src/HOL/Limits.thy
 author Christian Sternagel Thu Aug 30 15:44:03 2012 +0900 (2012-08-30) changeset 49093 fdc301f592c4 parent 47432 e1576d13e933 child 49834 b27bbb021df1 permissions -rw-r--r--
```     1 (*  Title       : Limits.thy
```
```     2     Author      : Brian Huffman
```
```     3 *)
```
```     4
```
```     5 header {* Filters and Limits *}
```
```     6
```
```     7 theory Limits
```
```     8 imports RealVector
```
```     9 begin
```
```    10
```
```    11 subsection {* Filters *}
```
```    12
```
```    13 text {*
```
```    14   This definition also allows non-proper filters.
```
```    15 *}
```
```    16
```
```    17 locale is_filter =
```
```    18   fixes F :: "('a \<Rightarrow> bool) \<Rightarrow> bool"
```
```    19   assumes True: "F (\<lambda>x. True)"
```
```    20   assumes conj: "F (\<lambda>x. P x) \<Longrightarrow> F (\<lambda>x. Q x) \<Longrightarrow> F (\<lambda>x. P x \<and> Q x)"
```
```    21   assumes mono: "\<forall>x. P x \<longrightarrow> Q x \<Longrightarrow> F (\<lambda>x. P x) \<Longrightarrow> F (\<lambda>x. Q x)"
```
```    22
```
```    23 typedef (open) 'a filter = "{F :: ('a \<Rightarrow> bool) \<Rightarrow> bool. is_filter F}"
```
```    24 proof
```
```    25   show "(\<lambda>x. True) \<in> ?filter" by (auto intro: is_filter.intro)
```
```    26 qed
```
```    27
```
```    28 lemma is_filter_Rep_filter: "is_filter (Rep_filter F)"
```
```    29   using Rep_filter [of F] by simp
```
```    30
```
```    31 lemma Abs_filter_inverse':
```
```    32   assumes "is_filter F" shows "Rep_filter (Abs_filter F) = F"
```
```    33   using assms by (simp add: Abs_filter_inverse)
```
```    34
```
```    35
```
```    36 subsection {* Eventually *}
```
```    37
```
```    38 definition eventually :: "('a \<Rightarrow> bool) \<Rightarrow> 'a filter \<Rightarrow> bool"
```
```    39   where "eventually P F \<longleftrightarrow> Rep_filter F P"
```
```    40
```
```    41 lemma eventually_Abs_filter:
```
```    42   assumes "is_filter F" shows "eventually P (Abs_filter F) = F P"
```
```    43   unfolding eventually_def using assms by (simp add: Abs_filter_inverse)
```
```    44
```
```    45 lemma filter_eq_iff:
```
```    46   shows "F = F' \<longleftrightarrow> (\<forall>P. eventually P F = eventually P F')"
```
```    47   unfolding Rep_filter_inject [symmetric] fun_eq_iff eventually_def ..
```
```    48
```
```    49 lemma eventually_True [simp]: "eventually (\<lambda>x. True) F"
```
```    50   unfolding eventually_def
```
```    51   by (rule is_filter.True [OF is_filter_Rep_filter])
```
```    52
```
```    53 lemma always_eventually: "\<forall>x. P x \<Longrightarrow> eventually P F"
```
```    54 proof -
```
```    55   assume "\<forall>x. P x" hence "P = (\<lambda>x. True)" by (simp add: ext)
```
```    56   thus "eventually P F" by simp
```
```    57 qed
```
```    58
```
```    59 lemma eventually_mono:
```
```    60   "(\<forall>x. P x \<longrightarrow> Q x) \<Longrightarrow> eventually P F \<Longrightarrow> eventually Q F"
```
```    61   unfolding eventually_def
```
```    62   by (rule is_filter.mono [OF is_filter_Rep_filter])
```
```    63
```
```    64 lemma eventually_conj:
```
```    65   assumes P: "eventually (\<lambda>x. P x) F"
```
```    66   assumes Q: "eventually (\<lambda>x. Q x) F"
```
```    67   shows "eventually (\<lambda>x. P x \<and> Q x) F"
```
```    68   using assms unfolding eventually_def
```
```    69   by (rule is_filter.conj [OF is_filter_Rep_filter])
```
```    70
```
```    71 lemma eventually_mp:
```
```    72   assumes "eventually (\<lambda>x. P x \<longrightarrow> Q x) F"
```
```    73   assumes "eventually (\<lambda>x. P x) F"
```
```    74   shows "eventually (\<lambda>x. Q x) F"
```
```    75 proof (rule eventually_mono)
```
```    76   show "\<forall>x. (P x \<longrightarrow> Q x) \<and> P x \<longrightarrow> Q x" by simp
```
```    77   show "eventually (\<lambda>x. (P x \<longrightarrow> Q x) \<and> P x) F"
```
```    78     using assms by (rule eventually_conj)
```
```    79 qed
```
```    80
```
```    81 lemma eventually_rev_mp:
```
```    82   assumes "eventually (\<lambda>x. P x) F"
```
```    83   assumes "eventually (\<lambda>x. P x \<longrightarrow> Q x) F"
```
```    84   shows "eventually (\<lambda>x. Q x) F"
```
```    85 using assms(2) assms(1) by (rule eventually_mp)
```
```    86
```
```    87 lemma eventually_conj_iff:
```
```    88   "eventually (\<lambda>x. P x \<and> Q x) F \<longleftrightarrow> eventually P F \<and> eventually Q F"
```
```    89   by (auto intro: eventually_conj elim: eventually_rev_mp)
```
```    90
```
```    91 lemma eventually_elim1:
```
```    92   assumes "eventually (\<lambda>i. P i) F"
```
```    93   assumes "\<And>i. P i \<Longrightarrow> Q i"
```
```    94   shows "eventually (\<lambda>i. Q i) F"
```
```    95   using assms by (auto elim!: eventually_rev_mp)
```
```    96
```
```    97 lemma eventually_elim2:
```
```    98   assumes "eventually (\<lambda>i. P i) F"
```
```    99   assumes "eventually (\<lambda>i. Q i) F"
```
```   100   assumes "\<And>i. P i \<Longrightarrow> Q i \<Longrightarrow> R i"
```
```   101   shows "eventually (\<lambda>i. R i) F"
```
```   102   using assms by (auto elim!: eventually_rev_mp)
```
```   103
```
```   104 lemma eventually_subst:
```
```   105   assumes "eventually (\<lambda>n. P n = Q n) F"
```
```   106   shows "eventually P F = eventually Q F" (is "?L = ?R")
```
```   107 proof -
```
```   108   from assms have "eventually (\<lambda>x. P x \<longrightarrow> Q x) F"
```
```   109       and "eventually (\<lambda>x. Q x \<longrightarrow> P x) F"
```
```   110     by (auto elim: eventually_elim1)
```
```   111   then show ?thesis by (auto elim: eventually_elim2)
```
```   112 qed
```
```   113
```
```   114 ML {*
```
```   115   fun eventually_elim_tac ctxt thms thm =
```
```   116     let
```
```   117       val thy = Proof_Context.theory_of ctxt
```
```   118       val mp_thms = thms RL [@{thm eventually_rev_mp}]
```
```   119       val raw_elim_thm =
```
```   120         (@{thm allI} RS @{thm always_eventually})
```
```   121         |> fold (fn thm1 => fn thm2 => thm2 RS thm1) mp_thms
```
```   122         |> fold (fn _ => fn thm => @{thm impI} RS thm) thms
```
```   123       val cases_prop = prop_of (raw_elim_thm RS thm)
```
```   124       val cases = (Rule_Cases.make_common (thy, cases_prop) [(("elim", []), [])])
```
```   125     in
```
```   126       CASES cases (rtac raw_elim_thm 1) thm
```
```   127     end
```
```   128 *}
```
```   129
```
```   130 method_setup eventually_elim = {*
```
```   131   Scan.succeed (fn ctxt => METHOD_CASES (eventually_elim_tac ctxt))
```
```   132 *} "elimination of eventually quantifiers"
```
```   133
```
```   134
```
```   135 subsection {* Finer-than relation *}
```
```   136
```
```   137 text {* @{term "F \<le> F'"} means that filter @{term F} is finer than
```
```   138 filter @{term F'}. *}
```
```   139
```
```   140 instantiation filter :: (type) complete_lattice
```
```   141 begin
```
```   142
```
```   143 definition le_filter_def:
```
```   144   "F \<le> F' \<longleftrightarrow> (\<forall>P. eventually P F' \<longrightarrow> eventually P F)"
```
```   145
```
```   146 definition
```
```   147   "(F :: 'a filter) < F' \<longleftrightarrow> F \<le> F' \<and> \<not> F' \<le> F"
```
```   148
```
```   149 definition
```
```   150   "top = Abs_filter (\<lambda>P. \<forall>x. P x)"
```
```   151
```
```   152 definition
```
```   153   "bot = Abs_filter (\<lambda>P. True)"
```
```   154
```
```   155 definition
```
```   156   "sup F F' = Abs_filter (\<lambda>P. eventually P F \<and> eventually P F')"
```
```   157
```
```   158 definition
```
```   159   "inf F F' = Abs_filter
```
```   160       (\<lambda>P. \<exists>Q R. eventually Q F \<and> eventually R F' \<and> (\<forall>x. Q x \<and> R x \<longrightarrow> P x))"
```
```   161
```
```   162 definition
```
```   163   "Sup S = Abs_filter (\<lambda>P. \<forall>F\<in>S. eventually P F)"
```
```   164
```
```   165 definition
```
```   166   "Inf S = Sup {F::'a filter. \<forall>F'\<in>S. F \<le> F'}"
```
```   167
```
```   168 lemma eventually_top [simp]: "eventually P top \<longleftrightarrow> (\<forall>x. P x)"
```
```   169   unfolding top_filter_def
```
```   170   by (rule eventually_Abs_filter, rule is_filter.intro, auto)
```
```   171
```
```   172 lemma eventually_bot [simp]: "eventually P bot"
```
```   173   unfolding bot_filter_def
```
```   174   by (subst eventually_Abs_filter, rule is_filter.intro, auto)
```
```   175
```
```   176 lemma eventually_sup:
```
```   177   "eventually P (sup F F') \<longleftrightarrow> eventually P F \<and> eventually P F'"
```
```   178   unfolding sup_filter_def
```
```   179   by (rule eventually_Abs_filter, rule is_filter.intro)
```
```   180      (auto elim!: eventually_rev_mp)
```
```   181
```
```   182 lemma eventually_inf:
```
```   183   "eventually P (inf F F') \<longleftrightarrow>
```
```   184    (\<exists>Q R. eventually Q F \<and> eventually R F' \<and> (\<forall>x. Q x \<and> R x \<longrightarrow> P x))"
```
```   185   unfolding inf_filter_def
```
```   186   apply (rule eventually_Abs_filter, rule is_filter.intro)
```
```   187   apply (fast intro: eventually_True)
```
```   188   apply clarify
```
```   189   apply (intro exI conjI)
```
```   190   apply (erule (1) eventually_conj)
```
```   191   apply (erule (1) eventually_conj)
```
```   192   apply simp
```
```   193   apply auto
```
```   194   done
```
```   195
```
```   196 lemma eventually_Sup:
```
```   197   "eventually P (Sup S) \<longleftrightarrow> (\<forall>F\<in>S. eventually P F)"
```
```   198   unfolding Sup_filter_def
```
```   199   apply (rule eventually_Abs_filter, rule is_filter.intro)
```
```   200   apply (auto intro: eventually_conj elim!: eventually_rev_mp)
```
```   201   done
```
```   202
```
```   203 instance proof
```
```   204   fix F F' F'' :: "'a filter" and S :: "'a filter set"
```
```   205   { show "F < F' \<longleftrightarrow> F \<le> F' \<and> \<not> F' \<le> F"
```
```   206     by (rule less_filter_def) }
```
```   207   { show "F \<le> F"
```
```   208     unfolding le_filter_def by simp }
```
```   209   { assume "F \<le> F'" and "F' \<le> F''" thus "F \<le> F''"
```
```   210     unfolding le_filter_def by simp }
```
```   211   { assume "F \<le> F'" and "F' \<le> F" thus "F = F'"
```
```   212     unfolding le_filter_def filter_eq_iff by fast }
```
```   213   { show "F \<le> top"
```
```   214     unfolding le_filter_def eventually_top by (simp add: always_eventually) }
```
```   215   { show "bot \<le> F"
```
```   216     unfolding le_filter_def by simp }
```
```   217   { show "F \<le> sup F F'" and "F' \<le> sup F F'"
```
```   218     unfolding le_filter_def eventually_sup by simp_all }
```
```   219   { assume "F \<le> F''" and "F' \<le> F''" thus "sup F F' \<le> F''"
```
```   220     unfolding le_filter_def eventually_sup by simp }
```
```   221   { show "inf F F' \<le> F" and "inf F F' \<le> F'"
```
```   222     unfolding le_filter_def eventually_inf by (auto intro: eventually_True) }
```
```   223   { assume "F \<le> F'" and "F \<le> F''" thus "F \<le> inf F' F''"
```
```   224     unfolding le_filter_def eventually_inf
```
```   225     by (auto elim!: eventually_mono intro: eventually_conj) }
```
```   226   { assume "F \<in> S" thus "F \<le> Sup S"
```
```   227     unfolding le_filter_def eventually_Sup by simp }
```
```   228   { assume "\<And>F. F \<in> S \<Longrightarrow> F \<le> F'" thus "Sup S \<le> F'"
```
```   229     unfolding le_filter_def eventually_Sup by simp }
```
```   230   { assume "F'' \<in> S" thus "Inf S \<le> F''"
```
```   231     unfolding le_filter_def Inf_filter_def eventually_Sup Ball_def by simp }
```
```   232   { assume "\<And>F'. F' \<in> S \<Longrightarrow> F \<le> F'" thus "F \<le> Inf S"
```
```   233     unfolding le_filter_def Inf_filter_def eventually_Sup Ball_def by simp }
```
```   234 qed
```
```   235
```
```   236 end
```
```   237
```
```   238 lemma filter_leD:
```
```   239   "F \<le> F' \<Longrightarrow> eventually P F' \<Longrightarrow> eventually P F"
```
```   240   unfolding le_filter_def by simp
```
```   241
```
```   242 lemma filter_leI:
```
```   243   "(\<And>P. eventually P F' \<Longrightarrow> eventually P F) \<Longrightarrow> F \<le> F'"
```
```   244   unfolding le_filter_def by simp
```
```   245
```
```   246 lemma eventually_False:
```
```   247   "eventually (\<lambda>x. False) F \<longleftrightarrow> F = bot"
```
```   248   unfolding filter_eq_iff by (auto elim: eventually_rev_mp)
```
```   249
```
```   250 abbreviation (input) trivial_limit :: "'a filter \<Rightarrow> bool"
```
```   251   where "trivial_limit F \<equiv> F = bot"
```
```   252
```
```   253 lemma trivial_limit_def: "trivial_limit F \<longleftrightarrow> eventually (\<lambda>x. False) F"
```
```   254   by (rule eventually_False [symmetric])
```
```   255
```
```   256
```
```   257 subsection {* Map function for filters *}
```
```   258
```
```   259 definition filtermap :: "('a \<Rightarrow> 'b) \<Rightarrow> 'a filter \<Rightarrow> 'b filter"
```
```   260   where "filtermap f F = Abs_filter (\<lambda>P. eventually (\<lambda>x. P (f x)) F)"
```
```   261
```
```   262 lemma eventually_filtermap:
```
```   263   "eventually P (filtermap f F) = eventually (\<lambda>x. P (f x)) F"
```
```   264   unfolding filtermap_def
```
```   265   apply (rule eventually_Abs_filter)
```
```   266   apply (rule is_filter.intro)
```
```   267   apply (auto elim!: eventually_rev_mp)
```
```   268   done
```
```   269
```
```   270 lemma filtermap_ident: "filtermap (\<lambda>x. x) F = F"
```
```   271   by (simp add: filter_eq_iff eventually_filtermap)
```
```   272
```
```   273 lemma filtermap_filtermap:
```
```   274   "filtermap f (filtermap g F) = filtermap (\<lambda>x. f (g x)) F"
```
```   275   by (simp add: filter_eq_iff eventually_filtermap)
```
```   276
```
```   277 lemma filtermap_mono: "F \<le> F' \<Longrightarrow> filtermap f F \<le> filtermap f F'"
```
```   278   unfolding le_filter_def eventually_filtermap by simp
```
```   279
```
```   280 lemma filtermap_bot [simp]: "filtermap f bot = bot"
```
```   281   by (simp add: filter_eq_iff eventually_filtermap)
```
```   282
```
```   283
```
```   284 subsection {* Sequentially *}
```
```   285
```
```   286 definition sequentially :: "nat filter"
```
```   287   where "sequentially = Abs_filter (\<lambda>P. \<exists>k. \<forall>n\<ge>k. P n)"
```
```   288
```
```   289 lemma eventually_sequentially:
```
```   290   "eventually P sequentially \<longleftrightarrow> (\<exists>N. \<forall>n\<ge>N. P n)"
```
```   291 unfolding sequentially_def
```
```   292 proof (rule eventually_Abs_filter, rule is_filter.intro)
```
```   293   fix P Q :: "nat \<Rightarrow> bool"
```
```   294   assume "\<exists>i. \<forall>n\<ge>i. P n" and "\<exists>j. \<forall>n\<ge>j. Q n"
```
```   295   then obtain i j where "\<forall>n\<ge>i. P n" and "\<forall>n\<ge>j. Q n" by auto
```
```   296   then have "\<forall>n\<ge>max i j. P n \<and> Q n" by simp
```
```   297   then show "\<exists>k. \<forall>n\<ge>k. P n \<and> Q n" ..
```
```   298 qed auto
```
```   299
```
```   300 lemma sequentially_bot [simp, intro]: "sequentially \<noteq> bot"
```
```   301   unfolding filter_eq_iff eventually_sequentially by auto
```
```   302
```
```   303 lemmas trivial_limit_sequentially = sequentially_bot
```
```   304
```
```   305 lemma eventually_False_sequentially [simp]:
```
```   306   "\<not> eventually (\<lambda>n. False) sequentially"
```
```   307   by (simp add: eventually_False)
```
```   308
```
```   309 lemma le_sequentially:
```
```   310   "F \<le> sequentially \<longleftrightarrow> (\<forall>N. eventually (\<lambda>n. N \<le> n) F)"
```
```   311   unfolding le_filter_def eventually_sequentially
```
```   312   by (safe, fast, drule_tac x=N in spec, auto elim: eventually_rev_mp)
```
```   313
```
```   314 lemma eventually_sequentiallyI:
```
```   315   assumes "\<And>x. c \<le> x \<Longrightarrow> P x"
```
```   316   shows "eventually P sequentially"
```
```   317 using assms by (auto simp: eventually_sequentially)
```
```   318
```
```   319
```
```   320 subsection {* Standard filters *}
```
```   321
```
```   322 definition within :: "'a filter \<Rightarrow> 'a set \<Rightarrow> 'a filter" (infixr "within" 70)
```
```   323   where "F within S = Abs_filter (\<lambda>P. eventually (\<lambda>x. x \<in> S \<longrightarrow> P x) F)"
```
```   324
```
```   325 definition (in topological_space) nhds :: "'a \<Rightarrow> 'a filter"
```
```   326   where "nhds a = Abs_filter (\<lambda>P. \<exists>S. open S \<and> a \<in> S \<and> (\<forall>x\<in>S. P x))"
```
```   327
```
```   328 definition (in topological_space) at :: "'a \<Rightarrow> 'a filter"
```
```   329   where "at a = nhds a within - {a}"
```
```   330
```
```   331 lemma eventually_within:
```
```   332   "eventually P (F within S) = eventually (\<lambda>x. x \<in> S \<longrightarrow> P x) F"
```
```   333   unfolding within_def
```
```   334   by (rule eventually_Abs_filter, rule is_filter.intro)
```
```   335      (auto elim!: eventually_rev_mp)
```
```   336
```
```   337 lemma within_UNIV [simp]: "F within UNIV = F"
```
```   338   unfolding filter_eq_iff eventually_within by simp
```
```   339
```
```   340 lemma within_empty [simp]: "F within {} = bot"
```
```   341   unfolding filter_eq_iff eventually_within by simp
```
```   342
```
```   343 lemma eventually_nhds:
```
```   344   "eventually P (nhds a) \<longleftrightarrow> (\<exists>S. open S \<and> a \<in> S \<and> (\<forall>x\<in>S. P x))"
```
```   345 unfolding nhds_def
```
```   346 proof (rule eventually_Abs_filter, rule is_filter.intro)
```
```   347   have "open UNIV \<and> a \<in> UNIV \<and> (\<forall>x\<in>UNIV. True)" by simp
```
```   348   thus "\<exists>S. open S \<and> a \<in> S \<and> (\<forall>x\<in>S. True)" by - rule
```
```   349 next
```
```   350   fix P Q
```
```   351   assume "\<exists>S. open S \<and> a \<in> S \<and> (\<forall>x\<in>S. P x)"
```
```   352      and "\<exists>T. open T \<and> a \<in> T \<and> (\<forall>x\<in>T. Q x)"
```
```   353   then obtain S T where
```
```   354     "open S \<and> a \<in> S \<and> (\<forall>x\<in>S. P x)"
```
```   355     "open T \<and> a \<in> T \<and> (\<forall>x\<in>T. Q x)" by auto
```
```   356   hence "open (S \<inter> T) \<and> a \<in> S \<inter> T \<and> (\<forall>x\<in>(S \<inter> T). P x \<and> Q x)"
```
```   357     by (simp add: open_Int)
```
```   358   thus "\<exists>S. open S \<and> a \<in> S \<and> (\<forall>x\<in>S. P x \<and> Q x)" by - rule
```
```   359 qed auto
```
```   360
```
```   361 lemma eventually_nhds_metric:
```
```   362   "eventually P (nhds a) \<longleftrightarrow> (\<exists>d>0. \<forall>x. dist x a < d \<longrightarrow> P x)"
```
```   363 unfolding eventually_nhds open_dist
```
```   364 apply safe
```
```   365 apply fast
```
```   366 apply (rule_tac x="{x. dist x a < d}" in exI, simp)
```
```   367 apply clarsimp
```
```   368 apply (rule_tac x="d - dist x a" in exI, clarsimp)
```
```   369 apply (simp only: less_diff_eq)
```
```   370 apply (erule le_less_trans [OF dist_triangle])
```
```   371 done
```
```   372
```
```   373 lemma nhds_neq_bot [simp]: "nhds a \<noteq> bot"
```
```   374   unfolding trivial_limit_def eventually_nhds by simp
```
```   375
```
```   376 lemma eventually_at_topological:
```
```   377   "eventually P (at a) \<longleftrightarrow> (\<exists>S. open S \<and> a \<in> S \<and> (\<forall>x\<in>S. x \<noteq> a \<longrightarrow> P x))"
```
```   378 unfolding at_def eventually_within eventually_nhds by simp
```
```   379
```
```   380 lemma eventually_at:
```
```   381   fixes a :: "'a::metric_space"
```
```   382   shows "eventually P (at a) \<longleftrightarrow> (\<exists>d>0. \<forall>x. x \<noteq> a \<and> dist x a < d \<longrightarrow> P x)"
```
```   383 unfolding at_def eventually_within eventually_nhds_metric by auto
```
```   384
```
```   385 lemma at_eq_bot_iff: "at a = bot \<longleftrightarrow> open {a}"
```
```   386   unfolding trivial_limit_def eventually_at_topological
```
```   387   by (safe, case_tac "S = {a}", simp, fast, fast)
```
```   388
```
```   389 lemma at_neq_bot [simp]: "at (a::'a::perfect_space) \<noteq> bot"
```
```   390   by (simp add: at_eq_bot_iff not_open_singleton)
```
```   391
```
```   392
```
```   393 subsection {* Boundedness *}
```
```   394
```
```   395 definition Bfun :: "('a \<Rightarrow> 'b::real_normed_vector) \<Rightarrow> 'a filter \<Rightarrow> bool"
```
```   396   where "Bfun f F = (\<exists>K>0. eventually (\<lambda>x. norm (f x) \<le> K) F)"
```
```   397
```
```   398 lemma BfunI:
```
```   399   assumes K: "eventually (\<lambda>x. norm (f x) \<le> K) F" shows "Bfun f F"
```
```   400 unfolding Bfun_def
```
```   401 proof (intro exI conjI allI)
```
```   402   show "0 < max K 1" by simp
```
```   403 next
```
```   404   show "eventually (\<lambda>x. norm (f x) \<le> max K 1) F"
```
```   405     using K by (rule eventually_elim1, simp)
```
```   406 qed
```
```   407
```
```   408 lemma BfunE:
```
```   409   assumes "Bfun f F"
```
```   410   obtains B where "0 < B" and "eventually (\<lambda>x. norm (f x) \<le> B) F"
```
```   411 using assms unfolding Bfun_def by fast
```
```   412
```
```   413
```
```   414 subsection {* Convergence to Zero *}
```
```   415
```
```   416 definition Zfun :: "('a \<Rightarrow> 'b::real_normed_vector) \<Rightarrow> 'a filter \<Rightarrow> bool"
```
```   417   where "Zfun f F = (\<forall>r>0. eventually (\<lambda>x. norm (f x) < r) F)"
```
```   418
```
```   419 lemma ZfunI:
```
```   420   "(\<And>r. 0 < r \<Longrightarrow> eventually (\<lambda>x. norm (f x) < r) F) \<Longrightarrow> Zfun f F"
```
```   421   unfolding Zfun_def by simp
```
```   422
```
```   423 lemma ZfunD:
```
```   424   "\<lbrakk>Zfun f F; 0 < r\<rbrakk> \<Longrightarrow> eventually (\<lambda>x. norm (f x) < r) F"
```
```   425   unfolding Zfun_def by simp
```
```   426
```
```   427 lemma Zfun_ssubst:
```
```   428   "eventually (\<lambda>x. f x = g x) F \<Longrightarrow> Zfun g F \<Longrightarrow> Zfun f F"
```
```   429   unfolding Zfun_def by (auto elim!: eventually_rev_mp)
```
```   430
```
```   431 lemma Zfun_zero: "Zfun (\<lambda>x. 0) F"
```
```   432   unfolding Zfun_def by simp
```
```   433
```
```   434 lemma Zfun_norm_iff: "Zfun (\<lambda>x. norm (f x)) F = Zfun (\<lambda>x. f x) F"
```
```   435   unfolding Zfun_def by simp
```
```   436
```
```   437 lemma Zfun_imp_Zfun:
```
```   438   assumes f: "Zfun f F"
```
```   439   assumes g: "eventually (\<lambda>x. norm (g x) \<le> norm (f x) * K) F"
```
```   440   shows "Zfun (\<lambda>x. g x) F"
```
```   441 proof (cases)
```
```   442   assume K: "0 < K"
```
```   443   show ?thesis
```
```   444   proof (rule ZfunI)
```
```   445     fix r::real assume "0 < r"
```
```   446     hence "0 < r / K"
```
```   447       using K by (rule divide_pos_pos)
```
```   448     then have "eventually (\<lambda>x. norm (f x) < r / K) F"
```
```   449       using ZfunD [OF f] by fast
```
```   450     with g show "eventually (\<lambda>x. norm (g x) < r) F"
```
```   451     proof eventually_elim
```
```   452       case (elim x)
```
```   453       hence "norm (f x) * K < r"
```
```   454         by (simp add: pos_less_divide_eq K)
```
```   455       thus ?case
```
```   456         by (simp add: order_le_less_trans [OF elim(1)])
```
```   457     qed
```
```   458   qed
```
```   459 next
```
```   460   assume "\<not> 0 < K"
```
```   461   hence K: "K \<le> 0" by (simp only: not_less)
```
```   462   show ?thesis
```
```   463   proof (rule ZfunI)
```
```   464     fix r :: real
```
```   465     assume "0 < r"
```
```   466     from g show "eventually (\<lambda>x. norm (g x) < r) F"
```
```   467     proof eventually_elim
```
```   468       case (elim x)
```
```   469       also have "norm (f x) * K \<le> norm (f x) * 0"
```
```   470         using K norm_ge_zero by (rule mult_left_mono)
```
```   471       finally show ?case
```
```   472         using `0 < r` by simp
```
```   473     qed
```
```   474   qed
```
```   475 qed
```
```   476
```
```   477 lemma Zfun_le: "\<lbrakk>Zfun g F; \<forall>x. norm (f x) \<le> norm (g x)\<rbrakk> \<Longrightarrow> Zfun f F"
```
```   478   by (erule_tac K="1" in Zfun_imp_Zfun, simp)
```
```   479
```
```   480 lemma Zfun_add:
```
```   481   assumes f: "Zfun f F" and g: "Zfun g F"
```
```   482   shows "Zfun (\<lambda>x. f x + g x) F"
```
```   483 proof (rule ZfunI)
```
```   484   fix r::real assume "0 < r"
```
```   485   hence r: "0 < r / 2" by simp
```
```   486   have "eventually (\<lambda>x. norm (f x) < r/2) F"
```
```   487     using f r by (rule ZfunD)
```
```   488   moreover
```
```   489   have "eventually (\<lambda>x. norm (g x) < r/2) F"
```
```   490     using g r by (rule ZfunD)
```
```   491   ultimately
```
```   492   show "eventually (\<lambda>x. norm (f x + g x) < r) F"
```
```   493   proof eventually_elim
```
```   494     case (elim x)
```
```   495     have "norm (f x + g x) \<le> norm (f x) + norm (g x)"
```
```   496       by (rule norm_triangle_ineq)
```
```   497     also have "\<dots> < r/2 + r/2"
```
```   498       using elim by (rule add_strict_mono)
```
```   499     finally show ?case
```
```   500       by simp
```
```   501   qed
```
```   502 qed
```
```   503
```
```   504 lemma Zfun_minus: "Zfun f F \<Longrightarrow> Zfun (\<lambda>x. - f x) F"
```
```   505   unfolding Zfun_def by simp
```
```   506
```
```   507 lemma Zfun_diff: "\<lbrakk>Zfun f F; Zfun g F\<rbrakk> \<Longrightarrow> Zfun (\<lambda>x. f x - g x) F"
```
```   508   by (simp only: diff_minus Zfun_add Zfun_minus)
```
```   509
```
```   510 lemma (in bounded_linear) Zfun:
```
```   511   assumes g: "Zfun g F"
```
```   512   shows "Zfun (\<lambda>x. f (g x)) F"
```
```   513 proof -
```
```   514   obtain K where "\<And>x. norm (f x) \<le> norm x * K"
```
```   515     using bounded by fast
```
```   516   then have "eventually (\<lambda>x. norm (f (g x)) \<le> norm (g x) * K) F"
```
```   517     by simp
```
```   518   with g show ?thesis
```
```   519     by (rule Zfun_imp_Zfun)
```
```   520 qed
```
```   521
```
```   522 lemma (in bounded_bilinear) Zfun:
```
```   523   assumes f: "Zfun f F"
```
```   524   assumes g: "Zfun g F"
```
```   525   shows "Zfun (\<lambda>x. f x ** g x) F"
```
```   526 proof (rule ZfunI)
```
```   527   fix r::real assume r: "0 < r"
```
```   528   obtain K where K: "0 < K"
```
```   529     and norm_le: "\<And>x y. norm (x ** y) \<le> norm x * norm y * K"
```
```   530     using pos_bounded by fast
```
```   531   from K have K': "0 < inverse K"
```
```   532     by (rule positive_imp_inverse_positive)
```
```   533   have "eventually (\<lambda>x. norm (f x) < r) F"
```
```   534     using f r by (rule ZfunD)
```
```   535   moreover
```
```   536   have "eventually (\<lambda>x. norm (g x) < inverse K) F"
```
```   537     using g K' by (rule ZfunD)
```
```   538   ultimately
```
```   539   show "eventually (\<lambda>x. norm (f x ** g x) < r) F"
```
```   540   proof eventually_elim
```
```   541     case (elim x)
```
```   542     have "norm (f x ** g x) \<le> norm (f x) * norm (g x) * K"
```
```   543       by (rule norm_le)
```
```   544     also have "norm (f x) * norm (g x) * K < r * inverse K * K"
```
```   545       by (intro mult_strict_right_mono mult_strict_mono' norm_ge_zero elim K)
```
```   546     also from K have "r * inverse K * K = r"
```
```   547       by simp
```
```   548     finally show ?case .
```
```   549   qed
```
```   550 qed
```
```   551
```
```   552 lemma (in bounded_bilinear) Zfun_left:
```
```   553   "Zfun f F \<Longrightarrow> Zfun (\<lambda>x. f x ** a) F"
```
```   554   by (rule bounded_linear_left [THEN bounded_linear.Zfun])
```
```   555
```
```   556 lemma (in bounded_bilinear) Zfun_right:
```
```   557   "Zfun f F \<Longrightarrow> Zfun (\<lambda>x. a ** f x) F"
```
```   558   by (rule bounded_linear_right [THEN bounded_linear.Zfun])
```
```   559
```
```   560 lemmas Zfun_mult = bounded_bilinear.Zfun [OF bounded_bilinear_mult]
```
```   561 lemmas Zfun_mult_right = bounded_bilinear.Zfun_right [OF bounded_bilinear_mult]
```
```   562 lemmas Zfun_mult_left = bounded_bilinear.Zfun_left [OF bounded_bilinear_mult]
```
```   563
```
```   564
```
```   565 subsection {* Limits *}
```
```   566
```
```   567 definition (in topological_space)
```
```   568   tendsto :: "('b \<Rightarrow> 'a) \<Rightarrow> 'a \<Rightarrow> 'b filter \<Rightarrow> bool" (infixr "--->" 55) where
```
```   569   "(f ---> l) F \<longleftrightarrow> (\<forall>S. open S \<longrightarrow> l \<in> S \<longrightarrow> eventually (\<lambda>x. f x \<in> S) F)"
```
```   570
```
```   571 definition real_tendsto_inf :: "('a \<Rightarrow> real) \<Rightarrow> 'a filter \<Rightarrow> bool" where
```
```   572   "real_tendsto_inf f F \<equiv> \<forall>x. eventually (\<lambda>y. x < f y) F"
```
```   573
```
```   574 ML {*
```
```   575 structure Tendsto_Intros = Named_Thms
```
```   576 (
```
```   577   val name = @{binding tendsto_intros}
```
```   578   val description = "introduction rules for tendsto"
```
```   579 )
```
```   580 *}
```
```   581
```
```   582 setup Tendsto_Intros.setup
```
```   583
```
```   584 lemma tendsto_mono: "F \<le> F' \<Longrightarrow> (f ---> l) F' \<Longrightarrow> (f ---> l) F"
```
```   585   unfolding tendsto_def le_filter_def by fast
```
```   586
```
```   587 lemma topological_tendstoI:
```
```   588   "(\<And>S. open S \<Longrightarrow> l \<in> S \<Longrightarrow> eventually (\<lambda>x. f x \<in> S) F)
```
```   589     \<Longrightarrow> (f ---> l) F"
```
```   590   unfolding tendsto_def by auto
```
```   591
```
```   592 lemma topological_tendstoD:
```
```   593   "(f ---> l) F \<Longrightarrow> open S \<Longrightarrow> l \<in> S \<Longrightarrow> eventually (\<lambda>x. f x \<in> S) F"
```
```   594   unfolding tendsto_def by auto
```
```   595
```
```   596 lemma tendstoI:
```
```   597   assumes "\<And>e. 0 < e \<Longrightarrow> eventually (\<lambda>x. dist (f x) l < e) F"
```
```   598   shows "(f ---> l) F"
```
```   599   apply (rule topological_tendstoI)
```
```   600   apply (simp add: open_dist)
```
```   601   apply (drule (1) bspec, clarify)
```
```   602   apply (drule assms)
```
```   603   apply (erule eventually_elim1, simp)
```
```   604   done
```
```   605
```
```   606 lemma tendstoD:
```
```   607   "(f ---> l) F \<Longrightarrow> 0 < e \<Longrightarrow> eventually (\<lambda>x. dist (f x) l < e) F"
```
```   608   apply (drule_tac S="{x. dist x l < e}" in topological_tendstoD)
```
```   609   apply (clarsimp simp add: open_dist)
```
```   610   apply (rule_tac x="e - dist x l" in exI, clarsimp)
```
```   611   apply (simp only: less_diff_eq)
```
```   612   apply (erule le_less_trans [OF dist_triangle])
```
```   613   apply simp
```
```   614   apply simp
```
```   615   done
```
```   616
```
```   617 lemma tendsto_iff:
```
```   618   "(f ---> l) F \<longleftrightarrow> (\<forall>e>0. eventually (\<lambda>x. dist (f x) l < e) F)"
```
```   619   using tendstoI tendstoD by fast
```
```   620
```
```   621 lemma tendsto_Zfun_iff: "(f ---> a) F = Zfun (\<lambda>x. f x - a) F"
```
```   622   by (simp only: tendsto_iff Zfun_def dist_norm)
```
```   623
```
```   624 lemma tendsto_bot [simp]: "(f ---> a) bot"
```
```   625   unfolding tendsto_def by simp
```
```   626
```
```   627 lemma tendsto_ident_at [tendsto_intros]: "((\<lambda>x. x) ---> a) (at a)"
```
```   628   unfolding tendsto_def eventually_at_topological by auto
```
```   629
```
```   630 lemma tendsto_ident_at_within [tendsto_intros]:
```
```   631   "((\<lambda>x. x) ---> a) (at a within S)"
```
```   632   unfolding tendsto_def eventually_within eventually_at_topological by auto
```
```   633
```
```   634 lemma tendsto_const [tendsto_intros]: "((\<lambda>x. k) ---> k) F"
```
```   635   by (simp add: tendsto_def)
```
```   636
```
```   637 lemma tendsto_unique:
```
```   638   fixes f :: "'a \<Rightarrow> 'b::t2_space"
```
```   639   assumes "\<not> trivial_limit F" and "(f ---> a) F" and "(f ---> b) F"
```
```   640   shows "a = b"
```
```   641 proof (rule ccontr)
```
```   642   assume "a \<noteq> b"
```
```   643   obtain U V where "open U" "open V" "a \<in> U" "b \<in> V" "U \<inter> V = {}"
```
```   644     using hausdorff [OF `a \<noteq> b`] by fast
```
```   645   have "eventually (\<lambda>x. f x \<in> U) F"
```
```   646     using `(f ---> a) F` `open U` `a \<in> U` by (rule topological_tendstoD)
```
```   647   moreover
```
```   648   have "eventually (\<lambda>x. f x \<in> V) F"
```
```   649     using `(f ---> b) F` `open V` `b \<in> V` by (rule topological_tendstoD)
```
```   650   ultimately
```
```   651   have "eventually (\<lambda>x. False) F"
```
```   652   proof eventually_elim
```
```   653     case (elim x)
```
```   654     hence "f x \<in> U \<inter> V" by simp
```
```   655     with `U \<inter> V = {}` show ?case by simp
```
```   656   qed
```
```   657   with `\<not> trivial_limit F` show "False"
```
```   658     by (simp add: trivial_limit_def)
```
```   659 qed
```
```   660
```
```   661 lemma tendsto_const_iff:
```
```   662   fixes a b :: "'a::t2_space"
```
```   663   assumes "\<not> trivial_limit F" shows "((\<lambda>x. a) ---> b) F \<longleftrightarrow> a = b"
```
```   664   by (safe intro!: tendsto_const tendsto_unique [OF assms tendsto_const])
```
```   665
```
```   666 lemma tendsto_compose:
```
```   667   assumes g: "(g ---> g l) (at l)"
```
```   668   assumes f: "(f ---> l) F"
```
```   669   shows "((\<lambda>x. g (f x)) ---> g l) F"
```
```   670 proof (rule topological_tendstoI)
```
```   671   fix B assume B: "open B" "g l \<in> B"
```
```   672   obtain A where A: "open A" "l \<in> A"
```
```   673     and gB: "\<forall>y. y \<in> A \<longrightarrow> g y \<in> B"
```
```   674     using topological_tendstoD [OF g B] B(2)
```
```   675     unfolding eventually_at_topological by fast
```
```   676   hence "\<forall>x. f x \<in> A \<longrightarrow> g (f x) \<in> B" by simp
```
```   677   from this topological_tendstoD [OF f A]
```
```   678   show "eventually (\<lambda>x. g (f x) \<in> B) F"
```
```   679     by (rule eventually_mono)
```
```   680 qed
```
```   681
```
```   682 lemma tendsto_compose_eventually:
```
```   683   assumes g: "(g ---> m) (at l)"
```
```   684   assumes f: "(f ---> l) F"
```
```   685   assumes inj: "eventually (\<lambda>x. f x \<noteq> l) F"
```
```   686   shows "((\<lambda>x. g (f x)) ---> m) F"
```
```   687 proof (rule topological_tendstoI)
```
```   688   fix B assume B: "open B" "m \<in> B"
```
```   689   obtain A where A: "open A" "l \<in> A"
```
```   690     and gB: "\<And>y. y \<in> A \<Longrightarrow> y \<noteq> l \<Longrightarrow> g y \<in> B"
```
```   691     using topological_tendstoD [OF g B]
```
```   692     unfolding eventually_at_topological by fast
```
```   693   show "eventually (\<lambda>x. g (f x) \<in> B) F"
```
```   694     using topological_tendstoD [OF f A] inj
```
```   695     by (rule eventually_elim2) (simp add: gB)
```
```   696 qed
```
```   697
```
```   698 lemma metric_tendsto_imp_tendsto:
```
```   699   assumes f: "(f ---> a) F"
```
```   700   assumes le: "eventually (\<lambda>x. dist (g x) b \<le> dist (f x) a) F"
```
```   701   shows "(g ---> b) F"
```
```   702 proof (rule tendstoI)
```
```   703   fix e :: real assume "0 < e"
```
```   704   with f have "eventually (\<lambda>x. dist (f x) a < e) F" by (rule tendstoD)
```
```   705   with le show "eventually (\<lambda>x. dist (g x) b < e) F"
```
```   706     using le_less_trans by (rule eventually_elim2)
```
```   707 qed
```
```   708
```
```   709 lemma real_tendsto_inf_real: "real_tendsto_inf real sequentially"
```
```   710 proof (unfold real_tendsto_inf_def, rule allI)
```
```   711   fix x show "eventually (\<lambda>y. x < real y) sequentially"
```
```   712     by (rule eventually_sequentiallyI[of "natceiling (x + 1)"])
```
```   713         (simp add: natceiling_le_eq)
```
```   714 qed
```
```   715
```
```   716
```
```   717
```
```   718 subsubsection {* Distance and norms *}
```
```   719
```
```   720 lemma tendsto_dist [tendsto_intros]:
```
```   721   assumes f: "(f ---> l) F" and g: "(g ---> m) F"
```
```   722   shows "((\<lambda>x. dist (f x) (g x)) ---> dist l m) F"
```
```   723 proof (rule tendstoI)
```
```   724   fix e :: real assume "0 < e"
```
```   725   hence e2: "0 < e/2" by simp
```
```   726   from tendstoD [OF f e2] tendstoD [OF g e2]
```
```   727   show "eventually (\<lambda>x. dist (dist (f x) (g x)) (dist l m) < e) F"
```
```   728   proof (eventually_elim)
```
```   729     case (elim x)
```
```   730     then show "dist (dist (f x) (g x)) (dist l m) < e"
```
```   731       unfolding dist_real_def
```
```   732       using dist_triangle2 [of "f x" "g x" "l"]
```
```   733       using dist_triangle2 [of "g x" "l" "m"]
```
```   734       using dist_triangle3 [of "l" "m" "f x"]
```
```   735       using dist_triangle [of "f x" "m" "g x"]
```
```   736       by arith
```
```   737   qed
```
```   738 qed
```
```   739
```
```   740 lemma norm_conv_dist: "norm x = dist x 0"
```
```   741   unfolding dist_norm by simp
```
```   742
```
```   743 lemma tendsto_norm [tendsto_intros]:
```
```   744   "(f ---> a) F \<Longrightarrow> ((\<lambda>x. norm (f x)) ---> norm a) F"
```
```   745   unfolding norm_conv_dist by (intro tendsto_intros)
```
```   746
```
```   747 lemma tendsto_norm_zero:
```
```   748   "(f ---> 0) F \<Longrightarrow> ((\<lambda>x. norm (f x)) ---> 0) F"
```
```   749   by (drule tendsto_norm, simp)
```
```   750
```
```   751 lemma tendsto_norm_zero_cancel:
```
```   752   "((\<lambda>x. norm (f x)) ---> 0) F \<Longrightarrow> (f ---> 0) F"
```
```   753   unfolding tendsto_iff dist_norm by simp
```
```   754
```
```   755 lemma tendsto_norm_zero_iff:
```
```   756   "((\<lambda>x. norm (f x)) ---> 0) F \<longleftrightarrow> (f ---> 0) F"
```
```   757   unfolding tendsto_iff dist_norm by simp
```
```   758
```
```   759 lemma tendsto_rabs [tendsto_intros]:
```
```   760   "(f ---> (l::real)) F \<Longrightarrow> ((\<lambda>x. \<bar>f x\<bar>) ---> \<bar>l\<bar>) F"
```
```   761   by (fold real_norm_def, rule tendsto_norm)
```
```   762
```
```   763 lemma tendsto_rabs_zero:
```
```   764   "(f ---> (0::real)) F \<Longrightarrow> ((\<lambda>x. \<bar>f x\<bar>) ---> 0) F"
```
```   765   by (fold real_norm_def, rule tendsto_norm_zero)
```
```   766
```
```   767 lemma tendsto_rabs_zero_cancel:
```
```   768   "((\<lambda>x. \<bar>f x\<bar>) ---> (0::real)) F \<Longrightarrow> (f ---> 0) F"
```
```   769   by (fold real_norm_def, rule tendsto_norm_zero_cancel)
```
```   770
```
```   771 lemma tendsto_rabs_zero_iff:
```
```   772   "((\<lambda>x. \<bar>f x\<bar>) ---> (0::real)) F \<longleftrightarrow> (f ---> 0) F"
```
```   773   by (fold real_norm_def, rule tendsto_norm_zero_iff)
```
```   774
```
```   775 subsubsection {* Addition and subtraction *}
```
```   776
```
```   777 lemma tendsto_add [tendsto_intros]:
```
```   778   fixes a b :: "'a::real_normed_vector"
```
```   779   shows "\<lbrakk>(f ---> a) F; (g ---> b) F\<rbrakk> \<Longrightarrow> ((\<lambda>x. f x + g x) ---> a + b) F"
```
```   780   by (simp only: tendsto_Zfun_iff add_diff_add Zfun_add)
```
```   781
```
```   782 lemma tendsto_add_zero:
```
```   783   fixes f g :: "'a::type \<Rightarrow> 'b::real_normed_vector"
```
```   784   shows "\<lbrakk>(f ---> 0) F; (g ---> 0) F\<rbrakk> \<Longrightarrow> ((\<lambda>x. f x + g x) ---> 0) F"
```
```   785   by (drule (1) tendsto_add, simp)
```
```   786
```
```   787 lemma tendsto_minus [tendsto_intros]:
```
```   788   fixes a :: "'a::real_normed_vector"
```
```   789   shows "(f ---> a) F \<Longrightarrow> ((\<lambda>x. - f x) ---> - a) F"
```
```   790   by (simp only: tendsto_Zfun_iff minus_diff_minus Zfun_minus)
```
```   791
```
```   792 lemma tendsto_minus_cancel:
```
```   793   fixes a :: "'a::real_normed_vector"
```
```   794   shows "((\<lambda>x. - f x) ---> - a) F \<Longrightarrow> (f ---> a) F"
```
```   795   by (drule tendsto_minus, simp)
```
```   796
```
```   797 lemma tendsto_diff [tendsto_intros]:
```
```   798   fixes a b :: "'a::real_normed_vector"
```
```   799   shows "\<lbrakk>(f ---> a) F; (g ---> b) F\<rbrakk> \<Longrightarrow> ((\<lambda>x. f x - g x) ---> a - b) F"
```
```   800   by (simp add: diff_minus tendsto_add tendsto_minus)
```
```   801
```
```   802 lemma tendsto_setsum [tendsto_intros]:
```
```   803   fixes f :: "'a \<Rightarrow> 'b \<Rightarrow> 'c::real_normed_vector"
```
```   804   assumes "\<And>i. i \<in> S \<Longrightarrow> (f i ---> a i) F"
```
```   805   shows "((\<lambda>x. \<Sum>i\<in>S. f i x) ---> (\<Sum>i\<in>S. a i)) F"
```
```   806 proof (cases "finite S")
```
```   807   assume "finite S" thus ?thesis using assms
```
```   808     by (induct, simp add: tendsto_const, simp add: tendsto_add)
```
```   809 next
```
```   810   assume "\<not> finite S" thus ?thesis
```
```   811     by (simp add: tendsto_const)
```
```   812 qed
```
```   813
```
```   814 lemma real_tendsto_sandwich:
```
```   815   fixes f g h :: "'a \<Rightarrow> real"
```
```   816   assumes ev: "eventually (\<lambda>n. f n \<le> g n) net" "eventually (\<lambda>n. g n \<le> h n) net"
```
```   817   assumes lim: "(f ---> c) net" "(h ---> c) net"
```
```   818   shows "(g ---> c) net"
```
```   819 proof -
```
```   820   have "((\<lambda>n. g n - f n) ---> 0) net"
```
```   821   proof (rule metric_tendsto_imp_tendsto)
```
```   822     show "eventually (\<lambda>n. dist (g n - f n) 0 \<le> dist (h n - f n) 0) net"
```
```   823       using ev by (rule eventually_elim2) (simp add: dist_real_def)
```
```   824     show "((\<lambda>n. h n - f n) ---> 0) net"
```
```   825       using tendsto_diff[OF lim(2,1)] by simp
```
```   826   qed
```
```   827   from tendsto_add[OF this lim(1)] show ?thesis by simp
```
```   828 qed
```
```   829
```
```   830 subsubsection {* Linear operators and multiplication *}
```
```   831
```
```   832 lemma (in bounded_linear) tendsto:
```
```   833   "(g ---> a) F \<Longrightarrow> ((\<lambda>x. f (g x)) ---> f a) F"
```
```   834   by (simp only: tendsto_Zfun_iff diff [symmetric] Zfun)
```
```   835
```
```   836 lemma (in bounded_linear) tendsto_zero:
```
```   837   "(g ---> 0) F \<Longrightarrow> ((\<lambda>x. f (g x)) ---> 0) F"
```
```   838   by (drule tendsto, simp only: zero)
```
```   839
```
```   840 lemma (in bounded_bilinear) tendsto:
```
```   841   "\<lbrakk>(f ---> a) F; (g ---> b) F\<rbrakk> \<Longrightarrow> ((\<lambda>x. f x ** g x) ---> a ** b) F"
```
```   842   by (simp only: tendsto_Zfun_iff prod_diff_prod
```
```   843                  Zfun_add Zfun Zfun_left Zfun_right)
```
```   844
```
```   845 lemma (in bounded_bilinear) tendsto_zero:
```
```   846   assumes f: "(f ---> 0) F"
```
```   847   assumes g: "(g ---> 0) F"
```
```   848   shows "((\<lambda>x. f x ** g x) ---> 0) F"
```
```   849   using tendsto [OF f g] by (simp add: zero_left)
```
```   850
```
```   851 lemma (in bounded_bilinear) tendsto_left_zero:
```
```   852   "(f ---> 0) F \<Longrightarrow> ((\<lambda>x. f x ** c) ---> 0) F"
```
```   853   by (rule bounded_linear.tendsto_zero [OF bounded_linear_left])
```
```   854
```
```   855 lemma (in bounded_bilinear) tendsto_right_zero:
```
```   856   "(f ---> 0) F \<Longrightarrow> ((\<lambda>x. c ** f x) ---> 0) F"
```
```   857   by (rule bounded_linear.tendsto_zero [OF bounded_linear_right])
```
```   858
```
```   859 lemmas tendsto_of_real [tendsto_intros] =
```
```   860   bounded_linear.tendsto [OF bounded_linear_of_real]
```
```   861
```
```   862 lemmas tendsto_scaleR [tendsto_intros] =
```
```   863   bounded_bilinear.tendsto [OF bounded_bilinear_scaleR]
```
```   864
```
```   865 lemmas tendsto_mult [tendsto_intros] =
```
```   866   bounded_bilinear.tendsto [OF bounded_bilinear_mult]
```
```   867
```
```   868 lemmas tendsto_mult_zero =
```
```   869   bounded_bilinear.tendsto_zero [OF bounded_bilinear_mult]
```
```   870
```
```   871 lemmas tendsto_mult_left_zero =
```
```   872   bounded_bilinear.tendsto_left_zero [OF bounded_bilinear_mult]
```
```   873
```
```   874 lemmas tendsto_mult_right_zero =
```
```   875   bounded_bilinear.tendsto_right_zero [OF bounded_bilinear_mult]
```
```   876
```
```   877 lemma tendsto_power [tendsto_intros]:
```
```   878   fixes f :: "'a \<Rightarrow> 'b::{power,real_normed_algebra}"
```
```   879   shows "(f ---> a) F \<Longrightarrow> ((\<lambda>x. f x ^ n) ---> a ^ n) F"
```
```   880   by (induct n) (simp_all add: tendsto_const tendsto_mult)
```
```   881
```
```   882 lemma tendsto_setprod [tendsto_intros]:
```
```   883   fixes f :: "'a \<Rightarrow> 'b \<Rightarrow> 'c::{real_normed_algebra,comm_ring_1}"
```
```   884   assumes "\<And>i. i \<in> S \<Longrightarrow> (f i ---> L i) F"
```
```   885   shows "((\<lambda>x. \<Prod>i\<in>S. f i x) ---> (\<Prod>i\<in>S. L i)) F"
```
```   886 proof (cases "finite S")
```
```   887   assume "finite S" thus ?thesis using assms
```
```   888     by (induct, simp add: tendsto_const, simp add: tendsto_mult)
```
```   889 next
```
```   890   assume "\<not> finite S" thus ?thesis
```
```   891     by (simp add: tendsto_const)
```
```   892 qed
```
```   893
```
```   894 subsubsection {* Inverse and division *}
```
```   895
```
```   896 lemma (in bounded_bilinear) Zfun_prod_Bfun:
```
```   897   assumes f: "Zfun f F"
```
```   898   assumes g: "Bfun g F"
```
```   899   shows "Zfun (\<lambda>x. f x ** g x) F"
```
```   900 proof -
```
```   901   obtain K where K: "0 \<le> K"
```
```   902     and norm_le: "\<And>x y. norm (x ** y) \<le> norm x * norm y * K"
```
```   903     using nonneg_bounded by fast
```
```   904   obtain B where B: "0 < B"
```
```   905     and norm_g: "eventually (\<lambda>x. norm (g x) \<le> B) F"
```
```   906     using g by (rule BfunE)
```
```   907   have "eventually (\<lambda>x. norm (f x ** g x) \<le> norm (f x) * (B * K)) F"
```
```   908   using norm_g proof eventually_elim
```
```   909     case (elim x)
```
```   910     have "norm (f x ** g x) \<le> norm (f x) * norm (g x) * K"
```
```   911       by (rule norm_le)
```
```   912     also have "\<dots> \<le> norm (f x) * B * K"
```
```   913       by (intro mult_mono' order_refl norm_g norm_ge_zero
```
```   914                 mult_nonneg_nonneg K elim)
```
```   915     also have "\<dots> = norm (f x) * (B * K)"
```
```   916       by (rule mult_assoc)
```
```   917     finally show "norm (f x ** g x) \<le> norm (f x) * (B * K)" .
```
```   918   qed
```
```   919   with f show ?thesis
```
```   920     by (rule Zfun_imp_Zfun)
```
```   921 qed
```
```   922
```
```   923 lemma (in bounded_bilinear) flip:
```
```   924   "bounded_bilinear (\<lambda>x y. y ** x)"
```
```   925   apply default
```
```   926   apply (rule add_right)
```
```   927   apply (rule add_left)
```
```   928   apply (rule scaleR_right)
```
```   929   apply (rule scaleR_left)
```
```   930   apply (subst mult_commute)
```
```   931   using bounded by fast
```
```   932
```
```   933 lemma (in bounded_bilinear) Bfun_prod_Zfun:
```
```   934   assumes f: "Bfun f F"
```
```   935   assumes g: "Zfun g F"
```
```   936   shows "Zfun (\<lambda>x. f x ** g x) F"
```
```   937   using flip g f by (rule bounded_bilinear.Zfun_prod_Bfun)
```
```   938
```
```   939 lemma Bfun_inverse_lemma:
```
```   940   fixes x :: "'a::real_normed_div_algebra"
```
```   941   shows "\<lbrakk>r \<le> norm x; 0 < r\<rbrakk> \<Longrightarrow> norm (inverse x) \<le> inverse r"
```
```   942   apply (subst nonzero_norm_inverse, clarsimp)
```
```   943   apply (erule (1) le_imp_inverse_le)
```
```   944   done
```
```   945
```
```   946 lemma Bfun_inverse:
```
```   947   fixes a :: "'a::real_normed_div_algebra"
```
```   948   assumes f: "(f ---> a) F"
```
```   949   assumes a: "a \<noteq> 0"
```
```   950   shows "Bfun (\<lambda>x. inverse (f x)) F"
```
```   951 proof -
```
```   952   from a have "0 < norm a" by simp
```
```   953   hence "\<exists>r>0. r < norm a" by (rule dense)
```
```   954   then obtain r where r1: "0 < r" and r2: "r < norm a" by fast
```
```   955   have "eventually (\<lambda>x. dist (f x) a < r) F"
```
```   956     using tendstoD [OF f r1] by fast
```
```   957   hence "eventually (\<lambda>x. norm (inverse (f x)) \<le> inverse (norm a - r)) F"
```
```   958   proof eventually_elim
```
```   959     case (elim x)
```
```   960     hence 1: "norm (f x - a) < r"
```
```   961       by (simp add: dist_norm)
```
```   962     hence 2: "f x \<noteq> 0" using r2 by auto
```
```   963     hence "norm (inverse (f x)) = inverse (norm (f x))"
```
```   964       by (rule nonzero_norm_inverse)
```
```   965     also have "\<dots> \<le> inverse (norm a - r)"
```
```   966     proof (rule le_imp_inverse_le)
```
```   967       show "0 < norm a - r" using r2 by simp
```
```   968     next
```
```   969       have "norm a - norm (f x) \<le> norm (a - f x)"
```
```   970         by (rule norm_triangle_ineq2)
```
```   971       also have "\<dots> = norm (f x - a)"
```
```   972         by (rule norm_minus_commute)
```
```   973       also have "\<dots> < r" using 1 .
```
```   974       finally show "norm a - r \<le> norm (f x)" by simp
```
```   975     qed
```
```   976     finally show "norm (inverse (f x)) \<le> inverse (norm a - r)" .
```
```   977   qed
```
```   978   thus ?thesis by (rule BfunI)
```
```   979 qed
```
```   980
```
```   981 lemma tendsto_inverse [tendsto_intros]:
```
```   982   fixes a :: "'a::real_normed_div_algebra"
```
```   983   assumes f: "(f ---> a) F"
```
```   984   assumes a: "a \<noteq> 0"
```
```   985   shows "((\<lambda>x. inverse (f x)) ---> inverse a) F"
```
```   986 proof -
```
```   987   from a have "0 < norm a" by simp
```
```   988   with f have "eventually (\<lambda>x. dist (f x) a < norm a) F"
```
```   989     by (rule tendstoD)
```
```   990   then have "eventually (\<lambda>x. f x \<noteq> 0) F"
```
```   991     unfolding dist_norm by (auto elim!: eventually_elim1)
```
```   992   with a have "eventually (\<lambda>x. inverse (f x) - inverse a =
```
```   993     - (inverse (f x) * (f x - a) * inverse a)) F"
```
```   994     by (auto elim!: eventually_elim1 simp: inverse_diff_inverse)
```
```   995   moreover have "Zfun (\<lambda>x. - (inverse (f x) * (f x - a) * inverse a)) F"
```
```   996     by (intro Zfun_minus Zfun_mult_left
```
```   997       bounded_bilinear.Bfun_prod_Zfun [OF bounded_bilinear_mult]
```
```   998       Bfun_inverse [OF f a] f [unfolded tendsto_Zfun_iff])
```
```   999   ultimately show ?thesis
```
```  1000     unfolding tendsto_Zfun_iff by (rule Zfun_ssubst)
```
```  1001 qed
```
```  1002
```
```  1003 lemma tendsto_divide [tendsto_intros]:
```
```  1004   fixes a b :: "'a::real_normed_field"
```
```  1005   shows "\<lbrakk>(f ---> a) F; (g ---> b) F; b \<noteq> 0\<rbrakk>
```
```  1006     \<Longrightarrow> ((\<lambda>x. f x / g x) ---> a / b) F"
```
```  1007   by (simp add: tendsto_mult tendsto_inverse divide_inverse)
```
```  1008
```
```  1009 lemma tendsto_sgn [tendsto_intros]:
```
```  1010   fixes l :: "'a::real_normed_vector"
```
```  1011   shows "\<lbrakk>(f ---> l) F; l \<noteq> 0\<rbrakk> \<Longrightarrow> ((\<lambda>x. sgn (f x)) ---> sgn l) F"
```
```  1012   unfolding sgn_div_norm by (simp add: tendsto_intros)
```
```  1013
```
```  1014 end
```