2079 declare set_mset_mset [code]
```
```  2080
```
```  2081 declare sorted_list_of_multiset_mset [code]
```
```  2082
```
```  2083 lemma [code]: \<comment> \<open>not very efficient, but representation-ignorant!\<close>
```
```  2084   "mset_set A = mset (sorted_list_of_set A)"
```
```  2085   apply (cases "finite A")
```
```  2086   apply simp_all
```
```  2087   apply (induct A rule: finite_induct)
```
```  2088   apply (simp_all add: add.commute)
```
```  2089   done
```
```  2090
```
```  2091 declare size_mset [code]
```
```  2092
```
```  2093 fun ms_lesseq_impl :: "'a list \<Rightarrow> 'a list \<Rightarrow> bool option" where
```
```  2094   "ms_lesseq_impl [] ys = Some (ys \<noteq> [])"
```
```  2095 | "ms_lesseq_impl (Cons x xs) ys = (case List.extract (op = x) ys of
```
```  2096      None \<Rightarrow> None
```
```  2097    | Some (ys1,_,ys2) \<Rightarrow> ms_lesseq_impl xs (ys1 @ ys2))"
```
```  2098
```
```  2099 lemma ms_lesseq_impl: "(ms_lesseq_impl xs ys = None \<longleftrightarrow> \<not> mset xs \<le># mset ys) \<and>
```
```  2100   (ms_lesseq_impl xs ys = Some True \<longleftrightarrow> mset xs <# mset ys) \<and>
```
```  2101   (ms_lesseq_impl xs ys = Some False \<longrightarrow> mset xs = mset ys)"
```
```  2102 proof (induct xs arbitrary: ys)
```
```  2103   case (Nil ys)
```
```  2104   show ?case by (auto simp: mset_less_empty_nonempty)
```
```  2105 next
```
```  2106   case (Cons x xs ys)
```
```  2107   show ?case
```
```  2108   proof (cases "List.extract (op = x) ys")
```
```  2109     case None
```
```  2110     hence x: "x \<notin> set ys" by (simp add: extract_None_iff)
```
```  2111     {
```
```  2112       assume "mset (x # xs) \<le># mset ys"
```
```  2113       from set_mset_mono[OF this] x have False by simp
```
```  2114     } note nle = this
```
```  2115     moreover
```
```  2116     {
```
```  2117       assume "mset (x # xs) <# mset ys"
```
```  2118       hence "mset (x # xs) \<le># mset ys" by auto
```
```  2119       from nle[OF this] have False .
```
```  2120     }
```
```  2121     ultimately show ?thesis using None by auto
```
```  2122   next
```
```  2123     case (Some res)
```
```  2124     obtain ys1 y ys2 where res: "res = (ys1,y,ys2)" by (cases res, auto)
```
```  2125     note Some = Some[unfolded res]
```
```  2126     from extract_SomeE[OF Some] have "ys = ys1 @ x # ys2" by simp
```
```  2127     hence id: "mset ys = mset (ys1 @ ys2) + {#x#}"
```
```  2128       by (auto simp: ac_simps)
```
```  2129     show ?thesis unfolding ms_lesseq_impl.simps
```
```  2130       unfolding Some option.simps split
```
```  2131       unfolding id
```
```  2132       using Cons[of "ys1 @ ys2"]
```
```  2133       unfolding subset_mset_def subseteq_mset_def by auto
```
```  2134   qed
```
```  2135 qed
```
```  2136
```
```  2137 lemma [code]: "mset xs \<le># mset ys \<longleftrightarrow> ms_lesseq_impl xs ys \<noteq> None"
```
```  2138   using ms_lesseq_impl[of xs ys] by (cases "ms_lesseq_impl xs ys", auto)
```
```  2139
```
```  2140 lemma [code]: "mset xs <# mset ys \<longleftrightarrow> ms_lesseq_impl xs ys = Some True"
```
```  2141   using ms_lesseq_impl[of xs ys] by (cases "ms_lesseq_impl xs ys", auto)
```
```  2142
```
```  2143 instantiation multiset :: (equal) equal
```
```  2144 begin
```
```  2145
```
```  2146 definition
```
```  2147   [code del]: "HOL.equal A (B :: 'a multiset) \<longleftrightarrow> A = B"
```
```  2148 lemma [code]: "HOL.equal (mset xs) (mset ys) \<longleftrightarrow> ms_lesseq_impl xs ys = Some False"
```
```  2149   unfolding equal_multiset_def
```
```  2150   using ms_lesseq_impl[of xs ys] by (cases "ms_lesseq_impl xs ys", auto)
```
```  2151
```
```  2152 instance
```
```  2153   by standard (simp add: equal_multiset_def)
```
```  2154
```
```  2155 end
```
```  2156
```
```  2157 lemma [code]: "msetsum (mset xs) = listsum xs"
```
```  2158   by (induct xs) (simp_all add: add.commute)
```
```  2159
```
```  2160 lemma [code]: "msetprod (mset xs) = fold times xs 1"
```
```  2161 proof -
```
```  2162   have "\<And>x. fold times xs x = msetprod (mset xs) * x"
```
```  2163     by (induct xs) (simp_all add: mult.assoc)
```
```  2164   then show ?thesis by simp
```
```  2165 qed
```
```  2166
```
```  2167 text \<open>
```
```  2168   Exercise for the casual reader: add implementations for @{const le_multiset}
```
```  2169   and @{const less_multiset} (multiset order).
```
```  2170 \<close>
```
```  2171
```
```  2172 text \<open>Quickcheck generators\<close>
```
```  2173
```
```  2174 definition (in term_syntax)
```
```  2175   msetify :: "'a::typerep list \<times> (unit \<Rightarrow> Code_Evaluation.term)
```
```  2176     \<Rightarrow> 'a multiset \<times> (unit \<Rightarrow> Code_Evaluation.term)" where
```
```  2177   [code_unfold]: "msetify xs = Code_Evaluation.valtermify mset {\<cdot>} xs"
```
```  2178
```
```  2179 notation fcomp (infixl "\<circ>>" 60)
```
```  2180 notation scomp (infixl "\<circ>\<rightarrow>" 60)
```
```  2181
```
```  2182 instantiation multiset :: (random) random
```
```  2183 begin
```
```  2184
```
```  2185 definition
```
```  2186   "Quickcheck_Random.random i = Quickcheck_Random.random i \<circ>\<rightarrow> (\<lambda>xs. Pair (msetify xs))"
```
```  2187
```
```  2188 instance ..
```
```  2189
```
```  2190 end
```
```  2191
```
```  2192 no_notation fcomp (infixl "\<circ>>" 60)
```
```  2193 no_notation scomp (infixl "\<circ>\<rightarrow>" 60)
```
```  2194
```
```  2195 instantiation multiset :: (full_exhaustive) full_exhaustive
```
```  2196 begin
```
```  2197
```
```  2198 definition full_exhaustive_multiset :: "('a multiset \<times> (unit \<Rightarrow> term) \<Rightarrow> (bool \<times> term list) option) \<Rightarrow> natural \<Rightarrow> (bool \<times> term list) option"
```
```  2199 where
```
```  2200   "full_exhaustive_multiset f i = Quickcheck_Exhaustive.full_exhaustive (\<lambda>xs. f (msetify xs)) i"
```
```  2201
```
```  2202 instance ..
```
```  2203
```
```  2204 end
```
```  2205
```
```  2206 hide_const (open) msetify
```
```  2207
```
```  2208
```
```  2209 subsection \<open>BNF setup\<close>
```
```  2210
```
```  2211 definition rel_mset where
```
```  2212   "rel_mset R X Y \<longleftrightarrow> (\<exists>xs ys. mset xs = X \<and> mset ys = Y \<and> list_all2 R xs ys)"
```
```  2213
```
```  2214 lemma mset_zip_take_Cons_drop_twice:
```
```  2215   assumes "length xs = length ys" "j \<le> length xs"
```
```  2216   shows "mset (zip (take j xs @ x # drop j xs) (take j ys @ y # drop j ys)) =
```
```  2217     mset (zip xs ys) + {#(x, y)#}"
```
```  2218   using assms
```
```  2219 proof (induct xs ys arbitrary: x y j rule: list_induct2)
```
```  2220   case Nil
```
```  2221   thus ?case
```
```  2222     by simp
```
```  2223 next
```
```  2224   case (Cons x xs y ys)
```
```  2225   thus ?case
```
```  2226   proof (cases "j = 0")
```
```  2227     case True
```
```  2228     thus ?thesis
```
```  2229       by simp
```
```  2230   next
```
```  2231     case False
```
```  2232     then obtain k where k: "j = Suc k"
```
```  2233       by (cases j) simp
```
```  2234     hence "k \<le> length xs"
```
```  2235       using Cons.prems by auto
```
```  2236     hence "mset (zip (take k xs @ x # drop k xs) (take k ys @ y # drop k ys)) =
```
```  2237       mset (zip xs ys) + {#(x, y)#}"
```
```  2238       by (rule Cons.hyps(2))
```
```  2239     thus ?thesis
```
```  2240       unfolding k by (auto simp: add.commute union_lcomm)
```
```  2241   qed
```
```  2242 qed
```
```  2243
```
```  2244 lemma ex_mset_zip_left:
```
```  2245   assumes "length xs = length ys" "mset xs' = mset xs"
```
```  2246   shows "\<exists>ys'. length ys' = length xs' \<and> mset (zip xs' ys') = mset (zip xs ys)"
```
```  2247 using assms
```
```  2248 proof (induct xs ys arbitrary: xs' rule: list_induct2)
```
```  2249   case Nil
```
```  2250   thus ?case
```
```  2251     by auto
```
```  2252 next
```
```  2253   case (Cons x xs y ys xs')
```
```  2254   obtain j where j_len: "j < length xs'" and nth_j: "xs' ! j = x"
```
```  2255     by (metis Cons.prems in_set_conv_nth list.set_intros(1) mset_eq_setD)
```
```  2256
```
```  2257   def xsa \<equiv> "take j xs' @ drop (Suc j) xs'"
```
```  2258   have "mset xs' = {#x#} + mset xsa"
```
```  2259     unfolding xsa_def using j_len nth_j
```
```  2260     by (metis (no_types) ab_semigroup_add_class.add_ac(1) append_take_drop_id Cons_nth_drop_Suc
```
```  2261       mset.simps(2) union_code add.commute)
```
```  2262   hence ms_x: "mset xsa = mset xs"
```
```  2263     by (metis Cons.prems add.commute add_right_imp_eq mset.simps(2))
```
```  2264   then obtain ysa where
```
```  2265     len_a: "length ysa = length xsa" and ms_a: "mset (zip xsa ysa) = mset (zip xs ys)"
```
```  2266     using Cons.hyps(2) by blast
```
```  2267
```
```  2268   def ys' \<equiv> "take j ysa @ y # drop j ysa"
```
```  2269   have xs': "xs' = take j xsa @ x # drop j xsa"
```
```  2270     using ms_x j_len nth_j Cons.prems xsa_def
```
```  2271     by (metis append_eq_append_conv append_take_drop_id diff_Suc_Suc Cons_nth_drop_Suc length_Cons
```
```  2272       length_drop size_mset)
```
```  2273   have j_len': "j \<le> length xsa"
```
```  2274     using j_len xs' xsa_def
```
```  2275     by (metis add_Suc_right append_take_drop_id length_Cons length_append less_eq_Suc_le not_less)
```
```  2276   have "length ys' = length xs'"
```
```  2277     unfolding ys'_def using Cons.prems len_a ms_x
```
```  2278     by (metis add_Suc_right append_take_drop_id length_Cons length_append mset_eq_length)
```
```  2279   moreover have "mset (zip xs' ys') = mset (zip (x # xs) (y # ys))"
```
```  2280     unfolding xs' ys'_def
```
```  2281     by (rule trans[OF mset_zip_take_Cons_drop_twice])
```
```  2282       (auto simp: len_a ms_a j_len' add.commute)
```
```  2283   ultimately show ?case
```
```  2284     by blast
```
```  2285 qed
```
```  2286
```
```  2287 lemma list_all2_reorder_left_invariance:
```
```  2288   assumes rel: "list_all2 R xs ys" and ms_x: "mset xs' = mset xs"
```
```  2289   shows "\<exists>ys'. list_all2 R xs' ys' \<and> mset ys' = mset ys"
```
```  2290 proof -
```
```  2291   have len: "length xs = length ys"
```
```  2292     using rel list_all2_conv_all_nth by auto
```
```  2293   obtain ys' where
```
```  2294     len': "length xs' = length ys'" and ms_xy: "mset (zip xs' ys') = mset (zip xs ys)"
```
```  2295     using len ms_x by (metis ex_mset_zip_left)
```
```  2296   have "list_all2 R xs' ys'"
```
```  2297     using assms(1) len' ms_xy unfolding list_all2_iff by (blast dest: mset_eq_setD)
```
```  2298   moreover have "mset ys' = mset ys"
```
```  2299     using len len' ms_xy map_snd_zip mset_map by metis
```
```  2300   ultimately show ?thesis
```
```  2301     by blast
```
```  2302 qed
```
```  2303
```
```  2304 lemma ex_mset: "\<exists>xs. mset xs = X"
```
```  2305   by (induct X) (simp, metis mset.simps(2))
```
```  2306
```
```  2307 bnf "'a multiset"
```
```  2308   map: image_mset
```
```  2309   sets: set_mset
```
```  2310   bd: natLeq
```
```  2311   wits: "{#}"
```
```  2312   rel: rel_mset
```
```  2313 proof -
```
```  2314   show "image_mset id = id"
```
```  2315     by (rule image_mset.id)
```
```  2316   show "image_mset (g \<circ> f) = image_mset g \<circ> image_mset f" for f g
```
```  2317     unfolding comp_def by (rule ext) (simp add: comp_def image_mset.compositionality)
```
```  2318   show "(\<And>z. z \<in> set_mset X \<Longrightarrow> f z = g z) \<Longrightarrow> image_mset f X = image_mset g X" for f g X
```
```  2319     by (induct X) (simp_all (no_asm),
```
```  2320       metis One_nat_def Un_iff count_single mem_set_mset_iff set_mset_union zero_less_Suc)
```
```  2321   show "set_mset \<circ> image_mset f = op ` f \<circ> set_mset" for f
```
```  2322     by auto
```
```  2323   show "card_order natLeq"
```
```  2324     by (rule natLeq_card_order)
```
```  2325   show "BNF_Cardinal_Arithmetic.cinfinite natLeq"
```
```  2326     by (rule natLeq_cinfinite)
```
```  2327   show "ordLeq3 (card_of (set_mset X)) natLeq" for X
```
```  2328     by transfer
```
```  2329       (auto intro!: ordLess_imp_ordLeq simp: finite_iff_ordLess_natLeq[symmetric] multiset_def)
```
```  2330   show "rel_mset R OO rel_mset S \<le> rel_mset (R OO S)" for R S
```
```  2331     unfolding rel_mset_def[abs_def] OO_def
```
```  2332     apply clarify
```
```  2333     subgoal for X Z Y xs ys' ys zs
```
```  2334       apply (drule list_all2_reorder_left_invariance [where xs = ys' and ys = zs and xs' = ys])
```
```  2335       apply (auto intro: list_all2_trans)
```
```  2336       done
```
```  2337     done
```
```  2338   show "rel_mset R =
```
```  2339     (BNF_Def.Grp {x. set_mset x \<subseteq> {(x, y). R x y}} (image_mset fst))\<inverse>\<inverse> OO
```
```  2340     BNF_Def.Grp {x. set_mset x \<subseteq> {(x, y). R x y}} (image_mset snd)" for R
```
```  2341     unfolding rel_mset_def[abs_def] BNF_Def.Grp_def OO_def
```
```  2342     apply (rule ext)+
```
```  2343     apply auto
```
```  2344      apply (rule_tac x = "mset (zip xs ys)" in exI; auto)
```
```  2345         apply (metis list_all2_lengthD map_fst_zip mset_map)
```
```  2346        apply (auto simp: list_all2_iff)[1]
```
```  2347       apply (metis list_all2_lengthD map_snd_zip mset_map)
```
```  2348      apply (auto simp: list_all2_iff)[1]
```
```  2349     apply (rename_tac XY)
```
```  2350     apply (cut_tac X = XY in ex_mset)
```
```  2351     apply (erule exE)
```
```  2352     apply (rename_tac xys)
```
```  2353     apply (rule_tac x = "map fst xys" in exI)
```
```  2354     apply (auto simp: mset_map)
```
```  2355     apply (rule_tac x = "map snd xys" in exI)
```
```  2356     apply (auto simp: mset_map list_all2I subset_eq zip_map_fst_snd)
```
```  2357     done
```
```  2358   show "z \<in> set_mset {#} \<Longrightarrow> False" for z
```
```  2359     by auto
```
```  2360 qed
```
```  2361
```
```  2362 inductive rel_mset'
```
```  2363 where
```
```  2364   Zero[intro]: "rel_mset' R {#} {#}"
```
```  2365 | Plus[intro]: "\<lbrakk>R a b; rel_mset' R M N\<rbrakk> \<Longrightarrow> rel_mset' R (M + {#a#}) (N + {#b#})"
```
```  2366
```
```  2367 lemma rel_mset_Zero: "rel_mset R {#} {#}"
```
```  2368 unfolding rel_mset_def Grp_def by auto
```
```  2369
```
```  2370 declare multiset.count[simp]
```
```  2371 declare Abs_multiset_inverse[simp]
```
```  2372 declare multiset.count_inverse[simp]
```
```  2373 declare union_preserves_multiset[simp]
```
```  2374
```
```  2375 lemma rel_mset_Plus:
```
```  2376   assumes ab: "R a b"
```
```  2377     and MN: "rel_mset R M N"
```
```  2378   shows "rel_mset R (M + {#a#}) (N + {#b#})"
```
```  2379 proof -
```
```  2380   have "\<exists>ya. image_mset fst y + {#a#} = image_mset fst ya \<and>
```
```  2381     image_mset snd y + {#b#} = image_mset snd ya \<and>
```
```  2382     set_mset ya \<subseteq> {(x, y). R x y}"
```
```  2383     if "R a b" and "set_mset y \<subseteq> {(x, y). R x y}" for y
```
```  2384     using that by (intro exI[of _ "y + {#(a,b)#}"]) auto
```
```  2385   thus ?thesis
```
```  2386   using assms
```
```  2387   unfolding multiset.rel_compp_Grp Grp_def by blast
```
```  2388 qed
```
```  2389
```
```  2390 lemma rel_mset'_imp_rel_mset: "rel_mset' R M N \<Longrightarrow> rel_mset R M N"
```
```  2391   by (induct rule: rel_mset'.induct) (auto simp: rel_mset_Zero rel_mset_Plus)
```
```  2392
```
```  2393 lemma rel_mset_size: "rel_mset R M N \<Longrightarrow> size M = size N"
```
```  2394   unfolding multiset.rel_compp_Grp Grp_def by auto
```
```  2395
```
```  2396 lemma multiset_induct2[case_names empty addL addR]:
```
```  2397   assumes empty: "P {#} {#}"
```
```  2398     and addL: "\<And>M N a. P M N \<Longrightarrow> P (M + {#a#}) N"
```
```  2399     and addR: "\<And>M N a. P M N \<Longrightarrow> P M (N + {#a#})"
```
```  2400   shows "P M N"
```
```  2401 apply(induct N rule: multiset_induct)
```
```  2402   apply(induct M rule: multiset_induct, rule empty, erule addL)
```
```  2403   apply(induct M rule: multiset_induct, erule addR, erule addR)
```
```  2404 done
```
```  2405
```
```  2406 lemma multiset_induct2_size[consumes 1, case_names empty add]:
```
```  2407   assumes c: "size M = size N"
```
```  2408     and empty: "P {#} {#}"
```
```  2409     and add: "\<And>M N a b. P M N \<Longrightarrow> P (M + {#a#}) (N + {#b#})"
```
```  2410   shows "P M N"
```
```  2411   using c
```
```  2412 proof (induct M arbitrary: N rule: measure_induct_rule[of size])
```
```  2413   case (less M)
```
```  2414   show ?case
```
```  2415   proof(cases "M = {#}")
```
```  2416     case True hence "N = {#}" using less.prems by auto
```
```  2417     thus ?thesis using True empty by auto
```
```  2418   next
```
```  2419     case False then obtain M1 a where M: "M = M1 + {#a#}" by (metis multi_nonempty_split)
```
```  2420     have "N \<noteq> {#}" using False less.prems by auto
```
```  2421     then obtain N1 b where N: "N = N1 + {#b#}" by (metis multi_nonempty_split)
```
```  2422     have "size M1 = size N1" using less.prems unfolding M N by auto
```
```  2423     thus ?thesis using M N less.hyps add by auto
```
```  2424   qed
```
```  2425 qed
```
```  2426
```
```  2427 lemma msed_map_invL:
```
```  2428   assumes "image_mset f (M + {#a#}) = N"
```
```  2429   shows "\<exists>N1. N = N1 + {#f a#} \<and> image_mset f M = N1"
```
```  2430 proof -
```
```  2431   have "f a \<in># N"
```
```  2432     using assms multiset.set_map[of f "M + {#a#}"] by auto
```
```  2433   then obtain N1 where N: "N = N1 + {#f a#}" using multi_member_split by metis
```
```  2434   have "image_mset f M = N1" using assms unfolding N by simp
```
```  2435   thus ?thesis using N by blast
```
```  2436 qed
```
```  2437
```
```  2438 lemma msed_map_invR:
```
```  2439   assumes "image_mset f M = N + {#b#}"
```
```  2440   shows "\<exists>M1 a. M = M1 + {#a#} \<and> f a = b \<and> image_mset f M1 = N"
```
```  2441 proof -
```
```  2442   obtain a where a: "a \<in># M" and fa: "f a = b"
```
```  2443     using multiset.set_map[of f M] unfolding assms
```
```  2444     by (metis image_iff mem_set_mset_iff union_single_eq_member)
```
```  2445   then obtain M1 where M: "M = M1 + {#a#}" using multi_member_split by metis
```
```  2446   have "image_mset f M1 = N" using assms unfolding M fa[symmetric] by simp
```
```  2447   thus ?thesis using M fa by blast
```
```  2448 qed
```
```  2449
```
```  2450 lemma msed_rel_invL:
```
```  2451   assumes "rel_mset R (M + {#a#}) N"
```
```  2452   shows "\<exists>N1 b. N = N1 + {#b#} \<and> R a b \<and> rel_mset R M N1"
```
```  2453 proof -
```
```  2454   obtain K where KM: "image_mset fst K = M + {#a#}"
```
```  2455     and KN: "image_mset snd K = N" and sK: "set_mset K \<subseteq> {(a, b). R a b}"
```
```  2456     using assms
```
```  2457     unfolding multiset.rel_compp_Grp Grp_def by auto
```
```  2458   obtain K1 ab where K: "K = K1 + {#ab#}" and a: "fst ab = a"
```
```  2459     and K1M: "image_mset fst K1 = M" using msed_map_invR[OF KM] by auto
```
```  2460   obtain N1 where N: "N = N1 + {#snd ab#}" and K1N1: "image_mset snd K1 = N1"
```
```  2461     using msed_map_invL[OF KN[unfolded K]] by auto
```
```  2462   have Rab: "R a (snd ab)" using sK a unfolding K by auto
```
```  2463   have "rel_mset R M N1" using sK K1M K1N1
```
```  2464     unfolding K multiset.rel_compp_Grp Grp_def by auto
```
```  2465   thus ?thesis using N Rab by auto
```
```  2466 qed
```
```  2467
```
```  2468 lemma msed_rel_invR:
```
```  2469   assumes "rel_mset R M (N + {#b#})"
```
```  2470   shows "\<exists>M1 a. M = M1 + {#a#} \<and> R a b \<and> rel_mset R M1 N"
```
```  2471 proof -
```
```  2472   obtain K where KN: "image_mset snd K = N + {#b#}"
```
```  2473     and KM: "image_mset fst K = M" and sK: "set_mset K \<subseteq> {(a, b). R a b}"
```
```  2474     using assms
```
```  2475     unfolding multiset.rel_compp_Grp Grp_def by auto
```
```  2476   obtain K1 ab where K: "K = K1 + {#ab#}" and b: "snd ab = b"
```
```  2477     and K1N: "image_mset snd K1 = N" using msed_map_invR[OF KN] by auto
```
```  2478   obtain M1 where M: "M = M1 + {#fst ab#}" and K1M1: "image_mset fst K1 = M1"
```
```  2479     using msed_map_invL[OF KM[unfolded K]] by auto
```
```  2480   have Rab: "R (fst ab) b" using sK b unfolding K by auto
```
```  2481   have "rel_mset R M1 N" using sK K1N K1M1
```
```  2482     unfolding K multiset.rel_compp_Grp Grp_def by auto
```
```  2483   thus ?thesis using M Rab by auto
```
```  2484 qed
```
```  2485
```
```  2486 lemma rel_mset_imp_rel_mset':
```
```  2487   assumes "rel_mset R M N"
```
```  2488   shows "rel_mset' R M N"
```
```  2489 using assms proof(induct M arbitrary: N rule: measure_induct_rule[of size])
```
```  2490   case (less M)
```
```  2491   have c: "size M = size N" using rel_mset_size[OF less.prems] .
```
```  2492   show ?case
```
```  2493   proof(cases "M = {#}")
```
```  2494     case True hence "N = {#}" using c by simp
```
```  2495     thus ?thesis using True rel_mset'.Zero by auto
```
```  2496   next
```
```  2497     case False then obtain M1 a where M: "M = M1 + {#a#}" by (metis multi_nonempty_split)
```
```  2498     obtain N1 b where N: "N = N1 + {#b#}" and R: "R a b" and ms: "rel_mset R M1 N1"
```
```  2499       using msed_rel_invL[OF less.prems[unfolded M]] by auto
```
```  2500     have "rel_mset' R M1 N1" using less.hyps[of M1 N1] ms unfolding M by simp
```
```  2501     thus ?thesis using rel_mset'.Plus[of R a b, OF R] unfolding M N by simp
```
```  2502   qed
```
```  2503 qed
```
```  2504
```
```  2505 lemma rel_mset_rel_mset': "rel_mset R M N = rel_mset' R M N"
```
```  2506   using rel_mset_imp_rel_mset' rel_mset'_imp_rel_mset by auto
```
```  2507
```
```  2508 text \<open>The main end product for @{const rel_mset}: inductive characterization:\<close>
```
```  2509 lemmas rel_mset_induct[case_names empty add, induct pred: rel_mset] =
```
```  2510   rel_mset'.induct[unfolded rel_mset_rel_mset'[symmetric]]
```
```  2511
```
```  2512
```
```  2513 subsection \<open>Size setup\<close>
```
```  2514
```
```  2515 lemma multiset_size_o_map: "size_multiset g \<circ> image_mset f = size_multiset (g \<circ> f)"
```
```  2516   apply (rule ext)
```
```  2517   subgoal for x by (induct x) auto
```
```  2518   done
```
```  2519
```
```  2520 setup \<open>
```
```  2521   BNF_LFP_Size.register_size_global @{type_name multiset} @{const_name size_multiset}
```
```  2522     @{thms size_multiset_empty size_multiset_single size_multiset_union size_empty size_single
```
```  2523       size_union}
```
```  2524     @{thms multiset_size_o_map}
```
```  2525 \<close>
```
```  2526
```
```  2527 hide_const (open) wcount
```
```  2528
```
```  2529 end
```