diff --git a/src/HOL/Analysis/Retracts.thy b/src/HOL/Analysis/Retracts.thy
--- a/src/HOL/Analysis/Retracts.thy
+++ b/src/HOL/Analysis/Retracts.thy
@@ -1,2595 +1,2518 @@
 section \<open>Absolute Retracts, Absolute Neighbourhood Retracts and Euclidean Neighbourhood Retracts\<close>
 
 theory Retracts
 imports
   Brouwer_Fixpoint
   Continuous_Extension
 begin
 
 text \<open>Absolute retracts (AR), absolute neighbourhood retracts (ANR) and also Euclidean neighbourhood
 retracts (ENR). We define AR and ANR by specializing the standard definitions for a set to embedding
 in spaces of higher dimension.
 
 John Harrison writes: "This turns out to be sufficient (since any set in \<open>\<real>\<^sup>n\<close> can be
 embedded as a closed subset of a convex subset of \<open>\<real>\<^sup>n\<^sup>+\<^sup>1\<close>) to derive the usual
 definitions, but we need to split them into two implications because of the lack of type
 quantifiers. Then ENR turns out to be equivalent to ANR plus local compactness."\<close>
 
 definition\<^marker>\<open>tag important\<close> AR :: "'a::topological_space set \<Rightarrow> bool" where
 "AR S \<equiv> \<forall>U. \<forall>S'::('a * real) set.
   S homeomorphic S' \<and> closedin (top_of_set U) S' \<longrightarrow> S' retract_of U"
 
 definition\<^marker>\<open>tag important\<close> ANR :: "'a::topological_space set \<Rightarrow> bool" where
 "ANR S \<equiv> \<forall>U. \<forall>S'::('a * real) set.
   S homeomorphic S' \<and> closedin (top_of_set U) S'
   \<longrightarrow> (\<exists>T. openin (top_of_set U) T \<and> S' retract_of T)"
 
 definition\<^marker>\<open>tag important\<close> ENR :: "'a::topological_space set \<Rightarrow> bool" where
 "ENR S \<equiv> \<exists>U. open U \<and> S retract_of U"
 
 text \<open>First, show that we do indeed get the "usual" properties of ARs and ANRs.\<close>
 
 lemma AR_imp_absolute_extensor:
   fixes f :: "'a::euclidean_space \<Rightarrow> 'b::euclidean_space"
   assumes "AR S" and contf: "continuous_on T f" and "f ` T \<subseteq> S"
       and cloUT: "closedin (top_of_set U) T"
   obtains g where "continuous_on U g" "g ` U \<subseteq> S" "\<And>x. x \<in> T \<Longrightarrow> g x = f x"
 proof -
   have "aff_dim S < int (DIM('b \<times> real))"
     using aff_dim_le_DIM [of S] by simp
   then obtain C and S' :: "('b * real) set"
           where C: "convex C" "C \<noteq> {}"
             and cloCS: "closedin (top_of_set C) S'"
             and hom: "S homeomorphic S'"
     by (metis that homeomorphic_closedin_convex)
   then have "S' retract_of C"
     using \<open>AR S\<close> by (simp add: AR_def)
   then obtain r where "S' \<subseteq> C" and contr: "continuous_on C r"
                   and "r ` C \<subseteq> S'" and rid: "\<And>x. x\<in>S' \<Longrightarrow> r x = x"
     by (auto simp: retraction_def retract_of_def)
   obtain g h where "homeomorphism S S' g h"
     using hom by (force simp: homeomorphic_def)
   then have "continuous_on (f ` T) g"
     by (meson \<open>f ` T \<subseteq> S\<close> continuous_on_subset homeomorphism_def)
   then have contgf: "continuous_on T (g \<circ> f)"
     by (metis continuous_on_compose contf)
   have gfTC: "(g \<circ> f) ` T \<subseteq> C"
   proof -
     have "g ` S = S'"
       by (metis (no_types) \<open>homeomorphism S S' g h\<close> homeomorphism_def)
     with \<open>S' \<subseteq> C\<close> \<open>f ` T \<subseteq> S\<close> show ?thesis by force
   qed
   obtain f' where f': "continuous_on U f'"  "f' ` U \<subseteq> C"
                       "\<And>x. x \<in> T \<Longrightarrow> f' x = (g \<circ> f) x"
     by (metis Dugundji [OF C cloUT contgf gfTC])
   show ?thesis
   proof (rule_tac g = "h \<circ> r \<circ> f'" in that)
     show "continuous_on U (h \<circ> r \<circ> f')"
-      apply (intro continuous_on_compose f')
-       using continuous_on_subset contr f' apply blast
-      by (meson \<open>homeomorphism S S' g h\<close> \<open>r ` C \<subseteq> S'\<close> continuous_on_subset \<open>f' ` U \<subseteq> C\<close> homeomorphism_def image_mono)
+    proof (intro continuous_on_compose f')
+      show "continuous_on (f' ` U) r"
+        using continuous_on_subset contr f' by blast
+      show "continuous_on (r ` f' ` U) h"
+        using \<open>homeomorphism S S' g h\<close> \<open>f' ` U \<subseteq> C\<close> 
+        unfolding homeomorphism_def
+        by (metis \<open>r ` C \<subseteq> S'\<close> continuous_on_subset image_mono)
+    qed
     show "(h \<circ> r \<circ> f') ` U \<subseteq> S"
       using \<open>homeomorphism S S' g h\<close> \<open>r ` C \<subseteq> S'\<close> \<open>f' ` U \<subseteq> C\<close>
       by (fastforce simp: homeomorphism_def)
     show "\<And>x. x \<in> T \<Longrightarrow> (h \<circ> r \<circ> f') x = f x"
       using \<open>homeomorphism S S' g h\<close> \<open>f ` T \<subseteq> S\<close> f'
       by (auto simp: rid homeomorphism_def)
   qed
 qed
 
 lemma AR_imp_absolute_retract:
   fixes S :: "'a::euclidean_space set" and S' :: "'b::euclidean_space set"
   assumes "AR S" "S homeomorphic S'"
       and clo: "closedin (top_of_set U) S'"
     shows "S' retract_of U"
 proof -
   obtain g h where hom: "homeomorphism S S' g h"
     using assms by (force simp: homeomorphic_def)
-  have h: "continuous_on S' h" " h ` S' \<subseteq> S"
-    using hom homeomorphism_def apply blast
-    apply (metis hom equalityE homeomorphism_def)
-    done
+  obtain h: "continuous_on S' h" " h ` S' \<subseteq> S"
+    using hom homeomorphism_def by blast
   obtain h' where h': "continuous_on U h'" "h' ` U \<subseteq> S"
               and h'h: "\<And>x. x \<in> S' \<Longrightarrow> h' x = h x"
     by (blast intro: AR_imp_absolute_extensor [OF \<open>AR S\<close> h clo])
   have [simp]: "S' \<subseteq> U" using clo closedin_limpt by blast
   show ?thesis
   proof (simp add: retraction_def retract_of_def, intro exI conjI)
     show "continuous_on U (g \<circ> h')"
-      apply (intro continuous_on_compose h')
-      apply (meson hom continuous_on_subset h' homeomorphism_cont1)
-      done
+      by (meson continuous_on_compose continuous_on_subset h' hom homeomorphism_cont1)
     show "(g \<circ> h') ` U \<subseteq> S'"
       using h'  by clarsimp (metis hom subsetD homeomorphism_def imageI)
     show "\<forall>x\<in>S'. (g \<circ> h') x = x"
       by clarsimp (metis h'h hom homeomorphism_def)
   qed
 qed
 
 lemma AR_imp_absolute_retract_UNIV:
   fixes S :: "'a::euclidean_space set" and S' :: "'b::euclidean_space set"
-  assumes "AR S" and hom: "S homeomorphic S'"
-      and clo: "closed S'"
+  assumes "AR S" "S homeomorphic S'" "closed S'"
     shows "S' retract_of UNIV"
-apply (rule AR_imp_absolute_retract [OF \<open>AR S\<close> hom])
-using clo closed_closedin by auto
+  using AR_imp_absolute_retract assms by fastforce
 
 lemma absolute_extensor_imp_AR:
   fixes S :: "'a::euclidean_space set"
   assumes "\<And>f :: 'a * real \<Rightarrow> 'a.
            \<And>U T. \<lbrakk>continuous_on T f;  f ` T \<subseteq> S;
                   closedin (top_of_set U) T\<rbrakk>
                  \<Longrightarrow> \<exists>g. continuous_on U g \<and> g ` U \<subseteq> S \<and> (\<forall>x \<in> T. g x = f x)"
   shows "AR S"
 proof (clarsimp simp: AR_def)
   fix U and T :: "('a * real) set"
   assume "S homeomorphic T" and clo: "closedin (top_of_set U) T"
   then obtain g h where hom: "homeomorphism S T g h"
     by (force simp: homeomorphic_def)
-  have h: "continuous_on T h" " h ` T \<subseteq> S"
-    using hom homeomorphism_def apply blast
-    apply (metis hom equalityE homeomorphism_def)
-    done
+  obtain h: "continuous_on T h" " h ` T \<subseteq> S"
+    using hom homeomorphism_def by blast
   obtain h' where h': "continuous_on U h'" "h' ` U \<subseteq> S"
               and h'h: "\<forall>x\<in>T. h' x = h x"
     using assms [OF h clo] by blast
   have [simp]: "T \<subseteq> U"
     using clo closedin_imp_subset by auto
   show "T retract_of U"
   proof (simp add: retraction_def retract_of_def, intro exI conjI)
     show "continuous_on U (g \<circ> h')"
-      apply (intro continuous_on_compose h')
-      apply (meson hom continuous_on_subset h' homeomorphism_cont1)
-      done
+      by (meson continuous_on_compose continuous_on_subset h' hom homeomorphism_cont1)
     show "(g \<circ> h') ` U \<subseteq> T"
       using h'  by clarsimp (metis hom subsetD homeomorphism_def imageI)
     show "\<forall>x\<in>T. (g \<circ> h') x = x"
       by clarsimp (metis h'h hom homeomorphism_def)
   qed
 qed
 
 lemma AR_eq_absolute_extensor:
   fixes S :: "'a::euclidean_space set"
   shows "AR S \<longleftrightarrow>
        (\<forall>f :: 'a * real \<Rightarrow> 'a.
         \<forall>U T. continuous_on T f \<longrightarrow> f ` T \<subseteq> S \<longrightarrow>
                closedin (top_of_set U) T \<longrightarrow>
                 (\<exists>g. continuous_on U g \<and> g ` U \<subseteq> S \<and> (\<forall>x \<in> T. g x = f x)))"
-apply (rule iffI)
- apply (metis AR_imp_absolute_extensor)
-apply (simp add: absolute_extensor_imp_AR)
-done
+  by (metis (mono_tags, hide_lams) AR_imp_absolute_extensor absolute_extensor_imp_AR)
 
 lemma AR_imp_retract:
   fixes S :: "'a::euclidean_space set"
   assumes "AR S \<and> closedin (top_of_set U) S"
     shows "S retract_of U"
 using AR_imp_absolute_retract assms homeomorphic_refl by blast
 
 lemma AR_homeomorphic_AR:
   fixes S :: "'a::euclidean_space set" and T :: "'b::euclidean_space set"
   assumes "AR T" "S homeomorphic T"
     shows "AR S"
 unfolding AR_def
 by (metis assms AR_imp_absolute_retract homeomorphic_trans [of _ S] homeomorphic_sym)
 
 lemma homeomorphic_AR_iff_AR:
   fixes S :: "'a::euclidean_space set" and T :: "'b::euclidean_space set"
   shows "S homeomorphic T \<Longrightarrow> AR S \<longleftrightarrow> AR T"
 by (metis AR_homeomorphic_AR homeomorphic_sym)
 
 
 lemma ANR_imp_absolute_neighbourhood_extensor:
   fixes f :: "'a::euclidean_space \<Rightarrow> 'b::euclidean_space"
   assumes "ANR S" and contf: "continuous_on T f" and "f ` T \<subseteq> S"
       and cloUT: "closedin (top_of_set U) T"
   obtains V g where "T \<subseteq> V" "openin (top_of_set U) V"
                     "continuous_on V g"
                     "g ` V \<subseteq> S" "\<And>x. x \<in> T \<Longrightarrow> g x = f x"
 proof -
   have "aff_dim S < int (DIM('b \<times> real))"
     using aff_dim_le_DIM [of S] by simp
   then obtain C and S' :: "('b * real) set"
           where C: "convex C" "C \<noteq> {}"
             and cloCS: "closedin (top_of_set C) S'"
             and hom: "S homeomorphic S'"
     by (metis that homeomorphic_closedin_convex)
   then obtain D where opD: "openin (top_of_set C) D" and "S' retract_of D"
     using \<open>ANR S\<close> by (auto simp: ANR_def)
   then obtain r where "S' \<subseteq> D" and contr: "continuous_on D r"
                   and "r ` D \<subseteq> S'" and rid: "\<And>x. x \<in> S' \<Longrightarrow> r x = x"
     by (auto simp: retraction_def retract_of_def)
   obtain g h where homgh: "homeomorphism S S' g h"
     using hom by (force simp: homeomorphic_def)
   have "continuous_on (f ` T) g"
     by (meson \<open>f ` T \<subseteq> S\<close> continuous_on_subset homeomorphism_def homgh)
   then have contgf: "continuous_on T (g \<circ> f)"
     by (intro continuous_on_compose contf)
   have gfTC: "(g \<circ> f) ` T \<subseteq> C"
   proof -
     have "g ` S = S'"
       by (metis (no_types) homeomorphism_def homgh)
     then show ?thesis
       by (metis (no_types) assms(3) cloCS closedin_def image_comp image_mono order.trans topspace_euclidean_subtopology)
   qed
   obtain f' where contf': "continuous_on U f'"
               and "f' ` U \<subseteq> C"
               and eq: "\<And>x. x \<in> T \<Longrightarrow> f' x = (g \<circ> f) x"
     by (metis Dugundji [OF C cloUT contgf gfTC])
   show ?thesis
   proof (rule_tac V = "U \<inter> f' -` D" and g = "h \<circ> r \<circ> f'" in that)
     show "T \<subseteq> U \<inter> f' -` D"
       using cloUT closedin_imp_subset \<open>S' \<subseteq> D\<close> \<open>f ` T \<subseteq> S\<close> eq homeomorphism_image1 homgh
       by fastforce
     show ope: "openin (top_of_set U) (U \<inter> f' -` D)"
       using  \<open>f' ` U \<subseteq> C\<close> by (auto simp: opD contf' continuous_openin_preimage)
     have conth: "continuous_on (r ` f' ` (U \<inter> f' -` D)) h"
-      apply (rule continuous_on_subset [of S'])
-      using homeomorphism_def homgh apply blast
-      using \<open>r ` D \<subseteq> S'\<close> by blast
+    proof (rule continuous_on_subset [of S'])
+      show "continuous_on S' h"
+        using homeomorphism_def homgh by blast
+    qed (use \<open>r ` D \<subseteq> S'\<close> in blast)
     show "continuous_on (U \<inter> f' -` D) (h \<circ> r \<circ> f')"
-      apply (intro continuous_on_compose conth
-                   continuous_on_subset [OF contr] continuous_on_subset [OF contf'], auto)
-      done
+      by (blast intro: continuous_on_compose conth continuous_on_subset [OF contr] continuous_on_subset [OF contf'])
     show "(h \<circ> r \<circ> f') ` (U \<inter> f' -` D) \<subseteq> S"
       using \<open>homeomorphism S S' g h\<close>  \<open>f' ` U \<subseteq> C\<close>  \<open>r ` D \<subseteq> S'\<close>
       by (auto simp: homeomorphism_def)
     show "\<And>x. x \<in> T \<Longrightarrow> (h \<circ> r \<circ> f') x = f x"
       using \<open>homeomorphism S S' g h\<close> \<open>f ` T \<subseteq> S\<close> eq
       by (auto simp: rid homeomorphism_def)
   qed
 qed
 
 
 corollary ANR_imp_absolute_neighbourhood_retract:
   fixes S :: "'a::euclidean_space set" and S' :: "'b::euclidean_space set"
   assumes "ANR S" "S homeomorphic S'"
       and clo: "closedin (top_of_set U) S'"
   obtains V where "openin (top_of_set U) V" "S' retract_of V"
 proof -
   obtain g h where hom: "homeomorphism S S' g h"
     using assms by (force simp: homeomorphic_def)
-  have h: "continuous_on S' h" " h ` S' \<subseteq> S"
-    using hom homeomorphism_def apply blast
-    apply (metis hom equalityE homeomorphism_def)
-    done
+  obtain h: "continuous_on S' h" " h ` S' \<subseteq> S"
+    using hom homeomorphism_def by blast
     from ANR_imp_absolute_neighbourhood_extensor [OF \<open>ANR S\<close> h clo]
   obtain V h' where "S' \<subseteq> V" and opUV: "openin (top_of_set U) V"
                 and h': "continuous_on V h'" "h' ` V \<subseteq> S"
                 and h'h:"\<And>x. x \<in> S' \<Longrightarrow> h' x = h x"
     by (blast intro: ANR_imp_absolute_neighbourhood_extensor [OF \<open>ANR S\<close> h clo])
   have "S' retract_of V"
   proof (simp add: retraction_def retract_of_def, intro exI conjI \<open>S' \<subseteq> V\<close>)
     show "continuous_on V (g \<circ> h')"
-      apply (intro continuous_on_compose h')
-      apply (meson hom continuous_on_subset h' homeomorphism_cont1)
-      done
+      by (meson continuous_on_compose continuous_on_subset h'(1) h'(2) hom homeomorphism_cont1)
     show "(g \<circ> h') ` V \<subseteq> S'"
       using h'  by clarsimp (metis hom subsetD homeomorphism_def imageI)
     show "\<forall>x\<in>S'. (g \<circ> h') x = x"
       by clarsimp (metis h'h hom homeomorphism_def)
   qed
   then show ?thesis
     by (rule that [OF opUV])
 qed
 
 corollary ANR_imp_absolute_neighbourhood_retract_UNIV:
   fixes S :: "'a::euclidean_space set" and S' :: "'b::euclidean_space set"
   assumes "ANR S" and hom: "S homeomorphic S'" and clo: "closed S'"
   obtains V where "open V" "S' retract_of V"
   using ANR_imp_absolute_neighbourhood_retract [OF \<open>ANR S\<close> hom]
 by (metis clo closed_closedin open_openin subtopology_UNIV)
 
 corollary neighbourhood_extension_into_ANR:
   fixes f :: "'a::euclidean_space \<Rightarrow> 'b::euclidean_space"
   assumes contf: "continuous_on S f" and fim: "f ` S \<subseteq> T" and "ANR T" "closed S"
   obtains V g where "S \<subseteq> V" "open V" "continuous_on V g"
                     "g ` V \<subseteq> T" "\<And>x. x \<in> S \<Longrightarrow> g x = f x"
   using ANR_imp_absolute_neighbourhood_extensor [OF  \<open>ANR T\<close> contf fim]
   by (metis \<open>closed S\<close> closed_closedin open_openin subtopology_UNIV)
 
 lemma absolute_neighbourhood_extensor_imp_ANR:
   fixes S :: "'a::euclidean_space set"
   assumes "\<And>f :: 'a * real \<Rightarrow> 'a.
            \<And>U T. \<lbrakk>continuous_on T f;  f ` T \<subseteq> S;
                   closedin (top_of_set U) T\<rbrakk>
                  \<Longrightarrow> \<exists>V g. T \<subseteq> V \<and> openin (top_of_set U) V \<and>
                        continuous_on V g \<and> g ` V \<subseteq> S \<and> (\<forall>x \<in> T. g x = f x)"
   shows "ANR S"
 proof (clarsimp simp: ANR_def)
   fix U and T :: "('a * real) set"
   assume "S homeomorphic T" and clo: "closedin (top_of_set U) T"
   then obtain g h where hom: "homeomorphism S T g h"
     by (force simp: homeomorphic_def)
-  have h: "continuous_on T h" " h ` T \<subseteq> S"
-    using hom homeomorphism_def apply blast
-    apply (metis hom equalityE homeomorphism_def)
-    done
+  obtain h: "continuous_on T h" " h ` T \<subseteq> S"
+    using hom homeomorphism_def by blast
   obtain V h' where "T \<subseteq> V" and opV: "openin (top_of_set U) V"
                 and h': "continuous_on V h'" "h' ` V \<subseteq> S"
               and h'h: "\<forall>x\<in>T. h' x = h x"
     using assms [OF h clo] by blast
   have [simp]: "T \<subseteq> U"
     using clo closedin_imp_subset by auto
   have "T retract_of V"
   proof (simp add: retraction_def retract_of_def, intro exI conjI \<open>T \<subseteq> V\<close>)
     show "continuous_on V (g \<circ> h')"
-      apply (intro continuous_on_compose h')
-      apply (meson hom continuous_on_subset h' homeomorphism_cont1)
-      done
+      by (meson continuous_on_compose continuous_on_subset h' hom homeomorphism_cont1)
     show "(g \<circ> h') ` V \<subseteq> T"
       using h'  by clarsimp (metis hom subsetD homeomorphism_def imageI)
     show "\<forall>x\<in>T. (g \<circ> h') x = x"
       by clarsimp (metis h'h hom homeomorphism_def)
   qed
   then show "\<exists>V. openin (top_of_set U) V \<and> T retract_of V"
     using opV by blast
 qed
 
 lemma ANR_eq_absolute_neighbourhood_extensor:
   fixes S :: "'a::euclidean_space set"
   shows "ANR S \<longleftrightarrow>
          (\<forall>f :: 'a * real \<Rightarrow> 'a.
           \<forall>U T. continuous_on T f \<longrightarrow> f ` T \<subseteq> S \<longrightarrow>
                 closedin (top_of_set U) T \<longrightarrow>
                (\<exists>V g. T \<subseteq> V \<and> openin (top_of_set U) V \<and>
-                       continuous_on V g \<and> g ` V \<subseteq> S \<and> (\<forall>x \<in> T. g x = f x)))"
-apply (rule iffI)
- apply (metis ANR_imp_absolute_neighbourhood_extensor)
-apply (simp add: absolute_neighbourhood_extensor_imp_ANR)
-done
+                       continuous_on V g \<and> g ` V \<subseteq> S \<and> (\<forall>x \<in> T. g x = f x)))" (is "_ = ?rhs")
+proof
+  assume "ANR S" then show ?rhs
+    by (metis ANR_imp_absolute_neighbourhood_extensor)
+qed (simp add: absolute_neighbourhood_extensor_imp_ANR)
 
 lemma ANR_imp_neighbourhood_retract:
   fixes S :: "'a::euclidean_space set"
   assumes "ANR S" "closedin (top_of_set U) S"
   obtains V where "openin (top_of_set U) V" "S retract_of V"
 using ANR_imp_absolute_neighbourhood_retract assms homeomorphic_refl by blast
 
 lemma ANR_imp_absolute_closed_neighbourhood_retract:
   fixes S :: "'a::euclidean_space set" and S' :: "'b::euclidean_space set"
   assumes "ANR S" "S homeomorphic S'" and US': "closedin (top_of_set U) S'"
   obtains V W
     where "openin (top_of_set U) V"
           "closedin (top_of_set U) W"
           "S' \<subseteq> V" "V \<subseteq> W" "S' retract_of W"
 proof -
   obtain Z where "openin (top_of_set U) Z" and S'Z: "S' retract_of Z"
     by (blast intro: assms ANR_imp_absolute_neighbourhood_retract)
   then have UUZ: "closedin (top_of_set U) (U - Z)"
     by auto
   have "S' \<inter> (U - Z) = {}"
     using \<open>S' retract_of Z\<close> closedin_retract closedin_subtopology by fastforce
   then obtain V W
       where "openin (top_of_set U) V"
         and "openin (top_of_set U) W"
         and "S' \<subseteq> V" "U - Z \<subseteq> W" "V \<inter> W = {}"
       using separation_normal_local [OF US' UUZ]  by auto
   moreover have "S' retract_of U - W"
-    apply (rule retract_of_subset [OF S'Z])
-    using US' \<open>S' \<subseteq> V\<close> \<open>V \<inter> W = {}\<close> closedin_subset apply fastforce
-    using Diff_subset_conv \<open>U - Z \<subseteq> W\<close> by blast
+  proof (rule retract_of_subset [OF S'Z])
+    show "S' \<subseteq> U - W"
+      using US' \<open>S' \<subseteq> V\<close> \<open>V \<inter> W = {}\<close> closedin_subset by fastforce
+    show "U - W \<subseteq> Z"
+      using Diff_subset_conv \<open>U - Z \<subseteq> W\<close> by blast
+  qed
   ultimately show ?thesis
-    apply (rule_tac V=V and W = "U-W" in that)
-    using openin_imp_subset apply force+
-    done
+    by (metis Diff_subset_conv Diff_triv Int_Diff_Un Int_absorb1 openin_closedin_eq that topspace_euclidean_subtopology)
 qed
 
 lemma ANR_imp_closed_neighbourhood_retract:
   fixes S :: "'a::euclidean_space set"
   assumes "ANR S" "closedin (top_of_set U) S"
   obtains V W where "openin (top_of_set U) V"
                     "closedin (top_of_set U) W"
                     "S \<subseteq> V" "V \<subseteq> W" "S retract_of W"
 by (meson ANR_imp_absolute_closed_neighbourhood_retract assms homeomorphic_refl)
 
 lemma ANR_homeomorphic_ANR:
   fixes S :: "'a::euclidean_space set" and T :: "'b::euclidean_space set"
   assumes "ANR T" "S homeomorphic T"
     shows "ANR S"
 unfolding ANR_def
 by (metis assms ANR_imp_absolute_neighbourhood_retract homeomorphic_trans [of _ S] homeomorphic_sym)
 
 lemma homeomorphic_ANR_iff_ANR:
   fixes S :: "'a::euclidean_space set" and T :: "'b::euclidean_space set"
   shows "S homeomorphic T \<Longrightarrow> ANR S \<longleftrightarrow> ANR T"
 by (metis ANR_homeomorphic_ANR homeomorphic_sym)
 
 subsection \<open>Analogous properties of ENRs\<close>
 
 lemma ENR_imp_absolute_neighbourhood_retract:
   fixes S :: "'a::euclidean_space set" and S' :: "'b::euclidean_space set"
   assumes "ENR S" and hom: "S homeomorphic S'"
       and "S' \<subseteq> U"
   obtains V where "openin (top_of_set U) V" "S' retract_of V"
 proof -
   obtain X where "open X" "S retract_of X"
     using \<open>ENR S\<close> by (auto simp: ENR_def)
   then obtain r where "retraction X S r"
     by (auto simp: retract_of_def)
   have "locally compact S'"
     using retract_of_locally_compact open_imp_locally_compact
           homeomorphic_local_compactness \<open>S retract_of X\<close> \<open>open X\<close> hom by blast
   then obtain W where UW: "openin (top_of_set U) W"
                   and WS': "closedin (top_of_set W) S'"
     apply (rule locally_compact_closedin_open)
-    apply (rename_tac W)
-    apply (rule_tac W = "U \<inter> W" in that, blast)
-    by (simp add: \<open>S' \<subseteq> U\<close> closedin_limpt)
+    by (meson Int_lower2 assms(3) closedin_imp_subset closedin_subset_trans le_inf_iff openin_open)
   obtain f g where hom: "homeomorphism S S' f g"
     using assms by (force simp: homeomorphic_def)
   have contg: "continuous_on S' g"
     using hom homeomorphism_def by blast
   moreover have "g ` S' \<subseteq> S" by (metis hom equalityE homeomorphism_def)
   ultimately obtain h where conth: "continuous_on W h" and hg: "\<And>x. x \<in> S' \<Longrightarrow> h x = g x"
     using Tietze_unbounded [of S' g W] WS' by blast
   have "W \<subseteq> U" using UW openin_open by auto
   have "S' \<subseteq> W" using WS' closedin_closed by auto
   have him: "\<And>x. x \<in> S' \<Longrightarrow> h x \<in> X"
     by (metis (no_types) \<open>S retract_of X\<close> hg hom homeomorphism_def image_insert insert_absorb insert_iff retract_of_imp_subset subset_eq)
   have "S' retract_of (W \<inter> h -` X)"
   proof (simp add: retraction_def retract_of_def, intro exI conjI)
     show "S' \<subseteq> W" "S' \<subseteq> h -` X"
       using him WS' closedin_imp_subset by blast+
     show "continuous_on (W \<inter> h -` X) (f \<circ> r \<circ> h)"
     proof (intro continuous_on_compose)
       show "continuous_on (W \<inter> h -` X) h"
         by (meson conth continuous_on_subset inf_le1)
       show "continuous_on (h ` (W \<inter> h -` X)) r"
       proof -
         have "h ` (W \<inter> h -` X) \<subseteq> X"
           by blast
         then show "continuous_on (h ` (W \<inter> h -` X)) r"
           by (meson \<open>retraction X S r\<close> continuous_on_subset retraction)
       qed
       show "continuous_on (r ` h ` (W \<inter> h -` X)) f"
-        apply (rule continuous_on_subset [of S])
-         using hom homeomorphism_def apply blast
-        apply clarify
-        apply (meson \<open>retraction X S r\<close> subsetD imageI retraction_def)
-        done
+      proof (rule continuous_on_subset [of S])
+        show "continuous_on S f"
+          using hom homeomorphism_def by blast
+        show "r ` h ` (W \<inter> h -` X) \<subseteq> S"
+          by (metis \<open>retraction X S r\<close> image_mono image_subset_iff_subset_vimage inf_le2 retraction)
+      qed
     qed
     show "(f \<circ> r \<circ> h) ` (W \<inter> h -` X) \<subseteq> S'"
       using \<open>retraction X S r\<close> hom
       by (auto simp: retraction_def homeomorphism_def)
     show "\<forall>x\<in>S'. (f \<circ> r \<circ> h) x = x"
       using \<open>retraction X S r\<close> hom by (auto simp: retraction_def homeomorphism_def hg)
   qed
   then show ?thesis
-    apply (rule_tac V = "W \<inter> h -` X" in that)
-     apply (rule openin_trans [OF _ UW])
-     using \<open>continuous_on W h\<close> \<open>open X\<close> continuous_openin_preimage_eq apply blast+
-     done
+    using UW \<open>open X\<close> conth continuous_openin_preimage_eq openin_trans that by blast
 qed
 
 corollary ENR_imp_absolute_neighbourhood_retract_UNIV:
   fixes S :: "'a::euclidean_space set" and S' :: "'b::euclidean_space set"
   assumes "ENR S" "S homeomorphic S'"
   obtains T' where "open T'" "S' retract_of T'"
 by (metis ENR_imp_absolute_neighbourhood_retract UNIV_I assms(1) assms(2) open_openin subsetI subtopology_UNIV)
 
 lemma ENR_homeomorphic_ENR:
   fixes S :: "'a::euclidean_space set" and T :: "'b::euclidean_space set"
   assumes "ENR T" "S homeomorphic T"
     shows "ENR S"
 unfolding ENR_def
 by (meson ENR_imp_absolute_neighbourhood_retract_UNIV assms homeomorphic_sym)
 
 lemma homeomorphic_ENR_iff_ENR:
   fixes S :: "'a::euclidean_space set" and T :: "'b::euclidean_space set"
   assumes "S homeomorphic T"
     shows "ENR S \<longleftrightarrow> ENR T"
 by (meson ENR_homeomorphic_ENR assms homeomorphic_sym)
 
 lemma ENR_translation:
   fixes S :: "'a::euclidean_space set"
   shows "ENR(image (\<lambda>x. a + x) S) \<longleftrightarrow> ENR S"
 by (meson homeomorphic_sym homeomorphic_translation homeomorphic_ENR_iff_ENR)
 
 lemma ENR_linear_image_eq:
   fixes f :: "'a::euclidean_space \<Rightarrow> 'b::euclidean_space"
   assumes "linear f" "inj f"
   shows "ENR (image f S) \<longleftrightarrow> ENR S"
-apply (rule homeomorphic_ENR_iff_ENR)
-using assms homeomorphic_sym linear_homeomorphic_image by auto
+  by (meson assms homeomorphic_ENR_iff_ENR linear_homeomorphic_image)
 
 text \<open>Some relations among the concepts. We also relate AR to being a retract of UNIV, which is
 often a more convenient proxy in the closed case.\<close>
 
 lemma AR_imp_ANR: "AR S \<Longrightarrow> ANR S"
   using ANR_def AR_def by fastforce
 
 lemma ENR_imp_ANR:
   fixes S :: "'a::euclidean_space set"
   shows "ENR S \<Longrightarrow> ANR S"
-apply (simp add: ANR_def)
-by (metis ENR_imp_absolute_neighbourhood_retract closedin_imp_subset)
+  by (meson ANR_def ENR_imp_absolute_neighbourhood_retract closedin_imp_subset)
 
 lemma ENR_ANR:
   fixes S :: "'a::euclidean_space set"
   shows "ENR S \<longleftrightarrow> ANR S \<and> locally compact S"
 proof
   assume "ENR S"
   then have "locally compact S"
     using ENR_def open_imp_locally_compact retract_of_locally_compact by auto
   then show "ANR S \<and> locally compact S"
     using ENR_imp_ANR \<open>ENR S\<close> by blast
 next
   assume "ANR S \<and> locally compact S"
   then have "ANR S" "locally compact S" by auto
   then obtain T :: "('a * real) set" where "closed T" "S homeomorphic T"
     using locally_compact_homeomorphic_closed
     by (metis DIM_prod DIM_real Suc_eq_plus1 lessI)
   then show "ENR S"
     using \<open>ANR S\<close>
-    apply (simp add: ANR_def)
-    apply (drule_tac x=UNIV in spec)
-    apply (drule_tac x=T in spec, clarsimp)
-    apply (meson ENR_def ENR_homeomorphic_ENR open_openin)
-    done
+    by (meson ANR_imp_absolute_neighbourhood_retract_UNIV ENR_def ENR_homeomorphic_ENR)
 qed
 
 
 lemma AR_ANR:
   fixes S :: "'a::euclidean_space set"
   shows "AR S \<longleftrightarrow> ANR S \<and> contractible S \<and> S \<noteq> {}"
         (is "?lhs = ?rhs")
 proof
   assume ?lhs
-  obtain C and S' :: "('a * real) set"
+  have "aff_dim S < int DIM('a \<times> real)"
+      using aff_dim_le_DIM [of S] by auto
+    then obtain C and S' :: "('a * real) set"
     where "convex C" "C \<noteq> {}" "closedin (top_of_set C) S'" "S homeomorphic S'"
-      apply (rule homeomorphic_closedin_convex [of S, where 'n = "'a * real"])
-      using aff_dim_le_DIM [of S] by auto
+    using homeomorphic_closedin_convex by blast
   with \<open>AR S\<close> have "contractible S"
-    apply (simp add: AR_def)
-    apply (drule_tac x=C in spec)
-    apply (drule_tac x="S'" in spec, simp)
-    using convex_imp_contractible homeomorphic_contractible_eq retract_of_contractible by fastforce
+    by (meson AR_def convex_imp_contractible homeomorphic_contractible_eq retract_of_contractible)
   with \<open>AR S\<close> show ?rhs
-    apply (auto simp: AR_imp_ANR)
-    apply (force simp: AR_def)
-    done
+    using AR_imp_ANR AR_imp_retract by fastforce
 next
   assume ?rhs
   then obtain a and h:: "real \<times> 'a \<Rightarrow> 'a"
       where conth: "continuous_on ({0..1} \<times> S) h"
         and hS: "h ` ({0..1} \<times> S) \<subseteq> S"
         and [simp]: "\<And>x. h(0, x) = x"
         and [simp]: "\<And>x. h(1, x) = a"
         and "ANR S" "S \<noteq> {}"
     by (auto simp: contractible_def homotopic_with_def)
   then have "a \<in> S"
     by (metis all_not_in_conv atLeastAtMost_iff image_subset_iff mem_Sigma_iff order_refl zero_le_one)
   have "\<exists>g. continuous_on W g \<and> g ` W \<subseteq> S \<and> (\<forall>x\<in>T. g x = f x)"
          if      f: "continuous_on T f" "f ` T \<subseteq> S"
             and WT: "closedin (top_of_set W) T"
          for W T and f :: "'a \<times> real \<Rightarrow> 'a"
   proof -
     obtain U g
       where "T \<subseteq> U" and WU: "openin (top_of_set W) U"
         and contg: "continuous_on U g"
         and "g ` U \<subseteq> S" and gf: "\<And>x. x \<in> T \<Longrightarrow> g x = f x"
       using iffD1 [OF ANR_eq_absolute_neighbourhood_extensor \<open>ANR S\<close>, rule_format, OF f WT]
       by auto
     have WWU: "closedin (top_of_set W) (W - U)"
       using WU closedin_diff by fastforce
     moreover have "(W - U) \<inter> T = {}"
       using \<open>T \<subseteq> U\<close> by auto
     ultimately obtain V V'
       where WV': "openin (top_of_set W) V'"
         and WV: "openin (top_of_set W) V"
         and "W - U \<subseteq> V'" "T \<subseteq> V" "V' \<inter> V = {}"
       using separation_normal_local [of W "W-U" T] WT by blast
     then have WVT: "T \<inter> (W - V) = {}"
       by auto
     have WWV: "closedin (top_of_set W) (W - V)"
       using WV closedin_diff by fastforce
     obtain j :: " 'a \<times> real \<Rightarrow> real"
       where contj: "continuous_on W j"
         and j:  "\<And>x. x \<in> W \<Longrightarrow> j x \<in> {0..1}"
         and j0: "\<And>x. x \<in> W - V \<Longrightarrow> j x = 1"
         and j1: "\<And>x. x \<in> T \<Longrightarrow> j x = 0"
       by (rule Urysohn_local [OF WT WWV WVT, of 0 "1::real"]) (auto simp: in_segment)
     have Weq: "W = (W - V) \<union> (W - V')"
       using \<open>V' \<inter> V = {}\<close> by force
     show ?thesis
     proof (intro conjI exI)
       have *: "continuous_on (W - V') (\<lambda>x. h (j x, g x))"
-        apply (rule continuous_on_compose2 [OF conth continuous_on_Pair])
-          apply (rule continuous_on_subset [OF contj Diff_subset])
-         apply (rule continuous_on_subset [OF contg])
-         apply (metis Diff_subset_conv Un_commute \<open>W - U \<subseteq> V'\<close>)
-        using j \<open>g ` U \<subseteq> S\<close> \<open>W - U \<subseteq> V'\<close> apply fastforce
-        done
+      proof (rule continuous_on_compose2 [OF conth continuous_on_Pair])
+        show "continuous_on (W - V') j"
+          by (rule continuous_on_subset [OF contj Diff_subset])
+        show "continuous_on (W - V') g"
+          by (metis Diff_subset_conv \<open>W - U \<subseteq> V'\<close> contg continuous_on_subset Un_commute)
+        show "(\<lambda>x. (j x, g x)) ` (W - V') \<subseteq> {0..1} \<times> S"
+          using j \<open>g ` U \<subseteq> S\<close> \<open>W - U \<subseteq> V'\<close> by fastforce
+      qed
       show "continuous_on W (\<lambda>x. if x \<in> W - V then a else h (j x, g x))"
-        apply (subst Weq)
-        apply (rule continuous_on_cases_local)
-            apply (simp_all add: Weq [symmetric] WWV *)
-          using WV' closedin_diff apply fastforce
-         apply (auto simp: j0 j1)
-        done
+      proof (subst Weq, rule continuous_on_cases_local)
+        show "continuous_on (W - V') (\<lambda>x. h (j x, g x))"
+          using "*" by blast
+      qed (use WWV WV' Weq j0 j1 in auto)
     next
       have "h (j (x, y), g (x, y)) \<in> S" if "(x, y) \<in> W" "(x, y) \<in> V" for x y
       proof -
         have "j(x, y) \<in> {0..1}"
           using j that by blast
         moreover have "g(x, y) \<in> S"
           using \<open>V' \<inter> V = {}\<close> \<open>W - U \<subseteq> V'\<close> \<open>g ` U \<subseteq> S\<close> that by fastforce
         ultimately show ?thesis
           using hS by blast
       qed
       with \<open>a \<in> S\<close> \<open>g ` U \<subseteq> S\<close>
       show "(\<lambda>x. if x \<in> W - V then a else h (j x, g x)) ` W \<subseteq> S"
         by auto
     next
       show "\<forall>x\<in>T. (if x \<in> W - V then a else h (j x, g x)) = f x"
         using \<open>T \<subseteq> V\<close> by (auto simp: j0 j1 gf)
     qed
   qed
   then show ?lhs
     by (simp add: AR_eq_absolute_extensor)
 qed
 
 
 lemma ANR_retract_of_ANR:
   fixes S :: "'a::euclidean_space set"
-  assumes "ANR T" "S retract_of T"
+  assumes "ANR T" and ST: "S retract_of T"
   shows "ANR S"
-using assms
-apply (simp add: ANR_eq_absolute_neighbourhood_extensor retract_of_def retraction_def)
-apply (clarsimp elim!: all_forward)
-apply (erule impCE, metis subset_trans)
-apply (clarsimp elim!: ex_forward)
-apply (rule_tac x="r \<circ> g" in exI)
-by (metis comp_apply continuous_on_compose continuous_on_subset subsetD imageI image_comp image_mono subset_trans)
+proof (clarsimp simp add: ANR_eq_absolute_neighbourhood_extensor)
+  fix f::"'a \<times> real \<Rightarrow> 'a" and U W
+  assume W: "continuous_on W f" "f ` W \<subseteq> S" "closedin (top_of_set U) W"
+  then obtain r where "S \<subseteq> T" and r: "continuous_on T r" "r ` T \<subseteq> S" "\<forall>x\<in>S. r x = x" "continuous_on W f" "f ` W \<subseteq> S"
+                                     "closedin (top_of_set U) W"
+    by (meson ST retract_of_def retraction_def)
+  then have "f ` W \<subseteq> T"
+    by blast
+  with W obtain V g where V: "W \<subseteq> V" "openin (top_of_set U) V" "continuous_on V g" "g ` V \<subseteq> T" "\<forall>x\<in>W. g x = f x"
+    by (metis ANR_imp_absolute_neighbourhood_extensor \<open>ANR T\<close>)
+  with r have "continuous_on V (r \<circ> g) \<and> (r \<circ> g) ` V \<subseteq> S \<and> (\<forall>x\<in>W. (r \<circ> g) x = f x)"
+    by (metis (no_types, lifting) comp_apply continuous_on_compose continuous_on_subset image_subset_iff)
+  then show "\<exists>V. W \<subseteq> V \<and> openin (top_of_set U) V \<and> (\<exists>g. continuous_on V g \<and> g ` V \<subseteq> S \<and> (\<forall>x\<in>W. g x = f x))"
+    by (meson V)
+qed
 
 lemma AR_retract_of_AR:
   fixes S :: "'a::euclidean_space set"
   shows "\<lbrakk>AR T; S retract_of T\<rbrakk> \<Longrightarrow> AR S"
 using ANR_retract_of_ANR AR_ANR retract_of_contractible by fastforce
 
 lemma ENR_retract_of_ENR:
    "\<lbrakk>ENR T; S retract_of T\<rbrakk> \<Longrightarrow> ENR S"
 by (meson ENR_def retract_of_trans)
 
 lemma retract_of_UNIV:
   fixes S :: "'a::euclidean_space set"
   shows "S retract_of UNIV \<longleftrightarrow> AR S \<and> closed S"
 by (metis AR_ANR AR_imp_retract ENR_def ENR_imp_ANR closed_UNIV closed_closedin contractible_UNIV empty_not_UNIV open_UNIV retract_of_closed retract_of_contractible retract_of_empty(1) subtopology_UNIV)
 
 lemma compact_AR:
   fixes S :: "'a::euclidean_space set"
   shows "compact S \<and> AR S \<longleftrightarrow> compact S \<and> S retract_of UNIV"
 using compact_imp_closed retract_of_UNIV by blast
 
 text \<open>More properties of ARs, ANRs and ENRs\<close>
 
 lemma not_AR_empty [simp]: "\<not> AR({})"
   by (auto simp: AR_def)
 
 lemma ENR_empty [simp]: "ENR {}"
   by (simp add: ENR_def)
 
 lemma ANR_empty [simp]: "ANR ({} :: 'a::euclidean_space set)"
   by (simp add: ENR_imp_ANR)
 
 lemma convex_imp_AR:
   fixes S :: "'a::euclidean_space set"
   shows "\<lbrakk>convex S; S \<noteq> {}\<rbrakk> \<Longrightarrow> AR S"
-apply (rule absolute_extensor_imp_AR)
-apply (rule Dugundji, assumption+)
-by blast
+  by (metis (mono_tags, lifting) Dugundji absolute_extensor_imp_AR)
 
 lemma convex_imp_ANR:
   fixes S :: "'a::euclidean_space set"
   shows "convex S \<Longrightarrow> ANR S"
 using ANR_empty AR_imp_ANR convex_imp_AR by blast
 
 lemma ENR_convex_closed:
   fixes S :: "'a::euclidean_space set"
   shows "\<lbrakk>closed S; convex S\<rbrakk> \<Longrightarrow> ENR S"
 using ENR_def ENR_empty convex_imp_AR retract_of_UNIV by blast
 
 lemma AR_UNIV [simp]: "AR (UNIV :: 'a::euclidean_space set)"
   using retract_of_UNIV by auto
 
 lemma ANR_UNIV [simp]: "ANR (UNIV :: 'a::euclidean_space set)"
   by (simp add: AR_imp_ANR)
 
 lemma ENR_UNIV [simp]:"ENR UNIV"
   using ENR_def by blast
 
 lemma AR_singleton:
     fixes a :: "'a::euclidean_space"
     shows "AR {a}"
   using retract_of_UNIV by blast
 
 lemma ANR_singleton:
     fixes a :: "'a::euclidean_space"
     shows "ANR {a}"
   by (simp add: AR_imp_ANR AR_singleton)
 
 lemma ENR_singleton: "ENR {a}"
   using ENR_def by blast
 
 text \<open>ARs closed under union\<close>
 
 lemma AR_closed_Un_local_aux:
   fixes U :: "'a::euclidean_space set"
   assumes "closedin (top_of_set U) S"
           "closedin (top_of_set U) T"
           "AR S" "AR T" "AR(S \<inter> T)"
   shows "(S \<union> T) retract_of U"
 proof -
   have "S \<inter> T \<noteq> {}"
     using assms AR_def by fastforce
   have "S \<subseteq> U" "T \<subseteq> U"
     using assms by (auto simp: closedin_imp_subset)
   define S' where "S' \<equiv> {x \<in> U. setdist {x} S \<le> setdist {x} T}"
   define T' where "T' \<equiv> {x \<in> U. setdist {x} T \<le> setdist {x} S}"
   define W  where "W \<equiv> {x \<in> U. setdist {x} S = setdist {x} T}"
   have US': "closedin (top_of_set U) S'"
     using continuous_closedin_preimage [of U "\<lambda>x. setdist {x} S - setdist {x} T" "{..0}"]
     by (simp add: S'_def vimage_def Collect_conj_eq continuous_on_diff continuous_on_setdist)
   have UT': "closedin (top_of_set U) T'"
     using continuous_closedin_preimage [of U "\<lambda>x. setdist {x} T - setdist {x} S" "{..0}"]
     by (simp add: T'_def vimage_def Collect_conj_eq continuous_on_diff continuous_on_setdist)
   have "S \<subseteq> S'"
     using S'_def \<open>S \<subseteq> U\<close> setdist_sing_in_set by fastforce
   have "T \<subseteq> T'"
     using T'_def \<open>T \<subseteq> U\<close> setdist_sing_in_set by fastforce
   have "S \<inter> T \<subseteq> W" "W \<subseteq> U"
     using \<open>S \<subseteq> U\<close> by (auto simp: W_def setdist_sing_in_set)
   have "(S \<inter> T) retract_of W"
-    apply (rule AR_imp_absolute_retract [OF \<open>AR(S \<inter> T)\<close>])
-     apply (simp add: homeomorphic_refl)
-    apply (rule closedin_subset_trans [of U])
-    apply (simp_all add: assms closedin_Int \<open>S \<inter> T \<subseteq> W\<close> \<open>W \<subseteq> U\<close>)
-    done
+  proof (rule AR_imp_absolute_retract [OF \<open>AR(S \<inter> T)\<close>])
+    show "S \<inter> T homeomorphic S \<inter> T"
+      by (simp add: homeomorphic_refl)
+    show "closedin (top_of_set W) (S \<inter> T)"
+      by (meson \<open>S \<inter> T \<subseteq> W\<close> \<open>W \<subseteq> U\<close> assms closedin_Int closedin_subset_trans)
+  qed
   then obtain r0
     where "S \<inter> T \<subseteq> W" and contr0: "continuous_on W r0"
       and "r0 ` W \<subseteq> S \<inter> T"
       and r0 [simp]: "\<And>x. x \<in> S \<inter> T \<Longrightarrow> r0 x = x"
       by (auto simp: retract_of_def retraction_def)
   have ST: "x \<in> W \<Longrightarrow> x \<in> S \<longleftrightarrow> x \<in> T" for x
     using setdist_eq_0_closedin \<open>S \<inter> T \<noteq> {}\<close> assms
     by (force simp: W_def setdist_sing_in_set)
   have "S' \<inter> T' = W"
     by (auto simp: S'_def T'_def W_def)
   then have cloUW: "closedin (top_of_set U) W"
     using closedin_Int US' UT' by blast
   define r where "r \<equiv> \<lambda>x. if x \<in> W then r0 x else x"
-  have "r ` (W \<union> S) \<subseteq> S" "r ` (W \<union> T) \<subseteq> T"
-    using \<open>r0 ` W \<subseteq> S \<inter> T\<close> r_def by auto
   have contr: "continuous_on (W \<union> (S \<union> T)) r"
   unfolding r_def
   proof (rule continuous_on_cases_local [OF _ _ contr0 continuous_on_id])
     show "closedin (top_of_set (W \<union> (S \<union> T))) W"
       using \<open>S \<subseteq> U\<close> \<open>T \<subseteq> U\<close> \<open>W \<subseteq> U\<close> \<open>closedin (top_of_set U) W\<close> closedin_subset_trans by fastforce
     show "closedin (top_of_set (W \<union> (S \<union> T))) (S \<union> T)"
       by (meson \<open>S \<subseteq> U\<close> \<open>T \<subseteq> U\<close> \<open>W \<subseteq> U\<close> assms closedin_Un closedin_subset_trans sup.bounded_iff sup.cobounded2)
     show "\<And>x. x \<in> W \<and> x \<notin> W \<or> x \<in> S \<union> T \<and> x \<in> W \<Longrightarrow> r0 x = x"
       by (auto simp: ST)
   qed
+  have rim: "r ` (W \<union> S) \<subseteq> S" "r ` (W \<union> T) \<subseteq> T"
+    using \<open>r0 ` W \<subseteq> S \<inter> T\<close> r_def by auto
   have cloUWS: "closedin (top_of_set U) (W \<union> S)"
     by (simp add: cloUW assms closedin_Un)
   obtain g where contg: "continuous_on U g"
-             and "g ` U \<subseteq> S" and geqr: "\<And>x. x \<in> W \<union> S \<Longrightarrow> g x = r x"
-    apply (rule AR_imp_absolute_extensor [OF \<open>AR S\<close> _ _ cloUWS])
-      apply (rule continuous_on_subset [OF contr])
-      using \<open>r ` (W \<union> S) \<subseteq> S\<close> apply auto
-    done
+    and "g ` U \<subseteq> S" and geqr: "\<And>x. x \<in> W \<union> S \<Longrightarrow> g x = r x"
+  proof (rule AR_imp_absolute_extensor [OF \<open>AR S\<close> _ _ cloUWS])
+    show "continuous_on (W \<union> S) r"
+      using continuous_on_subset contr sup_assoc by blast
+  qed (use rim in auto)
   have cloUWT: "closedin (top_of_set U) (W \<union> T)"
     by (simp add: cloUW assms closedin_Un)
   obtain h where conth: "continuous_on U h"
              and "h ` U \<subseteq> T" and heqr: "\<And>x. x \<in> W \<union> T \<Longrightarrow> h x = r x"
-    apply (rule AR_imp_absolute_extensor [OF \<open>AR T\<close> _ _ cloUWT])
-      apply (rule continuous_on_subset [OF contr])
-      using \<open>r ` (W \<union> T) \<subseteq> T\<close> apply auto
-    done
-  have "U = S' \<union> T'"
+  proof (rule AR_imp_absolute_extensor [OF \<open>AR T\<close> _ _ cloUWT])
+    show "continuous_on (W \<union> T) r"
+      using continuous_on_subset contr sup_assoc by blast
+  qed (use rim in auto)
+  have U: "U = S' \<union> T'"
     by (force simp: S'_def T'_def)
-  then have cont: "continuous_on U (\<lambda>x. if x \<in> S' then g x else h x)"
-    apply (rule ssubst)
+  have cont: "continuous_on U (\<lambda>x. if x \<in> S' then g x else h x)"
+    unfolding U
     apply (rule continuous_on_cases_local)
     using US' UT' \<open>S' \<inter> T' = W\<close> \<open>U = S' \<union> T'\<close>
-          contg conth continuous_on_subset geqr heqr apply auto
-    done
+          contg conth continuous_on_subset geqr heqr by auto
   have UST: "(\<lambda>x. if x \<in> S' then g x else h x) ` U \<subseteq> S \<union> T"
     using \<open>g ` U \<subseteq> S\<close> \<open>h ` U \<subseteq> T\<close> by auto
   show ?thesis
     apply (simp add: retract_of_def retraction_def \<open>S \<subseteq> U\<close> \<open>T \<subseteq> U\<close>)
     apply (rule_tac x="\<lambda>x. if x \<in> S' then g x else h x" in exI)
-    apply (intro conjI cont UST)
-    by (metis IntI ST Un_iff \<open>S \<subseteq> S'\<close> \<open>S' \<inter> T' = W\<close> \<open>T \<subseteq> T'\<close> subsetD geqr heqr r0 r_def)
+    using ST UST \<open>S \<subseteq> S'\<close> \<open>S' \<inter> T' = W\<close> \<open>T \<subseteq> T'\<close> cont geqr heqr r_def by auto
 qed
 
 
 lemma AR_closed_Un_local:
   fixes S :: "'a::euclidean_space set"
   assumes STS: "closedin (top_of_set (S \<union> T)) S"
       and STT: "closedin (top_of_set (S \<union> T)) T"
       and "AR S" "AR T" "AR(S \<inter> T)"
     shows "AR(S \<union> T)"
 proof -
   have "C retract_of U"
        if hom: "S \<union> T homeomorphic C" and UC: "closedin (top_of_set U) C"
        for U and C :: "('a * real) set"
   proof -
     obtain f g where hom: "homeomorphism (S \<union> T) C f g"
       using hom by (force simp: homeomorphic_def)
     have US: "closedin (top_of_set U) (C \<inter> g -` S)"
-      apply (rule closedin_trans [OF _ UC])
-      apply (rule continuous_closedin_preimage_gen [OF _ _ STS])
-      using hom homeomorphism_def apply blast
-      apply (metis hom homeomorphism_def set_eq_subset)
-      done
+      by (metis STS continuous_on_imp_closedin hom homeomorphism_def closedin_trans [OF _ UC])
     have UT: "closedin (top_of_set U) (C \<inter> g -` T)"
-      apply (rule closedin_trans [OF _ UC])
-      apply (rule continuous_closedin_preimage_gen [OF _ _ STT])
-      using hom homeomorphism_def apply blast
-      apply (metis hom homeomorphism_def set_eq_subset)
-      done
-    have ARS: "AR (C \<inter> g -` S)"
-      apply (rule AR_homeomorphic_AR [OF \<open>AR S\<close>])
-      apply (simp add: homeomorphic_def)
-      apply (rule_tac x=g in exI)
-      apply (rule_tac x=f in exI)
-      using hom apply (auto simp: homeomorphism_def elim!: continuous_on_subset)
+      by (metis STT continuous_on_closed hom homeomorphism_def closedin_trans [OF _ UC])
+    have "homeomorphism (C \<inter> g -` S) S g f"
+      using hom 
+      apply (auto simp: homeomorphism_def elim!: continuous_on_subset)
       apply (rule_tac x="f x" in image_eqI, auto)
       done
-    have ART: "AR (C \<inter> g -` T)"
-      apply (rule AR_homeomorphic_AR [OF \<open>AR T\<close>])
-      apply (simp add: homeomorphic_def)
-      apply (rule_tac x=g in exI)
-      apply (rule_tac x=f in exI)
-      using hom apply (auto simp: homeomorphism_def elim!: continuous_on_subset)
+    then have ARS: "AR (C \<inter> g -` S)"
+      using \<open>AR S\<close> homeomorphic_AR_iff_AR homeomorphic_def by blast
+    have "homeomorphism (C \<inter> g -` T) T g f"
+      using hom 
+      apply (auto simp: homeomorphism_def elim!: continuous_on_subset)
       apply (rule_tac x="f x" in image_eqI, auto)
       done
-    have ARI: "AR ((C \<inter> g -` S) \<inter> (C \<inter> g -` T))"
-      apply (rule AR_homeomorphic_AR [OF \<open>AR (S \<inter> T)\<close>])
-      apply (simp add: homeomorphic_def)
-      apply (rule_tac x=g in exI)
-      apply (rule_tac x=f in exI)
+    then have ART: "AR (C \<inter> g -` T)"
+      using \<open>AR T\<close> homeomorphic_AR_iff_AR homeomorphic_def by blast
+    have "homeomorphism (C \<inter> g -` S \<inter> (C \<inter> g -` T)) (S \<inter> T) g f"
       using hom
       apply (auto simp: homeomorphism_def elim!: continuous_on_subset)
       apply (rule_tac x="f x" in image_eqI, auto)
       done
+    then have ARI: "AR ((C \<inter> g -` S) \<inter> (C \<inter> g -` T))"
+      using \<open>AR (S \<inter> T)\<close> homeomorphic_AR_iff_AR homeomorphic_def by blast
     have "C = (C \<inter> g -` S) \<union> (C \<inter> g -` T)"
       using hom  by (auto simp: homeomorphism_def)
     then show ?thesis
       by (metis AR_closed_Un_local_aux [OF US UT ARS ART ARI])
   qed
   then show ?thesis
     by (force simp: AR_def)
 qed
 
 corollary AR_closed_Un:
   fixes S :: "'a::euclidean_space set"
   shows "\<lbrakk>closed S; closed T; AR S; AR T; AR (S \<inter> T)\<rbrakk> \<Longrightarrow> AR (S \<union> T)"
 by (metis AR_closed_Un_local_aux closed_closedin retract_of_UNIV subtopology_UNIV)
 
 text \<open>ANRs closed under union\<close>
 
 lemma ANR_closed_Un_local_aux:
   fixes U :: "'a::euclidean_space set"
   assumes US: "closedin (top_of_set U) S"
       and UT: "closedin (top_of_set U) T"
       and "ANR S" "ANR T" "ANR(S \<inter> T)"
   obtains V where "openin (top_of_set U) V" "(S \<union> T) retract_of V"
 proof (cases "S = {} \<or> T = {}")
   case True with assms that show ?thesis
     by (metis ANR_imp_neighbourhood_retract Un_commute inf_bot_right sup_inf_absorb)
 next
   case False
   then have [simp]: "S \<noteq> {}" "T \<noteq> {}" by auto
   have "S \<subseteq> U" "T \<subseteq> U"
     using assms by (auto simp: closedin_imp_subset)
   define S' where "S' \<equiv> {x \<in> U. setdist {x} S \<le> setdist {x} T}"
   define T' where "T' \<equiv> {x \<in> U. setdist {x} T \<le> setdist {x} S}"
   define W  where "W \<equiv> {x \<in> U. setdist {x} S = setdist {x} T}"
   have cloUS': "closedin (top_of_set U) S'"
     using continuous_closedin_preimage [of U "\<lambda>x. setdist {x} S - setdist {x} T" "{..0}"]
     by (simp add: S'_def vimage_def Collect_conj_eq continuous_on_diff continuous_on_setdist)
   have cloUT': "closedin (top_of_set U) T'"
     using continuous_closedin_preimage [of U "\<lambda>x. setdist {x} T - setdist {x} S" "{..0}"]
     by (simp add: T'_def vimage_def Collect_conj_eq continuous_on_diff continuous_on_setdist)
   have "S \<subseteq> S'"
     using S'_def \<open>S \<subseteq> U\<close> setdist_sing_in_set by fastforce
   have "T \<subseteq> T'"
     using T'_def \<open>T \<subseteq> U\<close> setdist_sing_in_set by fastforce
   have "S' \<union> T' = U"
     by (auto simp: S'_def T'_def)
   have "W \<subseteq> S'"
     by (simp add: Collect_mono S'_def W_def)
   have "W \<subseteq> T'"
     by (simp add: Collect_mono T'_def W_def)
   have ST_W: "S \<inter> T \<subseteq> W" and "W \<subseteq> U"
     using \<open>S \<subseteq> U\<close> by (force simp: W_def setdist_sing_in_set)+
   have "S' \<inter> T' = W"
     by (auto simp: S'_def T'_def W_def)
   then have cloUW: "closedin (top_of_set U) W"
     using closedin_Int cloUS' cloUT' by blast
   obtain W' W0 where "openin (top_of_set W) W'"
                  and cloWW0: "closedin (top_of_set W) W0"
                  and "S \<inter> T \<subseteq> W'" "W' \<subseteq> W0"
                  and ret: "(S \<inter> T) retract_of W0"
-    apply (rule ANR_imp_closed_neighbourhood_retract [OF \<open>ANR(S \<inter> T)\<close>])
-    apply (rule closedin_subset_trans [of U, OF _ ST_W \<open>W \<subseteq> U\<close>])
-    apply (blast intro: assms)+
-    done
+    by (meson ANR_imp_closed_neighbourhood_retract ST_W US UT \<open>W \<subseteq> U\<close> \<open>ANR(S \<inter> T)\<close> closedin_Int closedin_subset_trans)
   then obtain U0 where opeUU0: "openin (top_of_set U) U0"
                    and U0: "S \<inter> T \<subseteq> U0" "U0 \<inter> W \<subseteq> W0"
     unfolding openin_open  using \<open>W \<subseteq> U\<close> by blast
   have "W0 \<subseteq> U"
     using \<open>W \<subseteq> U\<close> cloWW0 closedin_subset by fastforce
   obtain r0
     where "S \<inter> T \<subseteq> W0" and contr0: "continuous_on W0 r0" and "r0 ` W0 \<subseteq> S \<inter> T"
       and r0 [simp]: "\<And>x. x \<in> S \<inter> T \<Longrightarrow> r0 x = x"
     using ret  by (force simp: retract_of_def retraction_def)
   have ST: "x \<in> W \<Longrightarrow> x \<in> S \<longleftrightarrow> x \<in> T" for x
     using assms by (auto simp: W_def setdist_sing_in_set dest!: setdist_eq_0_closedin)
   define r where "r \<equiv> \<lambda>x. if x \<in> W0 then r0 x else x"
   have "r ` (W0 \<union> S) \<subseteq> S" "r ` (W0 \<union> T) \<subseteq> T"
     using \<open>r0 ` W0 \<subseteq> S \<inter> T\<close> r_def by auto
   have contr: "continuous_on (W0 \<union> (S \<union> T)) r"
   unfolding r_def
   proof (rule continuous_on_cases_local [OF _ _ contr0 continuous_on_id])
     show "closedin (top_of_set (W0 \<union> (S \<union> T))) W0"
-      apply (rule closedin_subset_trans [of U])
-      using cloWW0 cloUW closedin_trans \<open>W0 \<subseteq> U\<close> \<open>S \<subseteq> U\<close> \<open>T \<subseteq> U\<close> apply blast+
-      done
+      using closedin_subset_trans [of U]
+      by (metis le_sup_iff order_refl cloWW0 cloUW closedin_trans \<open>W0 \<subseteq> U\<close> \<open>S \<subseteq> U\<close> \<open>T \<subseteq> U\<close>)
     show "closedin (top_of_set (W0 \<union> (S \<union> T))) (S \<union> T)"
       by (meson \<open>S \<subseteq> U\<close> \<open>T \<subseteq> U\<close> \<open>W0 \<subseteq> U\<close> assms closedin_Un closedin_subset_trans sup.bounded_iff sup.cobounded2)
     show "\<And>x. x \<in> W0 \<and> x \<notin> W0 \<or> x \<in> S \<union> T \<and> x \<in> W0 \<Longrightarrow> r0 x = x"
       using ST cloWW0 closedin_subset by fastforce
   qed
   have cloS'WS: "closedin (top_of_set S') (W0 \<union> S)"
     by (meson closedin_subset_trans US cloUS' \<open>S \<subseteq> S'\<close> \<open>W \<subseteq> S'\<close> cloUW cloWW0 
               closedin_Un closedin_imp_subset closedin_trans)
   obtain W1 g where "W0 \<union> S \<subseteq> W1" and contg: "continuous_on W1 g"
                 and opeSW1: "openin (top_of_set S') W1"
                 and "g ` W1 \<subseteq> S" and geqr: "\<And>x. x \<in> W0 \<union> S \<Longrightarrow> g x = r x"
-    apply (rule ANR_imp_absolute_neighbourhood_extensor [OF \<open>ANR S\<close> _ \<open>r ` (W0 \<union> S) \<subseteq> S\<close> cloS'WS])
-     apply (rule continuous_on_subset [OF contr], blast+)
-    done
+  proof (rule ANR_imp_absolute_neighbourhood_extensor [OF \<open>ANR S\<close> _ \<open>r ` (W0 \<union> S) \<subseteq> S\<close> cloS'WS])
+    show "continuous_on (W0 \<union> S) r"
+      using continuous_on_subset contr sup_assoc by blast
+  qed auto
   have cloT'WT: "closedin (top_of_set T') (W0 \<union> T)"
     by (meson closedin_subset_trans UT cloUT' \<open>T \<subseteq> T'\<close> \<open>W \<subseteq> T'\<close> cloUW cloWW0 
               closedin_Un closedin_imp_subset closedin_trans)
   obtain W2 h where "W0 \<union> T \<subseteq> W2" and conth: "continuous_on W2 h"
                 and opeSW2: "openin (top_of_set T') W2"
                 and "h ` W2 \<subseteq> T" and heqr: "\<And>x. x \<in> W0 \<union> T \<Longrightarrow> h x = r x"
-    apply (rule ANR_imp_absolute_neighbourhood_extensor [OF \<open>ANR T\<close> _ \<open>r ` (W0 \<union> T) \<subseteq> T\<close> cloT'WT])
-     apply (rule continuous_on_subset [OF contr], blast+)
-    done
+  proof (rule ANR_imp_absolute_neighbourhood_extensor [OF \<open>ANR T\<close> _ \<open>r ` (W0 \<union> T) \<subseteq> T\<close> cloT'WT])
+    show "continuous_on (W0 \<union> T) r"
+      using continuous_on_subset contr sup_assoc by blast
+  qed auto
   have "S' \<inter> T' = W"
     by (force simp: S'_def T'_def W_def)
-  obtain O1 O2 where "open O1" "W1 = S' \<inter> O1" "open O2" "W2 = T' \<inter> O2"
+  obtain O1 O2 where O12: "open O1" "W1 = S' \<inter> O1" "open O2" "W2 = T' \<inter> O2"
     using opeSW1 opeSW2 by (force simp: openin_open)
   show ?thesis
   proof
-    have eq: "W1 - (W - U0) \<union> (W2 - (W - U0)) =
-         ((U - T') \<inter> O1 \<union> (U - S') \<inter> O2 \<union> U \<inter> O1 \<inter> O2) - (W - U0)"
-     using \<open>U0 \<inter> W \<subseteq> W0\<close> \<open>W0 \<union> S \<subseteq> W1\<close> \<open>W0 \<union> T \<subseteq> W2\<close>
+    have eq: "W1 - (W - U0) \<union> (W2 - (W - U0)) 
+            = ((U - T') \<inter> O1 \<union> (U - S') \<inter> O2 \<union> U \<inter> O1 \<inter> O2) - (W - U0)" (is "?WW1 \<union> ?WW2 = ?rhs")
+      using \<open>U0 \<inter> W \<subseteq> W0\<close> \<open>W0 \<union> S \<subseteq> W1\<close> \<open>W0 \<union> T \<subseteq> W2\<close>
       by (auto simp: \<open>S' \<union> T' = U\<close> [symmetric] \<open>S' \<inter> T' = W\<close> [symmetric] \<open>W1 = S' \<inter> O1\<close> \<open>W2 = T' \<inter> O2\<close>)
-    show "openin (top_of_set U) (W1 - (W - U0) \<union> (W2 - (W - U0)))"
-      apply (subst eq)
-      apply (intro openin_Un openin_Int_open openin_diff closedin_diff cloUW opeUU0 cloUS' cloUT' \<open>open O1\<close> \<open>open O2\<close>, simp_all)
-      done
-    have cloW1: "closedin (top_of_set (W1 - (W - U0) \<union> (W2 - (W - U0)))) (W1 - (W - U0))"
-      using cloUS' apply (simp add: closedin_closed)
-      apply (erule ex_forward)
-      using U0 \<open>W0 \<union> S \<subseteq> W1\<close>
-      apply (auto simp: \<open>W1 = S' \<inter> O1\<close> \<open>W2 = T' \<inter> O2\<close> \<open>S' \<union> T' = U\<close> [symmetric]\<open>S' \<inter> T' = W\<close> [symmetric])
-      done
-    have cloW2: "closedin (top_of_set (W1 - (W - U0) \<union> (W2 - (W - U0)))) (W2 - (W - U0))"
-      using cloUT' apply (simp add: closedin_closed)
-      apply (erule ex_forward)
-      using U0 \<open>W0 \<union> T \<subseteq> W2\<close>
-      apply (auto simp: \<open>W1 = S' \<inter> O1\<close> \<open>W2 = T' \<inter> O2\<close> \<open>S' \<union> T' = U\<close> [symmetric]\<open>S' \<inter> T' = W\<close> [symmetric])
-      done
-    have *: "\<forall>x\<in>S \<union> T. (if x \<in> S' then g x else h x) = x"
-      using ST \<open>S' \<inter> T' = W\<close> cloT'WT closedin_subset geqr heqr 
-      apply (auto simp: r_def, fastforce)
-      using \<open>S \<subseteq> S'\<close> \<open>T \<subseteq> T'\<close> \<open>W0 \<union> S \<subseteq> W1\<close> \<open>W1 = S' \<inter> O1\<close>  by auto
-    have "\<exists>r. continuous_on (W1 - (W - U0) \<union> (W2 - (W - U0))) r \<and>
-              r ` (W1 - (W - U0) \<union> (W2 - (W - U0))) \<subseteq> S \<union> T \<and> 
-              (\<forall>x\<in>S \<union> T. r x = x)"
-      apply (rule_tac x = "\<lambda>x. if  x \<in> S' then g x else h x" in exI)
-      apply (intro conjI *)
-      apply (rule continuous_on_cases_local 
-                  [OF cloW1 cloW2 continuous_on_subset [OF contg] continuous_on_subset [OF conth]])
-      using \<open>W1 = S' \<inter> O1\<close> \<open>W2 = T' \<inter> O2\<close> \<open>S' \<inter> T' = W\<close>
-            \<open>g ` W1 \<subseteq> S\<close> \<open>h ` W2 \<subseteq> T\<close> apply auto
-      using \<open>U0 \<inter> W \<subseteq> W0\<close> \<open>W0 \<union> S \<subseteq> W1\<close> apply (fastforce simp add: geqr heqr)+
-      done
-    then show "S \<union> T retract_of W1 - (W - U0) \<union> (W2 - (W - U0))"
+    show "openin (top_of_set U) (?WW1 \<union> ?WW2)"
+      by (simp add: eq \<open>open O1\<close> \<open>open O2\<close> cloUS' cloUT' cloUW closedin_diff opeUU0 openin_Int_open openin_Un openin_diff)
+    obtain SU' where "closed SU'" "S' = U \<inter> SU'"
+      using cloUS' by (auto simp add: closedin_closed)
+    moreover have "?WW1 = (?WW1 \<union> ?WW2) \<inter> SU'"
+      using \<open>S' = U \<inter> SU'\<close> \<open>W1 = S' \<inter> O1\<close> \<open>S' \<union> T' = U\<close> \<open>W2 = T' \<inter> O2\<close>  \<open>S' \<inter> T' = W\<close> \<open>W0 \<union> S \<subseteq> W1\<close> U0
+      by auto
+    ultimately have cloW1: "closedin (top_of_set (W1 - (W - U0) \<union> (W2 - (W - U0)))) (W1 - (W - U0))"
+      by (metis closedin_closed_Int)
+    obtain TU' where "closed TU'" "T' = U \<inter> TU'"
+      using cloUT' by (auto simp add: closedin_closed)
+    moreover have "?WW2 = (?WW1 \<union> ?WW2) \<inter> TU'"
+      using \<open>T' = U \<inter> TU'\<close> \<open>W1 = S' \<inter> O1\<close> \<open>S' \<union> T' = U\<close> \<open>W2 = T' \<inter> O2\<close>  \<open>S' \<inter> T' = W\<close> \<open>W0 \<union> T \<subseteq> W2\<close> U0
+      by auto
+    ultimately have cloW2: "closedin (top_of_set (?WW1 \<union> ?WW2)) ?WW2"
+      by (metis closedin_closed_Int)
+    let ?gh = "\<lambda>x. if x \<in> S' then g x else h x"
+    have "\<exists>r. continuous_on (?WW1 \<union> ?WW2) r \<and> r ` (?WW1 \<union> ?WW2) \<subseteq> S \<union> T \<and> (\<forall>x\<in>S \<union> T. r x = x)"
+    proof (intro exI conjI)
+      show "\<forall>x\<in>S \<union> T. ?gh x = x"
+        using ST \<open>S' \<inter> T' = W\<close> geqr heqr O12  
+        by (metis Int_iff Un_iff \<open>W0 \<union> S \<subseteq> W1\<close> \<open>W0 \<union> T \<subseteq> W2\<close> r0 r_def sup.order_iff)  
+      have "\<And>x. x \<in> ?WW1 \<and> x \<notin> S' \<or> x \<in> ?WW2 \<and> x \<in> S' \<Longrightarrow> g x = h x"
+        using O12
+        by (metis (full_types) DiffD1 DiffD2 DiffI IntE IntI U0(2) UnCI \<open>S' \<inter> T' = W\<close> geqr heqr in_mono)
+      then show "continuous_on (?WW1 \<union> ?WW2) ?gh"
+        using continuous_on_cases_local [OF cloW1 cloW2 continuous_on_subset [OF contg] continuous_on_subset [OF conth]]
+        by simp
+      show "?gh ` (?WW1 \<union> ?WW2) \<subseteq> S \<union> T"
+        using \<open>W1 = S' \<inter> O1\<close> \<open>W2 = T' \<inter> O2\<close> \<open>S' \<inter> T' = W\<close> \<open>g ` W1 \<subseteq> S\<close> \<open>h ` W2 \<subseteq> T\<close> \<open>U0 \<inter> W \<subseteq> W0\<close> \<open>W0 \<union> S \<subseteq> W1\<close>  
+        by (auto simp add: image_subset_iff)
+    qed
+    then show "S \<union> T retract_of ?WW1 \<union> ?WW2"
       using  \<open>W0 \<union> S \<subseteq> W1\<close> \<open>W0 \<union> T \<subseteq> W2\<close> ST opeUU0 U0
       by (auto simp: retract_of_def retraction_def)
   qed
 qed
 
 
 lemma ANR_closed_Un_local:
   fixes S :: "'a::euclidean_space set"
   assumes STS: "closedin (top_of_set (S \<union> T)) S"
       and STT: "closedin (top_of_set (S \<union> T)) T"
       and "ANR S" "ANR T" "ANR(S \<inter> T)" 
     shows "ANR(S \<union> T)"
 proof -
   have "\<exists>T. openin (top_of_set U) T \<and> C retract_of T"
        if hom: "S \<union> T homeomorphic C" and UC: "closedin (top_of_set U) C"
        for U and C :: "('a * real) set"
   proof -
     obtain f g where hom: "homeomorphism (S \<union> T) C f g"
       using hom by (force simp: homeomorphic_def)
     have US: "closedin (top_of_set U) (C \<inter> g -` S)"
-      apply (rule closedin_trans [OF _ UC])
-      apply (rule continuous_closedin_preimage_gen [OF _ _ STS])
-      using hom [unfolded homeomorphism_def] apply blast
-      apply (metis hom homeomorphism_def set_eq_subset)
-      done
+      by (metis STS UC closedin_trans continuous_on_imp_closedin hom homeomorphism_def)
     have UT: "closedin (top_of_set U) (C \<inter> g -` T)"
-      apply (rule closedin_trans [OF _ UC])
-      apply (rule continuous_closedin_preimage_gen [OF _ _ STT])
-      using hom [unfolded homeomorphism_def] apply blast
-      apply (metis hom homeomorphism_def set_eq_subset)
-      done
-    have ANRS: "ANR (C \<inter> g -` S)"
-      apply (rule ANR_homeomorphic_ANR [OF \<open>ANR S\<close>])
-      apply (simp add: homeomorphic_def)
-      apply (rule_tac x=g in exI)
-      apply (rule_tac x=f in exI)
+      by (metis STT UC closedin_trans continuous_on_imp_closedin hom homeomorphism_def)
+    have "homeomorphism (C \<inter> g -` S) S g f"
+      using hom 
+      apply (auto simp: homeomorphism_def elim!: continuous_on_subset)
+      by (rule_tac x="f x" in image_eqI, auto)
+    then have ANRS: "ANR (C \<inter> g -` S)"
+      using \<open>ANR S\<close> homeomorphic_ANR_iff_ANR homeomorphic_def by blast
+    have "homeomorphism (C \<inter> g -` T) T g f"
       using hom apply (auto simp: homeomorphism_def elim!: continuous_on_subset)
-      apply (rule_tac x="f x" in image_eqI, auto)
-      done
-    have ANRT: "ANR (C \<inter> g -` T)"
-      apply (rule ANR_homeomorphic_ANR [OF \<open>ANR T\<close>])
-      apply (simp add: homeomorphic_def)
-      apply (rule_tac x=g in exI)
-      apply (rule_tac x=f in exI)
-      using hom apply (auto simp: homeomorphism_def elim!: continuous_on_subset)
-      apply (rule_tac x="f x" in image_eqI, auto)
-      done
-    have ANRI: "ANR ((C \<inter> g -` S) \<inter> (C \<inter> g -` T))"
-      apply (rule ANR_homeomorphic_ANR [OF \<open>ANR (S \<inter> T)\<close>])
-      apply (simp add: homeomorphic_def)
-      apply (rule_tac x=g in exI)
-      apply (rule_tac x=f in exI)
+      by (rule_tac x="f x" in image_eqI, auto)
+    then have ANRT: "ANR (C \<inter> g -` T)"
+      using \<open>ANR T\<close> homeomorphic_ANR_iff_ANR homeomorphic_def by blast
+    have "homeomorphism (C \<inter> g -` S \<inter> (C \<inter> g -` T)) (S \<inter> T) g f"
       using hom
       apply (auto simp: homeomorphism_def elim!: continuous_on_subset)
-      apply (rule_tac x="f x" in image_eqI, auto)
-      done
+      by (rule_tac x="f x" in image_eqI, auto)
+    then have ANRI: "ANR ((C \<inter> g -` S) \<inter> (C \<inter> g -` T))"
+      using \<open>ANR (S \<inter> T)\<close> homeomorphic_ANR_iff_ANR homeomorphic_def by blast
     have "C = (C \<inter> g -` S) \<union> (C \<inter> g -` T)"
       using hom by (auto simp: homeomorphism_def)
     then show ?thesis
       by (metis ANR_closed_Un_local_aux [OF US UT ANRS ANRT ANRI])
   qed
   then show ?thesis
     by (auto simp: ANR_def)
 qed    
 
 corollary ANR_closed_Un:
   fixes S :: "'a::euclidean_space set"
   shows "\<lbrakk>closed S; closed T; ANR S; ANR T; ANR (S \<inter> T)\<rbrakk> \<Longrightarrow> ANR (S \<union> T)"
 by (simp add: ANR_closed_Un_local closedin_def diff_eq open_Compl openin_open_Int)
 
 lemma ANR_openin:
   fixes S :: "'a::euclidean_space set"
   assumes "ANR T" and opeTS: "openin (top_of_set T) S"
   shows "ANR S"
 proof (clarsimp simp only: ANR_eq_absolute_neighbourhood_extensor)
   fix f :: "'a \<times> real \<Rightarrow> 'a" and U C
   assume contf: "continuous_on C f" and fim: "f ` C \<subseteq> S"
      and cloUC: "closedin (top_of_set U) C"
   have "f ` C \<subseteq> T"
     using fim opeTS openin_imp_subset by blast
   obtain W g where "C \<subseteq> W"
                and UW: "openin (top_of_set U) W"
                and contg: "continuous_on W g"
                and gim: "g ` W \<subseteq> T"
                and geq: "\<And>x. x \<in> C \<Longrightarrow> g x = f x"
-    apply (rule ANR_imp_absolute_neighbourhood_extensor [OF \<open>ANR T\<close> contf \<open>f ` C \<subseteq> T\<close> cloUC])
-    using fim by auto
+    using ANR_imp_absolute_neighbourhood_extensor [OF \<open>ANR T\<close> contf \<open>f ` C \<subseteq> T\<close> cloUC] fim by auto
   show "\<exists>V g. C \<subseteq> V \<and> openin (top_of_set U) V \<and> continuous_on V g \<and> g ` V \<subseteq> S \<and> (\<forall>x\<in>C. g x = f x)"
   proof (intro exI conjI)
     show "C \<subseteq> W \<inter> g -` S"
       using \<open>C \<subseteq> W\<close> fim geq by blast
     show "openin (top_of_set U) (W \<inter> g -` S)"
       by (metis (mono_tags, lifting) UW contg continuous_openin_preimage gim opeTS openin_trans)
     show "continuous_on (W \<inter> g -` S) g"
       by (blast intro: continuous_on_subset [OF contg])
     show "g ` (W \<inter> g -` S) \<subseteq> S"
       using gim by blast
     show "\<forall>x\<in>C. g x = f x"
       using geq by blast
   qed
 qed
 
 lemma ENR_openin:
     fixes S :: "'a::euclidean_space set"
-    assumes "ENR T" and opeTS: "openin (top_of_set T) S"
+    assumes "ENR T" "openin (top_of_set T) S"
     shows "ENR S"
-  using assms apply (simp add: ENR_ANR)
-  using ANR_openin locally_open_subset by blast
+  by (meson ANR_openin ENR_ANR assms locally_open_subset)
 
 lemma ANR_neighborhood_retract:
     fixes S :: "'a::euclidean_space set"
     assumes "ANR U" "S retract_of T" "openin (top_of_set U) T"
     shows "ANR S"
   using ANR_openin ANR_retract_of_ANR assms by blast
 
 lemma ENR_neighborhood_retract:
     fixes S :: "'a::euclidean_space set"
     assumes "ENR U" "S retract_of T" "openin (top_of_set U) T"
     shows "ENR S"
   using ENR_openin ENR_retract_of_ENR assms by blast
 
 lemma ANR_rel_interior:
   fixes S :: "'a::euclidean_space set"
   shows "ANR S \<Longrightarrow> ANR(rel_interior S)"
    by (blast intro: ANR_openin openin_set_rel_interior)
 
 lemma ANR_delete:
   fixes S :: "'a::euclidean_space set"
   shows "ANR S \<Longrightarrow> ANR(S - {a})"
    by (blast intro: ANR_openin openin_delete openin_subtopology_self)
 
 lemma ENR_rel_interior:
   fixes S :: "'a::euclidean_space set"
   shows "ENR S \<Longrightarrow> ENR(rel_interior S)"
    by (blast intro: ENR_openin openin_set_rel_interior)
 
 lemma ENR_delete:
   fixes S :: "'a::euclidean_space set"
   shows "ENR S \<Longrightarrow> ENR(S - {a})"
    by (blast intro: ENR_openin openin_delete openin_subtopology_self)
 
 lemma open_imp_ENR: "open S \<Longrightarrow> ENR S"
     using ENR_def by blast
 
 lemma open_imp_ANR:
     fixes S :: "'a::euclidean_space set"
     shows "open S \<Longrightarrow> ANR S"
   by (simp add: ENR_imp_ANR open_imp_ENR)
 
 lemma ANR_ball [iff]:
     fixes a :: "'a::euclidean_space"
     shows "ANR(ball a r)"
   by (simp add: convex_imp_ANR)
 
 lemma ENR_ball [iff]: "ENR(ball a r)"
   by (simp add: open_imp_ENR)
 
 lemma AR_ball [simp]:
     fixes a :: "'a::euclidean_space"
     shows "AR(ball a r) \<longleftrightarrow> 0 < r"
   by (auto simp: AR_ANR convex_imp_contractible)
 
 lemma ANR_cball [iff]:
     fixes a :: "'a::euclidean_space"
     shows "ANR(cball a r)"
   by (simp add: convex_imp_ANR)
 
 lemma ENR_cball:
     fixes a :: "'a::euclidean_space"
     shows "ENR(cball a r)"
   using ENR_convex_closed by blast
 
 lemma AR_cball [simp]:
     fixes a :: "'a::euclidean_space"
     shows "AR(cball a r) \<longleftrightarrow> 0 \<le> r"
   by (auto simp: AR_ANR convex_imp_contractible)
 
 lemma ANR_box [iff]:
     fixes a :: "'a::euclidean_space"
     shows "ANR(cbox a b)" "ANR(box a b)"
   by (auto simp: convex_imp_ANR open_imp_ANR)
 
 lemma ENR_box [iff]:
     fixes a :: "'a::euclidean_space"
     shows "ENR(cbox a b)" "ENR(box a b)"
-apply (simp add: ENR_convex_closed closed_cbox)
-by (simp add: open_box open_imp_ENR)
+  by (simp_all add: ENR_convex_closed closed_cbox open_box open_imp_ENR)
 
 lemma AR_box [simp]:
     "AR(cbox a b) \<longleftrightarrow> cbox a b \<noteq> {}" "AR(box a b) \<longleftrightarrow> box a b \<noteq> {}"
   by (auto simp: AR_ANR convex_imp_contractible)
 
 lemma ANR_interior:
      fixes S :: "'a::euclidean_space set"
      shows "ANR(interior S)"
   by (simp add: open_imp_ANR)
 
 lemma ENR_interior:
      fixes S :: "'a::euclidean_space set"
      shows "ENR(interior S)"
   by (simp add: open_imp_ENR)
 
 lemma AR_imp_contractible:
     fixes S :: "'a::euclidean_space set"
     shows "AR S \<Longrightarrow> contractible S"
   by (simp add: AR_ANR)
 
 lemma ENR_imp_locally_compact:
     fixes S :: "'a::euclidean_space set"
     shows "ENR S \<Longrightarrow> locally compact S"
   by (simp add: ENR_ANR)
 
 lemma ANR_imp_locally_path_connected:
   fixes S :: "'a::euclidean_space set"
   assumes "ANR S"
     shows "locally path_connected S"
 proof -
   obtain U and T :: "('a \<times> real) set"
      where "convex U" "U \<noteq> {}"
-       and UT: "closedin (top_of_set U) T"
-       and "S homeomorphic T"
-    apply (rule homeomorphic_closedin_convex [of S])
-    using aff_dim_le_DIM [of S] apply auto
-    done
+       and UT: "closedin (top_of_set U) T" and "S homeomorphic T"
+  proof (rule homeomorphic_closedin_convex)
+    show "aff_dim S < int DIM('a \<times> real)"
+      using aff_dim_le_DIM [of S] by auto
+  qed auto
   then have "locally path_connected T"
     by (meson ANR_imp_absolute_neighbourhood_retract
         assms convex_imp_locally_path_connected locally_open_subset retract_of_locally_path_connected)
   then have S: "locally path_connected S"
       if "openin (top_of_set U) V" "T retract_of V" "U \<noteq> {}" for V
     using \<open>S homeomorphic T\<close> homeomorphic_locally homeomorphic_path_connectedness by blast
-  show ?thesis
-    using assms
-    apply (clarsimp simp: ANR_def)
-    apply (drule_tac x=U in spec)
-    apply (drule_tac x=T in spec)
-    using \<open>S homeomorphic T\<close> \<open>U \<noteq> {}\<close> UT  apply (blast intro: S)
-    done
+  obtain Ta where "(openin (top_of_set U) Ta \<and> T retract_of Ta)"
+    using ANR_def UT \<open>S homeomorphic T\<close> assms by moura
+  then show ?thesis
+    using S \<open>U \<noteq> {}\<close> by blast
 qed
 
 lemma ANR_imp_locally_connected:
   fixes S :: "'a::euclidean_space set"
   assumes "ANR S"
     shows "locally connected S"
 using locally_path_connected_imp_locally_connected ANR_imp_locally_path_connected assms by auto
 
 lemma AR_imp_locally_path_connected:
   fixes S :: "'a::euclidean_space set"
   assumes "AR S"
     shows "locally path_connected S"
 by (simp add: ANR_imp_locally_path_connected AR_imp_ANR assms)
 
 lemma AR_imp_locally_connected:
   fixes S :: "'a::euclidean_space set"
   assumes "AR S"
     shows "locally connected S"
 using ANR_imp_locally_connected AR_ANR assms by blast
 
 lemma ENR_imp_locally_path_connected:
   fixes S :: "'a::euclidean_space set"
   assumes "ENR S"
     shows "locally path_connected S"
 by (simp add: ANR_imp_locally_path_connected ENR_imp_ANR assms)
 
 lemma ENR_imp_locally_connected:
   fixes S :: "'a::euclidean_space set"
   assumes "ENR S"
     shows "locally connected S"
 using ANR_imp_locally_connected ENR_ANR assms by blast
 
 lemma ANR_Times:
   fixes S :: "'a::euclidean_space set" and T :: "'b::euclidean_space set"
   assumes "ANR S" "ANR T" shows "ANR(S \<times> T)"
 proof (clarsimp simp only: ANR_eq_absolute_neighbourhood_extensor)
   fix f :: " ('a \<times> 'b) \<times> real \<Rightarrow> 'a \<times> 'b" and U C
   assume "continuous_on C f" and fim: "f ` C \<subseteq> S \<times> T"
      and cloUC: "closedin (top_of_set U) C"
   have contf1: "continuous_on C (fst \<circ> f)"
     by (simp add: \<open>continuous_on C f\<close> continuous_on_fst)
   obtain W1 g where "C \<subseteq> W1"
                and UW1: "openin (top_of_set U) W1"
                and contg: "continuous_on W1 g"
                and gim: "g ` W1 \<subseteq> S"
                and geq: "\<And>x. x \<in> C \<Longrightarrow> g x = (fst \<circ> f) x"
-    apply (rule ANR_imp_absolute_neighbourhood_extensor [OF \<open>ANR S\<close> contf1 _ cloUC])
-    using fim apply auto
-    done
+  proof (rule ANR_imp_absolute_neighbourhood_extensor [OF \<open>ANR S\<close> contf1 _ cloUC])
+    show "(fst \<circ> f) ` C \<subseteq> S"
+      using fim by auto
+  qed auto
   have contf2: "continuous_on C (snd \<circ> f)"
     by (simp add: \<open>continuous_on C f\<close> continuous_on_snd)
   obtain W2 h where "C \<subseteq> W2"
                and UW2: "openin (top_of_set U) W2"
                and conth: "continuous_on W2 h"
                and him: "h ` W2 \<subseteq> T"
                and heq: "\<And>x. x \<in> C \<Longrightarrow> h x = (snd \<circ> f) x"
-    apply (rule ANR_imp_absolute_neighbourhood_extensor [OF \<open>ANR T\<close> contf2 _ cloUC])
-    using fim apply auto
-    done
+  proof (rule ANR_imp_absolute_neighbourhood_extensor [OF \<open>ANR T\<close> contf2 _ cloUC])
+    show "(snd \<circ> f) ` C \<subseteq> T"
+      using fim by auto
+  qed auto
   show "\<exists>V g. C \<subseteq> V \<and>
                openin (top_of_set U) V \<and>
                continuous_on V g \<and> g ` V \<subseteq> S \<times> T \<and> (\<forall>x\<in>C. g x = f x)"
   proof (intro exI conjI)
     show "C \<subseteq> W1 \<inter> W2"
       by (simp add: \<open>C \<subseteq> W1\<close> \<open>C \<subseteq> W2\<close>)
     show "openin (top_of_set U) (W1 \<inter> W2)"
       by (simp add: UW1 UW2 openin_Int)
     show  "continuous_on (W1 \<inter> W2) (\<lambda>x. (g x, h x))"
       by (metis (no_types) contg conth continuous_on_Pair continuous_on_subset inf_commute inf_le1)
     show  "(\<lambda>x. (g x, h x)) ` (W1 \<inter> W2) \<subseteq> S \<times> T"
       using gim him by blast
     show  "(\<forall>x\<in>C. (g x, h x) = f x)"
       using geq heq by auto
   qed
 qed
 
 lemma AR_Times:
   fixes S :: "'a::euclidean_space set" and T :: "'b::euclidean_space set"
   assumes "AR S" "AR T" shows "AR(S \<times> T)"
   using assms by (simp add: AR_ANR ANR_Times contractible_Times)
 
-(* Unused
+(* Unused and requires ordered_euclidean_space
 subsection\<^marker>\<open>tag unimportant\<close>\<open>Retracts and intervals in ordered euclidean space\<close>
 
 lemma ANR_interval [iff]:
   fixes a :: "'a::ordered_euclidean_space"
   shows "ANR{a..b}"
   by (simp add: interval_cbox)
 
 lemma ENR_interval [iff]:
   fixes a :: "'a::ordered_euclidean_space"
   shows "ENR{a..b}"
   by (auto simp: interval_cbox)
 *)
 
 subsection \<open>More advanced properties of ANRs and ENRs\<close>
 
 lemma ENR_rel_frontier_convex:
   fixes S :: "'a::euclidean_space set"
   assumes "bounded S" "convex S"
     shows "ENR(rel_frontier S)"
 proof (cases "S = {}")
   case True then show ?thesis
     by simp
 next
   case False
   with assms have "rel_interior S \<noteq> {}"
     by (simp add: rel_interior_eq_empty)
   then obtain a where a: "a \<in> rel_interior S"
     by auto
   have ahS: "affine hull S - {a} \<subseteq> {x. closest_point (affine hull S) x \<noteq> a}"
     by (auto simp: closest_point_self)
   have "rel_frontier S retract_of affine hull S - {a}"
     by (simp add: assms a rel_frontier_retract_of_punctured_affine_hull)
   also have "\<dots> retract_of {x. closest_point (affine hull S) x \<noteq> a}"
-    apply (simp add: retract_of_def retraction_def ahS)
+    unfolding retract_of_def retraction_def ahS
     apply (rule_tac x="closest_point (affine hull S)" in exI)
     apply (auto simp: False closest_point_self affine_imp_convex closest_point_in_set continuous_on_closest_point)
     done
   finally have "rel_frontier S retract_of {x. closest_point (affine hull S) x \<noteq> a}" .
   moreover have "openin (top_of_set UNIV) (UNIV \<inter> closest_point (affine hull S) -` (- {a}))"
-    apply (rule continuous_openin_preimage_gen)
-    apply (auto simp: False affine_imp_convex continuous_on_closest_point)
-    done
+    by (intro continuous_openin_preimage_gen) (auto simp: False affine_imp_convex continuous_on_closest_point)
   ultimately show ?thesis
-    unfolding ENR_def
-    apply (rule_tac x = "closest_point (affine hull S) -` (- {a})" in exI)
-    apply (simp add: vimage_def)
-    done
+    by (meson ENR_convex_closed ENR_delete ENR_retract_of_ENR \<open>rel_frontier S retract_of affine hull S - {a}\<close> 
+              closed_affine_hull convex_affine_hull)
 qed
 
 lemma ANR_rel_frontier_convex:
                  fixes S :: "'a::euclidean_space set"
   assumes "bounded S" "convex S"
     shows "ANR(rel_frontier S)"
 by (simp add: ENR_imp_ANR ENR_rel_frontier_convex assms)
     
 lemma ENR_closedin_Un_local:
   fixes S :: "'a::euclidean_space set"
   shows "\<lbrakk>ENR S; ENR T; ENR(S \<inter> T);
           closedin (top_of_set (S \<union> T)) S; closedin (top_of_set (S \<union> T)) T\<rbrakk>
         \<Longrightarrow> ENR(S \<union> T)"
 by (simp add: ENR_ANR ANR_closed_Un_local locally_compact_closedin_Un)
 
 lemma ENR_closed_Un:
   fixes S :: "'a::euclidean_space set"
   shows "\<lbrakk>closed S; closed T; ENR S; ENR T; ENR(S \<inter> T)\<rbrakk> \<Longrightarrow> ENR(S \<union> T)"
 by (auto simp: closed_subset ENR_closedin_Un_local)
 
 lemma absolute_retract_Un:
   fixes S :: "'a::euclidean_space set"
   shows "\<lbrakk>S retract_of UNIV; T retract_of UNIV; (S \<inter> T) retract_of UNIV\<rbrakk>
          \<Longrightarrow> (S \<union> T) retract_of UNIV"
   by (meson AR_closed_Un_local_aux closed_subset retract_of_UNIV retract_of_imp_subset)
 
 lemma retract_from_Un_Int:
   fixes S :: "'a::euclidean_space set"
   assumes clS: "closedin (top_of_set (S \<union> T)) S"
       and clT: "closedin (top_of_set (S \<union> T)) T"
       and Un: "(S \<union> T) retract_of U" and Int: "(S \<inter> T) retract_of T"
     shows "S retract_of U"
 proof -
   obtain r where r: "continuous_on T r" "r ` T \<subseteq> S \<inter> T" "\<forall>x\<in>S \<inter> T. r x = x"
     using Int by (auto simp: retraction_def retract_of_def)
   have "S retract_of S \<union> T"
     unfolding retraction_def retract_of_def
   proof (intro exI conjI)
     show "continuous_on (S \<union> T) (\<lambda>x. if x \<in> S then x else r x)"
-      apply (rule continuous_on_cases_local [OF clS clT])
-      using r by (auto)
+      using r by (intro continuous_on_cases_local [OF clS clT]) auto
   qed (use r in auto)
   also have "\<dots> retract_of U"
     by (rule Un)
   finally show ?thesis .
 qed
 
 lemma AR_from_Un_Int_local:
   fixes S :: "'a::euclidean_space set"
   assumes clS: "closedin (top_of_set (S \<union> T)) S"
       and clT: "closedin (top_of_set (S \<union> T)) T"
       and Un: "AR(S \<union> T)" and Int: "AR(S \<inter> T)"
     shows "AR S"
-  apply (rule AR_retract_of_AR [OF Un])
-  by (meson AR_imp_retract clS clT closedin_closed_subset local.Int retract_from_Un_Int retract_of_refl sup_ge2)
+  by (meson AR_imp_retract AR_retract_of_AR Un assms closedin_closed_subset local.Int 
+            retract_from_Un_Int retract_of_refl sup_ge2)
 
 lemma AR_from_Un_Int_local':
   fixes S :: "'a::euclidean_space set"
   assumes "closedin (top_of_set (S \<union> T)) S"
       and "closedin (top_of_set (S \<union> T)) T"
       and "AR(S \<union> T)" "AR(S \<inter> T)"
     shows "AR T"
   using AR_from_Un_Int_local [of T S] assms by (simp add: Un_commute Int_commute)
 
 lemma AR_from_Un_Int:
   fixes S :: "'a::euclidean_space set"
   assumes clo: "closed S" "closed T" and Un: "AR(S \<union> T)" and Int: "AR(S \<inter> T)"
   shows "AR S"
   by (metis AR_from_Un_Int_local [OF _ _ Un Int] Un_commute clo closed_closedin closedin_closed_subset inf_sup_absorb subtopology_UNIV top_greatest)
 
 lemma ANR_from_Un_Int_local:
   fixes S :: "'a::euclidean_space set"
   assumes clS: "closedin (top_of_set (S \<union> T)) S"
       and clT: "closedin (top_of_set (S \<union> T)) T"
       and Un: "ANR(S \<union> T)" and Int: "ANR(S \<inter> T)"
     shows "ANR S"
 proof -
   obtain V where clo: "closedin (top_of_set (S \<union> T)) (S \<inter> T)"
              and ope: "openin (top_of_set (S \<union> T)) V"
              and ret: "S \<inter> T retract_of V"
     using ANR_imp_neighbourhood_retract [OF Int] by (metis clS clT closedin_Int)
   then obtain r where r: "continuous_on V r" and rim: "r ` V \<subseteq> S \<inter> T" and req: "\<forall>x\<in>S \<inter> T. r x = x"
     by (auto simp: retraction_def retract_of_def)
   have Vsub: "V \<subseteq> S \<union> T"
     by (meson ope openin_contains_cball)
   have Vsup: "S \<inter> T \<subseteq> V"
     by (simp add: retract_of_imp_subset ret)
   then have eq: "S \<union> V = ((S \<union> T) - T) \<union> V"
     by auto
   have eq': "S \<union> V = S \<union> (V \<inter> T)"
     using Vsub by blast
   have "continuous_on (S \<union> V \<inter> T) (\<lambda>x. if x \<in> S then x else r x)"
   proof (rule continuous_on_cases_local)
     show "closedin (top_of_set (S \<union> V \<inter> T)) S"
       using clS closedin_subset_trans inf.boundedE by blast
     show "closedin (top_of_set (S \<union> V \<inter> T)) (V \<inter> T)"
       using clT Vsup by (auto simp: closedin_closed)
     show "continuous_on (V \<inter> T) r"
       by (meson Int_lower1 continuous_on_subset r)
   qed (use req continuous_on_id in auto)
   with rim have "S retract_of S \<union> V"
-    unfolding retraction_def retract_of_def
-    apply (rule_tac x="\<lambda>x. if x \<in> S then x else r x" in exI)
-    apply (auto simp: eq')
-    done
+    unfolding retraction_def retract_of_def using eq' by fastforce
   then show ?thesis
     using ANR_neighborhood_retract [OF Un]
     using \<open>S \<union> V = S \<union> T - T \<union> V\<close> clT ope by fastforce
 qed
 
 lemma ANR_from_Un_Int:
   fixes S :: "'a::euclidean_space set"
   assumes clo: "closed S" "closed T" and Un: "ANR(S \<union> T)" and Int: "ANR(S \<inter> T)"
   shows "ANR S"
   by (metis ANR_from_Un_Int_local [OF _ _ Un Int] Un_commute clo closed_closedin closedin_closed_subset inf_sup_absorb subtopology_UNIV top_greatest)
 
 lemma ANR_finite_Union_convex_closed:
   fixes \<T> :: "'a::euclidean_space set set"
   assumes \<T>: "finite \<T>" and clo: "\<And>C. C \<in> \<T> \<Longrightarrow> closed C" and con: "\<And>C. C \<in> \<T> \<Longrightarrow> convex C"
   shows "ANR(\<Union>\<T>)"
 proof -
   have "ANR(\<Union>\<T>)" if "card \<T> < n" for n
   using assms that
   proof (induction n arbitrary: \<T>)
     case 0 then show ?case by simp
   next
     case (Suc n)
     have "ANR(\<Union>\<U>)" if "finite \<U>" "\<U> \<subseteq> \<T>" for \<U>
       using that
     proof (induction \<U>)
       case empty
       then show ?case  by simp
     next
       case (insert C \<U>)
       have "ANR (C \<union> \<Union>\<U>)"
       proof (rule ANR_closed_Un)
         show "ANR (C \<inter> \<Union>\<U>)"
           unfolding Int_Union
         proof (rule Suc)
           show "finite ((\<inter>) C ` \<U>)"
             by (simp add: insert.hyps(1))
           show "\<And>Ca. Ca \<in> (\<inter>) C ` \<U> \<Longrightarrow> closed Ca"
             by (metis (no_types, hide_lams) Suc.prems(2) closed_Int subsetD imageE insert.prems insertI1 insertI2)
           show "\<And>Ca. Ca \<in> (\<inter>) C ` \<U> \<Longrightarrow> convex Ca"
             by (metis (mono_tags, lifting) Suc.prems(3) convex_Int imageE insert.prems insert_subset subsetCE)
           show "card ((\<inter>) C ` \<U>) < n"
           proof -
             have "card \<T> \<le> n"
               by (meson Suc.prems(4) not_less not_less_eq)
             then show ?thesis
               by (metis Suc.prems(1) card_image_le card_seteq insert.hyps insert.prems insert_subset le_trans not_less)
           qed
         qed
         show "closed (\<Union>\<U>)"
           using Suc.prems(2) insert.hyps(1) insert.prems by blast
       qed (use Suc.prems convex_imp_ANR insert.prems insert.IH in auto)
       then show ?case
         by simp
     qed
     then show ?case
       using Suc.prems(1) by blast
   qed
   then show ?thesis
     by blast
 qed
 
 
 lemma finite_imp_ANR:
   fixes S :: "'a::euclidean_space set"
   assumes "finite S"
   shows "ANR S"
 proof -
   have "ANR(\<Union>x \<in> S. {x})"
     by (blast intro: ANR_finite_Union_convex_closed assms)
   then show ?thesis
     by simp
 qed
 
 lemma ANR_insert:
   fixes S :: "'a::euclidean_space set"
   assumes "ANR S" "closed S"
   shows "ANR(insert a S)"
   by (metis ANR_closed_Un ANR_empty ANR_singleton Diff_disjoint Diff_insert_absorb assms closed_singleton insert_absorb insert_is_Un)
 
 lemma ANR_path_component_ANR:
   fixes S :: "'a::euclidean_space set"
   shows "ANR S \<Longrightarrow> ANR(path_component_set S x)"
   using ANR_imp_locally_path_connected ANR_openin openin_path_component_locally_path_connected by blast
 
 lemma ANR_connected_component_ANR:
   fixes S :: "'a::euclidean_space set"
   shows "ANR S \<Longrightarrow> ANR(connected_component_set S x)"
   by (metis ANR_openin openin_connected_component_locally_connected ANR_imp_locally_connected)
 
 lemma ANR_component_ANR:
   fixes S :: "'a::euclidean_space set"
   assumes "ANR S" "c \<in> components S"
   shows "ANR c"
   by (metis ANR_connected_component_ANR assms componentsE)
 
 subsection\<open>Original ANR material, now for ENRs\<close>
 
 lemma ENR_bounded:
   fixes S :: "'a::euclidean_space set"
   assumes "bounded S"
   shows "ENR S \<longleftrightarrow> (\<exists>U. open U \<and> bounded U \<and> S retract_of U)"
          (is "?lhs = ?rhs")
 proof
   obtain r where "0 < r" and r: "S \<subseteq> ball 0 r"
     using bounded_subset_ballD assms by blast
   assume ?lhs
   then show ?rhs
-    apply (clarsimp simp: ENR_def)
-    apply (rule_tac x="ball 0 r \<inter> U" in exI, auto)
-    using r retract_of_imp_subset retract_of_subset by fastforce
+    by (meson ENR_def Elementary_Metric_Spaces.open_ball bounded_Int bounded_ball inf_le2 le_inf_iff 
+              open_Int r retract_of_imp_subset retract_of_subset)
 next
   assume ?rhs
   then show ?lhs
     using ENR_def by blast
 qed
 
 lemma absolute_retract_imp_AR_gen:
   fixes S :: "'a::euclidean_space set" and S' :: "'b::euclidean_space set"
   assumes "S retract_of T" "convex T" "T \<noteq> {}" "S homeomorphic S'" "closedin (top_of_set U) S'"
   shows "S' retract_of U"
 proof -
   have "AR T"
     by (simp add: assms convex_imp_AR)
   then have "AR S"
     using AR_retract_of_AR assms by auto
   then show ?thesis
     using assms AR_imp_absolute_retract by metis
 qed
 
 lemma absolute_retract_imp_AR:
   fixes S :: "'a::euclidean_space set" and S' :: "'b::euclidean_space set"
   assumes "S retract_of UNIV" "S homeomorphic S'" "closed S'"
   shows "S' retract_of UNIV"
   using AR_imp_absolute_retract_UNIV assms retract_of_UNIV by blast
 
 lemma homeomorphic_compact_arness:
   fixes S :: "'a::euclidean_space set" and S' :: "'b::euclidean_space set"
   assumes "S homeomorphic S'"
   shows "compact S \<and> S retract_of UNIV \<longleftrightarrow> compact S' \<and> S' retract_of UNIV"
   using assms homeomorphic_compactness
-  apply auto
-   apply (meson assms compact_AR homeomorphic_AR_iff_AR homeomorphic_compactness)+
-  done
+  by (metis compact_AR homeomorphic_AR_iff_AR)
 
 lemma absolute_retract_from_Un_Int:
   fixes S :: "'a::euclidean_space set"
   assumes "(S \<union> T) retract_of UNIV" "(S \<inter> T) retract_of UNIV" "closed S" "closed T"
   shows "S retract_of UNIV"
   using AR_from_Un_Int assms retract_of_UNIV by auto
 
 lemma ENR_from_Un_Int_gen:
   fixes S :: "'a::euclidean_space set"
   assumes "closedin (top_of_set (S \<union> T)) S" "closedin (top_of_set (S \<union> T)) T" "ENR(S \<union> T)" "ENR(S \<inter> T)"
   shows "ENR S"
-  apply (simp add: ENR_ANR)
-  using ANR_from_Un_Int_local ENR_ANR assms locally_compact_closedin by blast
+  by (meson ANR_from_Un_Int_local ANR_imp_neighbourhood_retract ENR_ANR ENR_neighborhood_retract assms)
 
 
 lemma ENR_from_Un_Int:
   fixes S :: "'a::euclidean_space set"
   assumes "closed S" "closed T" "ENR(S \<union> T)" "ENR(S \<inter> T)"
   shows "ENR S"
   by (meson ENR_from_Un_Int_gen assms closed_subset sup_ge1 sup_ge2)
 
 
 lemma ENR_finite_Union_convex_closed:
   fixes \<T> :: "'a::euclidean_space set set"
   assumes \<T>: "finite \<T>" and clo: "\<And>C. C \<in> \<T> \<Longrightarrow> closed C" and con: "\<And>C. C \<in> \<T> \<Longrightarrow> convex C"
   shows "ENR(\<Union> \<T>)"
   by (simp add: ENR_ANR ANR_finite_Union_convex_closed \<T> clo closed_Union closed_imp_locally_compact con)
 
 lemma finite_imp_ENR:
   fixes S :: "'a::euclidean_space set"
   shows "finite S \<Longrightarrow> ENR S"
   by (simp add: ENR_ANR finite_imp_ANR finite_imp_closed closed_imp_locally_compact)
 
 lemma ENR_insert:
   fixes S :: "'a::euclidean_space set"
   assumes "closed S" "ENR S"
   shows "ENR(insert a S)"
 proof -
   have "ENR ({a} \<union> S)"
     by (metis ANR_insert ENR_ANR Un_commute Un_insert_right assms closed_imp_locally_compact closed_insert sup_bot_right)
   then show ?thesis
     by auto
 qed
 
 lemma ENR_path_component_ENR:
   fixes S :: "'a::euclidean_space set"
   assumes "ENR S"
   shows "ENR(path_component_set S x)"
   by (metis ANR_imp_locally_path_connected ENR_empty ENR_imp_ANR ENR_openin assms
             locally_path_connected_2 openin_subtopology_self path_component_eq_empty)
 
 (*UNUSED
 lemma ENR_Times:
   fixes S :: "'a::euclidean_space set" and T :: "'b::euclidean_space set"
   assumes "ENR S" "ENR T" shows "ENR(S \<times> T)"
 using assms apply (simp add: ENR_ANR ANR_Times)
 thm locally_compact_Times
 oops
   SIMP_TAC[ENR_ANR; ANR_PCROSS; LOCALLY_COMPACT_PCROSS]);;
 *)
 
 subsection\<open>Finally, spheres are ANRs and ENRs\<close>
 
 lemma absolute_retract_homeomorphic_convex_compact:
   fixes S :: "'a::euclidean_space set" and U :: "'b::euclidean_space set"
   assumes "S homeomorphic U" "S \<noteq> {}" "S \<subseteq> T" "convex U" "compact U"
   shows "S retract_of T"
   by (metis UNIV_I assms compact_AR convex_imp_AR homeomorphic_AR_iff_AR homeomorphic_compactness homeomorphic_empty(1) retract_of_subset subsetI)
 
 lemma frontier_retract_of_punctured_universe:
   fixes S :: "'a::euclidean_space set"
   assumes "convex S" "bounded S" "a \<in> interior S"
   shows "(frontier S) retract_of (- {a})"
   using rel_frontier_retract_of_punctured_affine_hull
   by (metis Compl_eq_Diff_UNIV affine_hull_nonempty_interior assms empty_iff rel_frontier_frontier rel_interior_nonempty_interior)
 
 lemma sphere_retract_of_punctured_universe_gen:
   fixes a :: "'a::euclidean_space"
   assumes "b \<in> ball a r"
   shows  "sphere a r retract_of (- {b})"
 proof -
   have "frontier (cball a r) retract_of (- {b})"
-    apply (rule frontier_retract_of_punctured_universe)
-    using assms by auto
+    using assms frontier_retract_of_punctured_universe interior_cball by blast
   then show ?thesis
     by simp
 qed
 
 lemma sphere_retract_of_punctured_universe:
   fixes a :: "'a::euclidean_space"
   assumes "0 < r"
   shows "sphere a r retract_of (- {a})"
   by (simp add: assms sphere_retract_of_punctured_universe_gen)
 
 lemma ENR_sphere:
   fixes a :: "'a::euclidean_space"
   shows "ENR(sphere a r)"
 proof (cases "0 < r")
   case True
   then have "sphere a r retract_of -{a}"
     by (simp add: sphere_retract_of_punctured_universe)
   with open_delete show ?thesis
     by (auto simp: ENR_def)
 next
   case False
   then show ?thesis
     using finite_imp_ENR
     by (metis finite_insert infinite_imp_nonempty less_linear sphere_eq_empty sphere_trivial)
 qed
 
 corollary\<^marker>\<open>tag unimportant\<close> ANR_sphere:
   fixes a :: "'a::euclidean_space"
   shows "ANR(sphere a r)"
   by (simp add: ENR_imp_ANR ENR_sphere)
 
 subsection\<open>Spheres are connected, etc\<close>
 
 lemma locally_path_connected_sphere_gen:
   fixes S :: "'a::euclidean_space set"
   assumes "bounded S" and "convex S" 
   shows "locally path_connected (rel_frontier S)"
 proof (cases "rel_interior S = {}")
   case True
   with assms show ?thesis
     by (simp add: rel_interior_eq_empty)
 next
   case False
   then obtain a where a: "a \<in> rel_interior S"
     by blast
   show ?thesis
   proof (rule retract_of_locally_path_connected)
     show "locally path_connected (affine hull S - {a})"
       by (meson convex_affine_hull convex_imp_locally_path_connected locally_open_subset openin_delete openin_subtopology_self)
     show "rel_frontier S retract_of affine hull S - {a}"
       using a assms rel_frontier_retract_of_punctured_affine_hull by blast
   qed
 qed
 
 lemma locally_connected_sphere_gen:
   fixes S :: "'a::euclidean_space set"
   assumes "bounded S" and "convex S" 
   shows "locally connected (rel_frontier S)"
   by (simp add: ANR_imp_locally_connected ANR_rel_frontier_convex assms)
 
 lemma locally_path_connected_sphere:
   fixes a :: "'a::euclidean_space"
   shows "locally path_connected (sphere a r)"
   using ENR_imp_locally_path_connected ENR_sphere by blast
 
 lemma locally_connected_sphere:
   fixes a :: "'a::euclidean_space"
   shows "locally connected(sphere a r)"
   using ANR_imp_locally_connected ANR_sphere by blast
 
 subsection\<open>Borsuk homotopy extension theorem\<close>
 
 text\<open>It's only this late so we can use the concept of retraction,
   saying that the domain sets or range set are ENRs.\<close>
 
 theorem Borsuk_homotopy_extension_homotopic:
   fixes f :: "'a::euclidean_space \<Rightarrow> 'b::euclidean_space"
   assumes cloTS: "closedin (top_of_set T) S"
       and anr: "(ANR S \<and> ANR T) \<or> ANR U"
       and contf: "continuous_on T f"
       and "f ` T \<subseteq> U"
       and "homotopic_with_canon (\<lambda>x. True) S U f g"
    obtains g' where "homotopic_with_canon (\<lambda>x. True) T U f g'"
                     "continuous_on T g'" "image g' T \<subseteq> U"
                     "\<And>x. x \<in> S \<Longrightarrow> g' x = g x"
 proof -
   have "S \<subseteq> T" using assms closedin_imp_subset by blast
   obtain h where conth: "continuous_on ({0..1} \<times> S) h"
              and him: "h ` ({0..1} \<times> S) \<subseteq> U"
              and [simp]: "\<And>x. h(0, x) = f x" "\<And>x. h(1::real, x) = g x"
        using assms by (auto simp: homotopic_with_def)
   define h' where "h' \<equiv>  \<lambda>z. if snd z \<in> S then h z else (f \<circ> snd) z"
   define B where "B \<equiv> {0::real} \<times> T \<union> {0..1} \<times> S"
   have clo0T: "closedin (top_of_set ({0..1} \<times> T)) ({0::real} \<times> T)"
     by (simp add: Abstract_Topology.closedin_Times)
   moreover have cloT1S: "closedin (top_of_set ({0..1} \<times> T)) ({0..1} \<times> S)"
     by (simp add: Abstract_Topology.closedin_Times assms)
   ultimately have clo0TB:"closedin (top_of_set ({0..1} \<times> T)) B"
     by (auto simp: B_def)
   have cloBS: "closedin (top_of_set B) ({0..1} \<times> S)"
     by (metis (no_types) Un_subset_iff B_def closedin_subset_trans [OF cloT1S] clo0TB closedin_imp_subset closedin_self)
   moreover have cloBT: "closedin (top_of_set B) ({0} \<times> T)"
     using \<open>S \<subseteq> T\<close> closedin_subset_trans [OF clo0T]
     by (metis B_def Un_upper1 clo0TB closedin_closed inf_le1)
   moreover have "continuous_on ({0} \<times> T) (f \<circ> snd)"
-    apply (rule continuous_intros)+
-    apply (simp add: contf)
-    done
-  ultimately have conth': "continuous_on B h'"
-    apply (simp add: h'_def B_def Un_commute [of "{0} \<times> T"])
-    apply (auto intro!: continuous_on_cases_local conth)
-    done
+  proof (rule continuous_intros)+
+    show "continuous_on (snd ` ({0} \<times> T)) f"
+      by (simp add: contf)
+  qed
+  ultimately have "continuous_on ({0..1} \<times> S \<union> {0} \<times> T) (\<lambda>x. if snd x \<in> S then h x else (f \<circ> snd) x)"
+    by (auto intro!: continuous_on_cases_local conth simp: B_def Un_commute [of "{0} \<times> T"])
+  then have conth': "continuous_on B h'"
+    by (simp add: h'_def B_def Un_commute [of "{0} \<times> T"])
   have "image h' B \<subseteq> U"
     using \<open>f ` T \<subseteq> U\<close> him by (auto simp: h'_def B_def)
   obtain V k where "B \<subseteq> V" and opeTV: "openin (top_of_set ({0..1} \<times> T)) V"
                and contk: "continuous_on V k" and kim: "k ` V \<subseteq> U"
                and keq: "\<And>x. x \<in> B \<Longrightarrow> k x = h' x"
   using anr
   proof
     assume ST: "ANR S \<and> ANR T"
     have eq: "({0} \<times> T \<inter> {0..1} \<times> S) = {0::real} \<times> S"
       using \<open>S \<subseteq> T\<close> by auto
     have "ANR B"
-      apply (simp add: B_def)
-      apply (rule ANR_closed_Un_local)
-          apply (metis cloBT B_def)
-         apply (metis Un_commute cloBS B_def)
-        apply (simp_all add: ANR_Times convex_imp_ANR ANR_singleton ST eq)
-      done
+      unfolding B_def
+    proof (rule ANR_closed_Un_local)
+      show "closedin (top_of_set ({0} \<times> T \<union> {0..1} \<times> S)) ({0::real} \<times> T)"
+        by (metis cloBT B_def)
+      show "closedin (top_of_set ({0} \<times> T \<union> {0..1} \<times> S)) ({0..1::real} \<times> S)"
+        by (metis Un_commute cloBS B_def)
+    qed (simp_all add: ANR_Times convex_imp_ANR ANR_singleton ST eq)
     note Vk = that
     have *: thesis if "openin (top_of_set ({0..1::real} \<times> T)) V"
                       "retraction V B r" for V r
-      using that
-      apply (clarsimp simp add: retraction_def)
-      apply (rule Vk [of V "h' \<circ> r"], assumption+)
-        apply (metis continuous_on_compose conth' continuous_on_subset) 
-      using \<open>h' ` B \<subseteq> U\<close> apply force+
-      done
+    proof -
+      have "continuous_on V (h' \<circ> r)"
+        using conth' continuous_on_compose retractionE that(2) by blast
+      moreover have "(h' \<circ> r) ` V \<subseteq> U"
+        by (metis \<open>h' ` B \<subseteq> U\<close> image_comp retractionE that(2))
+      ultimately show ?thesis
+        using Vk [of V "h' \<circ> r"] by (metis comp_apply retraction that)
+    qed
     show thesis
-        apply (rule ANR_imp_neighbourhood_retract [OF \<open>ANR B\<close> clo0TB])
-        apply (auto simp: ANR_Times ANR_singleton ST retract_of_def *)
-        done
+      by (meson "*" ANR_imp_neighbourhood_retract \<open>ANR B\<close> clo0TB retract_of_def)
   next
     assume "ANR U"
     with ANR_imp_absolute_neighbourhood_extensor \<open>h' ` B \<subseteq> U\<close> clo0TB conth' that
     show ?thesis by blast
   qed
   define S' where "S' \<equiv> {x. \<exists>u::real. u \<in> {0..1} \<and> (u, x::'a) \<in> {0..1} \<times> T - V}"
   have "closedin (top_of_set T) S'"
-    unfolding S'_def
-    apply (rule closedin_compact_projection, blast)
-    using closedin_self opeTV by blast
+    unfolding S'_def using closedin_self opeTV 
+    by (blast intro: closedin_compact_projection)
   have S'_def: "S' = {x. \<exists>u::real.  (u, x::'a) \<in> {0..1} \<times> T - V}"
     by (auto simp: S'_def)
   have cloTS': "closedin (top_of_set T) S'"
     using S'_def \<open>closedin (top_of_set T) S'\<close> by blast
   have "S \<inter> S' = {}"
     using S'_def B_def \<open>B \<subseteq> V\<close> by force
   obtain a :: "'a \<Rightarrow> real" where conta: "continuous_on T a"
       and "\<And>x. x \<in> T \<Longrightarrow> a x \<in> closed_segment 1 0"
       and a1: "\<And>x. x \<in> S \<Longrightarrow> a x = 1"
       and a0: "\<And>x. x \<in> S' \<Longrightarrow> a x = 0"
-    apply (rule Urysohn_local [OF cloTS cloTS' \<open>S \<inter> S' = {}\<close>, of 1 0], blast)
-    done
+    by (rule Urysohn_local [OF cloTS cloTS' \<open>S \<inter> S' = {}\<close>, of 1 0], blast)
   then have ain: "\<And>x. x \<in> T \<Longrightarrow> a x \<in> {0..1}"
     using closed_segment_eq_real_ivl by auto
   have inV: "(u * a t, t) \<in> V" if "t \<in> T" "0 \<le> u" "u \<le> 1" for t u
   proof (rule ccontr)
     assume "(u * a t, t) \<notin> V"
     with ain [OF \<open>t \<in> T\<close>] have "a t = 0"
       apply simp
-      apply (rule a0)
-      by (metis (no_types, lifting) Diff_iff S'_def SigmaI atLeastAtMost_iff mem_Collect_eq mult_le_one mult_nonneg_nonneg that)
+      by (metis (no_types, lifting) a0 DiffI S'_def SigmaI atLeastAtMost_iff mem_Collect_eq mult_le_one mult_nonneg_nonneg that)
     show False
       using B_def \<open>(u * a t, t) \<notin> V\<close> \<open>B \<subseteq> V\<close> \<open>a t = 0\<close> that by auto
   qed
   show ?thesis
   proof
     show hom: "homotopic_with_canon (\<lambda>x. True) T U f (\<lambda>x. k (a x, x))"
     proof (simp add: homotopic_with, intro exI conjI)
       show "continuous_on ({0..1} \<times> T) (k \<circ> (\<lambda>z. (fst z *\<^sub>R (a \<circ> snd) z, snd z)))"
         apply (intro continuous_on_compose continuous_intros)
-        apply (rule continuous_on_subset [OF conta], force)
-        apply (rule continuous_on_subset [OF contk])
-        apply (force intro: inV)
+        apply (force intro: inV continuous_on_subset [OF contk] continuous_on_subset [OF conta])+
         done
       show "(k \<circ> (\<lambda>z. (fst z *\<^sub>R (a \<circ> snd) z, snd z))) ` ({0..1} \<times> T) \<subseteq> U"
         using inV kim by auto
       show "\<forall>x\<in>T. (k \<circ> (\<lambda>z. (fst z *\<^sub>R (a \<circ> snd) z, snd z))) (0, x) = f x"
         by (simp add: B_def h'_def keq)
       show "\<forall>x\<in>T. (k \<circ> (\<lambda>z. (fst z *\<^sub>R (a \<circ> snd) z, snd z))) (1, x) = k (a x, x)"
         by auto
     qed
   show "continuous_on T (\<lambda>x. k (a x, x))"
     using homotopic_with_imp_continuous_maps [OF hom] by auto
   show "(\<lambda>x. k (a x, x)) ` T \<subseteq> U"
   proof clarify
     fix t
     assume "t \<in> T"
     show "k (a t, t) \<in> U"
       by (metis \<open>t \<in> T\<close> image_subset_iff inV kim not_one_le_zero linear mult_cancel_right1)
   qed
   show "\<And>x. x \<in> S \<Longrightarrow> k (a x, x) = g x"
     by (simp add: B_def a1 h'_def keq)
   qed
 qed
 
 
 corollary\<^marker>\<open>tag unimportant\<close> nullhomotopic_into_ANR_extension:
   fixes f :: "'a::euclidean_space \<Rightarrow> 'b::euclidean_space"
   assumes "closed S"
       and contf: "continuous_on S f"
       and "ANR T"
       and fim: "f ` S \<subseteq> T"
       and "S \<noteq> {}"
    shows "(\<exists>c. homotopic_with_canon (\<lambda>x. True) S T f (\<lambda>x. c)) \<longleftrightarrow>
           (\<exists>g. continuous_on UNIV g \<and> range g \<subseteq> T \<and> (\<forall>x \<in> S. g x = f x))"
        (is "?lhs = ?rhs")
 proof
   assume ?lhs
   then obtain c where c: "homotopic_with_canon (\<lambda>x. True) S T (\<lambda>x. c) f"
     by (blast intro: homotopic_with_symD)
   have "closedin (top_of_set UNIV) S"
     using \<open>closed S\<close> closed_closedin by fastforce
   then obtain g where "continuous_on UNIV g" "range g \<subseteq> T"
                       "\<And>x. x \<in> S \<Longrightarrow> g x = f x"
-    apply (rule Borsuk_homotopy_extension_homotopic [OF _ _ continuous_on_const _ c, where T=UNIV])
-    using \<open>ANR T\<close> \<open>S \<noteq> {}\<close> c homotopic_with_imp_subset1 apply fastforce+
-    done
+  proof (rule Borsuk_homotopy_extension_homotopic)
+    show "range (\<lambda>x. c) \<subseteq> T"
+      using \<open>S \<noteq> {}\<close> c homotopic_with_imp_subset1 by fastforce
+  qed (use assms c in auto)
   then show ?rhs by blast
 next
   assume ?rhs
   then obtain g where "continuous_on UNIV g" "range g \<subseteq> T" "\<And>x. x\<in>S \<Longrightarrow> g x = f x"
     by blast
   then obtain c where "homotopic_with_canon (\<lambda>h. True) UNIV T g (\<lambda>x. c)"
     using nullhomotopic_from_contractible [of UNIV g T] contractible_UNIV by blast
   then have "homotopic_with_canon (\<lambda>x. True) S T g (\<lambda>x. c)"
     by (simp add: homotopic_from_subtopology)
   then show ?lhs
     by (force elim: homotopic_with_eq [of _ _ _ g "\<lambda>x. c"] simp: \<open>\<And>x. x \<in> S \<Longrightarrow> g x = f x\<close>)
 qed
 
 corollary\<^marker>\<open>tag unimportant\<close> nullhomotopic_into_rel_frontier_extension:
   fixes f :: "'a::euclidean_space \<Rightarrow> 'b::euclidean_space"
   assumes "closed S"
       and contf: "continuous_on S f"
       and "convex T" "bounded T"
       and fim: "f ` S \<subseteq> rel_frontier T"
       and "S \<noteq> {}"
    shows "(\<exists>c. homotopic_with_canon (\<lambda>x. True) S (rel_frontier T) f (\<lambda>x. c)) \<longleftrightarrow>
           (\<exists>g. continuous_on UNIV g \<and> range g \<subseteq> rel_frontier T \<and> (\<forall>x \<in> S. g x = f x))"
 by (simp add: nullhomotopic_into_ANR_extension assms ANR_rel_frontier_convex)
 
 corollary\<^marker>\<open>tag unimportant\<close> nullhomotopic_into_sphere_extension:
   fixes f :: "'a::euclidean_space \<Rightarrow> 'b :: euclidean_space"
   assumes "closed S" and contf: "continuous_on S f"
       and "S \<noteq> {}" and fim: "f ` S \<subseteq> sphere a r"
     shows "((\<exists>c. homotopic_with_canon (\<lambda>x. True) S (sphere a r) f (\<lambda>x. c)) \<longleftrightarrow>
            (\<exists>g. continuous_on UNIV g \<and> range g \<subseteq> sphere a r \<and> (\<forall>x \<in> S. g x = f x)))"
            (is "?lhs = ?rhs")
 proof (cases "r = 0")
   case True with fim show ?thesis
-    apply auto
-    using fim continuous_on_const apply fastforce
-    by (metis contf contractible_sing nullhomotopic_into_contractible)
+    by (metis ANR_sphere \<open>closed S\<close> \<open>S \<noteq> {}\<close> contf nullhomotopic_into_ANR_extension)
 next
   case False
   then have eq: "sphere a r = rel_frontier (cball a r)" by simp
   show ?thesis
-    using fim unfolding eq
-    apply (rule nullhomotopic_into_rel_frontier_extension [OF \<open>closed S\<close> contf convex_cball bounded_cball])
-    apply (rule \<open>S \<noteq> {}\<close>)
-    done
+    using fim nullhomotopic_into_rel_frontier_extension [OF \<open>closed S\<close> contf convex_cball bounded_cball]
+    by (simp add: \<open>S \<noteq> {}\<close> eq)
 qed
 
 proposition\<^marker>\<open>tag unimportant\<close> Borsuk_map_essential_bounded_component:
   fixes a :: "'a :: euclidean_space"
   assumes "compact S" and "a \<notin> S"
    shows "bounded (connected_component_set (- S) a) \<longleftrightarrow>
           \<not>(\<exists>c. homotopic_with_canon (\<lambda>x. True) S (sphere 0 1)
                                (\<lambda>x. inverse(norm(x - a)) *\<^sub>R (x - a)) (\<lambda>x. c))"
    (is "?lhs = ?rhs")
 proof (cases "S = {}")
   case True then show ?thesis
     by simp
 next
   case False
   have "closed S" "bounded S"
     using \<open>compact S\<close> compact_eq_bounded_closed by auto
   have s01: "(\<lambda>x. (x - a) /\<^sub>R norm (x - a)) ` S \<subseteq> sphere 0 1"
     using \<open>a \<notin> S\<close>  by clarsimp (metis dist_eq_0_iff dist_norm mult.commute right_inverse)
   have aincc: "a \<in> connected_component_set (- S) a"
     by (simp add: \<open>a \<notin> S\<close>)
   obtain r where "r>0" and r: "S \<subseteq> ball 0 r"
     using bounded_subset_ballD \<open>bounded S\<close> by blast
   have "\<not> ?rhs \<longleftrightarrow> \<not> ?lhs"
   proof
     assume notr: "\<not> ?rhs"
     have nog: "\<nexists>g. continuous_on (S \<union> connected_component_set (- S) a) g \<and>
                    g ` (S \<union> connected_component_set (- S) a) \<subseteq> sphere 0 1 \<and>
                    (\<forall>x\<in>S. g x = (x - a) /\<^sub>R norm (x - a))"
-         if "bounded (connected_component_set (- S) a)"
-      apply (rule non_extensible_Borsuk_map [OF \<open>compact S\<close> componentsI _ aincc])
-      using  \<open>a \<notin> S\<close> that by auto
+      if "bounded (connected_component_set (- S) a)"
+      using non_extensible_Borsuk_map [OF \<open>compact S\<close> componentsI _ aincc] \<open>a \<notin> S\<close> that by auto
     obtain g where "range g \<subseteq> sphere 0 1" "continuous_on UNIV g"
                         "\<And>x. x \<in> S \<Longrightarrow> g x = (x - a) /\<^sub>R norm (x - a)"
       using notr
       by (auto simp: nullhomotopic_into_sphere_extension
                  [OF \<open>closed S\<close> continuous_on_Borsuk_map [OF \<open>a \<notin> S\<close>] False s01])
     with \<open>a \<notin> S\<close> show  "\<not> ?lhs"
-      apply (clarsimp simp: Borsuk_map_into_sphere [of a S, symmetric] dest!: nog)
-      apply (drule_tac x=g in spec)
-      using continuous_on_subset by fastforce 
+      by (metis UNIV_I continuous_on_subset image_subset_iff nog subsetI)
   next
     assume "\<not> ?lhs"
     then obtain b where b: "b \<in> connected_component_set (- S) a" and "r \<le> norm b"
       using bounded_iff linear by blast
     then have bnot: "b \<notin> ball 0 r"
       by simp
     have "homotopic_with_canon (\<lambda>x. True) S (sphere 0 1) (\<lambda>x. (x - a) /\<^sub>R norm (x - a))
-                                                   (\<lambda>x. (x - b) /\<^sub>R norm (x - b))"
-      apply (rule Borsuk_maps_homotopic_in_path_component)
-      using \<open>closed S\<close> b open_Compl open_path_connected_component apply fastforce
-      done
+                                                         (\<lambda>x. (x - b) /\<^sub>R norm (x - b))"
+    proof -
+      have "path_component (- S) a b"
+        by (metis (full_types) \<open>closed S\<close> b mem_Collect_eq open_Compl open_path_connected_component)
+      then show ?thesis
+        using Borsuk_maps_homotopic_in_path_component by blast
+    qed
     moreover
     obtain c where "homotopic_with_canon (\<lambda>x. True) (ball 0 r) (sphere 0 1)
                                    (\<lambda>x. inverse (norm (x - b)) *\<^sub>R (x - b)) (\<lambda>x. c)"
     proof (rule nullhomotopic_from_contractible)
       show "contractible (ball (0::'a) r)"
         by (metis convex_imp_contractible convex_ball)
       show "continuous_on (ball 0 r) (\<lambda>x. inverse(norm (x - b)) *\<^sub>R (x - b))"
         by (rule continuous_on_Borsuk_map [OF bnot])
       show "(\<lambda>x. (x - b) /\<^sub>R norm (x - b)) ` ball 0 r \<subseteq> sphere 0 1"
         using bnot Borsuk_map_into_sphere by blast
     qed blast
     ultimately have "homotopic_with_canon (\<lambda>x. True) S (sphere 0 1) (\<lambda>x. (x - a) /\<^sub>R norm (x - a)) (\<lambda>x. c)"
       by (meson homotopic_with_subset_left homotopic_with_trans r)
     then show "\<not> ?rhs"
       by blast
   qed
   then show ?thesis by blast
 qed
 
 lemma homotopic_Borsuk_maps_in_bounded_component:
   fixes a :: "'a :: euclidean_space"
   assumes "compact S" and "a \<notin> S"and "b \<notin> S"
       and boc: "bounded (connected_component_set (- S) a)"
       and hom: "homotopic_with_canon (\<lambda>x. True) S (sphere 0 1)
                                (\<lambda>x. (x - a) /\<^sub>R norm (x - a))
                                (\<lambda>x. (x - b) /\<^sub>R norm (x - b))"
    shows "connected_component (- S) a b"
 proof (rule ccontr)
   assume notcc: "\<not> connected_component (- S) a b"
   let ?T = "S \<union> connected_component_set (- S) a"
   have "\<nexists>g. continuous_on (S \<union> connected_component_set (- S) a) g \<and>
             g ` (S \<union> connected_component_set (- S) a) \<subseteq> sphere 0 1 \<and>
             (\<forall>x\<in>S. g x = (x - a) /\<^sub>R norm (x - a))"
     by (simp add: \<open>a \<notin> S\<close> componentsI non_extensible_Borsuk_map [OF \<open>compact S\<close> _ boc])
   moreover obtain g where "continuous_on (S \<union> connected_component_set (- S) a) g"
                           "g ` (S \<union> connected_component_set (- S) a) \<subseteq> sphere 0 1"
                           "\<And>x. x \<in> S \<Longrightarrow> g x = (x - a) /\<^sub>R norm (x - a)"
   proof (rule Borsuk_homotopy_extension_homotopic)
     show "closedin (top_of_set ?T) S"
       by (simp add: \<open>compact S\<close> closed_subset compact_imp_closed)
     show "continuous_on ?T (\<lambda>x. (x - b) /\<^sub>R norm (x - b))"
       by (simp add: \<open>b \<notin> S\<close> notcc continuous_on_Borsuk_map)
     show "(\<lambda>x. (x - b) /\<^sub>R norm (x - b)) ` ?T \<subseteq> sphere 0 1"
       by (simp add: \<open>b \<notin> S\<close> notcc Borsuk_map_into_sphere)
     show "homotopic_with_canon (\<lambda>x. True) S (sphere 0 1)
              (\<lambda>x. (x - b) /\<^sub>R norm (x - b)) (\<lambda>x. (x - a) /\<^sub>R norm (x - a))"
       by (simp add: hom homotopic_with_symD)
     qed (auto simp: ANR_sphere intro: that)
   ultimately show False by blast
 qed
 
 
 lemma Borsuk_maps_homotopic_in_connected_component_eq:
   fixes a :: "'a :: euclidean_space"
   assumes S: "compact S" "a \<notin> S" "b \<notin> S" and 2: "2 \<le> DIM('a)"
     shows "(homotopic_with_canon (\<lambda>x. True) S (sphere 0 1)
                    (\<lambda>x. (x - a) /\<^sub>R norm (x - a))
                    (\<lambda>x. (x - b) /\<^sub>R norm (x - b)) \<longleftrightarrow>
            connected_component (- S) a b)"
          (is "?lhs = ?rhs")
 proof
   assume L: ?lhs
   show ?rhs
   proof (cases "bounded(connected_component_set (- S) a)")
     case True
     show ?thesis
       by (rule homotopic_Borsuk_maps_in_bounded_component [OF S True L])
   next
     case not_bo_a: False
     show ?thesis
     proof (cases "bounded(connected_component_set (- S) b)")
       case True
       show ?thesis
         using homotopic_Borsuk_maps_in_bounded_component [OF S]
         by (simp add: L True assms connected_component_sym homotopic_Borsuk_maps_in_bounded_component homotopic_with_sym)
     next
       case False
       then show ?thesis
         using cobounded_unique_unbounded_component [of "-S" a b] \<open>compact S\<close> not_bo_a
         by (auto simp: compact_eq_bounded_closed assms connected_component_eq_eq)
     qed
   qed
 next
   assume R: ?rhs
   then have "path_component (- S) a b"
     using assms(1) compact_eq_bounded_closed open_Compl open_path_connected_component_set by fastforce
   then show ?lhs
     by (simp add: Borsuk_maps_homotopic_in_path_component)
 qed
 
 subsection\<open>More extension theorems\<close>
 
 lemma extension_from_clopen:
   assumes ope: "openin (top_of_set S) T"
       and clo: "closedin (top_of_set S) T"
       and contf: "continuous_on T f" and fim: "f ` T \<subseteq> U" and null: "U = {} \<Longrightarrow> S = {}"
  obtains g where "continuous_on S g" "g ` S \<subseteq> U" "\<And>x. x \<in> T \<Longrightarrow> g x = f x"
 proof (cases "U = {}")
   case True
   then show ?thesis
     by (simp add: null that)
 next
   case False
   then obtain a where "a \<in> U"
     by auto
   let ?g = "\<lambda>x. if x \<in> T then f x else a"
   have Seq: "S = T \<union> (S - T)"
     using clo closedin_imp_subset by fastforce
   show ?thesis
   proof
     have "continuous_on (T \<union> (S - T)) ?g"
-      apply (rule continuous_on_cases_local)
-      using Seq clo ope by (auto simp: contf intro: continuous_on_cases_local)
+      using Seq clo ope  by (intro continuous_on_cases_local) (auto simp: contf)
     with Seq show "continuous_on S ?g"
       by metis
     show "?g ` S \<subseteq> U"
       using \<open>a \<in> U\<close> fim by auto
     show "\<And>x. x \<in> T \<Longrightarrow> ?g x = f x"
       by auto
   qed
 qed
 
 
 lemma extension_from_component:
   fixes f :: "'a :: euclidean_space \<Rightarrow> 'b :: euclidean_space"
   assumes S: "locally connected S \<or> compact S" and "ANR U"
      and C: "C \<in> components S" and contf: "continuous_on C f" and fim: "f ` C \<subseteq> U"
  obtains g where "continuous_on S g" "g ` S \<subseteq> U" "\<And>x. x \<in> C \<Longrightarrow> g x = f x"
 proof -
   obtain T g where ope: "openin (top_of_set S) T"
                and clo: "closedin (top_of_set S) T"
                and "C \<subseteq> T" and contg: "continuous_on T g" and gim: "g ` T \<subseteq> U"
                and gf: "\<And>x. x \<in> C \<Longrightarrow> g x = f x"
     using S
   proof
     assume "locally connected S"
     show ?thesis
       by (metis C \<open>locally connected S\<close> openin_components_locally_connected closedin_component contf fim order_refl that)
   next
     assume "compact S"
     then obtain W g where "C \<subseteq> W" and opeW: "openin (top_of_set S) W"
                  and contg: "continuous_on W g"
                  and gim: "g ` W \<subseteq> U" and gf: "\<And>x. x \<in> C \<Longrightarrow> g x = f x"
       using ANR_imp_absolute_neighbourhood_extensor [of U C f S] C \<open>ANR U\<close> closedin_component contf fim by blast
     then obtain V where "open V" and V: "W = S \<inter> V"
       by (auto simp: openin_open)
     moreover have "locally compact S"
       by (simp add: \<open>compact S\<close> closed_imp_locally_compact compact_imp_closed)
     ultimately obtain K where opeK: "openin (top_of_set S) K" and "compact K" "C \<subseteq> K" "K \<subseteq> V"
       by (metis C Int_subset_iff \<open>C \<subseteq> W\<close> \<open>compact S\<close> compact_components Sura_Bura_clopen_subset)
     show ?thesis
     proof
       show "closedin (top_of_set S) K"
         by (meson \<open>compact K\<close> \<open>compact S\<close> closedin_compact_eq opeK openin_imp_subset)
       show "continuous_on K g"
         by (metis Int_subset_iff V \<open>K \<subseteq> V\<close> contg continuous_on_subset opeK openin_subtopology subset_eq)
       show "g ` K \<subseteq> U"
         using V \<open>K \<subseteq> V\<close> gim opeK openin_imp_subset by fastforce
     qed (use opeK gf \<open>C \<subseteq> K\<close> in auto)
   qed
   obtain h where "continuous_on S h" "h ` S \<subseteq> U" "\<And>x. x \<in> T \<Longrightarrow> h x = g x"
     using extension_from_clopen
     by (metis C bot.extremum_uniqueI clo contg gim fim image_is_empty in_components_nonempty ope)
   then show ?thesis
     by (metis \<open>C \<subseteq> T\<close> gf subset_eq that)
 qed
 
 
 lemma tube_lemma:
   fixes S :: "'a::euclidean_space set" and T :: "'b::euclidean_space set"
   assumes "compact S" and S: "S \<noteq> {}" "(\<lambda>x. (x,a)) ` S \<subseteq> U" 
       and ope: "openin (top_of_set (S \<times> T)) U"
   obtains V where "openin (top_of_set T) V" "a \<in> V" "S \<times> V \<subseteq> U"
 proof -
   let ?W = "{y. \<exists>x. x \<in> S \<and> (x, y) \<in> (S \<times> T - U)}"
   have "U \<subseteq> S \<times> T" "closedin (top_of_set (S \<times> T)) (S \<times> T - U)"
     using ope by (auto simp: openin_closedin_eq)
   then have "closedin (top_of_set T) ?W"
     using \<open>compact S\<close> closedin_compact_projection by blast
   moreover have "a \<in> T - ?W"
     using \<open>U \<subseteq> S \<times> T\<close> S by auto
   moreover have "S \<times> (T - ?W) \<subseteq> U"
     by auto
   ultimately show ?thesis
     by (metis (no_types, lifting) Sigma_cong closedin_def that topspace_euclidean_subtopology)
 qed
 
 lemma tube_lemma_gen:
   fixes S :: "'a::euclidean_space set" and T :: "'b::euclidean_space set"
   assumes "compact S" "S \<noteq> {}" "T \<subseteq> T'" "S \<times> T \<subseteq> U"
       and ope: "openin (top_of_set (S \<times> T')) U"
   obtains V where "openin (top_of_set T') V" "T \<subseteq> V" "S \<times> V \<subseteq> U"
 proof -
   have "\<And>x. x \<in> T \<Longrightarrow> \<exists>V. openin (top_of_set T') V \<and> x \<in> V \<and> S \<times> V \<subseteq> U"
     using assms by (auto intro:  tube_lemma [OF \<open>compact S\<close>])
   then obtain F where F: "\<And>x. x \<in> T \<Longrightarrow> openin (top_of_set T') (F x) \<and> x \<in> F x \<and> S \<times> F x \<subseteq> U"
     by metis
   show ?thesis
   proof
     show "openin (top_of_set T') (\<Union>(F ` T))"
       using F by blast
     show "T \<subseteq> \<Union>(F ` T)"
       using F by blast
     show "S \<times> \<Union>(F ` T) \<subseteq> U"
       using F by auto
   qed
 qed
 
 proposition\<^marker>\<open>tag unimportant\<close> homotopic_neighbourhood_extension:
   fixes f :: "'a::euclidean_space \<Rightarrow> 'b::euclidean_space"
   assumes contf: "continuous_on S f" and fim: "f ` S \<subseteq> U"
       and contg: "continuous_on S g" and gim: "g ` S \<subseteq> U"
       and clo: "closedin (top_of_set S) T"
       and "ANR U" and hom: "homotopic_with_canon (\<lambda>x. True) T U f g"
     obtains V where "T \<subseteq> V" "openin (top_of_set S) V"
                     "homotopic_with_canon (\<lambda>x. True) V U f g"
 proof -
   have "T \<subseteq> S"
     using clo closedin_imp_subset by blast
   obtain h where conth: "continuous_on ({0..1::real} \<times> T) h"
              and him: "h ` ({0..1} \<times> T) \<subseteq> U"
              and h0: "\<And>x. h(0, x) = f x" and h1: "\<And>x. h(1, x) = g x"
     using hom by (auto simp: homotopic_with_def)
   define h' where "h' \<equiv> \<lambda>z. if fst z \<in> {0} then f(snd z)
                              else if fst z \<in> {1} then g(snd z)
                              else h z"
   let ?S0 = "{0::real} \<times> S" and ?S1 = "{1::real} \<times> S"
   have "continuous_on(?S0 \<union> (?S1 \<union> {0..1} \<times> T)) h'"
     unfolding h'_def
   proof (intro continuous_on_cases_local)
     show "closedin (top_of_set (?S0 \<union> (?S1 \<union> {0..1} \<times> T))) ?S0"
          "closedin (top_of_set (?S1 \<union> {0..1} \<times> T)) ?S1"
       using \<open>T \<subseteq> S\<close> by (force intro: closedin_Times closedin_subset_trans [of "{0..1} \<times> S"])+
     show "closedin (top_of_set (?S0 \<union> (?S1 \<union> {0..1} \<times> T))) (?S1 \<union> {0..1} \<times> T)"
          "closedin (top_of_set (?S1 \<union> {0..1} \<times> T)) ({0..1} \<times> T)"
       using \<open>T \<subseteq> S\<close> by (force intro: clo closedin_Times closedin_subset_trans [of "{0..1} \<times> S"])+
     show "continuous_on (?S0) (\<lambda>x. f (snd x))"
       by (intro continuous_intros continuous_on_compose2 [OF contf]) auto
     show "continuous_on (?S1) (\<lambda>x. g (snd x))"
       by (intro continuous_intros continuous_on_compose2 [OF contg]) auto
   qed (use h0 h1 conth in auto)
   then have "continuous_on ({0,1} \<times> S \<union> ({0..1} \<times> T)) h'"
     by (metis Sigma_Un_distrib1 Un_assoc insert_is_Un) 
   moreover have "h' ` ({0,1} \<times> S \<union> {0..1} \<times> T) \<subseteq> U"
     using fim gim him \<open>T \<subseteq> S\<close> unfolding h'_def by force
   moreover have "closedin (top_of_set ({0..1::real} \<times> S)) ({0,1} \<times> S \<union> {0..1::real} \<times> T)"
     by (intro closedin_Times closedin_Un clo) (simp_all add: closed_subset)
   ultimately
   obtain W k where W: "({0,1} \<times> S) \<union> ({0..1} \<times> T) \<subseteq> W"
                and opeW: "openin (top_of_set ({0..1} \<times> S)) W"
                and contk: "continuous_on W k"
                and kim: "k ` W \<subseteq> U"
                and kh': "\<And>x. x \<in> ({0,1} \<times> S) \<union> ({0..1} \<times> T) \<Longrightarrow> k x = h' x"
     by (metis ANR_imp_absolute_neighbourhood_extensor [OF \<open>ANR U\<close>, of "({0,1} \<times> S) \<union> ({0..1} \<times> T)" h' "{0..1} \<times> S"])
   obtain T' where opeT': "openin (top_of_set S) T'" 
               and "T \<subseteq> T'" and TW: "{0..1} \<times> T' \<subseteq> W"
     using tube_lemma_gen [of "{0..1::real}" T S W] W \<open>T \<subseteq> S\<close> opeW by auto
   moreover have "homotopic_with_canon (\<lambda>x. True) T' U f g"
   proof (simp add: homotopic_with, intro exI conjI)
     show "continuous_on ({0..1} \<times> T') k"
       using TW continuous_on_subset contk by auto
     show "k ` ({0..1} \<times> T') \<subseteq> U"
       using TW kim by fastforce
     have "T' \<subseteq> S"
       by (meson opeT' subsetD openin_imp_subset)
     then show "\<forall>x\<in>T'. k (0, x) = f x" "\<forall>x\<in>T'. k (1, x) = g x"
       by (auto simp: kh' h'_def)
   qed
   ultimately show ?thesis
     by (blast intro: that)
 qed
 
 text\<open> Homotopy on a union of closed-open sets.\<close>
 proposition\<^marker>\<open>tag unimportant\<close> homotopic_on_clopen_Union:
   fixes \<F> :: "'a::euclidean_space set set"
   assumes "\<And>S. S \<in> \<F> \<Longrightarrow> closedin (top_of_set (\<Union>\<F>)) S"
       and "\<And>S. S \<in> \<F> \<Longrightarrow> openin (top_of_set (\<Union>\<F>)) S"
       and "\<And>S. S \<in> \<F> \<Longrightarrow> homotopic_with_canon (\<lambda>x. True) S T f g"
   shows "homotopic_with_canon (\<lambda>x. True) (\<Union>\<F>) T f g"
 proof -
   obtain \<V> where "\<V> \<subseteq> \<F>" "countable \<V>" and eqU: "\<Union>\<V> = \<Union>\<F>"
     using Lindelof_openin assms by blast
   show ?thesis
   proof (cases "\<V> = {}")
     case True
     then show ?thesis
       by (metis Union_empty eqU homotopic_with_canon_on_empty)
   next
     case False
     then obtain V :: "nat \<Rightarrow> 'a set" where V: "range V = \<V>"
       using range_from_nat_into \<open>countable \<V>\<close> by metis
     with \<open>\<V> \<subseteq> \<F>\<close> have clo: "\<And>n. closedin (top_of_set (\<Union>\<F>)) (V n)"
                   and ope: "\<And>n. openin (top_of_set (\<Union>\<F>)) (V n)"
                   and hom: "\<And>n. homotopic_with_canon (\<lambda>x. True) (V n) T f g"
       using assms by auto 
     then obtain h where conth: "\<And>n. continuous_on ({0..1::real} \<times> V n) (h n)"
                   and him: "\<And>n. h n ` ({0..1} \<times> V n) \<subseteq> T" 
                   and h0: "\<And>n. \<And>x. x \<in> V n \<Longrightarrow> h n (0, x) = f x" 
                   and h1: "\<And>n. \<And>x. x \<in> V n \<Longrightarrow> h n (1, x) = g x"
       by (simp add: homotopic_with) metis
     have wop: "b \<in> V x \<Longrightarrow> \<exists>k. b \<in> V k \<and> (\<forall>j<k. b \<notin> V j)" for b x
         using nat_less_induct [where P = "\<lambda>i. b \<notin> V i"] by meson
     obtain \<zeta> where cont: "continuous_on ({0..1} \<times> \<Union>(V ` UNIV)) \<zeta>"
               and eq: "\<And>x i. \<lbrakk>x \<in> {0..1} \<times> \<Union>(V ` UNIV) \<inter>
                                    {0..1} \<times> (V i - (\<Union>m<i. V m))\<rbrakk> \<Longrightarrow> \<zeta> x = h i x"
     proof (rule pasting_lemma_exists)
       let ?X = "top_of_set ({0..1::real} \<times> \<Union>(range V))"
       show "topspace ?X \<subseteq> (\<Union>i. {0..1::real} \<times> (V i - (\<Union>m<i. V m)))"
         by (force simp: Ball_def dest: wop)
       show "openin (top_of_set ({0..1} \<times> \<Union>(V ` UNIV))) 
                    ({0..1::real} \<times> (V i - (\<Union>m<i. V m)))" for i
       proof (intro openin_Times openin_subtopology_self openin_diff)
         show "openin (top_of_set (\<Union>(V ` UNIV))) (V i)"
           using ope V eqU by auto
         show "closedin (top_of_set (\<Union>(V ` UNIV))) (\<Union>m<i. V m)"
           using V clo eqU by (force intro: closedin_Union)
       qed
       show "continuous_map (subtopology ?X ({0..1} \<times> (V i - \<Union> (V ` {..<i})))) euclidean (h i)"  for i
         by (auto simp add: subtopology_subtopology intro!: continuous_on_subset [OF conth])
       show "\<And>i j x. x \<in> topspace ?X \<inter> {0..1} \<times> (V i - (\<Union>m<i. V m)) \<inter> {0..1} \<times> (V j - (\<Union>m<j. V m))
                     \<Longrightarrow> h i x = h j x"
         by clarsimp (metis lessThan_iff linorder_neqE_nat)
     qed auto
     show ?thesis
     proof (simp add: homotopic_with eqU [symmetric], intro exI conjI ballI)
       show "continuous_on ({0..1} \<times> \<Union>\<V>) \<zeta>"
         using V eqU by (blast intro!:  continuous_on_subset [OF cont])
       show "\<zeta>` ({0..1} \<times> \<Union>\<V>) \<subseteq> T"
       proof clarsimp
         fix t :: real and y :: "'a" and X :: "'a set"
         assume "y \<in> X" "X \<in> \<V>" and t: "0 \<le> t" "t \<le> 1"
         then obtain k where "y \<in> V k" and j: "\<forall>j<k. y \<notin> V j"
           by (metis image_iff V wop)
         with him t show "\<zeta>(t, y) \<in> T"
           by (subst eq) force+
       qed
       fix X y
       assume "X \<in> \<V>" "y \<in> X"
       then obtain k where "y \<in> V k" and j: "\<forall>j<k. y \<notin> V j"
         by (metis image_iff V wop)
       then show "\<zeta>(0, y) = f y" and "\<zeta>(1, y) = g y"
         by (subst eq [where i=k]; force simp: h0 h1)+ 
     qed
   qed
 qed
 
 lemma homotopic_on_components_eq:
   fixes S :: "'a :: euclidean_space set" and T :: "'b :: euclidean_space set"
   assumes S: "locally connected S \<or> compact S" and "ANR T"
   shows "homotopic_with_canon (\<lambda>x. True) S T f g \<longleftrightarrow>
          (continuous_on S f \<and> f ` S \<subseteq> T \<and> continuous_on S g \<and> g ` S \<subseteq> T) \<and>
          (\<forall>C \<in> components S. homotopic_with_canon (\<lambda>x. True) C T f g)"
     (is "?lhs \<longleftrightarrow> ?C \<and> ?rhs")
 proof -
   have "continuous_on S f" "f ` S \<subseteq> T" "continuous_on S g" "g ` S \<subseteq> T" if ?lhs
     using homotopic_with_imp_continuous homotopic_with_imp_subset1 homotopic_with_imp_subset2 that by blast+
   moreover have "?lhs \<longleftrightarrow> ?rhs"
     if contf: "continuous_on S f" and fim: "f ` S \<subseteq> T" and contg: "continuous_on S g" and gim: "g ` S \<subseteq> T"
   proof
     assume ?lhs
     with that show ?rhs
       by (simp add: homotopic_with_subset_left in_components_subset)
   next
     assume R: ?rhs
     have "\<exists>U. C \<subseteq> U \<and> closedin (top_of_set S) U \<and>
               openin (top_of_set S) U \<and>
               homotopic_with_canon (\<lambda>x. True) U T f g" if C: "C \<in> components S" for C
     proof -
       have "C \<subseteq> S"
         by (simp add: in_components_subset that)
       show ?thesis
         using S
       proof
         assume "locally connected S"
         show ?thesis
         proof (intro exI conjI)
           show "closedin (top_of_set S) C"
             by (simp add: closedin_component that)
           show "openin (top_of_set S) C"
             by (simp add: \<open>locally connected S\<close> openin_components_locally_connected that)
           show "homotopic_with_canon (\<lambda>x. True) C T f g"
             by (simp add: R that)
         qed auto
       next
         assume "compact S"
         have hom: "homotopic_with_canon (\<lambda>x. True) C T f g"
           using R that by blast
         obtain U where "C \<subseteq> U" and opeU: "openin (top_of_set S) U"
                   and hom: "homotopic_with_canon (\<lambda>x. True) U T f g"
           using homotopic_neighbourhood_extension [OF contf fim contg gim _ \<open>ANR T\<close> hom]
             \<open>C \<in> components S\<close> closedin_component by blast
         then obtain V where "open V" and V: "U = S \<inter> V"
           by (auto simp: openin_open)
         moreover have "locally compact S"
           by (simp add: \<open>compact S\<close> closed_imp_locally_compact compact_imp_closed)
         ultimately obtain K where opeK: "openin (top_of_set S) K" and "compact K" "C \<subseteq> K" "K \<subseteq> V"
           by (metis C Int_subset_iff Sura_Bura_clopen_subset \<open>C \<subseteq> U\<close> \<open>compact S\<close> compact_components)
         show ?thesis
         proof (intro exI conjI)
           show "closedin (top_of_set S) K"
             by (meson \<open>compact K\<close> \<open>compact S\<close> closedin_compact_eq opeK openin_imp_subset)
           show "homotopic_with_canon (\<lambda>x. True) K T f g"
             using V \<open>K \<subseteq> V\<close> hom homotopic_with_subset_left opeK openin_imp_subset by fastforce
         qed (use opeK \<open>C \<subseteq> K\<close> in auto)
       qed
     qed
     then obtain \<phi> where \<phi>: "\<And>C. C \<in> components S \<Longrightarrow> C \<subseteq> \<phi> C"
                   and clo\<phi>: "\<And>C. C \<in> components S \<Longrightarrow> closedin (top_of_set S) (\<phi> C)"
                   and ope\<phi>: "\<And>C. C \<in> components S \<Longrightarrow> openin (top_of_set S) (\<phi> C)"
                   and hom\<phi>: "\<And>C. C \<in> components S \<Longrightarrow> homotopic_with_canon (\<lambda>x. True) (\<phi> C) T f g"
       by metis
     have Seq: "S = \<Union> (\<phi> ` components S)"
     proof
       show "S \<subseteq> \<Union> (\<phi> ` components S)"
         by (metis Sup_mono Union_components \<phi> imageI)
       show "\<Union> (\<phi> ` components S) \<subseteq> S"
         using ope\<phi> openin_imp_subset by fastforce
     qed
     show ?lhs
       apply (subst Seq)
-      apply (rule homotopic_on_clopen_Union)
-      using Seq clo\<phi> ope\<phi> hom\<phi> by auto
+      using Seq clo\<phi> ope\<phi> hom\<phi> by (intro homotopic_on_clopen_Union) auto
   qed
   ultimately show ?thesis by blast
 qed
 
 
 lemma cohomotopically_trivial_on_components:
   fixes S :: "'a :: euclidean_space set" and T :: "'b :: euclidean_space set"
   assumes S: "locally connected S \<or> compact S" and "ANR T"
   shows
    "(\<forall>f g. continuous_on S f \<longrightarrow> f ` S \<subseteq> T \<longrightarrow> continuous_on S g \<longrightarrow> g ` S \<subseteq> T \<longrightarrow>
            homotopic_with_canon (\<lambda>x. True) S T f g)
     \<longleftrightarrow>
     (\<forall>C\<in>components S.
         \<forall>f g. continuous_on C f \<longrightarrow> f ` C \<subseteq> T \<longrightarrow> continuous_on C g \<longrightarrow> g ` C \<subseteq> T \<longrightarrow>
               homotopic_with_canon (\<lambda>x. True) C T f g)"
      (is "?lhs = ?rhs")
 proof
   assume L[rule_format]: ?lhs
   show ?rhs
   proof clarify
     fix C f g
     assume contf: "continuous_on C f" and fim: "f ` C \<subseteq> T"
        and contg: "continuous_on C g" and gim: "g ` C \<subseteq> T" and C: "C \<in> components S"
     obtain f' where contf': "continuous_on S f'" and f'im: "f' ` S \<subseteq> T" and f'f: "\<And>x. x \<in> C \<Longrightarrow> f' x = f x"
       using extension_from_component [OF S \<open>ANR T\<close> C contf fim] by metis
     obtain g' where contg': "continuous_on S g'" and g'im: "g' ` S \<subseteq> T" and g'g: "\<And>x. x \<in> C \<Longrightarrow> g' x = g x"
       using extension_from_component [OF S \<open>ANR T\<close> C contg gim] by metis
     have "homotopic_with_canon (\<lambda>x. True) C T f' g'"
       using L [OF contf' f'im contg' g'im] homotopic_with_subset_left C in_components_subset by fastforce
     then show "homotopic_with_canon (\<lambda>x. True) C T f g"
       using f'f g'g homotopic_with_eq by force
   qed
 next
   assume R [rule_format]: ?rhs
   show ?lhs
   proof clarify
     fix f g
     assume contf: "continuous_on S f" and fim: "f ` S \<subseteq> T"
       and contg: "continuous_on S g" and gim: "g ` S \<subseteq> T"
     moreover have "homotopic_with_canon (\<lambda>x. True) C T f g" if "C \<in> components S" for C
       using R [OF that]
       by (meson contf contg continuous_on_subset fim gim image_mono in_components_subset order.trans that)
     ultimately show "homotopic_with_canon (\<lambda>x. True) S T f g"
       by (subst homotopic_on_components_eq [OF S \<open>ANR T\<close>]) auto
   qed
 qed
 
 subsection\<open>The complement of a set and path-connectedness\<close>
 
 text\<open>Complement in dimension N > 1 of set homeomorphic to any interval in
  any dimension is (path-)connected. This naively generalizes the argument
  in Ryuji Maehara's paper "The Jordan curve theorem via the Brouwer fixed point theorem",
 American Mathematical Monthly 1984.\<close>
 
 lemma unbounded_components_complement_absolute_retract:
   fixes S :: "'a::euclidean_space set"
   assumes C: "C \<in> components(- S)" and S: "compact S" "AR S"
     shows "\<not> bounded C"
 proof -
   obtain y where y: "C = connected_component_set (- S) y" and "y \<notin> S"
     using C by (auto simp: components_def)
   have "open(- S)"
     using S by (simp add: closed_open compact_eq_bounded_closed)
   have "S retract_of UNIV"
     using S compact_AR by blast
   then obtain r where contr: "continuous_on UNIV r" and ontor: "range r \<subseteq> S"
                   and r: "\<And>x. x \<in> S \<Longrightarrow> r x = x"
     by (auto simp: retract_of_def retraction_def)
   show ?thesis
   proof
     assume "bounded C"
     have "connected_component_set (- S) y \<subseteq> S"
     proof (rule frontier_subset_retraction)
       show "bounded (connected_component_set (- S) y)"
         using \<open>bounded C\<close> y by blast
       show "frontier (connected_component_set (- S) y) \<subseteq> S"
         using C \<open>compact S\<close> compact_eq_bounded_closed frontier_of_components_closed_complement y by blast
       show "continuous_on (closure (connected_component_set (- S) y)) r"
         by (blast intro: continuous_on_subset [OF contr])
     qed (use ontor r in auto)
     with \<open>y \<notin> S\<close> show False by force
   qed
 qed
 
 lemma connected_complement_absolute_retract:
   fixes S :: "'a::euclidean_space set"
   assumes S: "compact S" "AR S" and 2: "2 \<le> DIM('a)"
     shows "connected(- S)"
 proof -
   have "S retract_of UNIV"
     using S compact_AR by blast
   show ?thesis
-    apply (clarsimp simp: connected_iff_connected_component_eq)
-    apply (rule cobounded_unique_unbounded_component [OF _ 2])
-      apply (simp add: \<open>compact S\<close> compact_imp_bounded)
-     apply (meson ComplI S componentsI unbounded_components_complement_absolute_retract)+
-    done
+  proof (clarsimp simp: connected_iff_connected_component_eq)
+    have "\<not> bounded (connected_component_set (- S) x)" if "x \<notin> S" for x
+      by (meson Compl_iff assms componentsI that unbounded_components_complement_absolute_retract)
+    then show "connected_component_set (- S) x = connected_component_set (- S) y" 
+      if "x \<notin> S" "y \<notin> S" for x y
+      using cobounded_unique_unbounded_component [OF _ 2]
+      by (metis \<open>compact S\<close> compact_imp_bounded double_compl that)
+  qed
 qed
 
 lemma path_connected_complement_absolute_retract:
   fixes S :: "'a::euclidean_space set"
   assumes "compact S" "AR S" "2 \<le> DIM('a)"
     shows "path_connected(- S)"
   using connected_complement_absolute_retract [OF assms]
   using \<open>compact S\<close> compact_eq_bounded_closed connected_open_path_connected by blast
 
 theorem connected_complement_homeomorphic_convex_compact:
   fixes S :: "'a::euclidean_space set" and T :: "'b::euclidean_space set"
   assumes hom: "S homeomorphic T" and T: "convex T" "compact T" and 2: "2 \<le> DIM('a)"
     shows "connected(- S)"
 proof (cases "S = {}")
   case True
   then show ?thesis
     by (simp add: connected_UNIV)
 next
   case False
   show ?thesis
   proof (rule connected_complement_absolute_retract)
     show "compact S"
       using \<open>compact T\<close> hom homeomorphic_compactness by auto
     show "AR S"
       by (meson AR_ANR False \<open>convex T\<close> convex_imp_ANR convex_imp_contractible hom homeomorphic_ANR_iff_ANR homeomorphic_contractible_eq)
   qed (rule 2)
 qed
 
 corollary path_connected_complement_homeomorphic_convex_compact:
   fixes S :: "'a::euclidean_space set" and T :: "'b::euclidean_space set"
   assumes hom: "S homeomorphic T" "convex T" "compact T" "2 \<le> DIM('a)"
     shows "path_connected(- S)"
   using connected_complement_homeomorphic_convex_compact [OF assms]
   using \<open>compact T\<close> compact_eq_bounded_closed connected_open_path_connected hom homeomorphic_compactness by blast
 
 lemma path_connected_complement_homeomorphic_interval:
   fixes S :: "'a::euclidean_space set"
   assumes "S homeomorphic cbox a b" "2 \<le> DIM('a)"
   shows "path_connected(-S)"
   using assms compact_cbox convex_box(1) path_connected_complement_homeomorphic_convex_compact by blast
 
 lemma connected_complement_homeomorphic_interval:
   fixes S :: "'a::euclidean_space set"
   assumes "S homeomorphic cbox a b" "2 \<le> DIM('a)"
   shows "connected(-S)"
   using assms path_connected_complement_homeomorphic_interval path_connected_imp_connected by blast
 
-
 end