src/HOL/Groups_List.thy
 author wenzelm Mon Dec 07 10:38:04 2015 +0100 (2015-12-07) changeset 61799 4cf66f21b764 parent 61776 57bb7da5c867 child 61955 e96292f32c3c permissions -rw-r--r--
isabelle update_cartouches -c -t;
```     1 (* Author: Tobias Nipkow, TU Muenchen *)
```
```     2
```
```     3 section \<open>Sum and product over lists\<close>
```
```     4
```
```     5 theory Groups_List
```
```     6 imports List
```
```     7 begin
```
```     8
```
```     9 no_notation times (infixl "*" 70)
```
```    10 no_notation Groups.one ("1")
```
```    11
```
```    12 locale monoid_list = monoid
```
```    13 begin
```
```    14
```
```    15 definition F :: "'a list \<Rightarrow> 'a"
```
```    16 where
```
```    17   eq_foldr [code]: "F xs = foldr f xs 1"
```
```    18
```
```    19 lemma Nil [simp]:
```
```    20   "F [] = 1"
```
```    21   by (simp add: eq_foldr)
```
```    22
```
```    23 lemma Cons [simp]:
```
```    24   "F (x # xs) = x * F xs"
```
```    25   by (simp add: eq_foldr)
```
```    26
```
```    27 lemma append [simp]:
```
```    28   "F (xs @ ys) = F xs * F ys"
```
```    29   by (induct xs) (simp_all add: assoc)
```
```    30
```
```    31 end
```
```    32
```
```    33 locale comm_monoid_list = comm_monoid + monoid_list
```
```    34 begin
```
```    35
```
```    36 lemma rev [simp]:
```
```    37   "F (rev xs) = F xs"
```
```    38   by (simp add: eq_foldr foldr_fold  fold_rev fun_eq_iff assoc left_commute)
```
```    39
```
```    40 end
```
```    41
```
```    42 locale comm_monoid_list_set = list: comm_monoid_list + set: comm_monoid_set
```
```    43 begin
```
```    44
```
```    45 lemma distinct_set_conv_list:
```
```    46   "distinct xs \<Longrightarrow> set.F g (set xs) = list.F (map g xs)"
```
```    47   by (induct xs) simp_all
```
```    48
```
```    49 lemma set_conv_list [code]:
```
```    50   "set.F g (set xs) = list.F (map g (remdups xs))"
```
```    51   by (simp add: distinct_set_conv_list [symmetric])
```
```    52
```
```    53 end
```
```    54
```
```    55 notation times (infixl "*" 70)
```
```    56 notation Groups.one ("1")
```
```    57
```
```    58
```
```    59 subsection \<open>List summation\<close>
```
```    60
```
```    61 context monoid_add
```
```    62 begin
```
```    63
```
```    64 sublocale listsum: monoid_list plus 0
```
```    65 defines
```
```    66   listsum = listsum.F ..
```
```    67
```
```    68 end
```
```    69
```
```    70 context comm_monoid_add
```
```    71 begin
```
```    72
```
```    73 sublocale listsum: comm_monoid_list plus 0
```
```    74 rewrites
```
```    75   "monoid_list.F plus 0 = listsum"
```
```    76 proof -
```
```    77   show "comm_monoid_list plus 0" ..
```
```    78   then interpret listsum: comm_monoid_list plus 0 .
```
```    79   from listsum_def show "monoid_list.F plus 0 = listsum" by simp
```
```    80 qed
```
```    81
```
```    82 sublocale setsum: comm_monoid_list_set plus 0
```
```    83 rewrites
```
```    84   "monoid_list.F plus 0 = listsum"
```
```    85   and "comm_monoid_set.F plus 0 = setsum"
```
```    86 proof -
```
```    87   show "comm_monoid_list_set plus 0" ..
```
```    88   then interpret setsum: comm_monoid_list_set plus 0 .
```
```    89   from listsum_def show "monoid_list.F plus 0 = listsum" by simp
```
```    90   from setsum_def show "comm_monoid_set.F plus 0 = setsum" by (auto intro: sym)
```
```    91 qed
```
```    92
```
```    93 end
```
```    94
```
```    95 text \<open>Some syntactic sugar for summing a function over a list:\<close>
```
```    96
```
```    97 syntax
```
```    98   "_listsum" :: "pttrn => 'a list => 'b => 'b"    ("(3SUM _<-_. _)" [0, 51, 10] 10)
```
```    99 syntax (xsymbols)
```
```   100   "_listsum" :: "pttrn => 'a list => 'b => 'b"    ("(3\<Sum>_\<leftarrow>_. _)" [0, 51, 10] 10)
```
```   101
```
```   102 translations \<comment> \<open>Beware of argument permutation!\<close>
```
```   103   "SUM x<-xs. b" == "CONST listsum (CONST map (%x. b) xs)"
```
```   104   "\<Sum>x\<leftarrow>xs. b" == "CONST listsum (CONST map (%x. b) xs)"
```
```   105
```
```   106 text \<open>TODO duplicates\<close>
```
```   107 lemmas listsum_simps = listsum.Nil listsum.Cons
```
```   108 lemmas listsum_append = listsum.append
```
```   109 lemmas listsum_rev = listsum.rev
```
```   110
```
```   111 lemma (in monoid_add) fold_plus_listsum_rev:
```
```   112   "fold plus xs = plus (listsum (rev xs))"
```
```   113 proof
```
```   114   fix x
```
```   115   have "fold plus xs x = listsum (rev xs @ [x])"
```
```   116     by (simp add: foldr_conv_fold listsum.eq_foldr)
```
```   117   also have "\<dots> = listsum (rev xs) + x"
```
```   118     by simp
```
```   119   finally show "fold plus xs x = listsum (rev xs) + x"
```
```   120     .
```
```   121 qed
```
```   122
```
```   123 lemma (in comm_monoid_add) listsum_map_remove1:
```
```   124   "x \<in> set xs \<Longrightarrow> listsum (map f xs) = f x + listsum (map f (remove1 x xs))"
```
```   125   by (induct xs) (auto simp add: ac_simps)
```
```   126
```
```   127 lemma (in monoid_add) size_list_conv_listsum:
```
```   128   "size_list f xs = listsum (map f xs) + size xs"
```
```   129   by (induct xs) auto
```
```   130
```
```   131 lemma (in monoid_add) length_concat:
```
```   132   "length (concat xss) = listsum (map length xss)"
```
```   133   by (induct xss) simp_all
```
```   134
```
```   135 lemma (in monoid_add) length_product_lists:
```
```   136   "length (product_lists xss) = foldr op * (map length xss) 1"
```
```   137 proof (induct xss)
```
```   138   case (Cons xs xss) then show ?case by (induct xs) (auto simp: length_concat o_def)
```
```   139 qed simp
```
```   140
```
```   141 lemma (in monoid_add) listsum_map_filter:
```
```   142   assumes "\<And>x. x \<in> set xs \<Longrightarrow> \<not> P x \<Longrightarrow> f x = 0"
```
```   143   shows "listsum (map f (filter P xs)) = listsum (map f xs)"
```
```   144   using assms by (induct xs) auto
```
```   145
```
```   146 lemma (in comm_monoid_add) distinct_listsum_conv_Setsum:
```
```   147   "distinct xs \<Longrightarrow> listsum xs = Setsum (set xs)"
```
```   148   by (induct xs) simp_all
```
```   149
```
```   150 lemma listsum_upt[simp]:
```
```   151   "m \<le> n \<Longrightarrow> listsum [m..<n] = \<Sum> {m..<n}"
```
```   152 by(simp add: distinct_listsum_conv_Setsum)
```
```   153
```
```   154 lemma listsum_eq_0_nat_iff_nat [simp]:
```
```   155   "listsum ns = (0::nat) \<longleftrightarrow> (\<forall>n \<in> set ns. n = 0)"
```
```   156   by (induct ns) simp_all
```
```   157
```
```   158 lemma member_le_listsum_nat:
```
```   159   "(n :: nat) \<in> set ns \<Longrightarrow> n \<le> listsum ns"
```
```   160   by (induct ns) auto
```
```   161
```
```   162 lemma elem_le_listsum_nat:
```
```   163   "k < size ns \<Longrightarrow> ns ! k \<le> listsum (ns::nat list)"
```
```   164   by (rule member_le_listsum_nat) simp
```
```   165
```
```   166 lemma listsum_update_nat:
```
```   167   "k < size ns \<Longrightarrow> listsum (ns[k := (n::nat)]) = listsum ns + n - ns ! k"
```
```   168 apply(induct ns arbitrary:k)
```
```   169  apply (auto split:nat.split)
```
```   170 apply(drule elem_le_listsum_nat)
```
```   171 apply arith
```
```   172 done
```
```   173
```
```   174 lemma (in monoid_add) listsum_triv:
```
```   175   "(\<Sum>x\<leftarrow>xs. r) = of_nat (length xs) * r"
```
```   176   by (induct xs) (simp_all add: distrib_right)
```
```   177
```
```   178 lemma (in monoid_add) listsum_0 [simp]:
```
```   179   "(\<Sum>x\<leftarrow>xs. 0) = 0"
```
```   180   by (induct xs) (simp_all add: distrib_right)
```
```   181
```
```   182 text\<open>For non-Abelian groups \<open>xs\<close> needs to be reversed on one side:\<close>
```
```   183 lemma (in ab_group_add) uminus_listsum_map:
```
```   184   "- listsum (map f xs) = listsum (map (uminus \<circ> f) xs)"
```
```   185   by (induct xs) simp_all
```
```   186
```
```   187 lemma (in comm_monoid_add) listsum_addf:
```
```   188   "(\<Sum>x\<leftarrow>xs. f x + g x) = listsum (map f xs) + listsum (map g xs)"
```
```   189   by (induct xs) (simp_all add: algebra_simps)
```
```   190
```
```   191 lemma (in ab_group_add) listsum_subtractf:
```
```   192   "(\<Sum>x\<leftarrow>xs. f x - g x) = listsum (map f xs) - listsum (map g xs)"
```
```   193   by (induct xs) (simp_all add: algebra_simps)
```
```   194
```
```   195 lemma (in semiring_0) listsum_const_mult:
```
```   196   "(\<Sum>x\<leftarrow>xs. c * f x) = c * (\<Sum>x\<leftarrow>xs. f x)"
```
```   197   by (induct xs) (simp_all add: algebra_simps)
```
```   198
```
```   199 lemma (in semiring_0) listsum_mult_const:
```
```   200   "(\<Sum>x\<leftarrow>xs. f x * c) = (\<Sum>x\<leftarrow>xs. f x) * c"
```
```   201   by (induct xs) (simp_all add: algebra_simps)
```
```   202
```
```   203 lemma (in ordered_ab_group_add_abs) listsum_abs:
```
```   204   "\<bar>listsum xs\<bar> \<le> listsum (map abs xs)"
```
```   205   by (induct xs) (simp_all add: order_trans [OF abs_triangle_ineq])
```
```   206
```
```   207 lemma listsum_mono:
```
```   208   fixes f g :: "'a \<Rightarrow> 'b::{monoid_add, ordered_ab_semigroup_add}"
```
```   209   shows "(\<And>x. x \<in> set xs \<Longrightarrow> f x \<le> g x) \<Longrightarrow> (\<Sum>x\<leftarrow>xs. f x) \<le> (\<Sum>x\<leftarrow>xs. g x)"
```
```   210   by (induct xs) (simp, simp add: add_mono)
```
```   211
```
```   212 lemma (in monoid_add) listsum_distinct_conv_setsum_set:
```
```   213   "distinct xs \<Longrightarrow> listsum (map f xs) = setsum f (set xs)"
```
```   214   by (induct xs) simp_all
```
```   215
```
```   216 lemma (in monoid_add) interv_listsum_conv_setsum_set_nat:
```
```   217   "listsum (map f [m..<n]) = setsum f (set [m..<n])"
```
```   218   by (simp add: listsum_distinct_conv_setsum_set)
```
```   219
```
```   220 lemma (in monoid_add) interv_listsum_conv_setsum_set_int:
```
```   221   "listsum (map f [k..l]) = setsum f (set [k..l])"
```
```   222   by (simp add: listsum_distinct_conv_setsum_set)
```
```   223
```
```   224 text \<open>General equivalence between @{const listsum} and @{const setsum}\<close>
```
```   225 lemma (in monoid_add) listsum_setsum_nth:
```
```   226   "listsum xs = (\<Sum> i = 0 ..< length xs. xs ! i)"
```
```   227   using interv_listsum_conv_setsum_set_nat [of "op ! xs" 0 "length xs"] by (simp add: map_nth)
```
```   228
```
```   229 lemma listsum_map_eq_setsum_count:
```
```   230   "listsum (map f xs) = setsum (\<lambda>x. count_list xs x * f x) (set xs)"
```
```   231 proof(induction xs)
```
```   232   case (Cons x xs)
```
```   233   show ?case (is "?l = ?r")
```
```   234   proof cases
```
```   235     assume "x \<in> set xs"
```
```   236     have "?l = f x + (\<Sum>x\<in>set xs. count_list xs x * f x)" by (simp add: Cons.IH)
```
```   237     also have "set xs = insert x (set xs - {x})" using \<open>x \<in> set xs\<close>by blast
```
```   238     also have "f x + (\<Sum>x\<in>insert x (set xs - {x}). count_list xs x * f x) = ?r"
```
```   239       by (simp add: setsum.insert_remove eq_commute)
```
```   240     finally show ?thesis .
```
```   241   next
```
```   242     assume "x \<notin> set xs"
```
```   243     hence "\<And>xa. xa \<in> set xs \<Longrightarrow> x \<noteq> xa" by blast
```
```   244     thus ?thesis by (simp add: Cons.IH \<open>x \<notin> set xs\<close>)
```
```   245   qed
```
```   246 qed simp
```
```   247
```
```   248 lemma listsum_map_eq_setsum_count2:
```
```   249 assumes "set xs \<subseteq> X" "finite X"
```
```   250 shows "listsum (map f xs) = setsum (\<lambda>x. count_list xs x * f x) X"
```
```   251 proof-
```
```   252   let ?F = "\<lambda>x. count_list xs x * f x"
```
```   253   have "setsum ?F X = setsum ?F (set xs \<union> (X - set xs))"
```
```   254     using Un_absorb1[OF assms(1)] by(simp)
```
```   255   also have "\<dots> = setsum ?F (set xs)"
```
```   256     using assms(2)
```
```   257     by(simp add: setsum.union_disjoint[OF _ _ Diff_disjoint] del: Un_Diff_cancel)
```
```   258   finally show ?thesis by(simp add:listsum_map_eq_setsum_count)
```
```   259 qed
```
```   260
```
```   261
```
```   262 subsection \<open>Further facts about @{const List.n_lists}\<close>
```
```   263
```
```   264 lemma length_n_lists: "length (List.n_lists n xs) = length xs ^ n"
```
```   265   by (induct n) (auto simp add: comp_def length_concat listsum_triv)
```
```   266
```
```   267 lemma distinct_n_lists:
```
```   268   assumes "distinct xs"
```
```   269   shows "distinct (List.n_lists n xs)"
```
```   270 proof (rule card_distinct)
```
```   271   from assms have card_length: "card (set xs) = length xs" by (rule distinct_card)
```
```   272   have "card (set (List.n_lists n xs)) = card (set xs) ^ n"
```
```   273   proof (induct n)
```
```   274     case 0 then show ?case by simp
```
```   275   next
```
```   276     case (Suc n)
```
```   277     moreover have "card (\<Union>ys\<in>set (List.n_lists n xs). (\<lambda>y. y # ys) ` set xs)
```
```   278       = (\<Sum>ys\<in>set (List.n_lists n xs). card ((\<lambda>y. y # ys) ` set xs))"
```
```   279       by (rule card_UN_disjoint) auto
```
```   280     moreover have "\<And>ys. card ((\<lambda>y. y # ys) ` set xs) = card (set xs)"
```
```   281       by (rule card_image) (simp add: inj_on_def)
```
```   282     ultimately show ?case by auto
```
```   283   qed
```
```   284   also have "\<dots> = length xs ^ n" by (simp add: card_length)
```
```   285   finally show "card (set (List.n_lists n xs)) = length (List.n_lists n xs)"
```
```   286     by (simp add: length_n_lists)
```
```   287 qed
```
```   288
```
```   289
```
```   290 subsection \<open>Tools setup\<close>
```
```   291
```
```   292 lemmas setsum_code = setsum.set_conv_list
```
```   293
```
```   294 lemma setsum_set_upto_conv_listsum_int [code_unfold]:
```
```   295   "setsum f (set [i..j::int]) = listsum (map f [i..j])"
```
```   296   by (simp add: interv_listsum_conv_setsum_set_int)
```
```   297
```
```   298 lemma setsum_set_upt_conv_listsum_nat [code_unfold]:
```
```   299   "setsum f (set [m..<n]) = listsum (map f [m..<n])"
```
```   300   by (simp add: interv_listsum_conv_setsum_set_nat)
```
```   301
```
```   302 context
```
```   303 begin
```
```   304
```
```   305 interpretation lifting_syntax .
```
```   306
```
```   307 lemma listsum_transfer[transfer_rule]:
```
```   308   assumes [transfer_rule]: "A 0 0"
```
```   309   assumes [transfer_rule]: "(A ===> A ===> A) op + op +"
```
```   310   shows "(list_all2 A ===> A) listsum listsum"
```
```   311   unfolding listsum.eq_foldr [abs_def]
```
```   312   by transfer_prover
```
```   313
```
```   314 end
```
```   315
```
```   316
```
```   317 subsection \<open>List product\<close>
```
```   318
```
```   319 context monoid_mult
```
```   320 begin
```
```   321
```
```   322 sublocale listprod: monoid_list times 1
```
```   323 defines
```
```   324   listprod = listprod.F ..
```
```   325
```
```   326 end
```
```   327
```
```   328 context comm_monoid_mult
```
```   329 begin
```
```   330
```
```   331 sublocale listprod: comm_monoid_list times 1
```
```   332 rewrites
```
```   333   "monoid_list.F times 1 = listprod"
```
```   334 proof -
```
```   335   show "comm_monoid_list times 1" ..
```
```   336   then interpret listprod: comm_monoid_list times 1 .
```
```   337   from listprod_def show "monoid_list.F times 1 = listprod" by simp
```
```   338 qed
```
```   339
```
```   340 sublocale setprod: comm_monoid_list_set times 1
```
```   341 rewrites
```
```   342   "monoid_list.F times 1 = listprod"
```
```   343   and "comm_monoid_set.F times 1 = setprod"
```
```   344 proof -
```
```   345   show "comm_monoid_list_set times 1" ..
```
```   346   then interpret setprod: comm_monoid_list_set times 1 .
```
```   347   from listprod_def show "monoid_list.F times 1 = listprod" by simp
```
```   348   from setprod_def show "comm_monoid_set.F times 1 = setprod" by (auto intro: sym)
```
```   349 qed
```
```   350
```
```   351 end
```
```   352
```
```   353 text \<open>Some syntactic sugar:\<close>
```
```   354
```
```   355 syntax
```
```   356   "_listprod" :: "pttrn => 'a list => 'b => 'b"    ("(3PROD _<-_. _)" [0, 51, 10] 10)
```
```   357 syntax (xsymbols)
```
```   358   "_listprod" :: "pttrn => 'a list => 'b => 'b"    ("(3\<Prod>_\<leftarrow>_. _)" [0, 51, 10] 10)
```
```   359
```
```   360 translations \<comment> \<open>Beware of argument permutation!\<close>
```
```   361   "PROD x<-xs. b" == "CONST listprod (CONST map (%x. b) xs)"
```
```   362   "\<Prod>x\<leftarrow>xs. b" == "CONST listprod (CONST map (%x. b) xs)"
```
```   363
```
```   364 end
```