src/HOL/Limits.thy
 author noschinl Mon Mar 12 21:28:10 2012 +0100 (2012-03-12) changeset 46886 4cd29473c65d parent 45892 8dcf6692433f child 46887 cb891d9a23c1 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 ev_elim_tac ctxt thms thm = let
```
```   116       val thy = Proof_Context.theory_of ctxt
```
```   117       val mp_thms = thms RL [@{thm eventually_rev_mp}]
```
```   118       val raw_elim_thm =
```
```   119         (@{thm allI} RS @{thm always_eventually})
```
```   120         |> fold (fn thm1 => fn thm2 => thm2 RS thm1) mp_thms
```
```   121         |> fold (fn _ => fn thm => @{thm impI} RS thm) thms
```
```   122       val cases_prop = prop_of (raw_elim_thm RS thm)
```
```   123       val cases = (Rule_Cases.make_common (thy, cases_prop) [(("elim", []), [])])
```
```   124     in
```
```   125       CASES cases (rtac raw_elim_thm 1) thm
```
```   126     end
```
```   127
```
```   128   fun eventually_elim_setup name =
```
```   129     Method.setup name (Scan.succeed (fn ctxt => METHOD_CASES (ev_elim_tac ctxt)))
```
```   130       "elimination of eventually quantifiers"
```
```   131 *}
```
```   132
```
```   133 setup {* eventually_elim_setup @{binding "eventually_elim"} *}
```
```   134
```
```   135
```
```   136 subsection {* Finer-than relation *}
```
```   137
```
```   138 text {* @{term "F \<le> F'"} means that filter @{term F} is finer than
```
```   139 filter @{term F'}. *}
```
```   140
```
```   141 instantiation filter :: (type) complete_lattice
```
```   142 begin
```
```   143
```
```   144 definition le_filter_def:
```
```   145   "F \<le> F' \<longleftrightarrow> (\<forall>P. eventually P F' \<longrightarrow> eventually P F)"
```
```   146
```
```   147 definition
```
```   148   "(F :: 'a filter) < F' \<longleftrightarrow> F \<le> F' \<and> \<not> F' \<le> F"
```
```   149
```
```   150 definition
```
```   151   "top = Abs_filter (\<lambda>P. \<forall>x. P x)"
```
```   152
```
```   153 definition
```
```   154   "bot = Abs_filter (\<lambda>P. True)"
```
```   155
```
```   156 definition
```
```   157   "sup F F' = Abs_filter (\<lambda>P. eventually P F \<and> eventually P F')"
```
```   158
```
```   159 definition
```
```   160   "inf F F' = Abs_filter
```
```   161       (\<lambda>P. \<exists>Q R. eventually Q F \<and> eventually R F' \<and> (\<forall>x. Q x \<and> R x \<longrightarrow> P x))"
```
```   162
```
```   163 definition
```
```   164   "Sup S = Abs_filter (\<lambda>P. \<forall>F\<in>S. eventually P F)"
```
```   165
```
```   166 definition
```
```   167   "Inf S = Sup {F::'a filter. \<forall>F'\<in>S. F \<le> F'}"
```
```   168
```
```   169 lemma eventually_top [simp]: "eventually P top \<longleftrightarrow> (\<forall>x. P x)"
```
```   170   unfolding top_filter_def
```
```   171   by (rule eventually_Abs_filter, rule is_filter.intro, auto)
```
```   172
```
```   173 lemma eventually_bot [simp]: "eventually P bot"
```
```   174   unfolding bot_filter_def
```
```   175   by (subst eventually_Abs_filter, rule is_filter.intro, auto)
```
```   176
```
```   177 lemma eventually_sup:
```
```   178   "eventually P (sup F F') \<longleftrightarrow> eventually P F \<and> eventually P F'"
```
```   179   unfolding sup_filter_def
```
```   180   by (rule eventually_Abs_filter, rule is_filter.intro)
```
```   181      (auto elim!: eventually_rev_mp)
```
```   182
```
```   183 lemma eventually_inf:
```
```   184   "eventually P (inf F F') \<longleftrightarrow>
```
```   185    (\<exists>Q R. eventually Q F \<and> eventually R F' \<and> (\<forall>x. Q x \<and> R x \<longrightarrow> P x))"
```
```   186   unfolding inf_filter_def
```
```   187   apply (rule eventually_Abs_filter, rule is_filter.intro)
```
```   188   apply (fast intro: eventually_True)
```
```   189   apply clarify
```
```   190   apply (intro exI conjI)
```
```   191   apply (erule (1) eventually_conj)
```
```   192   apply (erule (1) eventually_conj)
```
```   193   apply simp
```
```   194   apply auto
```
```   195   done
```
```   196
```
```   197 lemma eventually_Sup:
```
```   198   "eventually P (Sup S) \<longleftrightarrow> (\<forall>F\<in>S. eventually P F)"
```
```   199   unfolding Sup_filter_def
```
```   200   apply (rule eventually_Abs_filter, rule is_filter.intro)
```
```   201   apply (auto intro: eventually_conj elim!: eventually_rev_mp)
```
```   202   done
```
```   203
```
```   204 instance proof
```
```   205   fix F F' F'' :: "'a filter" and S :: "'a filter set"
```
```   206   { show "F < F' \<longleftrightarrow> F \<le> F' \<and> \<not> F' \<le> F"
```
```   207     by (rule less_filter_def) }
```
```   208   { show "F \<le> F"
```
```   209     unfolding le_filter_def by simp }
```
```   210   { assume "F \<le> F'" and "F' \<le> F''" thus "F \<le> F''"
```
```   211     unfolding le_filter_def by simp }
```
```   212   { assume "F \<le> F'" and "F' \<le> F" thus "F = F'"
```
```   213     unfolding le_filter_def filter_eq_iff by fast }
```
```   214   { show "F \<le> top"
```
```   215     unfolding le_filter_def eventually_top by (simp add: always_eventually) }
```
```   216   { show "bot \<le> F"
```
```   217     unfolding le_filter_def by simp }
```
```   218   { show "F \<le> sup F F'" and "F' \<le> sup F F'"
```
```   219     unfolding le_filter_def eventually_sup by simp_all }
```
```   220   { assume "F \<le> F''" and "F' \<le> F''" thus "sup F F' \<le> F''"
```
```   221     unfolding le_filter_def eventually_sup by simp }
```
```   222   { show "inf F F' \<le> F" and "inf F F' \<le> F'"
```
```   223     unfolding le_filter_def eventually_inf by (auto intro: eventually_True) }
```
```   224   { assume "F \<le> F'" and "F \<le> F''" thus "F \<le> inf F' F''"
```
```   225     unfolding le_filter_def eventually_inf
```
```   226     by (auto elim!: eventually_mono intro: eventually_conj) }
```
```   227   { assume "F \<in> S" thus "F \<le> Sup S"
```
```   228     unfolding le_filter_def eventually_Sup by simp }
```
```   229   { assume "\<And>F. F \<in> S \<Longrightarrow> F \<le> F'" thus "Sup S \<le> F'"
```
```   230     unfolding le_filter_def eventually_Sup by simp }
```
```   231   { assume "F'' \<in> S" thus "Inf S \<le> F''"
```
```   232     unfolding le_filter_def Inf_filter_def eventually_Sup Ball_def by simp }
```
```   233   { assume "\<And>F'. F' \<in> S \<Longrightarrow> F \<le> F'" thus "F \<le> Inf S"
```
```   234     unfolding le_filter_def Inf_filter_def eventually_Sup Ball_def by simp }
```
```   235 qed
```
```   236
```
```   237 end
```
```   238
```
```   239 lemma filter_leD:
```
```   240   "F \<le> F' \<Longrightarrow> eventually P F' \<Longrightarrow> eventually P F"
```
```   241   unfolding le_filter_def by simp
```
```   242
```
```   243 lemma filter_leI:
```
```   244   "(\<And>P. eventually P F' \<Longrightarrow> eventually P F) \<Longrightarrow> F \<le> F'"
```
```   245   unfolding le_filter_def by simp
```
```   246
```
```   247 lemma eventually_False:
```
```   248   "eventually (\<lambda>x. False) F \<longleftrightarrow> F = bot"
```
```   249   unfolding filter_eq_iff by (auto elim: eventually_rev_mp)
```
```   250
```
```   251 abbreviation (input) trivial_limit :: "'a filter \<Rightarrow> bool"
```
```   252   where "trivial_limit F \<equiv> F = bot"
```
```   253
```
```   254 lemma trivial_limit_def: "trivial_limit F \<longleftrightarrow> eventually (\<lambda>x. False) F"
```
```   255   by (rule eventually_False [symmetric])
```
```   256
```
```   257
```
```   258 subsection {* Map function for filters *}
```
```   259
```
```   260 definition filtermap :: "('a \<Rightarrow> 'b) \<Rightarrow> 'a filter \<Rightarrow> 'b filter"
```
```   261   where "filtermap f F = Abs_filter (\<lambda>P. eventually (\<lambda>x. P (f x)) F)"
```
```   262
```
```   263 lemma eventually_filtermap:
```
```   264   "eventually P (filtermap f F) = eventually (\<lambda>x. P (f x)) F"
```
```   265   unfolding filtermap_def
```
```   266   apply (rule eventually_Abs_filter)
```
```   267   apply (rule is_filter.intro)
```
```   268   apply (auto elim!: eventually_rev_mp)
```
```   269   done
```
```   270
```
```   271 lemma filtermap_ident: "filtermap (\<lambda>x. x) F = F"
```
```   272   by (simp add: filter_eq_iff eventually_filtermap)
```
```   273
```
```   274 lemma filtermap_filtermap:
```
```   275   "filtermap f (filtermap g F) = filtermap (\<lambda>x. f (g x)) F"
```
```   276   by (simp add: filter_eq_iff eventually_filtermap)
```
```   277
```
```   278 lemma filtermap_mono: "F \<le> F' \<Longrightarrow> filtermap f F \<le> filtermap f F'"
```
```   279   unfolding le_filter_def eventually_filtermap by simp
```
```   280
```
```   281 lemma filtermap_bot [simp]: "filtermap f bot = bot"
```
```   282   by (simp add: filter_eq_iff eventually_filtermap)
```
```   283
```
```   284
```
```   285 subsection {* Sequentially *}
```
```   286
```
```   287 definition sequentially :: "nat filter"
```
```   288   where "sequentially = Abs_filter (\<lambda>P. \<exists>k. \<forall>n\<ge>k. P n)"
```
```   289
```
```   290 lemma eventually_sequentially:
```
```   291   "eventually P sequentially \<longleftrightarrow> (\<exists>N. \<forall>n\<ge>N. P n)"
```
```   292 unfolding sequentially_def
```
```   293 proof (rule eventually_Abs_filter, rule is_filter.intro)
```
```   294   fix P Q :: "nat \<Rightarrow> bool"
```
```   295   assume "\<exists>i. \<forall>n\<ge>i. P n" and "\<exists>j. \<forall>n\<ge>j. Q n"
```
```   296   then obtain i j where "\<forall>n\<ge>i. P n" and "\<forall>n\<ge>j. Q n" by auto
```
```   297   then have "\<forall>n\<ge>max i j. P n \<and> Q n" by simp
```
```   298   then show "\<exists>k. \<forall>n\<ge>k. P n \<and> Q n" ..
```
```   299 qed auto
```
```   300
```
```   301 lemma sequentially_bot [simp, intro]: "sequentially \<noteq> bot"
```
```   302   unfolding filter_eq_iff eventually_sequentially by auto
```
```   303
```
```   304 lemmas trivial_limit_sequentially = sequentially_bot
```
```   305
```
```   306 lemma eventually_False_sequentially [simp]:
```
```   307   "\<not> eventually (\<lambda>n. False) sequentially"
```
```   308   by (simp add: eventually_False)
```
```   309
```
```   310 lemma le_sequentially:
```
```   311   "F \<le> sequentially \<longleftrightarrow> (\<forall>N. eventually (\<lambda>n. N \<le> n) F)"
```
```   312   unfolding le_filter_def eventually_sequentially
```
```   313   by (safe, fast, drule_tac x=N in spec, auto elim: eventually_rev_mp)
```
```   314
```
```   315 lemma eventually_sequentiallyI:
```
```   316   assumes "\<And>x. c \<le> x \<Longrightarrow> P x"
```
```   317   shows "eventually P sequentially"
```
```   318 using assms by (auto simp: eventually_sequentially)
```
```   319
```
```   320
```
```   321 subsection {* Standard filters *}
```
```   322
```
```   323 definition within :: "'a filter \<Rightarrow> 'a set \<Rightarrow> 'a filter" (infixr "within" 70)
```
```   324   where "F within S = Abs_filter (\<lambda>P. eventually (\<lambda>x. x \<in> S \<longrightarrow> P x) F)"
```
```   325
```
```   326 definition (in topological_space) nhds :: "'a \<Rightarrow> 'a filter"
```
```   327   where "nhds a = Abs_filter (\<lambda>P. \<exists>S. open S \<and> a \<in> S \<and> (\<forall>x\<in>S. P x))"
```
```   328
```
```   329 definition (in topological_space) at :: "'a \<Rightarrow> 'a filter"
```
```   330   where "at a = nhds a within - {a}"
```
```   331
```
```   332 lemma eventually_within:
```
```   333   "eventually P (F within S) = eventually (\<lambda>x. x \<in> S \<longrightarrow> P x) F"
```
```   334   unfolding within_def
```
```   335   by (rule eventually_Abs_filter, rule is_filter.intro)
```
```   336      (auto elim!: eventually_rev_mp)
```
```   337
```
```   338 lemma within_UNIV [simp]: "F within UNIV = F"
```
```   339   unfolding filter_eq_iff eventually_within by simp
```
```   340
```
```   341 lemma within_empty [simp]: "F within {} = bot"
```
```   342   unfolding filter_eq_iff eventually_within by simp
```
```   343
```
```   344 lemma eventually_nhds:
```
```   345   "eventually P (nhds a) \<longleftrightarrow> (\<exists>S. open S \<and> a \<in> S \<and> (\<forall>x\<in>S. P x))"
```
```   346 unfolding nhds_def
```
```   347 proof (rule eventually_Abs_filter, rule is_filter.intro)
```
```   348   have "open UNIV \<and> a \<in> UNIV \<and> (\<forall>x\<in>UNIV. True)" by simp
```
```   349   thus "\<exists>S. open S \<and> a \<in> S \<and> (\<forall>x\<in>S. True)" by - rule
```
```   350 next
```
```   351   fix P Q
```
```   352   assume "\<exists>S. open S \<and> a \<in> S \<and> (\<forall>x\<in>S. P x)"
```
```   353      and "\<exists>T. open T \<and> a \<in> T \<and> (\<forall>x\<in>T. Q x)"
```
```   354   then obtain S T where
```
```   355     "open S \<and> a \<in> S \<and> (\<forall>x\<in>S. P x)"
```
```   356     "open T \<and> a \<in> T \<and> (\<forall>x\<in>T. Q x)" by auto
```
```   357   hence "open (S \<inter> T) \<and> a \<in> S \<inter> T \<and> (\<forall>x\<in>(S \<inter> T). P x \<and> Q x)"
```
```   358     by (simp add: open_Int)
```
```   359   thus "\<exists>S. open S \<and> a \<in> S \<and> (\<forall>x\<in>S. P x \<and> Q x)" by - rule
```
```   360 qed auto
```
```   361
```
```   362 lemma eventually_nhds_metric:
```
```   363   "eventually P (nhds a) \<longleftrightarrow> (\<exists>d>0. \<forall>x. dist x a < d \<longrightarrow> P x)"
```
```   364 unfolding eventually_nhds open_dist
```
```   365 apply safe
```
```   366 apply fast
```
```   367 apply (rule_tac x="{x. dist x a < d}" in exI, simp)
```
```   368 apply clarsimp
```
```   369 apply (rule_tac x="d - dist x a" in exI, clarsimp)
```
```   370 apply (simp only: less_diff_eq)
```
```   371 apply (erule le_less_trans [OF dist_triangle])
```
```   372 done
```
```   373
```
```   374 lemma nhds_neq_bot [simp]: "nhds a \<noteq> bot"
```
```   375   unfolding trivial_limit_def eventually_nhds by simp
```
```   376
```
```   377 lemma eventually_at_topological:
```
```   378   "eventually P (at a) \<longleftrightarrow> (\<exists>S. open S \<and> a \<in> S \<and> (\<forall>x\<in>S. x \<noteq> a \<longrightarrow> P x))"
```
```   379 unfolding at_def eventually_within eventually_nhds by simp
```
```   380
```
```   381 lemma eventually_at:
```
```   382   fixes a :: "'a::metric_space"
```
```   383   shows "eventually P (at a) \<longleftrightarrow> (\<exists>d>0. \<forall>x. x \<noteq> a \<and> dist x a < d \<longrightarrow> P x)"
```
```   384 unfolding at_def eventually_within eventually_nhds_metric by auto
```
```   385
```
```   386 lemma at_eq_bot_iff: "at a = bot \<longleftrightarrow> open {a}"
```
```   387   unfolding trivial_limit_def eventually_at_topological
```
```   388   by (safe, case_tac "S = {a}", simp, fast, fast)
```
```   389
```
```   390 lemma at_neq_bot [simp]: "at (a::'a::perfect_space) \<noteq> bot"
```
```   391   by (simp add: at_eq_bot_iff not_open_singleton)
```
```   392
```
```   393
```
```   394 subsection {* Boundedness *}
```
```   395
```
```   396 definition Bfun :: "('a \<Rightarrow> 'b::real_normed_vector) \<Rightarrow> 'a filter \<Rightarrow> bool"
```
```   397   where "Bfun f F = (\<exists>K>0. eventually (\<lambda>x. norm (f x) \<le> K) F)"
```
```   398
```
```   399 lemma BfunI:
```
```   400   assumes K: "eventually (\<lambda>x. norm (f x) \<le> K) F" shows "Bfun f F"
```
```   401 unfolding Bfun_def
```
```   402 proof (intro exI conjI allI)
```
```   403   show "0 < max K 1" by simp
```
```   404 next
```
```   405   show "eventually (\<lambda>x. norm (f x) \<le> max K 1) F"
```
```   406     using K by (rule eventually_elim1, simp)
```
```   407 qed
```
```   408
```
```   409 lemma BfunE:
```
```   410   assumes "Bfun f F"
```
```   411   obtains B where "0 < B" and "eventually (\<lambda>x. norm (f x) \<le> B) F"
```
```   412 using assms unfolding Bfun_def by fast
```
```   413
```
```   414
```
```   415 subsection {* Convergence to Zero *}
```
```   416
```
```   417 definition Zfun :: "('a \<Rightarrow> 'b::real_normed_vector) \<Rightarrow> 'a filter \<Rightarrow> bool"
```
```   418   where "Zfun f F = (\<forall>r>0. eventually (\<lambda>x. norm (f x) < r) F)"
```
```   419
```
```   420 lemma ZfunI:
```
```   421   "(\<And>r. 0 < r \<Longrightarrow> eventually (\<lambda>x. norm (f x) < r) F) \<Longrightarrow> Zfun f F"
```
```   422   unfolding Zfun_def by simp
```
```   423
```
```   424 lemma ZfunD:
```
```   425   "\<lbrakk>Zfun f F; 0 < r\<rbrakk> \<Longrightarrow> eventually (\<lambda>x. norm (f x) < r) F"
```
```   426   unfolding Zfun_def by simp
```
```   427
```
```   428 lemma Zfun_ssubst:
```
```   429   "eventually (\<lambda>x. f x = g x) F \<Longrightarrow> Zfun g F \<Longrightarrow> Zfun f F"
```
```   430   unfolding Zfun_def by (auto elim!: eventually_rev_mp)
```
```   431
```
```   432 lemma Zfun_zero: "Zfun (\<lambda>x. 0) F"
```
```   433   unfolding Zfun_def by simp
```
```   434
```
```   435 lemma Zfun_norm_iff: "Zfun (\<lambda>x. norm (f x)) F = Zfun (\<lambda>x. f x) F"
```
```   436   unfolding Zfun_def by simp
```
```   437
```
```   438 lemma Zfun_imp_Zfun:
```
```   439   assumes f: "Zfun f F"
```
```   440   assumes g: "eventually (\<lambda>x. norm (g x) \<le> norm (f x) * K) F"
```
```   441   shows "Zfun (\<lambda>x. g x) F"
```
```   442 proof (cases)
```
```   443   assume K: "0 < K"
```
```   444   show ?thesis
```
```   445   proof (rule ZfunI)
```
```   446     fix r::real assume "0 < r"
```
```   447     hence "0 < r / K"
```
```   448       using K by (rule divide_pos_pos)
```
```   449     then have "eventually (\<lambda>x. norm (f x) < r / K) F"
```
```   450       using ZfunD [OF f] by fast
```
```   451     with g show "eventually (\<lambda>x. norm (g x) < r) F"
```
```   452     proof (rule eventually_elim2)
```
```   453       fix x
```
```   454       assume *: "norm (g x) \<le> norm (f x) * K"
```
```   455       assume "norm (f x) < r / K"
```
```   456       hence "norm (f x) * K < r"
```
```   457         by (simp add: pos_less_divide_eq K)
```
```   458       thus "norm (g x) < r"
```
```   459         by (simp add: order_le_less_trans [OF *])
```
```   460     qed
```
```   461   qed
```
```   462 next
```
```   463   assume "\<not> 0 < K"
```
```   464   hence K: "K \<le> 0" by (simp only: not_less)
```
```   465   show ?thesis
```
```   466   proof (rule ZfunI)
```
```   467     fix r :: real
```
```   468     assume "0 < r"
```
```   469     from g show "eventually (\<lambda>x. norm (g x) < r) F"
```
```   470     proof (rule eventually_elim1)
```
```   471       fix x
```
```   472       assume "norm (g x) \<le> norm (f x) * K"
```
```   473       also have "\<dots> \<le> norm (f x) * 0"
```
```   474         using K norm_ge_zero by (rule mult_left_mono)
```
```   475       finally show "norm (g x) < r"
```
```   476         using `0 < r` by simp
```
```   477     qed
```
```   478   qed
```
```   479 qed
```
```   480
```
```   481 lemma Zfun_le: "\<lbrakk>Zfun g F; \<forall>x. norm (f x) \<le> norm (g x)\<rbrakk> \<Longrightarrow> Zfun f F"
```
```   482   by (erule_tac K="1" in Zfun_imp_Zfun, simp)
```
```   483
```
```   484 lemma Zfun_add:
```
```   485   assumes f: "Zfun f F" and g: "Zfun g F"
```
```   486   shows "Zfun (\<lambda>x. f x + g x) F"
```
```   487 proof (rule ZfunI)
```
```   488   fix r::real assume "0 < r"
```
```   489   hence r: "0 < r / 2" by simp
```
```   490   have "eventually (\<lambda>x. norm (f x) < r/2) F"
```
```   491     using f r by (rule ZfunD)
```
```   492   moreover
```
```   493   have "eventually (\<lambda>x. norm (g x) < r/2) F"
```
```   494     using g r by (rule ZfunD)
```
```   495   ultimately
```
```   496   show "eventually (\<lambda>x. norm (f x + g x) < r) F"
```
```   497   proof (rule eventually_elim2)
```
```   498     fix x
```
```   499     assume *: "norm (f x) < r/2" "norm (g x) < r/2"
```
```   500     have "norm (f x + g x) \<le> norm (f x) + norm (g x)"
```
```   501       by (rule norm_triangle_ineq)
```
```   502     also have "\<dots> < r/2 + r/2"
```
```   503       using * by (rule add_strict_mono)
```
```   504     finally show "norm (f x + g x) < r"
```
```   505       by simp
```
```   506   qed
```
```   507 qed
```
```   508
```
```   509 lemma Zfun_minus: "Zfun f F \<Longrightarrow> Zfun (\<lambda>x. - f x) F"
```
```   510   unfolding Zfun_def by simp
```
```   511
```
```   512 lemma Zfun_diff: "\<lbrakk>Zfun f F; Zfun g F\<rbrakk> \<Longrightarrow> Zfun (\<lambda>x. f x - g x) F"
```
```   513   by (simp only: diff_minus Zfun_add Zfun_minus)
```
```   514
```
```   515 lemma (in bounded_linear) Zfun:
```
```   516   assumes g: "Zfun g F"
```
```   517   shows "Zfun (\<lambda>x. f (g x)) F"
```
```   518 proof -
```
```   519   obtain K where "\<And>x. norm (f x) \<le> norm x * K"
```
```   520     using bounded by fast
```
```   521   then have "eventually (\<lambda>x. norm (f (g x)) \<le> norm (g x) * K) F"
```
```   522     by simp
```
```   523   with g show ?thesis
```
```   524     by (rule Zfun_imp_Zfun)
```
```   525 qed
```
```   526
```
```   527 lemma (in bounded_bilinear) Zfun:
```
```   528   assumes f: "Zfun f F"
```
```   529   assumes g: "Zfun g F"
```
```   530   shows "Zfun (\<lambda>x. f x ** g x) F"
```
```   531 proof (rule ZfunI)
```
```   532   fix r::real assume r: "0 < r"
```
```   533   obtain K where K: "0 < K"
```
```   534     and norm_le: "\<And>x y. norm (x ** y) \<le> norm x * norm y * K"
```
```   535     using pos_bounded by fast
```
```   536   from K have K': "0 < inverse K"
```
```   537     by (rule positive_imp_inverse_positive)
```
```   538   have "eventually (\<lambda>x. norm (f x) < r) F"
```
```   539     using f r by (rule ZfunD)
```
```   540   moreover
```
```   541   have "eventually (\<lambda>x. norm (g x) < inverse K) F"
```
```   542     using g K' by (rule ZfunD)
```
```   543   ultimately
```
```   544   show "eventually (\<lambda>x. norm (f x ** g x) < r) F"
```
```   545   proof (rule eventually_elim2)
```
```   546     fix x
```
```   547     assume *: "norm (f x) < r" "norm (g x) < inverse K"
```
```   548     have "norm (f x ** g x) \<le> norm (f x) * norm (g x) * K"
```
```   549       by (rule norm_le)
```
```   550     also have "norm (f x) * norm (g x) * K < r * inverse K * K"
```
```   551       by (intro mult_strict_right_mono mult_strict_mono' norm_ge_zero * K)
```
```   552     also from K have "r * inverse K * K = r"
```
```   553       by simp
```
```   554     finally show "norm (f x ** g x) < r" .
```
```   555   qed
```
```   556 qed
```
```   557
```
```   558 lemma (in bounded_bilinear) Zfun_left:
```
```   559   "Zfun f F \<Longrightarrow> Zfun (\<lambda>x. f x ** a) F"
```
```   560   by (rule bounded_linear_left [THEN bounded_linear.Zfun])
```
```   561
```
```   562 lemma (in bounded_bilinear) Zfun_right:
```
```   563   "Zfun f F \<Longrightarrow> Zfun (\<lambda>x. a ** f x) F"
```
```   564   by (rule bounded_linear_right [THEN bounded_linear.Zfun])
```
```   565
```
```   566 lemmas Zfun_mult = bounded_bilinear.Zfun [OF bounded_bilinear_mult]
```
```   567 lemmas Zfun_mult_right = bounded_bilinear.Zfun_right [OF bounded_bilinear_mult]
```
```   568 lemmas Zfun_mult_left = bounded_bilinear.Zfun_left [OF bounded_bilinear_mult]
```
```   569
```
```   570
```
```   571 subsection {* Limits *}
```
```   572
```
```   573 definition (in topological_space)
```
```   574   tendsto :: "('b \<Rightarrow> 'a) \<Rightarrow> 'a \<Rightarrow> 'b filter \<Rightarrow> bool" (infixr "--->" 55) where
```
```   575   "(f ---> l) F \<longleftrightarrow> (\<forall>S. open S \<longrightarrow> l \<in> S \<longrightarrow> eventually (\<lambda>x. f x \<in> S) F)"
```
```   576
```
```   577 definition real_tendsto_inf :: "('a \<Rightarrow> real) \<Rightarrow> 'a filter \<Rightarrow> bool" where
```
```   578   "real_tendsto_inf f F \<equiv> \<forall>x. eventually (\<lambda>y. x < f y) F"
```
```   579
```
```   580 ML {*
```
```   581 structure Tendsto_Intros = Named_Thms
```
```   582 (
```
```   583   val name = @{binding tendsto_intros}
```
```   584   val description = "introduction rules for tendsto"
```
```   585 )
```
```   586 *}
```
```   587
```
```   588 setup Tendsto_Intros.setup
```
```   589
```
```   590 lemma tendsto_mono: "F \<le> F' \<Longrightarrow> (f ---> l) F' \<Longrightarrow> (f ---> l) F"
```
```   591   unfolding tendsto_def le_filter_def by fast
```
```   592
```
```   593 lemma topological_tendstoI:
```
```   594   "(\<And>S. open S \<Longrightarrow> l \<in> S \<Longrightarrow> eventually (\<lambda>x. f x \<in> S) F)
```
```   595     \<Longrightarrow> (f ---> l) F"
```
```   596   unfolding tendsto_def by auto
```
```   597
```
```   598 lemma topological_tendstoD:
```
```   599   "(f ---> l) F \<Longrightarrow> open S \<Longrightarrow> l \<in> S \<Longrightarrow> eventually (\<lambda>x. f x \<in> S) F"
```
```   600   unfolding tendsto_def by auto
```
```   601
```
```   602 lemma tendstoI:
```
```   603   assumes "\<And>e. 0 < e \<Longrightarrow> eventually (\<lambda>x. dist (f x) l < e) F"
```
```   604   shows "(f ---> l) F"
```
```   605   apply (rule topological_tendstoI)
```
```   606   apply (simp add: open_dist)
```
```   607   apply (drule (1) bspec, clarify)
```
```   608   apply (drule assms)
```
```   609   apply (erule eventually_elim1, simp)
```
```   610   done
```
```   611
```
```   612 lemma tendstoD:
```
```   613   "(f ---> l) F \<Longrightarrow> 0 < e \<Longrightarrow> eventually (\<lambda>x. dist (f x) l < e) F"
```
```   614   apply (drule_tac S="{x. dist x l < e}" in topological_tendstoD)
```
```   615   apply (clarsimp simp add: open_dist)
```
```   616   apply (rule_tac x="e - dist x l" in exI, clarsimp)
```
```   617   apply (simp only: less_diff_eq)
```
```   618   apply (erule le_less_trans [OF dist_triangle])
```
```   619   apply simp
```
```   620   apply simp
```
```   621   done
```
```   622
```
```   623 lemma tendsto_iff:
```
```   624   "(f ---> l) F \<longleftrightarrow> (\<forall>e>0. eventually (\<lambda>x. dist (f x) l < e) F)"
```
```   625   using tendstoI tendstoD by fast
```
```   626
```
```   627 lemma tendsto_Zfun_iff: "(f ---> a) F = Zfun (\<lambda>x. f x - a) F"
```
```   628   by (simp only: tendsto_iff Zfun_def dist_norm)
```
```   629
```
```   630 lemma tendsto_bot [simp]: "(f ---> a) bot"
```
```   631   unfolding tendsto_def by simp
```
```   632
```
```   633 lemma tendsto_ident_at [tendsto_intros]: "((\<lambda>x. x) ---> a) (at a)"
```
```   634   unfolding tendsto_def eventually_at_topological by auto
```
```   635
```
```   636 lemma tendsto_ident_at_within [tendsto_intros]:
```
```   637   "((\<lambda>x. x) ---> a) (at a within S)"
```
```   638   unfolding tendsto_def eventually_within eventually_at_topological by auto
```
```   639
```
```   640 lemma tendsto_const [tendsto_intros]: "((\<lambda>x. k) ---> k) F"
```
```   641   by (simp add: tendsto_def)
```
```   642
```
```   643 lemma tendsto_unique:
```
```   644   fixes f :: "'a \<Rightarrow> 'b::t2_space"
```
```   645   assumes "\<not> trivial_limit F" and "(f ---> a) F" and "(f ---> b) F"
```
```   646   shows "a = b"
```
```   647 proof (rule ccontr)
```
```   648   assume "a \<noteq> b"
```
```   649   obtain U V where "open U" "open V" "a \<in> U" "b \<in> V" "U \<inter> V = {}"
```
```   650     using hausdorff [OF `a \<noteq> b`] by fast
```
```   651   have "eventually (\<lambda>x. f x \<in> U) F"
```
```   652     using `(f ---> a) F` `open U` `a \<in> U` by (rule topological_tendstoD)
```
```   653   moreover
```
```   654   have "eventually (\<lambda>x. f x \<in> V) F"
```
```   655     using `(f ---> b) F` `open V` `b \<in> V` by (rule topological_tendstoD)
```
```   656   ultimately
```
```   657   have "eventually (\<lambda>x. False) F"
```
```   658   proof (rule eventually_elim2)
```
```   659     fix x
```
```   660     assume "f x \<in> U" "f x \<in> V"
```
```   661     hence "f x \<in> U \<inter> V" by simp
```
```   662     with `U \<inter> V = {}` show "False" by simp
```
```   663   qed
```
```   664   with `\<not> trivial_limit F` show "False"
```
```   665     by (simp add: trivial_limit_def)
```
```   666 qed
```
```   667
```
```   668 lemma tendsto_const_iff:
```
```   669   fixes a b :: "'a::t2_space"
```
```   670   assumes "\<not> trivial_limit F" shows "((\<lambda>x. a) ---> b) F \<longleftrightarrow> a = b"
```
```   671   by (safe intro!: tendsto_const tendsto_unique [OF assms tendsto_const])
```
```   672
```
```   673 lemma tendsto_compose:
```
```   674   assumes g: "(g ---> g l) (at l)"
```
```   675   assumes f: "(f ---> l) F"
```
```   676   shows "((\<lambda>x. g (f x)) ---> g l) F"
```
```   677 proof (rule topological_tendstoI)
```
```   678   fix B assume B: "open B" "g l \<in> B"
```
```   679   obtain A where A: "open A" "l \<in> A"
```
```   680     and gB: "\<forall>y. y \<in> A \<longrightarrow> g y \<in> B"
```
```   681     using topological_tendstoD [OF g B] B(2)
```
```   682     unfolding eventually_at_topological by fast
```
```   683   hence "\<forall>x. f x \<in> A \<longrightarrow> g (f x) \<in> B" by simp
```
```   684   from this topological_tendstoD [OF f A]
```
```   685   show "eventually (\<lambda>x. g (f x) \<in> B) F"
```
```   686     by (rule eventually_mono)
```
```   687 qed
```
```   688
```
```   689 lemma tendsto_compose_eventually:
```
```   690   assumes g: "(g ---> m) (at l)"
```
```   691   assumes f: "(f ---> l) F"
```
```   692   assumes inj: "eventually (\<lambda>x. f x \<noteq> l) F"
```
```   693   shows "((\<lambda>x. g (f x)) ---> m) F"
```
```   694 proof (rule topological_tendstoI)
```
```   695   fix B assume B: "open B" "m \<in> B"
```
```   696   obtain A where A: "open A" "l \<in> A"
```
```   697     and gB: "\<And>y. y \<in> A \<Longrightarrow> y \<noteq> l \<Longrightarrow> g y \<in> B"
```
```   698     using topological_tendstoD [OF g B]
```
```   699     unfolding eventually_at_topological by fast
```
```   700   show "eventually (\<lambda>x. g (f x) \<in> B) F"
```
```   701     using topological_tendstoD [OF f A] inj
```
```   702     by (rule eventually_elim2) (simp add: gB)
```
```   703 qed
```
```   704
```
```   705 lemma metric_tendsto_imp_tendsto:
```
```   706   assumes f: "(f ---> a) F"
```
```   707   assumes le: "eventually (\<lambda>x. dist (g x) b \<le> dist (f x) a) F"
```
```   708   shows "(g ---> b) F"
```
```   709 proof (rule tendstoI)
```
```   710   fix e :: real assume "0 < e"
```
```   711   with f have "eventually (\<lambda>x. dist (f x) a < e) F" by (rule tendstoD)
```
```   712   with le show "eventually (\<lambda>x. dist (g x) b < e) F"
```
```   713     using le_less_trans by (rule eventually_elim2)
```
```   714 qed
```
```   715
```
```   716 lemma real_tendsto_inf_real: "real_tendsto_inf real sequentially"
```
```   717 proof (unfold real_tendsto_inf_def, rule allI)
```
```   718   fix x show "eventually (\<lambda>y. x < real y) sequentially"
```
```   719     by (rule eventually_sequentiallyI[of "natceiling (x + 1)"])
```
```   720         (simp add: natceiling_le_eq)
```
```   721 qed
```
```   722
```
```   723
```
```   724
```
```   725 subsubsection {* Distance and norms *}
```
```   726
```
```   727 lemma tendsto_dist [tendsto_intros]:
```
```   728   assumes f: "(f ---> l) F" and g: "(g ---> m) F"
```
```   729   shows "((\<lambda>x. dist (f x) (g x)) ---> dist l m) F"
```
```   730 proof (rule tendstoI)
```
```   731   fix e :: real assume "0 < e"
```
```   732   hence e2: "0 < e/2" by simp
```
```   733   from tendstoD [OF f e2] tendstoD [OF g e2]
```
```   734   show "eventually (\<lambda>x. dist (dist (f x) (g x)) (dist l m) < e) F"
```
```   735   proof (rule eventually_elim2)
```
```   736     fix x assume "dist (f x) l < e/2" "dist (g x) m < e/2"
```
```   737     then show "dist (dist (f x) (g x)) (dist l m) < e"
```
```   738       unfolding dist_real_def
```
```   739       using dist_triangle2 [of "f x" "g x" "l"]
```
```   740       using dist_triangle2 [of "g x" "l" "m"]
```
```   741       using dist_triangle3 [of "l" "m" "f x"]
```
```   742       using dist_triangle [of "f x" "m" "g x"]
```
```   743       by arith
```
```   744   qed
```
```   745 qed
```
```   746
```
```   747 lemma norm_conv_dist: "norm x = dist x 0"
```
```   748   unfolding dist_norm by simp
```
```   749
```
```   750 lemma tendsto_norm [tendsto_intros]:
```
```   751   "(f ---> a) F \<Longrightarrow> ((\<lambda>x. norm (f x)) ---> norm a) F"
```
```   752   unfolding norm_conv_dist by (intro tendsto_intros)
```
```   753
```
```   754 lemma tendsto_norm_zero:
```
```   755   "(f ---> 0) F \<Longrightarrow> ((\<lambda>x. norm (f x)) ---> 0) F"
```
```   756   by (drule tendsto_norm, simp)
```
```   757
```
```   758 lemma tendsto_norm_zero_cancel:
```
```   759   "((\<lambda>x. norm (f x)) ---> 0) F \<Longrightarrow> (f ---> 0) F"
```
```   760   unfolding tendsto_iff dist_norm by simp
```
```   761
```
```   762 lemma tendsto_norm_zero_iff:
```
```   763   "((\<lambda>x. norm (f x)) ---> 0) F \<longleftrightarrow> (f ---> 0) F"
```
```   764   unfolding tendsto_iff dist_norm by simp
```
```   765
```
```   766 lemma tendsto_rabs [tendsto_intros]:
```
```   767   "(f ---> (l::real)) F \<Longrightarrow> ((\<lambda>x. \<bar>f x\<bar>) ---> \<bar>l\<bar>) F"
```
```   768   by (fold real_norm_def, rule tendsto_norm)
```
```   769
```
```   770 lemma tendsto_rabs_zero:
```
```   771   "(f ---> (0::real)) F \<Longrightarrow> ((\<lambda>x. \<bar>f x\<bar>) ---> 0) F"
```
```   772   by (fold real_norm_def, rule tendsto_norm_zero)
```
```   773
```
```   774 lemma tendsto_rabs_zero_cancel:
```
```   775   "((\<lambda>x. \<bar>f x\<bar>) ---> (0::real)) F \<Longrightarrow> (f ---> 0) F"
```
```   776   by (fold real_norm_def, rule tendsto_norm_zero_cancel)
```
```   777
```
```   778 lemma tendsto_rabs_zero_iff:
```
```   779   "((\<lambda>x. \<bar>f x\<bar>) ---> (0::real)) F \<longleftrightarrow> (f ---> 0) F"
```
```   780   by (fold real_norm_def, rule tendsto_norm_zero_iff)
```
```   781
```
```   782 subsubsection {* Addition and subtraction *}
```
```   783
```
```   784 lemma tendsto_add [tendsto_intros]:
```
```   785   fixes a b :: "'a::real_normed_vector"
```
```   786   shows "\<lbrakk>(f ---> a) F; (g ---> b) F\<rbrakk> \<Longrightarrow> ((\<lambda>x. f x + g x) ---> a + b) F"
```
```   787   by (simp only: tendsto_Zfun_iff add_diff_add Zfun_add)
```
```   788
```
```   789 lemma tendsto_add_zero:
```
```   790   fixes f g :: "'a::type \<Rightarrow> 'b::real_normed_vector"
```
```   791   shows "\<lbrakk>(f ---> 0) F; (g ---> 0) F\<rbrakk> \<Longrightarrow> ((\<lambda>x. f x + g x) ---> 0) F"
```
```   792   by (drule (1) tendsto_add, simp)
```
```   793
```
```   794 lemma tendsto_minus [tendsto_intros]:
```
```   795   fixes a :: "'a::real_normed_vector"
```
```   796   shows "(f ---> a) F \<Longrightarrow> ((\<lambda>x. - f x) ---> - a) F"
```
```   797   by (simp only: tendsto_Zfun_iff minus_diff_minus Zfun_minus)
```
```   798
```
```   799 lemma tendsto_minus_cancel:
```
```   800   fixes a :: "'a::real_normed_vector"
```
```   801   shows "((\<lambda>x. - f x) ---> - a) F \<Longrightarrow> (f ---> a) F"
```
```   802   by (drule tendsto_minus, simp)
```
```   803
```
```   804 lemma tendsto_diff [tendsto_intros]:
```
```   805   fixes a b :: "'a::real_normed_vector"
```
```   806   shows "\<lbrakk>(f ---> a) F; (g ---> b) F\<rbrakk> \<Longrightarrow> ((\<lambda>x. f x - g x) ---> a - b) F"
```
```   807   by (simp add: diff_minus tendsto_add tendsto_minus)
```
```   808
```
```   809 lemma tendsto_setsum [tendsto_intros]:
```
```   810   fixes f :: "'a \<Rightarrow> 'b \<Rightarrow> 'c::real_normed_vector"
```
```   811   assumes "\<And>i. i \<in> S \<Longrightarrow> (f i ---> a i) F"
```
```   812   shows "((\<lambda>x. \<Sum>i\<in>S. f i x) ---> (\<Sum>i\<in>S. a i)) F"
```
```   813 proof (cases "finite S")
```
```   814   assume "finite S" thus ?thesis using assms
```
```   815     by (induct, simp add: tendsto_const, simp add: tendsto_add)
```
```   816 next
```
```   817   assume "\<not> finite S" thus ?thesis
```
```   818     by (simp add: tendsto_const)
```
```   819 qed
```
```   820
```
```   821 lemma real_tendsto_sandwich:
```
```   822   fixes f g h :: "'a \<Rightarrow> real"
```
```   823   assumes ev: "eventually (\<lambda>n. f n \<le> g n) net" "eventually (\<lambda>n. g n \<le> h n) net"
```
```   824   assumes lim: "(f ---> c) net" "(h ---> c) net"
```
```   825   shows "(g ---> c) net"
```
```   826 proof -
```
```   827   have "((\<lambda>n. g n - f n) ---> 0) net"
```
```   828   proof (rule metric_tendsto_imp_tendsto)
```
```   829     show "eventually (\<lambda>n. dist (g n - f n) 0 \<le> dist (h n - f n) 0) net"
```
```   830       using ev by (rule eventually_elim2) (simp add: dist_real_def)
```
```   831     show "((\<lambda>n. h n - f n) ---> 0) net"
```
```   832       using tendsto_diff[OF lim(2,1)] by simp
```
```   833   qed
```
```   834   from tendsto_add[OF this lim(1)] show ?thesis by simp
```
```   835 qed
```
```   836
```
```   837 subsubsection {* Linear operators and multiplication *}
```
```   838
```
```   839 lemma (in bounded_linear) tendsto:
```
```   840   "(g ---> a) F \<Longrightarrow> ((\<lambda>x. f (g x)) ---> f a) F"
```
```   841   by (simp only: tendsto_Zfun_iff diff [symmetric] Zfun)
```
```   842
```
```   843 lemma (in bounded_linear) tendsto_zero:
```
```   844   "(g ---> 0) F \<Longrightarrow> ((\<lambda>x. f (g x)) ---> 0) F"
```
```   845   by (drule tendsto, simp only: zero)
```
```   846
```
```   847 lemma (in bounded_bilinear) tendsto:
```
```   848   "\<lbrakk>(f ---> a) F; (g ---> b) F\<rbrakk> \<Longrightarrow> ((\<lambda>x. f x ** g x) ---> a ** b) F"
```
```   849   by (simp only: tendsto_Zfun_iff prod_diff_prod
```
```   850                  Zfun_add Zfun Zfun_left Zfun_right)
```
```   851
```
```   852 lemma (in bounded_bilinear) tendsto_zero:
```
```   853   assumes f: "(f ---> 0) F"
```
```   854   assumes g: "(g ---> 0) F"
```
```   855   shows "((\<lambda>x. f x ** g x) ---> 0) F"
```
```   856   using tendsto [OF f g] by (simp add: zero_left)
```
```   857
```
```   858 lemma (in bounded_bilinear) tendsto_left_zero:
```
```   859   "(f ---> 0) F \<Longrightarrow> ((\<lambda>x. f x ** c) ---> 0) F"
```
```   860   by (rule bounded_linear.tendsto_zero [OF bounded_linear_left])
```
```   861
```
```   862 lemma (in bounded_bilinear) tendsto_right_zero:
```
```   863   "(f ---> 0) F \<Longrightarrow> ((\<lambda>x. c ** f x) ---> 0) F"
```
```   864   by (rule bounded_linear.tendsto_zero [OF bounded_linear_right])
```
```   865
```
```   866 lemmas tendsto_of_real [tendsto_intros] =
```
```   867   bounded_linear.tendsto [OF bounded_linear_of_real]
```
```   868
```
```   869 lemmas tendsto_scaleR [tendsto_intros] =
```
```   870   bounded_bilinear.tendsto [OF bounded_bilinear_scaleR]
```
```   871
```
```   872 lemmas tendsto_mult [tendsto_intros] =
```
```   873   bounded_bilinear.tendsto [OF bounded_bilinear_mult]
```
```   874
```
```   875 lemmas tendsto_mult_zero =
```
```   876   bounded_bilinear.tendsto_zero [OF bounded_bilinear_mult]
```
```   877
```
```   878 lemmas tendsto_mult_left_zero =
```
```   879   bounded_bilinear.tendsto_left_zero [OF bounded_bilinear_mult]
```
```   880
```
```   881 lemmas tendsto_mult_right_zero =
```
```   882   bounded_bilinear.tendsto_right_zero [OF bounded_bilinear_mult]
```
```   883
```
```   884 lemma tendsto_power [tendsto_intros]:
```
```   885   fixes f :: "'a \<Rightarrow> 'b::{power,real_normed_algebra}"
```
```   886   shows "(f ---> a) F \<Longrightarrow> ((\<lambda>x. f x ^ n) ---> a ^ n) F"
```
```   887   by (induct n) (simp_all add: tendsto_const tendsto_mult)
```
```   888
```
```   889 lemma tendsto_setprod [tendsto_intros]:
```
```   890   fixes f :: "'a \<Rightarrow> 'b \<Rightarrow> 'c::{real_normed_algebra,comm_ring_1}"
```
```   891   assumes "\<And>i. i \<in> S \<Longrightarrow> (f i ---> L i) F"
```
```   892   shows "((\<lambda>x. \<Prod>i\<in>S. f i x) ---> (\<Prod>i\<in>S. L i)) F"
```
```   893 proof (cases "finite S")
```
```   894   assume "finite S" thus ?thesis using assms
```
```   895     by (induct, simp add: tendsto_const, simp add: tendsto_mult)
```
```   896 next
```
```   897   assume "\<not> finite S" thus ?thesis
```
```   898     by (simp add: tendsto_const)
```
```   899 qed
```
```   900
```
```   901 subsubsection {* Inverse and division *}
```
```   902
```
```   903 lemma (in bounded_bilinear) Zfun_prod_Bfun:
```
```   904   assumes f: "Zfun f F"
```
```   905   assumes g: "Bfun g F"
```
```   906   shows "Zfun (\<lambda>x. f x ** g x) F"
```
```   907 proof -
```
```   908   obtain K where K: "0 \<le> K"
```
```   909     and norm_le: "\<And>x y. norm (x ** y) \<le> norm x * norm y * K"
```
```   910     using nonneg_bounded by fast
```
```   911   obtain B where B: "0 < B"
```
```   912     and norm_g: "eventually (\<lambda>x. norm (g x) \<le> B) F"
```
```   913     using g by (rule BfunE)
```
```   914   have "eventually (\<lambda>x. norm (f x ** g x) \<le> norm (f x) * (B * K)) F"
```
```   915   using norm_g proof (rule eventually_elim1)
```
```   916     fix x
```
```   917     assume *: "norm (g x) \<le> B"
```
```   918     have "norm (f x ** g x) \<le> norm (f x) * norm (g x) * K"
```
```   919       by (rule norm_le)
```
```   920     also have "\<dots> \<le> norm (f x) * B * K"
```
```   921       by (intro mult_mono' order_refl norm_g norm_ge_zero
```
```   922                 mult_nonneg_nonneg K *)
```
```   923     also have "\<dots> = norm (f x) * (B * K)"
```
```   924       by (rule mult_assoc)
```
```   925     finally show "norm (f x ** g x) \<le> norm (f x) * (B * K)" .
```
```   926   qed
```
```   927   with f show ?thesis
```
```   928     by (rule Zfun_imp_Zfun)
```
```   929 qed
```
```   930
```
```   931 lemma (in bounded_bilinear) flip:
```
```   932   "bounded_bilinear (\<lambda>x y. y ** x)"
```
```   933   apply default
```
```   934   apply (rule add_right)
```
```   935   apply (rule add_left)
```
```   936   apply (rule scaleR_right)
```
```   937   apply (rule scaleR_left)
```
```   938   apply (subst mult_commute)
```
```   939   using bounded by fast
```
```   940
```
```   941 lemma (in bounded_bilinear) Bfun_prod_Zfun:
```
```   942   assumes f: "Bfun f F"
```
```   943   assumes g: "Zfun g F"
```
```   944   shows "Zfun (\<lambda>x. f x ** g x) F"
```
```   945   using flip g f by (rule bounded_bilinear.Zfun_prod_Bfun)
```
```   946
```
```   947 lemma Bfun_inverse_lemma:
```
```   948   fixes x :: "'a::real_normed_div_algebra"
```
```   949   shows "\<lbrakk>r \<le> norm x; 0 < r\<rbrakk> \<Longrightarrow> norm (inverse x) \<le> inverse r"
```
```   950   apply (subst nonzero_norm_inverse, clarsimp)
```
```   951   apply (erule (1) le_imp_inverse_le)
```
```   952   done
```
```   953
```
```   954 lemma Bfun_inverse:
```
```   955   fixes a :: "'a::real_normed_div_algebra"
```
```   956   assumes f: "(f ---> a) F"
```
```   957   assumes a: "a \<noteq> 0"
```
```   958   shows "Bfun (\<lambda>x. inverse (f x)) F"
```
```   959 proof -
```
```   960   from a have "0 < norm a" by simp
```
```   961   hence "\<exists>r>0. r < norm a" by (rule dense)
```
```   962   then obtain r where r1: "0 < r" and r2: "r < norm a" by fast
```
```   963   have "eventually (\<lambda>x. dist (f x) a < r) F"
```
```   964     using tendstoD [OF f r1] by fast
```
```   965   hence "eventually (\<lambda>x. norm (inverse (f x)) \<le> inverse (norm a - r)) F"
```
```   966   proof (rule eventually_elim1)
```
```   967     fix x
```
```   968     assume "dist (f x) a < r"
```
```   969     hence 1: "norm (f x - a) < r"
```
```   970       by (simp add: dist_norm)
```
```   971     hence 2: "f x \<noteq> 0" using r2 by auto
```
```   972     hence "norm (inverse (f x)) = inverse (norm (f x))"
```
```   973       by (rule nonzero_norm_inverse)
```
```   974     also have "\<dots> \<le> inverse (norm a - r)"
```
```   975     proof (rule le_imp_inverse_le)
```
```   976       show "0 < norm a - r" using r2 by simp
```
```   977     next
```
```   978       have "norm a - norm (f x) \<le> norm (a - f x)"
```
```   979         by (rule norm_triangle_ineq2)
```
```   980       also have "\<dots> = norm (f x - a)"
```
```   981         by (rule norm_minus_commute)
```
```   982       also have "\<dots> < r" using 1 .
```
```   983       finally show "norm a - r \<le> norm (f x)" by simp
```
```   984     qed
```
```   985     finally show "norm (inverse (f x)) \<le> inverse (norm a - r)" .
```
```   986   qed
```
```   987   thus ?thesis by (rule BfunI)
```
```   988 qed
```
```   989
```
```   990 lemma tendsto_inverse [tendsto_intros]:
```
```   991   fixes a :: "'a::real_normed_div_algebra"
```
```   992   assumes f: "(f ---> a) F"
```
```   993   assumes a: "a \<noteq> 0"
```
```   994   shows "((\<lambda>x. inverse (f x)) ---> inverse a) F"
```
```   995 proof -
```
```   996   from a have "0 < norm a" by simp
```
```   997   with f have "eventually (\<lambda>x. dist (f x) a < norm a) F"
```
```   998     by (rule tendstoD)
```
```   999   then have "eventually (\<lambda>x. f x \<noteq> 0) F"
```
```  1000     unfolding dist_norm by (auto elim!: eventually_elim1)
```
```  1001   with a have "eventually (\<lambda>x. inverse (f x) - inverse a =
```
```  1002     - (inverse (f x) * (f x - a) * inverse a)) F"
```
```  1003     by (auto elim!: eventually_elim1 simp: inverse_diff_inverse)
```
```  1004   moreover have "Zfun (\<lambda>x. - (inverse (f x) * (f x - a) * inverse a)) F"
```
```  1005     by (intro Zfun_minus Zfun_mult_left
```
```  1006       bounded_bilinear.Bfun_prod_Zfun [OF bounded_bilinear_mult]
```
```  1007       Bfun_inverse [OF f a] f [unfolded tendsto_Zfun_iff])
```
```  1008   ultimately show ?thesis
```
```  1009     unfolding tendsto_Zfun_iff by (rule Zfun_ssubst)
```
```  1010 qed
```
```  1011
```
```  1012 lemma tendsto_divide [tendsto_intros]:
```
```  1013   fixes a b :: "'a::real_normed_field"
```
```  1014   shows "\<lbrakk>(f ---> a) F; (g ---> b) F; b \<noteq> 0\<rbrakk>
```
```  1015     \<Longrightarrow> ((\<lambda>x. f x / g x) ---> a / b) F"
```
```  1016   by (simp add: tendsto_mult tendsto_inverse divide_inverse)
```
```  1017
```
```  1018 lemma tendsto_sgn [tendsto_intros]:
```
```  1019   fixes l :: "'a::real_normed_vector"
```
```  1020   shows "\<lbrakk>(f ---> l) F; l \<noteq> 0\<rbrakk> \<Longrightarrow> ((\<lambda>x. sgn (f x)) ---> sgn l) F"
```
```  1021   unfolding sgn_div_norm by (simp add: tendsto_intros)
```
```  1022
```
```  1023 end
```