src/HOL/Library/Multiset.thy
 author haftmann Sat May 14 18:26:25 2011 +0200 (2011-05-14) changeset 42809 5b45125b15ba parent 41505 6d19301074cf child 42871 1c0b99f950d9 permissions -rw-r--r--
use pointfree characterisation for fold_set locale
```     1 (*  Title:      HOL/Library/Multiset.thy
```
```     2     Author:     Tobias Nipkow, Markus Wenzel, Lawrence C Paulson, Norbert Voelker
```
```     3 *)
```
```     4
```
```     5 header {* (Finite) multisets *}
```
```     6
```
```     7 theory Multiset
```
```     8 imports Main
```
```     9 begin
```
```    10
```
```    11 subsection {* The type of multisets *}
```
```    12
```
```    13 typedef 'a multiset = "{f :: 'a => nat. finite {x. f x > 0}}"
```
```    14   morphisms count Abs_multiset
```
```    15 proof
```
```    16   show "(\<lambda>x. 0::nat) \<in> ?multiset" by simp
```
```    17 qed
```
```    18
```
```    19 lemmas multiset_typedef = Abs_multiset_inverse count_inverse count
```
```    20
```
```    21 abbreviation Melem :: "'a => 'a multiset => bool"  ("(_/ :# _)" [50, 51] 50) where
```
```    22   "a :# M == 0 < count M a"
```
```    23
```
```    24 notation (xsymbols)
```
```    25   Melem (infix "\<in>#" 50)
```
```    26
```
```    27 lemma multiset_eq_iff:
```
```    28   "M = N \<longleftrightarrow> (\<forall>a. count M a = count N a)"
```
```    29   by (simp only: count_inject [symmetric] fun_eq_iff)
```
```    30
```
```    31 lemma multiset_eqI:
```
```    32   "(\<And>x. count A x = count B x) \<Longrightarrow> A = B"
```
```    33   using multiset_eq_iff by auto
```
```    34
```
```    35 text {*
```
```    36  \medskip Preservation of the representing set @{term multiset}.
```
```    37 *}
```
```    38
```
```    39 lemma const0_in_multiset:
```
```    40   "(\<lambda>a. 0) \<in> multiset"
```
```    41   by (simp add: multiset_def)
```
```    42
```
```    43 lemma only1_in_multiset:
```
```    44   "(\<lambda>b. if b = a then n else 0) \<in> multiset"
```
```    45   by (simp add: multiset_def)
```
```    46
```
```    47 lemma union_preserves_multiset:
```
```    48   "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 {* Representing multisets *}
```
```    76
```
```    77 text {* Multiset enumeration *}
```
```    78
```
```    79 instantiation multiset :: (type) "{zero, plus}"
```
```    80 begin
```
```    81
```
```    82 definition Mempty_def:
```
```    83   "0 = Abs_multiset (\<lambda>a. 0)"
```
```    84
```
```    85 abbreviation Mempty :: "'a multiset" ("{#}") where
```
```    86   "Mempty \<equiv> 0"
```
```    87
```
```    88 definition union_def:
```
```    89   "M + N = Abs_multiset (\<lambda>a. count M a + count N a)"
```
```    90
```
```    91 instance ..
```
```    92
```
```    93 end
```
```    94
```
```    95 definition single :: "'a => 'a multiset" where
```
```    96   "single a = Abs_multiset (\<lambda>b. if b = a then 1 else 0)"
```
```    97
```
```    98 syntax
```
```    99   "_multiset" :: "args => 'a multiset"    ("{#(_)#}")
```
```   100 translations
```
```   101   "{#x, xs#}" == "{#x#} + {#xs#}"
```
```   102   "{#x#}" == "CONST single x"
```
```   103
```
```   104 lemma count_empty [simp]: "count {#} a = 0"
```
```   105   by (simp add: Mempty_def in_multiset multiset_typedef)
```
```   106
```
```   107 lemma count_single [simp]: "count {#b#} a = (if b = a then 1 else 0)"
```
```   108   by (simp add: single_def in_multiset multiset_typedef)
```
```   109
```
```   110
```
```   111 subsection {* Basic operations *}
```
```   112
```
```   113 subsubsection {* Union *}
```
```   114
```
```   115 lemma count_union [simp]: "count (M + N) a = count M a + count N a"
```
```   116   by (simp add: union_def in_multiset multiset_typedef)
```
```   117
```
```   118 instance multiset :: (type) cancel_comm_monoid_add proof
```
```   119 qed (simp_all add: multiset_eq_iff)
```
```   120
```
```   121
```
```   122 subsubsection {* Difference *}
```
```   123
```
```   124 instantiation multiset :: (type) minus
```
```   125 begin
```
```   126
```
```   127 definition diff_def:
```
```   128   "M - N = Abs_multiset (\<lambda>a. count M a - count N a)"
```
```   129
```
```   130 instance ..
```
```   131
```
```   132 end
```
```   133
```
```   134 lemma count_diff [simp]: "count (M - N) a = count M a - count N a"
```
```   135   by (simp add: diff_def in_multiset multiset_typedef)
```
```   136
```
```   137 lemma diff_empty [simp]: "M - {#} = M \<and> {#} - M = {#}"
```
```   138 by(simp add: multiset_eq_iff)
```
```   139
```
```   140 lemma diff_cancel[simp]: "A - A = {#}"
```
```   141 by (rule multiset_eqI) simp
```
```   142
```
```   143 lemma diff_union_cancelR [simp]: "M + N - N = (M::'a multiset)"
```
```   144 by(simp add: multiset_eq_iff)
```
```   145
```
```   146 lemma diff_union_cancelL [simp]: "N + M - N = (M::'a multiset)"
```
```   147 by(simp add: multiset_eq_iff)
```
```   148
```
```   149 lemma insert_DiffM:
```
```   150   "x \<in># M \<Longrightarrow> {#x#} + (M - {#x#}) = M"
```
```   151   by (clarsimp simp: multiset_eq_iff)
```
```   152
```
```   153 lemma insert_DiffM2 [simp]:
```
```   154   "x \<in># M \<Longrightarrow> M - {#x#} + {#x#} = M"
```
```   155   by (clarsimp simp: multiset_eq_iff)
```
```   156
```
```   157 lemma diff_right_commute:
```
```   158   "(M::'a multiset) - N - Q = M - Q - N"
```
```   159   by (auto simp add: multiset_eq_iff)
```
```   160
```
```   161 lemma diff_add:
```
```   162   "(M::'a multiset) - (N + Q) = M - N - Q"
```
```   163 by (simp add: multiset_eq_iff)
```
```   164
```
```   165 lemma diff_union_swap:
```
```   166   "a \<noteq> b \<Longrightarrow> M - {#a#} + {#b#} = M + {#b#} - {#a#}"
```
```   167   by (auto simp add: multiset_eq_iff)
```
```   168
```
```   169 lemma diff_union_single_conv:
```
```   170   "a \<in># J \<Longrightarrow> I + J - {#a#} = I + (J - {#a#})"
```
```   171   by (simp add: multiset_eq_iff)
```
```   172
```
```   173
```
```   174 subsubsection {* Equality of multisets *}
```
```   175
```
```   176 lemma single_not_empty [simp]: "{#a#} \<noteq> {#} \<and> {#} \<noteq> {#a#}"
```
```   177   by (simp add: multiset_eq_iff)
```
```   178
```
```   179 lemma single_eq_single [simp]: "{#a#} = {#b#} \<longleftrightarrow> a = b"
```
```   180   by (auto simp add: multiset_eq_iff)
```
```   181
```
```   182 lemma union_eq_empty [iff]: "M + N = {#} \<longleftrightarrow> M = {#} \<and> N = {#}"
```
```   183   by (auto simp add: multiset_eq_iff)
```
```   184
```
```   185 lemma empty_eq_union [iff]: "{#} = M + N \<longleftrightarrow> M = {#} \<and> N = {#}"
```
```   186   by (auto simp add: multiset_eq_iff)
```
```   187
```
```   188 lemma multi_self_add_other_not_self [simp]: "M = M + {#x#} \<longleftrightarrow> False"
```
```   189   by (auto simp add: multiset_eq_iff)
```
```   190
```
```   191 lemma diff_single_trivial:
```
```   192   "\<not> x \<in># M \<Longrightarrow> M - {#x#} = M"
```
```   193   by (auto simp add: multiset_eq_iff)
```
```   194
```
```   195 lemma diff_single_eq_union:
```
```   196   "x \<in># M \<Longrightarrow> M - {#x#} = N \<longleftrightarrow> M = N + {#x#}"
```
```   197   by auto
```
```   198
```
```   199 lemma union_single_eq_diff:
```
```   200   "M + {#x#} = N \<Longrightarrow> M = N - {#x#}"
```
```   201   by (auto dest: sym)
```
```   202
```
```   203 lemma union_single_eq_member:
```
```   204   "M + {#x#} = N \<Longrightarrow> x \<in># N"
```
```   205   by auto
```
```   206
```
```   207 lemma union_is_single:
```
```   208   "M + N = {#a#} \<longleftrightarrow> M = {#a#} \<and> N={#} \<or> M = {#} \<and> N = {#a#}" (is "?lhs = ?rhs")proof
```
```   209   assume ?rhs then show ?lhs by auto
```
```   210 next
```
```   211   assume ?lhs thus ?rhs
```
```   212     by(simp add: multiset_eq_iff split:if_splits) (metis add_is_1)
```
```   213 qed
```
```   214
```
```   215 lemma single_is_union:
```
```   216   "{#a#} = M + N \<longleftrightarrow> {#a#} = M \<and> N = {#} \<or> M = {#} \<and> {#a#} = N"
```
```   217   by (auto simp add: eq_commute [of "{#a#}" "M + N"] union_is_single)
```
```   218
```
```   219 lemma add_eq_conv_diff:
```
```   220   "M + {#a#} = N + {#b#} \<longleftrightarrow> M = N \<and> a = b \<or> M = N - {#a#} + {#b#} \<and> N = M - {#b#} + {#a#}"  (is "?lhs = ?rhs")
```
```   221 (* shorter: by (simp add: multiset_eq_iff) fastsimp *)
```
```   222 proof
```
```   223   assume ?rhs then show ?lhs
```
```   224   by (auto simp add: add_assoc add_commute [of "{#b#}"])
```
```   225     (drule sym, simp add: add_assoc [symmetric])
```
```   226 next
```
```   227   assume ?lhs
```
```   228   show ?rhs
```
```   229   proof (cases "a = b")
```
```   230     case True with `?lhs` show ?thesis by simp
```
```   231   next
```
```   232     case False
```
```   233     from `?lhs` have "a \<in># N + {#b#}" by (rule union_single_eq_member)
```
```   234     with False have "a \<in># N" by auto
```
```   235     moreover from `?lhs` have "M = N + {#b#} - {#a#}" by (rule union_single_eq_diff)
```
```   236     moreover note False
```
```   237     ultimately show ?thesis by (auto simp add: diff_right_commute [of _ "{#a#}"] diff_union_swap)
```
```   238   qed
```
```   239 qed
```
```   240
```
```   241 lemma insert_noteq_member:
```
```   242   assumes BC: "B + {#b#} = C + {#c#}"
```
```   243    and bnotc: "b \<noteq> c"
```
```   244   shows "c \<in># B"
```
```   245 proof -
```
```   246   have "c \<in># C + {#c#}" by simp
```
```   247   have nc: "\<not> c \<in># {#b#}" using bnotc by simp
```
```   248   then have "c \<in># B + {#b#}" using BC by simp
```
```   249   then show "c \<in># B" using nc by simp
```
```   250 qed
```
```   251
```
```   252 lemma add_eq_conv_ex:
```
```   253   "(M + {#a#} = N + {#b#}) =
```
```   254     (M = N \<and> a = b \<or> (\<exists>K. M = K + {#b#} \<and> N = K + {#a#}))"
```
```   255   by (auto simp add: add_eq_conv_diff)
```
```   256
```
```   257
```
```   258 subsubsection {* Pointwise ordering induced by count *}
```
```   259
```
```   260 instantiation multiset :: (type) ordered_ab_semigroup_add_imp_le
```
```   261 begin
```
```   262
```
```   263 definition less_eq_multiset :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> bool" where
```
```   264   mset_le_def: "A \<le> B \<longleftrightarrow> (\<forall>a. count A a \<le> count B a)"
```
```   265
```
```   266 definition less_multiset :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> bool" where
```
```   267   mset_less_def: "(A::'a multiset) < B \<longleftrightarrow> A \<le> B \<and> A \<noteq> B"
```
```   268
```
```   269 instance proof
```
```   270 qed (auto simp add: mset_le_def mset_less_def multiset_eq_iff intro: order_trans antisym)
```
```   271
```
```   272 end
```
```   273
```
```   274 lemma mset_less_eqI:
```
```   275   "(\<And>x. count A x \<le> count B x) \<Longrightarrow> A \<le> B"
```
```   276   by (simp add: mset_le_def)
```
```   277
```
```   278 lemma mset_le_exists_conv:
```
```   279   "(A::'a multiset) \<le> B \<longleftrightarrow> (\<exists>C. B = A + C)"
```
```   280 apply (unfold mset_le_def, rule iffI, rule_tac x = "B - A" in exI)
```
```   281 apply (auto intro: multiset_eq_iff [THEN iffD2])
```
```   282 done
```
```   283
```
```   284 lemma mset_le_mono_add_right_cancel [simp]:
```
```   285   "(A::'a multiset) + C \<le> B + C \<longleftrightarrow> A \<le> B"
```
```   286   by (fact add_le_cancel_right)
```
```   287
```
```   288 lemma mset_le_mono_add_left_cancel [simp]:
```
```   289   "C + (A::'a multiset) \<le> C + B \<longleftrightarrow> A \<le> B"
```
```   290   by (fact add_le_cancel_left)
```
```   291
```
```   292 lemma mset_le_mono_add:
```
```   293   "(A::'a multiset) \<le> B \<Longrightarrow> C \<le> D \<Longrightarrow> A + C \<le> B + D"
```
```   294   by (fact add_mono)
```
```   295
```
```   296 lemma mset_le_add_left [simp]:
```
```   297   "(A::'a multiset) \<le> A + B"
```
```   298   unfolding mset_le_def by auto
```
```   299
```
```   300 lemma mset_le_add_right [simp]:
```
```   301   "B \<le> (A::'a multiset) + B"
```
```   302   unfolding mset_le_def by auto
```
```   303
```
```   304 lemma mset_le_single:
```
```   305   "a :# B \<Longrightarrow> {#a#} \<le> B"
```
```   306   by (simp add: mset_le_def)
```
```   307
```
```   308 lemma multiset_diff_union_assoc:
```
```   309   "C \<le> B \<Longrightarrow> (A::'a multiset) + B - C = A + (B - C)"
```
```   310   by (simp add: multiset_eq_iff mset_le_def)
```
```   311
```
```   312 lemma mset_le_multiset_union_diff_commute:
```
```   313   "B \<le> A \<Longrightarrow> (A::'a multiset) - B + C = A + C - B"
```
```   314 by (simp add: multiset_eq_iff mset_le_def)
```
```   315
```
```   316 lemma diff_le_self[simp]: "(M::'a multiset) - N \<le> M"
```
```   317 by(simp add: mset_le_def)
```
```   318
```
```   319 lemma mset_lessD: "A < B \<Longrightarrow> x \<in># A \<Longrightarrow> x \<in># B"
```
```   320 apply (clarsimp simp: mset_le_def mset_less_def)
```
```   321 apply (erule_tac x=x in allE)
```
```   322 apply auto
```
```   323 done
```
```   324
```
```   325 lemma mset_leD: "A \<le> B \<Longrightarrow> x \<in># A \<Longrightarrow> x \<in># B"
```
```   326 apply (clarsimp simp: mset_le_def mset_less_def)
```
```   327 apply (erule_tac x = x in allE)
```
```   328 apply auto
```
```   329 done
```
```   330
```
```   331 lemma mset_less_insertD: "(A + {#x#} < B) \<Longrightarrow> (x \<in># B \<and> A < B)"
```
```   332 apply (rule conjI)
```
```   333  apply (simp add: mset_lessD)
```
```   334 apply (clarsimp simp: mset_le_def mset_less_def)
```
```   335 apply safe
```
```   336  apply (erule_tac x = a in allE)
```
```   337  apply (auto split: split_if_asm)
```
```   338 done
```
```   339
```
```   340 lemma mset_le_insertD: "(A + {#x#} \<le> B) \<Longrightarrow> (x \<in># B \<and> A \<le> B)"
```
```   341 apply (rule conjI)
```
```   342  apply (simp add: mset_leD)
```
```   343 apply (force simp: mset_le_def mset_less_def split: split_if_asm)
```
```   344 done
```
```   345
```
```   346 lemma mset_less_of_empty[simp]: "A < {#} \<longleftrightarrow> False"
```
```   347   by (auto simp add: mset_less_def mset_le_def multiset_eq_iff)
```
```   348
```
```   349 lemma multi_psub_of_add_self[simp]: "A < A + {#x#}"
```
```   350   by (auto simp: mset_le_def mset_less_def)
```
```   351
```
```   352 lemma multi_psub_self[simp]: "(A::'a multiset) < A = False"
```
```   353   by simp
```
```   354
```
```   355 lemma mset_less_add_bothsides:
```
```   356   "T + {#x#} < S + {#x#} \<Longrightarrow> T < S"
```
```   357   by (fact add_less_imp_less_right)
```
```   358
```
```   359 lemma mset_less_empty_nonempty:
```
```   360   "{#} < S \<longleftrightarrow> S \<noteq> {#}"
```
```   361   by (auto simp: mset_le_def mset_less_def)
```
```   362
```
```   363 lemma mset_less_diff_self:
```
```   364   "c \<in># B \<Longrightarrow> B - {#c#} < B"
```
```   365   by (auto simp: mset_le_def mset_less_def multiset_eq_iff)
```
```   366
```
```   367
```
```   368 subsubsection {* Intersection *}
```
```   369
```
```   370 instantiation multiset :: (type) semilattice_inf
```
```   371 begin
```
```   372
```
```   373 definition inf_multiset :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> 'a multiset" where
```
```   374   multiset_inter_def: "inf_multiset A B = A - (A - B)"
```
```   375
```
```   376 instance proof -
```
```   377   have aux: "\<And>m n q :: nat. m \<le> n \<Longrightarrow> m \<le> q \<Longrightarrow> m \<le> n - (n - q)" by arith
```
```   378   show "OFCLASS('a multiset, semilattice_inf_class)" proof
```
```   379   qed (auto simp add: multiset_inter_def mset_le_def aux)
```
```   380 qed
```
```   381
```
```   382 end
```
```   383
```
```   384 abbreviation multiset_inter :: "'a multiset \<Rightarrow> 'a multiset \<Rightarrow> 'a multiset" (infixl "#\<inter>" 70) where
```
```   385   "multiset_inter \<equiv> inf"
```
```   386
```
```   387 lemma multiset_inter_count [simp]:
```
```   388   "count (A #\<inter> B) x = min (count A x) (count B x)"
```
```   389   by (simp add: multiset_inter_def multiset_typedef)
```
```   390
```
```   391 lemma multiset_inter_single: "a \<noteq> b \<Longrightarrow> {#a#} #\<inter> {#b#} = {#}"
```
```   392   by (rule multiset_eqI) (auto simp add: multiset_inter_count)
```
```   393
```
```   394 lemma multiset_union_diff_commute:
```
```   395   assumes "B #\<inter> C = {#}"
```
```   396   shows "A + B - C = A - C + B"
```
```   397 proof (rule multiset_eqI)
```
```   398   fix x
```
```   399   from assms have "min (count B x) (count C x) = 0"
```
```   400     by (auto simp add: multiset_inter_count multiset_eq_iff)
```
```   401   then have "count B x = 0 \<or> count C x = 0"
```
```   402     by auto
```
```   403   then show "count (A + B - C) x = count (A - C + B) x"
```
```   404     by auto
```
```   405 qed
```
```   406
```
```   407
```
```   408 subsubsection {* Filter (with comprehension syntax) *}
```
```   409
```
```   410 text {* Multiset comprehension *}
```
```   411
```
```   412 definition filter :: "('a \<Rightarrow> bool) \<Rightarrow> 'a multiset \<Rightarrow> 'a multiset" where
```
```   413   "filter P M = Abs_multiset (\<lambda>x. if P x then count M x else 0)"
```
```   414
```
```   415 hide_const (open) filter
```
```   416
```
```   417 lemma count_filter [simp]:
```
```   418   "count (Multiset.filter P M) a = (if P a then count M a else 0)"
```
```   419   by (simp add: filter_def in_multiset multiset_typedef)
```
```   420
```
```   421 lemma filter_empty [simp]:
```
```   422   "Multiset.filter P {#} = {#}"
```
```   423   by (rule multiset_eqI) simp
```
```   424
```
```   425 lemma filter_single [simp]:
```
```   426   "Multiset.filter P {#x#} = (if P x then {#x#} else {#})"
```
```   427   by (rule multiset_eqI) simp
```
```   428
```
```   429 lemma filter_union [simp]:
```
```   430   "Multiset.filter P (M + N) = Multiset.filter P M + Multiset.filter P N"
```
```   431   by (rule multiset_eqI) simp
```
```   432
```
```   433 lemma filter_diff [simp]:
```
```   434   "Multiset.filter P (M - N) = Multiset.filter P M - Multiset.filter P N"
```
```   435   by (rule multiset_eqI) simp
```
```   436
```
```   437 lemma filter_inter [simp]:
```
```   438   "Multiset.filter P (M #\<inter> N) = Multiset.filter P M #\<inter> Multiset.filter P N"
```
```   439   by (rule multiset_eqI) simp
```
```   440
```
```   441 syntax
```
```   442   "_MCollect" :: "pttrn \<Rightarrow> 'a multiset \<Rightarrow> bool \<Rightarrow> 'a multiset"    ("(1{# _ :# _./ _#})")
```
```   443 syntax (xsymbol)
```
```   444   "_MCollect" :: "pttrn \<Rightarrow> 'a multiset \<Rightarrow> bool \<Rightarrow> 'a multiset"    ("(1{# _ \<in># _./ _#})")
```
```   445 translations
```
```   446   "{#x \<in># M. P#}" == "CONST Multiset.filter (\<lambda>x. P) M"
```
```   447
```
```   448
```
```   449 subsubsection {* Set of elements *}
```
```   450
```
```   451 definition set_of :: "'a multiset => 'a set" where
```
```   452   "set_of M = {x. x :# M}"
```
```   453
```
```   454 lemma set_of_empty [simp]: "set_of {#} = {}"
```
```   455 by (simp add: set_of_def)
```
```   456
```
```   457 lemma set_of_single [simp]: "set_of {#b#} = {b}"
```
```   458 by (simp add: set_of_def)
```
```   459
```
```   460 lemma set_of_union [simp]: "set_of (M + N) = set_of M \<union> set_of N"
```
```   461 by (auto simp add: set_of_def)
```
```   462
```
```   463 lemma set_of_eq_empty_iff [simp]: "(set_of M = {}) = (M = {#})"
```
```   464 by (auto simp add: set_of_def multiset_eq_iff)
```
```   465
```
```   466 lemma mem_set_of_iff [simp]: "(x \<in> set_of M) = (x :# M)"
```
```   467 by (auto simp add: set_of_def)
```
```   468
```
```   469 lemma set_of_filter [simp]: "set_of {# x:#M. P x #} = set_of M \<inter> {x. P x}"
```
```   470 by (auto simp add: set_of_def)
```
```   471
```
```   472 lemma finite_set_of [iff]: "finite (set_of M)"
```
```   473   using count [of M] by (simp add: multiset_def set_of_def)
```
```   474
```
```   475
```
```   476 subsubsection {* Size *}
```
```   477
```
```   478 instantiation multiset :: (type) size
```
```   479 begin
```
```   480
```
```   481 definition size_def:
```
```   482   "size M = setsum (count M) (set_of M)"
```
```   483
```
```   484 instance ..
```
```   485
```
```   486 end
```
```   487
```
```   488 lemma size_empty [simp]: "size {#} = 0"
```
```   489 by (simp add: size_def)
```
```   490
```
```   491 lemma size_single [simp]: "size {#b#} = 1"
```
```   492 by (simp add: size_def)
```
```   493
```
```   494 lemma setsum_count_Int:
```
```   495   "finite A ==> setsum (count N) (A \<inter> set_of N) = setsum (count N) A"
```
```   496 apply (induct rule: finite_induct)
```
```   497  apply simp
```
```   498 apply (simp add: Int_insert_left set_of_def)
```
```   499 done
```
```   500
```
```   501 lemma size_union [simp]: "size (M + N::'a multiset) = size M + size N"
```
```   502 apply (unfold size_def)
```
```   503 apply (subgoal_tac "count (M + N) = (\<lambda>a. count M a + count N a)")
```
```   504  prefer 2
```
```   505  apply (rule ext, simp)
```
```   506 apply (simp (no_asm_simp) add: setsum_Un_nat setsum_addf setsum_count_Int)
```
```   507 apply (subst Int_commute)
```
```   508 apply (simp (no_asm_simp) add: setsum_count_Int)
```
```   509 done
```
```   510
```
```   511 lemma size_eq_0_iff_empty [iff]: "(size M = 0) = (M = {#})"
```
```   512 by (auto simp add: size_def multiset_eq_iff)
```
```   513
```
```   514 lemma nonempty_has_size: "(S \<noteq> {#}) = (0 < size S)"
```
```   515 by (metis gr0I gr_implies_not0 size_empty size_eq_0_iff_empty)
```
```   516
```
```   517 lemma size_eq_Suc_imp_elem: "size M = Suc n ==> \<exists>a. a :# M"
```
```   518 apply (unfold size_def)
```
```   519 apply (drule setsum_SucD)
```
```   520 apply auto
```
```   521 done
```
```   522
```
```   523 lemma size_eq_Suc_imp_eq_union:
```
```   524   assumes "size M = Suc n"
```
```   525   shows "\<exists>a N. M = N + {#a#}"
```
```   526 proof -
```
```   527   from assms obtain a where "a \<in># M"
```
```   528     by (erule size_eq_Suc_imp_elem [THEN exE])
```
```   529   then have "M = M - {#a#} + {#a#}" by simp
```
```   530   then show ?thesis by blast
```
```   531 qed
```
```   532
```
```   533
```
```   534 subsection {* Induction and case splits *}
```
```   535
```
```   536 lemma setsum_decr:
```
```   537   "finite F ==> (0::nat) < f a ==>
```
```   538     setsum (f (a := f a - 1)) F = (if a\<in>F then setsum f F - 1 else setsum f F)"
```
```   539 apply (induct rule: finite_induct)
```
```   540  apply auto
```
```   541 apply (drule_tac a = a in mk_disjoint_insert, auto)
```
```   542 done
```
```   543
```
```   544 lemma rep_multiset_induct_aux:
```
```   545 assumes 1: "P (\<lambda>a. (0::nat))"
```
```   546   and 2: "!!f b. f \<in> multiset ==> P f ==> P (f (b := f b + 1))"
```
```   547 shows "\<forall>f. f \<in> multiset --> setsum f {x. f x \<noteq> 0} = n --> P f"
```
```   548 apply (unfold multiset_def)
```
```   549 apply (induct_tac n, simp, clarify)
```
```   550  apply (subgoal_tac "f = (\<lambda>a.0)")
```
```   551   apply simp
```
```   552   apply (rule 1)
```
```   553  apply (rule ext, force, clarify)
```
```   554 apply (frule setsum_SucD, clarify)
```
```   555 apply (rename_tac a)
```
```   556 apply (subgoal_tac "finite {x. (f (a := f a - 1)) x > 0}")
```
```   557  prefer 2
```
```   558  apply (rule finite_subset)
```
```   559   prefer 2
```
```   560   apply assumption
```
```   561  apply simp
```
```   562  apply blast
```
```   563 apply (subgoal_tac "f = (f (a := f a - 1))(a := (f (a := f a - 1)) a + 1)")
```
```   564  prefer 2
```
```   565  apply (rule ext)
```
```   566  apply (simp (no_asm_simp))
```
```   567  apply (erule ssubst, rule 2 [unfolded multiset_def], blast)
```
```   568 apply (erule allE, erule impE, erule_tac  mp, blast)
```
```   569 apply (simp (no_asm_simp) add: setsum_decr del: fun_upd_apply One_nat_def)
```
```   570 apply (subgoal_tac "{x. x \<noteq> a --> f x \<noteq> 0} = {x. f x \<noteq> 0}")
```
```   571  prefer 2
```
```   572  apply blast
```
```   573 apply (subgoal_tac "{x. x \<noteq> a \<and> f x \<noteq> 0} = {x. f x \<noteq> 0} - {a}")
```
```   574  prefer 2
```
```   575  apply blast
```
```   576 apply (simp add: le_imp_diff_is_add setsum_diff1_nat cong: conj_cong)
```
```   577 done
```
```   578
```
```   579 theorem rep_multiset_induct:
```
```   580   "f \<in> multiset ==> P (\<lambda>a. 0) ==>
```
```   581     (!!f b. f \<in> multiset ==> P f ==> P (f (b := f b + 1))) ==> P f"
```
```   582 using rep_multiset_induct_aux by blast
```
```   583
```
```   584 theorem multiset_induct [case_names empty add, induct type: multiset]:
```
```   585 assumes empty: "P {#}"
```
```   586   and add: "!!M x. P M ==> P (M + {#x#})"
```
```   587 shows "P M"
```
```   588 proof -
```
```   589   note defns = union_def single_def Mempty_def
```
```   590   note add' = add [unfolded defns, simplified]
```
```   591   have aux: "\<And>a::'a. count (Abs_multiset (\<lambda>b. if b = a then 1 else 0)) =
```
```   592     (\<lambda>b. if b = a then 1 else 0)" by (simp add: Abs_multiset_inverse in_multiset)
```
```   593   show ?thesis
```
```   594     apply (rule count_inverse [THEN subst])
```
```   595     apply (rule count [THEN rep_multiset_induct])
```
```   596      apply (rule empty [unfolded defns])
```
```   597     apply (subgoal_tac "f(b := f b + 1) = (\<lambda>a. f a + (if a=b then 1 else 0))")
```
```   598      prefer 2
```
```   599      apply (simp add: fun_eq_iff)
```
```   600     apply (erule ssubst)
```
```   601     apply (erule Abs_multiset_inverse [THEN subst])
```
```   602     apply (drule add')
```
```   603     apply (simp add: aux)
```
```   604     done
```
```   605 qed
```
```   606
```
```   607 lemma multi_nonempty_split: "M \<noteq> {#} \<Longrightarrow> \<exists>A a. M = A + {#a#}"
```
```   608 by (induct M) auto
```
```   609
```
```   610 lemma multiset_cases [cases type, case_names empty add]:
```
```   611 assumes em:  "M = {#} \<Longrightarrow> P"
```
```   612 assumes add: "\<And>N x. M = N + {#x#} \<Longrightarrow> P"
```
```   613 shows "P"
```
```   614 proof (cases "M = {#}")
```
```   615   assume "M = {#}" then show ?thesis using em by simp
```
```   616 next
```
```   617   assume "M \<noteq> {#}"
```
```   618   then obtain M' m where "M = M' + {#m#}"
```
```   619     by (blast dest: multi_nonempty_split)
```
```   620   then show ?thesis using add by simp
```
```   621 qed
```
```   622
```
```   623 lemma multi_member_split: "x \<in># M \<Longrightarrow> \<exists>A. M = A + {#x#}"
```
```   624 apply (cases M)
```
```   625  apply simp
```
```   626 apply (rule_tac x="M - {#x#}" in exI, simp)
```
```   627 done
```
```   628
```
```   629 lemma multi_drop_mem_not_eq: "c \<in># B \<Longrightarrow> B - {#c#} \<noteq> B"
```
```   630 by (cases "B = {#}") (auto dest: multi_member_split)
```
```   631
```
```   632 lemma multiset_partition: "M = {# x:#M. P x #} + {# x:#M. \<not> P x #}"
```
```   633 apply (subst multiset_eq_iff)
```
```   634 apply auto
```
```   635 done
```
```   636
```
```   637 lemma mset_less_size: "(A::'a multiset) < B \<Longrightarrow> size A < size B"
```
```   638 proof (induct A arbitrary: B)
```
```   639   case (empty M)
```
```   640   then have "M \<noteq> {#}" by (simp add: mset_less_empty_nonempty)
```
```   641   then obtain M' x where "M = M' + {#x#}"
```
```   642     by (blast dest: multi_nonempty_split)
```
```   643   then show ?case by simp
```
```   644 next
```
```   645   case (add S x T)
```
```   646   have IH: "\<And>B. S < B \<Longrightarrow> size S < size B" by fact
```
```   647   have SxsubT: "S + {#x#} < T" by fact
```
```   648   then have "x \<in># T" and "S < T" by (auto dest: mset_less_insertD)
```
```   649   then obtain T' where T: "T = T' + {#x#}"
```
```   650     by (blast dest: multi_member_split)
```
```   651   then have "S < T'" using SxsubT
```
```   652     by (blast intro: mset_less_add_bothsides)
```
```   653   then have "size S < size T'" using IH by simp
```
```   654   then show ?case using T by simp
```
```   655 qed
```
```   656
```
```   657
```
```   658 subsubsection {* Strong induction and subset induction for multisets *}
```
```   659
```
```   660 text {* Well-foundedness of proper subset operator: *}
```
```   661
```
```   662 text {* proper multiset subset *}
```
```   663
```
```   664 definition
```
```   665   mset_less_rel :: "('a multiset * 'a multiset) set" where
```
```   666   "mset_less_rel = {(A,B). A < B}"
```
```   667
```
```   668 lemma multiset_add_sub_el_shuffle:
```
```   669   assumes "c \<in># B" and "b \<noteq> c"
```
```   670   shows "B - {#c#} + {#b#} = B + {#b#} - {#c#}"
```
```   671 proof -
```
```   672   from `c \<in># B` obtain A where B: "B = A + {#c#}"
```
```   673     by (blast dest: multi_member_split)
```
```   674   have "A + {#b#} = A + {#b#} + {#c#} - {#c#}" by simp
```
```   675   then have "A + {#b#} = A + {#c#} + {#b#} - {#c#}"
```
```   676     by (simp add: add_ac)
```
```   677   then show ?thesis using B by simp
```
```   678 qed
```
```   679
```
```   680 lemma wf_mset_less_rel: "wf mset_less_rel"
```
```   681 apply (unfold mset_less_rel_def)
```
```   682 apply (rule wf_measure [THEN wf_subset, where f1=size])
```
```   683 apply (clarsimp simp: measure_def inv_image_def mset_less_size)
```
```   684 done
```
```   685
```
```   686 text {* The induction rules: *}
```
```   687
```
```   688 lemma full_multiset_induct [case_names less]:
```
```   689 assumes ih: "\<And>B. \<forall>(A::'a multiset). A < B \<longrightarrow> P A \<Longrightarrow> P B"
```
```   690 shows "P B"
```
```   691 apply (rule wf_mset_less_rel [THEN wf_induct])
```
```   692 apply (rule ih, auto simp: mset_less_rel_def)
```
```   693 done
```
```   694
```
```   695 lemma multi_subset_induct [consumes 2, case_names empty add]:
```
```   696 assumes "F \<le> A"
```
```   697   and empty: "P {#}"
```
```   698   and insert: "\<And>a F. a \<in># A \<Longrightarrow> P F \<Longrightarrow> P (F + {#a#})"
```
```   699 shows "P F"
```
```   700 proof -
```
```   701   from `F \<le> A`
```
```   702   show ?thesis
```
```   703   proof (induct F)
```
```   704     show "P {#}" by fact
```
```   705   next
```
```   706     fix x F
```
```   707     assume P: "F \<le> A \<Longrightarrow> P F" and i: "F + {#x#} \<le> A"
```
```   708     show "P (F + {#x#})"
```
```   709     proof (rule insert)
```
```   710       from i show "x \<in># A" by (auto dest: mset_le_insertD)
```
```   711       from i have "F \<le> A" by (auto dest: mset_le_insertD)
```
```   712       with P show "P F" .
```
```   713     qed
```
```   714   qed
```
```   715 qed
```
```   716
```
```   717
```
```   718 subsection {* Alternative representations *}
```
```   719
```
```   720 subsubsection {* Lists *}
```
```   721
```
```   722 primrec multiset_of :: "'a list \<Rightarrow> 'a multiset" where
```
```   723   "multiset_of [] = {#}" |
```
```   724   "multiset_of (a # x) = multiset_of x + {# a #}"
```
```   725
```
```   726 lemma in_multiset_in_set:
```
```   727   "x \<in># multiset_of xs \<longleftrightarrow> x \<in> set xs"
```
```   728   by (induct xs) simp_all
```
```   729
```
```   730 lemma count_multiset_of:
```
```   731   "count (multiset_of xs) x = length (filter (\<lambda>y. x = y) xs)"
```
```   732   by (induct xs) simp_all
```
```   733
```
```   734 lemma multiset_of_zero_iff[simp]: "(multiset_of x = {#}) = (x = [])"
```
```   735 by (induct x) auto
```
```   736
```
```   737 lemma multiset_of_zero_iff_right[simp]: "({#} = multiset_of x) = (x = [])"
```
```   738 by (induct x) auto
```
```   739
```
```   740 lemma set_of_multiset_of[simp]: "set_of (multiset_of x) = set x"
```
```   741 by (induct x) auto
```
```   742
```
```   743 lemma mem_set_multiset_eq: "x \<in> set xs = (x :# multiset_of xs)"
```
```   744 by (induct xs) auto
```
```   745
```
```   746 lemma multiset_of_append [simp]:
```
```   747   "multiset_of (xs @ ys) = multiset_of xs + multiset_of ys"
```
```   748   by (induct xs arbitrary: ys) (auto simp: add_ac)
```
```   749
```
```   750 lemma multiset_of_filter:
```
```   751   "multiset_of (filter P xs) = {#x :# multiset_of xs. P x #}"
```
```   752   by (induct xs) simp_all
```
```   753
```
```   754 lemma multiset_of_rev [simp]:
```
```   755   "multiset_of (rev xs) = multiset_of xs"
```
```   756   by (induct xs) simp_all
```
```   757
```
```   758 lemma surj_multiset_of: "surj multiset_of"
```
```   759 apply (unfold surj_def)
```
```   760 apply (rule allI)
```
```   761 apply (rule_tac M = y in multiset_induct)
```
```   762  apply auto
```
```   763 apply (rule_tac x = "x # xa" in exI)
```
```   764 apply auto
```
```   765 done
```
```   766
```
```   767 lemma set_count_greater_0: "set x = {a. count (multiset_of x) a > 0}"
```
```   768 by (induct x) auto
```
```   769
```
```   770 lemma distinct_count_atmost_1:
```
```   771   "distinct x = (! a. count (multiset_of x) a = (if a \<in> set x then 1 else 0))"
```
```   772 apply (induct x, simp, rule iffI, simp_all)
```
```   773 apply (rule conjI)
```
```   774 apply (simp_all add: set_of_multiset_of [THEN sym] del: set_of_multiset_of)
```
```   775 apply (erule_tac x = a in allE, simp, clarify)
```
```   776 apply (erule_tac x = aa in allE, simp)
```
```   777 done
```
```   778
```
```   779 lemma multiset_of_eq_setD:
```
```   780   "multiset_of xs = multiset_of ys \<Longrightarrow> set xs = set ys"
```
```   781 by (rule) (auto simp add:multiset_eq_iff set_count_greater_0)
```
```   782
```
```   783 lemma set_eq_iff_multiset_of_eq_distinct:
```
```   784   "distinct x \<Longrightarrow> distinct y \<Longrightarrow>
```
```   785     (set x = set y) = (multiset_of x = multiset_of y)"
```
```   786 by (auto simp: multiset_eq_iff distinct_count_atmost_1)
```
```   787
```
```   788 lemma set_eq_iff_multiset_of_remdups_eq:
```
```   789    "(set x = set y) = (multiset_of (remdups x) = multiset_of (remdups y))"
```
```   790 apply (rule iffI)
```
```   791 apply (simp add: set_eq_iff_multiset_of_eq_distinct[THEN iffD1])
```
```   792 apply (drule distinct_remdups [THEN distinct_remdups
```
```   793       [THEN set_eq_iff_multiset_of_eq_distinct [THEN iffD2]]])
```
```   794 apply simp
```
```   795 done
```
```   796
```
```   797 lemma multiset_of_compl_union [simp]:
```
```   798   "multiset_of [x\<leftarrow>xs. P x] + multiset_of [x\<leftarrow>xs. \<not>P x] = multiset_of xs"
```
```   799   by (induct xs) (auto simp: add_ac)
```
```   800
```
```   801 lemma count_multiset_of_length_filter:
```
```   802   "count (multiset_of xs) x = length (filter (\<lambda>y. x = y) xs)"
```
```   803   by (induct xs) auto
```
```   804
```
```   805 lemma nth_mem_multiset_of: "i < length ls \<Longrightarrow> (ls ! i) :# multiset_of ls"
```
```   806 apply (induct ls arbitrary: i)
```
```   807  apply simp
```
```   808 apply (case_tac i)
```
```   809  apply auto
```
```   810 done
```
```   811
```
```   812 lemma multiset_of_remove1[simp]:
```
```   813   "multiset_of (remove1 a xs) = multiset_of xs - {#a#}"
```
```   814 by (induct xs) (auto simp add: multiset_eq_iff)
```
```   815
```
```   816 lemma multiset_of_eq_length:
```
```   817   assumes "multiset_of xs = multiset_of ys"
```
```   818   shows "length xs = length ys"
```
```   819 using assms proof (induct xs arbitrary: ys)
```
```   820   case Nil then show ?case by simp
```
```   821 next
```
```   822   case (Cons x xs)
```
```   823   then have "x \<in># multiset_of ys" by (simp add: union_single_eq_member)
```
```   824   then have "x \<in> set ys" by (simp add: in_multiset_in_set)
```
```   825   from Cons.prems [symmetric] have "multiset_of xs = multiset_of (remove1 x ys)"
```
```   826     by simp
```
```   827   with Cons.hyps have "length xs = length (remove1 x ys)" .
```
```   828   with `x \<in> set ys` show ?case
```
```   829     by (auto simp add: length_remove1 dest: length_pos_if_in_set)
```
```   830 qed
```
```   831
```
```   832 lemma multiset_of_eq_length_filter:
```
```   833   assumes "multiset_of xs = multiset_of ys"
```
```   834   shows "length (filter (\<lambda>x. z = x) xs) = length (filter (\<lambda>y. z = y) ys)"
```
```   835 proof (cases "z \<in># multiset_of xs")
```
```   836   case False
```
```   837   moreover have "\<not> z \<in># multiset_of ys" using assms False by simp
```
```   838   ultimately show ?thesis by (simp add: count_multiset_of_length_filter)
```
```   839 next
```
```   840   case True
```
```   841   moreover have "z \<in># multiset_of ys" using assms True by simp
```
```   842   show ?thesis using assms proof (induct xs arbitrary: ys)
```
```   843     case Nil then show ?case by simp
```
```   844   next
```
```   845     case (Cons x xs)
```
```   846     from `multiset_of (x # xs) = multiset_of ys` [symmetric]
```
```   847       have *: "multiset_of xs = multiset_of (remove1 x ys)"
```
```   848       and "x \<in> set ys"
```
```   849       by (auto simp add: mem_set_multiset_eq)
```
```   850     from * have "length (filter (\<lambda>x. z = x) xs) = length (filter (\<lambda>y. z = y) (remove1 x ys))" by (rule Cons.hyps)
```
```   851     moreover from `x \<in> set ys` have "length (filter (\<lambda>y. x = y) ys) > 0" by (simp add: filter_empty_conv)
```
```   852     ultimately show ?case using `x \<in> set ys`
```
```   853       by (simp add: filter_remove1) (auto simp add: length_remove1)
```
```   854   qed
```
```   855 qed
```
```   856
```
```   857 context linorder
```
```   858 begin
```
```   859
```
```   860 lemma multiset_of_insort [simp]:
```
```   861   "multiset_of (insort_key k x xs) = {#x#} + multiset_of xs"
```
```   862   by (induct xs) (simp_all add: ac_simps)
```
```   863
```
```   864 lemma multiset_of_sort [simp]:
```
```   865   "multiset_of (sort_key k xs) = multiset_of xs"
```
```   866   by (induct xs) (simp_all add: ac_simps)
```
```   867
```
```   868 text {*
```
```   869   This lemma shows which properties suffice to show that a function
```
```   870   @{text "f"} with @{text "f xs = ys"} behaves like sort.
```
```   871 *}
```
```   872
```
```   873 lemma properties_for_sort_key:
```
```   874   assumes "multiset_of ys = multiset_of xs"
```
```   875   and "\<And>k. k \<in> set ys \<Longrightarrow> filter (\<lambda>x. f k = f x) ys = filter (\<lambda>x. f k = f x) xs"
```
```   876   and "sorted (map f ys)"
```
```   877   shows "sort_key f xs = ys"
```
```   878 using assms proof (induct xs arbitrary: ys)
```
```   879   case Nil then show ?case by simp
```
```   880 next
```
```   881   case (Cons x xs)
```
```   882   from Cons.prems(2) have
```
```   883     "\<forall>k \<in> set ys. filter (\<lambda>x. f k = f x) (remove1 x ys) = filter (\<lambda>x. f k = f x) xs"
```
```   884     by (simp add: filter_remove1)
```
```   885   with Cons.prems have "sort_key f xs = remove1 x ys"
```
```   886     by (auto intro!: Cons.hyps simp add: sorted_map_remove1)
```
```   887   moreover from Cons.prems have "x \<in> set ys"
```
```   888     by (auto simp add: mem_set_multiset_eq intro!: ccontr)
```
```   889   ultimately show ?case using Cons.prems by (simp add: insort_key_remove1)
```
```   890 qed
```
```   891
```
```   892 lemma properties_for_sort:
```
```   893   assumes multiset: "multiset_of ys = multiset_of xs"
```
```   894   and "sorted ys"
```
```   895   shows "sort xs = ys"
```
```   896 proof (rule properties_for_sort_key)
```
```   897   from multiset show "multiset_of ys = multiset_of xs" .
```
```   898   from `sorted ys` show "sorted (map (\<lambda>x. x) ys)" by simp
```
```   899   from multiset have "\<And>k. length (filter (\<lambda>y. k = y) ys) = length (filter (\<lambda>x. k = x) xs)"
```
```   900     by (rule multiset_of_eq_length_filter)
```
```   901   then have "\<And>k. replicate (length (filter (\<lambda>y. k = y) ys)) k = replicate (length (filter (\<lambda>x. k = x) xs)) k"
```
```   902     by simp
```
```   903   then show "\<And>k. k \<in> set ys \<Longrightarrow> filter (\<lambda>y. k = y) ys = filter (\<lambda>x. k = x) xs"
```
```   904     by (simp add: replicate_length_filter)
```
```   905 qed
```
```   906
```
```   907 lemma sort_key_by_quicksort:
```
```   908   "sort_key f xs = sort_key f [x\<leftarrow>xs. f x < f (xs ! (length xs div 2))]
```
```   909     @ [x\<leftarrow>xs. f x = f (xs ! (length xs div 2))]
```
```   910     @ sort_key f [x\<leftarrow>xs. f x > f (xs ! (length xs div 2))]" (is "sort_key f ?lhs = ?rhs")
```
```   911 proof (rule properties_for_sort_key)
```
```   912   show "multiset_of ?rhs = multiset_of ?lhs"
```
```   913     by (rule multiset_eqI) (auto simp add: multiset_of_filter)
```
```   914 next
```
```   915   show "sorted (map f ?rhs)"
```
```   916     by (auto simp add: sorted_append intro: sorted_map_same)
```
```   917 next
```
```   918   fix l
```
```   919   assume "l \<in> set ?rhs"
```
```   920   let ?pivot = "f (xs ! (length xs div 2))"
```
```   921   have *: "\<And>x. f l = f x \<longleftrightarrow> f x = f l" by auto
```
```   922   have "[x \<leftarrow> sort_key f xs . f x = f l] = [x \<leftarrow> xs. f x = f l]"
```
```   923     unfolding filter_sort by (rule properties_for_sort_key) (auto intro: sorted_map_same)
```
```   924   with * have **: "[x \<leftarrow> sort_key f xs . f l = f x] = [x \<leftarrow> xs. f l = f x]" by simp
```
```   925   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
```
```   926   then have "\<And>P. [x \<leftarrow> sort_key f xs . P (f x) ?pivot \<and> f l = f x] =
```
```   927     [x \<leftarrow> sort_key f xs. P (f l) ?pivot \<and> f l = f x]" by simp
```
```   928   note *** = this [of "op <"] this [of "op >"] this [of "op ="]
```
```   929   show "[x \<leftarrow> ?rhs. f l = f x] = [x \<leftarrow> ?lhs. f l = f x]"
```
```   930   proof (cases "f l" ?pivot rule: linorder_cases)
```
```   931     case less then moreover have "f l \<noteq> ?pivot" and "\<not> f l > ?pivot" by auto
```
```   932     ultimately show ?thesis
```
```   933       by (simp add: filter_sort [symmetric] ** ***)
```
```   934   next
```
```   935     case equal then show ?thesis
```
```   936       by (simp add: * less_le)
```
```   937   next
```
```   938     case greater then moreover have "f l \<noteq> ?pivot" and "\<not> f l < ?pivot" by auto
```
```   939     ultimately show ?thesis
```
```   940       by (simp add: filter_sort [symmetric] ** ***)
```
```   941   qed
```
```   942 qed
```
```   943
```
```   944 lemma sort_by_quicksort:
```
```   945   "sort xs = sort [x\<leftarrow>xs. x < xs ! (length xs div 2)]
```
```   946     @ [x\<leftarrow>xs. x = xs ! (length xs div 2)]
```
```   947     @ sort [x\<leftarrow>xs. x > xs ! (length xs div 2)]" (is "sort ?lhs = ?rhs")
```
```   948   using sort_key_by_quicksort [of "\<lambda>x. x", symmetric] by simp
```
```   949
```
```   950 text {* A stable parametrized quicksort *}
```
```   951
```
```   952 definition part :: "('b \<Rightarrow> 'a) \<Rightarrow> 'a \<Rightarrow> 'b list \<Rightarrow> 'b list \<times> 'b list \<times> 'b list" where
```
```   953   "part f pivot xs = ([x \<leftarrow> xs. f x < pivot], [x \<leftarrow> xs. f x = pivot], [x \<leftarrow> xs. pivot < f x])"
```
```   954
```
```   955 lemma part_code [code]:
```
```   956   "part f pivot [] = ([], [], [])"
```
```   957   "part f pivot (x # xs) = (let (lts, eqs, gts) = part f pivot xs; x' = f x in
```
```   958      if x' < pivot then (x # lts, eqs, gts)
```
```   959      else if x' > pivot then (lts, eqs, x # gts)
```
```   960      else (lts, x # eqs, gts))"
```
```   961   by (auto simp add: part_def Let_def split_def)
```
```   962
```
```   963 lemma sort_key_by_quicksort_code [code]:
```
```   964   "sort_key f xs = (case xs of [] \<Rightarrow> []
```
```   965     | [x] \<Rightarrow> xs
```
```   966     | [x, y] \<Rightarrow> (if f x \<le> f y then xs else [y, x])
```
```   967     | _ \<Rightarrow> (let (lts, eqs, gts) = part f (f (xs ! (length xs div 2))) xs
```
```   968        in sort_key f lts @ eqs @ sort_key f gts))"
```
```   969 proof (cases xs)
```
```   970   case Nil then show ?thesis by simp
```
```   971 next
```
```   972   case (Cons _ ys) note hyps = Cons show ?thesis proof (cases ys)
```
```   973     case Nil with hyps show ?thesis by simp
```
```   974   next
```
```   975     case (Cons _ zs) note hyps = hyps Cons show ?thesis proof (cases zs)
```
```   976       case Nil with hyps show ?thesis by auto
```
```   977     next
```
```   978       case Cons
```
```   979       from sort_key_by_quicksort [of f xs]
```
```   980       have "sort_key f xs = (let (lts, eqs, gts) = part f (f (xs ! (length xs div 2))) xs
```
```   981         in sort_key f lts @ eqs @ sort_key f gts)"
```
```   982       by (simp only: split_def Let_def part_def fst_conv snd_conv)
```
```   983       with hyps Cons show ?thesis by (simp only: list.cases)
```
```   984     qed
```
```   985   qed
```
```   986 qed
```
```   987
```
```   988 end
```
```   989
```
```   990 hide_const (open) part
```
```   991
```
```   992 lemma multiset_of_remdups_le: "multiset_of (remdups xs) \<le> multiset_of xs"
```
```   993   by (induct xs) (auto intro: order_trans)
```
```   994
```
```   995 lemma multiset_of_update:
```
```   996   "i < length ls \<Longrightarrow> multiset_of (ls[i := v]) = multiset_of ls - {#ls ! i#} + {#v#}"
```
```   997 proof (induct ls arbitrary: i)
```
```   998   case Nil then show ?case by simp
```
```   999 next
```
```  1000   case (Cons x xs)
```
```  1001   show ?case
```
```  1002   proof (cases i)
```
```  1003     case 0 then show ?thesis by simp
```
```  1004   next
```
```  1005     case (Suc i')
```
```  1006     with Cons show ?thesis
```
```  1007       apply simp
```
```  1008       apply (subst add_assoc)
```
```  1009       apply (subst add_commute [of "{#v#}" "{#x#}"])
```
```  1010       apply (subst add_assoc [symmetric])
```
```  1011       apply simp
```
```  1012       apply (rule mset_le_multiset_union_diff_commute)
```
```  1013       apply (simp add: mset_le_single nth_mem_multiset_of)
```
```  1014       done
```
```  1015   qed
```
```  1016 qed
```
```  1017
```
```  1018 lemma multiset_of_swap:
```
```  1019   "i < length ls \<Longrightarrow> j < length ls \<Longrightarrow>
```
```  1020     multiset_of (ls[j := ls ! i, i := ls ! j]) = multiset_of ls"
```
```  1021   by (cases "i = j") (simp_all add: multiset_of_update nth_mem_multiset_of)
```
```  1022
```
```  1023
```
```  1024 subsubsection {* Association lists -- including rudimentary code generation *}
```
```  1025
```
```  1026 definition count_of :: "('a \<times> nat) list \<Rightarrow> 'a \<Rightarrow> nat" where
```
```  1027   "count_of xs x = (case map_of xs x of None \<Rightarrow> 0 | Some n \<Rightarrow> n)"
```
```  1028
```
```  1029 lemma count_of_multiset:
```
```  1030   "count_of xs \<in> multiset"
```
```  1031 proof -
```
```  1032   let ?A = "{x::'a. 0 < (case map_of xs x of None \<Rightarrow> 0\<Colon>nat | Some (n\<Colon>nat) \<Rightarrow> n)}"
```
```  1033   have "?A \<subseteq> dom (map_of xs)"
```
```  1034   proof
```
```  1035     fix x
```
```  1036     assume "x \<in> ?A"
```
```  1037     then have "0 < (case map_of xs x of None \<Rightarrow> 0\<Colon>nat | Some (n\<Colon>nat) \<Rightarrow> n)" by simp
```
```  1038     then have "map_of xs x \<noteq> None" by (cases "map_of xs x") auto
```
```  1039     then show "x \<in> dom (map_of xs)" by auto
```
```  1040   qed
```
```  1041   with finite_dom_map_of [of xs] have "finite ?A"
```
```  1042     by (auto intro: finite_subset)
```
```  1043   then show ?thesis
```
```  1044     by (simp add: count_of_def fun_eq_iff multiset_def)
```
```  1045 qed
```
```  1046
```
```  1047 lemma count_simps [simp]:
```
```  1048   "count_of [] = (\<lambda>_. 0)"
```
```  1049   "count_of ((x, n) # xs) = (\<lambda>y. if x = y then n else count_of xs y)"
```
```  1050   by (simp_all add: count_of_def fun_eq_iff)
```
```  1051
```
```  1052 lemma count_of_empty:
```
```  1053   "x \<notin> fst ` set xs \<Longrightarrow> count_of xs x = 0"
```
```  1054   by (induct xs) (simp_all add: count_of_def)
```
```  1055
```
```  1056 lemma count_of_filter:
```
```  1057   "count_of (filter (P \<circ> fst) xs) x = (if P x then count_of xs x else 0)"
```
```  1058   by (induct xs) auto
```
```  1059
```
```  1060 definition Bag :: "('a \<times> nat) list \<Rightarrow> 'a multiset" where
```
```  1061   "Bag xs = Abs_multiset (count_of xs)"
```
```  1062
```
```  1063 code_datatype Bag
```
```  1064
```
```  1065 lemma count_Bag [simp, code]:
```
```  1066   "count (Bag xs) = count_of xs"
```
```  1067   by (simp add: Bag_def count_of_multiset Abs_multiset_inverse)
```
```  1068
```
```  1069 lemma Mempty_Bag [code]:
```
```  1070   "{#} = Bag []"
```
```  1071   by (simp add: multiset_eq_iff)
```
```  1072
```
```  1073 lemma single_Bag [code]:
```
```  1074   "{#x#} = Bag [(x, 1)]"
```
```  1075   by (simp add: multiset_eq_iff)
```
```  1076
```
```  1077 lemma filter_Bag [code]:
```
```  1078   "Multiset.filter P (Bag xs) = Bag (filter (P \<circ> fst) xs)"
```
```  1079   by (rule multiset_eqI) (simp add: count_of_filter)
```
```  1080
```
```  1081 lemma mset_less_eq_Bag [code]:
```
```  1082   "Bag xs \<le> A \<longleftrightarrow> (\<forall>(x, n) \<in> set xs. count_of xs x \<le> count A x)"
```
```  1083     (is "?lhs \<longleftrightarrow> ?rhs")
```
```  1084 proof
```
```  1085   assume ?lhs then show ?rhs
```
```  1086     by (auto simp add: mset_le_def count_Bag)
```
```  1087 next
```
```  1088   assume ?rhs
```
```  1089   show ?lhs
```
```  1090   proof (rule mset_less_eqI)
```
```  1091     fix x
```
```  1092     from `?rhs` have "count_of xs x \<le> count A x"
```
```  1093       by (cases "x \<in> fst ` set xs") (auto simp add: count_of_empty)
```
```  1094     then show "count (Bag xs) x \<le> count A x"
```
```  1095       by (simp add: mset_le_def count_Bag)
```
```  1096   qed
```
```  1097 qed
```
```  1098
```
```  1099 instantiation multiset :: (equal) equal
```
```  1100 begin
```
```  1101
```
```  1102 definition
```
```  1103   "HOL.equal A B \<longleftrightarrow> (A::'a multiset) \<le> B \<and> B \<le> A"
```
```  1104
```
```  1105 instance proof
```
```  1106 qed (simp add: equal_multiset_def eq_iff)
```
```  1107
```
```  1108 end
```
```  1109
```
```  1110 lemma [code nbe]:
```
```  1111   "HOL.equal (A :: 'a::equal multiset) A \<longleftrightarrow> True"
```
```  1112   by (fact equal_refl)
```
```  1113
```
```  1114 definition (in term_syntax)
```
```  1115   bagify :: "('a\<Colon>typerep \<times> nat) list \<times> (unit \<Rightarrow> Code_Evaluation.term)
```
```  1116     \<Rightarrow> 'a multiset \<times> (unit \<Rightarrow> Code_Evaluation.term)" where
```
```  1117   [code_unfold]: "bagify xs = Code_Evaluation.valtermify Bag {\<cdot>} xs"
```
```  1118
```
```  1119 notation fcomp (infixl "\<circ>>" 60)
```
```  1120 notation scomp (infixl "\<circ>\<rightarrow>" 60)
```
```  1121
```
```  1122 instantiation multiset :: (random) random
```
```  1123 begin
```
```  1124
```
```  1125 definition
```
```  1126   "Quickcheck.random i = Quickcheck.random i \<circ>\<rightarrow> (\<lambda>xs. Pair (bagify xs))"
```
```  1127
```
```  1128 instance ..
```
```  1129
```
```  1130 end
```
```  1131
```
```  1132 no_notation fcomp (infixl "\<circ>>" 60)
```
```  1133 no_notation scomp (infixl "\<circ>\<rightarrow>" 60)
```
```  1134
```
```  1135 hide_const (open) bagify
```
```  1136
```
```  1137
```
```  1138 subsection {* The multiset order *}
```
```  1139
```
```  1140 subsubsection {* Well-foundedness *}
```
```  1141
```
```  1142 definition mult1 :: "('a \<times> 'a) set => ('a multiset \<times> 'a multiset) set" where
```
```  1143   "mult1 r = {(N, M). \<exists>a M0 K. M = M0 + {#a#} \<and> N = M0 + K \<and>
```
```  1144       (\<forall>b. b :# K --> (b, a) \<in> r)}"
```
```  1145
```
```  1146 definition mult :: "('a \<times> 'a) set => ('a multiset \<times> 'a multiset) set" where
```
```  1147   "mult r = (mult1 r)\<^sup>+"
```
```  1148
```
```  1149 lemma not_less_empty [iff]: "(M, {#}) \<notin> mult1 r"
```
```  1150 by (simp add: mult1_def)
```
```  1151
```
```  1152 lemma less_add: "(N, M0 + {#a#}) \<in> mult1 r ==>
```
```  1153     (\<exists>M. (M, M0) \<in> mult1 r \<and> N = M + {#a#}) \<or>
```
```  1154     (\<exists>K. (\<forall>b. b :# K --> (b, a) \<in> r) \<and> N = M0 + K)"
```
```  1155   (is "_ \<Longrightarrow> ?case1 (mult1 r) \<or> ?case2")
```
```  1156 proof (unfold mult1_def)
```
```  1157   let ?r = "\<lambda>K a. \<forall>b. b :# K --> (b, a) \<in> r"
```
```  1158   let ?R = "\<lambda>N M. \<exists>a M0 K. M = M0 + {#a#} \<and> N = M0 + K \<and> ?r K a"
```
```  1159   let ?case1 = "?case1 {(N, M). ?R N M}"
```
```  1160
```
```  1161   assume "(N, M0 + {#a#}) \<in> {(N, M). ?R N M}"
```
```  1162   then have "\<exists>a' M0' K.
```
```  1163       M0 + {#a#} = M0' + {#a'#} \<and> N = M0' + K \<and> ?r K a'" by simp
```
```  1164   then show "?case1 \<or> ?case2"
```
```  1165   proof (elim exE conjE)
```
```  1166     fix a' M0' K
```
```  1167     assume N: "N = M0' + K" and r: "?r K a'"
```
```  1168     assume "M0 + {#a#} = M0' + {#a'#}"
```
```  1169     then have "M0 = M0' \<and> a = a' \<or>
```
```  1170         (\<exists>K'. M0 = K' + {#a'#} \<and> M0' = K' + {#a#})"
```
```  1171       by (simp only: add_eq_conv_ex)
```
```  1172     then show ?thesis
```
```  1173     proof (elim disjE conjE exE)
```
```  1174       assume "M0 = M0'" "a = a'"
```
```  1175       with N r have "?r K a \<and> N = M0 + K" by simp
```
```  1176       then have ?case2 .. then show ?thesis ..
```
```  1177     next
```
```  1178       fix K'
```
```  1179       assume "M0' = K' + {#a#}"
```
```  1180       with N have n: "N = K' + K + {#a#}" by (simp add: add_ac)
```
```  1181
```
```  1182       assume "M0 = K' + {#a'#}"
```
```  1183       with r have "?R (K' + K) M0" by blast
```
```  1184       with n have ?case1 by simp then show ?thesis ..
```
```  1185     qed
```
```  1186   qed
```
```  1187 qed
```
```  1188
```
```  1189 lemma all_accessible: "wf r ==> \<forall>M. M \<in> acc (mult1 r)"
```
```  1190 proof
```
```  1191   let ?R = "mult1 r"
```
```  1192   let ?W = "acc ?R"
```
```  1193   {
```
```  1194     fix M M0 a
```
```  1195     assume M0: "M0 \<in> ?W"
```
```  1196       and wf_hyp: "!!b. (b, a) \<in> r ==> (\<forall>M \<in> ?W. M + {#b#} \<in> ?W)"
```
```  1197       and acc_hyp: "\<forall>M. (M, M0) \<in> ?R --> M + {#a#} \<in> ?W"
```
```  1198     have "M0 + {#a#} \<in> ?W"
```
```  1199     proof (rule accI [of "M0 + {#a#}"])
```
```  1200       fix N
```
```  1201       assume "(N, M0 + {#a#}) \<in> ?R"
```
```  1202       then have "((\<exists>M. (M, M0) \<in> ?R \<and> N = M + {#a#}) \<or>
```
```  1203           (\<exists>K. (\<forall>b. b :# K --> (b, a) \<in> r) \<and> N = M0 + K))"
```
```  1204         by (rule less_add)
```
```  1205       then show "N \<in> ?W"
```
```  1206       proof (elim exE disjE conjE)
```
```  1207         fix M assume "(M, M0) \<in> ?R" and N: "N = M + {#a#}"
```
```  1208         from acc_hyp have "(M, M0) \<in> ?R --> M + {#a#} \<in> ?W" ..
```
```  1209         from this and `(M, M0) \<in> ?R` have "M + {#a#} \<in> ?W" ..
```
```  1210         then show "N \<in> ?W" by (simp only: N)
```
```  1211       next
```
```  1212         fix K
```
```  1213         assume N: "N = M0 + K"
```
```  1214         assume "\<forall>b. b :# K --> (b, a) \<in> r"
```
```  1215         then have "M0 + K \<in> ?W"
```
```  1216         proof (induct K)
```
```  1217           case empty
```
```  1218           from M0 show "M0 + {#} \<in> ?W" by simp
```
```  1219         next
```
```  1220           case (add K x)
```
```  1221           from add.prems have "(x, a) \<in> r" by simp
```
```  1222           with wf_hyp have "\<forall>M \<in> ?W. M + {#x#} \<in> ?W" by blast
```
```  1223           moreover from add have "M0 + K \<in> ?W" by simp
```
```  1224           ultimately have "(M0 + K) + {#x#} \<in> ?W" ..
```
```  1225           then show "M0 + (K + {#x#}) \<in> ?W" by (simp only: add_assoc)
```
```  1226         qed
```
```  1227         then show "N \<in> ?W" by (simp only: N)
```
```  1228       qed
```
```  1229     qed
```
```  1230   } note tedious_reasoning = this
```
```  1231
```
```  1232   assume wf: "wf r"
```
```  1233   fix M
```
```  1234   show "M \<in> ?W"
```
```  1235   proof (induct M)
```
```  1236     show "{#} \<in> ?W"
```
```  1237     proof (rule accI)
```
```  1238       fix b assume "(b, {#}) \<in> ?R"
```
```  1239       with not_less_empty show "b \<in> ?W" by contradiction
```
```  1240     qed
```
```  1241
```
```  1242     fix M a assume "M \<in> ?W"
```
```  1243     from wf have "\<forall>M \<in> ?W. M + {#a#} \<in> ?W"
```
```  1244     proof induct
```
```  1245       fix a
```
```  1246       assume r: "!!b. (b, a) \<in> r ==> (\<forall>M \<in> ?W. M + {#b#} \<in> ?W)"
```
```  1247       show "\<forall>M \<in> ?W. M + {#a#} \<in> ?W"
```
```  1248       proof
```
```  1249         fix M assume "M \<in> ?W"
```
```  1250         then show "M + {#a#} \<in> ?W"
```
```  1251           by (rule acc_induct) (rule tedious_reasoning [OF _ r])
```
```  1252       qed
```
```  1253     qed
```
```  1254     from this and `M \<in> ?W` show "M + {#a#} \<in> ?W" ..
```
```  1255   qed
```
```  1256 qed
```
```  1257
```
```  1258 theorem wf_mult1: "wf r ==> wf (mult1 r)"
```
```  1259 by (rule acc_wfI) (rule all_accessible)
```
```  1260
```
```  1261 theorem wf_mult: "wf r ==> wf (mult r)"
```
```  1262 unfolding mult_def by (rule wf_trancl) (rule wf_mult1)
```
```  1263
```
```  1264
```
```  1265 subsubsection {* Closure-free presentation *}
```
```  1266
```
```  1267 text {* One direction. *}
```
```  1268
```
```  1269 lemma mult_implies_one_step:
```
```  1270   "trans r ==> (M, N) \<in> mult r ==>
```
```  1271     \<exists>I J K. N = I + J \<and> M = I + K \<and> J \<noteq> {#} \<and>
```
```  1272     (\<forall>k \<in> set_of K. \<exists>j \<in> set_of J. (k, j) \<in> r)"
```
```  1273 apply (unfold mult_def mult1_def set_of_def)
```
```  1274 apply (erule converse_trancl_induct, clarify)
```
```  1275  apply (rule_tac x = M0 in exI, simp, clarify)
```
```  1276 apply (case_tac "a :# K")
```
```  1277  apply (rule_tac x = I in exI)
```
```  1278  apply (simp (no_asm))
```
```  1279  apply (rule_tac x = "(K - {#a#}) + Ka" in exI)
```
```  1280  apply (simp (no_asm_simp) add: add_assoc [symmetric])
```
```  1281  apply (drule_tac f = "\<lambda>M. M - {#a#}" in arg_cong)
```
```  1282  apply (simp add: diff_union_single_conv)
```
```  1283  apply (simp (no_asm_use) add: trans_def)
```
```  1284  apply blast
```
```  1285 apply (subgoal_tac "a :# I")
```
```  1286  apply (rule_tac x = "I - {#a#}" in exI)
```
```  1287  apply (rule_tac x = "J + {#a#}" in exI)
```
```  1288  apply (rule_tac x = "K + Ka" in exI)
```
```  1289  apply (rule conjI)
```
```  1290   apply (simp add: multiset_eq_iff split: nat_diff_split)
```
```  1291  apply (rule conjI)
```
```  1292   apply (drule_tac f = "\<lambda>M. M - {#a#}" in arg_cong, simp)
```
```  1293   apply (simp add: multiset_eq_iff split: nat_diff_split)
```
```  1294  apply (simp (no_asm_use) add: trans_def)
```
```  1295  apply blast
```
```  1296 apply (subgoal_tac "a :# (M0 + {#a#})")
```
```  1297  apply simp
```
```  1298 apply (simp (no_asm))
```
```  1299 done
```
```  1300
```
```  1301 lemma one_step_implies_mult_aux:
```
```  1302   "trans r ==>
```
```  1303     \<forall>I J K. (size J = n \<and> J \<noteq> {#} \<and> (\<forall>k \<in> set_of K. \<exists>j \<in> set_of J. (k, j) \<in> r))
```
```  1304       --> (I + K, I + J) \<in> mult r"
```
```  1305 apply (induct_tac n, auto)
```
```  1306 apply (frule size_eq_Suc_imp_eq_union, clarify)
```
```  1307 apply (rename_tac "J'", simp)
```
```  1308 apply (erule notE, auto)
```
```  1309 apply (case_tac "J' = {#}")
```
```  1310  apply (simp add: mult_def)
```
```  1311  apply (rule r_into_trancl)
```
```  1312  apply (simp add: mult1_def set_of_def, blast)
```
```  1313 txt {* Now we know @{term "J' \<noteq> {#}"}. *}
```
```  1314 apply (cut_tac M = K and P = "\<lambda>x. (x, a) \<in> r" in multiset_partition)
```
```  1315 apply (erule_tac P = "\<forall>k \<in> set_of K. ?P k" in rev_mp)
```
```  1316 apply (erule ssubst)
```
```  1317 apply (simp add: Ball_def, auto)
```
```  1318 apply (subgoal_tac
```
```  1319   "((I + {# x :# K. (x, a) \<in> r #}) + {# x :# K. (x, a) \<notin> r #},
```
```  1320     (I + {# x :# K. (x, a) \<in> r #}) + J') \<in> mult r")
```
```  1321  prefer 2
```
```  1322  apply force
```
```  1323 apply (simp (no_asm_use) add: add_assoc [symmetric] mult_def)
```
```  1324 apply (erule trancl_trans)
```
```  1325 apply (rule r_into_trancl)
```
```  1326 apply (simp add: mult1_def set_of_def)
```
```  1327 apply (rule_tac x = a in exI)
```
```  1328 apply (rule_tac x = "I + J'" in exI)
```
```  1329 apply (simp add: add_ac)
```
```  1330 done
```
```  1331
```
```  1332 lemma one_step_implies_mult:
```
```  1333   "trans r ==> J \<noteq> {#} ==> \<forall>k \<in> set_of K. \<exists>j \<in> set_of J. (k, j) \<in> r
```
```  1334     ==> (I + K, I + J) \<in> mult r"
```
```  1335 using one_step_implies_mult_aux by blast
```
```  1336
```
```  1337
```
```  1338 subsubsection {* Partial-order properties *}
```
```  1339
```
```  1340 definition less_multiset :: "'a\<Colon>order multiset \<Rightarrow> 'a multiset \<Rightarrow> bool" (infix "<#" 50) where
```
```  1341   "M' <# M \<longleftrightarrow> (M', M) \<in> mult {(x', x). x' < x}"
```
```  1342
```
```  1343 definition le_multiset :: "'a\<Colon>order multiset \<Rightarrow> 'a multiset \<Rightarrow> bool" (infix "<=#" 50) where
```
```  1344   "M' <=# M \<longleftrightarrow> M' <# M \<or> M' = M"
```
```  1345
```
```  1346 notation (xsymbols) less_multiset (infix "\<subset>#" 50)
```
```  1347 notation (xsymbols) le_multiset (infix "\<subseteq>#" 50)
```
```  1348
```
```  1349 interpretation multiset_order: order le_multiset less_multiset
```
```  1350 proof -
```
```  1351   have irrefl: "\<And>M :: 'a multiset. \<not> M \<subset># M"
```
```  1352   proof
```
```  1353     fix M :: "'a multiset"
```
```  1354     assume "M \<subset># M"
```
```  1355     then have MM: "(M, M) \<in> mult {(x, y). x < y}" by (simp add: less_multiset_def)
```
```  1356     have "trans {(x'::'a, x). x' < x}"
```
```  1357       by (rule transI) simp
```
```  1358     moreover note MM
```
```  1359     ultimately have "\<exists>I J K. M = I + J \<and> M = I + K
```
```  1360       \<and> J \<noteq> {#} \<and> (\<forall>k\<in>set_of K. \<exists>j\<in>set_of J. (k, j) \<in> {(x, y). x < y})"
```
```  1361       by (rule mult_implies_one_step)
```
```  1362     then obtain I J K where "M = I + J" and "M = I + K"
```
```  1363       and "J \<noteq> {#}" and "(\<forall>k\<in>set_of K. \<exists>j\<in>set_of J. (k, j) \<in> {(x, y). x < y})" by blast
```
```  1364     then have aux1: "K \<noteq> {#}" and aux2: "\<forall>k\<in>set_of K. \<exists>j\<in>set_of K. k < j" by auto
```
```  1365     have "finite (set_of K)" by simp
```
```  1366     moreover note aux2
```
```  1367     ultimately have "set_of K = {}"
```
```  1368       by (induct rule: finite_induct) (auto intro: order_less_trans)
```
```  1369     with aux1 show False by simp
```
```  1370   qed
```
```  1371   have trans: "\<And>K M N :: 'a multiset. K \<subset># M \<Longrightarrow> M \<subset># N \<Longrightarrow> K \<subset># N"
```
```  1372     unfolding less_multiset_def mult_def by (blast intro: trancl_trans)
```
```  1373   show "class.order (le_multiset :: 'a multiset \<Rightarrow> _) less_multiset" proof
```
```  1374   qed (auto simp add: le_multiset_def irrefl dest: trans)
```
```  1375 qed
```
```  1376
```
```  1377 lemma mult_less_irrefl [elim!]:
```
```  1378   "M \<subset># (M::'a::order multiset) ==> R"
```
```  1379   by (simp add: multiset_order.less_irrefl)
```
```  1380
```
```  1381
```
```  1382 subsubsection {* Monotonicity of multiset union *}
```
```  1383
```
```  1384 lemma mult1_union:
```
```  1385   "(B, D) \<in> mult1 r ==> (C + B, C + D) \<in> mult1 r"
```
```  1386 apply (unfold mult1_def)
```
```  1387 apply auto
```
```  1388 apply (rule_tac x = a in exI)
```
```  1389 apply (rule_tac x = "C + M0" in exI)
```
```  1390 apply (simp add: add_assoc)
```
```  1391 done
```
```  1392
```
```  1393 lemma union_less_mono2: "B \<subset># D ==> C + B \<subset># C + (D::'a::order multiset)"
```
```  1394 apply (unfold less_multiset_def mult_def)
```
```  1395 apply (erule trancl_induct)
```
```  1396  apply (blast intro: mult1_union)
```
```  1397 apply (blast intro: mult1_union trancl_trans)
```
```  1398 done
```
```  1399
```
```  1400 lemma union_less_mono1: "B \<subset># D ==> B + C \<subset># D + (C::'a::order multiset)"
```
```  1401 apply (subst add_commute [of B C])
```
```  1402 apply (subst add_commute [of D C])
```
```  1403 apply (erule union_less_mono2)
```
```  1404 done
```
```  1405
```
```  1406 lemma union_less_mono:
```
```  1407   "A \<subset># C ==> B \<subset># D ==> A + B \<subset># C + (D::'a::order multiset)"
```
```  1408   by (blast intro!: union_less_mono1 union_less_mono2 multiset_order.less_trans)
```
```  1409
```
```  1410 interpretation multiset_order: ordered_ab_semigroup_add plus le_multiset less_multiset
```
```  1411 proof
```
```  1412 qed (auto simp add: le_multiset_def intro: union_less_mono2)
```
```  1413
```
```  1414
```
```  1415 subsection {* The fold combinator *}
```
```  1416
```
```  1417 text {*
```
```  1418   The intended behaviour is
```
```  1419   @{text "fold_mset f z {#x\<^isub>1, ..., x\<^isub>n#} = f x\<^isub>1 (\<dots> (f x\<^isub>n z)\<dots>)"}
```
```  1420   if @{text f} is associative-commutative.
```
```  1421 *}
```
```  1422
```
```  1423 text {*
```
```  1424   The graph of @{text "fold_mset"}, @{text "z"}: the start element,
```
```  1425   @{text "f"}: folding function, @{text "A"}: the multiset, @{text
```
```  1426   "y"}: the result.
```
```  1427 *}
```
```  1428 inductive
```
```  1429   fold_msetG :: "('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a multiset \<Rightarrow> 'b \<Rightarrow> bool"
```
```  1430   for f :: "'a \<Rightarrow> 'b \<Rightarrow> 'b"
```
```  1431   and z :: 'b
```
```  1432 where
```
```  1433   emptyI [intro]:  "fold_msetG f z {#} z"
```
```  1434 | insertI [intro]: "fold_msetG f z A y \<Longrightarrow> fold_msetG f z (A + {#x#}) (f x y)"
```
```  1435
```
```  1436 inductive_cases empty_fold_msetGE [elim!]: "fold_msetG f z {#} x"
```
```  1437 inductive_cases insert_fold_msetGE: "fold_msetG f z (A + {#}) y"
```
```  1438
```
```  1439 definition
```
```  1440   fold_mset :: "('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a multiset \<Rightarrow> 'b" where
```
```  1441   "fold_mset f z A = (THE x. fold_msetG f z A x)"
```
```  1442
```
```  1443 lemma Diff1_fold_msetG:
```
```  1444   "fold_msetG f z (A - {#x#}) y \<Longrightarrow> x \<in># A \<Longrightarrow> fold_msetG f z A (f x y)"
```
```  1445 apply (frule_tac x = x in fold_msetG.insertI)
```
```  1446 apply auto
```
```  1447 done
```
```  1448
```
```  1449 lemma fold_msetG_nonempty: "\<exists>x. fold_msetG f z A x"
```
```  1450 apply (induct A)
```
```  1451  apply blast
```
```  1452 apply clarsimp
```
```  1453 apply (drule_tac x = x in fold_msetG.insertI)
```
```  1454 apply auto
```
```  1455 done
```
```  1456
```
```  1457 lemma fold_mset_empty[simp]: "fold_mset f z {#} = z"
```
```  1458 unfolding fold_mset_def by blast
```
```  1459
```
```  1460 context fun_left_comm
```
```  1461 begin
```
```  1462
```
```  1463 lemma fold_msetG_determ:
```
```  1464   "fold_msetG f z A x \<Longrightarrow> fold_msetG f z A y \<Longrightarrow> y = x"
```
```  1465 proof (induct arbitrary: x y z rule: full_multiset_induct)
```
```  1466   case (less M x\<^isub>1 x\<^isub>2 Z)
```
```  1467   have IH: "\<forall>A. A < M \<longrightarrow>
```
```  1468     (\<forall>x x' x''. fold_msetG f x'' A x \<longrightarrow> fold_msetG f x'' A x'
```
```  1469                \<longrightarrow> x' = x)" by fact
```
```  1470   have Mfoldx\<^isub>1: "fold_msetG f Z M x\<^isub>1" and Mfoldx\<^isub>2: "fold_msetG f Z M x\<^isub>2" by fact+
```
```  1471   show ?case
```
```  1472   proof (rule fold_msetG.cases [OF Mfoldx\<^isub>1])
```
```  1473     assume "M = {#}" and "x\<^isub>1 = Z"
```
```  1474     then show ?case using Mfoldx\<^isub>2 by auto
```
```  1475   next
```
```  1476     fix B b u
```
```  1477     assume "M = B + {#b#}" and "x\<^isub>1 = f b u" and Bu: "fold_msetG f Z B u"
```
```  1478     then have MBb: "M = B + {#b#}" and x\<^isub>1: "x\<^isub>1 = f b u" by auto
```
```  1479     show ?case
```
```  1480     proof (rule fold_msetG.cases [OF Mfoldx\<^isub>2])
```
```  1481       assume "M = {#}" "x\<^isub>2 = Z"
```
```  1482       then show ?case using Mfoldx\<^isub>1 by auto
```
```  1483     next
```
```  1484       fix C c v
```
```  1485       assume "M = C + {#c#}" and "x\<^isub>2 = f c v" and Cv: "fold_msetG f Z C v"
```
```  1486       then have MCc: "M = C + {#c#}" and x\<^isub>2: "x\<^isub>2 = f c v" by auto
```
```  1487       then have CsubM: "C < M" by simp
```
```  1488       from MBb have BsubM: "B < M" by simp
```
```  1489       show ?case
```
```  1490       proof cases
```
```  1491         assume "b=c"
```
```  1492         then moreover have "B = C" using MBb MCc by auto
```
```  1493         ultimately show ?thesis using Bu Cv x\<^isub>1 x\<^isub>2 CsubM IH by auto
```
```  1494       next
```
```  1495         assume diff: "b \<noteq> c"
```
```  1496         let ?D = "B - {#c#}"
```
```  1497         have cinB: "c \<in># B" and binC: "b \<in># C" using MBb MCc diff
```
```  1498           by (auto intro: insert_noteq_member dest: sym)
```
```  1499         have "B - {#c#} < B" using cinB by (rule mset_less_diff_self)
```
```  1500         then have DsubM: "?D < M" using BsubM by (blast intro: order_less_trans)
```
```  1501         from MBb MCc have "B + {#b#} = C + {#c#}" by blast
```
```  1502         then have [simp]: "B + {#b#} - {#c#} = C"
```
```  1503           using MBb MCc binC cinB by auto
```
```  1504         have B: "B = ?D + {#c#}" and C: "C = ?D + {#b#}"
```
```  1505           using MBb MCc diff binC cinB
```
```  1506           by (auto simp: multiset_add_sub_el_shuffle)
```
```  1507         then obtain d where Dfoldd: "fold_msetG f Z ?D d"
```
```  1508           using fold_msetG_nonempty by iprover
```
```  1509         then have "fold_msetG f Z B (f c d)" using cinB
```
```  1510           by (rule Diff1_fold_msetG)
```
```  1511         then have "f c d = u" using IH BsubM Bu by blast
```
```  1512         moreover
```
```  1513         have "fold_msetG f Z C (f b d)" using binC cinB diff Dfoldd
```
```  1514           by (auto simp: multiset_add_sub_el_shuffle
```
```  1515             dest: fold_msetG.insertI [where x=b])
```
```  1516         then have "f b d = v" using IH CsubM Cv by blast
```
```  1517         ultimately show ?thesis using x\<^isub>1 x\<^isub>2
```
```  1518           by (auto simp: fun_left_comm)
```
```  1519       qed
```
```  1520     qed
```
```  1521   qed
```
```  1522 qed
```
```  1523
```
```  1524 lemma fold_mset_insert_aux:
```
```  1525   "(fold_msetG f z (A + {#x#}) v) =
```
```  1526     (\<exists>y. fold_msetG f z A y \<and> v = f x y)"
```
```  1527 apply (rule iffI)
```
```  1528  prefer 2
```
```  1529  apply blast
```
```  1530 apply (rule_tac A=A and f=f in fold_msetG_nonempty [THEN exE, standard])
```
```  1531 apply (blast intro: fold_msetG_determ)
```
```  1532 done
```
```  1533
```
```  1534 lemma fold_mset_equality: "fold_msetG f z A y \<Longrightarrow> fold_mset f z A = y"
```
```  1535 unfolding fold_mset_def by (blast intro: fold_msetG_determ)
```
```  1536
```
```  1537 lemma fold_mset_insert:
```
```  1538   "fold_mset f z (A + {#x#}) = f x (fold_mset f z A)"
```
```  1539 apply (simp add: fold_mset_def fold_mset_insert_aux)
```
```  1540 apply (rule the_equality)
```
```  1541  apply (auto cong add: conj_cong
```
```  1542      simp add: fold_mset_def [symmetric] fold_mset_equality fold_msetG_nonempty)
```
```  1543 done
```
```  1544
```
```  1545 lemma fold_mset_commute: "f x (fold_mset f z A) = fold_mset f (f x z) A"
```
```  1546 by (induct A) (auto simp: fold_mset_insert fun_left_comm [of x])
```
```  1547
```
```  1548 lemma fold_mset_single [simp]: "fold_mset f z {#x#} = f x z"
```
```  1549 using fold_mset_insert [of z "{#}"] by simp
```
```  1550
```
```  1551 lemma fold_mset_union [simp]:
```
```  1552   "fold_mset f z (A+B) = fold_mset f (fold_mset f z A) B"
```
```  1553 proof (induct A)
```
```  1554   case empty then show ?case by simp
```
```  1555 next
```
```  1556   case (add A x)
```
```  1557   have "A + {#x#} + B = (A+B) + {#x#}" by (simp add: add_ac)
```
```  1558   then have "fold_mset f z (A + {#x#} + B) = f x (fold_mset f z (A + B))"
```
```  1559     by (simp add: fold_mset_insert)
```
```  1560   also have "\<dots> = fold_mset f (fold_mset f z (A + {#x#})) B"
```
```  1561     by (simp add: fold_mset_commute[of x,symmetric] add fold_mset_insert)
```
```  1562   finally show ?case .
```
```  1563 qed
```
```  1564
```
```  1565 lemma fold_mset_fusion:
```
```  1566   assumes "fun_left_comm g"
```
```  1567   shows "(\<And>x y. h (g x y) = f x (h y)) \<Longrightarrow> h (fold_mset g w A) = fold_mset f (h w) A" (is "PROP ?P")
```
```  1568 proof -
```
```  1569   interpret fun_left_comm g by (fact assms)
```
```  1570   show "PROP ?P" by (induct A) auto
```
```  1571 qed
```
```  1572
```
```  1573 lemma fold_mset_rec:
```
```  1574   assumes "a \<in># A"
```
```  1575   shows "fold_mset f z A = f a (fold_mset f z (A - {#a#}))"
```
```  1576 proof -
```
```  1577   from assms obtain A' where "A = A' + {#a#}"
```
```  1578     by (blast dest: multi_member_split)
```
```  1579   then show ?thesis by simp
```
```  1580 qed
```
```  1581
```
```  1582 end
```
```  1583
```
```  1584 text {*
```
```  1585   A note on code generation: When defining some function containing a
```
```  1586   subterm @{term"fold_mset F"}, code generation is not automatic. When
```
```  1587   interpreting locale @{text left_commutative} with @{text F}, the
```
```  1588   would be code thms for @{const fold_mset} become thms like
```
```  1589   @{term"fold_mset F z {#} = z"} where @{text F} is not a pattern but
```
```  1590   contains defined symbols, i.e.\ is not a code thm. Hence a separate
```
```  1591   constant with its own code thms needs to be introduced for @{text
```
```  1592   F}. See the image operator below.
```
```  1593 *}
```
```  1594
```
```  1595
```
```  1596 subsection {* Image *}
```
```  1597
```
```  1598 definition image_mset :: "('a \<Rightarrow> 'b) \<Rightarrow> 'a multiset \<Rightarrow> 'b multiset" where
```
```  1599   "image_mset f = fold_mset (op + o single o f) {#}"
```
```  1600
```
```  1601 interpretation image_left_comm: fun_left_comm "op + o single o f"
```
```  1602 proof qed (simp add: add_ac fun_eq_iff)
```
```  1603
```
```  1604 lemma image_mset_empty [simp]: "image_mset f {#} = {#}"
```
```  1605 by (simp add: image_mset_def)
```
```  1606
```
```  1607 lemma image_mset_single [simp]: "image_mset f {#x#} = {#f x#}"
```
```  1608 by (simp add: image_mset_def)
```
```  1609
```
```  1610 lemma image_mset_insert:
```
```  1611   "image_mset f (M + {#a#}) = image_mset f M + {#f a#}"
```
```  1612 by (simp add: image_mset_def add_ac)
```
```  1613
```
```  1614 lemma image_mset_union [simp]:
```
```  1615   "image_mset f (M+N) = image_mset f M + image_mset f N"
```
```  1616 apply (induct N)
```
```  1617  apply simp
```
```  1618 apply (simp add: add_assoc [symmetric] image_mset_insert)
```
```  1619 done
```
```  1620
```
```  1621 lemma size_image_mset [simp]: "size (image_mset f M) = size M"
```
```  1622 by (induct M) simp_all
```
```  1623
```
```  1624 lemma image_mset_is_empty_iff [simp]: "image_mset f M = {#} \<longleftrightarrow> M = {#}"
```
```  1625 by (cases M) auto
```
```  1626
```
```  1627 syntax
```
```  1628   "_comprehension1_mset" :: "'a \<Rightarrow> 'b \<Rightarrow> 'b multiset \<Rightarrow> 'a multiset"
```
```  1629       ("({#_/. _ :# _#})")
```
```  1630 translations
```
```  1631   "{#e. x:#M#}" == "CONST image_mset (%x. e) M"
```
```  1632
```
```  1633 syntax
```
```  1634   "_comprehension2_mset" :: "'a \<Rightarrow> 'b \<Rightarrow> 'b multiset \<Rightarrow> bool \<Rightarrow> 'a multiset"
```
```  1635       ("({#_/ | _ :# _./ _#})")
```
```  1636 translations
```
```  1637   "{#e | x:#M. P#}" => "{#e. x :# {# x:#M. P#}#}"
```
```  1638
```
```  1639 text {*
```
```  1640   This allows to write not just filters like @{term "{#x:#M. x<c#}"}
```
```  1641   but also images like @{term "{#x+x. x:#M #}"} and @{term [source]
```
```  1642   "{#x+x|x:#M. x<c#}"}, where the latter is currently displayed as
```
```  1643   @{term "{#x+x|x:#M. x<c#}"}.
```
```  1644 *}
```
```  1645
```
```  1646 enriched_type image_mset: image_mset proof -
```
```  1647   fix f g
```
```  1648   show "image_mset f \<circ> image_mset g = image_mset (f \<circ> g)"
```
```  1649   proof
```
```  1650     fix A
```
```  1651     show "(image_mset f \<circ> image_mset g) A = image_mset (f \<circ> g) A"
```
```  1652       by (induct A) simp_all
```
```  1653   qed
```
```  1654 next
```
```  1655   show "image_mset id = id"
```
```  1656   proof
```
```  1657     fix A
```
```  1658     show "image_mset id A = id A"
```
```  1659       by (induct A) simp_all
```
```  1660   qed
```
```  1661 qed
```
```  1662
```
```  1663
```
```  1664 subsection {* Termination proofs with multiset orders *}
```
```  1665
```
```  1666 lemma multi_member_skip: "x \<in># XS \<Longrightarrow> x \<in># {# y #} + XS"
```
```  1667   and multi_member_this: "x \<in># {# x #} + XS"
```
```  1668   and multi_member_last: "x \<in># {# x #}"
```
```  1669   by auto
```
```  1670
```
```  1671 definition "ms_strict = mult pair_less"
```
```  1672 definition "ms_weak = ms_strict \<union> Id"
```
```  1673
```
```  1674 lemma ms_reduction_pair: "reduction_pair (ms_strict, ms_weak)"
```
```  1675 unfolding reduction_pair_def ms_strict_def ms_weak_def pair_less_def
```
```  1676 by (auto intro: wf_mult1 wf_trancl simp: mult_def)
```
```  1677
```
```  1678 lemma smsI:
```
```  1679   "(set_of A, set_of B) \<in> max_strict \<Longrightarrow> (Z + A, Z + B) \<in> ms_strict"
```
```  1680   unfolding ms_strict_def
```
```  1681 by (rule one_step_implies_mult) (auto simp add: max_strict_def pair_less_def elim!:max_ext.cases)
```
```  1682
```
```  1683 lemma wmsI:
```
```  1684   "(set_of A, set_of B) \<in> max_strict \<or> A = {#} \<and> B = {#}
```
```  1685   \<Longrightarrow> (Z + A, Z + B) \<in> ms_weak"
```
```  1686 unfolding ms_weak_def ms_strict_def
```
```  1687 by (auto simp add: pair_less_def max_strict_def elim!:max_ext.cases intro: one_step_implies_mult)
```
```  1688
```
```  1689 inductive pw_leq
```
```  1690 where
```
```  1691   pw_leq_empty: "pw_leq {#} {#}"
```
```  1692 | pw_leq_step:  "\<lbrakk>(x,y) \<in> pair_leq; pw_leq X Y \<rbrakk> \<Longrightarrow> pw_leq ({#x#} + X) ({#y#} + Y)"
```
```  1693
```
```  1694 lemma pw_leq_lstep:
```
```  1695   "(x, y) \<in> pair_leq \<Longrightarrow> pw_leq {#x#} {#y#}"
```
```  1696 by (drule pw_leq_step) (rule pw_leq_empty, simp)
```
```  1697
```
```  1698 lemma pw_leq_split:
```
```  1699   assumes "pw_leq X Y"
```
```  1700   shows "\<exists>A B Z. X = A + Z \<and> Y = B + Z \<and> ((set_of A, set_of B) \<in> max_strict \<or> (B = {#} \<and> A = {#}))"
```
```  1701   using assms
```
```  1702 proof (induct)
```
```  1703   case pw_leq_empty thus ?case by auto
```
```  1704 next
```
```  1705   case (pw_leq_step x y X Y)
```
```  1706   then obtain A B Z where
```
```  1707     [simp]: "X = A + Z" "Y = B + Z"
```
```  1708       and 1[simp]: "(set_of A, set_of B) \<in> max_strict \<or> (B = {#} \<and> A = {#})"
```
```  1709     by auto
```
```  1710   from pw_leq_step have "x = y \<or> (x, y) \<in> pair_less"
```
```  1711     unfolding pair_leq_def by auto
```
```  1712   thus ?case
```
```  1713   proof
```
```  1714     assume [simp]: "x = y"
```
```  1715     have
```
```  1716       "{#x#} + X = A + ({#y#}+Z)
```
```  1717       \<and> {#y#} + Y = B + ({#y#}+Z)
```
```  1718       \<and> ((set_of A, set_of B) \<in> max_strict \<or> (B = {#} \<and> A = {#}))"
```
```  1719       by (auto simp: add_ac)
```
```  1720     thus ?case by (intro exI)
```
```  1721   next
```
```  1722     assume A: "(x, y) \<in> pair_less"
```
```  1723     let ?A' = "{#x#} + A" and ?B' = "{#y#} + B"
```
```  1724     have "{#x#} + X = ?A' + Z"
```
```  1725       "{#y#} + Y = ?B' + Z"
```
```  1726       by (auto simp add: add_ac)
```
```  1727     moreover have
```
```  1728       "(set_of ?A', set_of ?B') \<in> max_strict"
```
```  1729       using 1 A unfolding max_strict_def
```
```  1730       by (auto elim!: max_ext.cases)
```
```  1731     ultimately show ?thesis by blast
```
```  1732   qed
```
```  1733 qed
```
```  1734
```
```  1735 lemma
```
```  1736   assumes pwleq: "pw_leq Z Z'"
```
```  1737   shows ms_strictI: "(set_of A, set_of B) \<in> max_strict \<Longrightarrow> (Z + A, Z' + B) \<in> ms_strict"
```
```  1738   and   ms_weakI1:  "(set_of A, set_of B) \<in> max_strict \<Longrightarrow> (Z + A, Z' + B) \<in> ms_weak"
```
```  1739   and   ms_weakI2:  "(Z + {#}, Z' + {#}) \<in> ms_weak"
```
```  1740 proof -
```
```  1741   from pw_leq_split[OF pwleq]
```
```  1742   obtain A' B' Z''
```
```  1743     where [simp]: "Z = A' + Z''" "Z' = B' + Z''"
```
```  1744     and mx_or_empty: "(set_of A', set_of B') \<in> max_strict \<or> (A' = {#} \<and> B' = {#})"
```
```  1745     by blast
```
```  1746   {
```
```  1747     assume max: "(set_of A, set_of B) \<in> max_strict"
```
```  1748     from mx_or_empty
```
```  1749     have "(Z'' + (A + A'), Z'' + (B + B')) \<in> ms_strict"
```
```  1750     proof
```
```  1751       assume max': "(set_of A', set_of B') \<in> max_strict"
```
```  1752       with max have "(set_of (A + A'), set_of (B + B')) \<in> max_strict"
```
```  1753         by (auto simp: max_strict_def intro: max_ext_additive)
```
```  1754       thus ?thesis by (rule smsI)
```
```  1755     next
```
```  1756       assume [simp]: "A' = {#} \<and> B' = {#}"
```
```  1757       show ?thesis by (rule smsI) (auto intro: max)
```
```  1758     qed
```
```  1759     thus "(Z + A, Z' + B) \<in> ms_strict" by (simp add:add_ac)
```
```  1760     thus "(Z + A, Z' + B) \<in> ms_weak" by (simp add: ms_weak_def)
```
```  1761   }
```
```  1762   from mx_or_empty
```
```  1763   have "(Z'' + A', Z'' + B') \<in> ms_weak" by (rule wmsI)
```
```  1764   thus "(Z + {#}, Z' + {#}) \<in> ms_weak" by (simp add:add_ac)
```
```  1765 qed
```
```  1766
```
```  1767 lemma empty_neutral: "{#} + x = x" "x + {#} = x"
```
```  1768 and nonempty_plus: "{# x #} + rs \<noteq> {#}"
```
```  1769 and nonempty_single: "{# x #} \<noteq> {#}"
```
```  1770 by auto
```
```  1771
```
```  1772 setup {*
```
```  1773 let
```
```  1774   fun msetT T = Type (@{type_name multiset}, [T]);
```
```  1775
```
```  1776   fun mk_mset T [] = Const (@{const_abbrev Mempty}, msetT T)
```
```  1777     | mk_mset T [x] = Const (@{const_name single}, T --> msetT T) \$ x
```
```  1778     | mk_mset T (x :: xs) =
```
```  1779           Const (@{const_name plus}, msetT T --> msetT T --> msetT T) \$
```
```  1780                 mk_mset T [x] \$ mk_mset T xs
```
```  1781
```
```  1782   fun mset_member_tac m i =
```
```  1783       (if m <= 0 then
```
```  1784            rtac @{thm multi_member_this} i ORELSE rtac @{thm multi_member_last} i
```
```  1785        else
```
```  1786            rtac @{thm multi_member_skip} i THEN mset_member_tac (m - 1) i)
```
```  1787
```
```  1788   val mset_nonempty_tac =
```
```  1789       rtac @{thm nonempty_plus} ORELSE' rtac @{thm nonempty_single}
```
```  1790
```
```  1791   val regroup_munion_conv =
```
```  1792       Function_Lib.regroup_conv @{const_abbrev Mempty} @{const_name plus}
```
```  1793         (map (fn t => t RS eq_reflection) (@{thms add_ac} @ @{thms empty_neutral}))
```
```  1794
```
```  1795   fun unfold_pwleq_tac i =
```
```  1796     (rtac @{thm pw_leq_step} i THEN (fn st => unfold_pwleq_tac (i + 1) st))
```
```  1797       ORELSE (rtac @{thm pw_leq_lstep} i)
```
```  1798       ORELSE (rtac @{thm pw_leq_empty} i)
```
```  1799
```
```  1800   val set_of_simps = [@{thm set_of_empty}, @{thm set_of_single}, @{thm set_of_union},
```
```  1801                       @{thm Un_insert_left}, @{thm Un_empty_left}]
```
```  1802 in
```
```  1803   ScnpReconstruct.multiset_setup (ScnpReconstruct.Multiset
```
```  1804   {
```
```  1805     msetT=msetT, mk_mset=mk_mset, mset_regroup_conv=regroup_munion_conv,
```
```  1806     mset_member_tac=mset_member_tac, mset_nonempty_tac=mset_nonempty_tac,
```
```  1807     mset_pwleq_tac=unfold_pwleq_tac, set_of_simps=set_of_simps,
```
```  1808     smsI'= @{thm ms_strictI}, wmsI2''= @{thm ms_weakI2}, wmsI1= @{thm ms_weakI1},
```
```  1809     reduction_pair= @{thm ms_reduction_pair}
```
```  1810   })
```
```  1811 end
```
```  1812 *}
```
```  1813
```
```  1814
```
```  1815 subsection {* Legacy theorem bindings *}
```
```  1816
```
```  1817 lemmas multi_count_eq = multiset_eq_iff [symmetric]
```
```  1818
```
```  1819 lemma union_commute: "M + N = N + (M::'a multiset)"
```
```  1820   by (fact add_commute)
```
```  1821
```
```  1822 lemma union_assoc: "(M + N) + K = M + (N + (K::'a multiset))"
```
```  1823   by (fact add_assoc)
```
```  1824
```
```  1825 lemma union_lcomm: "M + (N + K) = N + (M + (K::'a multiset))"
```
```  1826   by (fact add_left_commute)
```
```  1827
```
```  1828 lemmas union_ac = union_assoc union_commute union_lcomm
```
```  1829
```
```  1830 lemma union_right_cancel: "M + K = N + K \<longleftrightarrow> M = (N::'a multiset)"
```
```  1831   by (fact add_right_cancel)
```
```  1832
```
```  1833 lemma union_left_cancel: "K + M = K + N \<longleftrightarrow> M = (N::'a multiset)"
```
```  1834   by (fact add_left_cancel)
```
```  1835
```
```  1836 lemma multi_union_self_other_eq: "(A::'a multiset) + X = A + Y \<Longrightarrow> X = Y"
```
```  1837   by (fact add_imp_eq)
```
```  1838
```
```  1839 lemma mset_less_trans: "(M::'a multiset) < K \<Longrightarrow> K < N \<Longrightarrow> M < N"
```
```  1840   by (fact order_less_trans)
```
```  1841
```
```  1842 lemma multiset_inter_commute: "A #\<inter> B = B #\<inter> A"
```
```  1843   by (fact inf.commute)
```
```  1844
```
```  1845 lemma multiset_inter_assoc: "A #\<inter> (B #\<inter> C) = A #\<inter> B #\<inter> C"
```
```  1846   by (fact inf.assoc [symmetric])
```
```  1847
```
```  1848 lemma multiset_inter_left_commute: "A #\<inter> (B #\<inter> C) = B #\<inter> (A #\<inter> C)"
```
```  1849   by (fact inf.left_commute)
```
```  1850
```
```  1851 lemmas multiset_inter_ac =
```
```  1852   multiset_inter_commute
```
```  1853   multiset_inter_assoc
```
```  1854   multiset_inter_left_commute
```
```  1855
```
```  1856 lemma mult_less_not_refl:
```
```  1857   "\<not> M \<subset># (M::'a::order multiset)"
```
```  1858   by (fact multiset_order.less_irrefl)
```
```  1859
```
```  1860 lemma mult_less_trans:
```
```  1861   "K \<subset># M ==> M \<subset># N ==> K \<subset># (N::'a::order multiset)"
```
```  1862   by (fact multiset_order.less_trans)
```
```  1863
```
```  1864 lemma mult_less_not_sym:
```
```  1865   "M \<subset># N ==> \<not> N \<subset># (M::'a::order multiset)"
```
```  1866   by (fact multiset_order.less_not_sym)
```
```  1867
```
```  1868 lemma mult_less_asym:
```
```  1869   "M \<subset># N ==> (\<not> P ==> N \<subset># (M::'a::order multiset)) ==> P"
```
```  1870   by (fact multiset_order.less_asym)
```
```  1871
```
```  1872 ML {*
```
```  1873 fun multiset_postproc _ maybe_name all_values (T as Type (_, [elem_T]))
```
```  1874                       (Const _ \$ t') =
```
```  1875     let
```
```  1876       val (maybe_opt, ps) =
```
```  1877         Nitpick_Model.dest_plain_fun t' ||> op ~~
```
```  1878         ||> map (apsnd (snd o HOLogic.dest_number))
```
```  1879       fun elems_for t =
```
```  1880         case AList.lookup (op =) ps t of
```
```  1881           SOME n => replicate n t
```
```  1882         | NONE => [Const (maybe_name, elem_T --> elem_T) \$ t]
```
```  1883     in
```
```  1884       case maps elems_for (all_values elem_T) @
```
```  1885            (if maybe_opt then [Const (Nitpick_Model.unrep (), elem_T)]
```
```  1886             else []) of
```
```  1887         [] => Const (@{const_name zero_class.zero}, T)
```
```  1888       | ts => foldl1 (fn (t1, t2) =>
```
```  1889                          Const (@{const_name plus_class.plus}, T --> T --> T)
```
```  1890                          \$ t1 \$ t2)
```
```  1891                      (map (curry (op \$) (Const (@{const_name single},
```
```  1892                                                 elem_T --> T))) ts)
```
```  1893     end
```
```  1894   | multiset_postproc _ _ _ _ t = t
```
```  1895 *}
```
```  1896
```
```  1897 declaration {*
```
```  1898 Nitpick_Model.register_term_postprocessor @{typ "'a multiset"}
```
```  1899     multiset_postproc
```
```  1900 *}
```
```  1901
```
```  1902 end
```