src/HOL/Multivariate_Analysis/Topology_Euclidean_Space.thy
author paulson <lp15@cam.ac.uk>
Tue Nov 17 12:32:08 2015 +0000 (2015-11-17)
changeset 61694 6571c78c9667
parent 61609 77b453bd616f
child 61699 a81dc5c4d6a9
permissions -rw-r--r--
Removed some legacy theorems; minor adjustments to simplification rules; new material on homotopic paths
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(*  title:      HOL/Library/Topology_Euclidian_Space.thy
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    Author:     Amine Chaieb, University of Cambridge
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    Author:     Robert Himmelmann, TU Muenchen
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    Author:     Brian Huffman, Portland State University
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*)
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section \<open>Elementary topology in Euclidean space.\<close>
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theory Topology_Euclidean_Space
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imports
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  Complex_Main
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  "~~/src/HOL/Library/Countable_Set"
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  "~~/src/HOL/Library/FuncSet"
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  Linear_Algebra
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  Norm_Arith
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begin
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lemma dist_0_norm:
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  fixes x :: "'a::real_normed_vector"
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  shows "dist 0 x = norm x"
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unfolding dist_norm by simp
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lemma dist_double: "dist x y < d / 2 \<Longrightarrow> dist x z < d / 2 \<Longrightarrow> dist y z < d"
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  using dist_triangle[of y z x] by (simp add: dist_commute)
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(* LEGACY *)
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lemma lim_subseq: "subseq r \<Longrightarrow> s ----> l \<Longrightarrow> (s \<circ> r) ----> l"
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  by (rule LIMSEQ_subseq_LIMSEQ)
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lemma countable_PiE:
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  "finite I \<Longrightarrow> (\<And>i. i \<in> I \<Longrightarrow> countable (F i)) \<Longrightarrow> countable (PiE I F)"
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  by (induct I arbitrary: F rule: finite_induct) (auto simp: PiE_insert_eq)
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lemma Lim_within_open:
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  fixes f :: "'a::topological_space \<Rightarrow> 'b::topological_space"
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  shows "a \<in> S \<Longrightarrow> open S \<Longrightarrow> (f ---> l)(at a within S) \<longleftrightarrow> (f ---> l)(at a)"
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  by (fact tendsto_within_open)
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lemma continuous_on_union:
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  "closed s \<Longrightarrow> closed t \<Longrightarrow> continuous_on s f \<Longrightarrow> continuous_on t f \<Longrightarrow> continuous_on (s \<union> t) f"
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  by (fact continuous_on_closed_Un)
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lemma continuous_on_cases:
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  "closed s \<Longrightarrow> closed t \<Longrightarrow> continuous_on s f \<Longrightarrow> continuous_on t g \<Longrightarrow>
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    \<forall>x. (x\<in>s \<and> \<not> P x) \<or> (x \<in> t \<and> P x) \<longrightarrow> f x = g x \<Longrightarrow>
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    continuous_on (s \<union> t) (\<lambda>x. if P x then f x else g x)"
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  by (rule continuous_on_If) auto
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subsection \<open>Topological Basis\<close>
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context topological_space
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begin
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definition "topological_basis B \<longleftrightarrow>
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  (\<forall>b\<in>B. open b) \<and> (\<forall>x. open x \<longrightarrow> (\<exists>B'. B' \<subseteq> B \<and> \<Union>B' = x))"
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lemma topological_basis:
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  "topological_basis B \<longleftrightarrow> (\<forall>x. open x \<longleftrightarrow> (\<exists>B'. B' \<subseteq> B \<and> \<Union>B' = x))"
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  unfolding topological_basis_def
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  apply safe
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     apply fastforce
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    apply fastforce
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   apply (erule_tac x="x" in allE)
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   apply simp
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   apply (rule_tac x="{x}" in exI)
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  apply auto
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  done
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lemma topological_basis_iff:
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  assumes "\<And>B'. B' \<in> B \<Longrightarrow> open B'"
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  shows "topological_basis B \<longleftrightarrow> (\<forall>O'. open O' \<longrightarrow> (\<forall>x\<in>O'. \<exists>B'\<in>B. x \<in> B' \<and> B' \<subseteq> O'))"
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    (is "_ \<longleftrightarrow> ?rhs")
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proof safe
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  fix O' and x::'a
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  assume H: "topological_basis B" "open O'" "x \<in> O'"
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  then have "(\<exists>B'\<subseteq>B. \<Union>B' = O')" by (simp add: topological_basis_def)
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  then obtain B' where "B' \<subseteq> B" "O' = \<Union>B'" by auto
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  then show "\<exists>B'\<in>B. x \<in> B' \<and> B' \<subseteq> O'" using H by auto
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next
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  assume H: ?rhs
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  show "topological_basis B"
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    using assms unfolding topological_basis_def
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  proof safe
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    fix O' :: "'a set"
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    assume "open O'"
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    with H obtain f where "\<forall>x\<in>O'. f x \<in> B \<and> x \<in> f x \<and> f x \<subseteq> O'"
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      by (force intro: bchoice simp: Bex_def)
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    then show "\<exists>B'\<subseteq>B. \<Union>B' = O'"
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      by (auto intro: exI[where x="{f x |x. x \<in> O'}"])
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  qed
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qed
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lemma topological_basisI:
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  assumes "\<And>B'. B' \<in> B \<Longrightarrow> open B'"
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    and "\<And>O' x. open O' \<Longrightarrow> x \<in> O' \<Longrightarrow> \<exists>B'\<in>B. x \<in> B' \<and> B' \<subseteq> O'"
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  shows "topological_basis B"
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  using assms by (subst topological_basis_iff) auto
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lemma topological_basisE:
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  fixes O'
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  assumes "topological_basis B"
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    and "open O'"
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    and "x \<in> O'"
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  obtains B' where "B' \<in> B" "x \<in> B'" "B' \<subseteq> O'"
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proof atomize_elim
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  from assms have "\<And>B'. B'\<in>B \<Longrightarrow> open B'"
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    by (simp add: topological_basis_def)
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  with topological_basis_iff assms
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  show  "\<exists>B'. B' \<in> B \<and> x \<in> B' \<and> B' \<subseteq> O'"
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    using assms by (simp add: Bex_def)
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qed
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lemma topological_basis_open:
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  assumes "topological_basis B"
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    and "X \<in> B"
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  shows "open X"
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  using assms by (simp add: topological_basis_def)
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lemma topological_basis_imp_subbasis:
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  assumes B: "topological_basis B"
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  shows "open = generate_topology B"
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proof (intro ext iffI)
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  fix S :: "'a set"
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  assume "open S"
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  with B obtain B' where "B' \<subseteq> B" "S = \<Union>B'"
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    unfolding topological_basis_def by blast
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  then show "generate_topology B S"
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    by (auto intro: generate_topology.intros dest: topological_basis_open)
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next
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  fix S :: "'a set"
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  assume "generate_topology B S"
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  then show "open S"
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    by induct (auto dest: topological_basis_open[OF B])
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qed
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lemma basis_dense:
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  fixes B :: "'a set set"
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    and f :: "'a set \<Rightarrow> 'a"
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  assumes "topological_basis B"
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    and choosefrom_basis: "\<And>B'. B' \<noteq> {} \<Longrightarrow> f B' \<in> B'"
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  shows "\<forall>X. open X \<longrightarrow> X \<noteq> {} \<longrightarrow> (\<exists>B' \<in> B. f B' \<in> X)"
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proof (intro allI impI)
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  fix X :: "'a set"
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  assume "open X" and "X \<noteq> {}"
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  from topological_basisE[OF \<open>topological_basis B\<close> \<open>open X\<close> choosefrom_basis[OF \<open>X \<noteq> {}\<close>]]
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  obtain B' where "B' \<in> B" "f X \<in> B'" "B' \<subseteq> X" .
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  then show "\<exists>B'\<in>B. f B' \<in> X"
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    by (auto intro!: choosefrom_basis)
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qed
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end
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lemma topological_basis_prod:
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  assumes A: "topological_basis A"
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    and B: "topological_basis B"
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  shows "topological_basis ((\<lambda>(a, b). a \<times> b) ` (A \<times> B))"
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  unfolding topological_basis_def
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proof (safe, simp_all del: ex_simps add: subset_image_iff ex_simps(1)[symmetric])
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  fix S :: "('a \<times> 'b) set"
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  assume "open S"
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  then show "\<exists>X\<subseteq>A \<times> B. (\<Union>(a,b)\<in>X. a \<times> b) = S"
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  proof (safe intro!: exI[of _ "{x\<in>A \<times> B. fst x \<times> snd x \<subseteq> S}"])
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    fix x y
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    assume "(x, y) \<in> S"
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    from open_prod_elim[OF \<open>open S\<close> this]
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    obtain a b where a: "open a""x \<in> a" and b: "open b" "y \<in> b" and "a \<times> b \<subseteq> S"
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      by (metis mem_Sigma_iff)
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    moreover
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    from A a obtain A0 where "A0 \<in> A" "x \<in> A0" "A0 \<subseteq> a"
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      by (rule topological_basisE)
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    moreover
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    from B b obtain B0 where "B0 \<in> B" "y \<in> B0" "B0 \<subseteq> b"
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      by (rule topological_basisE)
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    ultimately show "(x, y) \<in> (\<Union>(a, b)\<in>{X \<in> A \<times> B. fst X \<times> snd X \<subseteq> S}. a \<times> b)"
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      by (intro UN_I[of "(A0, B0)"]) auto
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  qed auto
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qed (metis A B topological_basis_open open_Times)
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subsection \<open>Countable Basis\<close>
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locale countable_basis =
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  fixes B :: "'a::topological_space set set"
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  assumes is_basis: "topological_basis B"
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    and countable_basis: "countable B"
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begin
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lemma open_countable_basis_ex:
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  assumes "open X"
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  shows "\<exists>B' \<subseteq> B. X = Union B'"
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  using assms countable_basis is_basis
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  unfolding topological_basis_def by blast
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lemma open_countable_basisE:
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  assumes "open X"
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  obtains B' where "B' \<subseteq> B" "X = Union B'"
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  using assms open_countable_basis_ex
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  by (atomize_elim) simp
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lemma countable_dense_exists:
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  "\<exists>D::'a set. countable D \<and> (\<forall>X. open X \<longrightarrow> X \<noteq> {} \<longrightarrow> (\<exists>d \<in> D. d \<in> X))"
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proof -
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  let ?f = "(\<lambda>B'. SOME x. x \<in> B')"
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  have "countable (?f ` B)" using countable_basis by simp
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  with basis_dense[OF is_basis, of ?f] show ?thesis
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    by (intro exI[where x="?f ` B"]) (metis (mono_tags) all_not_in_conv imageI someI)
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qed
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lemma countable_dense_setE:
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  obtains D :: "'a set"
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  where "countable D" "\<And>X. open X \<Longrightarrow> X \<noteq> {} \<Longrightarrow> \<exists>d \<in> D. d \<in> X"
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  using countable_dense_exists by blast
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end
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lemma (in first_countable_topology) first_countable_basisE:
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  obtains A where "countable A" "\<And>a. a \<in> A \<Longrightarrow> x \<in> a" "\<And>a. a \<in> A \<Longrightarrow> open a"
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    "\<And>S. open S \<Longrightarrow> x \<in> S \<Longrightarrow> (\<exists>a\<in>A. a \<subseteq> S)"
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  using first_countable_basis[of x]
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  apply atomize_elim
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  apply (elim exE)
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  apply (rule_tac x="range A" in exI)
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  apply auto
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  done
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lemma (in first_countable_topology) first_countable_basis_Int_stableE:
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  obtains A where "countable A" "\<And>a. a \<in> A \<Longrightarrow> x \<in> a" "\<And>a. a \<in> A \<Longrightarrow> open a"
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    "\<And>S. open S \<Longrightarrow> x \<in> S \<Longrightarrow> (\<exists>a\<in>A. a \<subseteq> S)"
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    "\<And>a b. a \<in> A \<Longrightarrow> b \<in> A \<Longrightarrow> a \<inter> b \<in> A"
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proof atomize_elim
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  obtain A' where A':
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    "countable A'"
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    "\<And>a. a \<in> A' \<Longrightarrow> x \<in> a"
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    "\<And>a. a \<in> A' \<Longrightarrow> open a"
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    "\<And>S. open S \<Longrightarrow> x \<in> S \<Longrightarrow> \<exists>a\<in>A'. a \<subseteq> S"
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    by (rule first_countable_basisE) blast
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  def A \<equiv> "(\<lambda>N. \<Inter>((\<lambda>n. from_nat_into A' n) ` N)) ` (Collect finite::nat set set)"
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  then show "\<exists>A. countable A \<and> (\<forall>a. a \<in> A \<longrightarrow> x \<in> a) \<and> (\<forall>a. a \<in> A \<longrightarrow> open a) \<and>
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        (\<forall>S. open S \<longrightarrow> x \<in> S \<longrightarrow> (\<exists>a\<in>A. a \<subseteq> S)) \<and> (\<forall>a b. a \<in> A \<longrightarrow> b \<in> A \<longrightarrow> a \<inter> b \<in> A)"
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  proof (safe intro!: exI[where x=A])
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    show "countable A"
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      unfolding A_def by (intro countable_image countable_Collect_finite)
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    fix a
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    assume "a \<in> A"
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    then show "x \<in> a" "open a"
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      using A'(4)[OF open_UNIV] by (auto simp: A_def intro: A' from_nat_into)
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  next
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    let ?int = "\<lambda>N. \<Inter>(from_nat_into A' ` N)"
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    fix a b
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    assume "a \<in> A" "b \<in> A"
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    then obtain N M where "a = ?int N" "b = ?int M" "finite (N \<union> M)"
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      by (auto simp: A_def)
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    then show "a \<inter> b \<in> A"
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      by (auto simp: A_def intro!: image_eqI[where x="N \<union> M"])
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  next
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    fix S
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    assume "open S" "x \<in> S"
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    then obtain a where a: "a\<in>A'" "a \<subseteq> S" using A' by blast
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    then show "\<exists>a\<in>A. a \<subseteq> S" using a A'
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      by (intro bexI[where x=a]) (auto simp: A_def intro: image_eqI[where x="{to_nat_on A' a}"])
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  qed
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qed
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lemma (in topological_space) first_countableI:
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  assumes "countable A"
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    and 1: "\<And>a. a \<in> A \<Longrightarrow> x \<in> a" "\<And>a. a \<in> A \<Longrightarrow> open a"
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    and 2: "\<And>S. open S \<Longrightarrow> x \<in> S \<Longrightarrow> \<exists>a\<in>A. a \<subseteq> S"
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  shows "\<exists>A::nat \<Rightarrow> 'a set. (\<forall>i. x \<in> A i \<and> open (A i)) \<and> (\<forall>S. open S \<and> x \<in> S \<longrightarrow> (\<exists>i. A i \<subseteq> S))"
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proof (safe intro!: exI[of _ "from_nat_into A"])
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  fix i
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  have "A \<noteq> {}" using 2[of UNIV] by auto
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  show "x \<in> from_nat_into A i" "open (from_nat_into A i)"
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    using range_from_nat_into_subset[OF \<open>A \<noteq> {}\<close>] 1 by auto
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next
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  fix S
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  assume "open S" "x\<in>S" from 2[OF this]
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  show "\<exists>i. from_nat_into A i \<subseteq> S"
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    using subset_range_from_nat_into[OF \<open>countable A\<close>] by auto
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qed
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instance prod :: (first_countable_topology, first_countable_topology) first_countable_topology
hoelzl@50883
   283
proof
hoelzl@50883
   284
  fix x :: "'a \<times> 'b"
wenzelm@55522
   285
  obtain A where A:
wenzelm@55522
   286
      "countable A"
wenzelm@55522
   287
      "\<And>a. a \<in> A \<Longrightarrow> fst x \<in> a"
wenzelm@55522
   288
      "\<And>a. a \<in> A \<Longrightarrow> open a"
wenzelm@55522
   289
      "\<And>S. open S \<Longrightarrow> fst x \<in> S \<Longrightarrow> \<exists>a\<in>A. a \<subseteq> S"
wenzelm@55522
   290
    by (rule first_countable_basisE[of "fst x"]) blast
wenzelm@55522
   291
  obtain B where B:
wenzelm@55522
   292
      "countable B"
wenzelm@55522
   293
      "\<And>a. a \<in> B \<Longrightarrow> snd x \<in> a"
wenzelm@55522
   294
      "\<And>a. a \<in> B \<Longrightarrow> open a"
wenzelm@55522
   295
      "\<And>S. open S \<Longrightarrow> snd x \<in> S \<Longrightarrow> \<exists>a\<in>B. a \<subseteq> S"
wenzelm@55522
   296
    by (rule first_countable_basisE[of "snd x"]) blast
wenzelm@53282
   297
  show "\<exists>A::nat \<Rightarrow> ('a \<times> 'b) set.
wenzelm@53282
   298
    (\<forall>i. x \<in> A i \<and> open (A i)) \<and> (\<forall>S. open S \<and> x \<in> S \<longrightarrow> (\<exists>i. A i \<subseteq> S))"
hoelzl@51473
   299
  proof (rule first_countableI[of "(\<lambda>(a, b). a \<times> b) ` (A \<times> B)"], safe)
wenzelm@53255
   300
    fix a b
wenzelm@53255
   301
    assume x: "a \<in> A" "b \<in> B"
wenzelm@53640
   302
    with A(2, 3)[of a] B(2, 3)[of b] show "x \<in> a \<times> b" and "open (a \<times> b)"
wenzelm@53640
   303
      unfolding mem_Times_iff
wenzelm@53640
   304
      by (auto intro: open_Times)
hoelzl@50883
   305
  next
wenzelm@53255
   306
    fix S
wenzelm@53255
   307
    assume "open S" "x \<in> S"
wenzelm@55522
   308
    then obtain a' b' where a'b': "open a'" "open b'" "x \<in> a' \<times> b'" "a' \<times> b' \<subseteq> S"
wenzelm@55522
   309
      by (rule open_prod_elim)
wenzelm@55522
   310
    moreover
wenzelm@55522
   311
    from a'b' A(4)[of a'] B(4)[of b']
wenzelm@55522
   312
    obtain a b where "a \<in> A" "a \<subseteq> a'" "b \<in> B" "b \<subseteq> b'"
wenzelm@55522
   313
      by auto
wenzelm@55522
   314
    ultimately
wenzelm@55522
   315
    show "\<exists>a\<in>(\<lambda>(a, b). a \<times> b) ` (A \<times> B). a \<subseteq> S"
hoelzl@50883
   316
      by (auto intro!: bexI[of _ "a \<times> b"] bexI[of _ a] bexI[of _ b])
hoelzl@50883
   317
  qed (simp add: A B)
hoelzl@50883
   318
qed
hoelzl@50883
   319
hoelzl@50881
   320
class second_countable_topology = topological_space +
wenzelm@53282
   321
  assumes ex_countable_subbasis:
wenzelm@53282
   322
    "\<exists>B::'a::topological_space set set. countable B \<and> open = generate_topology B"
hoelzl@51343
   323
begin
hoelzl@51343
   324
hoelzl@51343
   325
lemma ex_countable_basis: "\<exists>B::'a set set. countable B \<and> topological_basis B"
hoelzl@51343
   326
proof -
wenzelm@53255
   327
  from ex_countable_subbasis obtain B where B: "countable B" "open = generate_topology B"
wenzelm@53255
   328
    by blast
hoelzl@51343
   329
  let ?B = "Inter ` {b. finite b \<and> b \<subseteq> B }"
hoelzl@51343
   330
hoelzl@51343
   331
  show ?thesis
hoelzl@51343
   332
  proof (intro exI conjI)
hoelzl@51343
   333
    show "countable ?B"
hoelzl@51343
   334
      by (intro countable_image countable_Collect_finite_subset B)
wenzelm@53255
   335
    {
wenzelm@53255
   336
      fix S
wenzelm@53255
   337
      assume "open S"
hoelzl@51343
   338
      then have "\<exists>B'\<subseteq>{b. finite b \<and> b \<subseteq> B}. (\<Union>b\<in>B'. \<Inter>b) = S"
hoelzl@51343
   339
        unfolding B
hoelzl@51343
   340
      proof induct
wenzelm@53255
   341
        case UNIV
wenzelm@53255
   342
        show ?case by (intro exI[of _ "{{}}"]) simp
hoelzl@51343
   343
      next
hoelzl@51343
   344
        case (Int a b)
hoelzl@51343
   345
        then obtain x y where x: "a = UNION x Inter" "\<And>i. i \<in> x \<Longrightarrow> finite i \<and> i \<subseteq> B"
hoelzl@51343
   346
          and y: "b = UNION y Inter" "\<And>i. i \<in> y \<Longrightarrow> finite i \<and> i \<subseteq> B"
hoelzl@51343
   347
          by blast
hoelzl@51343
   348
        show ?case
hoelzl@51343
   349
          unfolding x y Int_UN_distrib2
hoelzl@51343
   350
          by (intro exI[of _ "{i \<union> j| i j.  i \<in> x \<and> j \<in> y}"]) (auto dest: x(2) y(2))
hoelzl@51343
   351
      next
hoelzl@51343
   352
        case (UN K)
hoelzl@51343
   353
        then have "\<forall>k\<in>K. \<exists>B'\<subseteq>{b. finite b \<and> b \<subseteq> B}. UNION B' Inter = k" by auto
wenzelm@55522
   354
        then obtain k where
wenzelm@55522
   355
            "\<forall>ka\<in>K. k ka \<subseteq> {b. finite b \<and> b \<subseteq> B} \<and> UNION (k ka) Inter = ka"
wenzelm@55522
   356
          unfolding bchoice_iff ..
hoelzl@51343
   357
        then show "\<exists>B'\<subseteq>{b. finite b \<and> b \<subseteq> B}. UNION B' Inter = \<Union>K"
hoelzl@51343
   358
          by (intro exI[of _ "UNION K k"]) auto
hoelzl@51343
   359
      next
wenzelm@53255
   360
        case (Basis S)
wenzelm@53255
   361
        then show ?case
hoelzl@51343
   362
          by (intro exI[of _ "{{S}}"]) auto
hoelzl@51343
   363
      qed
hoelzl@51343
   364
      then have "(\<exists>B'\<subseteq>Inter ` {b. finite b \<and> b \<subseteq> B}. \<Union>B' = S)"
hoelzl@51343
   365
        unfolding subset_image_iff by blast }
hoelzl@51343
   366
    then show "topological_basis ?B"
hoelzl@51343
   367
      unfolding topological_space_class.topological_basis_def
wenzelm@53282
   368
      by (safe intro!: topological_space_class.open_Inter)
hoelzl@51343
   369
         (simp_all add: B generate_topology.Basis subset_eq)
hoelzl@51343
   370
  qed
hoelzl@51343
   371
qed
hoelzl@51343
   372
hoelzl@51343
   373
end
hoelzl@51343
   374
hoelzl@51343
   375
sublocale second_countable_topology <
hoelzl@51343
   376
  countable_basis "SOME B. countable B \<and> topological_basis B"
hoelzl@51343
   377
  using someI_ex[OF ex_countable_basis]
hoelzl@51343
   378
  by unfold_locales safe
immler@50094
   379
hoelzl@50882
   380
instance prod :: (second_countable_topology, second_countable_topology) second_countable_topology
hoelzl@50882
   381
proof
hoelzl@50882
   382
  obtain A :: "'a set set" where "countable A" "topological_basis A"
hoelzl@50882
   383
    using ex_countable_basis by auto
hoelzl@50882
   384
  moreover
hoelzl@50882
   385
  obtain B :: "'b set set" where "countable B" "topological_basis B"
hoelzl@50882
   386
    using ex_countable_basis by auto
hoelzl@51343
   387
  ultimately show "\<exists>B::('a \<times> 'b) set set. countable B \<and> open = generate_topology B"
hoelzl@51343
   388
    by (auto intro!: exI[of _ "(\<lambda>(a, b). a \<times> b) ` (A \<times> B)"] topological_basis_prod
hoelzl@51343
   389
      topological_basis_imp_subbasis)
hoelzl@50882
   390
qed
hoelzl@50882
   391
hoelzl@50883
   392
instance second_countable_topology \<subseteq> first_countable_topology
hoelzl@50883
   393
proof
hoelzl@50883
   394
  fix x :: 'a
hoelzl@50883
   395
  def B \<equiv> "SOME B::'a set set. countable B \<and> topological_basis B"
hoelzl@50883
   396
  then have B: "countable B" "topological_basis B"
hoelzl@50883
   397
    using countable_basis is_basis
hoelzl@50883
   398
    by (auto simp: countable_basis is_basis)
wenzelm@53282
   399
  then show "\<exists>A::nat \<Rightarrow> 'a set.
wenzelm@53282
   400
    (\<forall>i. x \<in> A i \<and> open (A i)) \<and> (\<forall>S. open S \<and> x \<in> S \<longrightarrow> (\<exists>i. A i \<subseteq> S))"
hoelzl@51473
   401
    by (intro first_countableI[of "{b\<in>B. x \<in> b}"])
hoelzl@51473
   402
       (fastforce simp: topological_space_class.topological_basis_def)+
hoelzl@50883
   403
qed
hoelzl@50883
   404
wenzelm@53255
   405
wenzelm@60420
   406
subsection \<open>Polish spaces\<close>
wenzelm@60420
   407
wenzelm@60420
   408
text \<open>Textbooks define Polish spaces as completely metrizable.
wenzelm@60420
   409
  We assume the topology to be complete for a given metric.\<close>
immler@50087
   410
hoelzl@50881
   411
class polish_space = complete_space + second_countable_topology
immler@50087
   412
wenzelm@60420
   413
subsection \<open>General notion of a topology as a value\<close>
himmelma@33175
   414
wenzelm@53255
   415
definition "istopology L \<longleftrightarrow>
wenzelm@60585
   416
  L {} \<and> (\<forall>S T. L S \<longrightarrow> L T \<longrightarrow> L (S \<inter> T)) \<and> (\<forall>K. Ball K L \<longrightarrow> L (\<Union>K))"
wenzelm@53255
   417
wenzelm@49834
   418
typedef 'a topology = "{L::('a set) \<Rightarrow> bool. istopology L}"
himmelma@33175
   419
  morphisms "openin" "topology"
himmelma@33175
   420
  unfolding istopology_def by blast
himmelma@33175
   421
himmelma@33175
   422
lemma istopology_open_in[intro]: "istopology(openin U)"
himmelma@33175
   423
  using openin[of U] by blast
himmelma@33175
   424
himmelma@33175
   425
lemma topology_inverse': "istopology U \<Longrightarrow> openin (topology U) = U"
huffman@44170
   426
  using topology_inverse[unfolded mem_Collect_eq] .
himmelma@33175
   427
himmelma@33175
   428
lemma topology_inverse_iff: "istopology U \<longleftrightarrow> openin (topology U) = U"
himmelma@33175
   429
  using topology_inverse[of U] istopology_open_in[of "topology U"] by auto
himmelma@33175
   430
himmelma@33175
   431
lemma topology_eq: "T1 = T2 \<longleftrightarrow> (\<forall>S. openin T1 S \<longleftrightarrow> openin T2 S)"
wenzelm@53255
   432
proof
wenzelm@53255
   433
  assume "T1 = T2"
wenzelm@53255
   434
  then show "\<forall>S. openin T1 S \<longleftrightarrow> openin T2 S" by simp
wenzelm@53255
   435
next
wenzelm@53255
   436
  assume H: "\<forall>S. openin T1 S \<longleftrightarrow> openin T2 S"
wenzelm@53255
   437
  then have "openin T1 = openin T2" by (simp add: fun_eq_iff)
wenzelm@53255
   438
  then have "topology (openin T1) = topology (openin T2)" by simp
wenzelm@53255
   439
  then show "T1 = T2" unfolding openin_inverse .
himmelma@33175
   440
qed
himmelma@33175
   441
wenzelm@60420
   442
text\<open>Infer the "universe" from union of all sets in the topology.\<close>
himmelma@33175
   443
wenzelm@53640
   444
definition "topspace T = \<Union>{S. openin T S}"
himmelma@33175
   445
wenzelm@60420
   446
subsubsection \<open>Main properties of open sets\<close>
himmelma@33175
   447
himmelma@33175
   448
lemma openin_clauses:
himmelma@33175
   449
  fixes U :: "'a topology"
wenzelm@53282
   450
  shows
wenzelm@53282
   451
    "openin U {}"
wenzelm@53282
   452
    "\<And>S T. openin U S \<Longrightarrow> openin U T \<Longrightarrow> openin U (S\<inter>T)"
wenzelm@53282
   453
    "\<And>K. (\<forall>S \<in> K. openin U S) \<Longrightarrow> openin U (\<Union>K)"
wenzelm@53282
   454
  using openin[of U] unfolding istopology_def mem_Collect_eq by fast+
himmelma@33175
   455
himmelma@33175
   456
lemma openin_subset[intro]: "openin U S \<Longrightarrow> S \<subseteq> topspace U"
himmelma@33175
   457
  unfolding topspace_def by blast
wenzelm@53255
   458
wenzelm@53255
   459
lemma openin_empty[simp]: "openin U {}"
wenzelm@53255
   460
  by (simp add: openin_clauses)
himmelma@33175
   461
himmelma@33175
   462
lemma openin_Int[intro]: "openin U S \<Longrightarrow> openin U T \<Longrightarrow> openin U (S \<inter> T)"
huffman@36362
   463
  using openin_clauses by simp
huffman@36362
   464
wenzelm@60585
   465
lemma openin_Union[intro]: "(\<forall>S \<in>K. openin U S) \<Longrightarrow> openin U (\<Union>K)"
huffman@36362
   466
  using openin_clauses by simp
himmelma@33175
   467
himmelma@33175
   468
lemma openin_Un[intro]: "openin U S \<Longrightarrow> openin U T \<Longrightarrow> openin U (S \<union> T)"
himmelma@33175
   469
  using openin_Union[of "{S,T}" U] by auto
himmelma@33175
   470
wenzelm@53255
   471
lemma openin_topspace[intro, simp]: "openin U (topspace U)"
wenzelm@53255
   472
  by (simp add: openin_Union topspace_def)
himmelma@33175
   473
wenzelm@49711
   474
lemma openin_subopen: "openin U S \<longleftrightarrow> (\<forall>x \<in> S. \<exists>T. openin U T \<and> x \<in> T \<and> T \<subseteq> S)"
wenzelm@49711
   475
  (is "?lhs \<longleftrightarrow> ?rhs")
huffman@36584
   476
proof
wenzelm@49711
   477
  assume ?lhs
wenzelm@49711
   478
  then show ?rhs by auto
huffman@36584
   479
next
huffman@36584
   480
  assume H: ?rhs
huffman@36584
   481
  let ?t = "\<Union>{T. openin U T \<and> T \<subseteq> S}"
huffman@36584
   482
  have "openin U ?t" by (simp add: openin_Union)
huffman@36584
   483
  also have "?t = S" using H by auto
huffman@36584
   484
  finally show "openin U S" .
himmelma@33175
   485
qed
himmelma@33175
   486
wenzelm@49711
   487
wenzelm@60420
   488
subsubsection \<open>Closed sets\<close>
himmelma@33175
   489
himmelma@33175
   490
definition "closedin U S \<longleftrightarrow> S \<subseteq> topspace U \<and> openin U (topspace U - S)"
himmelma@33175
   491
wenzelm@53255
   492
lemma closedin_subset: "closedin U S \<Longrightarrow> S \<subseteq> topspace U"
wenzelm@53255
   493
  by (metis closedin_def)
wenzelm@53255
   494
wenzelm@53255
   495
lemma closedin_empty[simp]: "closedin U {}"
wenzelm@53255
   496
  by (simp add: closedin_def)
wenzelm@53255
   497
wenzelm@53255
   498
lemma closedin_topspace[intro, simp]: "closedin U (topspace U)"
wenzelm@53255
   499
  by (simp add: closedin_def)
wenzelm@53255
   500
himmelma@33175
   501
lemma closedin_Un[intro]: "closedin U S \<Longrightarrow> closedin U T \<Longrightarrow> closedin U (S \<union> T)"
himmelma@33175
   502
  by (auto simp add: Diff_Un closedin_def)
himmelma@33175
   503
wenzelm@60585
   504
lemma Diff_Inter[intro]: "A - \<Inter>S = \<Union>{A - s|s. s\<in>S}"
wenzelm@53255
   505
  by auto
wenzelm@53255
   506
wenzelm@53255
   507
lemma closedin_Inter[intro]:
wenzelm@53255
   508
  assumes Ke: "K \<noteq> {}"
wenzelm@53255
   509
    and Kc: "\<forall>S \<in>K. closedin U S"
wenzelm@60585
   510
  shows "closedin U (\<Inter>K)"
wenzelm@53255
   511
  using Ke Kc unfolding closedin_def Diff_Inter by auto
himmelma@33175
   512
himmelma@33175
   513
lemma closedin_Int[intro]: "closedin U S \<Longrightarrow> closedin U T \<Longrightarrow> closedin U (S \<inter> T)"
himmelma@33175
   514
  using closedin_Inter[of "{S,T}" U] by auto
himmelma@33175
   515
himmelma@33175
   516
lemma openin_closedin_eq: "openin U S \<longleftrightarrow> S \<subseteq> topspace U \<and> closedin U (topspace U - S)"
himmelma@33175
   517
  apply (auto simp add: closedin_def Diff_Diff_Int inf_absorb2)
himmelma@33175
   518
  apply (metis openin_subset subset_eq)
himmelma@33175
   519
  done
himmelma@33175
   520
wenzelm@53255
   521
lemma openin_closedin: "S \<subseteq> topspace U \<Longrightarrow> (openin U S \<longleftrightarrow> closedin U (topspace U - S))"
himmelma@33175
   522
  by (simp add: openin_closedin_eq)
himmelma@33175
   523
wenzelm@53255
   524
lemma openin_diff[intro]:
wenzelm@53255
   525
  assumes oS: "openin U S"
wenzelm@53255
   526
    and cT: "closedin U T"
wenzelm@53255
   527
  shows "openin U (S - T)"
wenzelm@53255
   528
proof -
himmelma@33175
   529
  have "S - T = S \<inter> (topspace U - T)" using openin_subset[of U S]  oS cT
himmelma@33175
   530
    by (auto simp add: topspace_def openin_subset)
wenzelm@53282
   531
  then show ?thesis using oS cT
wenzelm@53282
   532
    by (auto simp add: closedin_def)
himmelma@33175
   533
qed
himmelma@33175
   534
wenzelm@53255
   535
lemma closedin_diff[intro]:
wenzelm@53255
   536
  assumes oS: "closedin U S"
wenzelm@53255
   537
    and cT: "openin U T"
wenzelm@53255
   538
  shows "closedin U (S - T)"
wenzelm@53255
   539
proof -
wenzelm@53255
   540
  have "S - T = S \<inter> (topspace U - T)"
wenzelm@53282
   541
    using closedin_subset[of U S] oS cT by (auto simp add: topspace_def)
wenzelm@53255
   542
  then show ?thesis
wenzelm@53255
   543
    using oS cT by (auto simp add: openin_closedin_eq)
wenzelm@53255
   544
qed
wenzelm@53255
   545
himmelma@33175
   546
wenzelm@60420
   547
subsubsection \<open>Subspace topology\<close>
huffman@44170
   548
huffman@44170
   549
definition "subtopology U V = topology (\<lambda>T. \<exists>S. T = S \<inter> V \<and> openin U S)"
huffman@44170
   550
huffman@44170
   551
lemma istopology_subtopology: "istopology (\<lambda>T. \<exists>S. T = S \<inter> V \<and> openin U S)"
huffman@44170
   552
  (is "istopology ?L")
wenzelm@53255
   553
proof -
huffman@44170
   554
  have "?L {}" by blast
wenzelm@53255
   555
  {
wenzelm@53255
   556
    fix A B
wenzelm@53255
   557
    assume A: "?L A" and B: "?L B"
wenzelm@53255
   558
    from A B obtain Sa and Sb where Sa: "openin U Sa" "A = Sa \<inter> V" and Sb: "openin U Sb" "B = Sb \<inter> V"
wenzelm@53255
   559
      by blast
wenzelm@53255
   560
    have "A \<inter> B = (Sa \<inter> Sb) \<inter> V" "openin U (Sa \<inter> Sb)"
wenzelm@53255
   561
      using Sa Sb by blast+
wenzelm@53255
   562
    then have "?L (A \<inter> B)" by blast
wenzelm@53255
   563
  }
himmelma@33175
   564
  moreover
wenzelm@53255
   565
  {
wenzelm@53282
   566
    fix K
wenzelm@53282
   567
    assume K: "K \<subseteq> Collect ?L"
huffman@44170
   568
    have th0: "Collect ?L = (\<lambda>S. S \<inter> V) ` Collect (openin U)"
lp15@55775
   569
      by blast
himmelma@33175
   570
    from K[unfolded th0 subset_image_iff]
wenzelm@53255
   571
    obtain Sk where Sk: "Sk \<subseteq> Collect (openin U)" "K = (\<lambda>S. S \<inter> V) ` Sk"
wenzelm@53255
   572
      by blast
wenzelm@53255
   573
    have "\<Union>K = (\<Union>Sk) \<inter> V"
wenzelm@53255
   574
      using Sk by auto
wenzelm@60585
   575
    moreover have "openin U (\<Union>Sk)"
wenzelm@53255
   576
      using Sk by (auto simp add: subset_eq)
wenzelm@53255
   577
    ultimately have "?L (\<Union>K)" by blast
wenzelm@53255
   578
  }
huffman@44170
   579
  ultimately show ?thesis
huffman@44170
   580
    unfolding subset_eq mem_Collect_eq istopology_def by blast
himmelma@33175
   581
qed
himmelma@33175
   582
wenzelm@53255
   583
lemma openin_subtopology: "openin (subtopology U V) S \<longleftrightarrow> (\<exists>T. openin U T \<and> S = T \<inter> V)"
himmelma@33175
   584
  unfolding subtopology_def topology_inverse'[OF istopology_subtopology]
huffman@44170
   585
  by auto
himmelma@33175
   586
wenzelm@53255
   587
lemma topspace_subtopology: "topspace (subtopology U V) = topspace U \<inter> V"
himmelma@33175
   588
  by (auto simp add: topspace_def openin_subtopology)
himmelma@33175
   589
wenzelm@53255
   590
lemma closedin_subtopology: "closedin (subtopology U V) S \<longleftrightarrow> (\<exists>T. closedin U T \<and> S = T \<inter> V)"
himmelma@33175
   591
  unfolding closedin_def topspace_subtopology
lp15@55775
   592
  by (auto simp add: openin_subtopology)
himmelma@33175
   593
himmelma@33175
   594
lemma openin_subtopology_refl: "openin (subtopology U V) V \<longleftrightarrow> V \<subseteq> topspace U"
himmelma@33175
   595
  unfolding openin_subtopology
lp15@55775
   596
  by auto (metis IntD1 in_mono openin_subset)
wenzelm@49711
   597
wenzelm@49711
   598
lemma subtopology_superset:
wenzelm@49711
   599
  assumes UV: "topspace U \<subseteq> V"
himmelma@33175
   600
  shows "subtopology U V = U"
wenzelm@53255
   601
proof -
wenzelm@53255
   602
  {
wenzelm@53255
   603
    fix S
wenzelm@53255
   604
    {
wenzelm@53255
   605
      fix T
wenzelm@53255
   606
      assume T: "openin U T" "S = T \<inter> V"
wenzelm@53255
   607
      from T openin_subset[OF T(1)] UV have eq: "S = T"
wenzelm@53255
   608
        by blast
wenzelm@53255
   609
      have "openin U S"
wenzelm@53255
   610
        unfolding eq using T by blast
wenzelm@53255
   611
    }
himmelma@33175
   612
    moreover
wenzelm@53255
   613
    {
wenzelm@53255
   614
      assume S: "openin U S"
wenzelm@53255
   615
      then have "\<exists>T. openin U T \<and> S = T \<inter> V"
wenzelm@53255
   616
        using openin_subset[OF S] UV by auto
wenzelm@53255
   617
    }
wenzelm@53255
   618
    ultimately have "(\<exists>T. openin U T \<and> S = T \<inter> V) \<longleftrightarrow> openin U S"
wenzelm@53255
   619
      by blast
wenzelm@53255
   620
  }
wenzelm@53255
   621
  then show ?thesis
wenzelm@53255
   622
    unfolding topology_eq openin_subtopology by blast
himmelma@33175
   623
qed
himmelma@33175
   624
himmelma@33175
   625
lemma subtopology_topspace[simp]: "subtopology U (topspace U) = U"
himmelma@33175
   626
  by (simp add: subtopology_superset)
himmelma@33175
   627
himmelma@33175
   628
lemma subtopology_UNIV[simp]: "subtopology U UNIV = U"
himmelma@33175
   629
  by (simp add: subtopology_superset)
himmelma@33175
   630
wenzelm@53255
   631
wenzelm@60420
   632
subsubsection \<open>The standard Euclidean topology\<close>
himmelma@33175
   633
wenzelm@53255
   634
definition euclidean :: "'a::topological_space topology"
wenzelm@53255
   635
  where "euclidean = topology open"
himmelma@33175
   636
himmelma@33175
   637
lemma open_openin: "open S \<longleftrightarrow> openin euclidean S"
himmelma@33175
   638
  unfolding euclidean_def
himmelma@33175
   639
  apply (rule cong[where x=S and y=S])
himmelma@33175
   640
  apply (rule topology_inverse[symmetric])
himmelma@33175
   641
  apply (auto simp add: istopology_def)
huffman@44170
   642
  done
himmelma@33175
   643
himmelma@33175
   644
lemma topspace_euclidean: "topspace euclidean = UNIV"
himmelma@33175
   645
  apply (simp add: topspace_def)
nipkow@39302
   646
  apply (rule set_eqI)
wenzelm@53255
   647
  apply (auto simp add: open_openin[symmetric])
wenzelm@53255
   648
  done
himmelma@33175
   649
himmelma@33175
   650
lemma topspace_euclidean_subtopology[simp]: "topspace (subtopology euclidean S) = S"
himmelma@33175
   651
  by (simp add: topspace_euclidean topspace_subtopology)
himmelma@33175
   652
himmelma@33175
   653
lemma closed_closedin: "closed S \<longleftrightarrow> closedin euclidean S"
himmelma@33175
   654
  by (simp add: closed_def closedin_def topspace_euclidean open_openin Compl_eq_Diff_UNIV)
himmelma@33175
   655
himmelma@33175
   656
lemma open_subopen: "open S \<longleftrightarrow> (\<forall>x\<in>S. \<exists>T. open T \<and> x \<in> T \<and> T \<subseteq> S)"
himmelma@33175
   657
  by (simp add: open_openin openin_subopen[symmetric])
himmelma@33175
   658
wenzelm@60420
   659
text \<open>Basic "localization" results are handy for connectedness.\<close>
huffman@44210
   660
huffman@44210
   661
lemma openin_open: "openin (subtopology euclidean U) S \<longleftrightarrow> (\<exists>T. open T \<and> (S = U \<inter> T))"
huffman@44210
   662
  by (auto simp add: openin_subtopology open_openin[symmetric])
huffman@44210
   663
huffman@44210
   664
lemma openin_open_Int[intro]: "open S \<Longrightarrow> openin (subtopology euclidean U) (U \<inter> S)"
huffman@44210
   665
  by (auto simp add: openin_open)
huffman@44210
   666
huffman@44210
   667
lemma open_openin_trans[trans]:
wenzelm@53255
   668
  "open S \<Longrightarrow> open T \<Longrightarrow> T \<subseteq> S \<Longrightarrow> openin (subtopology euclidean S) T"
huffman@44210
   669
  by (metis Int_absorb1  openin_open_Int)
huffman@44210
   670
wenzelm@53255
   671
lemma open_subset: "S \<subseteq> T \<Longrightarrow> open S \<Longrightarrow> openin (subtopology euclidean T) S"
huffman@44210
   672
  by (auto simp add: openin_open)
huffman@44210
   673
huffman@44210
   674
lemma closedin_closed: "closedin (subtopology euclidean U) S \<longleftrightarrow> (\<exists>T. closed T \<and> S = U \<inter> T)"
huffman@44210
   675
  by (simp add: closedin_subtopology closed_closedin Int_ac)
huffman@44210
   676
wenzelm@53291
   677
lemma closedin_closed_Int: "closed S \<Longrightarrow> closedin (subtopology euclidean U) (U \<inter> S)"
huffman@44210
   678
  by (metis closedin_closed)
huffman@44210
   679
wenzelm@53282
   680
lemma closed_closedin_trans:
wenzelm@53282
   681
  "closed S \<Longrightarrow> closed T \<Longrightarrow> T \<subseteq> S \<Longrightarrow> closedin (subtopology euclidean S) T"
lp15@55775
   682
  by (metis closedin_closed inf.absorb2)
huffman@44210
   683
huffman@44210
   684
lemma closed_subset: "S \<subseteq> T \<Longrightarrow> closed S \<Longrightarrow> closedin (subtopology euclidean T) S"
huffman@44210
   685
  by (auto simp add: closedin_closed)
huffman@44210
   686
huffman@44210
   687
lemma openin_euclidean_subtopology_iff:
huffman@44210
   688
  fixes S U :: "'a::metric_space set"
wenzelm@53255
   689
  shows "openin (subtopology euclidean U) S \<longleftrightarrow>
wenzelm@53255
   690
    S \<subseteq> U \<and> (\<forall>x\<in>S. \<exists>e>0. \<forall>x'\<in>U. dist x' x < e \<longrightarrow> x'\<in> S)"
wenzelm@53255
   691
  (is "?lhs \<longleftrightarrow> ?rhs")
huffman@44210
   692
proof
wenzelm@53255
   693
  assume ?lhs
wenzelm@53282
   694
  then show ?rhs
wenzelm@53282
   695
    unfolding openin_open open_dist by blast
huffman@44210
   696
next
huffman@44210
   697
  def T \<equiv> "{x. \<exists>a\<in>S. \<exists>d>0. (\<forall>y\<in>U. dist y a < d \<longrightarrow> y \<in> S) \<and> dist x a < d}"
huffman@44210
   698
  have 1: "\<forall>x\<in>T. \<exists>e>0. \<forall>y. dist y x < e \<longrightarrow> y \<in> T"
huffman@44210
   699
    unfolding T_def
huffman@44210
   700
    apply clarsimp
huffman@44210
   701
    apply (rule_tac x="d - dist x a" in exI)
huffman@44210
   702
    apply (clarsimp simp add: less_diff_eq)
lp15@55775
   703
    by (metis dist_commute dist_triangle_lt)
wenzelm@53282
   704
  assume ?rhs then have 2: "S = U \<inter> T"
lp15@60141
   705
    unfolding T_def
lp15@55775
   706
    by auto (metis dist_self)
huffman@44210
   707
  from 1 2 show ?lhs
huffman@44210
   708
    unfolding openin_open open_dist by fast
huffman@44210
   709
qed
lp15@61609
   710
lp15@61306
   711
lemma connected_open_in:
lp15@61306
   712
      "connected s \<longleftrightarrow>
lp15@61306
   713
       ~(\<exists>e1 e2. openin (subtopology euclidean s) e1 \<and>
lp15@61306
   714
                 openin (subtopology euclidean s) e2 \<and>
lp15@61306
   715
                 s \<subseteq> e1 \<union> e2 \<and> e1 \<inter> e2 = {} \<and> e1 \<noteq> {} \<and> e2 \<noteq> {})"
lp15@61306
   716
  apply (simp add: connected_def openin_open, safe)
lp15@61609
   717
  apply (simp_all, blast+)  --\<open>slow\<close>
lp15@61306
   718
  done
lp15@61306
   719
lp15@61306
   720
lemma connected_open_in_eq:
lp15@61306
   721
      "connected s \<longleftrightarrow>
lp15@61306
   722
       ~(\<exists>e1 e2. openin (subtopology euclidean s) e1 \<and>
lp15@61306
   723
                 openin (subtopology euclidean s) e2 \<and>
lp15@61306
   724
                 e1 \<union> e2 = s \<and> e1 \<inter> e2 = {} \<and>
lp15@61306
   725
                 e1 \<noteq> {} \<and> e2 \<noteq> {})"
lp15@61306
   726
  apply (simp add: connected_open_in, safe)
lp15@61306
   727
  apply blast
lp15@61306
   728
  by (metis Int_lower1 Un_subset_iff openin_open subset_antisym)
lp15@61306
   729
lp15@61306
   730
lemma connected_closed_in:
lp15@61306
   731
      "connected s \<longleftrightarrow>
lp15@61306
   732
       ~(\<exists>e1 e2.
lp15@61306
   733
             closedin (subtopology euclidean s) e1 \<and>
lp15@61306
   734
             closedin (subtopology euclidean s) e2 \<and>
lp15@61306
   735
             s \<subseteq> e1 \<union> e2 \<and> e1 \<inter> e2 = {} \<and>
lp15@61306
   736
             e1 \<noteq> {} \<and> e2 \<noteq> {})"
lp15@61306
   737
proof -
lp15@61306
   738
  { fix A B x x'
lp15@61306
   739
    assume s_sub: "s \<subseteq> A \<union> B"
lp15@61306
   740
       and disj: "A \<inter> B \<inter> s = {}"
lp15@61306
   741
       and x: "x \<in> s" "x \<in> B" and x': "x' \<in> s" "x' \<in> A"
lp15@61306
   742
       and cl: "closed A" "closed B"
lp15@61306
   743
    assume "\<forall>e1. (\<forall>T. closed T \<longrightarrow> e1 \<noteq> s \<inter> T) \<or> (\<forall>e2. e1 \<inter> e2 = {} \<longrightarrow> s \<subseteq> e1 \<union> e2 \<longrightarrow> (\<forall>T. closed T \<longrightarrow> e2 \<noteq> s \<inter> T) \<or> e1 = {} \<or> e2 = {})"
lp15@61306
   744
    then have "\<And>C D. s \<inter> C = {} \<or> s \<inter> D = {} \<or> s \<inter> (C \<inter> (s \<inter> D)) \<noteq> {} \<or> \<not> s \<subseteq> s \<inter> (C \<union> D) \<or> \<not> closed C \<or> \<not> closed D"
lp15@61306
   745
      by (metis (no_types) Int_Un_distrib Int_assoc)
lp15@61306
   746
    moreover have "s \<inter> (A \<inter> B) = {}" "s \<inter> (A \<union> B) = s" "s \<inter> B \<noteq> {}"
lp15@61306
   747
      using disj s_sub x by blast+
lp15@61306
   748
    ultimately have "s \<inter> A = {}"
lp15@61306
   749
      using cl by (metis inf.left_commute inf_bot_right order_refl)
lp15@61306
   750
    then have False
lp15@61306
   751
      using x' by blast
lp15@61306
   752
  } note * = this
lp15@61306
   753
  show ?thesis
lp15@61306
   754
    apply (simp add: connected_closed closedin_closed)
lp15@61306
   755
    apply (safe; simp)
lp15@61306
   756
    apply blast
lp15@61306
   757
    apply (blast intro: *)
lp15@61306
   758
    done
lp15@61306
   759
qed
lp15@61306
   760
lp15@61306
   761
lemma connected_closed_in_eq:
lp15@61306
   762
      "connected s \<longleftrightarrow>
lp15@61306
   763
           ~(\<exists>e1 e2.
lp15@61306
   764
                 closedin (subtopology euclidean s) e1 \<and>
lp15@61306
   765
                 closedin (subtopology euclidean s) e2 \<and>
lp15@61306
   766
                 e1 \<union> e2 = s \<and> e1 \<inter> e2 = {} \<and>
lp15@61306
   767
                 e1 \<noteq> {} \<and> e2 \<noteq> {})"
lp15@61306
   768
  apply (simp add: connected_closed_in, safe)
lp15@61306
   769
  apply blast
lp15@61306
   770
  by (metis Int_lower1 Un_subset_iff closedin_closed subset_antisym)
lp15@61609
   771
wenzelm@60420
   772
text \<open>These "transitivity" results are handy too\<close>
huffman@44210
   773
wenzelm@53255
   774
lemma openin_trans[trans]:
wenzelm@53255
   775
  "openin (subtopology euclidean T) S \<Longrightarrow> openin (subtopology euclidean U) T \<Longrightarrow>
wenzelm@53255
   776
    openin (subtopology euclidean U) S"
huffman@44210
   777
  unfolding open_openin openin_open by blast
huffman@44210
   778
huffman@44210
   779
lemma openin_open_trans: "openin (subtopology euclidean T) S \<Longrightarrow> open T \<Longrightarrow> open S"
huffman@44210
   780
  by (auto simp add: openin_open intro: openin_trans)
huffman@44210
   781
huffman@44210
   782
lemma closedin_trans[trans]:
wenzelm@53255
   783
  "closedin (subtopology euclidean T) S \<Longrightarrow> closedin (subtopology euclidean U) T \<Longrightarrow>
wenzelm@53255
   784
    closedin (subtopology euclidean U) S"
huffman@44210
   785
  by (auto simp add: closedin_closed closed_closedin closed_Inter Int_assoc)
huffman@44210
   786
huffman@44210
   787
lemma closedin_closed_trans: "closedin (subtopology euclidean T) S \<Longrightarrow> closed T \<Longrightarrow> closed S"
huffman@44210
   788
  by (auto simp add: closedin_closed intro: closedin_trans)
huffman@44210
   789
paulson@61518
   790
lemma openin_subtopology_inter_subset:
paulson@61518
   791
   "openin (subtopology euclidean u) (u \<inter> s) \<and> v \<subseteq> u \<Longrightarrow> openin (subtopology euclidean v) (v \<inter> s)"
paulson@61518
   792
  by (auto simp: openin_subtopology)
paulson@61518
   793
paulson@61518
   794
lemma openin_open_eq: "open s \<Longrightarrow> (openin (subtopology euclidean s) t \<longleftrightarrow> open t \<and> t \<subseteq> s)"
paulson@61518
   795
  using open_subset openin_open_trans openin_subset by fastforce
paulson@61518
   796
huffman@44210
   797
wenzelm@60420
   798
subsection \<open>Open and closed balls\<close>
himmelma@33175
   799
wenzelm@53255
   800
definition ball :: "'a::metric_space \<Rightarrow> real \<Rightarrow> 'a set"
wenzelm@53255
   801
  where "ball x e = {y. dist x y < e}"
wenzelm@53255
   802
wenzelm@53255
   803
definition cball :: "'a::metric_space \<Rightarrow> real \<Rightarrow> 'a set"
wenzelm@53255
   804
  where "cball x e = {y. dist x y \<le> e}"
himmelma@33175
   805
huffman@45776
   806
lemma mem_ball [simp]: "y \<in> ball x e \<longleftrightarrow> dist x y < e"
huffman@45776
   807
  by (simp add: ball_def)
huffman@45776
   808
huffman@45776
   809
lemma mem_cball [simp]: "y \<in> cball x e \<longleftrightarrow> dist x y \<le> e"
huffman@45776
   810
  by (simp add: cball_def)
huffman@45776
   811
paulson@61518
   812
lemma ball_trivial [simp]: "ball x 0 = {}"
paulson@61518
   813
  by (simp add: ball_def)
paulson@61518
   814
paulson@61518
   815
lemma cball_trivial [simp]: "cball x 0 = {x}"
paulson@61518
   816
  by (simp add: cball_def)
paulson@61518
   817
paulson@61518
   818
lemma mem_ball_0 [simp]:
himmelma@33175
   819
  fixes x :: "'a::real_normed_vector"
himmelma@33175
   820
  shows "x \<in> ball 0 e \<longleftrightarrow> norm x < e"
himmelma@33175
   821
  by (simp add: dist_norm)
himmelma@33175
   822
paulson@61518
   823
lemma mem_cball_0 [simp]:
himmelma@33175
   824
  fixes x :: "'a::real_normed_vector"
himmelma@33175
   825
  shows "x \<in> cball 0 e \<longleftrightarrow> norm x \<le> e"
himmelma@33175
   826
  by (simp add: dist_norm)
himmelma@33175
   827
paulson@61518
   828
lemma centre_in_ball [simp]: "x \<in> ball x e \<longleftrightarrow> 0 < e"
huffman@45776
   829
  by simp
huffman@45776
   830
paulson@61518
   831
lemma centre_in_cball [simp]: "x \<in> cball x e \<longleftrightarrow> 0 \<le> e"
huffman@45776
   832
  by simp
huffman@45776
   833
paulson@61518
   834
lemma ball_subset_cball [simp,intro]: "ball x e \<subseteq> cball x e"
wenzelm@53255
   835
  by (simp add: subset_eq)
wenzelm@53255
   836
wenzelm@53282
   837
lemma subset_ball[intro]: "d \<le> e \<Longrightarrow> ball x d \<subseteq> ball x e"
wenzelm@53255
   838
  by (simp add: subset_eq)
wenzelm@53255
   839
wenzelm@53282
   840
lemma subset_cball[intro]: "d \<le> e \<Longrightarrow> cball x d \<subseteq> cball x e"
wenzelm@53255
   841
  by (simp add: subset_eq)
wenzelm@53255
   842
himmelma@33175
   843
lemma ball_max_Un: "ball a (max r s) = ball a r \<union> ball a s"
nipkow@39302
   844
  by (simp add: set_eq_iff) arith
himmelma@33175
   845
himmelma@33175
   846
lemma ball_min_Int: "ball a (min r s) = ball a r \<inter> ball a s"
nipkow@39302
   847
  by (simp add: set_eq_iff)
himmelma@33175
   848
lp15@61426
   849
lemma cball_diff_eq_sphere: "cball a r - ball a r =  {x. dist x a = r}"
lp15@61426
   850
  by (auto simp: cball_def ball_def dist_commute)
lp15@61426
   851
wenzelm@53255
   852
lemma diff_less_iff:
wenzelm@53255
   853
  "(a::real) - b > 0 \<longleftrightarrow> a > b"
himmelma@33175
   854
  "(a::real) - b < 0 \<longleftrightarrow> a < b"
wenzelm@53255
   855
  "a - b < c \<longleftrightarrow> a < c + b" "a - b > c \<longleftrightarrow> a > c + b"
wenzelm@53255
   856
  by arith+
wenzelm@53255
   857
wenzelm@53255
   858
lemma diff_le_iff:
wenzelm@53255
   859
  "(a::real) - b \<ge> 0 \<longleftrightarrow> a \<ge> b"
wenzelm@53255
   860
  "(a::real) - b \<le> 0 \<longleftrightarrow> a \<le> b"
wenzelm@53255
   861
  "a - b \<le> c \<longleftrightarrow> a \<le> c + b"
wenzelm@53255
   862
  "a - b \<ge> c \<longleftrightarrow> a \<ge> c + b"
wenzelm@53255
   863
  by arith+
himmelma@33175
   864
huffman@54070
   865
lemma open_ball [intro, simp]: "open (ball x e)"
huffman@54070
   866
proof -
huffman@54070
   867
  have "open (dist x -` {..<e})"
hoelzl@56371
   868
    by (intro open_vimage open_lessThan continuous_intros)
huffman@54070
   869
  also have "dist x -` {..<e} = ball x e"
huffman@54070
   870
    by auto
huffman@54070
   871
  finally show ?thesis .
huffman@54070
   872
qed
himmelma@33175
   873
himmelma@33175
   874
lemma open_contains_ball: "open S \<longleftrightarrow> (\<forall>x\<in>S. \<exists>e>0. ball x e \<subseteq> S)"
himmelma@33175
   875
  unfolding open_dist subset_eq mem_ball Ball_def dist_commute ..
himmelma@33175
   876
hoelzl@33714
   877
lemma openE[elim?]:
wenzelm@53282
   878
  assumes "open S" "x\<in>S"
hoelzl@33714
   879
  obtains e where "e>0" "ball x e \<subseteq> S"
hoelzl@33714
   880
  using assms unfolding open_contains_ball by auto
hoelzl@33714
   881
himmelma@33175
   882
lemma open_contains_ball_eq: "open S \<Longrightarrow> \<forall>x. x\<in>S \<longleftrightarrow> (\<exists>e>0. ball x e \<subseteq> S)"
himmelma@33175
   883
  by (metis open_contains_ball subset_eq centre_in_ball)
himmelma@33175
   884
himmelma@33175
   885
lemma ball_eq_empty[simp]: "ball x e = {} \<longleftrightarrow> e \<le> 0"
nipkow@39302
   886
  unfolding mem_ball set_eq_iff
himmelma@33175
   887
  apply (simp add: not_less)
wenzelm@52624
   888
  apply (metis zero_le_dist order_trans dist_self)
wenzelm@52624
   889
  done
himmelma@33175
   890
lp15@61694
   891
lemma ball_empty: "e \<le> 0 \<Longrightarrow> ball x e = {}" by simp
himmelma@33175
   892
hoelzl@50526
   893
lemma euclidean_dist_l2:
hoelzl@50526
   894
  fixes x y :: "'a :: euclidean_space"
hoelzl@50526
   895
  shows "dist x y = setL2 (\<lambda>i. dist (x \<bullet> i) (y \<bullet> i)) Basis"
hoelzl@50526
   896
  unfolding dist_norm norm_eq_sqrt_inner setL2_def
hoelzl@50526
   897
  by (subst euclidean_inner) (simp add: power2_eq_square inner_diff_left)
hoelzl@50526
   898
eberlm@61531
   899
lemma eventually_nhds_ball: "d > 0 \<Longrightarrow> eventually (\<lambda>x. x \<in> ball z d) (nhds z)"
eberlm@61531
   900
  by (rule eventually_nhds_in_open) simp_all
eberlm@61531
   901
eberlm@61531
   902
lemma eventually_at_ball: "d > 0 \<Longrightarrow> eventually (\<lambda>t. t \<in> ball z d \<and> t \<in> A) (at z within A)"
eberlm@61531
   903
  unfolding eventually_at by (intro exI[of _ d]) (simp_all add: dist_commute)
eberlm@61531
   904
eberlm@61531
   905
lemma eventually_at_ball': "d > 0 \<Longrightarrow> eventually (\<lambda>t. t \<in> ball z d \<and> t \<noteq> z \<and> t \<in> A) (at z within A)"
eberlm@61531
   906
  unfolding eventually_at by (intro exI[of _ d]) (simp_all add: dist_commute)
eberlm@61531
   907
immler@56189
   908
wenzelm@60420
   909
subsection \<open>Boxes\<close>
immler@56189
   910
hoelzl@57447
   911
abbreviation One :: "'a::euclidean_space"
hoelzl@57447
   912
  where "One \<equiv> \<Sum>Basis"
hoelzl@57447
   913
immler@54775
   914
definition (in euclidean_space) eucl_less (infix "<e" 50)
immler@54775
   915
  where "eucl_less a b \<longleftrightarrow> (\<forall>i\<in>Basis. a \<bullet> i < b \<bullet> i)"
immler@54775
   916
immler@54775
   917
definition box_eucl_less: "box a b = {x. a <e x \<and> x <e b}"
immler@56188
   918
definition "cbox a b = {x. \<forall>i\<in>Basis. a \<bullet> i \<le> x \<bullet> i \<and> x \<bullet> i \<le> b \<bullet> i}"
immler@54775
   919
immler@54775
   920
lemma box_def: "box a b = {x. \<forall>i\<in>Basis. a \<bullet> i < x \<bullet> i \<and> x \<bullet> i < b \<bullet> i}"
immler@54775
   921
  and in_box_eucl_less: "x \<in> box a b \<longleftrightarrow> a <e x \<and> x <e b"
immler@56188
   922
  and mem_box: "x \<in> box a b \<longleftrightarrow> (\<forall>i\<in>Basis. a \<bullet> i < x \<bullet> i \<and> x \<bullet> i < b \<bullet> i)"
immler@56188
   923
    "x \<in> cbox a b \<longleftrightarrow> (\<forall>i\<in>Basis. a \<bullet> i \<le> x \<bullet> i \<and> x \<bullet> i \<le> b \<bullet> i)"
immler@56188
   924
  by (auto simp: box_eucl_less eucl_less_def cbox_def)
immler@56188
   925
lp15@60615
   926
lemma cbox_Pair_eq: "cbox (a, c) (b, d) = cbox a b \<times> cbox c d"
lp15@60615
   927
  by (force simp: cbox_def Basis_prod_def)
lp15@60615
   928
lp15@60615
   929
lemma cbox_Pair_iff [iff]: "(x, y) \<in> cbox (a, c) (b, d) \<longleftrightarrow> x \<in> cbox a b \<and> y \<in> cbox c d"
lp15@60615
   930
  by (force simp: cbox_Pair_eq)
lp15@60615
   931
lp15@60615
   932
lemma cbox_Pair_eq_0: "cbox (a, c) (b, d) = {} \<longleftrightarrow> cbox a b = {} \<or> cbox c d = {}"
lp15@60615
   933
  by (force simp: cbox_Pair_eq)
lp15@60615
   934
lp15@60615
   935
lemma swap_cbox_Pair [simp]: "prod.swap ` cbox (c, a) (d, b) = cbox (a,c) (b,d)"
lp15@60615
   936
  by auto
lp15@60615
   937
immler@56188
   938
lemma mem_box_real[simp]:
immler@56188
   939
  "(x::real) \<in> box a b \<longleftrightarrow> a < x \<and> x < b"
immler@56188
   940
  "(x::real) \<in> cbox a b \<longleftrightarrow> a \<le> x \<and> x \<le> b"
immler@56188
   941
  by (auto simp: mem_box)
immler@56188
   942
immler@56188
   943
lemma box_real[simp]:
immler@56188
   944
  fixes a b:: real
immler@56188
   945
  shows "box a b = {a <..< b}" "cbox a b = {a .. b}"
immler@56188
   946
  by auto
hoelzl@50526
   947
hoelzl@57447
   948
lemma box_Int_box:
hoelzl@57447
   949
  fixes a :: "'a::euclidean_space"
hoelzl@57447
   950
  shows "box a b \<inter> box c d =
hoelzl@57447
   951
    box (\<Sum>i\<in>Basis. max (a\<bullet>i) (c\<bullet>i) *\<^sub>R i) (\<Sum>i\<in>Basis. min (b\<bullet>i) (d\<bullet>i) *\<^sub>R i)"
hoelzl@57447
   952
  unfolding set_eq_iff and Int_iff and mem_box by auto
hoelzl@57447
   953
immler@50087
   954
lemma rational_boxes:
wenzelm@61076
   955
  fixes x :: "'a::euclidean_space"
wenzelm@53291
   956
  assumes "e > 0"
hoelzl@50526
   957
  shows "\<exists>a b. (\<forall>i\<in>Basis. a \<bullet> i \<in> \<rat> \<and> b \<bullet> i \<in> \<rat> ) \<and> x \<in> box a b \<and> box a b \<subseteq> ball x e"
immler@50087
   958
proof -
immler@50087
   959
  def e' \<equiv> "e / (2 * sqrt (real (DIM ('a))))"
wenzelm@53291
   960
  then have e: "e' > 0"
nipkow@56541
   961
    using assms by (auto simp: DIM_positive)
hoelzl@50526
   962
  have "\<forall>i. \<exists>y. y \<in> \<rat> \<and> y < x \<bullet> i \<and> x \<bullet> i - y < e'" (is "\<forall>i. ?th i")
immler@50087
   963
  proof
wenzelm@53255
   964
    fix i
wenzelm@53255
   965
    from Rats_dense_in_real[of "x \<bullet> i - e'" "x \<bullet> i"] e
wenzelm@53255
   966
    show "?th i" by auto
immler@50087
   967
  qed
wenzelm@55522
   968
  from choice[OF this] obtain a where
wenzelm@55522
   969
    a: "\<forall>xa. a xa \<in> \<rat> \<and> a xa < x \<bullet> xa \<and> x \<bullet> xa - a xa < e'" ..
hoelzl@50526
   970
  have "\<forall>i. \<exists>y. y \<in> \<rat> \<and> x \<bullet> i < y \<and> y - x \<bullet> i < e'" (is "\<forall>i. ?th i")
immler@50087
   971
  proof
wenzelm@53255
   972
    fix i
wenzelm@53255
   973
    from Rats_dense_in_real[of "x \<bullet> i" "x \<bullet> i + e'"] e
wenzelm@53255
   974
    show "?th i" by auto
immler@50087
   975
  qed
wenzelm@55522
   976
  from choice[OF this] obtain b where
wenzelm@55522
   977
    b: "\<forall>xa. b xa \<in> \<rat> \<and> x \<bullet> xa < b xa \<and> b xa - x \<bullet> xa < e'" ..
hoelzl@50526
   978
  let ?a = "\<Sum>i\<in>Basis. a i *\<^sub>R i" and ?b = "\<Sum>i\<in>Basis. b i *\<^sub>R i"
hoelzl@50526
   979
  show ?thesis
hoelzl@50526
   980
  proof (rule exI[of _ ?a], rule exI[of _ ?b], safe)
wenzelm@53255
   981
    fix y :: 'a
wenzelm@53255
   982
    assume *: "y \<in> box ?a ?b"
wenzelm@53015
   983
    have "dist x y = sqrt (\<Sum>i\<in>Basis. (dist (x \<bullet> i) (y \<bullet> i))\<^sup>2)"
immler@50087
   984
      unfolding setL2_def[symmetric] by (rule euclidean_dist_l2)
hoelzl@50526
   985
    also have "\<dots> < sqrt (\<Sum>(i::'a)\<in>Basis. e^2 / real (DIM('a)))"
immler@50087
   986
    proof (rule real_sqrt_less_mono, rule setsum_strict_mono)
wenzelm@53255
   987
      fix i :: "'a"
wenzelm@53255
   988
      assume i: "i \<in> Basis"
wenzelm@53255
   989
      have "a i < y\<bullet>i \<and> y\<bullet>i < b i"
wenzelm@53255
   990
        using * i by (auto simp: box_def)
wenzelm@53255
   991
      moreover have "a i < x\<bullet>i" "x\<bullet>i - a i < e'"
wenzelm@53255
   992
        using a by auto
wenzelm@53255
   993
      moreover have "x\<bullet>i < b i" "b i - x\<bullet>i < e'"
wenzelm@53255
   994
        using b by auto
wenzelm@53255
   995
      ultimately have "\<bar>x\<bullet>i - y\<bullet>i\<bar> < 2 * e'"
wenzelm@53255
   996
        by auto
hoelzl@50526
   997
      then have "dist (x \<bullet> i) (y \<bullet> i) < e/sqrt (real (DIM('a)))"
immler@50087
   998
        unfolding e'_def by (auto simp: dist_real_def)
wenzelm@53015
   999
      then have "(dist (x \<bullet> i) (y \<bullet> i))\<^sup>2 < (e/sqrt (real (DIM('a))))\<^sup>2"
immler@50087
  1000
        by (rule power_strict_mono) auto
wenzelm@53015
  1001
      then show "(dist (x \<bullet> i) (y \<bullet> i))\<^sup>2 < e\<^sup>2 / real DIM('a)"
immler@50087
  1002
        by (simp add: power_divide)
immler@50087
  1003
    qed auto
wenzelm@53255
  1004
    also have "\<dots> = e"
lp15@61609
  1005
      using \<open>0 < e\<close> by simp
wenzelm@53255
  1006
    finally show "y \<in> ball x e"
wenzelm@53255
  1007
      by (auto simp: ball_def)
hoelzl@50526
  1008
  qed (insert a b, auto simp: box_def)
hoelzl@50526
  1009
qed
immler@51103
  1010
hoelzl@50526
  1011
lemma open_UNION_box:
wenzelm@61076
  1012
  fixes M :: "'a::euclidean_space set"
wenzelm@53282
  1013
  assumes "open M"
hoelzl@50526
  1014
  defines "a' \<equiv> \<lambda>f :: 'a \<Rightarrow> real \<times> real. (\<Sum>(i::'a)\<in>Basis. fst (f i) *\<^sub>R i)"
hoelzl@50526
  1015
  defines "b' \<equiv> \<lambda>f :: 'a \<Rightarrow> real \<times> real. (\<Sum>(i::'a)\<in>Basis. snd (f i) *\<^sub>R i)"
wenzelm@53015
  1016
  defines "I \<equiv> {f\<in>Basis \<rightarrow>\<^sub>E \<rat> \<times> \<rat>. box (a' f) (b' f) \<subseteq> M}"
hoelzl@50526
  1017
  shows "M = (\<Union>f\<in>I. box (a' f) (b' f))"
wenzelm@52624
  1018
proof -
wenzelm@60462
  1019
  have "x \<in> (\<Union>f\<in>I. box (a' f) (b' f))" if "x \<in> M" for x
wenzelm@60462
  1020
  proof -
wenzelm@52624
  1021
    obtain e where e: "e > 0" "ball x e \<subseteq> M"
wenzelm@60420
  1022
      using openE[OF \<open>open M\<close> \<open>x \<in> M\<close>] by auto
wenzelm@53282
  1023
    moreover obtain a b where ab:
wenzelm@53282
  1024
      "x \<in> box a b"
wenzelm@53282
  1025
      "\<forall>i \<in> Basis. a \<bullet> i \<in> \<rat>"
wenzelm@53282
  1026
      "\<forall>i\<in>Basis. b \<bullet> i \<in> \<rat>"
wenzelm@53282
  1027
      "box a b \<subseteq> ball x e"
wenzelm@52624
  1028
      using rational_boxes[OF e(1)] by metis
wenzelm@60462
  1029
    ultimately show ?thesis
wenzelm@52624
  1030
       by (intro UN_I[of "\<lambda>i\<in>Basis. (a \<bullet> i, b \<bullet> i)"])
wenzelm@52624
  1031
          (auto simp: euclidean_representation I_def a'_def b'_def)
wenzelm@60462
  1032
  qed
wenzelm@52624
  1033
  then show ?thesis by (auto simp: I_def)
wenzelm@52624
  1034
qed
wenzelm@52624
  1035
immler@56189
  1036
lemma box_eq_empty:
immler@56189
  1037
  fixes a :: "'a::euclidean_space"
immler@56189
  1038
  shows "(box a b = {} \<longleftrightarrow> (\<exists>i\<in>Basis. b\<bullet>i \<le> a\<bullet>i))" (is ?th1)
immler@56189
  1039
    and "(cbox a b = {} \<longleftrightarrow> (\<exists>i\<in>Basis. b\<bullet>i < a\<bullet>i))" (is ?th2)
immler@56189
  1040
proof -
immler@56189
  1041
  {
immler@56189
  1042
    fix i x
immler@56189
  1043
    assume i: "i\<in>Basis" and as:"b\<bullet>i \<le> a\<bullet>i" and x:"x\<in>box a b"
immler@56189
  1044
    then have "a \<bullet> i < x \<bullet> i \<and> x \<bullet> i < b \<bullet> i"
immler@56189
  1045
      unfolding mem_box by (auto simp: box_def)
immler@56189
  1046
    then have "a\<bullet>i < b\<bullet>i" by auto
immler@56189
  1047
    then have False using as by auto
immler@56189
  1048
  }
immler@56189
  1049
  moreover
immler@56189
  1050
  {
immler@56189
  1051
    assume as: "\<forall>i\<in>Basis. \<not> (b\<bullet>i \<le> a\<bullet>i)"
immler@56189
  1052
    let ?x = "(1/2) *\<^sub>R (a + b)"
immler@56189
  1053
    {
immler@56189
  1054
      fix i :: 'a
immler@56189
  1055
      assume i: "i \<in> Basis"
immler@56189
  1056
      have "a\<bullet>i < b\<bullet>i"
immler@56189
  1057
        using as[THEN bspec[where x=i]] i by auto
immler@56189
  1058
      then have "a\<bullet>i < ((1/2) *\<^sub>R (a+b)) \<bullet> i" "((1/2) *\<^sub>R (a+b)) \<bullet> i < b\<bullet>i"
immler@56189
  1059
        by (auto simp: inner_add_left)
immler@56189
  1060
    }
immler@56189
  1061
    then have "box a b \<noteq> {}"
immler@56189
  1062
      using mem_box(1)[of "?x" a b] by auto
immler@56189
  1063
  }
immler@56189
  1064
  ultimately show ?th1 by blast
immler@56189
  1065
immler@56189
  1066
  {
immler@56189
  1067
    fix i x
immler@56189
  1068
    assume i: "i \<in> Basis" and as:"b\<bullet>i < a\<bullet>i" and x:"x\<in>cbox a b"
immler@56189
  1069
    then have "a \<bullet> i \<le> x \<bullet> i \<and> x \<bullet> i \<le> b \<bullet> i"
immler@56189
  1070
      unfolding mem_box by auto
immler@56189
  1071
    then have "a\<bullet>i \<le> b\<bullet>i" by auto
immler@56189
  1072
    then have False using as by auto
immler@56189
  1073
  }
immler@56189
  1074
  moreover
immler@56189
  1075
  {
immler@56189
  1076
    assume as:"\<forall>i\<in>Basis. \<not> (b\<bullet>i < a\<bullet>i)"
immler@56189
  1077
    let ?x = "(1/2) *\<^sub>R (a + b)"
immler@56189
  1078
    {
immler@56189
  1079
      fix i :: 'a
immler@56189
  1080
      assume i:"i \<in> Basis"
immler@56189
  1081
      have "a\<bullet>i \<le> b\<bullet>i"
immler@56189
  1082
        using as[THEN bspec[where x=i]] i by auto
immler@56189
  1083
      then have "a\<bullet>i \<le> ((1/2) *\<^sub>R (a+b)) \<bullet> i" "((1/2) *\<^sub>R (a+b)) \<bullet> i \<le> b\<bullet>i"
immler@56189
  1084
        by (auto simp: inner_add_left)
immler@56189
  1085
    }
immler@56189
  1086
    then have "cbox a b \<noteq> {}"
immler@56189
  1087
      using mem_box(2)[of "?x" a b] by auto
immler@56189
  1088
  }
immler@56189
  1089
  ultimately show ?th2 by blast
immler@56189
  1090
qed
immler@56189
  1091
immler@56189
  1092
lemma box_ne_empty:
immler@56189
  1093
  fixes a :: "'a::euclidean_space"
immler@56189
  1094
  shows "cbox a b \<noteq> {} \<longleftrightarrow> (\<forall>i\<in>Basis. a\<bullet>i \<le> b\<bullet>i)"
immler@56189
  1095
  and "box a b \<noteq> {} \<longleftrightarrow> (\<forall>i\<in>Basis. a\<bullet>i < b\<bullet>i)"
immler@56189
  1096
  unfolding box_eq_empty[of a b] by fastforce+
immler@56189
  1097
immler@56189
  1098
lemma
immler@56189
  1099
  fixes a :: "'a::euclidean_space"
immler@56189
  1100
  shows cbox_sing: "cbox a a = {a}"
immler@56189
  1101
    and box_sing: "box a a = {}"
immler@56189
  1102
  unfolding set_eq_iff mem_box eq_iff [symmetric]
immler@56189
  1103
  by (auto intro!: euclidean_eqI[where 'a='a])
immler@56189
  1104
     (metis all_not_in_conv nonempty_Basis)
immler@56189
  1105
immler@56189
  1106
lemma subset_box_imp:
immler@56189
  1107
  fixes a :: "'a::euclidean_space"
immler@56189
  1108
  shows "(\<forall>i\<in>Basis. a\<bullet>i \<le> c\<bullet>i \<and> d\<bullet>i \<le> b\<bullet>i) \<Longrightarrow> cbox c d \<subseteq> cbox a b"
immler@56189
  1109
    and "(\<forall>i\<in>Basis. a\<bullet>i < c\<bullet>i \<and> d\<bullet>i < b\<bullet>i) \<Longrightarrow> cbox c d \<subseteq> box a b"
immler@56189
  1110
    and "(\<forall>i\<in>Basis. a\<bullet>i \<le> c\<bullet>i \<and> d\<bullet>i \<le> b\<bullet>i) \<Longrightarrow> box c d \<subseteq> cbox a b"
immler@56189
  1111
     and "(\<forall>i\<in>Basis. a\<bullet>i \<le> c\<bullet>i \<and> d\<bullet>i \<le> b\<bullet>i) \<Longrightarrow> box c d \<subseteq> box a b"
immler@56189
  1112
  unfolding subset_eq[unfolded Ball_def] unfolding mem_box
wenzelm@58757
  1113
  by (best intro: order_trans less_le_trans le_less_trans less_imp_le)+
immler@56189
  1114
immler@56189
  1115
lemma box_subset_cbox:
immler@56189
  1116
  fixes a :: "'a::euclidean_space"
immler@56189
  1117
  shows "box a b \<subseteq> cbox a b"
immler@56189
  1118
  unfolding subset_eq [unfolded Ball_def] mem_box
immler@56189
  1119
  by (fast intro: less_imp_le)
immler@56189
  1120
immler@56189
  1121
lemma subset_box:
immler@56189
  1122
  fixes a :: "'a::euclidean_space"
immler@56189
  1123
  shows "cbox c d \<subseteq> cbox a b \<longleftrightarrow> (\<forall>i\<in>Basis. c\<bullet>i \<le> d\<bullet>i) --> (\<forall>i\<in>Basis. a\<bullet>i \<le> c\<bullet>i \<and> d\<bullet>i \<le> b\<bullet>i)" (is ?th1)
immler@56189
  1124
    and "cbox c d \<subseteq> box a b \<longleftrightarrow> (\<forall>i\<in>Basis. c\<bullet>i \<le> d\<bullet>i) --> (\<forall>i\<in>Basis. a\<bullet>i < c\<bullet>i \<and> d\<bullet>i < b\<bullet>i)" (is ?th2)
immler@56189
  1125
    and "box c d \<subseteq> cbox a b \<longleftrightarrow> (\<forall>i\<in>Basis. c\<bullet>i < d\<bullet>i) --> (\<forall>i\<in>Basis. a\<bullet>i \<le> c\<bullet>i \<and> d\<bullet>i \<le> b\<bullet>i)" (is ?th3)
immler@56189
  1126
    and "box c d \<subseteq> box a b \<longleftrightarrow> (\<forall>i\<in>Basis. c\<bullet>i < d\<bullet>i) --> (\<forall>i\<in>Basis. a\<bullet>i \<le> c\<bullet>i \<and> d\<bullet>i \<le> b\<bullet>i)" (is ?th4)
immler@56189
  1127
proof -
immler@56189
  1128
  show ?th1
immler@56189
  1129
    unfolding subset_eq and Ball_def and mem_box
immler@56189
  1130
    by (auto intro: order_trans)
immler@56189
  1131
  show ?th2
immler@56189
  1132
    unfolding subset_eq and Ball_def and mem_box
immler@56189
  1133
    by (auto intro: le_less_trans less_le_trans order_trans less_imp_le)
immler@56189
  1134
  {
immler@56189
  1135
    assume as: "box c d \<subseteq> cbox a b" "\<forall>i\<in>Basis. c\<bullet>i < d\<bullet>i"
immler@56189
  1136
    then have "box c d \<noteq> {}"
immler@56189
  1137
      unfolding box_eq_empty by auto
immler@56189
  1138
    fix i :: 'a
immler@56189
  1139
    assume i: "i \<in> Basis"
immler@56189
  1140
    (** TODO combine the following two parts as done in the HOL_light version. **)
immler@56189
  1141
    {
immler@56189
  1142
      let ?x = "(\<Sum>j\<in>Basis. (if j=i then ((min (a\<bullet>j) (d\<bullet>j))+c\<bullet>j)/2 else (c\<bullet>j+d\<bullet>j)/2) *\<^sub>R j)::'a"
immler@56189
  1143
      assume as2: "a\<bullet>i > c\<bullet>i"
immler@56189
  1144
      {
immler@56189
  1145
        fix j :: 'a
immler@56189
  1146
        assume j: "j \<in> Basis"
immler@56189
  1147
        then have "c \<bullet> j < ?x \<bullet> j \<and> ?x \<bullet> j < d \<bullet> j"
immler@56189
  1148
          apply (cases "j = i")
immler@56189
  1149
          using as(2)[THEN bspec[where x=j]] i
immler@56189
  1150
          apply (auto simp add: as2)
immler@56189
  1151
          done
immler@56189
  1152
      }
immler@56189
  1153
      then have "?x\<in>box c d"
immler@56189
  1154
        using i unfolding mem_box by auto
immler@56189
  1155
      moreover
immler@56189
  1156
      have "?x \<notin> cbox a b"
immler@56189
  1157
        unfolding mem_box
immler@56189
  1158
        apply auto
immler@56189
  1159
        apply (rule_tac x=i in bexI)
immler@56189
  1160
        using as(2)[THEN bspec[where x=i]] and as2 i
immler@56189
  1161
        apply auto
immler@56189
  1162
        done
immler@56189
  1163
      ultimately have False using as by auto
immler@56189
  1164
    }
immler@56189
  1165
    then have "a\<bullet>i \<le> c\<bullet>i" by (rule ccontr) auto
immler@56189
  1166
    moreover
immler@56189
  1167
    {
immler@56189
  1168
      let ?x = "(\<Sum>j\<in>Basis. (if j=i then ((max (b\<bullet>j) (c\<bullet>j))+d\<bullet>j)/2 else (c\<bullet>j+d\<bullet>j)/2) *\<^sub>R j)::'a"
immler@56189
  1169
      assume as2: "b\<bullet>i < d\<bullet>i"
immler@56189
  1170
      {
immler@56189
  1171
        fix j :: 'a
immler@56189
  1172
        assume "j\<in>Basis"
immler@56189
  1173
        then have "d \<bullet> j > ?x \<bullet> j \<and> ?x \<bullet> j > c \<bullet> j"
immler@56189
  1174
          apply (cases "j = i")
immler@56189
  1175
          using as(2)[THEN bspec[where x=j]]
immler@56189
  1176
          apply (auto simp add: as2)
immler@56189
  1177
          done
immler@56189
  1178
      }
immler@56189
  1179
      then have "?x\<in>box c d"
immler@56189
  1180
        unfolding mem_box by auto
immler@56189
  1181
      moreover
immler@56189
  1182
      have "?x\<notin>cbox a b"
immler@56189
  1183
        unfolding mem_box
immler@56189
  1184
        apply auto
immler@56189
  1185
        apply (rule_tac x=i in bexI)
immler@56189
  1186
        using as(2)[THEN bspec[where x=i]] and as2 using i
immler@56189
  1187
        apply auto
immler@56189
  1188
        done
immler@56189
  1189
      ultimately have False using as by auto
immler@56189
  1190
    }
immler@56189
  1191
    then have "b\<bullet>i \<ge> d\<bullet>i" by (rule ccontr) auto
immler@56189
  1192
    ultimately
immler@56189
  1193
    have "a\<bullet>i \<le> c\<bullet>i \<and> d\<bullet>i \<le> b\<bullet>i" by auto
immler@56189
  1194
  } note part1 = this
immler@56189
  1195
  show ?th3
immler@56189
  1196
    unfolding subset_eq and Ball_def and mem_box
immler@56189
  1197
    apply (rule, rule, rule, rule)
immler@56189
  1198
    apply (rule part1)
immler@56189
  1199
    unfolding subset_eq and Ball_def and mem_box
immler@56189
  1200
    prefer 4
immler@56189
  1201
    apply auto
immler@56189
  1202
    apply (erule_tac x=xa in allE, erule_tac x=xa in allE, fastforce)+
immler@56189
  1203
    done
immler@56189
  1204
  {
immler@56189
  1205
    assume as: "box c d \<subseteq> box a b" "\<forall>i\<in>Basis. c\<bullet>i < d\<bullet>i"
immler@56189
  1206
    fix i :: 'a
immler@56189
  1207
    assume i:"i\<in>Basis"
immler@56189
  1208
    from as(1) have "box c d \<subseteq> cbox a b"
immler@56189
  1209
      using box_subset_cbox[of a b] by auto
immler@56189
  1210
    then have "a\<bullet>i \<le> c\<bullet>i \<and> d\<bullet>i \<le> b\<bullet>i"
immler@56189
  1211
      using part1 and as(2) using i by auto
immler@56189
  1212
  } note * = this
immler@56189
  1213
  show ?th4
immler@56189
  1214
    unfolding subset_eq and Ball_def and mem_box
immler@56189
  1215
    apply (rule, rule, rule, rule)
immler@56189
  1216
    apply (rule *)
immler@56189
  1217
    unfolding subset_eq and Ball_def and mem_box
immler@56189
  1218
    prefer 4
immler@56189
  1219
    apply auto
immler@56189
  1220
    apply (erule_tac x=xa in allE, simp)+
immler@56189
  1221
    done
immler@56189
  1222
qed
immler@56189
  1223
immler@56189
  1224
lemma inter_interval:
immler@56189
  1225
  fixes a :: "'a::euclidean_space"
immler@56189
  1226
  shows "cbox a b \<inter> cbox c d =
immler@56189
  1227
    cbox (\<Sum>i\<in>Basis. max (a\<bullet>i) (c\<bullet>i) *\<^sub>R i) (\<Sum>i\<in>Basis. min (b\<bullet>i) (d\<bullet>i) *\<^sub>R i)"
immler@56189
  1228
  unfolding set_eq_iff and Int_iff and mem_box
immler@56189
  1229
  by auto
immler@56189
  1230
immler@56189
  1231
lemma disjoint_interval:
immler@56189
  1232
  fixes a::"'a::euclidean_space"
immler@56189
  1233
  shows "cbox a b \<inter> cbox c d = {} \<longleftrightarrow> (\<exists>i\<in>Basis. (b\<bullet>i < a\<bullet>i \<or> d\<bullet>i < c\<bullet>i \<or> b\<bullet>i < c\<bullet>i \<or> d\<bullet>i < a\<bullet>i))" (is ?th1)
immler@56189
  1234
    and "cbox a b \<inter> box c d = {} \<longleftrightarrow> (\<exists>i\<in>Basis. (b\<bullet>i < a\<bullet>i \<or> d\<bullet>i \<le> c\<bullet>i \<or> b\<bullet>i \<le> c\<bullet>i \<or> d\<bullet>i \<le> a\<bullet>i))" (is ?th2)
immler@56189
  1235
    and "box a b \<inter> cbox c d = {} \<longleftrightarrow> (\<exists>i\<in>Basis. (b\<bullet>i \<le> a\<bullet>i \<or> d\<bullet>i < c\<bullet>i \<or> b\<bullet>i \<le> c\<bullet>i \<or> d\<bullet>i \<le> a\<bullet>i))" (is ?th3)
immler@56189
  1236
    and "box a b \<inter> box c d = {} \<longleftrightarrow> (\<exists>i\<in>Basis. (b\<bullet>i \<le> a\<bullet>i \<or> d\<bullet>i \<le> c\<bullet>i \<or> b\<bullet>i \<le> c\<bullet>i \<or> d\<bullet>i \<le> a\<bullet>i))" (is ?th4)
immler@56189
  1237
proof -
immler@56189
  1238
  let ?z = "(\<Sum>i\<in>Basis. (((max (a\<bullet>i) (c\<bullet>i)) + (min (b\<bullet>i) (d\<bullet>i))) / 2) *\<^sub>R i)::'a"
immler@56189
  1239
  have **: "\<And>P Q. (\<And>i :: 'a. i \<in> Basis \<Longrightarrow> Q ?z i \<Longrightarrow> P i) \<Longrightarrow>
immler@56189
  1240
      (\<And>i x :: 'a. i \<in> Basis \<Longrightarrow> P i \<Longrightarrow> Q x i) \<Longrightarrow> (\<forall>x. \<exists>i\<in>Basis. Q x i) \<longleftrightarrow> (\<exists>i\<in>Basis. P i)"
immler@56189
  1241
    by blast
immler@56189
  1242
  note * = set_eq_iff Int_iff empty_iff mem_box ball_conj_distrib[symmetric] eq_False ball_simps(10)
immler@56189
  1243
  show ?th1 unfolding * by (intro **) auto
immler@56189
  1244
  show ?th2 unfolding * by (intro **) auto
immler@56189
  1245
  show ?th3 unfolding * by (intro **) auto
immler@56189
  1246
  show ?th4 unfolding * by (intro **) auto
immler@56189
  1247
qed
immler@56189
  1248
hoelzl@57447
  1249
lemma UN_box_eq_UNIV: "(\<Union>i::nat. box (- (real i *\<^sub>R One)) (real i *\<^sub>R One)) = UNIV"
hoelzl@57447
  1250
proof -
lp15@61609
  1251
  have "\<bar>x \<bullet> b\<bar> < real_of_int (ceiling (Max ((\<lambda>b. \<bar>x \<bullet> b\<bar>)`Basis)) + 1)"
wenzelm@60462
  1252
    if [simp]: "b \<in> Basis" for x b :: 'a
wenzelm@60462
  1253
  proof -
lp15@61609
  1254
    have "\<bar>x \<bullet> b\<bar> \<le> real_of_int (ceiling \<bar>x \<bullet> b\<bar>)"
lp15@61609
  1255
      by (rule le_of_int_ceiling)
lp15@61609
  1256
    also have "\<dots> \<le> real_of_int (ceiling (Max ((\<lambda>b. \<bar>x \<bullet> b\<bar>)`Basis)))"
nipkow@59587
  1257
      by (auto intro!: ceiling_mono)
lp15@61609
  1258
    also have "\<dots> < real_of_int (ceiling (Max ((\<lambda>b. \<bar>x \<bullet> b\<bar>)`Basis)) + 1)"
hoelzl@57447
  1259
      by simp
wenzelm@60462
  1260
    finally show ?thesis .
wenzelm@60462
  1261
  qed
wenzelm@60462
  1262
  then have "\<exists>n::nat. \<forall>b\<in>Basis. \<bar>x \<bullet> b\<bar> < real n" for x :: 'a
nipkow@59587
  1263
    by (metis order.strict_trans reals_Archimedean2)
hoelzl@57447
  1264
  moreover have "\<And>x b::'a. \<And>n::nat.  \<bar>x \<bullet> b\<bar> < real n \<longleftrightarrow> - real n < x \<bullet> b \<and> x \<bullet> b < real n"
hoelzl@57447
  1265
    by auto
hoelzl@57447
  1266
  ultimately show ?thesis
hoelzl@57447
  1267
    by (auto simp: box_def inner_setsum_left inner_Basis setsum.If_cases)
hoelzl@57447
  1268
qed
hoelzl@57447
  1269
wenzelm@60420
  1270
text \<open>Intervals in general, including infinite and mixtures of open and closed.\<close>
immler@56189
  1271
immler@56189
  1272
definition "is_interval (s::('a::euclidean_space) set) \<longleftrightarrow>
immler@56189
  1273
  (\<forall>a\<in>s. \<forall>b\<in>s. \<forall>x. (\<forall>i\<in>Basis. ((a\<bullet>i \<le> x\<bullet>i \<and> x\<bullet>i \<le> b\<bullet>i) \<or> (b\<bullet>i \<le> x\<bullet>i \<and> x\<bullet>i \<le> a\<bullet>i))) \<longrightarrow> x \<in> s)"
immler@56189
  1274
immler@56189
  1275
lemma is_interval_cbox: "is_interval (cbox a (b::'a::euclidean_space))" (is ?th1)
immler@56189
  1276
  and is_interval_box: "is_interval (box a b)" (is ?th2)
immler@56189
  1277
  unfolding is_interval_def mem_box Ball_def atLeastAtMost_iff
immler@56189
  1278
  by (meson order_trans le_less_trans less_le_trans less_trans)+
immler@56189
  1279
lp15@61609
  1280
lemma is_interval_empty [iff]: "is_interval {}"
lp15@61609
  1281
  unfolding is_interval_def  by simp
lp15@61609
  1282
lp15@61609
  1283
lemma is_interval_univ [iff]: "is_interval UNIV"
lp15@61609
  1284
  unfolding is_interval_def  by simp
immler@56189
  1285
immler@56189
  1286
lemma mem_is_intervalI:
immler@56189
  1287
  assumes "is_interval s"
immler@56189
  1288
  assumes "a \<in> s" "b \<in> s"
immler@56189
  1289
  assumes "\<And>i. i \<in> Basis \<Longrightarrow> a \<bullet> i \<le> x \<bullet> i \<and> x \<bullet> i \<le> b \<bullet> i \<or> b \<bullet> i \<le> x \<bullet> i \<and> x \<bullet> i \<le> a \<bullet> i"
immler@56189
  1290
  shows "x \<in> s"
immler@56189
  1291
  by (rule assms(1)[simplified is_interval_def, rule_format, OF assms(2,3,4)])
immler@56189
  1292
immler@56189
  1293
lemma interval_subst:
immler@56189
  1294
  fixes S::"'a::euclidean_space set"
immler@56189
  1295
  assumes "is_interval S"
immler@56189
  1296
  assumes "x \<in> S" "y j \<in> S"
immler@56189
  1297
  assumes "j \<in> Basis"
immler@56189
  1298
  shows "(\<Sum>i\<in>Basis. (if i = j then y i \<bullet> i else x \<bullet> i) *\<^sub>R i) \<in> S"
immler@56189
  1299
  by (rule mem_is_intervalI[OF assms(1,2)]) (auto simp: assms)
immler@56189
  1300
immler@56189
  1301
lemma mem_box_componentwiseI:
immler@56189
  1302
  fixes S::"'a::euclidean_space set"
immler@56189
  1303
  assumes "is_interval S"
immler@56189
  1304
  assumes "\<And>i. i \<in> Basis \<Longrightarrow> x \<bullet> i \<in> ((\<lambda>x. x \<bullet> i) ` S)"
immler@56189
  1305
  shows "x \<in> S"
immler@56189
  1306
proof -
immler@56189
  1307
  from assms have "\<forall>i \<in> Basis. \<exists>s \<in> S. x \<bullet> i = s \<bullet> i"
immler@56189
  1308
    by auto
immler@56189
  1309
  with finite_Basis obtain s and bs::"'a list" where
immler@56189
  1310
    s: "\<And>i. i \<in> Basis \<Longrightarrow> x \<bullet> i = s i \<bullet> i" "\<And>i. i \<in> Basis \<Longrightarrow> s i \<in> S" and
immler@56189
  1311
    bs: "set bs = Basis" "distinct bs"
immler@56189
  1312
    by (metis finite_distinct_list)
immler@56189
  1313
  from nonempty_Basis s obtain j where j: "j \<in> Basis" "s j \<in> S" by blast
immler@56189
  1314
  def y \<equiv> "rec_list
immler@56189
  1315
    (s j)
immler@56189
  1316
    (\<lambda>j _ Y. (\<Sum>i\<in>Basis. (if i = j then s i \<bullet> i else Y \<bullet> i) *\<^sub>R i))"
immler@56189
  1317
  have "x = (\<Sum>i\<in>Basis. (if i \<in> set bs then s i \<bullet> i else s j \<bullet> i) *\<^sub>R i)"
immler@56189
  1318
    using bs by (auto simp add: s(1)[symmetric] euclidean_representation)
immler@56189
  1319
  also have [symmetric]: "y bs = \<dots>"
immler@56189
  1320
    using bs(2) bs(1)[THEN equalityD1]
immler@56189
  1321
    by (induct bs) (auto simp: y_def euclidean_representation intro!: euclidean_eqI[where 'a='a])
immler@56189
  1322
  also have "y bs \<in> S"
immler@56189
  1323
    using bs(1)[THEN equalityD1]
immler@56189
  1324
    apply (induct bs)
immler@56189
  1325
    apply (auto simp: y_def j)
immler@56189
  1326
    apply (rule interval_subst[OF assms(1)])
immler@56189
  1327
    apply (auto simp: s)
immler@56189
  1328
    done
immler@56189
  1329
  finally show ?thesis .
immler@56189
  1330
qed
immler@56189
  1331
himmelma@33175
  1332
wenzelm@60420
  1333
subsection\<open>Connectedness\<close>
himmelma@33175
  1334
himmelma@33175
  1335
lemma connected_local:
wenzelm@53255
  1336
 "connected S \<longleftrightarrow>
wenzelm@53255
  1337
  \<not> (\<exists>e1 e2.
wenzelm@53255
  1338
      openin (subtopology euclidean S) e1 \<and>
wenzelm@53255
  1339
      openin (subtopology euclidean S) e2 \<and>
wenzelm@53255
  1340
      S \<subseteq> e1 \<union> e2 \<and>
wenzelm@53255
  1341
      e1 \<inter> e2 = {} \<and>
wenzelm@53255
  1342
      e1 \<noteq> {} \<and>
wenzelm@53255
  1343
      e2 \<noteq> {})"
wenzelm@53282
  1344
  unfolding connected_def openin_open
lp15@59765
  1345
  by safe blast+
himmelma@33175
  1346
huffman@34105
  1347
lemma exists_diff:
huffman@34105
  1348
  fixes P :: "'a set \<Rightarrow> bool"
wenzelm@60462
  1349
  shows "(\<exists>S. P (- S)) \<longleftrightarrow> (\<exists>S. P S)" (is "?lhs \<longleftrightarrow> ?rhs")
wenzelm@53255
  1350
proof -
wenzelm@53255
  1351
  {
wenzelm@53255
  1352
    assume "?lhs"
wenzelm@53255
  1353
    then have ?rhs by blast
wenzelm@53255
  1354
  }
himmelma@33175
  1355
  moreover
wenzelm@53255
  1356
  {
wenzelm@53255
  1357
    fix S
wenzelm@53255
  1358
    assume H: "P S"
huffman@34105
  1359
    have "S = - (- S)" by auto
wenzelm@53255
  1360
    with H have "P (- (- S))" by metis
wenzelm@53255
  1361
  }
himmelma@33175
  1362
  ultimately show ?thesis by metis
himmelma@33175
  1363
qed
himmelma@33175
  1364
himmelma@33175
  1365
lemma connected_clopen: "connected S \<longleftrightarrow>
wenzelm@53255
  1366
  (\<forall>T. openin (subtopology euclidean S) T \<and>
wenzelm@53255
  1367
     closedin (subtopology euclidean S) T \<longrightarrow> T = {} \<or> T = S)" (is "?lhs \<longleftrightarrow> ?rhs")
wenzelm@53255
  1368
proof -
wenzelm@53255
  1369
  have "\<not> connected S \<longleftrightarrow>
wenzelm@53255
  1370
    (\<exists>e1 e2. open e1 \<and> open (- e2) \<and> S \<subseteq> e1 \<union> (- e2) \<and> e1 \<inter> (- e2) \<inter> S = {} \<and> e1 \<inter> S \<noteq> {} \<and> (- e2) \<inter> S \<noteq> {})"
himmelma@33175
  1371
    unfolding connected_def openin_open closedin_closed
lp15@55775
  1372
    by (metis double_complement)
wenzelm@53282
  1373
  then have th0: "connected S \<longleftrightarrow>
wenzelm@53255
  1374
    \<not> (\<exists>e2 e1. closed e2 \<and> open e1 \<and> S \<subseteq> e1 \<union> (- e2) \<and> e1 \<inter> (- e2) \<inter> S = {} \<and> e1 \<inter> S \<noteq> {} \<and> (- e2) \<inter> S \<noteq> {})"
wenzelm@52624
  1375
    (is " _ \<longleftrightarrow> \<not> (\<exists>e2 e1. ?P e2 e1)")
wenzelm@52624
  1376
    apply (simp add: closed_def)
wenzelm@52624
  1377
    apply metis
wenzelm@52624
  1378
    done
himmelma@33175
  1379
  have th1: "?rhs \<longleftrightarrow> \<not> (\<exists>t' t. closed t'\<and>t = S\<inter>t' \<and> t\<noteq>{} \<and> t\<noteq>S \<and> (\<exists>t'. open t' \<and> t = S \<inter> t'))"
himmelma@33175
  1380
    (is "_ \<longleftrightarrow> \<not> (\<exists>t' t. ?Q t' t)")
himmelma@33175
  1381
    unfolding connected_def openin_open closedin_closed by auto
wenzelm@53255
  1382
  {
wenzelm@53255
  1383
    fix e2
wenzelm@53255
  1384
    {
wenzelm@53255
  1385
      fix e1
wenzelm@53282
  1386
      have "?P e2 e1 \<longleftrightarrow> (\<exists>t. closed e2 \<and> t = S\<inter>e2 \<and> open e1 \<and> t = S\<inter>e1 \<and> t\<noteq>{} \<and> t \<noteq> S)"
wenzelm@53255
  1387
        by auto
wenzelm@53255
  1388
    }
wenzelm@53255
  1389
    then have "(\<exists>e1. ?P e2 e1) \<longleftrightarrow> (\<exists>t. ?Q e2 t)"
wenzelm@53255
  1390
      by metis
wenzelm@53255
  1391
  }
wenzelm@53255
  1392
  then have "\<forall>e2. (\<exists>e1. ?P e2 e1) \<longleftrightarrow> (\<exists>t. ?Q e2 t)"
wenzelm@53255
  1393
    by blast
wenzelm@53255
  1394
  then show ?thesis
wenzelm@53255
  1395
    unfolding th0 th1 by simp
himmelma@33175
  1396
qed
himmelma@33175
  1397
wenzelm@60420
  1398
subsection\<open>Limit points\<close>
himmelma@33175
  1399
wenzelm@53282
  1400
definition (in topological_space) islimpt:: "'a \<Rightarrow> 'a set \<Rightarrow> bool"  (infixr "islimpt" 60)
wenzelm@53255
  1401
  where "x islimpt S \<longleftrightarrow> (\<forall>T. x\<in>T \<longrightarrow> open T \<longrightarrow> (\<exists>y\<in>S. y\<in>T \<and> y\<noteq>x))"
himmelma@33175
  1402
himmelma@33175
  1403
lemma islimptI:
himmelma@33175
  1404
  assumes "\<And>T. x \<in> T \<Longrightarrow> open T \<Longrightarrow> \<exists>y\<in>S. y \<in> T \<and> y \<noteq> x"
himmelma@33175
  1405
  shows "x islimpt S"
himmelma@33175
  1406
  using assms unfolding islimpt_def by auto
himmelma@33175
  1407
himmelma@33175
  1408
lemma islimptE:
himmelma@33175
  1409
  assumes "x islimpt S" and "x \<in> T" and "open T"
himmelma@33175
  1410
  obtains y where "y \<in> S" and "y \<in> T" and "y \<noteq> x"
himmelma@33175
  1411
  using assms unfolding islimpt_def by auto
himmelma@33175
  1412
huffman@44584
  1413
lemma islimpt_iff_eventually: "x islimpt S \<longleftrightarrow> \<not> eventually (\<lambda>y. y \<notin> S) (at x)"
huffman@44584
  1414
  unfolding islimpt_def eventually_at_topological by auto
huffman@44584
  1415
wenzelm@53255
  1416
lemma islimpt_subset: "x islimpt S \<Longrightarrow> S \<subseteq> T \<Longrightarrow> x islimpt T"
huffman@44584
  1417
  unfolding islimpt_def by fast
himmelma@33175
  1418
himmelma@33175
  1419
lemma islimpt_approachable:
himmelma@33175
  1420
  fixes x :: "'a::metric_space"
himmelma@33175
  1421
  shows "x islimpt S \<longleftrightarrow> (\<forall>e>0. \<exists>x'\<in>S. x' \<noteq> x \<and> dist x' x < e)"
huffman@44584
  1422
  unfolding islimpt_iff_eventually eventually_at by fast
himmelma@33175
  1423
himmelma@33175
  1424
lemma islimpt_approachable_le:
himmelma@33175
  1425
  fixes x :: "'a::metric_space"
wenzelm@53640
  1426
  shows "x islimpt S \<longleftrightarrow> (\<forall>e>0. \<exists>x'\<in> S. x' \<noteq> x \<and> dist x' x \<le> e)"
himmelma@33175
  1427
  unfolding islimpt_approachable
huffman@44584
  1428
  using approachable_lt_le [where f="\<lambda>y. dist y x" and P="\<lambda>y. y \<notin> S \<or> y = x",
huffman@44584
  1429
    THEN arg_cong [where f=Not]]
huffman@44584
  1430
  by (simp add: Bex_def conj_commute conj_left_commute)
himmelma@33175
  1431
huffman@44571
  1432
lemma islimpt_UNIV_iff: "x islimpt UNIV \<longleftrightarrow> \<not> open {x}"
huffman@44571
  1433
  unfolding islimpt_def by (safe, fast, case_tac "T = {x}", fast, fast)
huffman@44571
  1434
hoelzl@51351
  1435
lemma islimpt_punctured: "x islimpt S = x islimpt (S-{x})"
hoelzl@51351
  1436
  unfolding islimpt_def by blast
hoelzl@51351
  1437
wenzelm@60420
  1438
text \<open>A perfect space has no isolated points.\<close>
huffman@44210
  1439
huffman@44571
  1440
lemma islimpt_UNIV [simp, intro]: "(x::'a::perfect_space) islimpt UNIV"
huffman@44571
  1441
  unfolding islimpt_UNIV_iff by (rule not_open_singleton)
himmelma@33175
  1442
himmelma@33175
  1443
lemma perfect_choose_dist:
huffman@44072
  1444
  fixes x :: "'a::{perfect_space, metric_space}"
himmelma@33175
  1445
  shows "0 < r \<Longrightarrow> \<exists>a. a \<noteq> x \<and> dist a x < r"
wenzelm@53255
  1446
  using islimpt_UNIV [of x]
wenzelm@53255
  1447
  by (simp add: islimpt_approachable)
himmelma@33175
  1448
himmelma@33175
  1449
lemma closed_limpt: "closed S \<longleftrightarrow> (\<forall>x. x islimpt S \<longrightarrow> x \<in> S)"
himmelma@33175
  1450
  unfolding closed_def
himmelma@33175
  1451
  apply (subst open_subopen)
huffman@34105
  1452
  apply (simp add: islimpt_def subset_eq)
wenzelm@52624
  1453
  apply (metis ComplE ComplI)
wenzelm@52624
  1454
  done
himmelma@33175
  1455
himmelma@33175
  1456
lemma islimpt_EMPTY[simp]: "\<not> x islimpt {}"
himmelma@33175
  1457
  unfolding islimpt_def by auto
himmelma@33175
  1458
himmelma@33175
  1459
lemma finite_set_avoid:
himmelma@33175
  1460
  fixes a :: "'a::metric_space"
wenzelm@53255
  1461
  assumes fS: "finite S"
wenzelm@53640
  1462
  shows  "\<exists>d>0. \<forall>x\<in>S. x \<noteq> a \<longrightarrow> d \<le> dist a x"
wenzelm@53255
  1463
proof (induct rule: finite_induct[OF fS])
wenzelm@53255
  1464
  case 1
wenzelm@53255
  1465
  then show ?case by (auto intro: zero_less_one)
himmelma@33175
  1466
next
himmelma@33175
  1467
  case (2 x F)
wenzelm@60462
  1468
  from 2 obtain d where d: "d > 0" "\<forall>x\<in>F. x \<noteq> a \<longrightarrow> d \<le> dist a x"
wenzelm@53255
  1469
    by blast
wenzelm@53255
  1470
  show ?case
wenzelm@53255
  1471
  proof (cases "x = a")
wenzelm@53255
  1472
    case True
wenzelm@53255
  1473
    then show ?thesis using d by auto
wenzelm@53255
  1474
  next
wenzelm@53255
  1475
    case False
himmelma@33175
  1476
    let ?d = "min d (dist a x)"
wenzelm@53255
  1477
    have dp: "?d > 0"
wenzelm@53255
  1478
      using False d(1) using dist_nz by auto
wenzelm@60462
  1479
    from d have d': "\<forall>x\<in>F. x \<noteq> a \<longrightarrow> ?d \<le> dist a x"
wenzelm@53255
  1480
      by auto
wenzelm@53255
  1481
    with dp False show ?thesis
wenzelm@53255
  1482
      by (auto intro!: exI[where x="?d"])
wenzelm@53255
  1483
  qed
himmelma@33175
  1484
qed
himmelma@33175
  1485
himmelma@33175
  1486
lemma islimpt_Un: "x islimpt (S \<union> T) \<longleftrightarrow> x islimpt S \<or> x islimpt T"
huffman@50897
  1487
  by (simp add: islimpt_iff_eventually eventually_conj_iff)
himmelma@33175
  1488
himmelma@33175
  1489
lemma discrete_imp_closed:
himmelma@33175
  1490
  fixes S :: "'a::metric_space set"
wenzelm@53255
  1491
  assumes e: "0 < e"
wenzelm@53255
  1492
    and d: "\<forall>x \<in> S. \<forall>y \<in> S. dist y x < e \<longrightarrow> y = x"
himmelma@33175
  1493
  shows "closed S"
wenzelm@53255
  1494
proof -
wenzelm@53255
  1495
  {
wenzelm@53255
  1496
    fix x
wenzelm@53255
  1497
    assume C: "\<forall>e>0. \<exists>x'\<in>S. x' \<noteq> x \<and> dist x' x < e"
himmelma@33175
  1498
    from e have e2: "e/2 > 0" by arith
wenzelm@53282
  1499
    from C[rule_format, OF e2] obtain y where y: "y \<in> S" "y \<noteq> x" "dist y x < e/2"
wenzelm@53255
  1500
      by blast
himmelma@33175
  1501
    let ?m = "min (e/2) (dist x y) "
wenzelm@53255
  1502
    from e2 y(2) have mp: "?m > 0"
wenzelm@53291
  1503
      by (simp add: dist_nz[symmetric])
wenzelm@53282
  1504
    from C[rule_format, OF mp] obtain z where z: "z \<in> S" "z \<noteq> x" "dist z x < ?m"
wenzelm@53255
  1505
      by blast
himmelma@33175
  1506
    have th: "dist z y < e" using z y
himmelma@33175
  1507
      by (intro dist_triangle_lt [where z=x], simp)
himmelma@33175
  1508
    from d[rule_format, OF y(1) z(1) th] y z
himmelma@33175
  1509
    have False by (auto simp add: dist_commute)}
wenzelm@53255
  1510
  then show ?thesis
wenzelm@53255
  1511
    by (metis islimpt_approachable closed_limpt [where 'a='a])
himmelma@33175
  1512
qed
himmelma@33175
  1513
eberlm@61524
  1514
lemma closed_of_nat_image: "closed (of_nat ` A :: 'a :: real_normed_algebra_1 set)"
eberlm@61524
  1515
  by (rule discrete_imp_closed[of 1]) (auto simp: dist_of_nat)
eberlm@61524
  1516
eberlm@61524
  1517
lemma closed_of_int_image: "closed (of_int ` A :: 'a :: real_normed_algebra_1 set)"
eberlm@61524
  1518
  by (rule discrete_imp_closed[of 1]) (auto simp: dist_of_int)
eberlm@61524
  1519
eberlm@61524
  1520
lemma closed_Nats [simp]: "closed (\<nat> :: 'a :: real_normed_algebra_1 set)"
eberlm@61524
  1521
  unfolding Nats_def by (rule closed_of_nat_image)
eberlm@61524
  1522
eberlm@61524
  1523
lemma closed_Ints [simp]: "closed (\<int> :: 'a :: real_normed_algebra_1 set)"
eberlm@61524
  1524
  unfolding Ints_def by (rule closed_of_int_image)
eberlm@61524
  1525
huffman@44210
  1526
wenzelm@60420
  1527
subsection \<open>Interior of a Set\<close>
huffman@44210
  1528
huffman@44519
  1529
definition "interior S = \<Union>{T. open T \<and> T \<subseteq> S}"
huffman@44519
  1530
huffman@44519
  1531
lemma interiorI [intro?]:
huffman@44519
  1532
  assumes "open T" and "x \<in> T" and "T \<subseteq> S"
huffman@44519
  1533
  shows "x \<in> interior S"
huffman@44519
  1534
  using assms unfolding interior_def by fast
huffman@44519
  1535
huffman@44519
  1536
lemma interiorE [elim?]:
huffman@44519
  1537
  assumes "x \<in> interior S"
huffman@44519
  1538
  obtains T where "open T" and "x \<in> T" and "T \<subseteq> S"
huffman@44519
  1539
  using assms unfolding interior_def by fast
huffman@44519
  1540
huffman@44519
  1541
lemma open_interior [simp, intro]: "open (interior S)"
huffman@44519
  1542
  by (simp add: interior_def open_Union)
huffman@44519
  1543
huffman@44519
  1544
lemma interior_subset: "interior S \<subseteq> S"
huffman@44519
  1545
  by (auto simp add: interior_def)
huffman@44519
  1546
huffman@44519
  1547
lemma interior_maximal: "T \<subseteq> S \<Longrightarrow> open T \<Longrightarrow> T \<subseteq> interior S"
huffman@44519
  1548
  by (auto simp add: interior_def)
huffman@44519
  1549
huffman@44519
  1550
lemma interior_open: "open S \<Longrightarrow> interior S = S"
huffman@44519
  1551
  by (intro equalityI interior_subset interior_maximal subset_refl)
himmelma@33175
  1552
himmelma@33175
  1553
lemma interior_eq: "interior S = S \<longleftrightarrow> open S"
huffman@44519
  1554
  by (metis open_interior interior_open)
huffman@44519
  1555
huffman@44519
  1556
lemma open_subset_interior: "open S \<Longrightarrow> S \<subseteq> interior T \<longleftrightarrow> S \<subseteq> T"
himmelma@33175
  1557
  by (metis interior_maximal interior_subset subset_trans)
himmelma@33175
  1558
huffman@44519
  1559
lemma interior_empty [simp]: "interior {} = {}"
huffman@44519
  1560
  using open_empty by (rule interior_open)
huffman@44519
  1561
huffman@44522
  1562
lemma interior_UNIV [simp]: "interior UNIV = UNIV"
huffman@44522
  1563
  using open_UNIV by (rule interior_open)
huffman@44522
  1564
huffman@44519
  1565
lemma interior_interior [simp]: "interior (interior S) = interior S"
huffman@44519
  1566
  using open_interior by (rule interior_open)
huffman@44519
  1567
huffman@44522
  1568
lemma interior_mono: "S \<subseteq> T \<Longrightarrow> interior S \<subseteq> interior T"
huffman@44522
  1569
  by (auto simp add: interior_def)
huffman@44519
  1570
huffman@44519
  1571
lemma interior_unique:
huffman@44519
  1572
  assumes "T \<subseteq> S" and "open T"
huffman@44519
  1573
  assumes "\<And>T'. T' \<subseteq> S \<Longrightarrow> open T' \<Longrightarrow> T' \<subseteq> T"
huffman@44519
  1574
  shows "interior S = T"
huffman@44519
  1575
  by (intro equalityI assms interior_subset open_interior interior_maximal)
huffman@44519
  1576
paulson@61518
  1577
lemma interior_singleton [simp]:
paulson@61518
  1578
      fixes a :: "'a::perfect_space" shows "interior {a} = {}"
paulson@61518
  1579
  apply (rule interior_unique, simp_all)
paulson@61518
  1580
  using not_open_singleton subset_singletonD by fastforce
paulson@61518
  1581
paulson@61518
  1582
lemma interior_Int [simp]: "interior (S \<inter> T) = interior S \<inter> interior T"
huffman@44522
  1583
  by (intro equalityI Int_mono Int_greatest interior_mono Int_lower1
huffman@44519
  1584
    Int_lower2 interior_maximal interior_subset open_Int open_interior)
huffman@44519
  1585
huffman@44519
  1586
lemma mem_interior: "x \<in> interior S \<longleftrightarrow> (\<exists>e>0. ball x e \<subseteq> S)"
huffman@44519
  1587
  using open_contains_ball_eq [where S="interior S"]
huffman@44519
  1588
  by (simp add: open_subset_interior)
himmelma@33175
  1589
eberlm@61531
  1590
lemma eventually_nhds_in_nhd: "x \<in> interior s \<Longrightarrow> eventually (\<lambda>y. y \<in> s) (nhds x)"
eberlm@61531
  1591
  using interior_subset[of s] by (subst eventually_nhds) blast
eberlm@61531
  1592
himmelma@33175
  1593
lemma interior_limit_point [intro]:
himmelma@33175
  1594
  fixes x :: "'a::perfect_space"
wenzelm@53255
  1595
  assumes x: "x \<in> interior S"
wenzelm@53255
  1596
  shows "x islimpt S"
huffman@44072
  1597
  using x islimpt_UNIV [of x]
huffman@44072
  1598
  unfolding interior_def islimpt_def
huffman@44072
  1599
  apply (clarsimp, rename_tac T T')
huffman@44072
  1600
  apply (drule_tac x="T \<inter> T'" in spec)
huffman@44072
  1601
  apply (auto simp add: open_Int)
huffman@44072
  1602
  done
himmelma@33175
  1603
himmelma@33175
  1604
lemma interior_closed_Un_empty_interior:
wenzelm@53255
  1605
  assumes cS: "closed S"
wenzelm@53255
  1606
    and iT: "interior T = {}"
huffman@44519
  1607
  shows "interior (S \<union> T) = interior S"
himmelma@33175
  1608
proof
huffman@44519
  1609
  show "interior S \<subseteq> interior (S \<union> T)"
wenzelm@53255
  1610
    by (rule interior_mono) (rule Un_upper1)
himmelma@33175
  1611
  show "interior (S \<union> T) \<subseteq> interior S"
himmelma@33175
  1612
  proof
wenzelm@53255
  1613
    fix x
wenzelm@53255
  1614
    assume "x \<in> interior (S \<union> T)"
huffman@44519
  1615
    then obtain R where "open R" "x \<in> R" "R \<subseteq> S \<union> T" ..
himmelma@33175
  1616
    show "x \<in> interior S"
himmelma@33175
  1617
    proof (rule ccontr)
himmelma@33175
  1618
      assume "x \<notin> interior S"
wenzelm@60420
  1619
      with \<open>x \<in> R\<close> \<open>open R\<close> obtain y where "y \<in> R - S"
huffman@44519
  1620
        unfolding interior_def by fast
wenzelm@60420
  1621
      from \<open>open R\<close> \<open>closed S\<close> have "open (R - S)"
wenzelm@53282
  1622
        by (rule open_Diff)
wenzelm@60420
  1623
      from \<open>R \<subseteq> S \<union> T\<close> have "R - S \<subseteq> T"
wenzelm@53282
  1624
        by fast
wenzelm@60420
  1625
      from \<open>y \<in> R - S\<close> \<open>open (R - S)\<close> \<open>R - S \<subseteq> T\<close> \<open>interior T = {}\<close> show False
wenzelm@53282
  1626
        unfolding interior_def by fast
himmelma@33175
  1627
    qed
himmelma@33175
  1628
  qed
himmelma@33175
  1629
qed
himmelma@33175
  1630
huffman@44365
  1631
lemma interior_Times: "interior (A \<times> B) = interior A \<times> interior B"
huffman@44365
  1632
proof (rule interior_unique)
huffman@44365
  1633
  show "interior A \<times> interior B \<subseteq> A \<times> B"
huffman@44365
  1634
    by (intro Sigma_mono interior_subset)
huffman@44365
  1635
  show "open (interior A \<times> interior B)"
huffman@44365
  1636
    by (intro open_Times open_interior)
wenzelm@53255
  1637
  fix T
wenzelm@53255
  1638
  assume "T \<subseteq> A \<times> B" and "open T"
wenzelm@53255
  1639
  then show "T \<subseteq> interior A \<times> interior B"
wenzelm@53282
  1640
  proof safe
wenzelm@53255
  1641
    fix x y
wenzelm@53255
  1642
    assume "(x, y) \<in> T"
huffman@44519
  1643
    then obtain C D where "open C" "open D" "C \<times> D \<subseteq> T" "x \<in> C" "y \<in> D"
wenzelm@60420
  1644
      using \<open>open T\<close> unfolding open_prod_def by fast
wenzelm@53255
  1645
    then have "open C" "open D" "C \<subseteq> A" "D \<subseteq> B" "x \<in> C" "y \<in> D"
wenzelm@60420
  1646
      using \<open>T \<subseteq> A \<times> B\<close> by auto
wenzelm@53255
  1647
    then show "x \<in> interior A" and "y \<in> interior B"
huffman@44519
  1648
      by (auto intro: interiorI)
huffman@44519
  1649
  qed
huffman@44365
  1650
qed
huffman@44365
  1651
hoelzl@61245
  1652
lemma interior_Ici:
hoelzl@61245
  1653
  fixes x :: "'a :: {dense_linorder, linorder_topology}"
hoelzl@61245
  1654
  assumes "b < x"
hoelzl@61245
  1655
  shows "interior { x ..} = { x <..}"
hoelzl@61245
  1656
proof (rule interior_unique)
hoelzl@61245
  1657
  fix T assume "T \<subseteq> {x ..}" "open T"
hoelzl@61245
  1658
  moreover have "x \<notin> T"
hoelzl@61245
  1659
  proof
hoelzl@61245
  1660
    assume "x \<in> T"
hoelzl@61245
  1661
    obtain y where "y < x" "{y <.. x} \<subseteq> T"
hoelzl@61245
  1662
      using open_left[OF \<open>open T\<close> \<open>x \<in> T\<close> \<open>b < x\<close>] by auto
hoelzl@61245
  1663
    with dense[OF \<open>y < x\<close>] obtain z where "z \<in> T" "z < x"
hoelzl@61245
  1664
      by (auto simp: subset_eq Ball_def)
hoelzl@61245
  1665
    with \<open>T \<subseteq> {x ..}\<close> show False by auto
hoelzl@61245
  1666
  qed
hoelzl@61245
  1667
  ultimately show "T \<subseteq> {x <..}"
hoelzl@61245
  1668
    by (auto simp: subset_eq less_le)
hoelzl@61245
  1669
qed auto
hoelzl@61245
  1670
hoelzl@61245
  1671
lemma interior_Iic:
hoelzl@61245
  1672
  fixes x :: "'a :: {dense_linorder, linorder_topology}"
hoelzl@61245
  1673
  assumes "x < b"
hoelzl@61245
  1674
  shows "interior {.. x} = {..< x}"
hoelzl@61245
  1675
proof (rule interior_unique)
hoelzl@61245
  1676
  fix T assume "T \<subseteq> {.. x}" "open T"
hoelzl@61245
  1677
  moreover have "x \<notin> T"
hoelzl@61245
  1678
  proof
hoelzl@61245
  1679
    assume "x \<in> T"
hoelzl@61245
  1680
    obtain y where "x < y" "{x ..< y} \<subseteq> T"
hoelzl@61245
  1681
      using open_right[OF \<open>open T\<close> \<open>x \<in> T\<close> \<open>x < b\<close>] by auto
hoelzl@61245
  1682
    with dense[OF \<open>x < y\<close>] obtain z where "z \<in> T" "x < z"
hoelzl@61245
  1683
      by (auto simp: subset_eq Ball_def less_le)
hoelzl@61245
  1684
    with \<open>T \<subseteq> {.. x}\<close> show False by auto
hoelzl@61245
  1685
  qed
hoelzl@61245
  1686
  ultimately show "T \<subseteq> {..< x}"
hoelzl@61245
  1687
    by (auto simp: subset_eq less_le)
hoelzl@61245
  1688
qed auto
himmelma@33175
  1689
wenzelm@60420
  1690
subsection \<open>Closure of a Set\<close>
himmelma@33175
  1691
himmelma@33175
  1692
definition "closure S = S \<union> {x | x. x islimpt S}"
himmelma@33175
  1693
huffman@44518
  1694
lemma interior_closure: "interior S = - (closure (- S))"
huffman@44518
  1695
  unfolding interior_def closure_def islimpt_def by auto
huffman@44518
  1696
huffman@34105
  1697
lemma closure_interior: "closure S = - interior (- S)"
huffman@44518
  1698
  unfolding interior_closure by simp
himmelma@33175
  1699
himmelma@33175
  1700
lemma closed_closure[simp, intro]: "closed (closure S)"
huffman@44518
  1701
  unfolding closure_interior by (simp add: closed_Compl)
huffman@44518
  1702
huffman@44518
  1703
lemma closure_subset: "S \<subseteq> closure S"
huffman@44518
  1704
  unfolding closure_def by simp
himmelma@33175
  1705
himmelma@33175
  1706
lemma closure_hull: "closure S = closed hull S"
huffman@44519
  1707
  unfolding hull_def closure_interior interior_def by auto
himmelma@33175
  1708
himmelma@33175
  1709
lemma closure_eq: "closure S = S \<longleftrightarrow> closed S"
huffman@44519
  1710
  unfolding closure_hull using closed_Inter by (rule hull_eq)
huffman@44519
  1711
huffman@44519
  1712
lemma closure_closed [simp]: "closed S \<Longrightarrow> closure S = S"
huffman@44519
  1713
  unfolding closure_eq .
huffman@44519
  1714
huffman@44519
  1715
lemma closure_closure [simp]: "closure (closure S) = closure S"
huffman@44518
  1716
  unfolding closure_hull by (rule hull_hull)
himmelma@33175
  1717
huffman@44522
  1718
lemma closure_mono: "S \<subseteq> T \<Longrightarrow> closure S \<subseteq> closure T"
huffman@44518
  1719
  unfolding closure_hull by (rule hull_mono)
himmelma@33175
  1720
huffman@44519
  1721
lemma closure_minimal: "S \<subseteq> T \<Longrightarrow> closed T \<Longrightarrow> closure S \<subseteq> T"
huffman@44518
  1722
  unfolding closure_hull by (rule hull_minimal)
himmelma@33175
  1723
huffman@44519
  1724
lemma closure_unique:
wenzelm@53255
  1725
  assumes "S \<subseteq> T"
wenzelm@53255
  1726
    and "closed T"
wenzelm@53255
  1727
    and "\<And>T'. S \<subseteq> T' \<Longrightarrow> closed T' \<Longrightarrow> T \<subseteq> T'"
huffman@44519
  1728
  shows "closure S = T"
huffman@44519
  1729
  using assms unfolding closure_hull by (rule hull_unique)
huffman@44519
  1730
huffman@44519
  1731
lemma closure_empty [simp]: "closure {} = {}"
huffman@44518
  1732
  using closed_empty by (rule closure_closed)
himmelma@33175
  1733
huffman@44522
  1734
lemma closure_UNIV [simp]: "closure UNIV = UNIV"
huffman@44518
  1735
  using closed_UNIV by (rule closure_closed)
huffman@44518
  1736
huffman@44518
  1737
lemma closure_union [simp]: "closure (S \<union> T) = closure S \<union> closure T"
huffman@44518
  1738
  unfolding closure_interior by simp
himmelma@33175
  1739
lp15@60974
  1740
lemma closure_eq_empty [iff]: "closure S = {} \<longleftrightarrow> S = {}"
himmelma@33175
  1741
  using closure_empty closure_subset[of S]
himmelma@33175
  1742
  by blast
himmelma@33175
  1743
himmelma@33175
  1744
lemma closure_subset_eq: "closure S \<subseteq> S \<longleftrightarrow> closed S"
himmelma@33175
  1745
  using closure_eq[of S] closure_subset[of S]
himmelma@33175
  1746
  by simp
himmelma@33175
  1747
himmelma@33175
  1748
lemma open_inter_closure_eq_empty:
himmelma@33175
  1749
  "open S \<Longrightarrow> (S \<inter> closure T) = {} \<longleftrightarrow> S \<inter> T = {}"
huffman@34105
  1750
  using open_subset_interior[of S "- T"]
huffman@34105
  1751
  using interior_subset[of "- T"]
himmelma@33175
  1752
  unfolding closure_interior
himmelma@33175
  1753
  by auto
himmelma@33175
  1754
himmelma@33175
  1755
lemma open_inter_closure_subset:
himmelma@33175
  1756
  "open S \<Longrightarrow> (S \<inter> (closure T)) \<subseteq> closure(S \<inter> T)"
himmelma@33175
  1757
proof
himmelma@33175
  1758
  fix x
himmelma@33175
  1759
  assume as: "open S" "x \<in> S \<inter> closure T"
wenzelm@53255
  1760
  {
wenzelm@53282
  1761
    assume *: "x islimpt T"
himmelma@33175
  1762
    have "x islimpt (S \<inter> T)"
himmelma@33175
  1763
    proof (rule islimptI)
himmelma@33175
  1764
      fix A
himmelma@33175
  1765
      assume "x \<in> A" "open A"
himmelma@33175
  1766
      with as have "x \<in> A \<inter> S" "open (A \<inter> S)"
himmelma@33175
  1767
        by (simp_all add: open_Int)
himmelma@33175
  1768
      with * obtain y where "y \<in> T" "y \<in> A \<inter> S" "y \<noteq> x"
himmelma@33175
  1769
        by (rule islimptE)
wenzelm@53255
  1770
      then have "y \<in> S \<inter> T" "y \<in> A \<and> y \<noteq> x"
himmelma@33175
  1771
        by simp_all
wenzelm@53255
  1772
      then show "\<exists>y\<in>(S \<inter> T). y \<in> A \<and> y \<noteq> x" ..
himmelma@33175
  1773
    qed
himmelma@33175
  1774
  }
himmelma@33175
  1775
  then show "x \<in> closure (S \<inter> T)" using as
himmelma@33175
  1776
    unfolding closure_def
himmelma@33175
  1777
    by blast
himmelma@33175
  1778
qed
himmelma@33175
  1779
huffman@44519
  1780
lemma closure_complement: "closure (- S) = - interior S"
huffman@44518
  1781
  unfolding closure_interior by simp
himmelma@33175
  1782
huffman@44519
  1783
lemma interior_complement: "interior (- S) = - closure S"
huffman@44518
  1784
  unfolding closure_interior by simp
himmelma@33175
  1785
huffman@44365
  1786
lemma closure_Times: "closure (A \<times> B) = closure A \<times> closure B"
huffman@44519
  1787
proof (rule closure_unique)
huffman@44365
  1788
  show "A \<times> B \<subseteq> closure A \<times> closure B"
huffman@44365
  1789
    by (intro Sigma_mono closure_subset)
huffman@44365
  1790
  show "closed (closure A \<times> closure B)"
huffman@44365
  1791
    by (intro closed_Times closed_closure)
wenzelm@53282
  1792
  fix T
wenzelm@53282
  1793
  assume "A \<times> B \<subseteq> T" and "closed T"
wenzelm@53282
  1794
  then show "closure A \<times> closure B \<subseteq> T"
huffman@44365
  1795
    apply (simp add: closed_def open_prod_def, clarify)
huffman@44365
  1796
    apply (rule ccontr)
huffman@44365
  1797
    apply (drule_tac x="(a, b)" in bspec, simp, clarify, rename_tac C D)
huffman@44365
  1798
    apply (simp add: closure_interior interior_def)
huffman@44365
  1799
    apply (drule_tac x=C in spec)
huffman@44365
  1800
    apply (drule_tac x=D in spec)
huffman@44365
  1801
    apply auto
huffman@44365
  1802
    done
huffman@44365
  1803
qed
huffman@44365
  1804
hoelzl@51351
  1805
lemma islimpt_in_closure: "(x islimpt S) = (x:closure(S-{x}))"
hoelzl@51351
  1806
  unfolding closure_def using islimpt_punctured by blast
hoelzl@51351
  1807
lp15@61306
  1808
lemma connected_imp_connected_closure: "connected s \<Longrightarrow> connected (closure s)"
lp15@61306
  1809
    by (rule connectedI) (meson closure_subset open_Int open_inter_closure_eq_empty subset_trans connectedD)
lp15@61306
  1810
lp15@61306
  1811
lemma limpt_of_limpts:
lp15@61306
  1812
      fixes x :: "'a::metric_space"
lp15@61306
  1813
      shows "x islimpt {y. y islimpt s} \<Longrightarrow> x islimpt s"
lp15@61306
  1814
  apply (clarsimp simp add: islimpt_approachable)
lp15@61306
  1815
  apply (drule_tac x="e/2" in spec)
lp15@61306
  1816
  apply (auto simp: simp del: less_divide_eq_numeral1)
lp15@61306
  1817
  apply (drule_tac x="dist x' x" in spec)
lp15@61306
  1818
  apply (auto simp: zero_less_dist_iff simp del: less_divide_eq_numeral1)
lp15@61306
  1819
  apply (erule rev_bexI)
lp15@61306
  1820
  by (metis dist_commute dist_triangle_half_r less_trans less_irrefl)
lp15@61306
  1821
lp15@61306
  1822
lemma closed_limpts:  "closed {x::'a::metric_space. x islimpt s}"
lp15@61306
  1823
  using closed_limpt limpt_of_limpts by blast
lp15@61306
  1824
lp15@61306
  1825
lemma limpt_of_closure:
lp15@61306
  1826
      fixes x :: "'a::metric_space"
lp15@61306
  1827
      shows "x islimpt closure s \<longleftrightarrow> x islimpt s"
lp15@61306
  1828
  by (auto simp: closure_def islimpt_Un dest: limpt_of_limpts)
lp15@61306
  1829
lp15@61306
  1830
lemma closed_in_limpt:
lp15@61306
  1831
   "closedin (subtopology euclidean t) s \<longleftrightarrow> s \<subseteq> t \<and> (\<forall>x. x islimpt s \<and> x \<in> t \<longrightarrow> x \<in> s)"
lp15@61306
  1832
  apply (simp add: closedin_closed, safe)
lp15@61306
  1833
  apply (simp add: closed_limpt islimpt_subset)
lp15@61306
  1834
  apply (rule_tac x="closure s" in exI)
lp15@61306
  1835
  apply simp
lp15@61306
  1836
  apply (force simp: closure_def)
lp15@61306
  1837
  done
lp15@61306
  1838
paulson@61518
  1839
lemma closedin_closed_eq:
paulson@61518
  1840
    "closed s \<Longrightarrow> (closedin (subtopology euclidean s) t \<longleftrightarrow> closed t \<and> t \<subseteq> s)"
paulson@61518
  1841
  by (meson closed_in_limpt closed_subset closedin_closed_trans)
paulson@61518
  1842
eberlm@61531
  1843
lp15@61306
  1844
subsection\<open>Connected components, considered as a connectedness relation or a set\<close>
lp15@61306
  1845
lp15@61306
  1846
definition
lp15@61306
  1847
   "connected_component s x y \<equiv> \<exists>t. connected t \<and> t \<subseteq> s \<and> x \<in> t \<and> y \<in> t"
lp15@61306
  1848
lp15@61306
  1849
abbreviation
lp15@61306
  1850
   "connected_component_set s x \<equiv> Collect (connected_component s x)"
lp15@61306
  1851
lp15@61426
  1852
lemma connected_componentI:
lp15@61426
  1853
    "\<lbrakk>connected t; t \<subseteq> s; x \<in> t; y \<in> t\<rbrakk> \<Longrightarrow> connected_component s x y"
lp15@61426
  1854
  by (auto simp: connected_component_def)
lp15@61426
  1855
lp15@61306
  1856
lemma connected_component_in: "connected_component s x y \<Longrightarrow> x \<in> s \<and> y \<in> s"
lp15@61306
  1857
  by (auto simp: connected_component_def)
lp15@61306
  1858
lp15@61306
  1859
lemma connected_component_refl: "x \<in> s \<Longrightarrow> connected_component s x x"
lp15@61306
  1860
  apply (auto simp: connected_component_def)
lp15@61306
  1861
  using connected_sing by blast
lp15@61306
  1862
lp15@61306
  1863
lemma connected_component_refl_eq [simp]: "connected_component s x x \<longleftrightarrow> x \<in> s"
lp15@61306
  1864
  by (auto simp: connected_component_refl) (auto simp: connected_component_def)
lp15@61306
  1865
lp15@61306
  1866
lemma connected_component_sym: "connected_component s x y \<Longrightarrow> connected_component s y x"
lp15@61306
  1867
  by (auto simp: connected_component_def)
lp15@61306
  1868
lp15@61306
  1869
lemma connected_component_trans:
lp15@61306
  1870
    "\<lbrakk>connected_component s x y; connected_component s y z\<rbrakk> \<Longrightarrow> connected_component s x z"
lp15@61306
  1871
  unfolding connected_component_def
lp15@61306
  1872
  by (metis Int_iff Un_iff Un_subset_iff equals0D connected_Un)
lp15@61306
  1873
lp15@61306
  1874
lemma connected_component_of_subset: "\<lbrakk>connected_component s x y; s \<subseteq> t\<rbrakk> \<Longrightarrow> connected_component t x y"
lp15@61306
  1875
  by (auto simp: connected_component_def)
lp15@61306
  1876
lp15@61306
  1877
lemma connected_component_Union: "connected_component_set s x = Union {t. connected t \<and> x \<in> t \<and> t \<subseteq> s}"
lp15@61306
  1878
  by (auto simp: connected_component_def)
lp15@61306
  1879
lp15@61306
  1880
lemma connected_connected_component [iff]: "connected (connected_component_set s x)"
lp15@61306
  1881
  by (auto simp: connected_component_Union intro: connected_Union)
lp15@61306
  1882
lp15@61306
  1883
lemma connected_iff_eq_connected_component_set: "connected s \<longleftrightarrow> (\<forall>x \<in> s. connected_component_set s x = s)"
lp15@61306
  1884
proof (cases "s={}")
lp15@61306
  1885
  case True then show ?thesis by simp
lp15@61306
  1886
next
lp15@61306
  1887
  case False
lp15@61306
  1888
  then obtain x where "x \<in> s" by auto
lp15@61306
  1889
  show ?thesis
lp15@61306
  1890
  proof
lp15@61306
  1891
    assume "connected s"
lp15@61306
  1892
    then show "\<forall>x \<in> s. connected_component_set s x = s"
lp15@61306
  1893
      by (force simp: connected_component_def)
lp15@61306
  1894
  next
lp15@61306
  1895
    assume "\<forall>x \<in> s. connected_component_set s x = s"
lp15@61306
  1896
    then show "connected s"
lp15@61306
  1897
      by (metis `x \<in> s` connected_connected_component)
lp15@61306
  1898
  qed
lp15@61306
  1899
qed
lp15@61306
  1900
lp15@61306
  1901
lemma connected_component_subset: "connected_component_set s x \<subseteq> s"
lp15@61306
  1902
  using connected_component_in by blast
lp15@61306
  1903
lp15@61306
  1904
lemma connected_component_eq_self: "\<lbrakk>connected s; x \<in> s\<rbrakk> \<Longrightarrow> connected_component_set s x = s"
lp15@61306
  1905
  by (simp add: connected_iff_eq_connected_component_set)
lp15@61306
  1906
lp15@61306
  1907
lemma connected_iff_connected_component:
lp15@61306
  1908
    "connected s \<longleftrightarrow> (\<forall>x \<in> s. \<forall>y \<in> s. connected_component s x y)"
lp15@61306
  1909
  using connected_component_in by (auto simp: connected_iff_eq_connected_component_set)
lp15@61306
  1910
lp15@61306
  1911
lemma connected_component_maximal:
lp15@61306
  1912
    "\<lbrakk>x \<in> t; connected t; t \<subseteq> s\<rbrakk> \<Longrightarrow> t \<subseteq> (connected_component_set s x)"
lp15@61306
  1913
  using connected_component_eq_self connected_component_of_subset by blast
lp15@61306
  1914
lp15@61306
  1915
lemma connected_component_mono:
lp15@61306
  1916
    "s \<subseteq> t \<Longrightarrow> (connected_component_set s x) \<subseteq> (connected_component_set t x)"
lp15@61306
  1917
  by (simp add: Collect_mono connected_component_of_subset)
lp15@61306
  1918
lp15@61306
  1919
lemma connected_component_eq_empty [simp]: "connected_component_set s x = {} \<longleftrightarrow> (x \<notin> s)"
lp15@61306
  1920
  using connected_component_refl by (fastforce simp: connected_component_in)
lp15@61306
  1921
lp15@61306
  1922
lemma connected_component_set_empty [simp]: "connected_component_set {} x = {}"
lp15@61306
  1923
  using connected_component_eq_empty by blast
lp15@61306
  1924
lp15@61306
  1925
lemma connected_component_eq:
lp15@61306
  1926
    "y \<in> connected_component_set s x
lp15@61306
  1927
     \<Longrightarrow> (connected_component_set s y = connected_component_set s x)"
lp15@61306
  1928
  by (metis (no_types, lifting) Collect_cong connected_component_sym connected_component_trans mem_Collect_eq)
lp15@61306
  1929
lp15@61306
  1930
lemma closed_connected_component:
lp15@61306
  1931
  assumes s: "closed s" shows "closed (connected_component_set s x)"
lp15@61306
  1932
proof (cases "x \<in> s")
lp15@61306
  1933
  case False then show ?thesis
lp15@61306
  1934
    by (metis connected_component_eq_empty closed_empty)
lp15@61306
  1935
next
lp15@61306
  1936
  case True
lp15@61306
  1937
  show ?thesis
lp15@61306
  1938
    unfolding closure_eq [symmetric]
lp15@61306
  1939
    proof
lp15@61306
  1940
      show "closure (connected_component_set s x) \<subseteq> connected_component_set s x"
lp15@61306
  1941
        apply (rule connected_component_maximal)
lp15@61306
  1942
        apply (simp add: closure_def True)
lp15@61306
  1943
        apply (simp add: connected_imp_connected_closure)
lp15@61306
  1944
        apply (simp add: s closure_minimal connected_component_subset)
lp15@61306
  1945
        done
lp15@61306
  1946
    next
lp15@61306
  1947
      show "connected_component_set s x \<subseteq> closure (connected_component_set s x)"
lp15@61306
  1948
        by (simp add: closure_subset)
lp15@61306
  1949
  qed
lp15@61306
  1950
qed
lp15@61306
  1951
lp15@61306
  1952
lemma connected_component_disjoint:
lp15@61306
  1953
    "(connected_component_set s a) \<inter> (connected_component_set s b) = {} \<longleftrightarrow>
lp15@61306
  1954
     a \<notin> connected_component_set s b"
lp15@61306
  1955
apply (auto simp: connected_component_eq)
lp15@61306
  1956
using connected_component_eq connected_component_sym by blast
lp15@61306
  1957
lp15@61306
  1958
lemma connected_component_nonoverlap:
lp15@61306
  1959
    "(connected_component_set s a) \<inter> (connected_component_set s b) = {} \<longleftrightarrow>
lp15@61306
  1960
     (a \<notin> s \<or> b \<notin> s \<or> connected_component_set s a \<noteq> connected_component_set s b)"
lp15@61306
  1961
  apply (auto simp: connected_component_in)
lp15@61306
  1962
  using connected_component_refl_eq apply blast
lp15@61306
  1963
  apply (metis connected_component_eq mem_Collect_eq)
lp15@61306
  1964
  apply (metis connected_component_eq mem_Collect_eq)
lp15@61306
  1965
  done
lp15@61306
  1966
lp15@61306
  1967
lemma connected_component_overlap:
lp15@61306
  1968
    "(connected_component_set s a \<inter> connected_component_set s b \<noteq> {}) =
lp15@61306
  1969
     (a \<in> s \<and> b \<in> s \<and> connected_component_set s a = connected_component_set s b)"
lp15@61306
  1970
  by (auto simp: connected_component_nonoverlap)
lp15@61306
  1971
lp15@61306
  1972
lemma connected_component_sym_eq: "connected_component s x y \<longleftrightarrow> connected_component s y x"
lp15@61306
  1973
  using connected_component_sym by blast
lp15@61306
  1974
lp15@61306
  1975
lemma connected_component_eq_eq:
lp15@61306
  1976
    "connected_component_set s x = connected_component_set s y \<longleftrightarrow>
lp15@61306
  1977
     x \<notin> s \<and> y \<notin> s \<or> x \<in> s \<and> y \<in> s \<and> connected_component s x y"
lp15@61306
  1978
  apply (case_tac "y \<in> s")
lp15@61306
  1979
   apply (simp add:)
lp15@61306
  1980
   apply (metis connected_component_eq connected_component_eq_empty connected_component_refl_eq mem_Collect_eq)
lp15@61306
  1981
  apply (case_tac "x \<in> s")
lp15@61306
  1982
   apply (simp add:)
lp15@61306
  1983
   apply (metis connected_component_eq_empty)
lp15@61306
  1984
  using connected_component_eq_empty by blast
lp15@61306
  1985
lp15@61306
  1986
lemma connected_iff_connected_component_eq:
lp15@61306
  1987
    "connected s \<longleftrightarrow>
lp15@61306
  1988
       (\<forall>x \<in> s. \<forall>y \<in> s. connected_component_set s x = connected_component_set s y)"
lp15@61306
  1989
  by (simp add: connected_component_eq_eq connected_iff_connected_component)
lp15@61306
  1990
lp15@61306
  1991
lemma connected_component_idemp:
lp15@61306
  1992
    "connected_component_set (connected_component_set s x) x = connected_component_set s x"
lp15@61306
  1993
apply (rule subset_antisym)
lp15@61306
  1994
apply (simp add: connected_component_subset)
lp15@61306
  1995
by (metis connected_component_eq_empty connected_component_maximal connected_component_refl_eq connected_connected_component mem_Collect_eq set_eq_subset)
lp15@61306
  1996
lp15@61306
  1997
lemma connected_component_unique:
lp15@61306
  1998
  "\<lbrakk>x \<in> c; c \<subseteq> s; connected c;
lp15@61306
  1999
    \<And>c'. x \<in> c' \<and> c' \<subseteq> s \<and> connected c'
lp15@61306
  2000
              \<Longrightarrow> c' \<subseteq> c\<rbrakk>
lp15@61306
  2001
        \<Longrightarrow> connected_component_set s x = c"
lp15@61306
  2002
apply (rule subset_antisym)
lp15@61306
  2003
apply (meson connected_component_maximal connected_component_subset connected_connected_component contra_subsetD)
lp15@61306
  2004
by (simp add: connected_component_maximal)
lp15@61306
  2005
lp15@61306
  2006
lemma joinable_connected_component_eq:
lp15@61306
  2007
  "\<lbrakk>connected t; t \<subseteq> s;
lp15@61306
  2008
    connected_component_set s x \<inter> t \<noteq> {};
lp15@61306
  2009
    connected_component_set s y \<inter> t \<noteq> {}\<rbrakk>
lp15@61306
  2010
    \<Longrightarrow> connected_component_set s x = connected_component_set s y"
lp15@61306
  2011
apply (simp add: ex_in_conv [symmetric])
lp15@61306
  2012
apply (rule connected_component_eq)
lp15@61306
  2013
by (metis (no_types, hide_lams) connected_component_eq_eq connected_component_in connected_component_maximal subsetD mem_Collect_eq)
lp15@61306
  2014
lp15@61306
  2015
lp15@61306
  2016
lemma Union_connected_component: "Union (connected_component_set s ` s) = s"
lp15@61306
  2017
  apply (rule subset_antisym)
lp15@61306
  2018
  apply (simp add: SUP_least connected_component_subset)
lp15@61306
  2019
  using connected_component_refl_eq
lp15@61306
  2020
  by force
lp15@61306
  2021
lp15@61306
  2022
lp15@61306
  2023
lemma complement_connected_component_unions:
lp15@61306
  2024
    "s - connected_component_set s x =
lp15@61306
  2025
     Union (connected_component_set s ` s - {connected_component_set s x})"
lp15@61306
  2026
  apply (subst Union_connected_component [symmetric], auto)
lp15@61306
  2027
  apply (metis connected_component_eq_eq connected_component_in)
lp15@61306
  2028
  by (metis connected_component_eq mem_Collect_eq)
lp15@61306
  2029
lp15@61306
  2030
lemma connected_component_intermediate_subset:
lp15@61306
  2031
        "\<lbrakk>connected_component_set u a \<subseteq> t; t \<subseteq> u\<rbrakk>
lp15@61306
  2032
        \<Longrightarrow> connected_component_set t a = connected_component_set u a"
lp15@61306
  2033
  apply (case_tac "a \<in> u")
lp15@61306
  2034
  apply (simp add: connected_component_maximal connected_component_mono subset_antisym)
lp15@61306
  2035
  using connected_component_eq_empty by blast
lp15@61306
  2036
lp15@61306
  2037
subsection\<open>The set of connected components of a set\<close>
lp15@61306
  2038
lp15@61306
  2039
definition components:: "'a::topological_space set \<Rightarrow> 'a set set" where
lp15@61306
  2040
  "components s \<equiv> connected_component_set s ` s"
lp15@61306
  2041
lp15@61306
  2042
lemma components_iff: "s \<in> components u \<longleftrightarrow> (\<exists>x. x \<in> u \<and> s = connected_component_set u x)"
lp15@61306
  2043
  by (auto simp: components_def)
lp15@61306
  2044
lp15@61306
  2045
lemma Union_components: "u = Union (components u)"
lp15@61306
  2046
  apply (rule subset_antisym)
lp15@61306
  2047
  apply (metis Union_connected_component components_def set_eq_subset)
lp15@61306
  2048
  using Union_connected_component components_def by fastforce
lp15@61306
  2049
lp15@61306
  2050
lemma pairwise_disjoint_components: "pairwise (\<lambda>X Y. X \<inter> Y = {}) (components u)"
lp15@61306
  2051
  apply (simp add: pairwise_def)
lp15@61306
  2052
  apply (auto simp: components_iff)
lp15@61306
  2053
  apply (metis connected_component_eq_eq connected_component_in)+
lp15@61306
  2054
  done
lp15@61306
  2055
lp15@61306
  2056
lemma in_components_nonempty: "c \<in> components s \<Longrightarrow> c \<noteq> {}"
lp15@61306
  2057
    by (metis components_iff connected_component_eq_empty)
lp15@61306
  2058
lp15@61306
  2059
lemma in_components_subset: "c \<in> components s \<Longrightarrow> c \<subseteq> s"
lp15@61306
  2060
  using Union_components by blast
lp15@61306
  2061
lp15@61306
  2062
lemma in_components_connected: "c \<in> components s \<Longrightarrow> connected c"
lp15@61306
  2063
  by (metis components_iff connected_connected_component)
lp15@61306
  2064
lp15@61306
  2065
lemma in_components_maximal:
lp15@61306
  2066
     "c \<in> components s \<longleftrightarrow>
lp15@61306
  2067
      (c \<noteq> {} \<and> c \<subseteq> s \<and> connected c \<and> (\<forall>d. d \<noteq> {} \<and> c \<subseteq> d \<and> d \<subseteq> s \<and> connected d \<longrightarrow> d = c))"
lp15@61306
  2068
  apply (rule iffI)
lp15@61306
  2069
  apply (simp add: in_components_nonempty in_components_connected)
lp15@61306
  2070
  apply (metis (full_types) components_iff connected_component_eq_self connected_component_intermediate_subset connected_component_refl in_components_subset mem_Collect_eq rev_subsetD)
lp15@61306
  2071
  by (metis bot.extremum_uniqueI components_iff connected_component_eq_empty connected_component_maximal connected_component_subset connected_connected_component subset_emptyI)
lp15@61306
  2072
lp15@61306
  2073
lemma joinable_components_eq:
lp15@61306
  2074
    "connected t \<and> t \<subseteq> s \<and> c1 \<in> components s \<and> c2 \<in> components s \<and> c1 \<inter> t \<noteq> {} \<and> c2 \<inter> t \<noteq> {} \<Longrightarrow> c1 = c2"
lp15@61306
  2075
  by (metis (full_types) components_iff joinable_connected_component_eq)
lp15@61306
  2076
lp15@61306
  2077
lemma closed_components: "\<lbrakk>closed s; c \<in> components s\<rbrakk> \<Longrightarrow> closed c"
lp15@61306
  2078
  by (metis closed_connected_component components_iff)
lp15@61306
  2079
lp15@61306
  2080
lemma components_nonoverlap:
lp15@61306
  2081
    "\<lbrakk>c \<in> components s; c' \<in> components s\<rbrakk> \<Longrightarrow> (c \<inter> c' = {}) \<longleftrightarrow> (c \<noteq> c')"
lp15@61306
  2082
  apply (auto simp: in_components_nonempty components_iff)
lp15@61306
  2083
    using connected_component_refl apply blast
lp15@61306
  2084
   apply (metis connected_component_eq_eq connected_component_in)
lp15@61306
  2085
  by (metis connected_component_eq mem_Collect_eq)
lp15@61306
  2086
lp15@61306
  2087
lemma components_eq: "\<lbrakk>c \<in> components s; c' \<in> components s\<rbrakk> \<Longrightarrow> (c = c' \<longleftrightarrow> c \<inter> c' \<noteq> {})"
lp15@61306
  2088
  by (metis components_nonoverlap)
lp15@61306
  2089
lp15@61306
  2090
lemma components_eq_empty [simp]: "components s = {} \<longleftrightarrow> s = {}"
lp15@61306
  2091
  by (simp add: components_def)
lp15@61306
  2092
lp15@61306
  2093
lemma components_empty [simp]: "components {} = {}"
lp15@61306
  2094
  by simp
lp15@61306
  2095
lp15@61306
  2096
lemma connected_eq_connected_components_eq: "connected s \<longleftrightarrow> (\<forall>c \<in> components s. \<forall>c' \<in> components s. c = c')"
lp15@61306
  2097
  by (metis (no_types, hide_lams) components_iff connected_component_eq_eq connected_iff_connected_component)
lp15@61306
  2098
lp15@61306
  2099
lemma components_eq_sing_iff: "components s = {s} \<longleftrightarrow> connected s \<and> s \<noteq> {}"
lp15@61306
  2100
  apply (rule iffI)
lp15@61306
  2101
   using in_components_connected apply fastforce
lp15@61306
  2102
  apply safe
lp15@61306
  2103
    using Union_components apply fastforce
lp15@61306
  2104
   apply (metis components_iff connected_component_eq_self)
lp15@61306
  2105
  using in_components_maximal by auto
lp15@61306
  2106
lp15@61306
  2107
lemma components_eq_sing_exists: "(\<exists>a. components s = {a}) \<longleftrightarrow> connected s \<and> s \<noteq> {}"
lp15@61306
  2108
  apply (rule iffI)
lp15@61306
  2109
   using connected_eq_connected_components_eq apply fastforce
lp15@61306
  2110
  by (metis components_eq_sing_iff)
lp15@61306
  2111
lp15@61306
  2112
lemma connected_eq_components_subset_sing: "connected s \<longleftrightarrow> components s \<subseteq> {s}"
lp15@61306
  2113
  by (metis Union_components components_empty components_eq_sing_iff connected_empty insert_subset order_refl subset_singletonD)
lp15@61306
  2114
lp15@61306
  2115
lemma connected_eq_components_subset_sing_exists: "connected s \<longleftrightarrow> (\<exists>a. components s \<subseteq> {a})"
lp15@61306
  2116
  by (metis components_eq_sing_exists connected_eq_components_subset_sing empty_iff subset_iff subset_singletonD)
lp15@61306
  2117
lp15@61306
  2118
lemma in_components_self: "s \<in> components s \<longleftrightarrow> connected s \<and> s \<noteq> {}"
lp15@61306
  2119
  by (metis components_empty components_eq_sing_iff empty_iff in_components_connected insertI1)
lp15@61306
  2120
lp15@61306
  2121
lemma components_maximal: "\<lbrakk>c \<in> components s; connected t; t \<subseteq> s; c \<inter> t \<noteq> {}\<rbrakk> \<Longrightarrow> t \<subseteq> c"
lp15@61306
  2122
  apply (simp add: components_def ex_in_conv [symmetric], clarify)
lp15@61306
  2123
  by (meson connected_component_def connected_component_trans)
lp15@61306
  2124
lp15@61306
  2125
lemma exists_component_superset: "\<lbrakk>t \<subseteq> s; s \<noteq> {}; connected t\<rbrakk> \<Longrightarrow> \<exists>c. c \<in> components s \<and> t \<subseteq> c"
lp15@61306
  2126
  apply (case_tac "t = {}")
lp15@61306
  2127
   apply force
lp15@61306
  2128
  by (metis components_def ex_in_conv connected_component_maximal contra_subsetD image_eqI)
lp15@61306
  2129
lp15@61306
  2130
lemma components_intermediate_subset: "\<lbrakk>s \<in> components u; s \<subseteq> t; t \<subseteq> u\<rbrakk> \<Longrightarrow> s \<in> components t"
lp15@61306
  2131
  apply (auto simp: components_iff)
lp15@61306
  2132
  by (metis connected_component_eq_empty connected_component_intermediate_subset)
lp15@61306
  2133
lp15@61306
  2134
lemma in_components_unions_complement: "c \<in> components s \<Longrightarrow> s - c = Union(components s - {c})"
lp15@61306
  2135
  by (metis complement_connected_component_unions components_def components_iff)
lp15@61306
  2136
lp15@61306
  2137
lemma connected_intermediate_closure:
lp15@61306
  2138
  assumes cs: "connected s" and st: "s \<subseteq> t" and ts: "t \<subseteq> closure s"
lp15@61306
  2139
    shows "connected t"
lp15@61306
  2140
proof (rule connectedI)
lp15@61306
  2141
  fix A B
lp15@61306
  2142
  assume A: "open A" and B: "open B" and Alap: "A \<inter> t \<noteq> {}" and Blap: "B \<inter> t \<noteq> {}"
lp15@61306
  2143
     and disj: "A \<inter> B \<inter> t = {}" and cover: "t \<subseteq> A \<union> B"
lp15@61306
  2144
  have disjs: "A \<inter> B \<inter> s = {}"
lp15@61306
  2145
    using disj st by auto
lp15@61306
  2146
  have "A \<inter> closure s \<noteq> {}"
lp15@61306
  2147
    using Alap Int_absorb1 ts by blast
lp15@61306
  2148
  then have Alaps: "A \<inter> s \<noteq> {}"
lp15@61306
  2149
    by (simp add: A open_inter_closure_eq_empty)
lp15@61306
  2150
  have "B \<inter> closure s \<noteq> {}"
lp15@61306
  2151
    using Blap Int_absorb1 ts by blast
lp15@61306
  2152
  then have Blaps: "B \<inter> s \<noteq> {}"
lp15@61306
  2153
    by (simp add: B open_inter_closure_eq_empty)
lp15@61306
  2154
  then show False
lp15@61306
  2155
    using cs [unfolded connected_def] A B disjs Alaps Blaps cover st
lp15@61306
  2156
    by blast
lp15@61306
  2157
qed
lp15@61306
  2158
lp15@61306
  2159
lemma closed_in_connected_component: "closedin (subtopology euclidean s) (connected_component_set s x)"
lp15@61306
  2160
proof (cases "connected_component_set s x = {}")
lp15@61609
  2161
  case True then show ?thesis
lp15@61306
  2162
    by (metis closedin_empty)
lp15@61306
  2163
next
lp15@61306
  2164
  case False
lp15@61306
  2165
  then obtain y where y: "connected_component s x y"
lp15@61306
  2166
    by blast
lp15@61306
  2167
  have 1: "connected_component_set s x \<subseteq> s \<inter> closure (connected_component_set s x)"
lp15@61306
  2168
    by (auto simp: closure_def connected_component_in)
lp15@61306
  2169
  have 2: "connected_component s x y \<Longrightarrow> s \<inter> closure (connected_component_set s x) \<subseteq> connected_component_set s x"
lp15@61306
  2170
    apply (rule connected_component_maximal)
lp15@61306
  2171
    apply (simp add:)
lp15@61306
  2172
    using closure_subset connected_component_in apply fastforce
lp15@61306
  2173
    using "1" connected_intermediate_closure apply blast+
lp15@61306
  2174
    done
lp15@61306
  2175
  show ?thesis using y
lp15@61306
  2176
    apply (simp add: Topology_Euclidean_Space.closedin_closed)
lp15@61306
  2177
    using 1 2 by auto
lp15@61306
  2178
qed
hoelzl@51351
  2179
wenzelm@60420
  2180
subsection \<open>Frontier (aka boundary)\<close>
himmelma@33175
  2181
himmelma@33175
  2182
definition "frontier S = closure S - interior S"
himmelma@33175
  2183
wenzelm@53255
  2184
lemma frontier_closed: "closed (frontier S)"
himmelma@33175
  2185
  by (simp add: frontier_def closed_Diff)
himmelma@33175
  2186
huffman@34105
  2187
lemma frontier_closures: "frontier S = (closure S) \<inter> (closure(- S))"
himmelma@33175
  2188
  by (auto simp add: frontier_def interior_closure)
himmelma@33175
  2189
himmelma@33175
  2190
lemma frontier_straddle:
himmelma@33175
  2191
  fixes a :: "'a::metric_space"
huffman@44909
  2192
  shows "a \<in> frontier S \<longleftrightarrow> (\<forall>e>0. (\<exists>x\<in>S. dist a x < e) \<and> (\<exists>x. x \<notin> S \<and> dist a x < e))"
huffman@44909
  2193
  unfolding frontier_def closure_interior
huffman@44909
  2194
  by (auto simp add: mem_interior subset_eq ball_def)
himmelma@33175
  2195
himmelma@33175
  2196
lemma frontier_subset_closed: "closed S \<Longrightarrow> frontier S \<subseteq> S"
himmelma@33175
  2197
  by (metis frontier_def closure_closed Diff_subset)
himmelma@33175
  2198
hoelzl@34964
  2199
lemma frontier_empty[simp]: "frontier {} = {}"
huffman@36362
  2200
  by (simp add: frontier_def)
himmelma@33175
  2201
himmelma@33175
  2202
lemma frontier_subset_eq: "frontier S \<subseteq> S \<longleftrightarrow> closed S"
wenzelm@58757
  2203
proof -
wenzelm@53255
  2204
  {
wenzelm@53255
  2205
    assume "frontier S \<subseteq> S"
wenzelm@53255
  2206
    then have "closure S \<subseteq> S"
wenzelm@53255
  2207
      using interior_subset unfolding frontier_def by auto
wenzelm@53255
  2208
    then have "closed S"
wenzelm@53255
  2209
      using closure_subset_eq by auto
himmelma@33175
  2210
  }
wenzelm@53255
  2211
  then show ?thesis using frontier_subset_closed[of S] ..
himmelma@33175
  2212
qed
himmelma@33175
  2213
paulson@61518
  2214
lemma frontier_complement  [simp]: "frontier (- S) = frontier S"
himmelma@33175
  2215
  by (auto simp add: frontier_def closure_complement interior_complement)
himmelma@33175
  2216
himmelma@33175
  2217
lemma frontier_disjoint_eq: "frontier S \<inter> S = {} \<longleftrightarrow> open S"
huffman@34105
  2218
  using frontier_complement frontier_subset_eq[of "- S"]
huffman@34105
  2219
  unfolding open_closed by auto
himmelma@33175
  2220
wenzelm@58757
  2221
wenzelm@60420
  2222
subsection \<open>Filters and the ``eventually true'' quantifier\<close>
huffman@44081
  2223
wenzelm@52624
  2224
definition indirection :: "'a::real_normed_vector \<Rightarrow> 'a \<Rightarrow> 'a filter"
wenzelm@52624
  2225
    (infixr "indirection" 70)
wenzelm@52624
  2226
  where "a indirection v = at a within {b. \<exists>c\<ge>0. b - a = scaleR c v}"
himmelma@33175
  2227
wenzelm@60420
  2228
text \<open>Identify Trivial limits, where we can't approach arbitrarily closely.\<close>
himmelma@33175
  2229
wenzelm@52624
  2230
lemma trivial_limit_within: "trivial_limit (at a within S) \<longleftrightarrow> \<not> a islimpt S"
himmelma@33175
  2231
proof
himmelma@33175
  2232
  assume "trivial_limit (at a within S)"
wenzelm@53255
  2233
  then show "\<not> a islimpt S"
himmelma@33175
  2234
    unfolding trivial_limit_def