src/HOL/Analysis/Path_Connected.thy

tidied up HOL/ex/Primrec

+
−(*  Title:      HOL/Analysis/Path_Connected.thy
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−    Authors:    LC Paulson and Robert Himmelmann (TU Muenchen), based on material from HOL Light
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−*)
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−
+
−section \<open>Path-Connectedness\<close>
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−
+
−theory Path_Connected
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−  imports Starlike
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−begin
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−
+
−subsection \<open>Paths and Arcs\<close>
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−
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−definition%important path :: "(real \<Rightarrow> 'a::topological_space) \<Rightarrow> bool"
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−  where "path g \<longleftrightarrow> continuous_on {0..1} g"
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−
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−definition%important pathstart :: "(real \<Rightarrow> 'a::topological_space) \<Rightarrow> 'a"
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−  where "pathstart g = g 0"
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−
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−definition%important pathfinish :: "(real \<Rightarrow> 'a::topological_space) \<Rightarrow> 'a"
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−  where "pathfinish g = g 1"
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−
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−definition%important path_image :: "(real \<Rightarrow> 'a::topological_space) \<Rightarrow> 'a set"
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−  where "path_image g = g ` {0 .. 1}"
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−
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−definition%important reversepath :: "(real \<Rightarrow> 'a::topological_space) \<Rightarrow> real \<Rightarrow> 'a"
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−  where "reversepath g = (\<lambda>x. g(1 - x))"
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−
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−definition%important joinpaths :: "(real \<Rightarrow> 'a::topological_space) \<Rightarrow> (real \<Rightarrow> 'a) \<Rightarrow> real \<Rightarrow> 'a"
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−    (infixr "+++" 75)
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−  where "g1 +++ g2 = (\<lambda>x. if x \<le> 1/2 then g1 (2 * x) else g2 (2 * x - 1))"
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−
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−definition%important simple_path :: "(real \<Rightarrow> 'a::topological_space) \<Rightarrow> bool"
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−  where "simple_path g \<longleftrightarrow>
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−     path g \<and> (\<forall>x\<in>{0..1}. \<forall>y\<in>{0..1}. g x = g y \<longrightarrow> x = y \<or> x = 0 \<and> y = 1 \<or> x = 1 \<and> y = 0)"
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−
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−definition%important arc :: "(real \<Rightarrow> 'a :: topological_space) \<Rightarrow> bool"
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−  where "arc g \<longleftrightarrow> path g \<and> inj_on g {0..1}"
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−
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−
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−subsection%unimportant\<open>Invariance theorems\<close>
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−
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−lemma path_eq: "path p \<Longrightarrow> (\<And>t. t \<in> {0..1} \<Longrightarrow> p t = q t) \<Longrightarrow> path q"
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−  using continuous_on_eq path_def by blast
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−
+
−lemma path_continuous_image: "path g \<Longrightarrow> continuous_on (path_image g) f \<Longrightarrow> path(f \<circ> g)"
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−  unfolding path_def path_image_def
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−  using continuous_on_compose by blast
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−
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−lemma path_translation_eq:
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−  fixes g :: "real \<Rightarrow> 'a :: real_normed_vector"
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−  shows "path((\<lambda>x. a + x) \<circ> g) = path g"
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−proof -
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−  have g: "g = (\<lambda>x. -a + x) \<circ> ((\<lambda>x. a + x) \<circ> g)"
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−    by (rule ext) simp
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−  show ?thesis
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−    unfolding path_def
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−    apply safe
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−    apply (subst g)
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−    apply (rule continuous_on_compose)
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−    apply (auto intro: continuous_intros)
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−    done
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−qed
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−
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−lemma path_linear_image_eq:
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−  fixes f :: "'a::euclidean_space \<Rightarrow> 'b::euclidean_space"
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−   assumes "linear f" "inj f"
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−     shows "path(f \<circ> g) = path g"
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−proof -
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−  from linear_injective_left_inverse [OF assms]
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−  obtain h where h: "linear h" "h \<circ> f = id"
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−    by blast
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−  then have g: "g = h \<circ> (f \<circ> g)"
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−    by (metis comp_assoc id_comp)
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−  show ?thesis
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−    unfolding path_def
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−    using h assms
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−    by (metis g continuous_on_compose linear_continuous_on linear_conv_bounded_linear)
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−qed
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−
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−lemma pathstart_translation: "pathstart((\<lambda>x. a + x) \<circ> g) = a + pathstart g"
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−  by (simp add: pathstart_def)
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−
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−lemma pathstart_linear_image_eq: "linear f \<Longrightarrow> pathstart(f \<circ> g) = f(pathstart g)"
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−  by (simp add: pathstart_def)
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−
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−lemma pathfinish_translation: "pathfinish((\<lambda>x. a + x) \<circ> g) = a + pathfinish g"
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−  by (simp add: pathfinish_def)
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−
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−lemma pathfinish_linear_image: "linear f \<Longrightarrow> pathfinish(f \<circ> g) = f(pathfinish g)"
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−  by (simp add: pathfinish_def)
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−
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−lemma path_image_translation: "path_image((\<lambda>x. a + x) \<circ> g) = (\<lambda>x. a + x) ` (path_image g)"
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−  by (simp add: image_comp path_image_def)
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−
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−lemma path_image_linear_image: "linear f \<Longrightarrow> path_image(f \<circ> g) = f ` (path_image g)"
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−  by (simp add: image_comp path_image_def)
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−
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−lemma reversepath_translation: "reversepath((\<lambda>x. a + x) \<circ> g) = (\<lambda>x. a + x) \<circ> reversepath g"
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−  by (rule ext) (simp add: reversepath_def)
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−
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−lemma reversepath_linear_image: "linear f \<Longrightarrow> reversepath(f \<circ> g) = f \<circ> reversepath g"
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−  by (rule ext) (simp add: reversepath_def)
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−
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−lemma joinpaths_translation:
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−    "((\<lambda>x. a + x) \<circ> g1) +++ ((\<lambda>x. a + x) \<circ> g2) = (\<lambda>x. a + x) \<circ> (g1 +++ g2)"
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−  by (rule ext) (simp add: joinpaths_def)
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−
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−lemma joinpaths_linear_image: "linear f \<Longrightarrow> (f \<circ> g1) +++ (f \<circ> g2) = f \<circ> (g1 +++ g2)"
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−  by (rule ext) (simp add: joinpaths_def)
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−
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−lemma simple_path_translation_eq:
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−  fixes g :: "real \<Rightarrow> 'a::euclidean_space"
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−  shows "simple_path((\<lambda>x. a + x) \<circ> g) = simple_path g"
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−  by (simp add: simple_path_def path_translation_eq)
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−
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−lemma simple_path_linear_image_eq:
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−  fixes f :: "'a::euclidean_space \<Rightarrow> 'b::euclidean_space"
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−  assumes "linear f" "inj f"
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−    shows "simple_path(f \<circ> g) = simple_path g"
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−  using assms inj_on_eq_iff [of f]
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−  by (auto simp: path_linear_image_eq simple_path_def path_translation_eq)
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−
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−lemma arc_translation_eq:
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−  fixes g :: "real \<Rightarrow> 'a::euclidean_space"
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−  shows "arc((\<lambda>x. a + x) \<circ> g) = arc g"
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−  by (auto simp: arc_def inj_on_def path_translation_eq)
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−
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−lemma arc_linear_image_eq:
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−  fixes f :: "'a::euclidean_space \<Rightarrow> 'b::euclidean_space"
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−   assumes "linear f" "inj f"
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−     shows  "arc(f \<circ> g) = arc g"
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−  using assms inj_on_eq_iff [of f]
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−  by (auto simp: arc_def inj_on_def path_linear_image_eq)
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−
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−
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−subsection%unimportant\<open>Basic lemmas about paths\<close>
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−
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−lemma continuous_on_path: "path f \<Longrightarrow> t \<subseteq> {0..1} \<Longrightarrow> continuous_on t f"
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−  using continuous_on_subset path_def by blast
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−
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−lemma arc_imp_simple_path: "arc g \<Longrightarrow> simple_path g"
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−  by (simp add: arc_def inj_on_def simple_path_def)
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−
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−lemma arc_imp_path: "arc g \<Longrightarrow> path g"
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−  using arc_def by blast
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−
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−lemma arc_imp_inj_on: "arc g \<Longrightarrow> inj_on g {0..1}"
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−  by (auto simp: arc_def)
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−
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−lemma simple_path_imp_path: "simple_path g \<Longrightarrow> path g"
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−  using simple_path_def by blast
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−
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−lemma simple_path_cases: "simple_path g \<Longrightarrow> arc g \<or> pathfinish g = pathstart g"
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−  unfolding simple_path_def arc_def inj_on_def pathfinish_def pathstart_def
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−  by force
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−
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−lemma simple_path_imp_arc: "simple_path g \<Longrightarrow> pathfinish g \<noteq> pathstart g \<Longrightarrow> arc g"
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−  using simple_path_cases by auto
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−
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−lemma arc_distinct_ends: "arc g \<Longrightarrow> pathfinish g \<noteq> pathstart g"
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−  unfolding arc_def inj_on_def pathfinish_def pathstart_def
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−  by fastforce
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−
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−lemma arc_simple_path: "arc g \<longleftrightarrow> simple_path g \<and> pathfinish g \<noteq> pathstart g"
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−  using arc_distinct_ends arc_imp_simple_path simple_path_cases by blast
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−
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−lemma simple_path_eq_arc: "pathfinish g \<noteq> pathstart g \<Longrightarrow> (simple_path g = arc g)"
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−  by (simp add: arc_simple_path)
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−
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−lemma path_image_const [simp]: "path_image (\<lambda>t. a) = {a}"
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−  by (force simp: path_image_def)
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−
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−lemma path_image_nonempty [simp]: "path_image g \<noteq> {}"
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−  unfolding path_image_def image_is_empty box_eq_empty
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−  by auto
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−
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−lemma pathstart_in_path_image[intro]: "pathstart g \<in> path_image g"
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−  unfolding pathstart_def path_image_def
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−  by auto
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−
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−lemma pathfinish_in_path_image[intro]: "pathfinish g \<in> path_image g"
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−  unfolding pathfinish_def path_image_def
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−  by auto
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−
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−lemma connected_path_image[intro]: "path g \<Longrightarrow> connected (path_image g)"
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−  unfolding path_def path_image_def
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−  using connected_continuous_image connected_Icc by blast
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−
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−lemma compact_path_image[intro]: "path g \<Longrightarrow> compact (path_image g)"
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−  unfolding path_def path_image_def
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−  using compact_continuous_image connected_Icc by blast
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−
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−lemma reversepath_reversepath[simp]: "reversepath (reversepath g) = g"
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−  unfolding reversepath_def
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−  by auto
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−
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−lemma pathstart_reversepath[simp]: "pathstart (reversepath g) = pathfinish g"
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−  unfolding pathstart_def reversepath_def pathfinish_def
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−  by auto
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−
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−lemma pathfinish_reversepath[simp]: "pathfinish (reversepath g) = pathstart g"
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−  unfolding pathstart_def reversepath_def pathfinish_def
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−  by auto
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−
+
−lemma pathstart_join[simp]: "pathstart (g1 +++ g2) = pathstart g1"
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−  unfolding pathstart_def joinpaths_def pathfinish_def
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−  by auto
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−
+
−lemma pathfinish_join[simp]: "pathfinish (g1 +++ g2) = pathfinish g2"
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−  unfolding pathstart_def joinpaths_def pathfinish_def
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−  by auto
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−
+
−lemma path_image_reversepath[simp]: "path_image (reversepath g) = path_image g"
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−proof -
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−  have *: "\<And>g. path_image (reversepath g) \<subseteq> path_image g"
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−    unfolding path_image_def subset_eq reversepath_def Ball_def image_iff
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−    by force
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−  show ?thesis
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−    using *[of g] *[of "reversepath g"]
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−    unfolding reversepath_reversepath
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−    by auto
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−qed
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−
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−lemma path_reversepath [simp]: "path (reversepath g) \<longleftrightarrow> path g"
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−proof -
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−  have *: "\<And>g. path g \<Longrightarrow> path (reversepath g)"
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−    unfolding path_def reversepath_def
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−    apply (rule continuous_on_compose[unfolded o_def, of _ "\<lambda>x. 1 - x"])
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−    apply (auto intro: continuous_intros continuous_on_subset[of "{0..1}"])
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−    done
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−  show ?thesis
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−    using *[of "reversepath g"] *[of g]
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−    unfolding reversepath_reversepath
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−    by (rule iffI)
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−qed
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−
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−lemma arc_reversepath:
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−  assumes "arc g" shows "arc(reversepath g)"
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−proof -
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−  have injg: "inj_on g {0..1}"
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−    using assms
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−    by (simp add: arc_def)
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−  have **: "\<And>x y::real. 1-x = 1-y \<Longrightarrow> x = y"
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−    by simp
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−  show ?thesis
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−    using assms  by (clarsimp simp: arc_def intro!: inj_onI) (simp add: inj_onD reversepath_def **)
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−qed
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−
+
−lemma simple_path_reversepath: "simple_path g \<Longrightarrow> simple_path (reversepath g)"
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−  apply (simp add: simple_path_def)
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−  apply (force simp: reversepath_def)
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−  done
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−
+
−lemmas reversepath_simps =
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−  path_reversepath path_image_reversepath pathstart_reversepath pathfinish_reversepath
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−
+
−lemma path_join[simp]:
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−  assumes "pathfinish g1 = pathstart g2"
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−  shows "path (g1 +++ g2) \<longleftrightarrow> path g1 \<and> path g2"
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−  unfolding path_def pathfinish_def pathstart_def
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−proof safe
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−  assume cont: "continuous_on {0..1} (g1 +++ g2)"
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−  have g1: "continuous_on {0..1} g1 \<longleftrightarrow> continuous_on {0..1} ((g1 +++ g2) \<circ> (\<lambda>x. x / 2))"
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−    by (intro continuous_on_cong refl) (auto simp: joinpaths_def)
+
−  have g2: "continuous_on {0..1} g2 \<longleftrightarrow> continuous_on {0..1} ((g1 +++ g2) \<circ> (\<lambda>x. x / 2 + 1/2))"
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−    using assms
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−    by (intro continuous_on_cong refl) (auto simp: joinpaths_def pathfinish_def pathstart_def)
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−  show "continuous_on {0..1} g1" and "continuous_on {0..1} g2"
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−    unfolding g1 g2
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−    by (auto intro!: continuous_intros continuous_on_subset[OF cont] simp del: o_apply)
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−next
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−  assume g1g2: "continuous_on {0..1} g1" "continuous_on {0..1} g2"
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−  have 01: "{0 .. 1} = {0..1/2} \<union> {1/2 .. 1::real}"
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−    by auto
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−  {
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−    fix x :: real
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−    assume "0 \<le> x" and "x \<le> 1"
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−    then have "x \<in> (\<lambda>x. x * 2) ` {0..1 / 2}"
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−      by (intro image_eqI[where x="x/2"]) auto
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−  }
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−  note 1 = this
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−  {
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−    fix x :: real
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−    assume "0 \<le> x" and "x \<le> 1"
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−    then have "x \<in> (\<lambda>x. x * 2 - 1) ` {1 / 2..1}"
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−      by (intro image_eqI[where x="x/2 + 1/2"]) auto
+
−  }
+
−  note 2 = this
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−  show "continuous_on {0..1} (g1 +++ g2)"
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−    using assms
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−    unfolding joinpaths_def 01
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−    apply (intro continuous_on_cases closed_atLeastAtMost g1g2[THEN continuous_on_compose2] continuous_intros)
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−    apply (auto simp: field_simps pathfinish_def pathstart_def intro!: 1 2)
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−    done
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−qed
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−
+
−
+
−subsection%unimportant \<open>Path Images\<close>
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−
+
−lemma bounded_path_image: "path g \<Longrightarrow> bounded(path_image g)"
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−  by (simp add: compact_imp_bounded compact_path_image)
+
−
+
−lemma closed_path_image:
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−  fixes g :: "real \<Rightarrow> 'a::t2_space"
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−  shows "path g \<Longrightarrow> closed(path_image g)"
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−  by (metis compact_path_image compact_imp_closed)
+
−
+
−lemma connected_simple_path_image: "simple_path g \<Longrightarrow> connected(path_image g)"
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−  by (metis connected_path_image simple_path_imp_path)
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−
+
−lemma compact_simple_path_image: "simple_path g \<Longrightarrow> compact(path_image g)"
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−  by (metis compact_path_image simple_path_imp_path)
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−
+
−lemma bounded_simple_path_image: "simple_path g \<Longrightarrow> bounded(path_image g)"
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−  by (metis bounded_path_image simple_path_imp_path)
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−
+
−lemma closed_simple_path_image:
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−  fixes g :: "real \<Rightarrow> 'a::t2_space"
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−  shows "simple_path g \<Longrightarrow> closed(path_image g)"
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−  by (metis closed_path_image simple_path_imp_path)
+
−
+
−lemma connected_arc_image: "arc g \<Longrightarrow> connected(path_image g)"
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−  by (metis connected_path_image arc_imp_path)
+
−
+
−lemma compact_arc_image: "arc g \<Longrightarrow> compact(path_image g)"
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−  by (metis compact_path_image arc_imp_path)
+
−
+
−lemma bounded_arc_image: "arc g \<Longrightarrow> bounded(path_image g)"
+
−  by (metis bounded_path_image arc_imp_path)
+
−
+
−lemma closed_arc_image:
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−  fixes g :: "real \<Rightarrow> 'a::t2_space"
+
−  shows "arc g \<Longrightarrow> closed(path_image g)"
+
−  by (metis closed_path_image arc_imp_path)
+
−
+
−lemma path_image_join_subset: "path_image (g1 +++ g2) \<subseteq> path_image g1 \<union> path_image g2"
+
−  unfolding path_image_def joinpaths_def
+
−  by auto
+
−
+
−lemma subset_path_image_join:
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−  assumes "path_image g1 \<subseteq> s"
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−    and "path_image g2 \<subseteq> s"
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−  shows "path_image (g1 +++ g2) \<subseteq> s"
+
−  using path_image_join_subset[of g1 g2] and assms
+
−  by auto
+
−
+
−lemma path_image_join:
+
−    "pathfinish g1 = pathstart g2 \<Longrightarrow> path_image(g1 +++ g2) = path_image g1 \<union> path_image g2"
+
−  apply (rule subset_antisym [OF path_image_join_subset])
+
−  apply (auto simp: pathfinish_def pathstart_def path_image_def joinpaths_def image_def)
+
−  apply (drule sym)
+
−  apply (rule_tac x="xa/2" in bexI, auto)
+
−  apply (rule ccontr)
+
−  apply (drule_tac x="(xa+1)/2" in bspec)
+
−  apply (auto simp: field_simps)
+
−  apply (drule_tac x="1/2" in bspec, auto)
+
−  done
+
−
+
−lemma not_in_path_image_join:
+
−  assumes "x \<notin> path_image g1"
+
−    and "x \<notin> path_image g2"
+
−  shows "x \<notin> path_image (g1 +++ g2)"
+
−  using assms and path_image_join_subset[of g1 g2]
+
−  by auto
+
−
+
−lemma pathstart_compose: "pathstart(f \<circ> p) = f(pathstart p)"
+
−  by (simp add: pathstart_def)
+
−
+
−lemma pathfinish_compose: "pathfinish(f \<circ> p) = f(pathfinish p)"
+
−  by (simp add: pathfinish_def)
+
−
+
−lemma path_image_compose: "path_image (f \<circ> p) = f ` (path_image p)"
+
−  by (simp add: image_comp path_image_def)
+
−
+
−lemma path_compose_join: "f \<circ> (p +++ q) = (f \<circ> p) +++ (f \<circ> q)"
+
−  by (rule ext) (simp add: joinpaths_def)
+
−
+
−lemma path_compose_reversepath: "f \<circ> reversepath p = reversepath(f \<circ> p)"
+
−  by (rule ext) (simp add: reversepath_def)
+
−
+
−lemma joinpaths_eq:
+
−  "(\<And>t. t \<in> {0..1} \<Longrightarrow> p t = p' t) \<Longrightarrow>
+
−   (\<And>t. t \<in> {0..1} \<Longrightarrow> q t = q' t)
+
−   \<Longrightarrow>  t \<in> {0..1} \<Longrightarrow> (p +++ q) t = (p' +++ q') t"
+
−  by (auto simp: joinpaths_def)
+
−
+
−lemma simple_path_inj_on: "simple_path g \<Longrightarrow> inj_on g {0<..<1}"
+
−  by (auto simp: simple_path_def path_image_def inj_on_def less_eq_real_def Ball_def)
+
−
+
−
+
−subsection%unimportant\<open>Simple paths with the endpoints removed\<close>
+
−
+
−lemma simple_path_endless:
+
−    "simple_path c \<Longrightarrow> path_image c - {pathstart c,pathfinish c} = c ` {0<..<1}"
+
−  apply (auto simp: simple_path_def path_image_def pathstart_def pathfinish_def Ball_def Bex_def image_def)
+
−  apply (metis eq_iff le_less_linear)
+
−  apply (metis leD linear)
+
−  using less_eq_real_def zero_le_one apply blast
+
−  using less_eq_real_def zero_le_one apply blast
+
−  done
+
−
+
−lemma connected_simple_path_endless:
+
−    "simple_path c \<Longrightarrow> connected(path_image c - {pathstart c,pathfinish c})"
+
−apply (simp add: simple_path_endless)
+
−apply (rule connected_continuous_image)
+
−apply (meson continuous_on_subset greaterThanLessThan_subseteq_atLeastAtMost_iff le_numeral_extra(3) le_numeral_extra(4) path_def simple_path_imp_path)
+
−by auto
+
−
+
−lemma nonempty_simple_path_endless:
+
−    "simple_path c \<Longrightarrow> path_image c - {pathstart c,pathfinish c} \<noteq> {}"
+
−  by (simp add: simple_path_endless)
+
−
+
−
+
−subsection%unimportant\<open>The operations on paths\<close>
+
−
+
−lemma path_image_subset_reversepath: "path_image(reversepath g) \<le> path_image g"
+
−  by (auto simp: path_image_def reversepath_def)
+
−
+
−lemma path_imp_reversepath: "path g \<Longrightarrow> path(reversepath g)"
+
−  apply (auto simp: path_def reversepath_def)
+
−  using continuous_on_compose [of "{0..1}" "\<lambda>x. 1 - x" g]
+
−  apply (auto simp: continuous_on_op_minus)
+
−  done
+
−
+
−lemma half_bounded_equal: "1 \<le> x * 2 \<Longrightarrow> x * 2 \<le> 1 \<longleftrightarrow> x = (1/2::real)"
+
−  by simp
+
−
+
−lemma continuous_on_joinpaths:
+
−  assumes "continuous_on {0..1} g1" "continuous_on {0..1} g2" "pathfinish g1 = pathstart g2"
+
−    shows "continuous_on {0..1} (g1 +++ g2)"
+
−proof -
+
−  have *: "{0..1::real} = {0..1/2} \<union> {1/2..1}"
+
−    by auto
+
−  have gg: "g2 0 = g1 1"
+
−    by (metis assms(3) pathfinish_def pathstart_def)
+
−  have 1: "continuous_on {0..1/2} (g1 +++ g2)"
+
−    apply (rule continuous_on_eq [of _ "g1 \<circ> (\<lambda>x. 2*x)"])
+
−    apply (rule continuous_intros | simp add: joinpaths_def assms)+
+
−    done
+
−  have "continuous_on {1/2..1} (g2 \<circ> (\<lambda>x. 2*x-1))"
+
−    apply (rule continuous_on_subset [of "{1/2..1}"])
+
−    apply (rule continuous_intros | simp add: image_affinity_atLeastAtMost_diff assms)+
+
−    done
+
−  then have 2: "continuous_on {1/2..1} (g1 +++ g2)"
+
−    apply (rule continuous_on_eq [of "{1/2..1}" "g2 \<circ> (\<lambda>x. 2*x-1)"])
+
−    apply (rule assms continuous_intros | simp add: joinpaths_def mult.commute half_bounded_equal gg)+
+
−    done
+
−  show ?thesis
+
−    apply (subst *)
+
−    apply (rule continuous_on_closed_Un)
+
−    using 1 2
+
−    apply auto
+
−    done
+
−qed
+
−
+
−lemma path_join_imp: "\<lbrakk>path g1; path g2; pathfinish g1 = pathstart g2\<rbrakk> \<Longrightarrow> path(g1 +++ g2)"
+
−  by (simp add: path_join)
+
−
+
−lemma simple_path_join_loop:
+
−  assumes "arc g1" "arc g2"
+
−          "pathfinish g1 = pathstart g2"  "pathfinish g2 = pathstart g1"
+
−          "path_image g1 \<inter> path_image g2 \<subseteq> {pathstart g1, pathstart g2}"
+
−  shows "simple_path(g1 +++ g2)"
+
−proof -
+
−  have injg1: "inj_on g1 {0..1}"
+
−    using assms
+
−    by (simp add: arc_def)
+
−  have injg2: "inj_on g2 {0..1}"
+
−    using assms
+
−    by (simp add: arc_def)
+
−  have g12: "g1 1 = g2 0"
+
−   and g21: "g2 1 = g1 0"
+
−   and sb:  "g1 ` {0..1} \<inter> g2 ` {0..1} \<subseteq> {g1 0, g2 0}"
+
−    using assms
+
−    by (simp_all add: arc_def pathfinish_def pathstart_def path_image_def)
+
−  { fix x and y::real
+
−    assume xyI: "x = 1 \<longrightarrow> y \<noteq> 0"
+
−       and xy: "x \<le> 1" "0 \<le> y" " y * 2 \<le> 1" "\<not> x * 2 \<le> 1" "g2 (2 * x - 1) = g1 (2 * y)"
+
−    have g1im: "g1 (2 * y) \<in> g1 ` {0..1} \<inter> g2 ` {0..1}"
+
−      using xy
+
−      apply simp
+
−      apply (rule_tac x="2 * x - 1" in image_eqI, auto)
+
−      done
+
−    have False
+
−      using subsetD [OF sb g1im] xy
+
−      apply auto
+
−      apply (drule inj_onD [OF injg1])
+
−      using g21 [symmetric] xyI
+
−      apply (auto dest: inj_onD [OF injg2])
+
−      done
+
−   } note * = this
+
−  { fix x and y::real
+
−    assume xy: "y \<le> 1" "0 \<le> x" "\<not> y * 2 \<le> 1" "x * 2 \<le> 1" "g1 (2 * x) = g2 (2 * y - 1)"
+
−    have g1im: "g1 (2 * x) \<in> g1 ` {0..1} \<inter> g2 ` {0..1}"
+
−      using xy
+
−      apply simp
+
−      apply (rule_tac x="2 * x" in image_eqI, auto)
+
−      done
+
−    have "x = 0 \<and> y = 1"
+
−      using subsetD [OF sb g1im] xy
+
−      apply auto
+
−      apply (force dest: inj_onD [OF injg1])
+
−      using  g21 [symmetric]
+
−      apply (auto dest: inj_onD [OF injg2])
+
−      done
+
−   } note ** = this
+
−  show ?thesis
+
−    using assms
+
−    apply (simp add: arc_def simple_path_def path_join, clarify)
+
−    apply (simp add: joinpaths_def split: if_split_asm)
+
−    apply (force dest: inj_onD [OF injg1])
+
−    apply (metis *)
+
−    apply (metis **)
+
−    apply (force dest: inj_onD [OF injg2])
+
−    done
+
−qed
+
−
+
−lemma arc_join:
+
−  assumes "arc g1" "arc g2"
+
−          "pathfinish g1 = pathstart g2"
+
−          "path_image g1 \<inter> path_image g2 \<subseteq> {pathstart g2}"
+
−    shows "arc(g1 +++ g2)"
+
−proof -
+
−  have injg1: "inj_on g1 {0..1}"
+
−    using assms
+
−    by (simp add: arc_def)
+
−  have injg2: "inj_on g2 {0..1}"
+
−    using assms
+
−    by (simp add: arc_def)
+
−  have g11: "g1 1 = g2 0"
+
−   and sb:  "g1 ` {0..1} \<inter> g2 ` {0..1} \<subseteq> {g2 0}"
+
−    using assms
+
−    by (simp_all add: arc_def pathfinish_def pathstart_def path_image_def)
+
−  { fix x and y::real
+
−    assume xy: "x \<le> 1" "0 \<le> y" " y * 2 \<le> 1" "\<not> x * 2 \<le> 1" "g2 (2 * x - 1) = g1 (2 * y)"
+
−    have g1im: "g1 (2 * y) \<in> g1 ` {0..1} \<inter> g2 ` {0..1}"
+
−      using xy
+
−      apply simp
+
−      apply (rule_tac x="2 * x - 1" in image_eqI, auto)
+
−      done
+
−    have False
+
−      using subsetD [OF sb g1im] xy
+
−      by (auto dest: inj_onD [OF injg2])
+
−   } note * = this
+
−  show ?thesis
+
−    apply (simp add: arc_def inj_on_def)
+
−    apply (clarsimp simp add: arc_imp_path assms path_join)
+
−    apply (simp add: joinpaths_def split: if_split_asm)
+
−    apply (force dest: inj_onD [OF injg1])
+
−    apply (metis *)
+
−    apply (metis *)
+
−    apply (force dest: inj_onD [OF injg2])
+
−    done
+
−qed
+
−
+
−lemma reversepath_joinpaths:
+
−    "pathfinish g1 = pathstart g2 \<Longrightarrow> reversepath(g1 +++ g2) = reversepath g2 +++ reversepath g1"
+
−  unfolding reversepath_def pathfinish_def pathstart_def joinpaths_def
+
−  by (rule ext) (auto simp: mult.commute)
+
−
+
−
+
−subsection%unimportant\<open>Some reversed and "if and only if" versions of joining theorems\<close>
+
−
+
−lemma path_join_path_ends:
+
−  fixes g1 :: "real \<Rightarrow> 'a::metric_space"
+
−  assumes "path(g1 +++ g2)" "path g2"
+
−    shows "pathfinish g1 = pathstart g2"
+
−proof (rule ccontr)
+
−  define e where "e = dist (g1 1) (g2 0)"
+
−  assume Neg: "pathfinish g1 \<noteq> pathstart g2"
+
−  then have "0 < dist (pathfinish g1) (pathstart g2)"
+
−    by auto
+
−  then have "e > 0"
+
−    by (metis e_def pathfinish_def pathstart_def)
+
−  then obtain d1 where "d1 > 0"
+
−       and d1: "\<And>x'. \<lbrakk>x'\<in>{0..1}; norm x' < d1\<rbrakk> \<Longrightarrow> dist (g2 x') (g2 0) < e/2"
+
−    using assms(2) unfolding path_def continuous_on_iff
+
−    apply (drule_tac x=0 in bspec, simp)
+
−    by (metis half_gt_zero_iff norm_conv_dist)
+
−  obtain d2 where "d2 > 0"
+
−       and d2: "\<And>x'. \<lbrakk>x'\<in>{0..1}; dist x' (1/2) < d2\<rbrakk>
+
−                      \<Longrightarrow> dist ((g1 +++ g2) x') (g1 1) < e/2"
+
−    using assms(1) \<open>e > 0\<close> unfolding path_def continuous_on_iff
+
−    apply (drule_tac x="1/2" in bspec, simp)
+
−    apply (drule_tac x="e/2" in spec)
+
−    apply (force simp: joinpaths_def)
+
−    done
+
−  have int01_1: "min (1/2) (min d1 d2) / 2 \<in> {0..1}"
+
−    using \<open>d1 > 0\<close> \<open>d2 > 0\<close> by (simp add: min_def)
+
−  have dist1: "norm (min (1 / 2) (min d1 d2) / 2) < d1"
+
−    using \<open>d1 > 0\<close> \<open>d2 > 0\<close> by (simp add: min_def dist_norm)
+
−  have int01_2: "1/2 + min (1/2) (min d1 d2) / 4 \<in> {0..1}"
+
−    using \<open>d1 > 0\<close> \<open>d2 > 0\<close> by (simp add: min_def)
+
−  have dist2: "dist (1 / 2 + min (1 / 2) (min d1 d2) / 4) (1 / 2) < d2"
+
−    using \<open>d1 > 0\<close> \<open>d2 > 0\<close> by (simp add: min_def dist_norm)
+
−  have [simp]: "\<not> min (1 / 2) (min d1 d2) \<le> 0"
+
−    using \<open>d1 > 0\<close> \<open>d2 > 0\<close> by (simp add: min_def)
+
−  have "dist (g2 (min (1 / 2) (min d1 d2) / 2)) (g1 1) < e/2"
+
−       "dist (g2 (min (1 / 2) (min d1 d2) / 2)) (g2 0) < e/2"
+
−    using d1 [OF int01_1 dist1] d2 [OF int01_2 dist2] by (simp_all add: joinpaths_def)
+
−  then have "dist (g1 1) (g2 0) < e/2 + e/2"
+
−    using dist_triangle_half_r e_def by blast
+
−  then show False
+
−    by (simp add: e_def [symmetric])
+
−qed
+
−
+
−lemma path_join_eq [simp]:
+
−  fixes g1 :: "real \<Rightarrow> 'a::metric_space"
+
−  assumes "path g1" "path g2"
+
−    shows "path(g1 +++ g2) \<longleftrightarrow> pathfinish g1 = pathstart g2"
+
−  using assms by (metis path_join_path_ends path_join_imp)
+
−
+
−lemma simple_path_joinE:
+
−  assumes "simple_path(g1 +++ g2)" and "pathfinish g1 = pathstart g2"
+
−  obtains "arc g1" "arc g2"
+
−          "path_image g1 \<inter> path_image g2 \<subseteq> {pathstart g1, pathstart g2}"
+
−proof -
+
−  have *: "\<And>x y. \<lbrakk>0 \<le> x; x \<le> 1; 0 \<le> y; y \<le> 1; (g1 +++ g2) x = (g1 +++ g2) y\<rbrakk>
+
−               \<Longrightarrow> x = y \<or> x = 0 \<and> y = 1 \<or> x = 1 \<and> y = 0"
+
−    using assms by (simp add: simple_path_def)
+
−  have "path g1"
+
−    using assms path_join simple_path_imp_path by blast
+
−  moreover have "inj_on g1 {0..1}"
+
−  proof (clarsimp simp: inj_on_def)
+
−    fix x y
+
−    assume "g1 x = g1 y" "0 \<le> x" "x \<le> 1" "0 \<le> y" "y \<le> 1"
+
−    then show "x = y"
+
−      using * [of "x/2" "y/2"] by (simp add: joinpaths_def split_ifs)
+
−  qed
+
−  ultimately have "arc g1"
+
−    using assms  by (simp add: arc_def)
+
−  have [simp]: "g2 0 = g1 1"
+
−    using assms by (metis pathfinish_def pathstart_def)
+
−  have "path g2"
+
−    using assms path_join simple_path_imp_path by blast
+
−  moreover have "inj_on g2 {0..1}"
+
−  proof (clarsimp simp: inj_on_def)
+
−    fix x y
+
−    assume "g2 x = g2 y" "0 \<le> x" "x \<le> 1" "0 \<le> y" "y \<le> 1"
+
−    then show "x = y"
+
−      using * [of "(x + 1) / 2" "(y + 1) / 2"]
+
−      by (force simp: joinpaths_def split_ifs divide_simps)
+
−  qed
+
−  ultimately have "arc g2"
+
−    using assms  by (simp add: arc_def)
+
−  have "g2 y = g1 0 \<or> g2 y = g1 1"
+
−       if "g1 x = g2 y" "0 \<le> x" "x \<le> 1" "0 \<le> y" "y \<le> 1" for x y
+
−      using * [of "x / 2" "(y + 1) / 2"] that
+
−      by (auto simp: joinpaths_def split_ifs divide_simps)
+
−  then have "path_image g1 \<inter> path_image g2 \<subseteq> {pathstart g1, pathstart g2}"
+
−    by (fastforce simp: pathstart_def pathfinish_def path_image_def)
+
−  with \<open>arc g1\<close> \<open>arc g2\<close> show ?thesis using that by blast
+
−qed
+
−
+
−lemma simple_path_join_loop_eq:
+
−  assumes "pathfinish g2 = pathstart g1" "pathfinish g1 = pathstart g2"
+
−    shows "simple_path(g1 +++ g2) \<longleftrightarrow>
+
−             arc g1 \<and> arc g2 \<and> path_image g1 \<inter> path_image g2 \<subseteq> {pathstart g1, pathstart g2}"
+
−by (metis assms simple_path_joinE simple_path_join_loop)
+
−
+
−lemma arc_join_eq:
+
−  assumes "pathfinish g1 = pathstart g2"
+
−    shows "arc(g1 +++ g2) \<longleftrightarrow>
+
−           arc g1 \<and> arc g2 \<and> path_image g1 \<inter> path_image g2 \<subseteq> {pathstart g2}"
+
−           (is "?lhs = ?rhs")
+
−proof
+
−  assume ?lhs
+
−  then have "simple_path(g1 +++ g2)" by (rule arc_imp_simple_path)
+
−  then have *: "\<And>x y. \<lbrakk>0 \<le> x; x \<le> 1; 0 \<le> y; y \<le> 1; (g1 +++ g2) x = (g1 +++ g2) y\<rbrakk>
+
−               \<Longrightarrow> x = y \<or> x = 0 \<and> y = 1 \<or> x = 1 \<and> y = 0"
+
−    using assms by (simp add: simple_path_def)
+
−  have False if "g1 0 = g2 u" "0 \<le> u" "u \<le> 1" for u
+
−    using * [of 0 "(u + 1) / 2"] that assms arc_distinct_ends [OF \<open>?lhs\<close>]
+
−    by (auto simp: joinpaths_def pathstart_def pathfinish_def split_ifs divide_simps)
+
−  then have n1: "pathstart g1 \<notin> path_image g2"
+
−    unfolding pathstart_def path_image_def
+
−    using atLeastAtMost_iff by blast
+
−  show ?rhs using \<open>?lhs\<close>
+
−    apply (rule simple_path_joinE [OF arc_imp_simple_path assms])
+
−    using n1 by force
+
−next
+
−  assume ?rhs then show ?lhs
+
−    using assms
+
−    by (fastforce simp: pathfinish_def pathstart_def intro!: arc_join)
+
−qed
+
−
+
−lemma arc_join_eq_alt:
+
−        "pathfinish g1 = pathstart g2
+
−        \<Longrightarrow> (arc(g1 +++ g2) \<longleftrightarrow>
+
−             arc g1 \<and> arc g2 \<and>
+
−             path_image g1 \<inter> path_image g2 = {pathstart g2})"
+
−using pathfinish_in_path_image by (fastforce simp: arc_join_eq)
+
−
+
−
+
−subsection%unimportant\<open>The joining of paths is associative\<close>
+
−
+
−lemma path_assoc:
+
−    "\<lbrakk>pathfinish p = pathstart q; pathfinish q = pathstart r\<rbrakk>
+
−     \<Longrightarrow> path(p +++ (q +++ r)) \<longleftrightarrow> path((p +++ q) +++ r)"
+
−by simp
+
−
+
−lemma simple_path_assoc:
+
−  assumes "pathfinish p = pathstart q" "pathfinish q = pathstart r"
+
−    shows "simple_path (p +++ (q +++ r)) \<longleftrightarrow> simple_path ((p +++ q) +++ r)"
+
−proof (cases "pathstart p = pathfinish r")
+
−  case True show ?thesis
+
−  proof
+
−    assume "simple_path (p +++ q +++ r)"
+
−    with assms True show "simple_path ((p +++ q) +++ r)"
+
−      by (fastforce simp add: simple_path_join_loop_eq arc_join_eq path_image_join
+
−                    dest: arc_distinct_ends [of r])
+
−  next
+
−    assume 0: "simple_path ((p +++ q) +++ r)"
+
−    with assms True have q: "pathfinish r \<notin> path_image q"
+
−      using arc_distinct_ends
+
−      by (fastforce simp add: simple_path_join_loop_eq arc_join_eq path_image_join)
+
−    have "pathstart r \<notin> path_image p"
+
−      using assms
+
−      by (metis 0 IntI arc_distinct_ends arc_join_eq_alt empty_iff insert_iff
+
−              pathfinish_in_path_image pathfinish_join simple_path_joinE)
+
−    with assms 0 q True show "simple_path (p +++ q +++ r)"
+
−      by (auto simp: simple_path_join_loop_eq arc_join_eq path_image_join
+
−               dest!: subsetD [OF _ IntI])
+
−  qed
+
−next
+
−  case False
+
−  { fix x :: 'a
+
−    assume a: "path_image p \<inter> path_image q \<subseteq> {pathstart q}"
+
−              "(path_image p \<union> path_image q) \<inter> path_image r \<subseteq> {pathstart r}"
+
−              "x \<in> path_image p" "x \<in> path_image r"
+
−    have "pathstart r \<in> path_image q"
+
−      by (metis assms(2) pathfinish_in_path_image)
+
−    with a have "x = pathstart q"
+
−      by blast
+
−  }
+
−  with False assms show ?thesis
+
−    by (auto simp: simple_path_eq_arc simple_path_join_loop_eq arc_join_eq path_image_join)
+
−qed
+
−
+
−lemma arc_assoc:
+
−     "\<lbrakk>pathfinish p = pathstart q; pathfinish q = pathstart r\<rbrakk>
+
−      \<Longrightarrow> arc(p +++ (q +++ r)) \<longleftrightarrow> arc((p +++ q) +++ r)"
+
−by (simp add: arc_simple_path simple_path_assoc)
+
−
+
−subsubsection%unimportant\<open>Symmetry and loops\<close>
+
−
+
−lemma path_sym:
+
−    "\<lbrakk>pathfinish p = pathstart q; pathfinish q = pathstart p\<rbrakk> \<Longrightarrow> path(p +++ q) \<longleftrightarrow> path(q +++ p)"
+
−  by auto
+
−
+
−lemma simple_path_sym:
+
−    "\<lbrakk>pathfinish p = pathstart q; pathfinish q = pathstart p\<rbrakk>
+
−     \<Longrightarrow> simple_path(p +++ q) \<longleftrightarrow> simple_path(q +++ p)"
+
−by (metis (full_types) inf_commute insert_commute simple_path_joinE simple_path_join_loop)
+
−
+
−lemma path_image_sym:
+
−    "\<lbrakk>pathfinish p = pathstart q; pathfinish q = pathstart p\<rbrakk>
+
−     \<Longrightarrow> path_image(p +++ q) = path_image(q +++ p)"
+
−by (simp add: path_image_join sup_commute)
+
−
+
−
+
−subsection\<open>Subpath\<close>
+
−
+
−definition%important subpath :: "real \<Rightarrow> real \<Rightarrow> (real \<Rightarrow> 'a) \<Rightarrow> real \<Rightarrow> 'a::real_normed_vector"
+
−  where "subpath a b g \<equiv> \<lambda>x. g((b - a) * x + a)"
+
−
+
−lemma path_image_subpath_gen:
+
−  fixes g :: "_ \<Rightarrow> 'a::real_normed_vector"
+
−  shows "path_image(subpath u v g) = g ` (closed_segment u v)"
+
−  by (auto simp add: closed_segment_real_eq path_image_def subpath_def)
+
−
+
−lemma path_image_subpath:
+
−  fixes g :: "real \<Rightarrow> 'a::real_normed_vector"
+
−  shows "path_image(subpath u v g) = (if u \<le> v then g ` {u..v} else g ` {v..u})"
+
−  by (simp add: path_image_subpath_gen closed_segment_eq_real_ivl)
+
−
+
−lemma path_image_subpath_commute:
+
−  fixes g :: "real \<Rightarrow> 'a::real_normed_vector"
+
−  shows "path_image(subpath u v g) = path_image(subpath v u g)"
+
−  by (simp add: path_image_subpath_gen closed_segment_eq_real_ivl)
+
−
+
−lemma path_subpath [simp]:
+
−  fixes g :: "real \<Rightarrow> 'a::real_normed_vector"
+
−  assumes "path g" "u \<in> {0..1}" "v \<in> {0..1}"
+
−    shows "path(subpath u v g)"
+
−proof -
+
−  have "continuous_on {0..1} (g \<circ> (\<lambda>x. ((v-u) * x+ u)))"
+
−    apply (rule continuous_intros | simp)+
+
−    apply (simp add: image_affinity_atLeastAtMost [where c=u])
+
−    using assms
+
−    apply (auto simp: path_def continuous_on_subset)
+
−    done
+
−  then show ?thesis
+
−    by (simp add: path_def subpath_def)
+
−qed
+
−
+
−lemma pathstart_subpath [simp]: "pathstart(subpath u v g) = g(u)"
+
−  by (simp add: pathstart_def subpath_def)
+
−
+
−lemma pathfinish_subpath [simp]: "pathfinish(subpath u v g) = g(v)"
+
−  by (simp add: pathfinish_def subpath_def)
+
−
+
−lemma subpath_trivial [simp]: "subpath 0 1 g = g"
+
−  by (simp add: subpath_def)
+
−
+
−lemma subpath_reversepath: "subpath 1 0 g = reversepath g"
+
−  by (simp add: reversepath_def subpath_def)
+
−
+
−lemma reversepath_subpath: "reversepath(subpath u v g) = subpath v u g"
+
−  by (simp add: reversepath_def subpath_def algebra_simps)
+
−
+
−lemma subpath_translation: "subpath u v ((\<lambda>x. a + x) \<circ> g) = (\<lambda>x. a + x) \<circ> subpath u v g"
+
−  by (rule ext) (simp add: subpath_def)
+
−
+
−lemma subpath_linear_image: "linear f \<Longrightarrow> subpath u v (f \<circ> g) = f \<circ> subpath u v g"
+
−  by (rule ext) (simp add: subpath_def)
+
−
+
−lemma affine_ineq:
+
−  fixes x :: "'a::linordered_idom"
+
−  assumes "x \<le> 1" "v \<le> u"
+
−    shows "v + x * u \<le> u + x * v"
+
−proof -
+
−  have "(1-x)*(u-v) \<ge> 0"
+
−    using assms by auto
+
−  then show ?thesis
+
−    by (simp add: algebra_simps)
+
−qed
+
−
+
−lemma sum_le_prod1:
+
−  fixes a::real shows "\<lbrakk>a \<le> 1; b \<le> 1\<rbrakk> \<Longrightarrow> a + b \<le> 1 + a * b"
+
−by (metis add.commute affine_ineq less_eq_real_def mult.right_neutral)
+
−
+
−lemma simple_path_subpath_eq:
+
−  "simple_path(subpath u v g) \<longleftrightarrow>
+
−     path(subpath u v g) \<and> u\<noteq>v \<and>
+
−     (\<forall>x y. x \<in> closed_segment u v \<and> y \<in> closed_segment u v \<and> g x = g y
+
−                \<longrightarrow> x = y \<or> x = u \<and> y = v \<or> x = v \<and> y = u)"
+
−    (is "?lhs = ?rhs")
+
−proof (rule iffI)
+
−  assume ?lhs
+
−  then have p: "path (\<lambda>x. g ((v - u) * x + u))"
+
−        and sim: "(\<And>x y. \<lbrakk>x\<in>{0..1}; y\<in>{0..1}; g ((v - u) * x + u) = g ((v - u) * y + u)\<rbrakk>
+
−                  \<Longrightarrow> x = y \<or> x = 0 \<and> y = 1 \<or> x = 1 \<and> y = 0)"
+
−    by (auto simp: simple_path_def subpath_def)
+
−  { fix x y
+
−    assume "x \<in> closed_segment u v" "y \<in> closed_segment u v" "g x = g y"
+
−    then have "x = y \<or> x = u \<and> y = v \<or> x = v \<and> y = u"
+
−    using sim [of "(x-u)/(v-u)" "(y-u)/(v-u)"] p
+
−    by (auto simp: closed_segment_real_eq image_affinity_atLeastAtMost divide_simps
+
−       split: if_split_asm)
+
−  } moreover
+
−  have "path(subpath u v g) \<and> u\<noteq>v"
+
−    using sim [of "1/3" "2/3"] p
+
−    by (auto simp: subpath_def)
+
−  ultimately show ?rhs
+
−    by metis
+
−next
+
−  assume ?rhs
+
−  then
+
−  have d1: "\<And>x y. \<lbrakk>g x = g y; u \<le> x; x \<le> v; u \<le> y; y \<le> v\<rbrakk> \<Longrightarrow> x = y \<or> x = u \<and> y = v \<or> x = v \<and> y = u"
+
−   and d2: "\<And>x y. \<lbrakk>g x = g y; v \<le> x; x \<le> u; v \<le> y; y \<le> u\<rbrakk> \<Longrightarrow> x = y \<or> x = u \<and> y = v \<or> x = v \<and> y = u"
+
−   and ne: "u < v \<or> v < u"
+
−   and psp: "path (subpath u v g)"
+
−    by (auto simp: closed_segment_real_eq image_affinity_atLeastAtMost)
+
−  have [simp]: "\<And>x. u + x * v = v + x * u \<longleftrightarrow> u=v \<or> x=1"
+
−    by algebra
+
−  show ?lhs using psp ne
+
−    unfolding simple_path_def subpath_def
+
−    by (fastforce simp add: algebra_simps affine_ineq mult_left_mono crossproduct_eq dest: d1 d2)
+
−qed
+
−
+
−lemma arc_subpath_eq:
+
−  "arc(subpath u v g) \<longleftrightarrow> path(subpath u v g) \<and> u\<noteq>v \<and> inj_on g (closed_segment u v)"
+
−    (is "?lhs = ?rhs")
+
−proof (rule iffI)
+
−  assume ?lhs
+
−  then have p: "path (\<lambda>x. g ((v - u) * x + u))"
+
−        and sim: "(\<And>x y. \<lbrakk>x\<in>{0..1}; y\<in>{0..1}; g ((v - u) * x + u) = g ((v - u) * y + u)\<rbrakk>
+
−                  \<Longrightarrow> x = y)"
+
−    by (auto simp: arc_def inj_on_def subpath_def)
+
−  { fix x y
+
−    assume "x \<in> closed_segment u v" "y \<in> closed_segment u v" "g x = g y"
+
−    then have "x = y"
+
−    using sim [of "(x-u)/(v-u)" "(y-u)/(v-u)"] p
+
−    by (force simp: inj_on_def closed_segment_real_eq image_affinity_atLeastAtMost divide_simps
+
−       split: if_split_asm)
+
−  } moreover
+
−  have "path(subpath u v g) \<and> u\<noteq>v"
+
−    using sim [of "1/3" "2/3"] p
+
−    by (auto simp: subpath_def)
+
−  ultimately show ?rhs
+
−    unfolding inj_on_def
+
−    by metis
+
−next
+
−  assume ?rhs
+
−  then
+
−  have d1: "\<And>x y. \<lbrakk>g x = g y; u \<le> x; x \<le> v; u \<le> y; y \<le> v\<rbrakk> \<Longrightarrow> x = y"
+
−   and d2: "\<And>x y. \<lbrakk>g x = g y; v \<le> x; x \<le> u; v \<le> y; y \<le> u\<rbrakk> \<Longrightarrow> x = y"
+
−   and ne: "u < v \<or> v < u"
+
−   and psp: "path (subpath u v g)"
+
−    by (auto simp: inj_on_def closed_segment_real_eq image_affinity_atLeastAtMost)
+
−  show ?lhs using psp ne
+
−    unfolding arc_def subpath_def inj_on_def
+
−    by (auto simp: algebra_simps affine_ineq mult_left_mono crossproduct_eq dest: d1 d2)
+
−qed
+
−
+
−
+
−lemma simple_path_subpath:
+
−  assumes "simple_path g" "u \<in> {0..1}" "v \<in> {0..1}" "u \<noteq> v"
+
−  shows "simple_path(subpath u v g)"
+
−  using assms
+
−  apply (simp add: simple_path_subpath_eq simple_path_imp_path)
+
−  apply (simp add: simple_path_def closed_segment_real_eq image_affinity_atLeastAtMost, fastforce)
+
−  done
+
−
+
−lemma arc_simple_path_subpath:
+
−    "\<lbrakk>simple_path g; u \<in> {0..1}; v \<in> {0..1}; g u \<noteq> g v\<rbrakk> \<Longrightarrow> arc(subpath u v g)"
+
−  by (force intro: simple_path_subpath simple_path_imp_arc)
+
−
+
−lemma arc_subpath_arc:
+
−    "\<lbrakk>arc g; u \<in> {0..1}; v \<in> {0..1}; u \<noteq> v\<rbrakk> \<Longrightarrow> arc(subpath u v g)"
+
−  by (meson arc_def arc_imp_simple_path arc_simple_path_subpath inj_onD)
+
−
+
−lemma arc_simple_path_subpath_interior:
+
−    "\<lbrakk>simple_path g; u \<in> {0..1}; v \<in> {0..1}; u \<noteq> v; \<bar>u-v\<bar> < 1\<rbrakk> \<Longrightarrow> arc(subpath u v g)"
+
−    apply (rule arc_simple_path_subpath)
+
−    apply (force simp: simple_path_def)+
+
−    done
+
−
+
−lemma path_image_subpath_subset:
+
−    "\<lbrakk>u \<in> {0..1}; v \<in> {0..1}\<rbrakk> \<Longrightarrow> path_image(subpath u v g) \<subseteq> path_image g"
+
−  apply (simp add: closed_segment_real_eq image_affinity_atLeastAtMost path_image_subpath)
+
−  apply (auto simp: path_image_def)
+
−  done  
+
−
+
−lemma join_subpaths_middle: "subpath (0) ((1 / 2)) p +++ subpath ((1 / 2)) 1 p = p"
+
−  by (rule ext) (simp add: joinpaths_def subpath_def divide_simps)
+
−
+
−
+
−subsection%unimportant\<open>There is a subpath to the frontier\<close>
+
−
+
−lemma subpath_to_frontier_explicit:
+
−    fixes S :: "'a::metric_space set"
+
−    assumes g: "path g" and "pathfinish g \<notin> S"
+
−    obtains u where "0 \<le> u" "u \<le> 1"
+
−                "\<And>x. 0 \<le> x \<and> x < u \<Longrightarrow> g x \<in> interior S"
+
−                "(g u \<notin> interior S)" "(u = 0 \<or> g u \<in> closure S)"
+
−proof -
+
−  have gcon: "continuous_on {0..1} g"     using g by (simp add: path_def)
+
−  then have com: "compact ({0..1} \<inter> {u. g u \<in> closure (- S)})"
+
−    apply (simp add: Int_commute [of "{0..1}"] compact_eq_bounded_closed closed_vimage_Int [unfolded vimage_def])
+
−    using compact_eq_bounded_closed apply fastforce
+
−    done
+
−  have "1 \<in> {u. g u \<in> closure (- S)}"
+
−    using assms by (simp add: pathfinish_def closure_def)
+
−  then have dis: "{0..1} \<inter> {u. g u \<in> closure (- S)} \<noteq> {}"
+
−    using atLeastAtMost_iff zero_le_one by blast
+
−  then obtain u where "0 \<le> u" "u \<le> 1" and gu: "g u \<in> closure (- S)"
+
−                  and umin: "\<And>t. \<lbrakk>0 \<le> t; t \<le> 1; g t \<in> closure (- S)\<rbrakk> \<Longrightarrow> u \<le> t"
+
−    using compact_attains_inf [OF com dis] by fastforce
+
−  then have umin': "\<And>t. \<lbrakk>0 \<le> t; t \<le> 1; t < u\<rbrakk> \<Longrightarrow>  g t \<in> S"
+
−    using closure_def by fastforce
+
−  { assume "u \<noteq> 0"
+
−    then have "u > 0" using \<open>0 \<le> u\<close> by auto
+
−    { fix e::real assume "e > 0"
+
−      obtain d where "d>0" and d: "\<And>x'. \<lbrakk>x' \<in> {0..1}; dist x' u \<le> d\<rbrakk> \<Longrightarrow> dist (g x') (g u) < e"
+
−        using continuous_onE [OF gcon _ \<open>e > 0\<close>] \<open>0 \<le> _\<close> \<open>_ \<le> 1\<close> atLeastAtMost_iff by auto
+
−      have *: "dist (max 0 (u - d / 2)) u \<le> d"
+
−        using \<open>0 \<le> u\<close> \<open>u \<le> 1\<close> \<open>d > 0\<close> by (simp add: dist_real_def)
+
−      have "\<exists>y\<in>S. dist y (g u) < e"
+
−        using \<open>0 < u\<close> \<open>u \<le> 1\<close> \<open>d > 0\<close>
+
−        by (force intro: d [OF _ *] umin')
+
−    }
+
−    then have "g u \<in> closure S"
+
−      by (simp add: frontier_def closure_approachable)
+
−  }
+
−  then show ?thesis
+
−    apply (rule_tac u=u in that)
+
−    apply (auto simp: \<open>0 \<le> u\<close> \<open>u \<le> 1\<close> gu interior_closure umin)
+
−    using \<open>_ \<le> 1\<close> interior_closure umin apply fastforce
+
−    done
+
−qed
+
−
+
−lemma subpath_to_frontier_strong:
+
−    assumes g: "path g" and "pathfinish g \<notin> S"
+
−    obtains u where "0 \<le> u" "u \<le> 1" "g u \<notin> interior S"
+
−                    "u = 0 \<or> (\<forall>x. 0 \<le> x \<and> x < 1 \<longrightarrow> subpath 0 u g x \<in> interior S)  \<and>  g u \<in> closure S"
+
−proof -
+
−  obtain u where "0 \<le> u" "u \<le> 1"
+
−             and gxin: "\<And>x. 0 \<le> x \<and> x < u \<Longrightarrow> g x \<in> interior S"
+
−             and gunot: "(g u \<notin> interior S)" and u0: "(u = 0 \<or> g u \<in> closure S)"
+
−    using subpath_to_frontier_explicit [OF assms] by blast
+
−  show ?thesis
+
−    apply (rule that [OF \<open>0 \<le> u\<close> \<open>u \<le> 1\<close>])
+
−    apply (simp add: gunot)
+
−    using \<open>0 \<le> u\<close> u0 by (force simp: subpath_def gxin)
+
−qed
+
−
+
−lemma subpath_to_frontier:
+
−    assumes g: "path g" and g0: "pathstart g \<in> closure S" and g1: "pathfinish g \<notin> S"
+
−    obtains u where "0 \<le> u" "u \<le> 1" "g u \<in> frontier S" "(path_image(subpath 0 u g) - {g u}) \<subseteq> interior S"
+
−proof -
+
−  obtain u where "0 \<le> u" "u \<le> 1"
+
−             and notin: "g u \<notin> interior S"
+
−             and disj: "u = 0 \<or>
+
−                        (\<forall>x. 0 \<le> x \<and> x < 1 \<longrightarrow> subpath 0 u g x \<in> interior S) \<and> g u \<in> closure S"
+
−    using subpath_to_frontier_strong [OF g g1] by blast
+
−  show ?thesis
+
−    apply (rule that [OF \<open>0 \<le> u\<close> \<open>u \<le> 1\<close>])
+
−    apply (metis DiffI disj frontier_def g0 notin pathstart_def)
+
−    using \<open>0 \<le> u\<close> g0 disj
+
−    apply (simp add: path_image_subpath_gen)
+
−    apply (auto simp: closed_segment_eq_real_ivl pathstart_def pathfinish_def subpath_def)
+
−    apply (rename_tac y)
+
−    apply (drule_tac x="y/u" in spec)
+
−    apply (auto split: if_split_asm)
+
−    done
+
−qed
+
−
+
−lemma exists_path_subpath_to_frontier:
+
−    fixes S :: "'a::real_normed_vector set"
+
−    assumes "path g" "pathstart g \<in> closure S" "pathfinish g \<notin> S"
+
−    obtains h where "path h" "pathstart h = pathstart g" "path_image h \<subseteq> path_image g"
+
−                    "path_image h - {pathfinish h} \<subseteq> interior S"
+
−                    "pathfinish h \<in> frontier S"
+
−proof -
+
−  obtain u where u: "0 \<le> u" "u \<le> 1" "g u \<in> frontier S" "(path_image(subpath 0 u g) - {g u}) \<subseteq> interior S"
+
−    using subpath_to_frontier [OF assms] by blast
+
−  show ?thesis
+
−    apply (rule that [of "subpath 0 u g"])
+
−    using assms u
+
−    apply (simp_all add: path_image_subpath)
+
−    apply (simp add: pathstart_def)
+
−    apply (force simp: closed_segment_eq_real_ivl path_image_def)
+
−    done
+
−qed
+
−
+
−lemma exists_path_subpath_to_frontier_closed:
+
−    fixes S :: "'a::real_normed_vector set"
+
−    assumes S: "closed S" and g: "path g" and g0: "pathstart g \<in> S" and g1: "pathfinish g \<notin> S"
+
−    obtains h where "path h" "pathstart h = pathstart g" "path_image h \<subseteq> path_image g \<inter> S"
+
−                    "pathfinish h \<in> frontier S"
+
−proof -
+
−  obtain h where h: "path h" "pathstart h = pathstart g" "path_image h \<subseteq> path_image g"
+
−                    "path_image h - {pathfinish h} \<subseteq> interior S"
+
−                    "pathfinish h \<in> frontier S"
+
−    using exists_path_subpath_to_frontier [OF g _ g1] closure_closed [OF S] g0 by auto
+
−  show ?thesis
+
−    apply (rule that [OF \<open>path h\<close>])
+
−    using assms h
+
−    apply auto
+
−    apply (metis Diff_single_insert frontier_subset_eq insert_iff interior_subset subset_iff)
+
−    done
+
−qed
+
−
+
−
+
−subsection \<open>Shift Path to Start at Some Given Point\<close>
+
−
+
−definition%important shiftpath :: "real \<Rightarrow> (real \<Rightarrow> 'a::topological_space) \<Rightarrow> real \<Rightarrow> 'a"
+
−  where "shiftpath a f = (\<lambda>x. if (a + x) \<le> 1 then f (a + x) else f (a + x - 1))"
+
−
+
−lemma pathstart_shiftpath: "a \<le> 1 \<Longrightarrow> pathstart (shiftpath a g) = g a"
+
−  unfolding pathstart_def shiftpath_def by auto
+
−
+
−lemma pathfinish_shiftpath:
+
−  assumes "0 \<le> a"
+
−    and "pathfinish g = pathstart g"
+
−  shows "pathfinish (shiftpath a g) = g a"
+
−  using assms
+
−  unfolding pathstart_def pathfinish_def shiftpath_def
+
−  by auto
+
−
+
−lemma endpoints_shiftpath:
+
−  assumes "pathfinish g = pathstart g"
+
−    and "a \<in> {0 .. 1}"
+
−  shows "pathfinish (shiftpath a g) = g a"
+
−    and "pathstart (shiftpath a g) = g a"
+
−  using assms
+
−  by (auto intro!: pathfinish_shiftpath pathstart_shiftpath)
+
−
+
−lemma closed_shiftpath:
+
−  assumes "pathfinish g = pathstart g"
+
−    and "a \<in> {0..1}"
+
−  shows "pathfinish (shiftpath a g) = pathstart (shiftpath a g)"
+
−  using endpoints_shiftpath[OF assms]
+
−  by auto
+
−
+
−lemma path_shiftpath:
+
−  assumes "path g"
+
−    and "pathfinish g = pathstart g"
+
−    and "a \<in> {0..1}"
+
−  shows "path (shiftpath a g)"
+
−proof -
+
−  have *: "{0 .. 1} = {0 .. 1-a} \<union> {1-a .. 1}"
+
−    using assms(3) by auto
+
−  have **: "\<And>x. x + a = 1 \<Longrightarrow> g (x + a - 1) = g (x + a)"
+
−    using assms(2)[unfolded pathfinish_def pathstart_def]
+
−    by auto
+
−  show ?thesis
+
−    unfolding path_def shiftpath_def *
+
−  proof (rule continuous_on_closed_Un)
+
−    have contg: "continuous_on {0..1} g"
+
−      using \<open>path g\<close> path_def by blast
+
−    show "continuous_on {0..1-a} (\<lambda>x. if a + x \<le> 1 then g (a + x) else g (a + x - 1))"
+
−    proof (rule continuous_on_eq)
+
−      show "continuous_on {0..1-a} (g \<circ> (+) a)"
+
−        by (intro continuous_intros continuous_on_subset [OF contg]) (use \<open>a \<in> {0..1}\<close> in auto)
+
−    qed auto
+
−    show "continuous_on {1-a..1} (\<lambda>x. if a + x \<le> 1 then g (a + x) else g (a + x - 1))"
+
−    proof (rule continuous_on_eq)
+
−      show "continuous_on {1-a..1} (g \<circ> (+) (a - 1))"
+
−        by (intro continuous_intros continuous_on_subset [OF contg]) (use \<open>a \<in> {0..1}\<close> in auto)
+
−    qed (auto simp:  "**" add.commute add_diff_eq)
+
−  qed auto
+
−qed
+
−
+
−lemma shiftpath_shiftpath:
+
−  assumes "pathfinish g = pathstart g"
+
−    and "a \<in> {0..1}"
+
−    and "x \<in> {0..1}"
+
−  shows "shiftpath (1 - a) (shiftpath a g) x = g x"
+
−  using assms
+
−  unfolding pathfinish_def pathstart_def shiftpath_def
+
−  by auto
+
−
+
−lemma path_image_shiftpath:
+
−  assumes a: "a \<in> {0..1}"
+
−    and "pathfinish g = pathstart g"
+
−  shows "path_image (shiftpath a g) = path_image g"
+
−proof -
+
−  { fix x
+
−    assume g: "g 1 = g 0" "x \<in> {0..1::real}" and gne: "\<And>y. y\<in>{0..1} \<inter> {x. \<not> a + x \<le> 1} \<Longrightarrow> g x \<noteq> g (a + y - 1)"
+
−    then have "\<exists>y\<in>{0..1} \<inter> {x. a + x \<le> 1}. g x = g (a + y)"
+
−    proof (cases "a \<le> x")
+
−      case False
+
−      then show ?thesis
+
−        apply (rule_tac x="1 + x - a" in bexI)
+
−        using g gne[of "1 + x - a"] a
+
−        apply (force simp: field_simps)+
+
−        done
+
−    next
+
−      case True
+
−      then show ?thesis
+
−        using g a  by (rule_tac x="x - a" in bexI) (auto simp: field_simps)
+
−    qed
+
−  }
+
−  then show ?thesis
+
−    using assms
+
−    unfolding shiftpath_def path_image_def pathfinish_def pathstart_def
+
−    by (auto simp: image_iff)
+
−qed
+
−
+
−lemma simple_path_shiftpath:
+
−  assumes "simple_path g" "pathfinish g = pathstart g" and a: "0 \<le> a" "a \<le> 1"
+
−    shows "simple_path (shiftpath a g)"
+
−  unfolding simple_path_def
+
−proof (intro conjI impI ballI)
+
−  show "path (shiftpath a g)"
+
−    by (simp add: assms path_shiftpath simple_path_imp_path)
+
−  have *: "\<And>x y. \<lbrakk>g x = g y; x \<in> {0..1}; y \<in> {0..1}\<rbrakk> \<Longrightarrow> x = y \<or> x = 0 \<and> y = 1 \<or> x = 1 \<and> y = 0"
+
−    using assms by (simp add:  simple_path_def)
+
−  show "x = y \<or> x = 0 \<and> y = 1 \<or> x = 1 \<and> y = 0"
+
−    if "x \<in> {0..1}" "y \<in> {0..1}" "shiftpath a g x = shiftpath a g y" for x y
+
−    using that a unfolding shiftpath_def
+
−    by (force split: if_split_asm dest!: *)
+
−qed
+
−
+
−
+
−subsection \<open>Straight-Line Paths\<close>
+
−
+
−definition%important linepath :: "'a::real_normed_vector \<Rightarrow> 'a \<Rightarrow> real \<Rightarrow> 'a"
+
−  where "linepath a b = (\<lambda>x. (1 - x) *\<^sub>R a + x *\<^sub>R b)"
+
−
+
−lemma pathstart_linepath[simp]: "pathstart (linepath a b) = a"
+
−  unfolding pathstart_def linepath_def
+
−  by auto
+
−
+
−lemma pathfinish_linepath[simp]: "pathfinish (linepath a b) = b"
+
−  unfolding pathfinish_def linepath_def
+
−  by auto
+
−
+
−lemma linepath_inner: "linepath a b x \<bullet> v = linepath (a \<bullet> v) (b \<bullet> v) x"
+
−  by (simp add: linepath_def algebra_simps)
+
−
+
−lemma Re_linepath': "Re (linepath a b x) = linepath (Re a) (Re b) x"
+
−  by (simp add: linepath_def)
+
−
+
−lemma Im_linepath': "Im (linepath a b x) = linepath (Im a) (Im b) x"
+
−  by (simp add: linepath_def)
+
−
+
−lemma linepath_0': "linepath a b 0 = a"
+
−  by (simp add: linepath_def)
+
−
+
−lemma linepath_1': "linepath a b 1 = b"
+
−  by (simp add: linepath_def)
+
−
+
−lemma continuous_linepath_at[intro]: "continuous (at x) (linepath a b)"
+
−  unfolding linepath_def
+
−  by (intro continuous_intros)
+
−
+
−lemma continuous_on_linepath [intro,continuous_intros]: "continuous_on s (linepath a b)"
+
−  using continuous_linepath_at
+
−  by (auto intro!: continuous_at_imp_continuous_on)
+
−
+
−lemma path_linepath[iff]: "path (linepath a b)"
+
−  unfolding path_def
+
−  by (rule continuous_on_linepath)
+
−
+
−lemma path_image_linepath[simp]: "path_image (linepath a b) = closed_segment a b"
+
−  unfolding path_image_def segment linepath_def
+
−  by auto
+
−
+
−lemma reversepath_linepath[simp]: "reversepath (linepath a b) = linepath b a"
+
−  unfolding reversepath_def linepath_def
+
−  by auto
+
−
+
−lemma linepath_0 [simp]: "linepath 0 b x = x *\<^sub>R b"
+
−  by (simp add: linepath_def)
+
−
+
−lemma linepath_cnj: "cnj (linepath a b x) = linepath (cnj a) (cnj b) x"
+
−  by (simp add: linepath_def)
+
−
+
−lemma arc_linepath:
+
−  assumes "a \<noteq> b" shows [simp]: "arc (linepath a b)"
+
−proof -
+
−  {
+
−    fix x y :: "real"
+
−    assume "x *\<^sub>R b + y *\<^sub>R a = x *\<^sub>R a + y *\<^sub>R b"
+
−    then have "(x - y) *\<^sub>R a = (x - y) *\<^sub>R b"
+
−      by (simp add: algebra_simps)
+
−    with assms have "x = y"
+
−      by simp
+
−  }
+
−  then show ?thesis
+
−    unfolding arc_def inj_on_def
+
−    by (fastforce simp: algebra_simps linepath_def)
+
−qed
+
−
+
−lemma simple_path_linepath[intro]: "a \<noteq> b \<Longrightarrow> simple_path (linepath a b)"
+
−  by (simp add: arc_imp_simple_path)
+
−
+
−lemma linepath_trivial [simp]: "linepath a a x = a"
+
−  by (simp add: linepath_def real_vector.scale_left_diff_distrib)
+
−
+
−lemma linepath_refl: "linepath a a = (\<lambda>x. a)"
+
−  by auto
+
−
+
−lemma subpath_refl: "subpath a a g = linepath (g a) (g a)"
+
−  by (simp add: subpath_def linepath_def algebra_simps)
+
−
+
−lemma linepath_of_real: "(linepath (of_real a) (of_real b) x) = of_real ((1 - x)*a + x*b)"
+
−  by (simp add: scaleR_conv_of_real linepath_def)
+
−
+
−lemma of_real_linepath: "of_real (linepath a b x) = linepath (of_real a) (of_real b) x"
+
−  by (metis linepath_of_real mult.right_neutral of_real_def real_scaleR_def)
+
−
+
−lemma inj_on_linepath:
+
−  assumes "a \<noteq> b" shows "inj_on (linepath a b) {0..1}"
+
−proof (clarsimp simp: inj_on_def linepath_def)
+
−  fix x y
+
−  assume "(1 - x) *\<^sub>R a + x *\<^sub>R b = (1 - y) *\<^sub>R a + y *\<^sub>R b" "0 \<le> x" "x \<le> 1" "0 \<le> y" "y \<le> 1"
+
−  then have "x *\<^sub>R (a - b) = y *\<^sub>R (a - b)"
+
−    by (auto simp: algebra_simps)
+
−  then show "x=y"
+
−    using assms by auto
+
−qed
+
−
+
−lemma linepath_le_1:
+
−  fixes a::"'a::linordered_idom" shows "\<lbrakk>a \<le> 1; b \<le> 1; 0 \<le> u; u \<le> 1\<rbrakk> \<Longrightarrow> (1 - u) * a + u * b \<le> 1"
+
−  using mult_left_le [of a "1-u"] mult_left_le [of b u] by auto
+
−
+
−
+
−subsection%unimportant\<open>Segments via convex hulls\<close>
+
−
+
−lemma segments_subset_convex_hull:
+
−    "closed_segment a b \<subseteq> (convex hull {a,b,c})"
+
−    "closed_segment a c \<subseteq> (convex hull {a,b,c})"
+
−    "closed_segment b c \<subseteq> (convex hull {a,b,c})"
+
−    "closed_segment b a \<subseteq> (convex hull {a,b,c})"
+
−    "closed_segment c a \<subseteq> (convex hull {a,b,c})"
+
−    "closed_segment c b \<subseteq> (convex hull {a,b,c})"
+
−by (auto simp: segment_convex_hull linepath_of_real  elim!: rev_subsetD [OF _ hull_mono])
+
−
+
−lemma midpoints_in_convex_hull:
+
−  assumes "x \<in> convex hull s" "y \<in> convex hull s"
+
−    shows "midpoint x y \<in> convex hull s"
+
−proof -
+
−  have "(1 - inverse(2)) *\<^sub>R x + inverse(2) *\<^sub>R y \<in> convex hull s"
+
−    by (rule convexD_alt) (use assms in auto)
+
−  then show ?thesis
+
−    by (simp add: midpoint_def algebra_simps)
+
−qed
+
−
+
−lemma not_in_interior_convex_hull_3:
+
−  fixes a :: "complex"
+
−  shows "a \<notin> interior(convex hull {a,b,c})"
+
−        "b \<notin> interior(convex hull {a,b,c})"
+
−        "c \<notin> interior(convex hull {a,b,c})"
+
−  by (auto simp: card_insert_le_m1 not_in_interior_convex_hull)
+
−
+
−lemma midpoint_in_closed_segment [simp]: "midpoint a b \<in> closed_segment a b"
+
−  using midpoints_in_convex_hull segment_convex_hull by blast
+
−
+
−lemma midpoint_in_open_segment [simp]: "midpoint a b \<in> open_segment a b \<longleftrightarrow> a \<noteq> b"
+
−  by (simp add: open_segment_def)
+
−
+
−lemma continuous_IVT_local_extremum:
+
−  fixes f :: "'a::euclidean_space \<Rightarrow> real"
+
−  assumes contf: "continuous_on (closed_segment a b) f"
+
−      and "a \<noteq> b" "f a = f b"
+
−  obtains z where "z \<in> open_segment a b"
+
−                  "(\<forall>w \<in> closed_segment a b. (f w) \<le> (f z)) \<or>
+
−                   (\<forall>w \<in> closed_segment a b. (f z) \<le> (f w))"
+
−proof -
+
−  obtain c where "c \<in> closed_segment a b" and c: "\<And>y. y \<in> closed_segment a b \<Longrightarrow> f y \<le> f c"
+
−    using continuous_attains_sup [of "closed_segment a b" f] contf by auto
+
−  obtain d where "d \<in> closed_segment a b" and d: "\<And>y. y \<in> closed_segment a b \<Longrightarrow> f d \<le> f y"
+
−    using continuous_attains_inf [of "closed_segment a b" f] contf by auto
+
−  show ?thesis
+
−  proof (cases "c \<in> open_segment a b \<or> d \<in> open_segment a b")
+
−    case True
+
−    then show ?thesis
+
−      using c d that by blast
+
−  next
+
−    case False
+
−    then have "(c = a \<or> c = b) \<and> (d = a \<or> d = b)"
+
−      by (simp add: \<open>c \<in> closed_segment a b\<close> \<open>d \<in> closed_segment a b\<close> open_segment_def)
+
−    with \<open>a \<noteq> b\<close> \<open>f a = f b\<close> c d show ?thesis
+
−      by (rule_tac z = "midpoint a b" in that) (fastforce+)
+
−  qed
+
−qed
+
−
+
−text\<open>An injective map into R is also an open map w.r.T. the universe, and conversely. \<close>
+
−proposition injective_eq_1d_open_map_UNIV:
+
−  fixes f :: "real \<Rightarrow> real"
+
−  assumes contf: "continuous_on S f" and S: "is_interval S"
+
−    shows "inj_on f S \<longleftrightarrow> (\<forall>T. open T \<and> T \<subseteq> S \<longrightarrow> open(f ` T))"
+
−          (is "?lhs = ?rhs")
+
−proof safe
+
−  fix T
+
−  assume injf: ?lhs and "open T" and "T \<subseteq> S"
+
−  have "\<exists>U. open U \<and> f x \<in> U \<and> U \<subseteq> f ` T" if "x \<in> T" for x
+
−  proof -
+
−    obtain \<delta> where "\<delta> > 0" and \<delta>: "cball x \<delta> \<subseteq> T"
+
−      using \<open>open T\<close> \<open>x \<in> T\<close> open_contains_cball_eq by blast
+
−    show ?thesis
+
−    proof (intro exI conjI)
+
−      have "closed_segment (x-\<delta>) (x+\<delta>) = {x-\<delta>..x+\<delta>}"
+
−        using \<open>0 < \<delta>\<close> by (auto simp: closed_segment_eq_real_ivl)
+
−      also have "\<dots> \<subseteq> S"
+
−        using \<delta> \<open>T \<subseteq> S\<close> by (auto simp: dist_norm subset_eq)
+
−      finally have "f ` (open_segment (x-\<delta>) (x+\<delta>)) = open_segment (f (x-\<delta>)) (f (x+\<delta>))"
+
−        using continuous_injective_image_open_segment_1
+
−        by (metis continuous_on_subset [OF contf] inj_on_subset [OF injf])
+
−      then show "open (f ` {x-\<delta><..<x+\<delta>})"
+
−        using \<open>0 < \<delta>\<close> by (simp add: open_segment_eq_real_ivl)
+
−      show "f x \<in> f ` {x - \<delta><..<x + \<delta>}"
+
−        by (auto simp: \<open>\<delta> > 0\<close>)
+
−      show "f ` {x - \<delta><..<x + \<delta>} \<subseteq> f ` T"
+
−        using \<delta> by (auto simp: dist_norm subset_iff)
+
−    qed
+
−  qed
+
−  with open_subopen show "open (f ` T)"
+
−    by blast
+
−next
+
−  assume R: ?rhs
+
−  have False if xy: "x \<in> S" "y \<in> S" and "f x = f y" "x \<noteq> y" for x y
+
−  proof -
+
−    have "open (f ` open_segment x y)"
+
−      using R
+
−      by (metis S convex_contains_open_segment is_interval_convex open_greaterThanLessThan open_segment_eq_real_ivl xy)
+
−    moreover
+
−    have "continuous_on (closed_segment x y) f"
+
−      by (meson S closed_segment_subset contf continuous_on_subset is_interval_convex that)
+
−    then obtain \<xi> where "\<xi> \<in> open_segment x y"
+
−                    and \<xi>: "(\<forall>w \<in> closed_segment x y. (f w) \<le> (f \<xi>)) \<or>
+
−                            (\<forall>w \<in> closed_segment x y. (f \<xi>) \<le> (f w))"
+
−      using continuous_IVT_local_extremum [of x y f] \<open>f x = f y\<close> \<open>x \<noteq> y\<close> by blast
+
−    ultimately obtain e where "e>0" and e: "\<And>u. dist u (f \<xi>) < e \<Longrightarrow> u \<in> f ` open_segment x y"
+
−      using open_dist by (metis image_eqI)
+
−    have fin: "f \<xi> + (e/2) \<in> f ` open_segment x y" "f \<xi> - (e/2) \<in> f ` open_segment x y"
+
−      using e [of "f \<xi> + (e/2)"] e [of "f \<xi> - (e/2)"] \<open>e > 0\<close> by (auto simp: dist_norm)
+
−    show ?thesis
+
−      using \<xi> \<open>0 < e\<close> fin open_closed_segment by fastforce
+
−  qed
+
−  then show ?lhs
+
−    by (force simp: inj_on_def)
+
−qed
+
−
+
−
+
−subsection%unimportant \<open>Bounding a point away from a path\<close>
+
−
+
−lemma not_on_path_ball:
+
−  fixes g :: "real \<Rightarrow> 'a::heine_borel"
+
−  assumes "path g"
+
−    and z: "z \<notin> path_image g"
+
−  shows "\<exists>e > 0. ball z e \<inter> path_image g = {}"
+
−proof -
+
−  have "closed (path_image g)"
+
−    by (simp add: \<open>path g\<close> closed_path_image)
+
−  then obtain a where "a \<in> path_image g" "\<forall>y \<in> path_image g. dist z a \<le> dist z y"
+
−    by (auto intro: distance_attains_inf[OF _ path_image_nonempty, of g z])
+
−  then show ?thesis
+
−    by (rule_tac x="dist z a" in exI) (use dist_commute z in auto)
+
−qed
+
−
+
−lemma not_on_path_cball:
+
−  fixes g :: "real \<Rightarrow> 'a::heine_borel"
+
−  assumes "path g"
+
−    and "z \<notin> path_image g"
+
−  shows "\<exists>e>0. cball z e \<inter> (path_image g) = {}"
+
−proof -
+
−  obtain e where "ball z e \<inter> path_image g = {}" "e > 0"
+
−    using not_on_path_ball[OF assms] by auto
+
−  moreover have "cball z (e/2) \<subseteq> ball z e"
+
−    using \<open>e > 0\<close> by auto
+
−  ultimately show ?thesis
+
−    by (rule_tac x="e/2" in exI) auto
+
−qed
+
−
+
−subsection \<open>Path component\<close>
+
−
+
−text \<open>Original formalization by Tom Hales\<close>
+
−
+
−definition%important "path_component s x y \<longleftrightarrow>
+
−  (\<exists>g. path g \<and> path_image g \<subseteq> s \<and> pathstart g = x \<and> pathfinish g = y)"
+
−
+
−abbreviation%important
+
−  "path_component_set s x \<equiv> Collect (path_component s x)"
+
−
+
−lemmas path_defs = path_def pathstart_def pathfinish_def path_image_def path_component_def
+
−
+
−lemma path_component_mem:
+
−  assumes "path_component s x y"
+
−  shows "x \<in> s" and "y \<in> s"
+
−  using assms
+
−  unfolding path_defs
+
−  by auto
+
−
+
−lemma path_component_refl:
+
−  assumes "x \<in> s"
+
−  shows "path_component s x x"
+
−  unfolding path_defs
+
−  apply (rule_tac x="\<lambda>u. x" in exI)
+
−  using assms
+
−  apply (auto intro!: continuous_intros)
+
−  done
+
−
+
−lemma path_component_refl_eq: "path_component s x x \<longleftrightarrow> x \<in> s"
+
−  by (auto intro!: path_component_mem path_component_refl)
+
−
+
−lemma path_component_sym: "path_component s x y \<Longrightarrow> path_component s y x"
+
−  unfolding path_component_def
+
−  apply (erule exE)
+
−  apply (rule_tac x="reversepath g" in exI, auto)
+
−  done
+
−
+
−lemma path_component_trans:
+
−  assumes "path_component s x y" and "path_component s y z"
+
−  shows "path_component s x z"
+
−  using assms
+
−  unfolding path_component_def
+
−  apply (elim exE)
+
−  apply (rule_tac x="g +++ ga" in exI)
+
−  apply (auto simp: path_image_join)
+
−  done
+
−
+
−lemma path_component_of_subset: "s \<subseteq> t \<Longrightarrow> path_component s x y \<Longrightarrow> path_component t x y"
+
−  unfolding path_component_def by auto
+
−
+
−lemma path_connected_linepath:
+
−    fixes s :: "'a::real_normed_vector set"
+
−    shows "closed_segment a b \<subseteq> s \<Longrightarrow> path_component s a b"
+
−  unfolding path_component_def
+
−  by (rule_tac x="linepath a b" in exI, auto)
+
−
+
−subsubsection%unimportant \<open>Path components as sets\<close>
+
−
+
−lemma path_component_set:
+
−  "path_component_set s x =
+
−    {y. (\<exists>g. path g \<and> path_image g \<subseteq> s \<and> pathstart g = x \<and> pathfinish g = y)}"
+
−  by (auto simp: path_component_def)
+
−
+
−lemma path_component_subset: "path_component_set s x \<subseteq> s"
+
−  by (auto simp: path_component_mem(2))
+
−
+
−lemma path_component_eq_empty: "path_component_set s x = {} \<longleftrightarrow> x \<notin> s"
+
−  using path_component_mem path_component_refl_eq
+
−    by fastforce
+
−
+
−lemma path_component_mono:
+
−     "s \<subseteq> t \<Longrightarrow> (path_component_set s x) \<subseteq> (path_component_set t x)"
+
−  by (simp add: Collect_mono path_component_of_subset)
+
−
+
−lemma path_component_eq:
+
−   "y \<in> path_component_set s x \<Longrightarrow> path_component_set s y = path_component_set s x"
+
−by (metis (no_types, lifting) Collect_cong mem_Collect_eq path_component_sym path_component_trans)
+
−
+
−
+
−subsection \<open>Path connectedness of a space\<close>
+
−
+
−definition%important "path_connected s \<longleftrightarrow>
+
−  (\<forall>x\<in>s. \<forall>y\<in>s. \<exists>g. path g \<and> path_image g \<subseteq> s \<and> pathstart g = x \<and> pathfinish g = y)"
+
−
+
−lemma path_connected_component: "path_connected s \<longleftrightarrow> (\<forall>x\<in>s. \<forall>y\<in>s. path_component s x y)"
+
−  unfolding path_connected_def path_component_def by auto
+
−
+
−lemma path_connected_component_set: "path_connected s \<longleftrightarrow> (\<forall>x\<in>s. path_component_set s x = s)"
+
−  unfolding path_connected_component path_component_subset
+
−  using path_component_mem by blast
+
−
+
−lemma path_component_maximal:
+
−     "\<lbrakk>x \<in> t; path_connected t; t \<subseteq> s\<rbrakk> \<Longrightarrow> t \<subseteq> (path_component_set s x)"
+
−  by (metis path_component_mono path_connected_component_set)
+
−
+
−lemma convex_imp_path_connected:
+
−  fixes s :: "'a::real_normed_vector set"
+
−  assumes "convex s"
+
−  shows "path_connected s"
+
−  unfolding path_connected_def
+
−  using assms convex_contains_segment by fastforce
+
−
+
−lemma path_connected_UNIV [iff]: "path_connected (UNIV :: 'a::real_normed_vector set)"
+
−  by (simp add: convex_imp_path_connected)
+
−
+
−lemma path_component_UNIV: "path_component_set UNIV x = (UNIV :: 'a::real_normed_vector set)"
+
−  using path_connected_component_set by auto
+
−
+
−lemma path_connected_imp_connected:
+
−  assumes "path_connected S"
+
−  shows "connected S"
+
−proof (rule connectedI)
+
−  fix e1 e2
+
−  assume as: "open e1" "open e2" "S \<subseteq> e1 \<union> e2" "e1 \<inter> e2 \<inter> S = {}" "e1 \<inter> S \<noteq> {}" "e2 \<inter> S \<noteq> {}"
+
−  then obtain x1 x2 where obt:"x1 \<in> e1 \<inter> S" "x2 \<in> e2 \<inter> S"
+
−    by auto
+
−  then obtain g where g: "path g" "path_image g \<subseteq> S" "pathstart g = x1" "pathfinish g = x2"
+
−    using assms[unfolded path_connected_def,rule_format,of x1 x2] by auto
+
−  have *: "connected {0..1::real}"
+
−    by (auto intro!: convex_connected convex_real_interval)
+
−  have "{0..1} \<subseteq> {x \<in> {0..1}. g x \<in> e1} \<union> {x \<in> {0..1}. g x \<in> e2}"
+
−    using as(3) g(2)[unfolded path_defs] by blast
+
−  moreover have "{x \<in> {0..1}. g x \<in> e1} \<inter> {x \<in> {0..1}. g x \<in> e2} = {}"
+
−    using as(4) g(2)[unfolded path_defs]
+
−    unfolding subset_eq
+
−    by auto
+
−  moreover have "{x \<in> {0..1}. g x \<in> e1} \<noteq> {} \<and> {x \<in> {0..1}. g x \<in> e2} \<noteq> {}"
+
−    using g(3,4)[unfolded path_defs]
+
−    using obt
+
−    by (simp add: ex_in_conv [symmetric], metis zero_le_one order_refl)
+
−  ultimately show False
+
−    using *[unfolded connected_local not_ex, rule_format,
+
−      of "{0..1} \<inter> g -` e1" "{0..1} \<inter> g -` e2"]
+
−    using continuous_openin_preimage_gen[OF g(1)[unfolded path_def] as(1)]
+
−    using continuous_openin_preimage_gen[OF g(1)[unfolded path_def] as(2)]
+
−    by auto
+
−qed
+
−
+
−lemma open_path_component:
+
−  fixes S :: "'a::real_normed_vector set"
+
−  assumes "open S"
+
−  shows "open (path_component_set S x)"
+
−  unfolding open_contains_ball
+
−proof
+
−  fix y
+
−  assume as: "y \<in> path_component_set S x"
+
−  then have "y \<in> S"
+
−    by (simp add: path_component_mem(2))
+
−  then obtain e where e: "e > 0" "ball y e \<subseteq> S"
+
−    using assms[unfolded open_contains_ball]
+
−    by auto
+
−have "\<And>u. dist y u < e \<Longrightarrow> path_component S x u"
+
−      by (metis (full_types) as centre_in_ball convex_ball convex_imp_path_connected e mem_Collect_eq mem_ball path_component_eq path_component_of_subset path_connected_component)
+
−  then show "\<exists>e > 0. ball y e \<subseteq> path_component_set S x"
+
−    using \<open>e>0\<close> by auto
+
−qed
+
−
+
−lemma open_non_path_component:
+
−  fixes S :: "'a::real_normed_vector set"
+
−  assumes "open S"
+
−  shows "open (S - path_component_set S x)"
+
−  unfolding open_contains_ball
+
−proof
+
−  fix y
+
−  assume y: "y \<in> S - path_component_set S x"
+
−  then obtain e where e: "e > 0" "ball y e \<subseteq> S"
+
−    using assms openE by auto
+
−  show "\<exists>e>0. ball y e \<subseteq> S - path_component_set S x"
+
−  proof (intro exI conjI subsetI DiffI notI)
+
−    show "\<And>x. x \<in> ball y e \<Longrightarrow> x \<in> S"
+
−      using e by blast
+
−    show False if "z \<in> ball y e" "z \<in> path_component_set S x" for z
+
−    proof -
+
−      have "y \<in> path_component_set S z"
+
−        by (meson assms convex_ball convex_imp_path_connected e open_contains_ball_eq open_path_component path_component_maximal that(1))
+
−      then have "y \<in> path_component_set S x"
+
−        using path_component_eq that(2) by blast
+
−      then show False
+
−        using y by blast
+
−    qed
+
−  qed (use e in auto)
+
−qed
+
−
+
−lemma connected_open_path_connected:
+
−  fixes S :: "'a::real_normed_vector set"
+
−  assumes "open S"
+
−    and "connected S"
+
−  shows "path_connected S"
+
−  unfolding path_connected_component_set
+
−proof (rule, rule, rule path_component_subset, rule)
+
−  fix x y
+
−  assume "x \<in> S" and "y \<in> S"
+
−  show "y \<in> path_component_set S x"
+
−  proof (rule ccontr)
+
−    assume "\<not> ?thesis"
+
−    moreover have "path_component_set S x \<inter> S \<noteq> {}"
+
−      using \<open>x \<in> S\<close> path_component_eq_empty path_component_subset[of S x]
+
−      by auto
+
−    ultimately
+
−    show False
+
−      using \<open>y \<in> S\<close> open_non_path_component[OF assms(1)] open_path_component[OF assms(1)]
+
−      using assms(2)[unfolded connected_def not_ex, rule_format,
+
−        of "path_component_set S x" "S - path_component_set S x"]
+
−      by auto
+
−  qed
+
−qed
+
−
+
−lemma path_connected_continuous_image:
+
−  assumes "continuous_on S f"
+
−    and "path_connected S"
+
−  shows "path_connected (f ` S)"
+
−  unfolding path_connected_def
+
−proof (rule, rule)
+
−  fix x' y'
+
−  assume "x' \<in> f ` S" "y' \<in> f ` S"
+
−  then obtain x y where x: "x \<in> S" and y: "y \<in> S" and x': "x' = f x" and y': "y' = f y"
+
−    by auto
+
−  from x y obtain g where "path g \<and> path_image g \<subseteq> S \<and> pathstart g = x \<and> pathfinish g = y"
+
−    using assms(2)[unfolded path_connected_def] by fast
+
−  then show "\<exists>g. path g \<and> path_image g \<subseteq> f ` S \<and> pathstart g = x' \<and> pathfinish g = y'"
+
−    unfolding x' y'
+
−    apply (rule_tac x="f \<circ> g" in exI)
+
−    unfolding path_defs
+
−    apply (intro conjI continuous_on_compose continuous_on_subset[OF assms(1)])
+
−    apply auto
+
−    done
+
−qed
+
−
+
−lemma path_connected_translationI:
+
−  fixes a :: "'a :: topological_group_add"
+
−  assumes "path_connected S" shows "path_connected ((\<lambda>x. a + x) ` S)"
+
−  by (intro path_connected_continuous_image assms continuous_intros)
+
−
+
−lemma path_connected_translation:
+
−  fixes a :: "'a :: topological_group_add"
+
−  shows "path_connected ((\<lambda>x. a + x) ` S) = path_connected S"
+
−proof -
+
−  have "\<forall>x y. (+) (x::'a) ` (+) (0 - x) ` y = y"
+
−    by (simp add: image_image)
+
−  then show ?thesis
+
−    by (metis (no_types) path_connected_translationI)
+
−qed
+
−
+
−lemma path_connected_segment [simp]:
+
−    fixes a :: "'a::real_normed_vector"
+
−    shows "path_connected (closed_segment a b)"
+
−  by (simp add: convex_imp_path_connected)
+
−
+
−lemma path_connected_open_segment [simp]:
+
−    fixes a :: "'a::real_normed_vector"
+
−    shows "path_connected (open_segment a b)"
+
−  by (simp add: convex_imp_path_connected)
+
−
+
−lemma homeomorphic_path_connectedness:
+
−  "S homeomorphic T \<Longrightarrow> path_connected S \<longleftrightarrow> path_connected T"
+
−  unfolding homeomorphic_def homeomorphism_def by (metis path_connected_continuous_image)
+
−
+
−lemma path_connected_empty [simp]: "path_connected {}"
+
−  unfolding path_connected_def by auto
+
−
+
−lemma path_connected_singleton [simp]: "path_connected {a}"
+
−  unfolding path_connected_def pathstart_def pathfinish_def path_image_def
+
−  apply clarify
+
−  apply (rule_tac x="\<lambda>x. a" in exI)
+
−  apply (simp add: image_constant_conv)
+
−  apply (simp add: path_def continuous_on_const)
+
−  done
+
−
+
−lemma path_connected_Un:
+
−  assumes "path_connected S"
+
−    and "path_connected T"
+
−    and "S \<inter> T \<noteq> {}"
+
−  shows "path_connected (S \<union> T)"
+
−  unfolding path_connected_component
+
−proof (intro ballI)
+
−  fix x y
+
−  assume x: "x \<in> S \<union> T" and y: "y \<in> S \<union> T"
+
−  from assms obtain z where z: "z \<in> S" "z \<in> T"
+
−    by auto
+
−  show "path_component (S \<union> T) x y"
+
−    using x y
+
−  proof safe
+
−    assume "x \<in> S" "y \<in> S"
+
−    then show "path_component (S \<union> T) x y"
+
−      by (meson Un_upper1 \<open>path_connected S\<close> path_component_of_subset path_connected_component)
+
−  next
+
−    assume "x \<in> S" "y \<in> T"
+
−    then show "path_component (S \<union> T) x y"
+
−      by (metis z assms(1-2) le_sup_iff order_refl path_component_of_subset path_component_trans path_connected_component)
+
−  next
+
−  assume "x \<in> T" "y \<in> S"
+
−    then show "path_component (S \<union> T) x y"
+
−      by (metis z assms(1-2) le_sup_iff order_refl path_component_of_subset path_component_trans path_connected_component)
+
−  next
+
−    assume "x \<in> T" "y \<in> T"
+
−    then show "path_component (S \<union> T) x y"
+
−      by (metis Un_upper1 assms(2) path_component_of_subset path_connected_component sup_commute)
+
−  qed
+
−qed
+
−
+
−lemma path_connected_UNION:
+
−  assumes "\<And>i. i \<in> A \<Longrightarrow> path_connected (S i)"
+
−    and "\<And>i. i \<in> A \<Longrightarrow> z \<in> S i"
+
−  shows "path_connected (\<Union>i\<in>A. S i)"
+
−  unfolding path_connected_component
+
−proof clarify
+
−  fix x i y j
+
−  assume *: "i \<in> A" "x \<in> S i" "j \<in> A" "y \<in> S j"
+
−  then have "path_component (S i) x z" and "path_component (S j) z y"
+
−    using assms by (simp_all add: path_connected_component)
+
−  then have "path_component (\<Union>i\<in>A. S i) x z" and "path_component (\<Union>i\<in>A. S i) z y"
+
−    using *(1,3) by (auto elim!: path_component_of_subset [rotated])
+
−  then show "path_component (\<Union>i\<in>A. S i) x y"
+
−    by (rule path_component_trans)
+
−qed
+
−
+
−lemma path_component_path_image_pathstart:
+
−  assumes p: "path p" and x: "x \<in> path_image p"
+
−  shows "path_component (path_image p) (pathstart p) x"
+
−proof -
+
−  obtain y where x: "x = p y" and y: "0 \<le> y" "y \<le> 1"
+
−    using x by (auto simp: path_image_def)
+
−  show ?thesis
+
−    unfolding path_component_def 
+
−  proof (intro exI conjI)
+
−    have "continuous_on {0..1} (p \<circ> ((*) y))"
+
−      apply (rule continuous_intros)+
+
−      using p [unfolded path_def] y
+
−      apply (auto simp: mult_le_one intro: continuous_on_subset [of _ p])
+
−      done
+
−    then show "path (\<lambda>u. p (y * u))"
+
−      by (simp add: path_def)
+
−    show "path_image (\<lambda>u. p (y * u)) \<subseteq> path_image p"
+
−      using y mult_le_one by (fastforce simp: path_image_def image_iff)
+
−  qed (auto simp: pathstart_def pathfinish_def x)
+
−qed
+
−
+
−lemma path_connected_path_image: "path p \<Longrightarrow> path_connected(path_image p)"
+
−  unfolding path_connected_component
+
−  by (meson path_component_path_image_pathstart path_component_sym path_component_trans)
+
−
+
−lemma path_connected_path_component [simp]:
+
−   "path_connected (path_component_set s x)"
+
−proof -
+
−  { fix y z
+
−    assume pa: "path_component s x y" "path_component s x z"
+
−    then have pae: "path_component_set s x = path_component_set s y"
+
−      using path_component_eq by auto
+
−    have yz: "path_component s y z"
+
−      using pa path_component_sym path_component_trans by blast
+
−    then have "\<exists>g. path g \<and> path_image g \<subseteq> path_component_set s x \<and> pathstart g = y \<and> pathfinish g = z"
+
−      apply (simp add: path_component_def, clarify)
+
−      apply (rule_tac x=g in exI)
+
−      by (simp add: pae path_component_maximal path_connected_path_image pathstart_in_path_image)
+
−  }
+
−  then show ?thesis
+
−    by (simp add: path_connected_def)
+
−qed
+
−
+
−lemma path_component: "path_component S x y \<longleftrightarrow> (\<exists>t. path_connected t \<and> t \<subseteq> S \<and> x \<in> t \<and> y \<in> t)"
+
−  apply (intro iffI)
+
−  apply (metis path_connected_path_image path_defs(5) pathfinish_in_path_image pathstart_in_path_image)
+
−  using path_component_of_subset path_connected_component by blast
+
−
+
−lemma path_component_path_component [simp]:
+
−   "path_component_set (path_component_set S x) x = path_component_set S x"
+
−proof (cases "x \<in> S")
+
−  case True show ?thesis
+
−    apply (rule subset_antisym)
+
−    apply (simp add: path_component_subset)
+
−    by (simp add: True path_component_maximal path_component_refl path_connected_path_component)
+
−next
+
−  case False then show ?thesis
+
−    by (metis False empty_iff path_component_eq_empty)
+
−qed
+
−
+
−lemma path_component_subset_connected_component:
+
−   "(path_component_set S x) \<subseteq> (connected_component_set S x)"
+
−proof (cases "x \<in> S")
+
−  case True show ?thesis
+
−    apply (rule connected_component_maximal)
+
−    apply (auto simp: True path_component_subset path_component_refl path_connected_imp_connected)
+
−    done
+
−next
+
−  case False then show ?thesis
+
−    using path_component_eq_empty by auto
+
−qed
+
−
+
−
+
−subsection%unimportant\<open>Lemmas about path-connectedness\<close>
+
−
+
−lemma path_connected_linear_image:
+
−  fixes f :: "'a::real_normed_vector \<Rightarrow> 'b::real_normed_vector"
+
−  assumes "path_connected S" "bounded_linear f"
+
−    shows "path_connected(f ` S)"
+
−by (auto simp: linear_continuous_on assms path_connected_continuous_image)
+
−
+
−lemma is_interval_path_connected: "is_interval S \<Longrightarrow> path_connected S"
+
−  by (simp add: convex_imp_path_connected is_interval_convex)
+
−
+
−lemma linear_homeomorphism_image:
+
−  fixes f :: "'a::euclidean_space \<Rightarrow> 'b::euclidean_space"
+
−  assumes "linear f" "inj f"
+
−    obtains g where "homeomorphism (f ` S) S g f"
+
−using linear_injective_left_inverse [OF assms]
+
−apply clarify
+
−apply (rule_tac g=g in that)
+
−using assms
+
−apply (auto simp: homeomorphism_def eq_id_iff [symmetric] image_comp comp_def linear_conv_bounded_linear linear_continuous_on)
+
−done
+
−
+
−lemma linear_homeomorphic_image:
+
−  fixes f :: "'a::euclidean_space \<Rightarrow> 'b::euclidean_space"
+
−  assumes "linear f" "inj f"
+
−    shows "S homeomorphic f ` S"
+
−by (meson homeomorphic_def homeomorphic_sym linear_homeomorphism_image [OF assms])
+
−
+
−lemma path_connected_Times:
+
−  assumes "path_connected s" "path_connected t"
+
−    shows "path_connected (s \<times> t)"
+
−proof (simp add: path_connected_def Sigma_def, clarify)
+
−  fix x1 y1 x2 y2
+
−  assume "x1 \<in> s" "y1 \<in> t" "x2 \<in> s" "y2 \<in> t"
+
−  obtain g where "path g" and g: "path_image g \<subseteq> s" and gs: "pathstart g = x1" and gf: "pathfinish g = x2"
+
−    using \<open>x1 \<in> s\<close> \<open>x2 \<in> s\<close> assms by (force simp: path_connected_def)
+
−  obtain h where "path h" and h: "path_image h \<subseteq> t" and hs: "pathstart h = y1" and hf: "pathfinish h = y2"
+
−    using \<open>y1 \<in> t\<close> \<open>y2 \<in> t\<close> assms by (force simp: path_connected_def)
+
−  have "path (\<lambda>z. (x1, h z))"
+
−    using \<open>path h\<close>
+
−    apply (simp add: path_def)
+
−    apply (rule continuous_on_compose2 [where f = h])
+
−    apply (rule continuous_intros | force)+
+
−    done
+
−  moreover have "path (\<lambda>z. (g z, y2))"
+
−    using \<open>path g\<close>
+
−    apply (simp add: path_def)
+
−    apply (rule continuous_on_compose2 [where f = g])
+
−    apply (rule continuous_intros | force)+
+
−    done
+
−  ultimately have 1: "path ((\<lambda>z. (x1, h z)) +++ (\<lambda>z. (g z, y2)))"
+
−    by (metis hf gs path_join_imp pathstart_def pathfinish_def)
+
−  have "path_image ((\<lambda>z. (x1, h z)) +++ (\<lambda>z. (g z, y2))) \<subseteq> path_image (\<lambda>z. (x1, h z)) \<union> path_image (\<lambda>z. (g z, y2))"
+
−    by (rule Path_Connected.path_image_join_subset)
+
−  also have "\<dots> \<subseteq> (\<Union>x\<in>s. \<Union>x1\<in>t. {(x, x1)})"
+
−    using g h \<open>x1 \<in> s\<close> \<open>y2 \<in> t\<close> by (force simp: path_image_def)
+
−  finally have 2: "path_image ((\<lambda>z. (x1, h z)) +++ (\<lambda>z. (g z, y2))) \<subseteq> (\<Union>x\<in>s. \<Union>x1\<in>t. {(x, x1)})" .
+
−  show "\<exists>g. path g \<and> path_image g \<subseteq> (\<Union>x\<in>s. \<Union>x1\<in>t. {(x, x1)}) \<and>
+
−            pathstart g = (x1, y1) \<and> pathfinish g = (x2, y2)"
+
−    apply (intro exI conjI)
+
−       apply (rule 1)
+
−      apply (rule 2)
+
−     apply (metis hs pathstart_def pathstart_join)
+
−    by (metis gf pathfinish_def pathfinish_join)
+
−qed
+
−
+
−lemma is_interval_path_connected_1:
+
−  fixes s :: "real set"
+
−  shows "is_interval s \<longleftrightarrow> path_connected s"
+
−using is_interval_connected_1 is_interval_path_connected path_connected_imp_connected by blast
+
−
+
−
+
−subsection%unimportant\<open>Path components\<close>
+
−
+
−lemma Union_path_component [simp]:
+
−   "Union {path_component_set S x |x. x \<in> S} = S"
+
−apply (rule subset_antisym)
+
−using path_component_subset apply force
+
−using path_component_refl by auto
+
−
+
−lemma path_component_disjoint:
+
−   "disjnt (path_component_set S a) (path_component_set S b) \<longleftrightarrow>
+
−    (a \<notin> path_component_set S b)"
+
−apply (auto simp: disjnt_def)
+
−using path_component_eq apply fastforce
+
−using path_component_sym path_component_trans by blast
+
−
+
−lemma path_component_eq_eq:
+
−   "path_component S x = path_component S y \<longleftrightarrow>
+
−        (x \<notin> S) \<and> (y \<notin> S) \<or> x \<in> S \<and> y \<in> S \<and> path_component S x y"
+
−apply (rule iffI, metis (no_types) path_component_mem(1) path_component_refl)
+
−apply (erule disjE, metis Collect_empty_eq_bot path_component_eq_empty)
+
−apply (rule ext)
+
−apply (metis path_component_trans path_component_sym)
+
−done
+
−
+
−lemma path_component_unique:
+
−  assumes "x \<in> c" "c \<subseteq> S" "path_connected c"
+
−          "\<And>c'. \<lbrakk>x \<in> c'; c' \<subseteq> S; path_connected c'\<rbrakk> \<Longrightarrow> c' \<subseteq> c"
+
−   shows "path_component_set S x = c"
+
−apply (rule subset_antisym)
+
−using assms
+
−apply (metis mem_Collect_eq subsetCE path_component_eq_eq path_component_subset path_connected_path_component)
+
−by (simp add: assms path_component_maximal)
+
−
+
−lemma path_component_intermediate_subset:
+
−   "path_component_set u a \<subseteq> t \<and> t \<subseteq> u
+
−        \<Longrightarrow> path_component_set t a = path_component_set u a"
+
−by (metis (no_types) path_component_mono path_component_path_component subset_antisym)
+
−
+
−lemma complement_path_component_Union:
+
−  fixes x :: "'a :: topological_space"
+
−  shows "S - path_component_set S x =
+
−         \<Union>({path_component_set S y| y. y \<in> S} - {path_component_set S x})"
+
−proof -
+
−  have *: "(\<And>x. x \<in> S - {a} \<Longrightarrow> disjnt a x) \<Longrightarrow> \<Union>S - a = \<Union>(S - {a})"
+
−    for a::"'a set" and S
+
−    by (auto simp: disjnt_def)
+
−  have "\<And>y. y \<in> {path_component_set S x |x. x \<in> S} - {path_component_set S x}
+
−            \<Longrightarrow> disjnt (path_component_set S x) y"
+
−    using path_component_disjoint path_component_eq by fastforce
+
−  then have "\<Union>{path_component_set S x |x. x \<in> S} - path_component_set S x =
+
−             \<Union>({path_component_set S y |y. y \<in> S} - {path_component_set S x})"
+
−    by (meson *)
+
−  then show ?thesis by simp
+
−qed
+
−
+
−
+
−subsection \<open>Sphere is path-connected\<close>
+
−
+
−lemma path_connected_punctured_universe:
+
−  assumes "2 \<le> DIM('a::euclidean_space)"
+
−  shows "path_connected (- {a::'a})"
+
−proof -
+
−  let ?A = "{x::'a. \<exists>i\<in>Basis. x \<bullet> i < a \<bullet> i}"
+
−  let ?B = "{x::'a. \<exists>i\<in>Basis. a \<bullet> i < x \<bullet> i}"
+
−
+
−  have A: "path_connected ?A"
+
−    unfolding Collect_bex_eq
+
−  proof (rule path_connected_UNION)
+
−    fix i :: 'a
+
−    assume "i \<in> Basis"
+
−    then show "(\<Sum>i\<in>Basis. (a \<bullet> i - 1)*\<^sub>R i) \<in> {x::'a. x \<bullet> i < a \<bullet> i}"
+
−      by simp
+
−    show "path_connected {x. x \<bullet> i < a \<bullet> i}"
+
−      using convex_imp_path_connected [OF convex_halfspace_lt, of i "a \<bullet> i"]
+
−      by (simp add: inner_commute)
+
−  qed
+
−  have B: "path_connected ?B"
+
−    unfolding Collect_bex_eq
+
−  proof (rule path_connected_UNION)
+
−    fix i :: 'a
+
−    assume "i \<in> Basis"
+
−    then show "(\<Sum>i\<in>Basis. (a \<bullet> i + 1) *\<^sub>R i) \<in> {x::'a. a \<bullet> i < x \<bullet> i}"
+
−      by simp
+
−    show "path_connected {x. a \<bullet> i < x \<bullet> i}"
+
−      using convex_imp_path_connected [OF convex_halfspace_gt, of "a \<bullet> i" i]
+
−      by (simp add: inner_commute)
+
−  qed
+
−  obtain S :: "'a set" where "S \<subseteq> Basis" and "card S = Suc (Suc 0)"
+
−    using ex_card[OF assms]
+
−    by auto
+
−  then obtain b0 b1 :: 'a where "b0 \<in> Basis" and "b1 \<in> Basis" and "b0 \<noteq> b1"
+
−    unfolding card_Suc_eq by auto
+
−  then have "a + b0 - b1 \<in> ?A \<inter> ?B"
+
−    by (auto simp: inner_simps inner_Basis)
+
−  then have "?A \<inter> ?B \<noteq> {}"
+
−    by fast
+
−  with A B have "path_connected (?A \<union> ?B)"
+
−    by (rule path_connected_Un)
+
−  also have "?A \<union> ?B = {x. \<exists>i\<in>Basis. x \<bullet> i \<noteq> a \<bullet> i}"
+
−    unfolding neq_iff bex_disj_distrib Collect_disj_eq ..
+
−  also have "\<dots> = {x. x \<noteq> a}"
+
−    unfolding euclidean_eq_iff [where 'a='a]
+
−    by (simp add: Bex_def)
+
−  also have "\<dots> = - {a}"
+
−    by auto
+
−  finally show ?thesis .
+
−qed
+
−
+
−corollary connected_punctured_universe:
+
−  "2 \<le> DIM('N::euclidean_space) \<Longrightarrow> connected(- {a::'N})"
+
−  by (simp add: path_connected_punctured_universe path_connected_imp_connected)
+
−
+
−proposition path_connected_sphere:
+
−  fixes a :: "'a :: euclidean_space"
+
−  assumes "2 \<le> DIM('a)"
+
−  shows "path_connected(sphere a r)"
+
−proof (cases r "0::real" rule: linorder_cases)
+
−  case less
+
−  then show ?thesis
+
−    by (simp add: path_connected_empty)
+
−next
+
−  case equal
+
−  then show ?thesis
+
−    by (simp add: path_connected_singleton)
+
−next
+
−  case greater
+
−  then have eq: "(sphere (0::'a) r) = (\<lambda>x. (r / norm x) *\<^sub>R x) ` (- {0::'a})"
+
−    by (force simp: image_iff split: if_split_asm)
+
−  have "continuous_on (- {0::'a}) (\<lambda>x. (r / norm x) *\<^sub>R x)"
+
−    by (intro continuous_intros) auto
+
−  then have "path_connected ((\<lambda>x. (r / norm x) *\<^sub>R x) ` (- {0::'a}))"
+
−    by (intro path_connected_continuous_image path_connected_punctured_universe assms)
+
−  with eq have "path_connected (sphere (0::'a) r)"
+
−    by auto
+
−  then have "path_connected((+) a ` (sphere (0::'a) r))"
+
−    by (simp add: path_connected_translation)
+
−  then show ?thesis
+
−    by (metis add.right_neutral sphere_translation)
+
−qed
+
−
+
−lemma connected_sphere:
+
−    fixes a :: "'a :: euclidean_space"
+
−    assumes "2 \<le> DIM('a)"
+
−      shows "connected(sphere a r)"
+
−  using path_connected_sphere [OF assms]
+
−  by (simp add: path_connected_imp_connected)
+
−
+
−
+
−corollary path_connected_complement_bounded_convex:
+
−    fixes s :: "'a :: euclidean_space set"
+
−    assumes "bounded s" "convex s" and 2: "2 \<le> DIM('a)"
+
−    shows "path_connected (- s)"
+
−proof (cases "s = {}")
+
−  case True then show ?thesis
+
−    using convex_imp_path_connected by auto
+
−next
+
−  case False
+
−  then obtain a where "a \<in> s" by auto
+
−  { fix x y assume "x \<notin> s" "y \<notin> s"
+
−    then have "x \<noteq> a" "y \<noteq> a" using \<open>a \<in> s\<close> by auto
+
−    then have bxy: "bounded(insert x (insert y s))"
+
−      by (simp add: \<open>bounded s\<close>)
+
−    then obtain B::real where B: "0 < B" and Bx: "norm (a - x) < B" and By: "norm (a - y) < B"
+
−                          and "s \<subseteq> ball a B"
+
−      using bounded_subset_ballD [OF bxy, of a] by (auto simp: dist_norm)
+
−    define C where "C = B / norm(x - a)"
+
−    { fix u
+
−      assume u: "(1 - u) *\<^sub>R x + u *\<^sub>R (a + C *\<^sub>R (x - a)) \<in> s" and "0 \<le> u" "u \<le> 1"
+
−      have CC: "1 \<le> 1 + (C - 1) * u"
+
−        using \<open>x \<noteq> a\<close> \<open>0 \<le> u\<close>
+
−        apply (simp add: C_def divide_simps norm_minus_commute)
+
−        using Bx by auto
+
−      have *: "\<And>v. (1 - u) *\<^sub>R x + u *\<^sub>R (a + v *\<^sub>R (x - a)) = a + (1 + (v - 1) * u) *\<^sub>R (x - a)"
+
−        by (simp add: algebra_simps)
+
−      have "a + ((1 / (1 + C * u - u)) *\<^sub>R x + ((u / (1 + C * u - u)) *\<^sub>R a + (C * u / (1 + C * u - u)) *\<^sub>R x)) =
+
−            (1 + (u / (1 + C * u - u))) *\<^sub>R a + ((1 / (1 + C * u - u)) + (C * u / (1 + C * u - u))) *\<^sub>R x"
+
−        by (simp add: algebra_simps)
+
−      also have "\<dots> = (1 + (u / (1 + C * u - u))) *\<^sub>R a + (1 + (u / (1 + C * u - u))) *\<^sub>R x"
+
−        using CC by (simp add: field_simps)
+
−      also have "\<dots> = x + (1 + (u / (1 + C * u - u))) *\<^sub>R a + (u / (1 + C * u - u)) *\<^sub>R x"
+
−        by (simp add: algebra_simps)
+
−      also have "\<dots> = x + ((1 / (1 + C * u - u)) *\<^sub>R a +
+
−              ((u / (1 + C * u - u)) *\<^sub>R x + (C * u / (1 + C * u - u)) *\<^sub>R a))"
+
−        using CC by (simp add: field_simps) (simp add: add_divide_distrib scaleR_add_left)
+
−      finally have xeq: "(1 - 1 / (1 + (C - 1) * u)) *\<^sub>R a + (1 / (1 + (C - 1) * u)) *\<^sub>R (a + (1 + (C - 1) * u) *\<^sub>R (x - a)) = x"
+
−        by (simp add: algebra_simps)
+
−      have False
+
−        using \<open>convex s\<close>
+
−        apply (simp add: convex_alt)
+
−        apply (drule_tac x=a in bspec)
+
−         apply (rule  \<open>a \<in> s\<close>)
+
−        apply (drule_tac x="a + (1 + (C - 1) * u) *\<^sub>R (x - a)" in bspec)
+
−         using u apply (simp add: *)
+
−        apply (drule_tac x="1 / (1 + (C - 1) * u)" in spec)
+
−        using \<open>x \<noteq> a\<close> \<open>x \<notin> s\<close> \<open>0 \<le> u\<close> CC
+
−        apply (auto simp: xeq)
+
−        done
+
−    }
+
−    then have pcx: "path_component (- s) x (a + C *\<^sub>R (x - a))"
+
−      by (force simp: closed_segment_def intro!: path_connected_linepath)
+
−    define D where "D = B / norm(y - a)"  \<comment> \<open>massive duplication with the proof above\<close>
+
−    { fix u
+
−      assume u: "(1 - u) *\<^sub>R y + u *\<^sub>R (a + D *\<^sub>R (y - a)) \<in> s" and "0 \<le> u" "u \<le> 1"
+
−      have DD: "1 \<le> 1 + (D - 1) * u"
+
−        using \<open>y \<noteq> a\<close> \<open>0 \<le> u\<close>
+
−        apply (simp add: D_def divide_simps norm_minus_commute)
+
−        using By by auto
+
−      have *: "\<And>v. (1 - u) *\<^sub>R y + u *\<^sub>R (a + v *\<^sub>R (y - a)) = a + (1 + (v - 1) * u) *\<^sub>R (y - a)"
+
−        by (simp add: algebra_simps)
+
−      have "a + ((1 / (1 + D * u - u)) *\<^sub>R y + ((u / (1 + D * u - u)) *\<^sub>R a + (D * u / (1 + D * u - u)) *\<^sub>R y)) =
+
−            (1 + (u / (1 + D * u - u))) *\<^sub>R a + ((1 / (1 + D * u - u)) + (D * u / (1 + D * u - u))) *\<^sub>R y"
+
−        by (simp add: algebra_simps)
+
−      also have "\<dots> = (1 + (u / (1 + D * u - u))) *\<^sub>R a + (1 + (u / (1 + D * u - u))) *\<^sub>R y"
+
−        using DD by (simp add: field_simps)
+
−      also have "\<dots> = y + (1 + (u / (1 + D * u - u))) *\<^sub>R a + (u / (1 + D * u - u)) *\<^sub>R y"
+
−        by (simp add: algebra_simps)
+
−      also have "\<dots> = y + ((1 / (1 + D * u - u)) *\<^sub>R a +
+
−              ((u / (1 + D * u - u)) *\<^sub>R y + (D * u / (1 + D * u - u)) *\<^sub>R a))"
+
−        using DD by (simp add: field_simps) (simp add: add_divide_distrib scaleR_add_left)
+
−      finally have xeq: "(1 - 1 / (1 + (D - 1) * u)) *\<^sub>R a + (1 / (1 + (D - 1) * u)) *\<^sub>R (a + (1 + (D - 1) * u) *\<^sub>R (y - a)) = y"
+
−        by (simp add: algebra_simps)
+
−      have False
+
−        using \<open>convex s\<close>
+
−        apply (simp add: convex_alt)
+
−        apply (drule_tac x=a in bspec)
+
−         apply (rule  \<open>a \<in> s\<close>)
+
−        apply (drule_tac x="a + (1 + (D - 1) * u) *\<^sub>R (y - a)" in bspec)
+
−         using u apply (simp add: *)
+
−        apply (drule_tac x="1 / (1 + (D - 1) * u)" in spec)
+
−        using \<open>y \<noteq> a\<close> \<open>y \<notin> s\<close> \<open>0 \<le> u\<close> DD
+
−        apply (auto simp: xeq)
+
−        done
+
−    }
+
−    then have pdy: "path_component (- s) y (a + D *\<^sub>R (y - a))"
+
−      by (force simp: closed_segment_def intro!: path_connected_linepath)
+
−    have pyx: "path_component (- s) (a + D *\<^sub>R (y - a)) (a + C *\<^sub>R (x - a))"
+
−      apply (rule path_component_of_subset [of "sphere a B"])
+
−       using \<open>s \<subseteq> ball a B\<close>
+
−       apply (force simp: ball_def dist_norm norm_minus_commute)
+
−      apply (rule path_connected_sphere [OF 2, of a B, simplified path_connected_component, rule_format])
+
−       using \<open>x \<noteq> a\<close>  using \<open>y \<noteq> a\<close>  B apply (auto simp: dist_norm C_def D_def)
+
−      done
+
−    have "path_component (- s) x y"
+
−      by (metis path_component_trans path_component_sym pcx pdy pyx)
+
−  }
+
−  then show ?thesis
+
−    by (auto simp: path_connected_component)
+
−qed
+
−
+
−lemma connected_complement_bounded_convex:
+
−    fixes s :: "'a :: euclidean_space set"
+
−    assumes "bounded s" "convex s" "2 \<le> DIM('a)"
+
−      shows  "connected (- s)"
+
−  using path_connected_complement_bounded_convex [OF assms] path_connected_imp_connected by blast
+
−
+
−lemma connected_diff_ball:
+
−    fixes s :: "'a :: euclidean_space set"
+
−    assumes "connected s" "cball a r \<subseteq> s" "2 \<le> DIM('a)"
+
−      shows "connected (s - ball a r)"
+
−  apply (rule connected_diff_open_from_closed [OF ball_subset_cball])
+
−  using assms connected_sphere
+
−  apply (auto simp: cball_diff_eq_sphere dist_norm)
+
−  done
+
−
+
−proposition connected_open_delete:
+
−  assumes "open S" "connected S" and 2: "2 \<le> DIM('N::euclidean_space)"
+
−    shows "connected(S - {a::'N})"
+
−proof (cases "a \<in> S")
+
−  case True
+
−  with \<open>open S\<close> obtain \<epsilon> where "\<epsilon> > 0" and \<epsilon>: "cball a \<epsilon> \<subseteq> S"
+
−    using open_contains_cball_eq by blast
+
−  have "dist a (a + \<epsilon> *\<^sub>R (SOME i. i \<in> Basis)) = \<epsilon>"
+
−    by (simp add: dist_norm SOME_Basis \<open>0 < \<epsilon>\<close> less_imp_le)
+
−  with \<epsilon> have "\<Inter>{S - ball a r |r. 0 < r \<and> r < \<epsilon>} \<subseteq> {} \<Longrightarrow> False"
+
−    apply (drule_tac c="a + scaleR (\<epsilon>) ((SOME i. i \<in> Basis))" in subsetD)
+
−    by auto
+
−  then have nonemp: "(\<Inter>{S - ball a r |r. 0 < r \<and> r < \<epsilon>}) = {} \<Longrightarrow> False"
+
−    by auto
+
−  have con: "\<And>r. r < \<epsilon> \<Longrightarrow> connected (S - ball a r)"
+
−    using \<epsilon> by (force intro: connected_diff_ball [OF \<open>connected S\<close> _ 2])
+
−  have "x \<in> \<Union>{S - ball a r |r. 0 < r \<and> r < \<epsilon>}" if "x \<in> S - {a}" for x
+
−    apply (rule UnionI [of "S - ball a (min \<epsilon> (dist a x) / 2)"])
+
−     using that \<open>0 < \<epsilon>\<close> apply simp_all
+
−    apply (rule_tac x="min \<epsilon> (dist a x) / 2" in exI)
+
−    apply auto
+
−    done
+
−  then have "S - {a} = \<Union>{S - ball a r | r. 0 < r \<and> r < \<epsilon>}"
+
−    by auto
+
−  then show ?thesis
+
−    by (auto intro: connected_Union con dest!: nonemp)
+
−next
+
−  case False then show ?thesis
+
−    by (simp add: \<open>connected S\<close>)
+
−qed
+
−
+
−corollary path_connected_open_delete:
+
−  assumes "open S" "connected S" and 2: "2 \<le> DIM('N::euclidean_space)"
+
−    shows "path_connected(S - {a::'N})"
+
−by (simp add: assms connected_open_delete connected_open_path_connected open_delete)
+
−
+
−corollary path_connected_punctured_ball:
+
−   "2 \<le> DIM('N::euclidean_space) \<Longrightarrow> path_connected(ball a r - {a::'N})"
+
−by (simp add: path_connected_open_delete)
+
−
+
−corollary connected_punctured_ball:
+
−   "2 \<le> DIM('N::euclidean_space) \<Longrightarrow> connected(ball a r - {a::'N})"
+
−by (simp add: connected_open_delete)
+
−
+
−corollary connected_open_delete_finite:
+
−  fixes S T::"'a::euclidean_space set"
+
−  assumes S: "open S" "connected S" and 2: "2 \<le> DIM('a)" and "finite T"
+
−  shows "connected(S - T)"
+
−  using \<open>finite T\<close> S
+
−proof (induct T)
+
−  case empty
+
−  show ?case using \<open>connected S\<close> by simp
+
−next
+
−  case (insert x F)
+
−  then have "connected (S-F)" by auto
+
−  moreover have "open (S - F)" using finite_imp_closed[OF \<open>finite F\<close>] \<open>open S\<close> by auto
+
−  ultimately have "connected (S - F - {x})" using connected_open_delete[OF _ _ 2] by auto
+
−  thus ?case by (metis Diff_insert)
+
−qed
+
−
+
−lemma sphere_1D_doubleton_zero:
+
−  assumes 1: "DIM('a) = 1" and "r > 0"
+
−  obtains x y::"'a::euclidean_space"
+
−    where "sphere 0 r = {x,y} \<and> dist x y = 2*r"
+
−proof -
+
−  obtain b::'a where b: "Basis = {b}"
+
−    using 1 card_1_singletonE by blast
+
−  show ?thesis
+
−  proof (intro that conjI)
+
−    have "x = norm x *\<^sub>R b \<or> x = - norm x *\<^sub>R b" if "r = norm x" for x
+
−    proof -
+
−      have xb: "(x \<bullet> b) *\<^sub>R b = x"
+
−        using euclidean_representation [of x, unfolded b] by force
+
−      then have "norm ((x \<bullet> b) *\<^sub>R b) = norm x"
+
−        by simp
+
−      with b have "\<bar>x \<bullet> b\<bar> = norm x"
+
−        using norm_Basis by (simp add: b)
+
−      with xb show ?thesis
+
−        apply (simp add: abs_if split: if_split_asm)
+
−        apply (metis add.inverse_inverse real_vector.scale_minus_left xb)
+
−        done
+
−    qed
+
−    with \<open>r > 0\<close> b show "sphere 0 r = {r *\<^sub>R b, - r *\<^sub>R b}"
+
−      by (force simp: sphere_def dist_norm)
+
−    have "dist (r *\<^sub>R b) (- r *\<^sub>R b) = norm (r *\<^sub>R b + r *\<^sub>R b)"
+
−      by (simp add: dist_norm)
+
−    also have "\<dots> = norm ((2*r) *\<^sub>R b)"
+
−      by (metis mult_2 scaleR_add_left)
+
−    also have "\<dots> = 2*r"
+
−      using \<open>r > 0\<close> b norm_Basis by fastforce
+
−    finally show "dist (r *\<^sub>R b) (- r *\<^sub>R b) = 2*r" .
+
−  qed
+
−qed
+
−
+
−lemma sphere_1D_doubleton:
+
−  fixes a :: "'a :: euclidean_space"
+
−  assumes "DIM('a) = 1" and "r > 0"
+
−  obtains x y where "sphere a r = {x,y} \<and> dist x y = 2*r"
+
−proof -
+
−  have "sphere a r = (+) a ` sphere 0 r"
+
−    by (metis add.right_neutral sphere_translation)
+
−  then show ?thesis
+
−    using sphere_1D_doubleton_zero [OF assms]
+
−    by (metis (mono_tags, lifting) dist_add_cancel image_empty image_insert that)
+
−qed
+
−
+
−lemma psubset_sphere_Compl_connected:
+
−  fixes S :: "'a::euclidean_space set"
+
−  assumes S: "S \<subset> sphere a r" and "0 < r" and 2: "2 \<le> DIM('a)"
+
−  shows "connected(- S)"
+
−proof -
+
−  have "S \<subseteq> sphere a r"
+
−    using S by blast
+
−  obtain b where "dist a b = r" and "b \<notin> S"
+
−    using S mem_sphere by blast
+
−  have CS: "- S = {x. dist a x \<le> r \<and> (x \<notin> S)} \<union> {x. r \<le> dist a x \<and> (x \<notin> S)}"
+
−    by auto
+
−  have "{x. dist a x \<le> r \<and> x \<notin> S} \<inter> {x. r \<le> dist a x \<and> x \<notin> S} \<noteq> {}"
+
−    using \<open>b \<notin> S\<close> \<open>dist a b = r\<close> by blast
+
−  moreover have "connected {x. dist a x \<le> r \<and> x \<notin> S}"
+
−    apply (rule connected_intermediate_closure [of "ball a r"])
+
−    using assms by auto
+
−  moreover
+
−  have "connected {x. r \<le> dist a x \<and> x \<notin> S}"
+
−    apply (rule connected_intermediate_closure [of "- cball a r"])
+
−    using assms apply (auto intro: connected_complement_bounded_convex)
+
−    apply (metis ComplI interior_cball interior_closure mem_ball not_less)
+
−    done
+
−  ultimately show ?thesis
+
−    by (simp add: CS connected_Un)
+
−qed
+
−
+
−
+
−subsection\<open>Every annulus is a connected set\<close>
+
−
+
−lemma path_connected_2DIM_I:
+
−  fixes a :: "'N::euclidean_space"
+
−  assumes 2: "2 \<le> DIM('N)" and pc: "path_connected {r. 0 \<le> r \<and> P r}"
+
−  shows "path_connected {x. P(norm(x - a))}"
+
−proof -
+
−  have "{x. P(norm(x - a))} = (+) a ` {x. P(norm x)}"
+
−    by force
+
−  moreover have "path_connected {x::'N. P(norm x)}"
+
−  proof -
+
−    let ?D = "{x. 0 \<le> x \<and> P x} \<times> sphere (0::'N) 1"
+
−    have "x \<in> (\<lambda>z. fst z *\<^sub>R snd z) ` ?D"
+
−      if "P (norm x)" for x::'N
+
−    proof (cases "x=0")
+
−      case True
+
−      with that show ?thesis
+
−        apply (simp add: image_iff)
+
−        apply (rule_tac x=0 in exI, simp)
+
−        using vector_choose_size zero_le_one by blast
+
−    next
+
−      case False
+
−      with that show ?thesis
+
−        by (rule_tac x="(norm x, x /\<^sub>R norm x)" in image_eqI) auto
+
−    qed
+
−    then have *: "{x::'N. P(norm x)} =  (\<lambda>z. fst z *\<^sub>R snd z) ` ?D"
+
−      by auto
+
−    have "continuous_on ?D (\<lambda>z:: real\<times>'N. fst z *\<^sub>R snd z)"
+
−      by (intro continuous_intros)
+
−    moreover have "path_connected ?D"
+
−      by (metis path_connected_Times [OF pc] path_connected_sphere 2)
+
−    ultimately show ?thesis
+
−      apply (subst *)
+
−      apply (rule path_connected_continuous_image, auto)
+
−      done
+
−  qed
+
−  ultimately show ?thesis
+
−    using path_connected_translation by metis
+
−qed
+
−
+
−proposition path_connected_annulus:
+
−  fixes a :: "'N::euclidean_space"
+
−  assumes "2 \<le> DIM('N)"
+
−  shows "path_connected {x. r1 < norm(x - a) \<and> norm(x - a) < r2}"
+
−        "path_connected {x. r1 < norm(x - a) \<and> norm(x - a) \<le> r2}"
+
−        "path_connected {x. r1 \<le> norm(x - a) \<and> norm(x - a) < r2}"
+
−        "path_connected {x. r1 \<le> norm(x - a) \<and> norm(x - a) \<le> r2}"
+
−  by (auto simp: is_interval_def intro!: is_interval_convex convex_imp_path_connected path_connected_2DIM_I [OF assms])
+
−
+
−proposition connected_annulus:
+
−  fixes a :: "'N::euclidean_space"
+
−  assumes "2 \<le> DIM('N::euclidean_space)"
+
−  shows "connected {x. r1 < norm(x - a) \<and> norm(x - a) < r2}"
+
−        "connected {x. r1 < norm(x - a) \<and> norm(x - a) \<le> r2}"
+
−        "connected {x. r1 \<le> norm(x - a) \<and> norm(x - a) < r2}"
+
−        "connected {x. r1 \<le> norm(x - a) \<and> norm(x - a) \<le> r2}"
+
−  by (auto simp: path_connected_annulus [OF assms] path_connected_imp_connected)
+
−
+
−
+
−subsection%unimportant\<open>Relations between components and path components\<close>
+
−
+
−lemma open_connected_component:
+
−  fixes s :: "'a::real_normed_vector set"
+
−  shows "open s \<Longrightarrow> open (connected_component_set s x)"
+
−    apply (simp add: open_contains_ball, clarify)
+
−    apply (rename_tac y)
+
−    apply (drule_tac x=y in bspec)
+
−     apply (simp add: connected_component_in, clarify)
+
−    apply (rule_tac x=e in exI)
+
−    by (metis mem_Collect_eq connected_component_eq connected_component_maximal centre_in_ball connected_ball)
+
−
+
−corollary open_components:
+
−    fixes s :: "'a::real_normed_vector set"
+
−    shows "\<lbrakk>open u; s \<in> components u\<rbrakk> \<Longrightarrow> open s"
+
−  by (simp add: components_iff) (metis open_connected_component)
+
−
+
−lemma in_closure_connected_component:
+
−  fixes s :: "'a::real_normed_vector set"
+
−  assumes x: "x \<in> s" and s: "open s"
+
−  shows "x \<in> closure (connected_component_set s y) \<longleftrightarrow>  x \<in> connected_component_set s y"
+
−proof -
+
−  { assume "x \<in> closure (connected_component_set s y)"
+
−    moreover have "x \<in> connected_component_set s x"
+
−      using x by simp
+
−    ultimately have "x \<in> connected_component_set s y"
+
−      using s by (meson Compl_disjoint closure_iff_nhds_not_empty connected_component_disjoint disjoint_eq_subset_Compl open_connected_component)
+
−  }
+
−  then show ?thesis
+
−    by (auto simp: closure_def)
+
−qed
+
−
+
−lemma connected_disjoint_Union_open_pick:
+
−  assumes "pairwise disjnt B"
+
−          "\<And>S. S \<in> A \<Longrightarrow> connected S \<and> S \<noteq> {}"
+
−          "\<And>S. S \<in> B \<Longrightarrow> open S"
+
−          "\<Union>A \<subseteq> \<Union>B"
+
−          "S \<in> A"
+
−  obtains T where "T \<in> B" "S \<subseteq> T" "S \<inter> \<Union>(B - {T}) = {}"
+
−proof -
+
−  have "S \<subseteq> \<Union>B" "connected S" "S \<noteq> {}"
+
−    using assms \<open>S \<in> A\<close> by blast+
+
−  then obtain T where "T \<in> B" "S \<inter> T \<noteq> {}"
+
−    by (metis Sup_inf_eq_bot_iff inf.absorb_iff2 inf_commute)
+
−  have 1: "open T" by (simp add: \<open>T \<in> B\<close> assms)
+
−  have 2: "open (\<Union>(B-{T}))" using assms by blast
+
−  have 3: "S \<subseteq> T \<union> \<Union>(B - {T})" using \<open>S \<subseteq> \<Union>B\<close> by blast
+
−  have "T \<inter> \<Union>(B - {T}) = {}" using \<open>T \<in> B\<close> \<open>pairwise disjnt B\<close>
+
−    by (auto simp: pairwise_def disjnt_def)
+
−  then have 4: "T \<inter> \<Union>(B - {T}) \<inter> S = {}" by auto
+
−  from connectedD [OF \<open>connected S\<close> 1 2 3 4]
+
−  have "S \<inter> \<Union>(B-{T}) = {}"
+
−    by (auto simp: Int_commute \<open>S \<inter> T \<noteq> {}\<close>)
+
−  with \<open>T \<in> B\<close> have "S \<subseteq> T"
+
−    using "3" by auto
+
−  show ?thesis
+
−    using \<open>S \<inter> \<Union>(B - {T}) = {}\<close> \<open>S \<subseteq> T\<close> \<open>T \<in> B\<close> that by auto
+
−qed
+
−
+
−lemma connected_disjoint_Union_open_subset:
+
−  assumes A: "pairwise disjnt A" and B: "pairwise disjnt B"
+
−      and SA: "\<And>S. S \<in> A \<Longrightarrow> open S \<and> connected S \<and> S \<noteq> {}"
+
−      and SB: "\<And>S. S \<in> B \<Longrightarrow> open S \<and> connected S \<and> S \<noteq> {}"
+
−      and eq [simp]: "\<Union>A = \<Union>B"
+
−    shows "A \<subseteq> B"
+
−proof
+
−  fix S
+
−  assume "S \<in> A"
+
−  obtain T where "T \<in> B" "S \<subseteq> T" "S \<inter> \<Union>(B - {T}) = {}"
+
−      apply (rule connected_disjoint_Union_open_pick [OF B, of A])
+
−      using SA SB \<open>S \<in> A\<close> by auto
+
−  moreover obtain S' where "S' \<in> A" "T \<subseteq> S'" "T \<inter> \<Union>(A - {S'}) = {}"
+
−      apply (rule connected_disjoint_Union_open_pick [OF A, of B])
+
−      using SA SB \<open>T \<in> B\<close> by auto
+
−  ultimately have "S' = S"
+
−    by (metis A Int_subset_iff SA \<open>S \<in> A\<close> disjnt_def inf.orderE pairwise_def)
+
−  with \<open>T \<subseteq> S'\<close> have "T \<subseteq> S" by simp
+
−  with \<open>S \<subseteq> T\<close> have "S = T" by blast
+
−  with \<open>T \<in> B\<close> show "S \<in> B" by simp
+
−qed
+
−
+
−lemma connected_disjoint_Union_open_unique:
+
−  assumes A: "pairwise disjnt A" and B: "pairwise disjnt B"
+
−      and SA: "\<And>S. S \<in> A \<Longrightarrow> open S \<and> connected S \<and> S \<noteq> {}"
+
−      and SB: "\<And>S. S \<in> B \<Longrightarrow> open S \<and> connected S \<and> S \<noteq> {}"
+
−      and eq [simp]: "\<Union>A = \<Union>B"
+
−    shows "A = B"
+
−by (rule subset_antisym; metis connected_disjoint_Union_open_subset assms)
+
−
+
−proposition components_open_unique:
+
− fixes S :: "'a::real_normed_vector set"
+
−  assumes "pairwise disjnt A" "\<Union>A = S"
+
−          "\<And>X. X \<in> A \<Longrightarrow> open X \<and> connected X \<and> X \<noteq> {}"
+
−    shows "components S = A"
+
−proof -
+
−  have "open S" using assms by blast
+
−  show ?thesis
+
−    apply (rule connected_disjoint_Union_open_unique)
+
−    apply (simp add: components_eq disjnt_def pairwise_def)
+
−    using \<open>open S\<close>
+
−    apply (simp_all add: assms open_components in_components_connected in_components_nonempty)
+
−    done
+
−qed
+
−
+
−
+
−subsection%unimportant\<open>Existence of unbounded components\<close>
+
−
+
−lemma cobounded_unbounded_component:
+
−    fixes s :: "'a :: euclidean_space set"
+
−    assumes "bounded (-s)"
+
−      shows "\<exists>x. x \<in> s \<and> \<not> bounded (connected_component_set s x)"
+
−proof -
+
−  obtain i::'a where i: "i \<in> Basis"
+
−    using nonempty_Basis by blast
+
−  obtain B where B: "B>0" "-s \<subseteq> ball 0 B"
+
−    using bounded_subset_ballD [OF assms, of 0] by auto
+
−  then have *: "\<And>x. B \<le> norm x \<Longrightarrow> x \<in> s"
+
−    by (force simp: ball_def dist_norm)
+
−  have unbounded_inner: "\<not> bounded {x. inner i x \<ge> B}"
+
−    apply (auto simp: bounded_def dist_norm)
+
−    apply (rule_tac x="x + (max B e + 1 + \<bar>i \<bullet> x\<bar>) *\<^sub>R i" in exI)
+
−    apply simp
+
−    using i
+
−    apply (auto simp: algebra_simps)
+
−    done
+
−  have **: "{x. B \<le> i \<bullet> x} \<subseteq> connected_component_set s (B *\<^sub>R i)"
+
−    apply (rule connected_component_maximal)
+
−    apply (auto simp: i intro: convex_connected convex_halfspace_ge [of B])
+
−    apply (rule *)
+
−    apply (rule order_trans [OF _ Basis_le_norm [OF i]])
+
−    by (simp add: inner_commute)
+
−  have "B *\<^sub>R i \<in> s"
+
−    by (rule *) (simp add: norm_Basis [OF i])
+
−  then show ?thesis
+
−    apply (rule_tac x="B *\<^sub>R i" in exI, clarify)
+
−    apply (frule bounded_subset [of _ "{x. B \<le> i \<bullet> x}", OF _ **])
+
−    using unbounded_inner apply blast
+
−    done
+
−qed
+
−
+
−lemma cobounded_unique_unbounded_component:
+
−    fixes s :: "'a :: euclidean_space set"
+
−    assumes bs: "bounded (-s)" and "2 \<le> DIM('a)"
+
−        and bo: "\<not> bounded(connected_component_set s x)"
+
−                "\<not> bounded(connected_component_set s y)"
+
−      shows "connected_component_set s x = connected_component_set s y"
+
−proof -
+
−  obtain i::'a where i: "i \<in> Basis"
+
−    using nonempty_Basis by blast
+
−  obtain B where B: "B>0" "-s \<subseteq> ball 0 B"
+
−    using bounded_subset_ballD [OF bs, of 0] by auto
+
−  then have *: "\<And>x. B \<le> norm x \<Longrightarrow> x \<in> s"
+
−    by (force simp: ball_def dist_norm)
+
−  have ccb: "connected (- ball 0 B :: 'a set)"
+
−    using assms by (auto intro: connected_complement_bounded_convex)
+
−  obtain x' where x': "connected_component s x x'" "norm x' > B"
+
−    using bo [unfolded bounded_def dist_norm, simplified, rule_format]
+
−    by (metis diff_zero norm_minus_commute not_less)
+
−  obtain y' where y': "connected_component s y y'" "norm y' > B"
+
−    using bo [unfolded bounded_def dist_norm, simplified, rule_format]
+
−    by (metis diff_zero norm_minus_commute not_less)
+
−  have x'y': "connected_component s x' y'"
+
−    apply (simp add: connected_component_def)
+
−    apply (rule_tac x="- ball 0 B" in exI)
+
−    using x' y'
+
−    apply (auto simp: ccb dist_norm *)
+
−    done
+
−  show ?thesis
+
−    apply (rule connected_component_eq)
+
−    using x' y' x'y'
+
−    by (metis (no_types, lifting) connected_component_eq_empty connected_component_eq_eq connected_component_idemp connected_component_in)
+
−qed
+
−
+
−lemma cobounded_unbounded_components:
+
−    fixes s :: "'a :: euclidean_space set"
+
−    shows "bounded (-s) \<Longrightarrow> \<exists>c. c \<in> components s \<and> \<not>bounded c"
+
−  by (metis cobounded_unbounded_component components_def imageI)
+
−
+
−lemma cobounded_unique_unbounded_components:
+
−    fixes s :: "'a :: euclidean_space set"
+
−    shows  "\<lbrakk>bounded (- s); c \<in> components s; \<not> bounded c; c' \<in> components s; \<not> bounded c'; 2 \<le> DIM('a)\<rbrakk> \<Longrightarrow> c' = c"
+
−  unfolding components_iff
+
−  by (metis cobounded_unique_unbounded_component)
+
−
+
−lemma cobounded_has_bounded_component:
+
−  fixes S :: "'a :: euclidean_space set"
+
−  assumes "bounded (- S)" "\<not> connected S" "2 \<le> DIM('a)"
+
−  obtains C where "C \<in> components S" "bounded C"
+
−  by (meson cobounded_unique_unbounded_components connected_eq_connected_components_eq assms)
+
−
+
−
+
−subsection\<open>The \<open>inside\<close> and \<open>outside\<close> of a Set\<close>
+
−
+
−text%important\<open>The inside comprises the points in a bounded connected component of the set's complement.
+
−  The outside comprises the points in unbounded connected component of the complement.\<close>
+
−
+
−definition%important inside where
+
−  "inside S \<equiv> {x. (x \<notin> S) \<and> bounded(connected_component_set ( - S) x)}"
+
−
+
−definition%important outside where
+
−  "outside S \<equiv> -S \<inter> {x. \<not> bounded(connected_component_set (- S) x)}"
+
−
+
−lemma outside: "outside S = {x. \<not> bounded(connected_component_set (- S) x)}"
+
−  by (auto simp: outside_def) (metis Compl_iff bounded_empty connected_component_eq_empty)
+
−
+
−lemma inside_no_overlap [simp]: "inside S \<inter> S = {}"
+
−  by (auto simp: inside_def)
+
−
+
−lemma outside_no_overlap [simp]:
+
−   "outside S \<inter> S = {}"
+
−  by (auto simp: outside_def)
+
−
+
−lemma inside_Int_outside [simp]: "inside S \<inter> outside S = {}"
+
−  by (auto simp: inside_def outside_def)
+
−
+
−lemma inside_Un_outside [simp]: "inside S \<union> outside S = (- S)"
+
−  by (auto simp: inside_def outside_def)
+
−
+
−lemma inside_eq_outside:
+
−   "inside S = outside S \<longleftrightarrow> S = UNIV"
+
−  by (auto simp: inside_def outside_def)
+
−
+
−lemma inside_outside: "inside S = (- (S \<union> outside S))"
+
−  by (force simp: inside_def outside)
+
−
+
−lemma outside_inside: "outside S = (- (S \<union> inside S))"
+
−  by (auto simp: inside_outside) (metis IntI equals0D outside_no_overlap)
+
−
+
−lemma union_with_inside: "S \<union> inside S = - outside S"
+
−  by (auto simp: inside_outside) (simp add: outside_inside)
+
−
+
−lemma union_with_outside: "S \<union> outside S = - inside S"
+
−  by (simp add: inside_outside)
+
−
+
−lemma outside_mono: "S \<subseteq> T \<Longrightarrow> outside T \<subseteq> outside S"
+
−  by (auto simp: outside bounded_subset connected_component_mono)
+
−
+
−lemma inside_mono: "S \<subseteq> T \<Longrightarrow> inside S - T \<subseteq> inside T"
+
−  by (auto simp: inside_def bounded_subset connected_component_mono)
+
−
+
−lemma segment_bound_lemma:
+
−  fixes u::real
+
−  assumes "x \<ge> B" "y \<ge> B" "0 \<le> u" "u \<le> 1"
+
−  shows "(1 - u) * x + u * y \<ge> B"
+
−proof -
+
−  obtain dx dy where "dx \<ge> 0" "dy \<ge> 0" "x = B + dx" "y = B + dy"
+
−    using assms by auto (metis add.commute diff_add_cancel)
+
−  with \<open>0 \<le> u\<close> \<open>u \<le> 1\<close> show ?thesis
+
−    by (simp add: add_increasing2 mult_left_le field_simps)
+
−qed
+
−
+
−lemma cobounded_outside:
+
−  fixes S :: "'a :: real_normed_vector set"
+
−  assumes "bounded S" shows "bounded (- outside S)"
+
−proof -
+
−  obtain B where B: "B>0" "S \<subseteq> ball 0 B"
+
−    using bounded_subset_ballD [OF assms, of 0] by auto
+
−  { fix x::'a and C::real
+
−    assume Bno: "B \<le> norm x" and C: "0 < C"
+
−    have "\<exists>y. connected_component (- S) x y \<and> norm y > C"
+
−    proof (cases "x = 0")
+
−      case True with B Bno show ?thesis by force
+
−    next
+
−      case False 
+
−      with B C
+
−      have "closed_segment x (((B + C) / norm x) *\<^sub>R x) \<subseteq> - ball 0 B"
+
−        apply (clarsimp simp add: closed_segment_def ball_def dist_norm real_vector_class.scaleR_add_left [symmetric] divide_simps)
+
−        using segment_bound_lemma [of B "norm x" "B+C" ] Bno
+
−        by (meson le_add_same_cancel1 less_eq_real_def not_le)
+
−      also have "... \<subseteq> -S"
+
−        by (simp add: B)
+
−      finally have "\<exists>T. connected T \<and> T \<subseteq> - S \<and> x \<in> T \<and> ((B + C) / norm x) *\<^sub>R x \<in> T"
+
−        by (rule_tac x="closed_segment x (((B+C)/norm x) *\<^sub>R x)" in exI) simp
+
−      with False B
+
−      show ?thesis
+
−        by (rule_tac x="((B+C)/norm x) *\<^sub>R x" in exI) (simp add: connected_component_def)
+
−    qed
+
−  }
+
−  then show ?thesis
+
−    apply (simp add: outside_def assms)
+
−    apply (rule bounded_subset [OF bounded_ball [of 0 B]])
+
−    apply (force simp: dist_norm not_less bounded_pos)
+
−    done
+
−qed
+
−
+
−lemma unbounded_outside:
+
−    fixes S :: "'a::{real_normed_vector, perfect_space} set"
+
−    shows "bounded S \<Longrightarrow> \<not> bounded(outside S)"
+
−  using cobounded_imp_unbounded cobounded_outside by blast
+
−
+
−lemma bounded_inside:
+
−    fixes S :: "'a::{real_normed_vector, perfect_space} set"
+
−    shows "bounded S \<Longrightarrow> bounded(inside S)"
+
−  by (simp add: bounded_Int cobounded_outside inside_outside)
+
−
+
−lemma connected_outside:
+
−    fixes S :: "'a::euclidean_space set"
+
−    assumes "bounded S" "2 \<le> DIM('a)"
+
−      shows "connected(outside S)"
+
−  apply (clarsimp simp add: connected_iff_connected_component outside)
+
−  apply (rule_tac s="connected_component_set (- S) x" in connected_component_of_subset)
+
−  apply (metis (no_types) assms cobounded_unbounded_component cobounded_unique_unbounded_component connected_component_eq_eq connected_component_idemp double_complement mem_Collect_eq)
+
−  apply clarify
+
−  apply (metis connected_component_eq_eq connected_component_in)
+
−  done
+
−
+
−lemma outside_connected_component_lt:
+
−    "outside S = {x. \<forall>B. \<exists>y. B < norm(y) \<and> connected_component (- S) x y}"
+
−apply (auto simp: outside bounded_def dist_norm)
+
−apply (metis diff_0 norm_minus_cancel not_less)
+
−by (metis less_diff_eq norm_minus_commute norm_triangle_ineq2 order.trans pinf(6))
+
−
+
−lemma outside_connected_component_le:
+
−   "outside S =
+
−            {x. \<forall>B. \<exists>y. B \<le> norm(y) \<and>
+
−                         connected_component (- S) x y}"
+
−apply (simp add: outside_connected_component_lt)
+
−apply (simp add: Set.set_eq_iff)
+
−by (meson gt_ex leD le_less_linear less_imp_le order.trans)
+
−
+
−lemma not_outside_connected_component_lt:
+
−    fixes S :: "'a::euclidean_space set"
+
−    assumes S: "bounded S" and "2 \<le> DIM('a)"
+
−      shows "- (outside S) = {x. \<forall>B. \<exists>y. B < norm(y) \<and> \<not> connected_component (- S) x y}"
+
−proof -
+
−  obtain B::real where B: "0 < B" and Bno: "\<And>x. x \<in> S \<Longrightarrow> norm x \<le> B"
+
−    using S [simplified bounded_pos] by auto
+
−  { fix y::'a and z::'a
+
−    assume yz: "B < norm z" "B < norm y"
+
−    have "connected_component (- cball 0 B) y z"
+
−      apply (rule connected_componentI [OF _ subset_refl])
+
−      apply (rule connected_complement_bounded_convex)
+
−      using assms yz
+
−      by (auto simp: dist_norm)
+
−    then have "connected_component (- S) y z"
+
−      apply (rule connected_component_of_subset)
+
−      apply (metis Bno Compl_anti_mono mem_cball_0 subset_iff)
+
−      done
+
−  } note cyz = this
+
−  show ?thesis
+
−    apply (auto simp: outside)
+
−    apply (metis Compl_iff bounded_iff cobounded_imp_unbounded mem_Collect_eq not_le)
+
−    apply (simp add: bounded_pos)
+
−    by (metis B connected_component_trans cyz not_le)
+
−qed
+
−
+
−lemma not_outside_connected_component_le:
+
−    fixes S :: "'a::euclidean_space set"
+
−    assumes S: "bounded S"  "2 \<le> DIM('a)"
+
−      shows "- (outside S) = {x. \<forall>B. \<exists>y. B \<le> norm(y) \<and> \<not> connected_component (- S) x y}"
+
−apply (auto intro: less_imp_le simp: not_outside_connected_component_lt [OF assms])
+
−by (meson gt_ex less_le_trans)
+
−
+
−lemma inside_connected_component_lt:
+
−    fixes S :: "'a::euclidean_space set"
+
−    assumes S: "bounded S"  "2 \<le> DIM('a)"
+
−      shows "inside S = {x. (x \<notin> S) \<and> (\<forall>B. \<exists>y. B < norm(y) \<and> \<not> connected_component (- S) x y)}"
+
−  by (auto simp: inside_outside not_outside_connected_component_lt [OF assms])
+
−
+
−lemma inside_connected_component_le:
+
−    fixes S :: "'a::euclidean_space set"
+
−    assumes S: "bounded S"  "2 \<le> DIM('a)"
+
−      shows "inside S = {x. (x \<notin> S) \<and> (\<forall>B. \<exists>y. B \<le> norm(y) \<and> \<not> connected_component (- S) x y)}"
+
−  by (auto simp: inside_outside not_outside_connected_component_le [OF assms])
+
−
+
−lemma inside_subset:
+
−  assumes "connected U" and "\<not> bounded U" and "T \<union> U = - S"
+
−  shows "inside S \<subseteq> T"
+
−apply (auto simp: inside_def)
+
−by (metis bounded_subset [of "connected_component_set (- S) _"] connected_component_maximal
+
−       Compl_iff Un_iff assms subsetI)
+
−
+
−lemma frontier_not_empty:
+
−  fixes S :: "'a :: real_normed_vector set"
+
−  shows "\<lbrakk>S \<noteq> {}; S \<noteq> UNIV\<rbrakk> \<Longrightarrow> frontier S \<noteq> {}"
+
−    using connected_Int_frontier [of UNIV S] by auto
+
−
+
−lemma frontier_eq_empty:
+
−  fixes S :: "'a :: real_normed_vector set"
+
−  shows "frontier S = {} \<longleftrightarrow> S = {} \<or> S = UNIV"
+
−using frontier_UNIV frontier_empty frontier_not_empty by blast
+
−
+
−lemma frontier_of_connected_component_subset:
+
−  fixes S :: "'a::real_normed_vector set"
+
−  shows "frontier(connected_component_set S x) \<subseteq> frontier S"
+
−proof -
+
−  { fix y
+
−    assume y1: "y \<in> closure (connected_component_set S x)"
+
−       and y2: "y \<notin> interior (connected_component_set S x)"
+
−    have "y \<in> closure S"
+
−      using y1 closure_mono connected_component_subset by blast
+
−    moreover have "z \<in> interior (connected_component_set S x)"
+
−          if "0 < e" "ball y e \<subseteq> interior S" "dist y z < e" for e z
+
−    proof -
+
−      have "ball y e \<subseteq> connected_component_set S y"
+
−        apply (rule connected_component_maximal)
+
−        using that interior_subset mem_ball apply auto
+
−        done
+
−      then show ?thesis
+
−        using y1 apply (simp add: closure_approachable open_contains_ball_eq [OF open_interior])
+
−        by (metis connected_component_eq dist_commute mem_Collect_eq mem_ball mem_interior subsetD \<open>0 < e\<close> y2)
+
−    qed
+
−    then have "y \<notin> interior S"
+
−      using y2 by (force simp: open_contains_ball_eq [OF open_interior])
+
−    ultimately have "y \<in> frontier S"
+
−      by (auto simp: frontier_def)
+
−  }
+
−  then show ?thesis by (auto simp: frontier_def)
+
−qed
+
−
+
−lemma frontier_Union_subset_closure:
+
−  fixes F :: "'a::real_normed_vector set set"
+
−  shows "frontier(\<Union>F) \<subseteq> closure(\<Union>t \<in> F. frontier t)"
+
−proof -
+
−  have "\<exists>y\<in>F. \<exists>y\<in>frontier y. dist y x < e"
+
−       if "T \<in> F" "y \<in> T" "dist y x < e"
+
−          "x \<notin> interior (\<Union>F)" "0 < e" for x y e T
+
−  proof (cases "x \<in> T")
+
−    case True with that show ?thesis
+
−      by (metis Diff_iff Sup_upper closure_subset contra_subsetD dist_self frontier_def interior_mono)
+
−  next
+
−    case False
+
−    have 1: "closed_segment x y \<inter> T \<noteq> {}" using \<open>y \<in> T\<close> by blast
+
−    have 2: "closed_segment x y - T \<noteq> {}"
+
−      using False by blast
+
−    obtain c where "c \<in> closed_segment x y" "c \<in> frontier T"
+
−       using False connected_Int_frontier [OF connected_segment 1 2] by auto
+
−    then show ?thesis
+
−    proof -
+
−      have "norm (y - x) < e"
+
−        by (metis dist_norm \<open>dist y x < e\<close>)
+
−      moreover have "norm (c - x) \<le> norm (y - x)"
+
−        by (simp add: \<open>c \<in> closed_segment x y\<close> segment_bound(1))
+
−      ultimately have "norm (c - x) < e"
+
−        by linarith
+
−      then show ?thesis
+
−        by (metis (no_types) \<open>c \<in> frontier T\<close> dist_norm that(1))
+
−    qed
+
−  qed
+
−  then show ?thesis
+
−    by (fastforce simp add: frontier_def closure_approachable)
+
−qed
+
−
+
−lemma frontier_Union_subset:
+
−  fixes F :: "'a::real_normed_vector set set"
+
−  shows "finite F \<Longrightarrow> frontier(\<Union>F) \<subseteq> (\<Union>t \<in> F. frontier t)"
+
−by (rule order_trans [OF frontier_Union_subset_closure])
+
−   (auto simp: closure_subset_eq)
+
−
+
−lemma frontier_of_components_subset:
+
−  fixes S :: "'a::real_normed_vector set"
+
−  shows "C \<in> components S \<Longrightarrow> frontier C \<subseteq> frontier S"
+
−  by (metis Path_Connected.frontier_of_connected_component_subset components_iff)
+
−
+
−lemma frontier_of_components_closed_complement:
+
−  fixes S :: "'a::real_normed_vector set"
+
−  shows "\<lbrakk>closed S; C \<in> components (- S)\<rbrakk> \<Longrightarrow> frontier C \<subseteq> S"
+
−  using frontier_complement frontier_of_components_subset frontier_subset_eq by blast
+
−
+
−lemma frontier_minimal_separating_closed:
+
−  fixes S :: "'a::real_normed_vector set"
+
−  assumes "closed S"
+
−      and nconn: "\<not> connected(- S)"
+
−      and C: "C \<in> components (- S)"
+
−      and conn: "\<And>T. \<lbrakk>closed T; T \<subset> S\<rbrakk> \<Longrightarrow> connected(- T)"
+
−    shows "frontier C = S"
+
−proof (rule ccontr)
+
−  assume "frontier C \<noteq> S"
+
−  then have "frontier C \<subset> S"
+
−    using frontier_of_components_closed_complement [OF \<open>closed S\<close> C] by blast
+
−  then have "connected(- (frontier C))"
+
−    by (simp add: conn)
+
−  have "\<not> connected(- (frontier C))"
+
−    unfolding connected_def not_not
+
−  proof (intro exI conjI)
+
−    show "open C"
+
−      using C \<open>closed S\<close> open_components by blast
+
−    show "open (- closure C)"
+
−      by blast
+
−    show "C \<inter> - closure C \<inter> - frontier C = {}"
+
−      using closure_subset by blast
+
−    show "C \<inter> - frontier C \<noteq> {}"
+
−      using C \<open>open C\<close> components_eq frontier_disjoint_eq by fastforce
+
−    show "- frontier C \<subseteq> C \<union> - closure C"
+
−      by (simp add: \<open>open C\<close> closed_Compl frontier_closures)
+
−    then show "- closure C \<inter> - frontier C \<noteq> {}"
+
−      by (metis (no_types, lifting) C Compl_subset_Compl_iff \<open>frontier C \<subset> S\<close> compl_sup frontier_closures in_components_subset psubsetE sup.absorb_iff2 sup.boundedE sup_bot.right_neutral sup_inf_absorb)
+
−  qed
+
−  then show False
+
−    using \<open>connected (- frontier C)\<close> by blast
+
−qed
+
−
+
−lemma connected_component_UNIV [simp]:
+
−    fixes x :: "'a::real_normed_vector"
+
−    shows "connected_component_set UNIV x = UNIV"
+
−using connected_iff_eq_connected_component_set [of "UNIV::'a set"] connected_UNIV
+
−by auto
+
−
+
−lemma connected_component_eq_UNIV:
+
−    fixes x :: "'a::real_normed_vector"
+
−    shows "connected_component_set s x = UNIV \<longleftrightarrow> s = UNIV"
+
−  using connected_component_in connected_component_UNIV by blast
+
−
+
−lemma components_UNIV [simp]: "components UNIV = {UNIV :: 'a::real_normed_vector set}"
+
−  by (auto simp: components_eq_sing_iff)
+
−
+
−lemma interior_inside_frontier:
+
−    fixes s :: "'a::real_normed_vector set"
+
−    assumes "bounded s"
+
−      shows "interior s \<subseteq> inside (frontier s)"
+
−proof -
+
−  { fix x y
+
−    assume x: "x \<in> interior s" and y: "y \<notin> s"
+
−       and cc: "connected_component (- frontier s) x y"
+
−    have "connected_component_set (- frontier s) x \<inter> frontier s \<noteq> {}"
+
−      apply (rule connected_Int_frontier, simp)
+
−      apply (metis IntI cc connected_component_in connected_component_refl empty_iff interiorE mem_Collect_eq rev_subsetD x)
+
−      using  y cc
+
−      by blast
+
−    then have "bounded (connected_component_set (- frontier s) x)"
+
−      using connected_component_in by auto
+
−  }
+
−  then show ?thesis
+
−    apply (auto simp: inside_def frontier_def)
+
−    apply (rule classical)
+
−    apply (rule bounded_subset [OF assms], blast)
+
−    done
+
−qed
+
−
+
−lemma inside_empty [simp]: "inside {} = ({} :: 'a :: {real_normed_vector, perfect_space} set)"
+
−  by (simp add: inside_def connected_component_UNIV)
+
−
+
−lemma outside_empty [simp]: "outside {} = (UNIV :: 'a :: {real_normed_vector, perfect_space} set)"
+
−using inside_empty inside_Un_outside by blast
+
−
+
−lemma inside_same_component:
+
−   "\<lbrakk>connected_component (- s) x y; x \<in> inside s\<rbrakk> \<Longrightarrow> y \<in> inside s"
+
−  using connected_component_eq connected_component_in
+
−  by (fastforce simp add: inside_def)
+
−
+
−lemma outside_same_component:
+
−   "\<lbrakk>connected_component (- s) x y; x \<in> outside s\<rbrakk> \<Longrightarrow> y \<in> outside s"
+
−  using connected_component_eq connected_component_in
+
−  by (fastforce simp add: outside_def)
+
−
+
−lemma convex_in_outside:
+
−  fixes s :: "'a :: {real_normed_vector, perfect_space} set"
+
−  assumes s: "convex s" and z: "z \<notin> s"
+
−    shows "z \<in> outside s"
+
−proof (cases "s={}")
+
−  case True then show ?thesis by simp
+
−next
+
−  case False then obtain a where "a \<in> s" by blast
+
−  with z have zna: "z \<noteq> a" by auto
+
−  { assume "bounded (connected_component_set (- s) z)"
+
−    with bounded_pos_less obtain B where "B>0" and B: "\<And>x. connected_component (- s) z x \<Longrightarrow> norm x < B"
+
−      by (metis mem_Collect_eq)
+
−    define C where "C = (B + 1 + norm z) / norm (z-a)"
+
−    have "C > 0"
+
−      using \<open>0 < B\<close> zna by (simp add: C_def divide_simps add_strict_increasing)
+
−    have "\<bar>norm (z + C *\<^sub>R (z-a)) - norm (C *\<^sub>R (z-a))\<bar> \<le> norm z"
+
−      by (metis add_diff_cancel norm_triangle_ineq3)
+
−    moreover have "norm (C *\<^sub>R (z-a)) > norm z + B"
+
−      using zna \<open>B>0\<close> by (simp add: C_def le_max_iff_disj field_simps)
+
−    ultimately have C: "norm (z + C *\<^sub>R (z-a)) > B" by linarith
+
−    { fix u::real
+
−      assume u: "0\<le>u" "u\<le>1" and ins: "(1 - u) *\<^sub>R z + u *\<^sub>R (z + C *\<^sub>R (z - a)) \<in> s"
+
−      then have Cpos: "1 + u * C > 0"
+
−        by (meson \<open>0 < C\<close> add_pos_nonneg less_eq_real_def zero_le_mult_iff zero_less_one)
+
−      then have *: "(1 / (1 + u * C)) *\<^sub>R z + (u * C / (1 + u * C)) *\<^sub>R z = z"
+
−        by (simp add: scaleR_add_left [symmetric] divide_simps)
+
−      then have False
+
−        using convexD_alt [OF s \<open>a \<in> s\<close> ins, of "1/(u*C + 1)"] \<open>C>0\<close> \<open>z \<notin> s\<close> Cpos u
+
−        by (simp add: * divide_simps algebra_simps)
+
−    } note contra = this
+
−    have "connected_component (- s) z (z + C *\<^sub>R (z-a))"
+
−      apply (rule connected_componentI [OF connected_segment [of z "z + C *\<^sub>R (z-a)"]])
+
−      apply (simp add: closed_segment_def)
+
−      using contra
+
−      apply auto
+
−      done
+
−    then have False
+
−      using zna B [of "z + C *\<^sub>R (z-a)"] C
+
−      by (auto simp: divide_simps max_mult_distrib_right)
+
−  }
+
−  then show ?thesis
+
−    by (auto simp: outside_def z)
+
−qed
+
−
+
−lemma outside_convex:
+
−  fixes s :: "'a :: {real_normed_vector, perfect_space} set"
+
−  assumes "convex s"
+
−    shows "outside s = - s"
+
−  by (metis ComplD assms convex_in_outside equalityI inside_Un_outside subsetI sup.cobounded2)
+
−
+
−lemma outside_singleton [simp]:
+
−  fixes x :: "'a :: {real_normed_vector, perfect_space}"
+
−  shows "outside {x} = -{x}"
+
−  by (auto simp: outside_convex)
+
−
+
−lemma inside_convex:
+
−  fixes s :: "'a :: {real_normed_vector, perfect_space} set"
+
−  shows "convex s \<Longrightarrow> inside s = {}"
+
−  by (simp add: inside_outside outside_convex)
+
−
+
−lemma inside_singleton [simp]:
+
−  fixes x :: "'a :: {real_normed_vector, perfect_space}"
+
−  shows "inside {x} = {}"
+
−  by (auto simp: inside_convex)
+
−
+
−lemma outside_subset_convex:
+
−  fixes s :: "'a :: {real_normed_vector, perfect_space} set"
+
−  shows "\<lbrakk>convex t; s \<subseteq> t\<rbrakk> \<Longrightarrow> - t \<subseteq> outside s"
+
−  using outside_convex outside_mono by blast
+
−
+
−lemma outside_Un_outside_Un:
+
−  fixes S :: "'a::real_normed_vector set"
+
−  assumes "S \<inter> outside(T \<union> U) = {}"
+
−  shows "outside(T \<union> U) \<subseteq> outside(T \<union> S)"
+
−proof
+
−  fix x
+
−  assume x: "x \<in> outside (T \<union> U)"
+
−  have "Y \<subseteq> - S" if "connected Y" "Y \<subseteq> - T" "Y \<subseteq> - U" "x \<in> Y" "u \<in> Y" for u Y
+
−  proof -
+
−    have "Y \<subseteq> connected_component_set (- (T \<union> U)) x"
+
−      by (simp add: connected_component_maximal that)
+
−    also have "\<dots> \<subseteq> outside(T \<union> U)"
+
−      by (metis (mono_tags, lifting) Collect_mono mem_Collect_eq outside outside_same_component x)
+
−    finally have "Y \<subseteq> outside(T \<union> U)" .
+
−    with assms show ?thesis by auto
+
−  qed
+
−  with x show "x \<in> outside (T \<union> S)"
+
−    by (simp add: outside_connected_component_lt connected_component_def) meson
+
−qed
+
−
+
−lemma outside_frontier_misses_closure:
+
−    fixes s :: "'a::real_normed_vector set"
+
−    assumes "bounded s"
+
−    shows  "outside(frontier s) \<subseteq> - closure s"
+
−  unfolding outside_inside Lattices.boolean_algebra_class.compl_le_compl_iff
+
−proof -
+
−  { assume "interior s \<subseteq> inside (frontier s)"
+
−    hence "interior s \<union> inside (frontier s) = inside (frontier s)"
+
−      by (simp add: subset_Un_eq)
+
−    then have "closure s \<subseteq> frontier s \<union> inside (frontier s)"
+
−      using frontier_def by auto
+
−  }
+
−  then show "closure s \<subseteq> frontier s \<union> inside (frontier s)"
+
−    using interior_inside_frontier [OF assms] by blast
+
−qed
+
−
+
−lemma outside_frontier_eq_complement_closure:
+
−  fixes s :: "'a :: {real_normed_vector, perfect_space} set"
+
−    assumes "bounded s" "convex s"
+
−      shows "outside(frontier s) = - closure s"
+
−by (metis Diff_subset assms convex_closure frontier_def outside_frontier_misses_closure
+
−          outside_subset_convex subset_antisym)
+
−
+
−lemma inside_frontier_eq_interior:
+
−     fixes s :: "'a :: {real_normed_vector, perfect_space} set"
+
−     shows "\<lbrakk>bounded s; convex s\<rbrakk> \<Longrightarrow> inside(frontier s) = interior s"
+
−  apply (simp add: inside_outside outside_frontier_eq_complement_closure)
+
−  using closure_subset interior_subset
+
−  apply (auto simp: frontier_def)
+
−  done
+
−
+
−lemma open_inside:
+
−    fixes s :: "'a::real_normed_vector set"
+
−    assumes "closed s"
+
−      shows "open (inside s)"
+
−proof -
+
−  { fix x assume x: "x \<in> inside s"
+
−    have "open (connected_component_set (- s) x)"
+
−      using assms open_connected_component by blast
+
−    then obtain e where e: "e>0" and e: "\<And>y. dist y x < e \<longrightarrow> connected_component (- s) x y"
+
−      using dist_not_less_zero
+
−      apply (simp add: open_dist)
+
−      by (metis (no_types, lifting) Compl_iff connected_component_refl_eq inside_def mem_Collect_eq x)
+
−    then have "\<exists>e>0. ball x e \<subseteq> inside s"
+
−      by (metis e dist_commute inside_same_component mem_ball subsetI x)
+
−  }
+
−  then show ?thesis
+
−    by (simp add: open_contains_ball)
+
−qed
+
−
+
−lemma open_outside:
+
−    fixes s :: "'a::real_normed_vector set"
+
−    assumes "closed s"
+
−      shows "open (outside s)"
+
−proof -
+
−  { fix x assume x: "x \<in> outside s"
+
−    have "open (connected_component_set (- s) x)"
+
−      using assms open_connected_component by blast
+
−    then obtain e where e: "e>0" and e: "\<And>y. dist y x < e \<longrightarrow> connected_component (- s) x y"
+
−      using dist_not_less_zero
+
−      apply (simp add: open_dist)
+
−      by (metis Int_iff outside_def connected_component_refl_eq  x)
+
−    then have "\<exists>e>0. ball x e \<subseteq> outside s"
+
−      by (metis e dist_commute outside_same_component mem_ball subsetI x)
+
−  }
+
−  then show ?thesis
+
−    by (simp add: open_contains_ball)
+
−qed
+
−
+
−lemma closure_inside_subset:
+
−    fixes s :: "'a::real_normed_vector set"
+
−    assumes "closed s"
+
−      shows "closure(inside s) \<subseteq> s \<union> inside s"
+
−by (metis assms closure_minimal open_closed open_outside sup.cobounded2 union_with_inside)
+
−
+
−lemma frontier_inside_subset:
+
−    fixes s :: "'a::real_normed_vector set"
+
−    assumes "closed s"
+
−      shows "frontier(inside s) \<subseteq> s"
+
−proof -
+
−  have "closure (inside s) \<inter> - inside s = closure (inside s) - interior (inside s)"
+
−    by (metis (no_types) Diff_Compl assms closure_closed interior_closure open_closed open_inside)
+
−  moreover have "- inside s \<inter> - outside s = s"
+
−    by (metis (no_types) compl_sup double_compl inside_Un_outside)
+
−  moreover have "closure (inside s) \<subseteq> - outside s"
+
−    by (metis (no_types) assms closure_inside_subset union_with_inside)
+
−  ultimately have "closure (inside s) - interior (inside s) \<subseteq> s"
+
−    by blast
+
−  then show ?thesis
+
−    by (simp add: frontier_def open_inside interior_open)
+
−qed
+
−
+
−lemma closure_outside_subset:
+
−    fixes s :: "'a::real_normed_vector set"
+
−    assumes "closed s"
+
−      shows "closure(outside s) \<subseteq> s \<union> outside s"
+
−  apply (rule closure_minimal, simp)
+
−  by (metis assms closed_open inside_outside open_inside)
+
−
+
−lemma frontier_outside_subset:
+
−    fixes s :: "'a::real_normed_vector set"
+
−    assumes "closed s"
+
−      shows "frontier(outside s) \<subseteq> s"
+
−  apply (simp add: frontier_def open_outside interior_open)
+
−  by (metis Diff_subset_conv assms closure_outside_subset interior_eq open_outside sup.commute)
+
−
+
−lemma inside_complement_unbounded_connected_empty:
+
−     "\<lbrakk>connected (- s); \<not> bounded (- s)\<rbrakk> \<Longrightarrow> inside s = {}"
+
−  apply (simp add: inside_def)
+
−  by (meson Compl_iff bounded_subset connected_component_maximal order_refl)
+
−
+
−lemma inside_bounded_complement_connected_empty:
+
−    fixes s :: "'a::{real_normed_vector, perfect_space} set"
+
−    shows "\<lbrakk>connected (- s); bounded s\<rbrakk> \<Longrightarrow> inside s = {}"
+
−  by (metis inside_complement_unbounded_connected_empty cobounded_imp_unbounded)
+
−
+
−lemma inside_inside:
+
−    assumes "s \<subseteq> inside t"
+
−    shows "inside s - t \<subseteq> inside t"
+
−unfolding inside_def
+
−proof clarify
+
−  fix x
+
−  assume x: "x \<notin> t" "x \<notin> s" and bo: "bounded (connected_component_set (- s) x)"
+
−  show "bounded (connected_component_set (- t) x)"
+
−  proof (cases "s \<inter> connected_component_set (- t) x = {}")
+
−    case True show ?thesis
+
−      apply (rule bounded_subset [OF bo])
+
−      apply (rule connected_component_maximal)
+
−      using x True apply auto
+
−      done
+
−  next
+
−    case False then show ?thesis
+
−      using assms [unfolded inside_def] x
+
−      apply (simp add: disjoint_iff_not_equal, clarify)
+
−      apply (drule subsetD, assumption, auto)
+
−      by (metis (no_types, hide_lams) ComplI connected_component_eq_eq)
+
−  qed
+
−qed
+
−
+
−lemma inside_inside_subset: "inside(inside s) \<subseteq> s"
+
−  using inside_inside union_with_outside by fastforce
+
−
+
−lemma inside_outside_intersect_connected:
+
−      "\<lbrakk>connected t; inside s \<inter> t \<noteq> {}; outside s \<inter> t \<noteq> {}\<rbrakk> \<Longrightarrow> s \<inter> t \<noteq> {}"
+
−  apply (simp add: inside_def outside_def ex_in_conv [symmetric] disjoint_eq_subset_Compl, clarify)
+
−  by (metis (no_types, hide_lams) Compl_anti_mono connected_component_eq connected_component_maximal contra_subsetD double_compl)
+
−
+
−lemma outside_bounded_nonempty:
+
−  fixes s :: "'a :: {real_normed_vector, perfect_space} set"
+
−    assumes "bounded s" shows "outside s \<noteq> {}"
+
−  by (metis (no_types, lifting) Collect_empty_eq Collect_mem_eq Compl_eq_Diff_UNIV Diff_cancel
+
−                   Diff_disjoint UNIV_I assms ball_eq_empty bounded_diff cobounded_outside convex_ball
+
−                   double_complement order_refl outside_convex outside_def)
+
−
+
−lemma outside_compact_in_open:
+
−    fixes s :: "'a :: {real_normed_vector,perfect_space} set"
+
−    assumes s: "compact s" and t: "open t" and "s \<subseteq> t" "t \<noteq> {}"
+
−      shows "outside s \<inter> t \<noteq> {}"
+
−proof -
+
−  have "outside s \<noteq> {}"
+
−    by (simp add: compact_imp_bounded outside_bounded_nonempty s)
+
−  with assms obtain a b where a: "a \<in> outside s" and b: "b \<in> t" by auto
+
−  show ?thesis
+
−  proof (cases "a \<in> t")
+
−    case True with a show ?thesis by blast
+
−  next
+
−    case False
+
−      have front: "frontier t \<subseteq> - s"
+
−        using \<open>s \<subseteq> t\<close> frontier_disjoint_eq t by auto
+
−      { fix \<gamma>
+
−        assume "path \<gamma>" and pimg_sbs: "path_image \<gamma> - {pathfinish \<gamma>} \<subseteq> interior (- t)"
+
−           and pf: "pathfinish \<gamma> \<in> frontier t" and ps: "pathstart \<gamma> = a"
+
−        define c where "c = pathfinish \<gamma>"
+
−        have "c \<in> -s" unfolding c_def using front pf by blast
+
−        moreover have "open (-s)" using s compact_imp_closed by blast
+
−        ultimately obtain \<epsilon>::real where "\<epsilon> > 0" and \<epsilon>: "cball c \<epsilon> \<subseteq> -s"
+
−          using open_contains_cball[of "-s"] s by blast
+
−        then obtain d where "d \<in> t" and d: "dist d c < \<epsilon>"
+
−          using closure_approachable [of c t] pf unfolding c_def
+
−          by (metis Diff_iff frontier_def)
+
−        then have "d \<in> -s" using \<epsilon>
+
−          using dist_commute by (metis contra_subsetD mem_cball not_le not_less_iff_gr_or_eq)
+
−        have pimg_sbs_cos: "path_image \<gamma> \<subseteq> -s"
+
−          using pimg_sbs apply (auto simp: path_image_def)
+
−          apply (drule subsetD)
+
−          using \<open>c \<in> - s\<close> \<open>s \<subseteq> t\<close> interior_subset apply (auto simp: c_def)
+
−          done
+
−        have "closed_segment c d \<le> cball c \<epsilon>"
+
−          apply (simp add: segment_convex_hull)
+
−          apply (rule hull_minimal)
+
−          using  \<open>\<epsilon> > 0\<close> d apply (auto simp: dist_commute)
+
−          done
+
−        with \<epsilon> have "closed_segment c d \<subseteq> -s" by blast
+
−        moreover have con_gcd: "connected (path_image \<gamma> \<union> closed_segment c d)"
+
−          by (rule connected_Un) (auto simp: c_def \<open>path \<gamma>\<close> connected_path_image)
+
−        ultimately have "connected_component (- s) a d"
+
−          unfolding connected_component_def using pimg_sbs_cos ps by blast
+
−        then have "outside s \<inter> t \<noteq> {}"
+
−          using outside_same_component [OF _ a]  by (metis IntI \<open>d \<in> t\<close> empty_iff)
+
−      } note * = this
+
−      have pal: "pathstart (linepath a b) \<in> closure (- t)"
+
−        by (auto simp: False closure_def)
+
−      show ?thesis
+
−        by (rule exists_path_subpath_to_frontier [OF path_linepath pal _ *]) (auto simp: b)
+
−  qed
+
−qed
+
−
+
−lemma inside_inside_compact_connected:
+
−    fixes s :: "'a :: euclidean_space set"
+
−    assumes s: "closed s" and t: "compact t" and "connected t" "s \<subseteq> inside t"
+
−      shows "inside s \<subseteq> inside t"
+
−proof (cases "inside t = {}")
+
−  case True with assms show ?thesis by auto
+
−next
+
−  case False
+
−  consider "DIM('a) = 1" | "DIM('a) \<ge> 2"
+
−    using antisym not_less_eq_eq by fastforce
+
−  then show ?thesis
+
−  proof cases
+
−    case 1 then show ?thesis
+
−             using connected_convex_1_gen assms False inside_convex by blast
+
−  next
+
−    case 2
+
−    have coms: "compact s"
+
−      using assms apply (simp add: s compact_eq_bounded_closed)
+
−       by (meson bounded_inside bounded_subset compact_imp_bounded)
+
−    then have bst: "bounded (s \<union> t)"
+
−      by (simp add: compact_imp_bounded t)
+
−    then obtain r where "0 < r" and r: "s \<union> t \<subseteq> ball 0 r"
+
−      using bounded_subset_ballD by blast
+
−    have outst: "outside s \<inter> outside t \<noteq> {}"
+
−    proof -
+
−      have "- ball 0 r \<subseteq> outside s"
+
−        apply (rule outside_subset_convex)
+
−        using r by auto
+
−      moreover have "- ball 0 r \<subseteq> outside t"
+
−        apply (rule outside_subset_convex)
+
−        using r by auto
+
−      ultimately show ?thesis
+
−        by (metis Compl_subset_Compl_iff Int_subset_iff bounded_ball inf.orderE outside_bounded_nonempty outside_no_overlap)
+
−    qed
+
−    have "s \<inter> t = {}" using assms
+
−      by (metis disjoint_iff_not_equal inside_no_overlap subsetCE)
+
−    moreover have "outside s \<inter> inside t \<noteq> {}"
+
−      by (meson False assms(4) compact_eq_bounded_closed coms open_inside outside_compact_in_open t)
+
−    ultimately have "inside s \<inter> t = {}"
+
−      using inside_outside_intersect_connected [OF \<open>connected t\<close>, of s]
+
−      by (metis "2" compact_eq_bounded_closed coms connected_outside inf.commute inside_outside_intersect_connected outst)
+
−    then show ?thesis
+
−      using inside_inside [OF \<open>s \<subseteq> inside t\<close>] by blast
+
−  qed
+
−qed
+
−
+
−lemma connected_with_inside:
+
−    fixes s :: "'a :: real_normed_vector set"
+
−    assumes s: "closed s" and cons: "connected s"
+
−      shows "connected(s \<union> inside s)"
+
−proof (cases "s \<union> inside s = UNIV")
+
−  case True with assms show ?thesis by auto
+
−next
+
−  case False
+
−  then obtain b where b: "b \<notin> s" "b \<notin> inside s" by blast
+
−  have *: "\<exists>y t. y \<in> s \<and> connected t \<and> a \<in> t \<and> y \<in> t \<and> t \<subseteq> (s \<union> inside s)" if "a \<in> (s \<union> inside s)" for a
+
−  using that proof
+
−    assume "a \<in> s" then show ?thesis
+
−      apply (rule_tac x=a in exI)
+
−      apply (rule_tac x="{a}" in exI, simp)
+
−      done
+
−  next
+
−    assume a: "a \<in> inside s"
+
−    show ?thesis
+
−      apply (rule exists_path_subpath_to_frontier [OF path_linepath [of a b], of "inside s"])
+
−      using a apply (simp add: closure_def)
+
−      apply (simp add: b)
+
−      apply (rule_tac x="pathfinish h" in exI)
+
−      apply (rule_tac x="path_image h" in exI)
+
−      apply (simp add: pathfinish_in_path_image connected_path_image, auto)
+
−      using frontier_inside_subset s apply fastforce
+
−      by (metis (no_types, lifting) frontier_inside_subset insertE insert_Diff interior_eq open_inside pathfinish_in_path_image s subsetCE)
+
−  qed
+
−  show ?thesis
+
−    apply (simp add: connected_iff_connected_component)
+
−    apply (simp add: connected_component_def)
+
−    apply (clarify dest!: *)
+
−    apply (rename_tac u u' t t')
+
−    apply (rule_tac x="(s \<union> t \<union> t')" in exI)
+
−    apply (auto simp: intro!: connected_Un cons)
+
−    done
+
−qed
+
−
+
−text\<open>The proof is virtually the same as that above.\<close>
+
−lemma connected_with_outside:
+
−    fixes s :: "'a :: real_normed_vector set"
+
−    assumes s: "closed s" and cons: "connected s"
+
−      shows "connected(s \<union> outside s)"
+
−proof (cases "s \<union> outside s = UNIV")
+
−  case True with assms show ?thesis by auto
+
−next
+
−  case False
+
−  then obtain b where b: "b \<notin> s" "b \<notin> outside s" by blast
+
−  have *: "\<exists>y t. y \<in> s \<and> connected t \<and> a \<in> t \<and> y \<in> t \<and> t \<subseteq> (s \<union> outside s)" if "a \<in> (s \<union> outside s)" for a
+
−  using that proof
+
−    assume "a \<in> s" then show ?thesis
+
−      apply (rule_tac x=a in exI)
+
−      apply (rule_tac x="{a}" in exI, simp)
+
−      done
+
−  next
+
−    assume a: "a \<in> outside s"
+
−    show ?thesis
+
−      apply (rule exists_path_subpath_to_frontier [OF path_linepath [of a b], of "outside s"])
+
−      using a apply (simp add: closure_def)
+
−      apply (simp add: b)
+
−      apply (rule_tac x="pathfinish h" in exI)
+
−      apply (rule_tac x="path_image h" in exI)
+
−      apply (simp add: pathfinish_in_path_image connected_path_image, auto)
+
−      using frontier_outside_subset s apply fastforce
+
−      by (metis (no_types, lifting) frontier_outside_subset insertE insert_Diff interior_eq open_outside pathfinish_in_path_image s subsetCE)
+
−  qed
+
−  show ?thesis
+
−    apply (simp add: connected_iff_connected_component)
+
−    apply (simp add: connected_component_def)
+
−    apply (clarify dest!: *)
+
−    apply (rename_tac u u' t t')
+
−    apply (rule_tac x="(s \<union> t \<union> t')" in exI)
+
−    apply (auto simp: intro!: connected_Un cons)
+
−    done
+
−qed
+
−
+
−lemma inside_inside_eq_empty [simp]:
+
−    fixes s :: "'a :: {real_normed_vector, perfect_space} set"
+
−    assumes s: "closed s" and cons: "connected s"
+
−      shows "inside (inside s) = {}"
+
−  by (metis (no_types) unbounded_outside connected_with_outside [OF assms] bounded_Un
+
−           inside_complement_unbounded_connected_empty unbounded_outside union_with_outside)
+
−
+
−lemma inside_in_components:
+
−     "inside s \<in> components (- s) \<longleftrightarrow> connected(inside s) \<and> inside s \<noteq> {}"
+
−  apply (simp add: in_components_maximal)
+
−  apply (auto intro: inside_same_component connected_componentI)
+
−  apply (metis IntI empty_iff inside_no_overlap)
+
−  done
+
−
+
−text\<open>The proof is virtually the same as that above.\<close>
+
−lemma outside_in_components:
+
−     "outside s \<in> components (- s) \<longleftrightarrow> connected(outside s) \<and> outside s \<noteq> {}"
+
−  apply (simp add: in_components_maximal)
+
−  apply (auto intro: outside_same_component connected_componentI)
+
−  apply (metis IntI empty_iff outside_no_overlap)
+
−  done
+
−
+
−lemma bounded_unique_outside:
+
−    fixes s :: "'a :: euclidean_space set"
+
−    shows "\<lbrakk>bounded s; DIM('a) \<ge> 2\<rbrakk> \<Longrightarrow> (c \<in> components (- s) \<and> \<not> bounded c \<longleftrightarrow> c = outside s)"
+
−  apply (rule iffI)
+
−  apply (metis cobounded_unique_unbounded_components connected_outside double_compl outside_bounded_nonempty outside_in_components unbounded_outside)
+
−  by (simp add: connected_outside outside_bounded_nonempty outside_in_components unbounded_outside)
+
−
+
−
+
−subsection\<open>Condition for an open map's image to contain a ball\<close>
+
−
+
−proposition ball_subset_open_map_image:
+
−  fixes f :: "'a::heine_borel \<Rightarrow> 'b :: {real_normed_vector,heine_borel}"
+
−  assumes contf: "continuous_on (closure S) f"
+
−      and oint: "open (f ` interior S)"
+
−      and le_no: "\<And>z. z \<in> frontier S \<Longrightarrow> r \<le> norm(f z - f a)"
+
−      and "bounded S" "a \<in> S" "0 < r"
+
−    shows "ball (f a) r \<subseteq> f ` S"
+
−proof (cases "f ` S = UNIV")
+
−  case True then show ?thesis by simp
+
−next
+
−  case False
+
−    obtain w where w: "w \<in> frontier (f ` S)"
+
−               and dw_le: "\<And>y. y \<in> frontier (f ` S) \<Longrightarrow> norm (f a - w) \<le> norm (f a - y)"
+
−      apply (rule distance_attains_inf [of "frontier(f ` S)" "f a"])
+
−      using \<open>a \<in> S\<close> by (auto simp: frontier_eq_empty dist_norm False)
+
−    then obtain \<xi> where \<xi>: "\<And>n. \<xi> n \<in> f ` S" and tendsw: "\<xi> \<longlonglongrightarrow> w"
+
−      by (metis Diff_iff frontier_def closure_sequential)
+
−    then have "\<And>n. \<exists>x \<in> S. \<xi> n = f x" by force
+
−    then obtain z where zs: "\<And>n. z n \<in> S" and fz: "\<And>n. \<xi> n = f (z n)"
+
−      by metis
+
−    then obtain y K where y: "y \<in> closure S" and "strict_mono (K :: nat \<Rightarrow> nat)" 
+
−                      and Klim: "(z \<circ> K) \<longlonglongrightarrow> y"
+
−      using \<open>bounded S\<close>
+
−      apply (simp add: compact_closure [symmetric] compact_def)
+
−      apply (drule_tac x=z in spec)
+
−      using closure_subset apply force
+
−      done
+
−    then have ftendsw: "((\<lambda>n. f (z n)) \<circ> K) \<longlonglongrightarrow> w"
+
−      by (metis LIMSEQ_subseq_LIMSEQ fun.map_cong0 fz tendsw)
+
−    have zKs: "\<And>n. (z \<circ> K) n \<in> S" by (simp add: zs)
+
−    have fz: "f \<circ> z = \<xi>"  "(\<lambda>n. f (z n)) = \<xi>"
+
−      using fz by auto
+
−    then have "(\<xi> \<circ> K) \<longlonglongrightarrow> f y"
+
−      by (metis (no_types) Klim zKs y contf comp_assoc continuous_on_closure_sequentially)
+
−    with fz have wy: "w = f y" using fz LIMSEQ_unique ftendsw by auto
+
−    have rle: "r \<le> norm (f y - f a)"
+
−      apply (rule le_no)
+
−      using w wy oint
+
−      by (force simp: imageI image_mono interiorI interior_subset frontier_def y)
+
−    have **: "(b \<inter> (- S) \<noteq> {} \<and> b - (- S) \<noteq> {} \<Longrightarrow> b \<inter> f \<noteq> {})
+
−              \<Longrightarrow> (b \<inter> S \<noteq> {}) \<Longrightarrow> b \<inter> f = {} \<Longrightarrow>
+
−              b \<subseteq> S" for b f and S :: "'b set"
+
−      by blast
+
−    show ?thesis
+
−      apply (rule **)   (*such a horrible mess*)
+
−      apply (rule connected_Int_frontier [where t = "f`S", OF connected_ball])
+
−      using \<open>a \<in> S\<close> \<open>0 < r\<close>
+
−      apply (auto simp: disjoint_iff_not_equal  dist_norm)
+
−      by (metis dw_le norm_minus_commute not_less order_trans rle wy)
+
−qed
+
−
+
−end