# HG changeset patch
# User paulson <lp15@cam.ac.uk>
# Date 1676550081 0
# Node ID c6b50597abbcb5275da3fb952f4947481657620d
# Parent  29032b496f2e6d42c0837f2521a764ecd880ac59
More of Eberl's contributions: memomorphic functions

diff -r 29032b496f2e -r c6b50597abbc src/HOL/Complex_Analysis/Complex_Analysis.thy
--- a/src/HOL/Complex_Analysis/Complex_Analysis.thy	Thu Feb 16 10:42:39 2023 +0000
+++ b/src/HOL/Complex_Analysis/Complex_Analysis.thy	Thu Feb 16 12:21:21 2023 +0000
@@ -1,7 +1,7 @@
 theory Complex_Analysis
 imports
   Residue_Theorem
-  Riemann_Mapping
+  Meromorphic
 begin
 
 end
diff -r 29032b496f2e -r c6b50597abbc src/HOL/Complex_Analysis/Complex_Singularities.thy
--- a/src/HOL/Complex_Analysis/Complex_Singularities.thy	Thu Feb 16 10:42:39 2023 +0000
+++ b/src/HOL/Complex_Analysis/Complex_Singularities.thy	Thu Feb 16 12:21:21 2023 +0000
@@ -249,6 +249,12 @@
   shows   "not_essential f z \<longleftrightarrow> not_essential g z'"
   unfolding not_essential_def using assms filterlim_cong is_pole_cong by fastforce
 
+lemma not_essential_compose_iff:
+  assumes "filtermap g (at z) = at z'"
+  shows   "not_essential (f \<circ> g) z = not_essential f z'"
+  unfolding not_essential_def filterlim_def filtermap_compose assms is_pole_compose_iff[OF assms]
+  by blast
+
 lemma isolated_singularity_at_cong:
   assumes "eventually (\<lambda>x. f x = g x) (at z)" "z = z'"
   shows   "isolated_singularity_at f z \<longleftrightarrow> isolated_singularity_at g z'"
@@ -362,8 +368,8 @@
       ultimately have "(f' \<longlongrightarrow> 0) F" unfolding F_def
         by (simp add: continuous_within)
       moreover have "(g \<longlongrightarrow> g z) F"
-        using holomorphic_on_imp_continuous_on[OF g_holo,unfolded continuous_on_def] \<open>r>0\<close>
-        unfolding F_def by auto
+        unfolding F_def
+        using \<open>r>0\<close> centre_in_ball continuous_on_def g_holo holomorphic_on_imp_continuous_on by blast
       ultimately show " ((\<lambda>w. f' w * g w) \<longlongrightarrow> 0) F" using tendsto_mult by fastforce
     qed
     moreover have "(h \<longlongrightarrow> h z) (at z within ball z r)"
@@ -1058,7 +1064,7 @@
   using analytic_at not_is_pole_holomorphic by blast
 
 lemma not_essential_const [singularity_intros]: "not_essential (\<lambda>_. c) z"
-  unfolding not_essential_def by (rule exI[of _ c]) auto
+  by blast
 
 lemma not_essential_uminus [singularity_intros]:
   assumes f_ness: "not_essential f z"
diff -r 29032b496f2e -r c6b50597abbc src/HOL/Complex_Analysis/Laurent_Convergence.thy
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/Complex_Analysis/Laurent_Convergence.thy	Thu Feb 16 12:21:21 2023 +0000
@@ -0,0 +1,2917 @@
+theory Laurent_Convergence
+  imports "HOL-Computational_Algebra.Formal_Laurent_Series" "HOL-Library.Landau_Symbols"
+          Residue_Theorem
+
+begin
+
+(* TODO: Move *)
+text \<open>TODO: Better than @{thm deriv_compose_linear}?\<close>
+lemma deriv_compose_linear':
+  assumes "f field_differentiable at (c * z+a)"
+  shows "deriv (\<lambda>w. f (c * w+a)) z = c * deriv f (c * z+a)"
+  apply (subst deriv_chain[where f="\<lambda>w. c * w+a",unfolded comp_def])
+  using assms by (auto intro:derivative_intros)
+
+text \<open>TODO: Better than @{thm higher_deriv_compose_linear}?\<close>
+lemma higher_deriv_compose_linear':
+  fixes z::complex
+  assumes f: "f holomorphic_on T" and S: "open S" and T: "open T" and z: "z \<in> S"
+      and fg: "\<And>w. w \<in> S \<Longrightarrow> u * w+c \<in> T"
+    shows "(deriv ^^ n) (\<lambda>w. f (u * w+c)) z = u^n * (deriv ^^ n) f (u * z+c)"
+using z
+proof (induction n arbitrary: z)
+  case 0 then show ?case by simp
+next
+  case (Suc n z)
+  have holo0: "f holomorphic_on (\<lambda>w. u * w+c) ` S"
+    by (meson fg f holomorphic_on_subset image_subset_iff)
+  have holo2: "(deriv ^^ n) f holomorphic_on (\<lambda>w. u * w+c) ` S"
+    by (meson f fg holomorphic_higher_deriv holomorphic_on_subset image_subset_iff T)
+  have holo3: "(\<lambda>z. u ^ n * (deriv ^^ n) f (u * z+c)) holomorphic_on S"
+    by (intro holo2 holomorphic_on_compose [where g="(deriv ^^ n) f", unfolded o_def] holomorphic_intros)
+  have "(\<lambda>w. u * w+c) holomorphic_on S" "f holomorphic_on (\<lambda>w. u * w+c) ` S"
+    by (rule holo0 holomorphic_intros)+
+  then have holo1: "(\<lambda>w. f (u * w+c)) holomorphic_on S"
+    by (rule holomorphic_on_compose [where g=f, unfolded o_def])
+  have "deriv ((deriv ^^ n) (\<lambda>w. f (u * w+c))) z = deriv (\<lambda>z. u^n * (deriv ^^ n) f (u*z+c)) z"
+  proof (rule complex_derivative_transform_within_open [OF _ holo3 S Suc.prems])
+    show "(deriv ^^ n) (\<lambda>w. f (u * w+c)) holomorphic_on S"
+      by (rule holomorphic_higher_deriv [OF holo1 S])
+  qed (simp add: Suc.IH)
+  also have "\<dots> = u^n * deriv (\<lambda>z. (deriv ^^ n) f (u * z+c)) z"
+  proof -
+    have "(deriv ^^ n) f analytic_on T"
+      by (simp add: analytic_on_open f holomorphic_higher_deriv T)
+    then have "(\<lambda>w. (deriv ^^ n) f (u * w+c)) analytic_on S"
+    proof -
+      have "(deriv ^^ n) f \<circ> (\<lambda>w. u * w+c) holomorphic_on S"
+        using holomorphic_on_compose[OF _ holo2] \<open>(\<lambda>w. u * w+c) holomorphic_on S\<close>
+        by simp
+      then show ?thesis
+        by (simp add: S analytic_on_open o_def)
+    qed
+    then show ?thesis
+      by (intro deriv_cmult analytic_on_imp_differentiable_at [OF _ Suc.prems])
+  qed
+  also have "\<dots> = u * u ^ n * deriv ((deriv ^^ n) f) (u * z+c)"
+  proof -
+    have "(deriv ^^ n) f field_differentiable at (u * z+c)"
+      using Suc.prems T f fg holomorphic_higher_deriv holomorphic_on_imp_differentiable_at by blast
+    then show ?thesis
+      by (simp add: deriv_compose_linear')
+  qed
+  finally show ?case
+    by simp
+qed
+
+lemma fps_to_fls_numeral [simp]: "fps_to_fls (numeral n) = numeral n"
+  by (metis fps_to_fls_of_nat of_nat_numeral)
+
+lemma fls_const_power: "fls_const (a ^ b) = fls_const a ^ b"
+  by (induction b) (auto simp flip: fls_const_mult_const)
+
+lemma fls_deriv_numeral [simp]: "fls_deriv (numeral n) = 0"
+  by (metis fls_deriv_of_int of_int_numeral)
+
+lemma fls_const_numeral [simp]: "fls_const (numeral n) = numeral n"
+  by (metis fls_of_nat of_nat_numeral)
+
+lemma fls_mult_of_int_nth [simp]:
+  shows "fls_nth (numeral k * f) n = numeral k * fls_nth f n"
+  and   "fls_nth (f * numeral k) n = fls_nth f n * numeral k"
+  by (metis fls_const_numeral fls_mult_const_nth)+
+
+lemma fls_nth_numeral' [simp]:
+  "fls_nth (numeral n) 0 = numeral n" "k \<noteq> 0 \<Longrightarrow> fls_nth (numeral n) k = 0"
+  by (subst fls_const_numeral [symmetric], subst fls_const_nth, simp)+
+
+lemma fls_subdegree_prod:
+  fixes F :: "'a \<Rightarrow> 'b :: field_char_0 fls"
+  assumes "\<And>x. x \<in> I \<Longrightarrow> F x \<noteq> 0"
+  shows   "fls_subdegree (\<Prod>x\<in>I. F x) = (\<Sum>x\<in>I. fls_subdegree (F x))"
+  using assms by (induction I rule: infinite_finite_induct) auto
+
+lemma fls_subdegree_prod':
+  fixes F :: "'a \<Rightarrow> 'b :: field_char_0 fls"
+  assumes "\<And>x. x \<in> I \<Longrightarrow> fls_subdegree (F x) \<noteq> 0"
+  shows   "fls_subdegree (\<Prod>x\<in>I. F x) = (\<Sum>x\<in>I. fls_subdegree (F x))"
+proof (intro fls_subdegree_prod)
+  show "F x \<noteq> 0" if "x \<in> I" for x
+    using assms[OF that] by auto
+qed
+
+instance fps :: (semiring_char_0) semiring_char_0
+proof
+  show "inj (of_nat :: nat \<Rightarrow> 'a fps)"
+  proof
+    fix m n :: nat
+    assume "of_nat m = (of_nat n :: 'a fps)"
+    hence "fps_nth (of_nat m) 0 = (fps_nth (of_nat n) 0 :: 'a)"
+      by (simp only: )
+    thus "m = n"
+      by simp
+  qed
+qed
+
+instance fls :: (semiring_char_0) semiring_char_0
+proof
+  show "inj (of_nat :: nat \<Rightarrow> 'a fls)"
+  proof
+    fix m n :: nat
+    assume "of_nat m = (of_nat n :: 'a fls)"
+    hence "fls_nth (of_nat m) 0 = (fls_nth (of_nat n) 0 :: 'a)"
+      by (simp only: )
+    thus "m = n"
+      by (simp add: fls_of_nat_nth)
+  qed
+qed
+
+lemma fls_const_eq_0_iff [simp]: "fls_const c = 0 \<longleftrightarrow> c = 0"
+  using fls_const_0 fls_const_nonzero by blast
+
+lemma fls_subdegree_add_eq1:
+  assumes "f \<noteq> 0" "fls_subdegree f < fls_subdegree g"
+  shows   "fls_subdegree (f + g) = fls_subdegree f"
+proof (intro antisym)
+  from assms have *: "fls_nth (f + g) (fls_subdegree f) \<noteq> 0"
+    by auto
+  from * show "fls_subdegree (f + g) \<le> fls_subdegree f"
+    by (rule fls_subdegree_leI)
+  from * have "f + g \<noteq> 0"
+    using fls_nonzeroI by blast
+  thus "fls_subdegree f \<le> fls_subdegree (f + g)"
+    using assms(2) fls_plus_subdegree by force
+qed
+
+lemma fls_subdegree_add_eq2:
+  assumes "g \<noteq> 0" "fls_subdegree g < fls_subdegree f"
+  shows   "fls_subdegree (f + g) = fls_subdegree g"
+proof (intro antisym)
+  from assms have *: "fls_nth (f + g) (fls_subdegree g) \<noteq> 0"
+    by auto
+  from * show "fls_subdegree (f + g) \<le> fls_subdegree g"
+    by (rule fls_subdegree_leI)
+  from * have "f + g \<noteq> 0"
+    using fls_nonzeroI by blast
+  thus "fls_subdegree g \<le> fls_subdegree (f + g)"
+    using assms(2) fls_plus_subdegree by force
+qed
+
+lemma fls_subdegree_diff_eq1:
+  assumes "f \<noteq> 0" "fls_subdegree f < fls_subdegree g"
+  shows   "fls_subdegree (f - g) = fls_subdegree f"
+  using fls_subdegree_add_eq1[of f "-g"] assms by simp
+
+lemma fls_subdegree_diff_eq2:
+  assumes "g \<noteq> 0" "fls_subdegree g < fls_subdegree f"
+  shows   "fls_subdegree (f - g) = fls_subdegree g"
+  using fls_subdegree_add_eq2[of "-g" f] assms by simp
+
+lemma nat_minus_fls_subdegree_plus_const_eq:
+  "nat (-fls_subdegree (F + fls_const c)) = nat (-fls_subdegree F)"
+proof (cases "fls_subdegree F < 0")
+  case True
+  hence "fls_subdegree (F + fls_const c) = fls_subdegree F"
+    by (intro fls_subdegree_add_eq1) auto
+  thus ?thesis
+    by simp
+next
+  case False
+  thus ?thesis
+    by (auto simp: fls_subdegree_ge0I)
+qed
+
+lemma at_to_0': "NO_MATCH 0 z \<Longrightarrow> at z = filtermap (\<lambda>x. x + z) (at 0)"
+  for z :: "'a::real_normed_vector"
+  by (rule at_to_0)
+
+lemma nhds_to_0: "nhds (x :: 'a :: real_normed_vector) = filtermap ((+) x) (nhds 0)"
+proof -
+  have "(\<lambda>xa. xa - - x) = (+) x"
+    by auto
+  thus ?thesis
+    using filtermap_nhds_shift[of "-x" 0] by simp
+qed
+
+lemma nhds_to_0': "NO_MATCH 0 x \<Longrightarrow> nhds (x :: 'a :: real_normed_vector) = filtermap ((+) x) (nhds 0)"
+  by (rule nhds_to_0)
+
+
+definition%important fls_conv_radius :: "complex fls \<Rightarrow> ereal" where
+  "fls_conv_radius f = fps_conv_radius (fls_regpart f)"
+
+definition%important eval_fls :: "complex fls \<Rightarrow> complex \<Rightarrow> complex" where
+  "eval_fls F z = eval_fps (fls_base_factor_to_fps F) z * z powi fls_subdegree F"
+
+definition\<^marker>\<open>tag important\<close>
+  has_laurent_expansion :: "(complex \<Rightarrow> complex) \<Rightarrow> complex fls \<Rightarrow> bool"
+  (infixl "has'_laurent'_expansion" 60)
+  where "(f has_laurent_expansion F) \<longleftrightarrow>
+            fls_conv_radius F > 0 \<and> eventually (\<lambda>z. eval_fls F z = f z) (at 0)"
+
+lemma has_laurent_expansion_schematicI:
+  "f has_laurent_expansion F \<Longrightarrow> F = G \<Longrightarrow> f has_laurent_expansion G"
+  by simp
+
+lemma has_laurent_expansion_cong:
+  assumes "eventually (\<lambda>x. f x = g x) (at 0)" "F = G"
+  shows   "(f has_laurent_expansion F) \<longleftrightarrow> (g has_laurent_expansion G)"
+proof -
+  have "eventually (\<lambda>z. eval_fls F z = g z) (at 0)"
+    if "eventually (\<lambda>z. eval_fls F z = f z) (at 0)" "eventually (\<lambda>x. f x = g x) (at 0)" for f g
+    using that by eventually_elim auto
+  from this[of f g] this[of g f] show ?thesis
+    using assms by (auto simp: eq_commute has_laurent_expansion_def)
+qed
+
+lemma has_laurent_expansion_cong':
+  assumes "eventually (\<lambda>x. f x = g x) (at z)" "F = G" "z = z'"
+  shows   "((\<lambda>x. f (z + x)) has_laurent_expansion F) \<longleftrightarrow> ((\<lambda>x. g (z' + x)) has_laurent_expansion G)"
+  by (intro has_laurent_expansion_cong)
+     (use assms in \<open>auto simp: at_to_0' eventually_filtermap add_ac\<close>)
+
+lemma fls_conv_radius_altdef:
+  "fls_conv_radius F = fps_conv_radius (fls_base_factor_to_fps F)"
+proof -
+  have "conv_radius (\<lambda>n. fls_nth F (int n)) = conv_radius (\<lambda>n. fls_nth F (int n + fls_subdegree F))"
+  proof (cases "fls_subdegree F \<ge> 0")
+    case True
+    hence "conv_radius (\<lambda>n. fls_nth F (int n + fls_subdegree F)) =
+           conv_radius (\<lambda>n. fls_nth F (int (n + nat (fls_subdegree F))))"
+      by auto
+    thus ?thesis
+      by (subst (asm) conv_radius_shift) auto
+  next
+    case False
+    hence "conv_radius (\<lambda>n. fls_nth F (int n)) =
+           conv_radius (\<lambda>n. fls_nth F (fls_subdegree F + int (n + nat (-fls_subdegree F))))"
+      by auto
+    thus ?thesis
+      by (subst (asm) conv_radius_shift) (auto simp: add_ac)
+  qed
+  thus ?thesis
+    by (simp add: fls_conv_radius_def fps_conv_radius_def)
+qed
+
+lemma eval_fps_of_nat [simp]: "eval_fps (of_nat n) z = of_nat n"
+  and eval_fps_of_int [simp]: "eval_fps (of_int m) z = of_int m"
+  by (simp_all flip: fps_of_nat fps_of_int)
+
+lemma fls_subdegree_numeral [simp]: "fls_subdegree (numeral n) = 0"
+  by (metis fls_subdegree_of_nat of_nat_numeral)
+
+lemma fls_regpart_numeral [simp]: "fls_regpart (numeral n) = numeral n"
+  by (metis fls_regpart_of_nat of_nat_numeral)
+
+lemma fps_conv_radius_of_nat [simp]: "fps_conv_radius (of_nat n) = \<infinity>"
+  and fps_conv_radius_of_int [simp]: "fps_conv_radius (of_int m) = \<infinity>"
+  by (simp_all flip: fps_of_nat fps_of_int)
+
+lemma fps_conv_radius_fls_regpart: "fps_conv_radius (fls_regpart F) = fls_conv_radius F"
+  by (simp add: fls_conv_radius_def)
+
+lemma fls_conv_radius_0 [simp]: "fls_conv_radius 0 = \<infinity>"
+  and fls_conv_radius_1 [simp]: "fls_conv_radius 1 = \<infinity>"
+  and fls_conv_radius_const [simp]: "fls_conv_radius (fls_const c) = \<infinity>"
+  and fls_conv_radius_numeral [simp]: "fls_conv_radius (numeral num) = \<infinity>"
+  and fls_conv_radius_of_nat [simp]: "fls_conv_radius (of_nat n) = \<infinity>"
+  and fls_conv_radius_of_int [simp]: "fls_conv_radius (of_int m) = \<infinity>"
+  and fls_conv_radius_X [simp]: "fls_conv_radius fls_X = \<infinity>"
+  and fls_conv_radius_X_inv [simp]: "fls_conv_radius fls_X_inv = \<infinity>"
+  and fls_conv_radius_X_intpow [simp]: "fls_conv_radius (fls_X_intpow m) = \<infinity>"
+  by (simp_all add: fls_conv_radius_def fls_X_intpow_regpart)
+
+lemma fls_conv_radius_shift [simp]: "fls_conv_radius (fls_shift n F) = fls_conv_radius F"
+  unfolding fls_conv_radius_altdef by (subst fls_base_factor_to_fps_shift) (rule refl)
+
+lemma fls_conv_radius_fps_to_fls [simp]: "fls_conv_radius (fps_to_fls F) = fps_conv_radius F"
+  by (simp add: fls_conv_radius_def)
+
+lemma fls_conv_radius_deriv [simp]: "fls_conv_radius (fls_deriv F) \<ge> fls_conv_radius F"
+proof -
+  have "fls_conv_radius (fls_deriv F) = fps_conv_radius (fls_regpart (fls_deriv F))"
+    by (simp add: fls_conv_radius_def)
+  also have "fls_regpart (fls_deriv F) = fps_deriv (fls_regpart F)"
+    by (intro fps_ext) (auto simp: add_ac)
+  also have "fps_conv_radius \<dots> \<ge> fls_conv_radius F"
+    by (simp add: fls_conv_radius_def fps_conv_radius_deriv)
+  finally show ?thesis .
+qed
+
+lemma fls_conv_radius_uminus [simp]: "fls_conv_radius (-F) = fls_conv_radius F"
+  by (simp add: fls_conv_radius_def)
+
+lemma fls_conv_radius_add: "fls_conv_radius (F + G) \<ge> min (fls_conv_radius F) (fls_conv_radius G)"
+  by (simp add: fls_conv_radius_def fps_conv_radius_add)
+
+lemma fls_conv_radius_diff: "fls_conv_radius (F - G) \<ge> min (fls_conv_radius F) (fls_conv_radius G)"
+  by (simp add: fls_conv_radius_def fps_conv_radius_diff)
+
+lemma fls_conv_radius_mult: "fls_conv_radius (F * G) \<ge> min (fls_conv_radius F) (fls_conv_radius G)"
+proof (cases "F = 0 \<or> G = 0")
+  case False
+  hence [simp]: "F \<noteq> 0" "G \<noteq> 0"
+    by auto
+  have "fls_conv_radius (F * G) = fps_conv_radius (fls_regpart (fls_shift (fls_subdegree F + fls_subdegree G) (F * G)))"
+    by (simp add: fls_conv_radius_altdef)
+  also have "fls_regpart (fls_shift (fls_subdegree F + fls_subdegree G) (F * G)) =
+             fls_base_factor_to_fps F * fls_base_factor_to_fps G"
+    by (simp add: fls_times_def)
+  also have "fps_conv_radius \<dots> \<ge> min (fls_conv_radius F) (fls_conv_radius G)"
+    unfolding fls_conv_radius_altdef by (rule fps_conv_radius_mult)
+  finally show ?thesis .
+qed auto
+
+lemma fps_conv_radius_add_ge:
+  "fps_conv_radius F \<ge> r \<Longrightarrow> fps_conv_radius G \<ge> r \<Longrightarrow> fps_conv_radius (F + G) \<ge> r"
+  using fps_conv_radius_add[of F G] by (simp add: min_def split: if_splits)
+
+lemma fps_conv_radius_diff_ge:
+  "fps_conv_radius F \<ge> r \<Longrightarrow> fps_conv_radius G \<ge> r \<Longrightarrow> fps_conv_radius (F - G) \<ge> r"
+  using fps_conv_radius_diff[of F G] by (simp add: min_def split: if_splits)
+
+lemma fps_conv_radius_mult_ge:
+  "fps_conv_radius F \<ge> r \<Longrightarrow> fps_conv_radius G \<ge> r \<Longrightarrow> fps_conv_radius (F * G) \<ge> r"
+  using fps_conv_radius_mult[of F G] by (simp add: min_def split: if_splits)
+
+lemma fls_conv_radius_add_ge:
+  "fls_conv_radius F \<ge> r \<Longrightarrow> fls_conv_radius G \<ge> r \<Longrightarrow> fls_conv_radius (F + G) \<ge> r"
+  using fls_conv_radius_add[of F G] by (simp add: min_def split: if_splits)
+
+lemma fls_conv_radius_diff_ge:
+  "fls_conv_radius F \<ge> r \<Longrightarrow> fls_conv_radius G \<ge> r \<Longrightarrow> fls_conv_radius (F - G) \<ge> r"
+  using fls_conv_radius_diff[of F G] by (simp add: min_def split: if_splits)
+
+lemma fls_conv_radius_mult_ge:
+  "fls_conv_radius F \<ge> r \<Longrightarrow> fls_conv_radius G \<ge> r \<Longrightarrow> fls_conv_radius (F * G) \<ge> r"
+  using fls_conv_radius_mult[of F G] by (simp add: min_def split: if_splits)
+
+lemma fls_conv_radius_power: "fls_conv_radius (F ^ n) \<ge> fls_conv_radius F"
+  by (induction n) (auto intro!: fls_conv_radius_mult_ge)
+
+lemma eval_fls_0 [simp]: "eval_fls 0 z = 0"
+  and eval_fls_1 [simp]: "eval_fls 1 z = 1"
+  and eval_fls_const [simp]: "eval_fls (fls_const c) z = c"
+  and eval_fls_numeral [simp]: "eval_fls (numeral num) z = numeral num"
+  and eval_fls_of_nat [simp]: "eval_fls (of_nat n) z = of_nat n"
+  and eval_fls_of_int [simp]: "eval_fls (of_int m) z = of_int m"
+  and eval_fls_X [simp]: "eval_fls fls_X z = z"
+  and eval_fls_X_intpow [simp]: "eval_fls (fls_X_intpow m) z = z powi m"
+  by (simp_all add: eval_fls_def)
+
+lemma eval_fls_at_0: "eval_fls F 0 = (if fls_subdegree F \<ge> 0 then fls_nth F 0 else 0)"
+  by (cases "fls_subdegree F = 0")
+     (simp_all add: eval_fls_def fls_regpart_def eval_fps_at_0)
+
+lemma eval_fps_to_fls:
+  assumes "norm z < fps_conv_radius F"
+  shows   "eval_fls (fps_to_fls F) z = eval_fps F z"
+proof (cases "F = 0")
+  case [simp]: False
+  have "eval_fps F z = eval_fps (unit_factor F * normalize F) z"
+    by (metis unit_factor_mult_normalize)
+  also have "\<dots> = eval_fps (unit_factor F * fps_X ^ subdegree F) z"
+    by simp
+  also have "\<dots> = eval_fps (unit_factor F) z * z ^ subdegree F"
+    using assms by (subst eval_fps_mult) auto
+  also have "\<dots> = eval_fls (fps_to_fls F) z"
+    unfolding eval_fls_def fls_base_factor_to_fps_to_fls fls_subdegree_fls_to_fps
+              power_int_of_nat ..
+  finally show ?thesis ..
+qed auto
+
+lemma eval_fls_shift:
+  assumes [simp]: "z \<noteq> 0"
+  shows   "eval_fls (fls_shift n F) z = eval_fls F z * z powi -n"
+proof (cases "F = 0")
+  case [simp]: False
+  show ?thesis
+  unfolding eval_fls_def
+  by (subst fls_base_factor_to_fps_shift, subst fls_shift_subdegree[OF \<open>F \<noteq> 0\<close>], subst power_int_diff)
+     (auto simp: power_int_minus divide_simps)
+qed auto
+
+lemma eval_fls_add:
+  assumes "ereal (norm z) < fls_conv_radius F" "ereal (norm z) < fls_conv_radius G" "z \<noteq> 0"
+  shows   "eval_fls (F + G) z = eval_fls F z + eval_fls G z"
+  using assms
+proof (induction "fls_subdegree F" "fls_subdegree G" arbitrary: F G rule: linorder_wlog)
+  case (sym F G)
+  show ?case
+    using sym(1)[of G F] sym(2-) by (simp add: add_ac)
+next
+  case (le F G)
+  show ?case
+  proof (cases "F = 0 \<or> G = 0")
+    case False
+    hence [simp]: "F \<noteq> 0" "G \<noteq> 0"
+      by auto
+    note [simp] = \<open>z \<noteq> 0\<close>
+    define F' G' where "F' = fls_base_factor_to_fps F" "G' = fls_base_factor_to_fps G"
+    define m n where "m = fls_subdegree F" "n = fls_subdegree G"
+    have "m \<le> n"
+      using le by (auto simp: m_n_def)
+    have conv1: "ereal (cmod z) < fps_conv_radius F'" "ereal (cmod z) < fps_conv_radius G'"
+      using assms le by (simp_all add: F'_G'_def fls_conv_radius_altdef)
+    have conv2: "ereal (cmod z) < fps_conv_radius (G' * fps_X ^ nat (n - m))"
+      using conv1 by (intro less_le_trans[OF _ fps_conv_radius_mult]) auto
+    have conv3: "ereal (cmod z) < fps_conv_radius (F' + G' * fps_X ^ nat (n - m))"
+      using conv1 conv2 by (intro less_le_trans[OF _ fps_conv_radius_add]) auto
+
+    have "eval_fls F z + eval_fls G z = eval_fps F' z * z powi m + eval_fps G' z * z powi n"
+      unfolding eval_fls_def m_n_def[symmetric] F'_G'_def[symmetric]
+      by (simp add: power_int_add algebra_simps)
+    also have "\<dots> = (eval_fps F' z + eval_fps G' z * z powi (n - m)) * z powi m"
+      by (simp add: algebra_simps power_int_diff)
+    also have "eval_fps G' z * z powi (n - m) = eval_fps (G' * fps_X ^ nat (n - m)) z"
+      using assms \<open>m \<le> n\<close> conv1 by (subst eval_fps_mult) (auto simp: power_int_def)
+    also have "eval_fps F' z + \<dots> = eval_fps (F' + G' * fps_X ^ nat (n - m)) z"
+      using conv1 conv2 by (subst eval_fps_add) auto
+    also have "\<dots> = eval_fls (fps_to_fls (F' + G' * fps_X ^ nat (n - m))) z"
+      using conv3 by (subst eval_fps_to_fls) auto
+    also have "\<dots> * z powi m = eval_fls (fls_shift (-m) (fps_to_fls (F' + G' * fps_X ^ nat (n - m)))) z"
+      by (subst eval_fls_shift) auto
+    also have "fls_shift (-m) (fps_to_fls (F' + G' * fps_X ^ nat (n - m))) = F + G"
+      using \<open>m \<le> n\<close>
+      by (simp add: fls_times_fps_to_fls fps_to_fls_power fls_X_power_conv_shift_1
+                    fls_shifted_times_simps F'_G'_def m_n_def)
+    finally show ?thesis ..
+  qed auto
+qed
+
+lemma eval_fls_minus:
+  assumes "ereal (norm z) < fls_conv_radius F"
+  shows   "eval_fls (-F) z = -eval_fls F z"
+  using assms by (simp add: eval_fls_def eval_fps_minus fls_conv_radius_altdef)
+
+lemma eval_fls_diff:
+  assumes "ereal (norm z) < fls_conv_radius F" "ereal (norm z) < fls_conv_radius G"
+     and [simp]: "z \<noteq> 0"
+  shows   "eval_fls (F - G) z = eval_fls F z - eval_fls G z"
+proof -
+  have "eval_fls (F + (-G)) z = eval_fls F z - eval_fls G z"
+    using assms by (subst eval_fls_add) (auto simp: eval_fls_minus)
+  thus ?thesis
+    by simp
+qed
+
+lemma eval_fls_mult:
+  assumes "ereal (norm z) < fls_conv_radius F" "ereal (norm z) < fls_conv_radius G" "z \<noteq> 0"
+  shows   "eval_fls (F * G) z = eval_fls F z * eval_fls G z"
+proof (cases "F = 0 \<or> G = 0")
+  case False
+  hence [simp]: "F \<noteq> 0" "G \<noteq> 0"
+    by auto
+  note [simp] = \<open>z \<noteq> 0\<close>
+  define F' G' where "F' = fls_base_factor_to_fps F" "G' = fls_base_factor_to_fps G"
+  define m n where "m = fls_subdegree F" "n = fls_subdegree G"
+  have "eval_fls F z * eval_fls G z = (eval_fps F' z * eval_fps G' z) * z powi (m + n)"
+    unfolding eval_fls_def m_n_def[symmetric] F'_G'_def[symmetric]
+    by (simp add: power_int_add algebra_simps)
+  also have "\<dots> = eval_fps (F' * G') z * z powi (m + n)"
+    using assms by (subst eval_fps_mult) (auto simp: F'_G'_def fls_conv_radius_altdef)
+  also have "\<dots> = eval_fls (F * G) z"
+    by (simp add: eval_fls_def F'_G'_def m_n_def) (simp add: fls_times_def)
+  finally show ?thesis ..
+qed auto
+
+lemma eval_fls_power:
+  assumes "ereal (norm z) < fls_conv_radius F" "z \<noteq> 0"
+  shows   "eval_fls (F ^ n) z = eval_fls F z ^ n"
+proof (induction n)
+  case (Suc n)
+  have "eval_fls (F ^ Suc n) z = eval_fls (F * F ^ n) z"
+    by simp
+  also have "\<dots> = eval_fls F z * eval_fls (F ^ n) z"
+    using assms by (subst eval_fls_mult) (auto intro!: less_le_trans[OF _ fls_conv_radius_power])
+  finally show ?case
+    using Suc by simp
+qed auto
+
+lemma norm_summable_fls:
+  "norm z < fls_conv_radius f \<Longrightarrow> summable (\<lambda>n. norm (fls_nth f n * z ^ n))"
+  using norm_summable_fps[of z "fls_regpart f"] by (simp add: fls_conv_radius_def)
+
+lemma norm_summable_fls':
+  "norm z < fls_conv_radius f \<Longrightarrow> summable (\<lambda>n. norm (fls_nth f (n + fls_subdegree f) * z ^ n))"
+  using norm_summable_fps[of z "fls_base_factor_to_fps f"] by (simp add: fls_conv_radius_altdef)
+
+lemma summable_fls:
+  "norm z < fls_conv_radius f \<Longrightarrow> summable (\<lambda>n. fls_nth f n * z ^ n)"
+  by (rule summable_norm_cancel[OF norm_summable_fls])
+
+theorem sums_eval_fls:
+  fixes f
+  defines "n \<equiv> fls_subdegree f"
+  assumes "norm z < fls_conv_radius f" and "z \<noteq> 0 \<or> n \<ge> 0"
+  shows   "(\<lambda>k. fls_nth f (int k + n) * z powi (int k + n)) sums eval_fls f z"
+proof (cases "z = 0")
+  case [simp]: False
+  have "(\<lambda>k. fps_nth (fls_base_factor_to_fps f) k * z ^ k * z powi n) sums
+          (eval_fps (fls_base_factor_to_fps f) z * z powi n)"
+    using assms(2) by (intro sums_eval_fps sums_mult2) (auto simp: fls_conv_radius_altdef)
+  thus ?thesis
+    by (simp add: power_int_add n_def eval_fls_def mult_ac)
+next
+  case [simp]: True
+  with assms have "n \<ge> 0"
+    by auto
+  have "(\<lambda>k. fls_nth f (int k + n) * z powi (int k + n)) sums
+          (\<Sum>k\<in>(if n \<le> 0 then {nat (-n)} else {}). fls_nth f (int k + n) * z powi (int k + n))"
+    by (intro sums_finite) (auto split: if_splits)
+  also have "\<dots> = eval_fls f z"
+    using \<open>n \<ge> 0\<close> by (auto simp: eval_fls_at_0 n_def not_le)
+  finally show ?thesis .
+qed
+
+lemma holomorphic_on_eval_fls:
+  fixes f
+  defines "n \<equiv> fls_subdegree f"
+  assumes "A \<subseteq> eball 0 (fls_conv_radius f) - (if n \<ge> 0 then {} else {0})"
+  shows   "eval_fls f holomorphic_on A"
+proof (cases "n \<ge> 0")
+  case True
+  have "eval_fls f = (\<lambda>z. eval_fps (fls_base_factor_to_fps f) z * z ^ nat n)"
+    using True by (simp add: fun_eq_iff eval_fls_def power_int_def n_def)
+  moreover have "\<dots> holomorphic_on A"
+    using True assms(2) by (intro holomorphic_intros) (auto simp: fls_conv_radius_altdef)
+  ultimately show ?thesis
+    by simp
+next
+  case False
+  show ?thesis using assms
+    unfolding eval_fls_def by (intro holomorphic_intros) (auto simp: fls_conv_radius_altdef)
+qed
+
+lemma holomorphic_on_eval_fls' [holomorphic_intros]:
+  assumes "g holomorphic_on A"
+  assumes "g ` A \<subseteq> eball 0 (fls_conv_radius f) - (if fls_subdegree f \<ge> 0 then {} else {0})"
+  shows   "(\<lambda>x. eval_fls f (g x)) holomorphic_on A"
+proof -
+  have "eval_fls f \<circ> g holomorphic_on A"
+    by (intro holomorphic_on_compose[OF assms(1) holomorphic_on_eval_fls]) (use assms in auto)
+  thus ?thesis
+    by (simp add: o_def)
+qed
+
+lemma continuous_on_eval_fls:
+  fixes f
+  defines "n \<equiv> fls_subdegree f"
+  assumes "A \<subseteq> eball 0 (fls_conv_radius f) - (if n \<ge> 0 then {} else {0})"
+  shows   "continuous_on A (eval_fls f)"
+  by (intro holomorphic_on_imp_continuous_on holomorphic_on_eval_fls)
+     (use assms in auto)
+
+lemma continuous_on_eval_fls' [continuous_intros]:
+  fixes f
+  defines "n \<equiv> fls_subdegree f"
+  assumes "g ` A \<subseteq> eball 0 (fls_conv_radius f) - (if n \<ge> 0 then {} else {0})"
+  assumes "continuous_on A g"
+  shows   "continuous_on A (\<lambda>x. eval_fls f (g x))"
+  using assms(3)
+  by (intro continuous_on_compose2[OF continuous_on_eval_fls _ assms(2)])
+     (auto simp: n_def)
+
+lemmas has_field_derivative_eval_fps' [derivative_intros] =
+  DERIV_chain2[OF has_field_derivative_eval_fps]
+
+lemma fps_deriv_fls_regpart: "fps_deriv (fls_regpart F) = fls_regpart (fls_deriv F)"
+  by (intro fps_ext) (auto simp: add_ac)
+
+(* TODO: generalise for nonneg subdegree *)
+lemma has_field_derivative_eval_fls:
+  assumes "z \<in> eball 0 (fls_conv_radius f) - {0}"
+  shows   "(eval_fls f has_field_derivative eval_fls (fls_deriv f) z) (at z within A)"
+proof -
+  define g where "g = fls_base_factor_to_fps f"
+  define n where "n = fls_subdegree f"
+  have [simp]: "fps_conv_radius g = fls_conv_radius f"
+    by (simp add: fls_conv_radius_altdef g_def)
+  have conv1: "fps_conv_radius (fps_deriv g * fps_X) \<ge> fls_conv_radius f"
+    by (intro fps_conv_radius_mult_ge order.trans[OF _ fps_conv_radius_deriv]) auto
+  have conv2: "fps_conv_radius (of_int n * g) \<ge> fls_conv_radius f"
+    by (intro fps_conv_radius_mult_ge) auto
+  have conv3: "fps_conv_radius (fps_deriv g * fps_X + of_int n * g) \<ge> fls_conv_radius f"
+    by (intro fps_conv_radius_add_ge conv1 conv2)
+
+  have [simp]: "fps_conv_radius g = fls_conv_radius f"
+    by (simp add: g_def fls_conv_radius_altdef)
+  have "((\<lambda>z. eval_fps g z * z powi fls_subdegree f) has_field_derivative
+          (eval_fps (fps_deriv g) z * z powi n + of_int n * z powi (n - 1) * eval_fps g z))
+          (at z within A)"
+    using assms by (auto intro!: derivative_eq_intros simp: n_def)
+  also have "(\<lambda>z. eval_fps g z * z powi fls_subdegree f) = eval_fls f"
+    by (simp add: eval_fls_def g_def fun_eq_iff)
+  also have "eval_fps (fps_deriv g) z * z powi n + of_int n * z powi (n - 1) * eval_fps g z =
+             (z * eval_fps (fps_deriv g) z + of_int n * eval_fps g z) * z powi (n - 1)"
+    using assms by (auto simp: power_int_diff field_simps)
+  also have "(z * eval_fps (fps_deriv g) z + of_int n * eval_fps g z) =
+             eval_fps (fps_deriv g * fps_X + of_int n * g) z"
+    using conv1 conv2 assms fps_conv_radius_deriv[of g]
+    by (subst eval_fps_add) (auto simp: eval_fps_mult)
+  also have "\<dots> = eval_fls (fps_to_fls (fps_deriv g * fps_X + of_int n * g)) z"
+    using conv3 assms by (subst eval_fps_to_fls) auto
+  also have "\<dots> * z powi (n - 1) = eval_fls (fls_shift (1 - n) (fps_to_fls (fps_deriv g * fps_X + of_int n * g))) z"
+    using assms by (subst eval_fls_shift) auto
+  also have "fls_shift (1 - n) (fps_to_fls (fps_deriv g * fps_X + of_int n * g)) = fls_deriv f"
+    by (intro fls_eqI) (auto simp: g_def n_def algebra_simps eq_commute[of _ "fls_subdegree f"])
+  finally show ?thesis .
+qed
+
+lemma eval_fls_deriv:
+  assumes "z \<in> eball 0 (fls_conv_radius F) - {0}"
+  shows   "eval_fls (fls_deriv F) z = deriv (eval_fls F) z"
+  by (rule sym, rule DERIV_imp_deriv, rule has_field_derivative_eval_fls, rule assms)
+
+lemma analytic_on_eval_fls:
+  assumes "A \<subseteq> eball 0 (fls_conv_radius f) - (if fls_subdegree f \<ge> 0 then {} else {0})"
+  shows   "eval_fls f analytic_on A"
+proof (rule analytic_on_subset [OF _ assms])
+  show "eval_fls f analytic_on eball 0 (fls_conv_radius f) - (if fls_subdegree f \<ge> 0 then {} else {0})"
+    using holomorphic_on_eval_fls[OF order.refl]
+    by (subst analytic_on_open) auto
+qed
+
+lemma analytic_on_eval_fls' [analytic_intros]:
+  assumes "g analytic_on A"
+  assumes "g ` A \<subseteq> eball 0 (fls_conv_radius f) - (if fls_subdegree f \<ge> 0 then {} else {0})"
+  shows   "(\<lambda>x. eval_fls f (g x)) analytic_on A"
+proof -
+  have "eval_fls f \<circ> g analytic_on A"
+    by (intro analytic_on_compose[OF assms(1) analytic_on_eval_fls]) (use assms in auto)
+  thus ?thesis
+    by (simp add: o_def)
+qed
+
+lemma continuous_eval_fls [continuous_intros]:
+  assumes "z \<in> eball 0 (fls_conv_radius F) - (if fls_subdegree F \<ge> 0 then {} else {0})"
+  shows   "continuous (at z within A) (eval_fls F)"
+proof -
+  have "isCont (eval_fls F) z"
+    using continuous_on_eval_fls[OF order.refl] assms
+    by (subst (asm) continuous_on_eq_continuous_at) auto
+  thus ?thesis
+    using continuous_at_imp_continuous_at_within by blast
+qed
+
+
+
+
+named_theorems laurent_expansion_intros
+
+lemma has_laurent_expansion_imp_asymp_equiv_0:
+  assumes F: "f has_laurent_expansion F"
+  defines "n \<equiv> fls_subdegree F"
+  shows   "f \<sim>[at 0] (\<lambda>z. fls_nth F n * z powi n)"
+proof (cases "F = 0")
+  case True
+  thus ?thesis using assms
+    by (auto simp: has_laurent_expansion_def)
+next
+  case [simp]: False
+  define G where "G = fls_base_factor_to_fps F"
+  have "fls_conv_radius F > 0"
+    using F by (auto simp: has_laurent_expansion_def)
+  hence "isCont (eval_fps G) 0"
+    by (intro continuous_intros) (auto simp: G_def fps_conv_radius_fls_regpart zero_ereal_def)
+  hence lim: "eval_fps G \<midarrow>0\<rightarrow> eval_fps G 0"
+    by (meson isContD)
+  have [simp]: "fps_nth G 0 \<noteq> 0"
+    by (auto simp: G_def)
+
+  have "f \<sim>[at 0] eval_fls F"
+    using F by (intro asymp_equiv_refl_ev) (auto simp: has_laurent_expansion_def eq_commute)
+  also have "\<dots> = (\<lambda>z. eval_fps G z * z powi n)"
+    by (intro ext) (simp_all add: eval_fls_def G_def n_def)
+  also have "\<dots> \<sim>[at 0] (\<lambda>z. fps_nth G 0 * z powi n)" using lim
+    by (intro asymp_equiv_intros tendsto_imp_asymp_equiv_const) (auto simp: eval_fps_at_0)
+  also have "fps_nth G 0 = fls_nth F n"
+    by (simp add: G_def n_def)
+  finally show ?thesis
+    by simp
+qed
+
+lemma has_laurent_expansion_imp_asymp_equiv:
+  assumes F: "(\<lambda>w. f (z + w)) has_laurent_expansion F"
+  defines "n \<equiv> fls_subdegree F"
+  shows   "f \<sim>[at z] (\<lambda>w. fls_nth F n * (w - z) powi n)"
+  using has_laurent_expansion_imp_asymp_equiv_0[OF assms(1)] unfolding n_def
+  by (simp add: at_to_0[of z] asymp_equiv_filtermap_iff add_ac)
+
+
+lemmas [tendsto_intros del] = tendsto_power_int
+
+lemma has_laurent_expansion_imp_tendsto_0:
+  assumes F: "f has_laurent_expansion F" and "fls_subdegree F \<ge> 0"
+  shows   "f \<midarrow>0\<rightarrow> fls_nth F 0"
+proof (rule asymp_equiv_tendsto_transfer)
+  show "(\<lambda>z. fls_nth F (fls_subdegree F) * z powi fls_subdegree F) \<sim>[at 0] f"
+    by (rule asymp_equiv_symI, rule has_laurent_expansion_imp_asymp_equiv_0) fact
+  show "(\<lambda>z. fls_nth F (fls_subdegree F) * z powi fls_subdegree F) \<midarrow>0\<rightarrow> fls_nth F 0"
+    by (rule tendsto_eq_intros refl | use assms(2) in simp)+
+       (use assms(2) in \<open>auto simp: power_int_0_left_If\<close>)
+qed
+
+lemma has_laurent_expansion_imp_tendsto:
+  assumes F: "(\<lambda>w. f (z + w)) has_laurent_expansion F" and "fls_subdegree F \<ge> 0"
+  shows   "f \<midarrow>z\<rightarrow> fls_nth F 0"
+  using has_laurent_expansion_imp_tendsto_0[OF assms]
+  by (simp add: at_to_0[of z] filterlim_filtermap add_ac)
+
+lemma has_laurent_expansion_imp_filterlim_infinity_0:
+  assumes F: "f has_laurent_expansion F" and "fls_subdegree F < 0"
+  shows   "filterlim f at_infinity (at 0)"
+proof (rule asymp_equiv_at_infinity_transfer)
+  have [simp]: "F \<noteq> 0"
+    using assms(2) by auto
+  show "(\<lambda>z. fls_nth F (fls_subdegree F) * z powi fls_subdegree F) \<sim>[at 0] f"
+    by (rule asymp_equiv_symI, rule has_laurent_expansion_imp_asymp_equiv_0) fact
+  show "filterlim (\<lambda>z. fls_nth F (fls_subdegree F) * z powi fls_subdegree F) at_infinity (at 0)"
+    by (rule tendsto_mult_filterlim_at_infinity tendsto_const
+             filterlim_power_int_neg_at_infinity | use assms(2) in simp)+
+       (auto simp: eventually_at_filter)
+qed
+
+lemma has_laurent_expansion_imp_neg_fls_subdegree:
+  assumes F: "f has_laurent_expansion F"
+    and infy:"filterlim f at_infinity (at 0)"
+  shows   "fls_subdegree F < 0"
+proof (rule ccontr)
+  assume asm:"\<not> fls_subdegree F < 0"
+  define ff where "ff=(\<lambda>z. fls_nth F (fls_subdegree F)
+                              * z powi fls_subdegree F)"
+
+  have "(ff \<longlongrightarrow> (if fls_subdegree F =0 then fls_nth F 0 else 0)) (at 0)"
+    using asm unfolding ff_def
+    by (auto intro!: tendsto_eq_intros)
+  moreover have "filterlim ff at_infinity (at 0)"
+  proof (rule asymp_equiv_at_infinity_transfer)
+    show "f \<sim>[at 0] ff" unfolding ff_def
+      using has_laurent_expansion_imp_asymp_equiv_0[OF F] unfolding ff_def .
+    show "filterlim f at_infinity (at 0)" by fact
+  qed
+  ultimately show False
+    using not_tendsto_and_filterlim_at_infinity[of "at (0::complex)"] by auto
+qed
+
+lemma has_laurent_expansion_imp_filterlim_infinity:
+  assumes F: "(\<lambda>w. f (z + w)) has_laurent_expansion F" and "fls_subdegree F < 0"
+  shows   "filterlim f at_infinity (at z)"
+  using has_laurent_expansion_imp_filterlim_infinity_0[OF assms]
+  by (simp add: at_to_0[of z] filterlim_filtermap add_ac)
+
+lemma has_laurent_expansion_imp_is_pole_0:
+  assumes F: "f has_laurent_expansion F" and "fls_subdegree F < 0"
+  shows   "is_pole f 0"
+  using has_laurent_expansion_imp_filterlim_infinity_0[OF assms]
+  by (simp add: is_pole_def)
+
+lemma is_pole_0_imp_neg_fls_subdegree:
+  assumes F: "f has_laurent_expansion F" and "is_pole f 0"
+  shows   "fls_subdegree F < 0"
+  using F assms(2) has_laurent_expansion_imp_neg_fls_subdegree is_pole_def
+  by blast
+
+lemma has_laurent_expansion_imp_is_pole:
+  assumes F: "(\<lambda>x. f (z + x)) has_laurent_expansion F" and "fls_subdegree F < 0"
+  shows   "is_pole f z"
+  using has_laurent_expansion_imp_is_pole_0[OF assms]
+  by (simp add: is_pole_shift_0')
+
+lemma is_pole_imp_neg_fls_subdegree:
+  assumes F: "(\<lambda>x. f (z + x)) has_laurent_expansion F" and "is_pole f z"
+  shows   "fls_subdegree F < 0"
+  apply (rule is_pole_0_imp_neg_fls_subdegree[OF F])
+  using assms(2) is_pole_shift_0 by blast
+
+lemma is_pole_fls_subdegree_iff:
+  assumes "(\<lambda>x. f (z + x)) has_laurent_expansion F"
+  shows "is_pole f z \<longleftrightarrow> fls_subdegree F < 0"
+  using assms is_pole_imp_neg_fls_subdegree has_laurent_expansion_imp_is_pole
+  by auto
+
+lemma
+  assumes "f has_laurent_expansion F"
+  shows   has_laurent_expansion_isolated_0: "isolated_singularity_at f 0"
+    and   has_laurent_expansion_not_essential_0: "not_essential f 0"
+proof -
+  from assms have "eventually (\<lambda>z. eval_fls F z = f z) (at 0)"
+    by (auto simp: has_laurent_expansion_def)
+  then obtain r where r: "r > 0" "\<And>z. z \<in> ball 0 r - {0} \<Longrightarrow> eval_fls F z = f z"
+    by (auto simp: eventually_at_filter ball_def eventually_nhds_metric)
+
+  have "fls_conv_radius F > 0"
+    using assms by (auto simp: has_laurent_expansion_def)
+  then obtain R :: real where R: "R > 0" "R \<le> min r (fls_conv_radius F)"
+    using \<open>r > 0\<close> by (metis dual_order.strict_implies_order ereal_dense2 ereal_less(2) min_def)
+
+  have "eval_fls F holomorphic_on ball 0 R - {0}"
+    using r R by (intro holomorphic_intros ball_eball_mono Diff_mono)  (auto simp: ereal_le_less)
+  also have "?this \<longleftrightarrow> f holomorphic_on ball 0 R - {0}"
+    using r R by (intro holomorphic_cong) auto
+  also have "\<dots> \<longleftrightarrow> f analytic_on ball 0 R - {0}"
+    by (subst analytic_on_open) auto
+  finally show "isolated_singularity_at f 0"
+    unfolding isolated_singularity_at_def using \<open>R > 0\<close> by blast
+
+  show "not_essential f 0"
+  proof (cases "fls_subdegree F \<ge> 0")
+    case True
+    hence "f \<midarrow>0\<rightarrow> fls_nth F 0"
+      by (intro has_laurent_expansion_imp_tendsto_0[OF assms])
+    thus ?thesis
+      by (auto simp: not_essential_def)
+  next
+    case False
+    hence "is_pole f 0"
+      by (intro has_laurent_expansion_imp_is_pole_0[OF assms]) auto
+    thus ?thesis
+      by (auto simp: not_essential_def)
+  qed
+qed
+
+lemma
+  assumes "(\<lambda>w. f (z + w)) has_laurent_expansion F"
+  shows   has_laurent_expansion_isolated: "isolated_singularity_at f z"
+    and   has_laurent_expansion_not_essential: "not_essential f z"
+  using has_laurent_expansion_isolated_0[OF assms] has_laurent_expansion_not_essential_0[OF assms]
+  by (simp_all add: isolated_singularity_at_shift_0 not_essential_shift_0)
+
+lemma has_laurent_expansion_fps:
+  assumes "f has_fps_expansion F"
+  shows   "f has_laurent_expansion fps_to_fls F"
+proof -
+  from assms have radius: "0 < fps_conv_radius F" and eval: "\<forall>\<^sub>F z in nhds 0. eval_fps F z = f z"
+    by (auto simp: has_fps_expansion_def)
+  from eval have eval': "\<forall>\<^sub>F z in at 0. eval_fps F z = f z"
+    using eventually_at_filter eventually_mono by fastforce
+  moreover have "eventually (\<lambda>z. z \<in> eball 0 (fps_conv_radius F) - {0}) (at 0)"
+    using radius by (intro eventually_at_in_open) (auto simp: zero_ereal_def)
+  ultimately have "eventually (\<lambda>z. eval_fls (fps_to_fls F) z = f z) (at 0)"
+    by eventually_elim (auto simp: eval_fps_to_fls)
+  thus ?thesis using radius
+    by (auto simp: has_laurent_expansion_def)
+qed
+
+lemma has_laurent_expansion_const [simp, intro, laurent_expansion_intros]:
+  "(\<lambda>_. c) has_laurent_expansion fls_const c"
+  by (auto simp: has_laurent_expansion_def)
+
+lemma has_laurent_expansion_0 [simp, intro, laurent_expansion_intros]:
+  "(\<lambda>_. 0) has_laurent_expansion 0"
+  by (auto simp: has_laurent_expansion_def)
+
+lemma has_fps_expansion_0_iff: "f has_fps_expansion 0 \<longleftrightarrow> eventually (\<lambda>z. f z = 0) (nhds 0)"
+  by (auto simp: has_fps_expansion_def)
+
+lemma has_laurent_expansion_1 [simp, intro, laurent_expansion_intros]:
+  "(\<lambda>_. 1) has_laurent_expansion 1"
+  by (auto simp: has_laurent_expansion_def)
+
+lemma has_laurent_expansion_numeral [simp, intro, laurent_expansion_intros]:
+  "(\<lambda>_. numeral n) has_laurent_expansion numeral n"
+  by (auto simp: has_laurent_expansion_def)
+
+lemma has_laurent_expansion_fps_X_power [laurent_expansion_intros]:
+  "(\<lambda>x. x ^ n) has_laurent_expansion (fls_X_intpow n)"
+  by (auto simp: has_laurent_expansion_def)
+
+lemma has_laurent_expansion_fps_X_power_int [laurent_expansion_intros]:
+  "(\<lambda>x. x powi n) has_laurent_expansion (fls_X_intpow n)"
+  by (auto simp: has_laurent_expansion_def)
+
+lemma has_laurent_expansion_fps_X [laurent_expansion_intros]:
+  "(\<lambda>x. x) has_laurent_expansion fls_X"
+  by (auto simp: has_laurent_expansion_def)
+
+lemma has_laurent_expansion_cmult_left [laurent_expansion_intros]:
+  assumes "f has_laurent_expansion F"
+  shows   "(\<lambda>x. c * f x) has_laurent_expansion fls_const c * F"
+proof -
+  from assms have "eventually (\<lambda>z. z \<in> eball 0 (fls_conv_radius F) - {0}) (at 0)"
+    by (intro eventually_at_in_open) (auto simp: has_laurent_expansion_def zero_ereal_def)
+  moreover from assms have "eventually (\<lambda>z. eval_fls F z = f z) (at 0)"
+    by (auto simp: has_laurent_expansion_def)
+  ultimately have "eventually (\<lambda>z. eval_fls (fls_const c * F) z = c * f z) (at 0)"
+    by eventually_elim (simp_all add: eval_fls_mult)
+  with assms show ?thesis
+    by (auto simp: has_laurent_expansion_def intro!: less_le_trans[OF _ fls_conv_radius_mult])
+qed
+
+lemma has_laurent_expansion_cmult_right [laurent_expansion_intros]:
+  assumes "f has_laurent_expansion F"
+  shows   "(\<lambda>x. f x * c) has_laurent_expansion F * fls_const c"
+proof -
+  have "F * fls_const c = fls_const c * F"
+    by (intro fls_eqI) (auto simp: mult.commute)
+  with has_laurent_expansion_cmult_left [OF assms] show ?thesis
+    by (simp add: mult.commute)
+qed
+
+lemma has_fps_expansion_scaleR [fps_expansion_intros]:
+  fixes F :: "'a :: {banach, real_normed_div_algebra, comm_ring_1} fps"
+  shows "f has_fps_expansion F \<Longrightarrow> (\<lambda>x. c *\<^sub>R f x) has_fps_expansion fps_const (of_real c) * F"
+  unfolding scaleR_conv_of_real by (intro fps_expansion_intros)
+
+lemma has_laurent_expansion_scaleR [laurent_expansion_intros]:
+  "f has_laurent_expansion F \<Longrightarrow> (\<lambda>x. c *\<^sub>R f x) has_laurent_expansion fls_const (of_real c) * F"
+  unfolding scaleR_conv_of_real by (intro laurent_expansion_intros)
+
+lemma has_laurent_expansion_minus [laurent_expansion_intros]:
+  assumes "f has_laurent_expansion F"
+  shows   "(\<lambda>x. - f x) has_laurent_expansion -F"
+proof -
+  from assms have "eventually (\<lambda>x. x \<in> eball 0 (fls_conv_radius F) - {0}) (at 0)"
+    by (intro eventually_at_in_open) (auto simp: has_laurent_expansion_def zero_ereal_def)
+  moreover from assms have "eventually (\<lambda>x. eval_fls F x = f x) (at 0)"
+    by (auto simp: has_laurent_expansion_def)
+  ultimately have "eventually (\<lambda>x. eval_fls (-F) x = -f x) (at 0)"
+    by eventually_elim (auto simp: eval_fls_minus)
+  thus ?thesis using assms by (auto simp: has_laurent_expansion_def)
+qed
+
+lemma has_laurent_expansion_add [laurent_expansion_intros]:
+  assumes "f has_laurent_expansion F" "g has_laurent_expansion G"
+  shows   "(\<lambda>x. f x + g x) has_laurent_expansion F + G"
+proof -
+  from assms have "0 < min (fls_conv_radius F) (fls_conv_radius G)"
+    by (auto simp: has_laurent_expansion_def)
+  also have "\<dots> \<le> fls_conv_radius (F + G)"
+    by (rule fls_conv_radius_add)
+  finally have radius: "\<dots> > 0" .
+
+  from assms have "eventually (\<lambda>x. x \<in> eball 0 (fls_conv_radius F) - {0}) (at 0)"
+                  "eventually (\<lambda>x. x \<in> eball 0 (fls_conv_radius G) - {0}) (at 0)"
+    by (intro eventually_at_in_open; force simp: has_laurent_expansion_def zero_ereal_def)+
+  moreover have "eventually (\<lambda>x. eval_fls F x = f x) (at 0)"
+            and "eventually (\<lambda>x. eval_fls G x = g x) (at 0)"
+    using assms by (auto simp: has_laurent_expansion_def)
+  ultimately have "eventually (\<lambda>x. eval_fls (F + G) x = f x + g x) (at 0)"
+    by eventually_elim (auto simp: eval_fls_add)
+  with radius show ?thesis by (auto simp: has_laurent_expansion_def)
+qed
+
+lemma has_laurent_expansion_diff [laurent_expansion_intros]:
+  assumes "f has_laurent_expansion F" "g has_laurent_expansion G"
+  shows   "(\<lambda>x. f x - g x) has_laurent_expansion F - G"
+  using has_laurent_expansion_add[of f F "\<lambda>x. - g x" "-G"] assms
+  by (simp add: has_laurent_expansion_minus)
+
+lemma has_laurent_expansion_mult [laurent_expansion_intros]:
+  assumes "f has_laurent_expansion F" "g has_laurent_expansion G"
+  shows   "(\<lambda>x. f x * g x) has_laurent_expansion F * G"
+proof -
+  from assms have "0 < min (fls_conv_radius F) (fls_conv_radius G)"
+    by (auto simp: has_laurent_expansion_def)
+  also have "\<dots> \<le> fls_conv_radius (F * G)"
+    by (rule fls_conv_radius_mult)
+  finally have radius: "\<dots> > 0" .
+
+  from assms have "eventually (\<lambda>x. x \<in> eball 0 (fls_conv_radius F) - {0}) (at 0)"
+                  "eventually (\<lambda>x. x \<in> eball 0 (fls_conv_radius G) - {0}) (at 0)"
+    by (intro eventually_at_in_open; force simp: has_laurent_expansion_def zero_ereal_def)+
+  moreover have "eventually (\<lambda>x. eval_fls F x = f x) (at 0)"
+            and "eventually (\<lambda>x. eval_fls G x = g x) (at 0)"
+    using assms by (auto simp: has_laurent_expansion_def)
+  ultimately have "eventually (\<lambda>x. eval_fls (F * G) x = f x * g x) (at 0)"
+    by eventually_elim (auto simp: eval_fls_mult)
+  with radius show ?thesis by (auto simp: has_laurent_expansion_def)
+qed
+
+lemma has_fps_expansion_power [fps_expansion_intros]:
+  fixes F :: "'a :: {banach, real_normed_div_algebra, comm_ring_1} fps"
+  shows "f has_fps_expansion F \<Longrightarrow> (\<lambda>x. f x ^ m) has_fps_expansion F ^ m"
+  by (induction m) (auto intro!: fps_expansion_intros)
+
+lemma has_laurent_expansion_power [laurent_expansion_intros]:
+  assumes "f has_laurent_expansion F"
+  shows   "(\<lambda>x. f x ^ n) has_laurent_expansion F ^ n"
+  by (induction n) (auto intro!: laurent_expansion_intros assms)
+
+lemma has_laurent_expansion_sum [laurent_expansion_intros]:
+  assumes "\<And>x. x \<in> I \<Longrightarrow> f x has_laurent_expansion F x"
+  shows   "(\<lambda>y. \<Sum>x\<in>I. f x y) has_laurent_expansion (\<Sum>x\<in>I. F x)"
+  using assms by (induction I rule: infinite_finite_induct) (auto intro!: laurent_expansion_intros)
+
+lemma has_laurent_expansion_prod [laurent_expansion_intros]:
+  assumes "\<And>x. x \<in> I \<Longrightarrow> f x has_laurent_expansion F x"
+  shows   "(\<lambda>y. \<Prod>x\<in>I. f x y) has_laurent_expansion (\<Prod>x\<in>I. F x)"
+  using assms by (induction I rule: infinite_finite_induct) (auto intro!: laurent_expansion_intros)
+
+lemma has_laurent_expansion_deriv [laurent_expansion_intros]:
+  assumes "f has_laurent_expansion F"
+  shows   "deriv f has_laurent_expansion fls_deriv F"
+proof -
+  have "eventually (\<lambda>z. z \<in> eball 0 (fls_conv_radius F) - {0}) (at 0)"
+    using assms by (intro eventually_at_in_open)
+                   (auto simp: has_laurent_expansion_def zero_ereal_def)
+  moreover from assms have "eventually (\<lambda>z. eval_fls F z = f z) (at 0)"
+    by (auto simp: has_laurent_expansion_def)
+  then obtain s where "open s" "0 \<in> s" and s: "\<And>w. w \<in> s - {0} \<Longrightarrow> eval_fls F w = f w"
+    by (auto simp: eventually_nhds eventually_at_filter)
+  hence "eventually (\<lambda>w. w \<in> s - {0}) (at 0)"
+    by (intro eventually_at_in_open) auto
+  ultimately have "eventually (\<lambda>z. eval_fls (fls_deriv F) z = deriv f z) (at 0)"
+  proof eventually_elim
+    case (elim z)
+    hence "eval_fls (fls_deriv F) z = deriv (eval_fls F) z"
+      by (simp add: eval_fls_deriv)
+    also have "eventually (\<lambda>w. w \<in> s - {0}) (nhds z)"
+      using elim and \<open>open s\<close> by (intro eventually_nhds_in_open) auto
+    hence "eventually (\<lambda>w. eval_fls F w = f w) (nhds z)"
+      by eventually_elim (use s in auto)
+    hence "deriv (eval_fls F) z = deriv f z"
+      by (intro deriv_cong_ev refl)
+    finally show ?case .
+  qed
+  with assms show ?thesis
+    by (auto simp: has_laurent_expansion_def intro!: less_le_trans[OF _ fls_conv_radius_deriv])
+qed
+
+lemma has_laurent_expansion_shift [laurent_expansion_intros]:
+  assumes "f has_laurent_expansion F"
+  shows   "(\<lambda>x. f x * x powi n) has_laurent_expansion (fls_shift (-n) F)"
+proof -
+  have "eventually (\<lambda>x. x \<in> eball 0 (fls_conv_radius F) - {0}) (at 0)"
+    using assms by (intro eventually_at_in_open) (auto simp: has_laurent_expansion_def zero_ereal_def)
+  moreover have "eventually (\<lambda>x. eval_fls F x = f x) (at 0)"
+    using assms by (auto simp: has_laurent_expansion_def)
+  ultimately have "eventually (\<lambda>x. eval_fls (fls_shift (-n) F) x = f x * x powi n) (at 0)"
+    by eventually_elim (auto simp: eval_fls_shift assms)
+  with assms show ?thesis by (auto simp: has_laurent_expansion_def)
+qed
+
+lemma has_laurent_expansion_shift' [laurent_expansion_intros]:
+  assumes "f has_laurent_expansion F"
+  shows   "(\<lambda>x. f x * x powi (-n)) has_laurent_expansion (fls_shift n F)"
+  using has_laurent_expansion_shift[OF assms, of "-n"] by simp
+
+
+lemma has_laurent_expansion_deriv':
+  assumes "f has_laurent_expansion F"
+  assumes "open A" "0 \<in> A" "\<And>x. x \<in> A - {0} \<Longrightarrow> (f has_field_derivative f' x) (at x)"
+  shows   "f' has_laurent_expansion fls_deriv F"
+proof -
+  have "deriv f has_laurent_expansion fls_deriv F"
+    by (intro laurent_expansion_intros assms)
+  also have "?this \<longleftrightarrow> ?thesis"
+  proof (intro has_laurent_expansion_cong refl)
+    have "eventually (\<lambda>z. z \<in> A - {0}) (at 0)"
+      by (intro eventually_at_in_open assms)
+    thus "eventually (\<lambda>z. deriv f z = f' z) (at 0)"
+      by eventually_elim (auto intro!: DERIV_imp_deriv assms)
+  qed
+  finally show ?thesis .
+qed
+
+definition laurent_expansion :: "(complex \<Rightarrow> complex) \<Rightarrow> complex \<Rightarrow> complex fls" where
+  "laurent_expansion f z =
+     (if eventually (\<lambda>z. f z = 0) (at z) then 0
+      else fls_shift (-zorder f z) (fps_to_fls (fps_expansion (zor_poly f z) z)))"
+
+lemma laurent_expansion_cong:
+  assumes "eventually (\<lambda>w. f w = g w) (at z)" "z = z'"
+  shows   "laurent_expansion f z = laurent_expansion g z'"
+  unfolding laurent_expansion_def
+  using zor_poly_cong[OF assms(1,2)] zorder_cong[OF assms] assms
+  by (intro if_cong refl) (auto elim: eventually_elim2)
+
+theorem not_essential_has_laurent_expansion_0:
+  assumes "isolated_singularity_at f 0" "not_essential f 0"
+  shows   "f has_laurent_expansion laurent_expansion f 0"
+proof (cases "\<exists>\<^sub>F w in at 0. f w \<noteq> 0")
+  case False
+  have "(\<lambda>_. 0) has_laurent_expansion 0"
+    by simp
+  also have "?this \<longleftrightarrow> f has_laurent_expansion 0"
+    using False by (intro has_laurent_expansion_cong) (auto simp: frequently_def)
+  finally show ?thesis
+    using False by (simp add: laurent_expansion_def frequently_def)
+next
+  case True
+  define n where "n = zorder f 0"
+  obtain r where r: "zor_poly f 0 0 \<noteq> 0" "zor_poly f 0 holomorphic_on cball 0 r" "r > 0"
+                    "\<forall>w\<in>cball 0 r - {0}. f w = zor_poly f 0 w * w powr of_int n \<and>
+                                         zor_poly f 0 w \<noteq> 0"
+    using zorder_exist[OF assms True] unfolding n_def by auto
+  have holo: "zor_poly f 0 holomorphic_on ball 0 r"
+    by (rule holomorphic_on_subset[OF r(2)]) auto
+
+  define F where "F = fps_expansion (zor_poly f 0) 0"
+  have F: "zor_poly f 0 has_fps_expansion F"
+    unfolding F_def by (rule has_fps_expansion_fps_expansion[OF _ _ holo]) (use \<open>r > 0\<close> in auto)
+  have "(\<lambda>z. zor_poly f 0 z * z powi n) has_laurent_expansion fls_shift (-n) (fps_to_fls F)"
+    by (intro laurent_expansion_intros has_laurent_expansion_fps[OF F])
+  also have "?this \<longleftrightarrow> f has_laurent_expansion fls_shift (-n) (fps_to_fls F)"
+    by (intro has_laurent_expansion_cong refl eventually_mono[OF eventually_at_in_open[of "ball 0 r"]])
+       (use r in \<open>auto simp: complex_powr_of_int\<close>)
+  finally show ?thesis using True
+    by (simp add: laurent_expansion_def F_def n_def frequently_def)
+qed
+
+lemma not_essential_has_laurent_expansion:
+  assumes "isolated_singularity_at f z" "not_essential f z"
+  shows   "(\<lambda>x. f (z + x)) has_laurent_expansion laurent_expansion f z"
+proof -
+  from assms(1) have iso:"isolated_singularity_at (\<lambda>x. f (z + x)) 0"
+    by (simp add: isolated_singularity_at_shift_0)
+  moreover from assms(2) have ness:"not_essential (\<lambda>x. f (z + x)) 0"
+    by (simp add: not_essential_shift_0)
+  ultimately have "(\<lambda>x. f (z + x)) has_laurent_expansion laurent_expansion (\<lambda>x. f (z + x)) 0"
+    by (rule not_essential_has_laurent_expansion_0)
+
+  also have "\<dots> = laurent_expansion f z"
+  proof (cases "\<exists>\<^sub>F w in at z. f w \<noteq> 0")
+    case False
+    then have "\<forall>\<^sub>F w in at z. f w = 0" using not_frequently by force
+    then have "laurent_expansion (\<lambda>x. f (z + x)) 0 = 0"
+      by (smt (verit, best) add.commute eventually_at_to_0 eventually_mono
+          laurent_expansion_def)
+    moreover have "laurent_expansion f z = 0"
+      using \<open>\<forall>\<^sub>F w in at z. f w = 0\<close> unfolding laurent_expansion_def by auto
+    ultimately show ?thesis by auto
+  next
+    case True
+    define df where "df=zor_poly (\<lambda>x. f (z + x)) 0"
+    define g where "g=(\<lambda>u. u-z)"
+
+    have "fps_expansion df 0
+        =  fps_expansion (df o g) z"
+    proof -
+      have "\<exists>\<^sub>F w in at 0. f (z + w) \<noteq> 0" using True
+        by (smt (verit, best) add.commute eventually_at_to_0
+            eventually_mono not_frequently)
+      from zorder_exist[OF iso ness this,folded df_def]
+      obtain r where "r>0" and df_holo:"df holomorphic_on cball 0 r" and "df 0 \<noteq> 0"
+          "\<forall>w\<in>cball 0 r - {0}.
+             f (z + w) = df w * w powr of_int (zorder (\<lambda>w. f (z + w)) 0) \<and>
+             df w \<noteq> 0"
+        by auto
+      then have df_nz:"\<forall>w\<in>ball 0 r. df w\<noteq>0" by auto
+
+      have "(deriv ^^ n) df 0 =  (deriv ^^ n) (df \<circ> g) z" for n
+        unfolding comp_def g_def
+      proof (subst higher_deriv_compose_linear'[where u=1 and c="-z",simplified])
+        show "df holomorphic_on ball 0 r"
+          using df_holo by auto
+        show "open (ball z r)" "open (ball 0 r)" "z \<in> ball z r"
+          using \<open>r>0\<close> by auto
+        show " \<And>w. w \<in> ball z r \<Longrightarrow> w - z \<in> ball 0 r"
+          by (simp add: dist_norm)
+      qed auto
+      then show ?thesis
+        unfolding fps_expansion_def by auto
+    qed
+    also have "... = fps_expansion (zor_poly f z) z"
+    proof (rule fps_expansion_cong)
+      have "\<forall>\<^sub>F w in nhds z. zor_poly f z w
+                = zor_poly (\<lambda>u. f (z + u)) 0 (w - z)"
+        apply (rule zor_poly_shift)
+        using True assms by auto
+      then show "\<forall>\<^sub>F w in nhds z. (df \<circ> g) w = zor_poly f z w"
+        unfolding df_def g_def comp_def
+        by (auto elim:eventually_mono)
+    qed
+    finally show ?thesis unfolding df_def
+      by (auto simp: laurent_expansion_def at_to_0[of z]
+          eventually_filtermap add_ac zorder_shift')
+  qed
+  finally show ?thesis .
+qed
+
+lemma has_fps_expansion_to_laurent:
+  "f has_fps_expansion F \<longleftrightarrow> f has_laurent_expansion fps_to_fls F \<and> f 0 = fps_nth F 0"
+proof safe
+  assume *: "f has_laurent_expansion fps_to_fls F" "f 0 = fps_nth F 0"
+  have "eventually (\<lambda>z. z \<in> eball 0 (fps_conv_radius F)) (nhds 0)"
+    using * by (intro eventually_nhds_in_open) (auto simp: has_laurent_expansion_def zero_ereal_def)
+  moreover have "eventually (\<lambda>z. z \<noteq> 0 \<longrightarrow> eval_fls (fps_to_fls F) z = f z) (nhds 0)"
+    using * by (auto simp: has_laurent_expansion_def eventually_at_filter)
+  ultimately have "eventually (\<lambda>z. f z = eval_fps F z) (nhds 0)"
+    by eventually_elim
+       (auto simp: has_laurent_expansion_def eventually_at_filter eval_fps_at_0 eval_fps_to_fls *(2))
+  thus "f has_fps_expansion F"
+    using * by (auto simp: has_fps_expansion_def has_laurent_expansion_def eq_commute)
+next
+  assume "f has_fps_expansion F"
+  thus "f 0 = fps_nth F 0"
+    by (metis eval_fps_at_0 has_fps_expansion_imp_holomorphic)
+qed (auto intro: has_laurent_expansion_fps)
+
+lemma eval_fps_fls_base_factor [simp]:
+  assumes "z \<noteq> 0"
+  shows   "eval_fps (fls_base_factor_to_fps F) z = eval_fls F z * z powi -fls_subdegree F"
+  using assms unfolding eval_fls_def by (simp add: power_int_minus field_simps)
+
+lemma has_fps_expansion_imp_analytic_0:
+  assumes "f has_fps_expansion F"
+  shows   "f analytic_on {0}"
+  by (meson analytic_at_two assms has_fps_expansion_imp_holomorphic)
+
+lemma has_fps_expansion_imp_analytic:
+  assumes "(\<lambda>x. f (z + x)) has_fps_expansion F"
+  shows   "f analytic_on {z}"
+proof -
+  have "(\<lambda>x. f (z + x)) analytic_on {0}"
+    by (rule has_fps_expansion_imp_analytic_0) fact
+  hence "(\<lambda>x. f (z + x)) \<circ> (\<lambda>x. x - z) analytic_on {z}"
+    by (intro analytic_on_compose_gen analytic_intros) auto
+  thus ?thesis
+    by (simp add: o_def)
+qed
+
+lemma is_pole_cong_asymp_equiv:
+  assumes "f \<sim>[at z] g" "z = z'"
+  shows   "is_pole f z = is_pole g z'"
+  using asymp_equiv_at_infinity_transfer[OF assms(1)]
+        asymp_equiv_at_infinity_transfer[OF asymp_equiv_symI[OF assms(1)]] assms(2)
+  unfolding is_pole_def by auto
+
+lemma not_is_pole_const [simp]: "\<not>is_pole (\<lambda>_::'a::perfect_space. c :: complex) z"
+  using not_tendsto_and_filterlim_at_infinity[of "at z" "\<lambda>_::'a. c" c] by (auto simp: is_pole_def)
+
+lemma has_laurent_expansion_imp_is_pole_iff:
+  assumes F: "(\<lambda>x. f (z + x)) has_laurent_expansion F"
+  shows   "is_pole f z \<longleftrightarrow> fls_subdegree F < 0"
+proof
+  assume pole: "is_pole f z"
+  have [simp]: "F \<noteq> 0"
+  proof
+    assume "F = 0"
+    hence "is_pole f z \<longleftrightarrow> is_pole (\<lambda>_. 0 :: complex) z" using assms
+      by (intro is_pole_cong)
+         (auto simp: has_laurent_expansion_def at_to_0[of z] eventually_filtermap add_ac)
+    with pole show False
+      by simp
+  qed
+
+  note pole
+  also have "is_pole f z \<longleftrightarrow>
+             is_pole (\<lambda>w. fls_nth F (fls_subdegree F) * (w - z) powi fls_subdegree F) z"
+    using has_laurent_expansion_imp_asymp_equiv[OF F] by (intro is_pole_cong_asymp_equiv refl)
+  also have "\<dots> \<longleftrightarrow> is_pole (\<lambda>w. (w - z) powi fls_subdegree F) z"
+    by simp
+  finally have pole': \<dots> .
+
+  have False if "fls_subdegree F \<ge> 0"
+  proof -
+    have "(\<lambda>w. (w - z) powi fls_subdegree F) holomorphic_on UNIV"
+      using that by (intro holomorphic_intros) auto
+    hence "\<not>is_pole (\<lambda>w. (w - z) powi fls_subdegree F) z"
+      by (meson UNIV_I not_is_pole_holomorphic open_UNIV)
+    with pole' show False
+      by simp
+  qed
+  thus "fls_subdegree F < 0"
+    by force
+qed (use has_laurent_expansion_imp_is_pole[OF assms] in auto)
+
+lemma analytic_at_imp_has_fps_expansion_0:
+  assumes "f analytic_on {0}"
+  shows   "f has_fps_expansion fps_expansion f 0"
+  using assms has_fps_expansion_fps_expansion analytic_at by fast
+
+lemma deriv_shift_0: "deriv f z = deriv (f \<circ> (\<lambda>x. z + x)) 0"
+proof -
+  have *: "(f \<circ> (+) z has_field_derivative D) (at z')"
+    if "(f has_field_derivative D) (at (z + z'))" for D z z' and f :: "'a \<Rightarrow> 'a"
+  proof -
+    have "(f \<circ> (+) z has_field_derivative D * 1) (at z')"
+      by (rule DERIV_chain that derivative_eq_intros refl)+ auto
+    thus ?thesis by simp
+  qed
+  have "(\<lambda>D. (f has_field_derivative D) (at z)) = (\<lambda> D. (f \<circ> (+) z has_field_derivative D) (at 0))"
+    using *[of f _ z 0] *[of "f \<circ> (+) z" _ "-z" z] by (intro ext iffI) (auto simp: o_def)
+  thus ?thesis
+    by (simp add: deriv_def)
+qed
+
+lemma deriv_shift_0': "NO_MATCH 0 z \<Longrightarrow> deriv f z = deriv (f \<circ> (\<lambda>x. z + x)) 0"
+  by (rule deriv_shift_0)
+
+lemma higher_deriv_shift_0: "(deriv ^^ n) f z = (deriv ^^ n) (f \<circ> (\<lambda>x. z + x)) 0"
+proof (induction n arbitrary: f)
+  case (Suc n)
+  have "(deriv ^^ Suc n) f z = (deriv ^^ n) (deriv f) z"
+    by (subst funpow_Suc_right) auto
+  also have "\<dots> = (deriv ^^ n) (\<lambda>x. deriv f (z + x)) 0"
+    by (subst Suc) (auto simp: o_def)
+  also have "\<dots> = (deriv ^^ n) (\<lambda>x. deriv (\<lambda>xa. f (z + x + xa)) 0) 0"
+    by (subst deriv_shift_0) (auto simp: o_def)
+  also have "(\<lambda>x. deriv (\<lambda>xa. f (z + x + xa)) 0) = deriv (\<lambda>x. f (z + x))"
+    by (rule ext) (simp add: deriv_shift_0' o_def add_ac)
+  also have "(deriv ^^ n) \<dots> 0 = (deriv ^^ Suc n) (f \<circ> (\<lambda>x. z + x)) 0"
+    by (subst funpow_Suc_right) (auto simp: o_def)
+  finally show ?case .
+qed auto
+
+lemma higher_deriv_shift_0': "NO_MATCH 0 z \<Longrightarrow> (deriv ^^ n) f z = (deriv ^^ n) (f \<circ> (\<lambda>x. z + x)) 0"
+  by (rule higher_deriv_shift_0)
+
+lemma analytic_at_imp_has_fps_expansion:
+  assumes "f analytic_on {z}"
+  shows   "(\<lambda>x. f (z + x)) has_fps_expansion fps_expansion f z"
+proof -
+  have "f \<circ> (\<lambda>x. z + x) analytic_on {0}"
+    by (intro analytic_on_compose_gen[OF _ assms] analytic_intros) auto
+  hence "(f \<circ> (\<lambda>x. z + x)) has_fps_expansion fps_expansion (f \<circ> (\<lambda>x. z + x)) 0"
+    unfolding o_def by (intro analytic_at_imp_has_fps_expansion_0) auto
+  also have "\<dots> = fps_expansion f z"
+    by (simp add: fps_expansion_def higher_deriv_shift_0')
+  finally show ?thesis by (simp add: add_ac)
+qed
+
+lemma has_laurent_expansion_zorder_0:
+  assumes "f has_laurent_expansion F" "F \<noteq> 0"
+  shows   "zorder f 0 = fls_subdegree F"
+proof -
+  define G where "G = fls_base_factor_to_fps F"
+  from assms obtain A where A: "0 \<in> A" "open A" "\<And>x. x \<in> A - {0} \<Longrightarrow> eval_fls F x = f x"
+    unfolding has_laurent_expansion_def eventually_at_filter eventually_nhds
+    by blast
+
+  show ?thesis
+  proof (rule zorder_eqI)
+    show "open (A \<inter> eball 0 (fls_conv_radius F))" "0 \<in> A \<inter>  eball 0 (fls_conv_radius F)"
+      using assms A by (auto simp: has_laurent_expansion_def zero_ereal_def)
+    show "eval_fps G holomorphic_on A \<inter> eball 0 (fls_conv_radius F)"
+      by (intro holomorphic_intros) (auto simp: fls_conv_radius_altdef G_def)
+    show "eval_fps G 0 \<noteq> 0" using \<open>F \<noteq> 0\<close>
+      by (auto simp: eval_fps_at_0 G_def)
+  next
+    fix w :: complex assume "w \<in> A \<inter> eball 0 (fls_conv_radius F)" "w \<noteq> 0"
+    thus "f w = eval_fps G w * (w - 0) powr of_int (fls_subdegree F)"
+      using A unfolding G_def
+      by (subst eval_fps_fls_base_factor)
+         (auto simp: complex_powr_of_int power_int_minus field_simps)
+  qed
+qed
+
+lemma has_laurent_expansion_zorder:
+  assumes "(\<lambda>w. f (z + w)) has_laurent_expansion F" "F \<noteq> 0"
+  shows   "zorder f z = fls_subdegree F"
+  using has_laurent_expansion_zorder_0[OF assms] by (simp add: zorder_shift' add_ac)
+
+lemma has_fps_expansion_zorder_0:
+  assumes "f has_fps_expansion F" "F \<noteq> 0"
+  shows   "zorder f 0 = int (subdegree F)"
+  using assms has_laurent_expansion_zorder_0[of f "fps_to_fls F"]
+  by (auto simp: has_fps_expansion_to_laurent fls_subdegree_fls_to_fps)
+
+lemma has_fps_expansion_zorder:
+  assumes "(\<lambda>w. f (z + w)) has_fps_expansion F" "F \<noteq> 0"
+  shows   "zorder f z = int (subdegree F)"
+  using has_fps_expansion_zorder_0[OF assms]
+  by (simp add: zorder_shift' add_ac)
+
+lemma has_fps_expansion_fls_base_factor_to_fps:
+  assumes "f has_laurent_expansion F"
+  defines "n \<equiv> fls_subdegree F"
+  defines "c \<equiv> fps_nth (fls_base_factor_to_fps F) 0"
+  shows   "(\<lambda>z. if z = 0 then c else f z * z powi -n) has_fps_expansion fls_base_factor_to_fps F"
+proof -
+  have "(\<lambda>z. f z * z powi -n) has_laurent_expansion fls_shift (-(-n)) F"
+    by (intro laurent_expansion_intros assms)
+  also have "fls_shift (-(-n)) F = fps_to_fls (fls_base_factor_to_fps F)"
+    by (simp add: n_def fls_shift_nonneg_subdegree)
+  also have "(\<lambda>z. f z * z powi - n) has_laurent_expansion fps_to_fls (fls_base_factor_to_fps F) \<longleftrightarrow>
+             (\<lambda>z. if z = 0 then c else f z * z powi -n) has_laurent_expansion fps_to_fls (fls_base_factor_to_fps F)"
+    by (intro has_laurent_expansion_cong) (auto simp: eventually_at_filter)
+  also have "\<dots> \<longleftrightarrow> (\<lambda>z. if z = 0 then c else f z * z powi -n) has_fps_expansion fls_base_factor_to_fps F"
+    by (subst has_fps_expansion_to_laurent) (auto simp: c_def)
+  finally show ?thesis .
+qed
+
+lemma zero_has_laurent_expansion_imp_eq_0:
+  assumes "(\<lambda>_. 0) has_laurent_expansion F"
+  shows   "F = 0"
+proof -
+  have "at (0 :: complex) \<noteq> bot"
+    by auto
+  moreover have "(\<lambda>z. if z = 0 then fls_nth F (fls_subdegree F) else 0) has_fps_expansion
+          fls_base_factor_to_fps F" (is "?f has_fps_expansion _")
+    using has_fps_expansion_fls_base_factor_to_fps[OF assms] by (simp cong: if_cong)
+  hence "isCont ?f 0"
+    using has_fps_expansion_imp_continuous by blast
+  hence "?f \<midarrow>0\<rightarrow> fls_nth F (fls_subdegree F)"
+    by (auto simp: isCont_def)
+  moreover have "?f \<midarrow>0\<rightarrow> 0 \<longleftrightarrow> (\<lambda>_::complex. 0 :: complex) \<midarrow>0\<rightarrow> 0"
+    by (intro filterlim_cong) (auto simp: eventually_at_filter)
+  hence "?f \<midarrow>0\<rightarrow> 0"
+    by simp
+  ultimately have "fls_nth F (fls_subdegree F) = 0"
+    by (rule tendsto_unique)
+  thus ?thesis
+    by (meson nth_fls_subdegree_nonzero)
+qed
+
+lemma has_laurent_expansion_unique:
+  assumes "f has_laurent_expansion F" "f has_laurent_expansion G"
+  shows   "F = G"
+proof -
+  from assms have "(\<lambda>x. f x - f x) has_laurent_expansion F - G"
+    by (intro laurent_expansion_intros)
+  hence "(\<lambda>_. 0) has_laurent_expansion F - G"
+    by simp
+  hence "F - G = 0"
+    by (rule zero_has_laurent_expansion_imp_eq_0)
+  thus ?thesis
+    by simp
+qed
+
+lemma laurent_expansion_eqI:
+  assumes "(\<lambda>x. f (z + x)) has_laurent_expansion F"
+  shows   "laurent_expansion f z = F"
+  using assms has_laurent_expansion_isolated has_laurent_expansion_not_essential
+        has_laurent_expansion_unique not_essential_has_laurent_expansion by blast
+
+lemma laurent_expansion_0_eqI:
+  assumes "f has_laurent_expansion F"
+  shows   "laurent_expansion f 0 = F"
+  using assms laurent_expansion_eqI[of f 0] by simp
+
+lemma has_laurent_expansion_nonzero_imp_eventually_nonzero:
+  assumes "f has_laurent_expansion F" "F \<noteq> 0"
+  shows   "eventually (\<lambda>x. f x \<noteq> 0) (at 0)"
+proof (rule ccontr)
+  assume "\<not>eventually (\<lambda>x. f x \<noteq> 0) (at 0)"
+  with assms have "eventually (\<lambda>x. f x = 0) (at 0)"
+    by (intro not_essential_frequently_0_imp_eventually_0 has_laurent_expansion_isolated
+              has_laurent_expansion_not_essential)
+       (auto simp: frequently_def)
+  hence "(f has_laurent_expansion 0) \<longleftrightarrow> ((\<lambda>_. 0) has_laurent_expansion 0)"
+    by (intro has_laurent_expansion_cong) auto
+  hence "f has_laurent_expansion 0"
+    by simp
+  with assms(1) have "F = 0"
+    using has_laurent_expansion_unique by blast
+  with \<open>F \<noteq> 0\<close> show False
+    by contradiction
+qed
+
+lemma has_laurent_expansion_eventually_nonzero_iff':
+  assumes "f has_laurent_expansion F"
+  shows   "eventually (\<lambda>x. f x \<noteq> 0) (at 0) \<longleftrightarrow> F \<noteq> 0 "
+proof
+  assume "\<forall>\<^sub>F x in at 0. f x \<noteq> 0"
+  moreover have "\<not> (\<forall>\<^sub>F x in at 0. f x \<noteq> 0)" if "F=0"
+  proof -
+    have "\<forall>\<^sub>F x in at 0. f x = 0"
+      using assms that unfolding has_laurent_expansion_def by simp
+    then show ?thesis unfolding not_eventually
+      by (auto elim:eventually_frequentlyE)
+  qed
+  ultimately show "F \<noteq> 0" by auto
+qed (simp add:has_laurent_expansion_nonzero_imp_eventually_nonzero[OF assms])
+
+lemma has_laurent_expansion_eventually_nonzero_iff:
+  assumes "(\<lambda>w. f (z+w)) has_laurent_expansion F"
+  shows   "eventually (\<lambda>x. f x \<noteq> 0) (at z)  \<longleftrightarrow> F \<noteq> 0"
+  apply (subst eventually_at_to_0)
+  apply (rule has_laurent_expansion_eventually_nonzero_iff')
+  using assms by (simp add:add.commute)
+
+lemma has_laurent_expansion_inverse [laurent_expansion_intros]:
+  assumes "f has_laurent_expansion F"
+  shows   "(\<lambda>x. inverse (f x)) has_laurent_expansion inverse F"
+proof (cases "F = 0")
+  case True
+  thus ?thesis using assms
+    by (auto simp: has_laurent_expansion_def)
+next
+  case False
+  define G where "G = laurent_expansion (\<lambda>x. inverse (f x)) 0"
+  from False have ev: "eventually (\<lambda>z. f z \<noteq> 0) (at 0)"
+    by (intro has_laurent_expansion_nonzero_imp_eventually_nonzero[OF assms])
+
+  have *: "(\<lambda>x. inverse (f x)) has_laurent_expansion G" unfolding G_def
+    by (intro not_essential_has_laurent_expansion_0 isolated_singularity_at_inverse not_essential_inverse
+              has_laurent_expansion_isolated_0[OF assms] has_laurent_expansion_not_essential_0[OF assms])
+  have "(\<lambda>x. f x * inverse (f x)) has_laurent_expansion F * G"
+    by (intro laurent_expansion_intros assms *)
+  also have "?this \<longleftrightarrow> (\<lambda>x. 1) has_laurent_expansion F * G"
+    by (intro has_laurent_expansion_cong refl eventually_mono[OF ev]) auto
+  finally have "(\<lambda>_. 1) has_laurent_expansion F * G" .
+  moreover have "(\<lambda>_. 1) has_laurent_expansion 1"
+    by simp
+  ultimately have "F * G = 1"
+    using has_laurent_expansion_unique by blast
+  hence "G = inverse F"
+    using inverse_unique by blast
+  with * show ?thesis
+    by simp
+qed
+
+lemma has_laurent_expansion_power_int [laurent_expansion_intros]:
+  "f has_laurent_expansion F \<Longrightarrow> (\<lambda>x. f x powi n) has_laurent_expansion (F powi n)"
+  by (auto simp: power_int_def intro!: laurent_expansion_intros)
+
+
+lemma has_fps_expansion_0_analytic_continuation:
+  assumes "f has_fps_expansion 0" "f holomorphic_on A"
+  assumes "open A" "connected A" "0 \<in> A" "x \<in> A"
+  shows   "f x = 0"
+proof -
+  have "eventually (\<lambda>z. z \<in> A \<and> f z = 0) (nhds 0)" using assms
+    by (intro eventually_conj eventually_nhds_in_open) (auto simp: has_fps_expansion_def)
+  then obtain B where B: "open B" "0 \<in> B" "\<forall>z\<in>B. z \<in> A \<and> f z = 0"
+    unfolding eventually_nhds by blast
+  show ?thesis
+  proof (rule analytic_continuation_open[where f = f and g = "\<lambda>_. 0"])
+    show "B \<noteq> {}"
+      using \<open>open B\<close> B by auto
+    show "connected A"
+      using assms by auto
+  qed (use assms B in auto)
+qed
+
+lemma has_laurent_expansion_0_analytic_continuation:
+  assumes "f has_laurent_expansion 0" "f holomorphic_on A - {0}"
+  assumes "open A" "connected A" "0 \<in> A" "x \<in> A - {0}"
+  shows   "f x = 0"
+proof -
+  have "eventually (\<lambda>z. z \<in> A - {0} \<and> f z = 0) (at 0)" using assms
+    by (intro eventually_conj eventually_at_in_open) (auto simp: has_laurent_expansion_def)
+  then obtain B where B: "open B" "0 \<in> B" "\<forall>z\<in>B - {0}. z \<in> A - {0} \<and> f z = 0"
+    unfolding eventually_at_filter eventually_nhds by blast
+  show ?thesis
+  proof (rule analytic_continuation_open[where f = f and g = "\<lambda>_. 0"])
+    show "B - {0} \<noteq> {}"
+      using \<open>open B\<close> \<open>0 \<in> B\<close> by (metis insert_Diff not_open_singleton)
+    show "connected (A - {0})"
+      using assms by (intro connected_open_delete) auto
+  qed (use assms B in auto)
+qed
+
+lemma has_fps_expansion_cong:
+  assumes "eventually (\<lambda>x. f x = g x) (nhds 0)" "F = G"
+  shows   "f has_fps_expansion F \<longleftrightarrow> g has_fps_expansion G"
+  using assms(2) by (auto simp: has_fps_expansion_def elim!: eventually_elim2[OF assms(1)])
+
+lemma zor_poly_has_fps_expansion:
+  assumes "f has_laurent_expansion F" "F \<noteq> 0"
+  shows   "zor_poly f 0 has_fps_expansion fls_base_factor_to_fps F"
+proof -
+  note [simp] = \<open>F \<noteq> 0\<close>
+  have "eventually (\<lambda>z. f z \<noteq> 0) (at 0)"
+    by (rule has_laurent_expansion_nonzero_imp_eventually_nonzero[OF assms])
+  hence freq: "frequently (\<lambda>z. f z \<noteq> 0) (at 0)"
+    by (rule eventually_frequently[rotated]) auto
+
+  have *: "isolated_singularity_at f 0" "not_essential f 0"
+    using has_laurent_expansion_isolated_0[OF assms(1)] has_laurent_expansion_not_essential_0[OF assms(1)]
+    by auto
+
+  define G where "G = fls_base_factor_to_fps F"
+  define n where "n = zorder f 0"
+  have n_altdef: "n = fls_subdegree F"
+    using has_laurent_expansion_zorder_0 [OF assms(1)] by (simp add: n_def)
+  obtain r where r: "zor_poly f 0 0 \<noteq> 0" "zor_poly f 0 holomorphic_on cball 0 r" "r > 0"
+                    "\<forall>w\<in>cball 0 r - {0}. f w = zor_poly f 0 w * w powr of_int n \<and>
+                                         zor_poly f 0 w \<noteq> 0"
+    using zorder_exist[OF * freq] unfolding n_def by auto
+  obtain r' where r': "r' > 0" "\<forall>x\<in>ball 0 r'-{0}. eval_fls F x = f x"
+    using assms(1) unfolding has_laurent_expansion_def eventually_at_filter eventually_nhds_metric ball_def
+    by (auto simp: dist_commute)
+  have holo: "zor_poly f 0 holomorphic_on ball 0 r"
+    by (rule holomorphic_on_subset[OF r(2)]) auto
+
+  have "(\<lambda>z. if z = 0 then fps_nth G 0 else f z * z powi -n) has_fps_expansion G"
+    unfolding G_def n_altdef by (intro has_fps_expansion_fls_base_factor_to_fps assms)
+  also have "?this \<longleftrightarrow> zor_poly f 0 has_fps_expansion G"
+  proof (intro has_fps_expansion_cong)
+    have "eventually (\<lambda>z. z \<in> ball 0 (min r r')) (nhds 0)"
+      using \<open>r > 0\<close> \<open>r' > 0\<close> by (intro eventually_nhds_in_open) auto
+    thus "\<forall>\<^sub>F x in nhds 0. (if x = 0 then G $ 0 else f x * x powi - n) = zor_poly f 0 x"
+    proof eventually_elim
+      case (elim w)
+      have w: "w \<in> ball 0 r" "w \<in> ball 0 r'"
+        using elim by auto
+      show ?case
+      proof (cases "w = 0")
+        case False
+        hence "f w = zor_poly f 0 w * w powr of_int n"
+          using r w by auto
+        thus ?thesis using False
+          by (simp add: powr_minus complex_powr_of_int power_int_minus)
+      next
+        case [simp]: True
+        obtain R where R: "R > 0" "R \<le> r" "R \<le> r'" "R \<le> fls_conv_radius F"
+          using \<open>r > 0\<close> \<open>r' > 0\<close> assms(1) unfolding has_laurent_expansion_def
+          by (smt (verit, ccfv_SIG) ereal_dense2 ereal_less(2) less_ereal.simps(1) order.strict_implies_order order_trans)
+        have "eval_fps G 0 = zor_poly f 0 0"
+        proof (rule analytic_continuation_open[where f = "eval_fps G" and g = "zor_poly f 0"])
+          show "connected (ball 0 R :: complex set)"
+            by auto
+          have "of_real R / 2 \<in> ball 0 R - {0 :: complex}"
+            using R by auto
+          thus "ball 0 R - {0 :: complex} \<noteq> {}"
+            by blast
+          show "eval_fps G holomorphic_on ball 0 R"
+            using R less_le_trans[OF _ R(4)] unfolding G_def
+            by (intro holomorphic_intros) (auto simp: fls_conv_radius_altdef)
+          show "zor_poly f 0 holomorphic_on ball 0 R"
+            by (rule holomorphic_on_subset[OF holo]) (use R in auto)
+          show "eval_fps G z = zor_poly f 0 z" if "z \<in> ball 0 R - {0}" for z
+            using that r r' R n_altdef unfolding G_def
+            by (subst eval_fps_fls_base_factor)
+               (auto simp: complex_powr_of_int field_simps power_int_minus n_def)
+        qed (use R in auto)
+        hence "zor_poly f 0 0 = fps_nth G 0"
+          by (simp add: eval_fps_at_0)
+        thus ?thesis by simp
+      qed
+    qed
+  qed (use r' in auto)
+  finally show ?thesis
+    by (simp add: G_def)
+qed
+
+lemma zorder_geI_0:
+  assumes "f analytic_on {0}" "f holomorphic_on A" "open A" "connected A" "0 \<in> A" "z \<in> A" "f z \<noteq> 0"
+  assumes "\<And>k. k < n \<Longrightarrow> (deriv ^^ k) f 0 = 0"
+  shows   "zorder f 0 \<ge> n"
+proof -
+  define F where "F = fps_expansion f 0"
+  from assms have "f has_fps_expansion F"
+    unfolding F_def using analytic_at_imp_has_fps_expansion_0 by blast
+  hence laurent: "f has_laurent_expansion fps_to_fls F" and [simp]: "f 0 = fps_nth F 0"
+    by (simp_all add: has_fps_expansion_to_laurent)
+
+  have [simp]: "F \<noteq> 0"
+  proof
+    assume [simp]: "F = 0"
+    hence "f z = 0"
+    proof (cases "z = 0")
+      case False
+      have "f has_laurent_expansion 0"
+        using laurent by simp
+      thus ?thesis
+      proof (rule has_laurent_expansion_0_analytic_continuation)
+        show "f holomorphic_on A - {0}"
+          using assms(2) by (rule holomorphic_on_subset) auto
+      qed (use assms False in auto)
+    qed auto
+    with \<open>f z \<noteq> 0\<close> show False by contradiction
+  qed
+
+  have "zorder f 0 = int (subdegree F)"
+    using has_laurent_expansion_zorder_0[OF laurent] by (simp add: fls_subdegree_fls_to_fps)
+  also have "subdegree F \<ge> n"
+    using assms by (intro subdegree_geI \<open>F \<noteq> 0\<close>) (auto simp: F_def fps_expansion_def)
+  hence "int (subdegree F) \<ge> int n"
+    by simp
+  finally show ?thesis .
+qed
+
+lemma zorder_geI:
+  assumes "f analytic_on {x}" "f holomorphic_on A" "open A" "connected A" "x \<in> A" "z \<in> A" "f z \<noteq> 0"
+  assumes "\<And>k. k < n \<Longrightarrow> (deriv ^^ k) f x = 0"
+  shows   "zorder f x \<ge> n"
+proof -
+  have "zorder f x = zorder (f \<circ> (\<lambda>u. u + x)) 0"
+    by (subst zorder_shift) (auto simp: o_def)
+  also have "\<dots> \<ge> n"
+  proof (rule zorder_geI_0)
+    show "(f \<circ> (\<lambda>u. u + x)) analytic_on {0}"
+      by (intro analytic_on_compose_gen[OF _ assms(1)] analytic_intros) auto
+    show "f \<circ> (\<lambda>u. u + x) holomorphic_on ((+) (-x)) ` A"
+      by (intro holomorphic_on_compose_gen[OF _ assms(2)] holomorphic_intros) auto
+    show "connected ((+) (- x) ` A)"
+      by (intro connected_continuous_image continuous_intros assms)
+    show "open ((+) (- x) ` A)"
+      by (intro open_translation assms)
+    show "z - x \<in> (+) (- x) ` A"
+      using \<open>z \<in> A\<close> by auto
+    show "0 \<in> (+) (- x) ` A"
+      using \<open>x \<in> A\<close> by auto
+    show "(f \<circ> (\<lambda>u. u + x)) (z - x) \<noteq> 0"
+      using \<open>f z \<noteq> 0\<close> by auto
+  next
+    fix k :: nat assume "k < n"
+    hence "(deriv ^^ k) f x = 0"
+      using assms by simp
+    also have "(deriv ^^ k) f x = (deriv ^^ k) (f \<circ> (+) x) 0"
+      by (subst higher_deriv_shift_0) auto
+    finally show "(deriv ^^ k) (f \<circ> (\<lambda>u. u + x)) 0 = 0"
+      by (subst add.commute) auto
+  qed
+  finally show ?thesis .
+qed
+
+lemma has_laurent_expansion_divide [laurent_expansion_intros]:
+  assumes "f has_laurent_expansion F" and "g has_laurent_expansion G"
+  shows   "(\<lambda>x. f x / g x) has_laurent_expansion (F / G)"
+proof -
+  have "(\<lambda>x. f x * inverse (g x)) has_laurent_expansion (F * inverse G)"
+    by (intro laurent_expansion_intros assms)
+  thus ?thesis
+    by (simp add: field_simps)
+qed
+
+lemma vector_derivative_translate [simp]:
+  "vector_derivative ((+) z \<circ> g) (at x within A) = vector_derivative g (at x within A)"
+proof -
+  have "(((+) z \<circ> g) has_vector_derivative g') (at x within A)"
+    if "(g has_vector_derivative g') (at x within A)" for g :: "real \<Rightarrow> 'a" and z g'
+    unfolding o_def using that by (auto intro!: derivative_eq_intros)
+  from this[of g _ z] this[of "\<lambda>x. z + g x" _ "-z"] show ?thesis
+    unfolding vector_derivative_def
+    by (intro arg_cong[where f = Eps] ext) (auto simp: o_def algebra_simps)
+qed
+
+lemma has_contour_integral_translate:
+  "(f has_contour_integral I) ((+) z \<circ> g) \<longleftrightarrow> ((\<lambda>x. f (x + z)) has_contour_integral I) g"
+  by (simp add: has_contour_integral_def add_ac)
+
+lemma contour_integrable_translate:
+  "f contour_integrable_on ((+) z \<circ> g) \<longleftrightarrow> (\<lambda>x. f (x + z)) contour_integrable_on g"
+  by (simp add: contour_integrable_on_def has_contour_integral_translate)
+
+lemma contour_integral_translate:
+  "contour_integral ((+) z \<circ> g) f = contour_integral g (\<lambda>x. f (x + z))"
+  by (simp add: contour_integral_def contour_integrable_translate has_contour_integral_translate)
+
+lemma residue_shift_0: "residue f z = residue (\<lambda>x. f (z + x)) 0"
+proof -
+  define Q where
+    "Q = (\<lambda>r f z \<epsilon>. (f has_contour_integral complex_of_real (2 * pi) * \<i> * r) (circlepath z \<epsilon>))"
+  define P where
+    "P = (\<lambda>r f z. \<exists>e>0. \<forall>\<epsilon>>0. \<epsilon> < e \<longrightarrow> Q r f z \<epsilon>)"
+  have path_eq: "circlepath (z - w) \<epsilon> = (+) (-w) \<circ> circlepath z \<epsilon>" for z w \<epsilon>
+    by (simp add: circlepath_def o_def part_circlepath_def algebra_simps)
+  have *: "P r f z" if "P r (\<lambda>x. f (x + w)) (z - w)" for r w f z
+    using that by (auto simp: P_def Q_def path_eq has_contour_integral_translate)
+  have "(SOME r. P r f z) = (SOME r. P r (\<lambda>x. f (z + x)) 0)"
+    using *[of _ f z z] *[of _ "\<lambda>x. f (z + x)" "-z"]
+    by (intro arg_cong[where f = Eps] ext iffI) (simp_all add: add_ac)
+  thus ?thesis
+    by (simp add: residue_def P_def Q_def)
+qed
+
+lemma residue_shift_0': "NO_MATCH 0 z \<Longrightarrow> residue f z = residue (\<lambda>x. f (z + x)) 0"
+  by (rule residue_shift_0)
+
+lemma has_laurent_expansion_residue_0:
+  assumes "f has_laurent_expansion F"
+  shows   "residue f 0 = fls_residue F"
+proof (cases "fls_subdegree F \<ge> 0")
+  case True
+  have "residue f 0 = residue (eval_fls F) 0"
+    using assms by (intro residue_cong) (auto simp: has_laurent_expansion_def eq_commute)
+  also have "\<dots> = 0"
+    by (rule residue_holo[OF _ _ holomorphic_on_eval_fls[OF order.refl]])
+       (use True assms in \<open>auto simp: has_laurent_expansion_def zero_ereal_def\<close>)
+  also have "\<dots> = fls_residue F"
+    using True by simp
+  finally show ?thesis .
+next
+  case False
+  hence "F \<noteq> 0"
+    by auto
+  have *: "zor_poly f 0 has_fps_expansion fls_base_factor_to_fps F"
+    by (intro zor_poly_has_fps_expansion False assms \<open>F \<noteq> 0\<close>)
+
+  have "residue f 0 = (deriv ^^ (nat (-zorder f 0) - 1)) (zor_poly f 0) 0 / fact (nat (- zorder f 0) - 1)"
+    by (intro residue_pole_order has_laurent_expansion_isolated_0[OF assms]
+              has_laurent_expansion_imp_is_pole_0[OF assms]) (use False in auto)
+  also have "\<dots> = fls_residue F"
+    using has_laurent_expansion_zorder_0[OF assms \<open>F \<noteq> 0\<close>] False
+    by (subst fps_nth_fps_expansion [OF *, symmetric]) (auto simp: of_nat_diff)
+  finally show ?thesis .
+qed
+
+lemma has_laurent_expansion_residue:
+  assumes "(\<lambda>x. f (z + x)) has_laurent_expansion F"
+  shows   "residue f z = fls_residue F"
+  using has_laurent_expansion_residue_0[OF assms] by (simp add: residue_shift_0')
+
+lemma eval_fls_has_laurent_expansion [laurent_expansion_intros]:
+  assumes "fls_conv_radius F > 0"
+  shows   "eval_fls F has_laurent_expansion F"
+  using assms by (auto simp: has_laurent_expansion_def)
+
+lemma fps_expansion_unique_complex:
+  fixes F G :: "complex fps"
+  assumes "f has_fps_expansion F" "f has_fps_expansion G"
+  shows   "F = G"
+  using assms unfolding fps_eq_iff by (auto simp: fps_eq_iff fps_nth_fps_expansion)
+
+lemma fps_expansion_eqI:
+  assumes "f has_fps_expansion F"
+  shows   "fps_expansion f 0 = F"
+  using assms unfolding fps_eq_iff
+  by (auto simp: fps_eq_iff fps_nth_fps_expansion fps_expansion_def)
+
+lemma has_fps_expansion_imp_eval_fps_eq:
+  assumes "f has_fps_expansion F" "norm z < r"
+  assumes "f holomorphic_on ball 0 r"
+  shows   "eval_fps F z = f z"
+proof -
+  have [simp]: "fps_expansion f 0 = F"
+    by (rule fps_expansion_eqI) fact
+  have *: "f holomorphic_on eball 0 (ereal r)"
+    using assms by simp
+  from conv_radius_fps_expansion[OF *] have "fps_conv_radius F \<ge> ereal r"
+    by simp
+  have "eval_fps (fps_expansion f 0) z = f (0 + z)"
+    by (rule eval_fps_expansion'[OF *]) (use assms in auto)
+  thus ?thesis
+    by simp
+qed
+
+lemma fls_conv_radius_ge:
+  assumes "f has_laurent_expansion F"
+  assumes "f holomorphic_on eball 0 r - {0}"
+  shows   "fls_conv_radius F \<ge> r"
+proof -
+  define n where "n = fls_subdegree F"
+  define G where "G = fls_base_factor_to_fps F"
+  define g where "g = (\<lambda>z. if z = 0 then fps_nth G 0 else f z * z powi -n)"
+  have G: "g has_fps_expansion G"
+    unfolding G_def g_def n_def
+    by (intro has_fps_expansion_fls_base_factor_to_fps assms)
+  have "(\<lambda>z. f z * z powi -n) holomorphic_on eball 0 r - {0}"
+    by (intro holomorphic_intros assms) auto
+  also have "?this \<longleftrightarrow> g holomorphic_on eball 0 r - {0}"
+    by (intro holomorphic_cong) (auto simp: g_def)
+  finally have "g analytic_on eball 0 r - {0}"
+    by (subst analytic_on_open) auto
+  moreover have "g analytic_on {0}"
+    using G has_fps_expansion_imp_analytic_0 by auto
+  ultimately have "g analytic_on (eball 0 r - {0} \<union> {0})"
+    by (subst analytic_on_Un) auto
+  hence "g analytic_on eball 0 r"
+    by (rule analytic_on_subset) auto
+  hence "g holomorphic_on eball 0 r"
+    by (subst (asm) analytic_on_open) auto
+  hence "fps_conv_radius (fps_expansion g 0) \<ge> r"
+    by (intro conv_radius_fps_expansion)
+  also have "fps_expansion g 0 = G"
+    using G by (intro fps_expansion_eqI)
+  finally show ?thesis
+    by (simp add: fls_conv_radius_altdef G_def)
+qed
+
+lemma connected_eball [intro]: "connected (eball (z :: 'a :: real_normed_vector) r)"
+  by (cases r) auto
+
+lemma eval_fls_eqI:
+  assumes "f has_laurent_expansion F" "f holomorphic_on eball 0 r - {0}"
+  assumes "z \<in> eball 0 r - {0}"
+  shows   "eval_fls F z = f z"
+proof -
+  have conv: "fls_conv_radius F \<ge> r"
+    by (intro fls_conv_radius_ge[OF assms(1,2)])
+  have "(\<lambda>z. eval_fls F z - f z) has_laurent_expansion F - F"
+    using assms by (intro laurent_expansion_intros assms) (auto simp: has_laurent_expansion_def)
+  hence "(\<lambda>z. eval_fls F z - f z) has_laurent_expansion 0"
+    by simp
+  hence "eval_fls F z - f z = 0"
+  proof (rule has_laurent_expansion_0_analytic_continuation)
+    have "ereal 0 \<le> ereal (norm z)"
+      by simp
+    also have "norm z < r"
+      using assms by auto
+    finally have "r > 0"
+      by (simp add: zero_ereal_def)
+    thus "open (eball 0 r :: complex set)" "connected (eball 0 r :: complex set)"
+         "0 \<in> eball 0 r" "z \<in> eball 0 r - {0}"
+      using assms by (auto simp: zero_ereal_def)
+  qed (auto intro!: holomorphic_intros assms less_le_trans[OF _ conv] split: if_splits)
+  thus ?thesis by simp
+qed
+
+lemma fls_nth_as_contour_integral:
+  assumes F: "f has_laurent_expansion F"
+  assumes holo: "f holomorphic_on ball 0 r - {0}"
+  assumes R: "0 < R" "R < r"
+  shows "((\<lambda>z. f z * z powi (-(n+1))) has_contour_integral
+            complex_of_real (2 * pi) * \<i> * fls_nth F n) (circlepath 0 R)"
+proof -
+  define I where "I = (\<lambda>z. f z * z powi (-(n+1)))"
+  have "(I has_contour_integral complex_of_real (2 * pi) * \<i> * residue I 0) (circlepath 0 R)"
+  proof (rule base_residue)
+    show "open (ball (0::complex) r)" "0 \<in> ball (0::complex) r"
+      using R F by (auto simp: has_laurent_expansion_def zero_ereal_def)
+  qed (use R in \<open>auto intro!: holomorphic_intros holomorphic_on_subset[OF holo]
+                      simp: I_def split: if_splits\<close>)
+  also have "residue I 0 = fls_residue (fls_shift (n + 1) F)"
+    unfolding I_def by (intro has_laurent_expansion_residue_0 laurent_expansion_intros F)
+  also have "\<dots> = fls_nth F n"
+    by simp
+  finally show ?thesis
+    by (simp add: I_def)
+qed
+
+lemma tendsto_0_subdegree_iff_0:
+  assumes F:"f has_laurent_expansion F" and "F\<noteq>0"
+  shows "(f \<midarrow>0\<rightarrow>0) \<longleftrightarrow> fls_subdegree F > 0"
+proof -
+  have ?thesis if "is_pole f 0"
+  proof -
+    have "fls_subdegree F <0"
+      using is_pole_0_imp_neg_fls_subdegree[OF F that] .
+    moreover then have "\<not> f \<midarrow>0\<rightarrow>0"
+      using \<open>is_pole f 0\<close> F at_neq_bot
+        has_laurent_expansion_imp_filterlim_infinity_0
+        not_tendsto_and_filterlim_at_infinity that
+      by blast
+    ultimately show ?thesis by auto
+  qed
+  moreover have ?thesis if "\<not>is_pole f 0" "\<exists>x. f \<midarrow>0\<rightarrow>x"
+  proof -
+    have "fls_subdegree F \<ge>0"
+      using has_laurent_expansion_imp_is_pole_0[OF F] that(1)
+      by linarith
+    have "f \<midarrow>0\<rightarrow>0" if "fls_subdegree F > 0"
+      using fls_eq0_below_subdegree[OF that]
+      by (metis F \<open>0 \<le> fls_subdegree F\<close> has_laurent_expansion_imp_tendsto_0)
+    moreover have "fls_subdegree F > 0" if "f \<midarrow>0\<rightarrow>0"
+    proof -
+      have False if "fls_subdegree F = 0"
+      proof -
+        have "f \<midarrow>0\<rightarrow> fls_nth F 0"
+          using has_laurent_expansion_imp_tendsto_0
+              [OF F \<open>fls_subdegree F \<ge>0\<close>] .
+        then have "fls_nth F 0 = 0" using \<open>f \<midarrow>0\<rightarrow>0\<close>
+          using LIM_unique by blast
+        then have "F = 0"
+          using nth_fls_subdegree_zero_iff \<open>fls_subdegree F = 0\<close>
+          by metis
+        with \<open>F\<noteq>0\<close> show False by auto
+      qed
+      with \<open>fls_subdegree F \<ge>0\<close>
+      show ?thesis by fastforce
+    qed
+    ultimately show ?thesis by auto
+  qed
+  moreover have "is_pole f 0 \<or> (\<exists>x. f \<midarrow>0\<rightarrow>x)"
+  proof -
+    have "not_essential f 0"
+      using F has_laurent_expansion_not_essential_0 by auto
+    then show ?thesis unfolding not_essential_def
+      by auto
+  qed
+  ultimately show ?thesis by auto
+qed
+
+lemma tendsto_0_subdegree_iff:
+  assumes F:"(\<lambda>w. f (z+w)) has_laurent_expansion F" and "F\<noteq>0"
+  shows "(f \<midarrow>z\<rightarrow>0) \<longleftrightarrow> fls_subdegree F > 0"
+  apply (subst Lim_at_zero)
+  apply (rule tendsto_0_subdegree_iff_0)
+  using assms by auto
+
+lemma is_pole_0_deriv_divide_iff:
+  assumes F:"f has_laurent_expansion F" and "F\<noteq>0"
+  shows "is_pole (\<lambda>x. deriv f x / f x) 0 \<longleftrightarrow> is_pole f 0 \<or> (f \<midarrow>0\<rightarrow>0)"
+proof -
+  have "(\<lambda>x. deriv f x / f x) has_laurent_expansion fls_deriv F / F"
+    using F by (auto intro:laurent_expansion_intros)
+
+  have "is_pole (\<lambda>x. deriv f x / f x) 0 \<longleftrightarrow>
+            fls_subdegree (fls_deriv F / F) < 0"
+    apply (rule is_pole_fls_subdegree_iff)
+    using F by (auto intro:laurent_expansion_intros)
+  also have "... \<longleftrightarrow> is_pole f 0 \<or> (f \<midarrow>0\<rightarrow>0)"
+  proof (cases "fls_subdegree F = 0")
+    case True
+    then have "fls_subdegree (fls_deriv F / F) \<ge> 0"
+      by (metis diff_zero div_0 \<open>F\<noteq>0\<close> fls_deriv_subdegree0
+          fls_divide_subdegree)
+    moreover then have "\<not> is_pole f 0"
+      by (metis F True is_pole_0_imp_neg_fls_subdegree less_le)
+    moreover have "\<not> (f \<midarrow>0\<rightarrow>0)"
+      using tendsto_0_subdegree_iff_0[OF F \<open>F\<noteq>0\<close>] True by auto
+    ultimately show ?thesis by auto
+  next
+    case False
+    then have "fls_deriv F \<noteq> 0"
+      by (metis fls_const_subdegree fls_deriv_eq_0_iff)
+    then have "fls_subdegree (fls_deriv F / F) =
+              fls_subdegree (fls_deriv F) - fls_subdegree F"
+      by (rule fls_divide_subdegree[OF _ \<open>F\<noteq>0\<close>])
+    moreover have "fls_subdegree (fls_deriv F) = fls_subdegree F - 1"
+      using fls_subdegree_deriv[OF False] .
+    ultimately have "fls_subdegree (fls_deriv F / F) < 0" by auto
+    moreover have "f \<midarrow>0\<rightarrow> 0 = (0 < fls_subdegree F)"
+      using tendsto_0_subdegree_iff_0[OF F \<open>F \<noteq> 0\<close>] .
+    moreover have "is_pole f 0 = (fls_subdegree F < 0)"
+      using is_pole_fls_subdegree_iff F by auto
+    ultimately show ?thesis using False by auto
+  qed
+  finally show ?thesis .
+qed
+
+lemma is_pole_deriv_divide_iff:
+  assumes F:"(\<lambda>w. f (z+w))  has_laurent_expansion F" and "F\<noteq>0"
+  shows "is_pole (\<lambda>x. deriv f x / f x) z \<longleftrightarrow> is_pole f z \<or> (f \<midarrow>z\<rightarrow>0)"
+proof -
+  define ff df where "ff=(\<lambda>w. f (z+w))" and "df=(\<lambda>w. deriv f (z + w))"
+  have "is_pole (\<lambda>x. deriv f x / f x) z
+          \<longleftrightarrow> is_pole (\<lambda>x. deriv ff x / ff x) 0"
+    unfolding ff_def df_def
+    by (simp add:deriv_shift_0' is_pole_shift_0' comp_def algebra_simps)
+  moreover have "is_pole f z \<longleftrightarrow> is_pole ff 0"
+    unfolding ff_def by (auto simp:is_pole_shift_0')
+  moreover have "(f \<midarrow>z\<rightarrow>0) \<longleftrightarrow> (ff \<midarrow>0\<rightarrow>0)"
+    unfolding ff_def by (simp add: LIM_offset_zero_iff)
+  moreover have "is_pole (\<lambda>x. deriv ff x / ff x) 0 = (is_pole ff 0 \<or> ff \<midarrow>0\<rightarrow> 0)"
+    apply (rule is_pole_0_deriv_divide_iff)
+    using F ff_def \<open>F\<noteq>0\<close> by blast+
+  ultimately show ?thesis by auto
+qed
+
+lemma subdegree_imp_eventually_deriv_nzero_0:
+  assumes F:"f has_laurent_expansion F" and "fls_subdegree F\<noteq>0"
+  shows "eventually (\<lambda>z. deriv f z \<noteq> 0) (at 0)"
+proof -
+  have "deriv f has_laurent_expansion fls_deriv F"
+    using has_laurent_expansion_deriv[OF F] .
+  moreover have "fls_deriv F\<noteq>0"
+    using \<open>fls_subdegree F\<noteq>0\<close>
+    by (metis fls_const_subdegree fls_deriv_eq_0_iff)
+  ultimately show ?thesis
+    using has_laurent_expansion_eventually_nonzero_iff' by blast
+qed
+
+lemma subdegree_imp_eventually_deriv_nzero:
+  assumes F:"(\<lambda>w. f (z+w)) has_laurent_expansion F"
+      and "fls_subdegree F\<noteq>0"
+  shows "eventually (\<lambda>w. deriv f w \<noteq> 0) (at z)"
+proof -
+  have "\<forall>\<^sub>F x in at 0. deriv (\<lambda>w. f (z + w)) x \<noteq> 0"
+    using subdegree_imp_eventually_deriv_nzero_0 assms by auto
+  then show ?thesis
+    apply (subst eventually_at_to_0)
+    by (simp add:deriv_shift_0' comp_def algebra_simps)
+qed
+
+lemma has_fps_expansion_imp_asymp_equiv_0:
+  fixes f :: "complex \<Rightarrow> complex"
+  assumes F: "f has_fps_expansion F"
+  defines "n \<equiv> subdegree F"
+  shows   "f \<sim>[nhds 0] (\<lambda>z. fps_nth F n * z ^ n)"
+proof -
+  have F': "f has_laurent_expansion fps_to_fls F"
+    using F has_laurent_expansion_fps by blast
+
+  have "f \<sim>[at 0] (\<lambda>z. fps_nth F n * z ^ n)"
+    using has_laurent_expansion_imp_asymp_equiv_0[OF F']
+    by (simp add: fls_subdegree_fls_to_fps n_def)
+  moreover have "f 0 = fps_nth F n * 0 ^ n"
+    using F by (auto simp: n_def has_fps_expansion_to_laurent power_0_left)
+  ultimately show ?thesis
+    by (auto simp: asymp_equiv_nhds_iff)
+qed
+
+lemma has_fps_expansion_imp_tendsto_0:
+  fixes f :: "complex \<Rightarrow> complex"
+  assumes "f has_fps_expansion F"
+  shows   "(f \<longlongrightarrow> fps_nth F 0) (nhds 0)"
+proof (rule asymp_equiv_tendsto_transfer)
+  show "(\<lambda>z. fps_nth F (subdegree F) * z ^ subdegree F) \<sim>[nhds 0] f"
+    by (rule asymp_equiv_symI, rule has_fps_expansion_imp_asymp_equiv_0) fact
+  have "((\<lambda>z. F $ subdegree F * z ^ subdegree F) \<longlongrightarrow> F $ 0) (at 0)"
+    by (rule tendsto_eq_intros refl | simp)+ (auto simp: power_0_left)
+  thus "((\<lambda>z. F $ subdegree F * z ^ subdegree F) \<longlongrightarrow> F $ 0) (nhds 0)"
+    by (auto simp: tendsto_nhds_iff power_0_left)
+qed
+
+lemma has_fps_expansion_imp_0_eq_fps_nth_0:
+  assumes "f has_fps_expansion F"
+  shows   "f 0 = fps_nth F 0"
+proof -
+  have "eventually (\<lambda>x. f x = eval_fps F x) (nhds 0)"
+    using assms by (auto simp: has_fps_expansion_def eq_commute)
+  then obtain A where "open A" "0 \<in> A" "\<forall>x\<in>A. f x = eval_fps F x"
+    unfolding eventually_nhds by blast
+  hence "f 0 = eval_fps F 0"
+    by blast
+  thus ?thesis
+    by (simp add: eval_fps_at_0)
+qed
+
+lemma fls_nth_compose_aux:
+  assumes "f has_fps_expansion F"
+  assumes G: "g has_fps_expansion G" "fps_nth G 0 = 0" "fps_deriv G \<noteq> 0"
+  assumes "(f \<circ> g) has_laurent_expansion H"
+  shows   "fls_nth H (int n) = fps_nth (fps_compose F G) n"
+  using assms(1,5)
+proof (induction n arbitrary: f F H rule: less_induct)
+  case (less n f F H)
+  have [simp]: "g 0 = 0"
+    using has_fps_expansion_imp_0_eq_fps_nth_0[OF G(1)] G(2) by simp
+  have ana_f: "f analytic_on {0}"
+    using less.prems by (meson has_fps_expansion_imp_analytic_0)
+  have ana_g: "g analytic_on {0}"
+    using G by (meson has_fps_expansion_imp_analytic_0)
+  have "(f \<circ> g) has_laurent_expansion fps_to_fls (fps_expansion (f \<circ> g) 0)"
+    by (rule analytic_at_imp_has_fps_expansion_0 analytic_intros has_laurent_expansion_fps
+             analytic_on_compose_gen ana_f ana_g)+ auto
+  with less.prems have "H = fps_to_fls (fps_expansion (f \<circ> g) 0)"
+    using has_laurent_expansion_unique by blast
+  also have "fls_subdegree \<dots> \<ge> 0"
+    by (simp add: fls_subdegree_fls_to_fps)
+  finally have subdeg: "fls_subdegree H \<ge> 0" .
+
+  show ?case
+  proof (cases "n = 0")
+    case [simp]: True
+    have lim_g: "g \<midarrow>0\<rightarrow> 0"
+      using has_laurent_expansion_imp_tendsto_0[of g "fps_to_fls G"] G
+      by (auto simp: fls_subdegree_fls_to_fps_gt0 has_fps_expansion_to_laurent)
+    have lim_f: "(f \<longlongrightarrow> fps_nth F 0) (nhds 0)"
+      by (intro has_fps_expansion_imp_tendsto_0 less.prems)
+    have "(\<lambda>x. f (g x)) \<midarrow>0\<rightarrow> fps_nth F 0"
+      by (rule filterlim_compose[OF lim_f lim_g])
+    moreover have "(f \<circ> g) \<midarrow>0\<rightarrow> fls_nth H 0"
+      by (intro has_laurent_expansion_imp_tendsto_0 less.prems subdeg)
+    ultimately have "fps_nth F 0 = fls_nth H 0"
+      using tendsto_unique by (force simp: o_def)
+    thus ?thesis
+      by simp
+  next
+    case n: False
+    define GH where "GH = (fls_deriv H / fls_deriv (fps_to_fls G))"
+    define GH' where "GH' = fls_regpart GH"
+
+    have "(\<lambda>x. deriv (f \<circ> g) x / deriv g x) has_laurent_expansion
+          fls_deriv H / fls_deriv (fps_to_fls G)"
+      by (intro laurent_expansion_intros less.prems has_laurent_expansion_fps[of _ G] G)
+    also have "?this \<longleftrightarrow> (deriv f \<circ> g) has_laurent_expansion fls_deriv H / fls_deriv (fps_to_fls G)"
+    proof (rule has_laurent_expansion_cong)
+      from ana_f obtain r1 where r1: "r1 > 0" "f holomorphic_on ball 0 r1"
+        unfolding analytic_on_def by blast
+      from ana_g obtain r2 where r2: "r2 > 0" "g holomorphic_on ball 0 r2"
+        unfolding analytic_on_def by blast
+      have lim_g: "g \<midarrow>0\<rightarrow> 0"
+        using has_laurent_expansion_imp_tendsto_0[of g "fps_to_fls G"] G
+        by (auto simp: fls_subdegree_fls_to_fps_gt0 has_fps_expansion_to_laurent)
+      moreover have "open (ball 0 r1)" "0 \<in> ball 0 r1"
+        using r1 by auto
+      ultimately have "eventually (\<lambda>x. g x \<in> ball 0 r1) (at 0)"
+        unfolding tendsto_def by blast
+      moreover have "eventually (\<lambda>x. deriv g x \<noteq> 0) (at 0)"
+        using G fps_to_fls_eq_0_iff has_fps_expansion_deriv has_fps_expansion_to_laurent
+              has_laurent_expansion_nonzero_imp_eventually_nonzero by blast
+      moreover have "eventually (\<lambda>x. x \<in> ball 0 (min r1 r2) - {0}) (at 0)"
+        by (intro eventually_at_in_open) (use r1 r2 in auto)
+      ultimately show "eventually (\<lambda>x. deriv (f \<circ> g) x / deriv g x = (deriv f \<circ> g) x) (at 0)"
+      proof eventually_elim
+        case (elim x)
+        thus ?case using r1 r2
+          by (subst deriv_chain)
+             (auto simp: field_simps holomorphic_on_def at_within_open[of _ "ball _ _"])
+      qed
+    qed auto
+    finally have GH: "(deriv f \<circ> g) has_laurent_expansion GH"
+      unfolding GH_def .
+
+    have "(deriv f \<circ> g) has_laurent_expansion fps_to_fls (fps_expansion (deriv f \<circ> g) 0)"
+      by (rule analytic_at_imp_has_fps_expansion_0 analytic_intros has_laurent_expansion_fps
+               analytic_on_compose_gen ana_f ana_g)+ auto
+    with GH have "GH = fps_to_fls (fps_expansion (deriv f \<circ> g) 0)"
+      using has_laurent_expansion_unique by blast
+    also have "fls_subdegree \<dots> \<ge> 0"
+      by (simp add: fls_subdegree_fls_to_fps)
+    finally have subdeg': "fls_subdegree GH \<ge> 0" .
+
+    have "deriv f has_fps_expansion fps_deriv F"
+      by (intro fps_expansion_intros less.prems)
+    from this and GH have IH: "fls_nth GH (int k) = fps_nth (fps_compose (fps_deriv F) G) k"
+      if "k < n" for k
+      by (intro less.IH that)
+
+    have "fps_nth (fps_compose (fps_deriv F) G) n = (\<Sum>i=0..n. of_nat (Suc i) * F $ Suc i * G ^ i $ n)"
+      by (simp add: fps_compose_nth)
+
+    have "fps_nth (fps_compose F G) n =
+            fps_nth (fps_deriv (fps_compose F G)) (n - 1) / of_nat n"
+      using n by (cases n) (auto simp del: of_nat_Suc)
+    also have "fps_deriv (fps_compose F G) = fps_compose (fps_deriv F) G * fps_deriv G "
+      using G by (subst fps_compose_deriv) auto
+    also have "fps_nth \<dots> (n - 1) = (\<Sum>i=0..n-1. (fps_deriv F oo G) $ i * fps_deriv G $ (n - 1 - i))"
+      unfolding fps_mult_nth ..
+    also have "\<dots> = (\<Sum>i=0..n-1. fps_nth GH' i * of_nat (n - i) * G $ (n - i))"
+      using n by (intro sum.cong) (auto simp: IH Suc_diff_Suc GH'_def)
+    also have "\<dots> = (\<Sum>i=0..n. fps_nth GH' i * of_nat (n - i) * G $ (n - i))"
+      by (intro sum.mono_neutral_left) auto
+    also have "\<dots> = fps_nth (GH' * Abs_fps (\<lambda>i. of_nat i * fps_nth G i)) n"
+      by (simp add: fps_mult_nth mult_ac)
+    also have "Abs_fps (\<lambda>i. of_nat i * fps_nth G i) = fps_X * fps_deriv G"
+      by (simp add: fps_mult_fps_X_deriv_shift)
+    also have "fps_nth (GH' * (fps_X * fps_deriv G)) n =
+               fls_nth (fps_to_fls (GH' * (fps_X * fps_deriv G))) (int n)"
+      by simp
+    also have "fps_to_fls (GH' * (fps_X * fps_deriv G)) =
+                 GH * fps_to_fls (fps_deriv G) * fls_X"
+      using subdeg' by (simp add: mult_ac fls_times_fps_to_fls GH'_def)
+    also have "GH * fps_to_fls (fps_deriv G) = fls_deriv H"
+      unfolding GH_def using G  by (simp add: fls_deriv_fps_to_fls)
+    also have "fls_deriv H * fls_X = fls_shift (-1) (fls_deriv H)"
+      using fls_X_times_conv_shift(2) by blast
+    finally show ?thesis
+      using n by simp
+  qed
+qed
+
+lemma has_fps_expansion_compose [fps_expansion_intros]:
+  fixes f g :: "complex \<Rightarrow> complex"
+  assumes F: "f has_fps_expansion F"
+  assumes G: "g has_fps_expansion G" "fps_nth G 0 = 0"
+  shows   "(f \<circ> g) has_fps_expansion fps_compose F G"
+proof (cases "fps_deriv G = 0")
+  case False
+  have [simp]: "g 0 = 0"
+    using has_fps_expansion_imp_0_eq_fps_nth_0[OF G(1)] G(2) False by simp
+  have ana_f: "f analytic_on {0}"
+    using F by (meson has_fps_expansion_imp_analytic_0)
+  have ana_g: "g analytic_on {0}"
+    using G by (meson has_fps_expansion_imp_analytic_0)
+  have fg: "(f \<circ> g) has_fps_expansion fps_expansion (f \<circ> g) 0"
+    by (rule analytic_at_imp_has_fps_expansion_0 analytic_intros
+         analytic_on_compose_gen ana_f ana_g)+ auto
+
+  have "fls_nth (fps_to_fls (fps_expansion (f \<circ> g) 0)) (int n) = fps_nth (fps_compose F G) n" for n
+    by (rule fls_nth_compose_aux has_laurent_expansion_fps F G False fg)+
+  hence "fps_expansion (f \<circ> g) 0 = fps_compose F G"
+    by (simp add: fps_eq_iff)
+  thus ?thesis using fg
+    by simp
+next
+  case True
+  have [simp]: "f 0 = fps_nth F 0"
+    using F by (auto dest: has_fps_expansion_imp_0_eq_fps_nth_0)
+  from True have "fps_nth G n = 0" for n
+    using G(2) by (cases n) (auto simp del: of_nat_Suc)
+  hence [simp]: "G = 0"
+    by (auto simp: fps_eq_iff)
+  have "(\<lambda>_. f 0) has_fps_expansion fps_const (f 0)"
+    by (intro fps_expansion_intros)
+  also have "eventually (\<lambda>x. g x = 0) (nhds 0)"
+    using G by (auto simp: has_fps_expansion_def)
+  hence "(\<lambda>_. f 0) has_fps_expansion fps_const (f 0) \<longleftrightarrow> (f \<circ> g) has_fps_expansion fps_const (f 0)"
+    by (intro has_fps_expansion_cong) (auto elim!: eventually_mono)
+  thus ?thesis
+    by simp
+qed
+
+hide_const (open) fls_compose_fps
+
+definition fls_compose_fps :: "'a :: field fls \<Rightarrow> 'a fps \<Rightarrow> 'a fls" where
+  "fls_compose_fps F G =
+     fps_to_fls (fps_compose (fls_base_factor_to_fps F) G) * fps_to_fls G powi fls_subdegree F"
+
+lemma fps_compose_of_nat [simp]: "fps_compose (of_nat n :: 'a :: comm_ring_1 fps) H = of_nat n"
+  and fps_compose_of_int [simp]: "fps_compose (of_int i) H = of_int i"
+  unfolding fps_of_nat [symmetric] fps_of_int [symmetric] numeral_fps_const
+  by (rule fps_const_compose)+
+
+lemmas [simp] = fps_to_fls_of_nat fps_to_fls_of_int
+
+lemma fls_compose_fps_0 [simp]: "fls_compose_fps 0 H = 0"
+  and fls_compose_fps_1 [simp]: "fls_compose_fps 1 H = 1"
+  and fls_compose_fps_const [simp]: "fls_compose_fps (fls_const c) H = fls_const c"
+  and fls_compose_fps_of_nat [simp]: "fls_compose_fps (of_nat n) H = of_nat n"
+  and fls_compose_fps_of_int [simp]: "fls_compose_fps (of_int i) H = of_int i"
+  and fls_compose_fps_X [simp]: "fls_compose_fps fls_X F = fps_to_fls F"
+  by (simp_all add: fls_compose_fps_def)
+
+lemma fls_compose_fps_0_right:
+  "fls_compose_fps F 0 = (if fls_subdegree F \<ge> 0 then fls_const (fls_nth F 0) else 0)"
+  by (cases "fls_subdegree F = 0") (simp_all add: fls_compose_fps_def)
+
+lemma fls_compose_fps_shift:
+  assumes "H \<noteq> 0"
+  shows   "fls_compose_fps (fls_shift n F) H = fls_compose_fps F H * fps_to_fls H powi (-n)"
+proof (cases "F = 0")
+  case False
+  thus ?thesis
+    using assms by (simp add: fls_compose_fps_def power_int_diff power_int_minus field_simps)
+qed auto
+
+lemma fls_compose_fps_to_fls [simp]:
+  assumes [simp]: "G \<noteq> 0" "fps_nth G 0 = 0"
+  shows   "fls_compose_fps (fps_to_fls F) G = fps_to_fls (fps_compose F G)"
+proof (cases "F = 0")
+  case False
+  define n where "n = subdegree F"
+  define F' where "F' = fps_shift n F"
+  have [simp]: "F' \<noteq> 0" "subdegree F' = 0"
+    using False by (auto simp: F'_def n_def)
+  have F_eq: "F = F' * fps_X ^ n"
+    unfolding F'_def n_def using subdegree_decompose by blast
+  have "fls_compose_fps (fps_to_fls F) G =
+          fps_to_fls (fps_shift n (fls_regpart (fps_to_fls F' * fls_X_intpow (int n))) oo G) * fps_to_fls (G ^ n)"
+    unfolding F_eq fls_compose_fps_def
+    by (simp add: fls_times_fps_to_fls fls_X_power_conv_shift_1 power_int_add
+                  fls_subdegree_fls_to_fps fps_to_fls_power fls_regpart_shift_conv_fps_shift
+             flip: fls_times_both_shifted_simp)
+  also have "fps_to_fls F' * fls_X_intpow (int n) = fps_to_fls F"
+    by (simp add: F_eq fls_times_fps_to_fls fps_to_fls_power fls_X_power_conv_shift_1)
+  also have "fps_to_fls (fps_shift n (fls_regpart (fps_to_fls F)) oo G) * fps_to_fls (G ^ n) =
+             fps_to_fls ((fps_shift n (fls_regpart (fps_to_fls F)) * fps_X ^ n) oo G)"
+    by (simp add: fls_times_fps_to_fls flip: fps_compose_power add: fps_compose_mult_distrib)
+  also have "fps_shift n (fls_regpart (fps_to_fls F)) * fps_X ^ n = F"
+    by (simp add: F_eq)
+  finally show ?thesis .
+qed (auto simp: fls_compose_fps_def)
+
+lemma fls_compose_fps_mult:
+  assumes [simp]: "H \<noteq> 0" "fps_nth H 0 = 0"
+  shows   "fls_compose_fps (F * G) H = fls_compose_fps F H * fls_compose_fps G H"
+  using assms
+proof (cases "F * G = 0")
+  case False
+  hence [simp]: "F \<noteq> 0" "G \<noteq> 0"
+    by auto
+  define n m where "n = fls_subdegree F" "m = fls_subdegree G"
+  define F' where "F' = fls_regpart (fls_shift n F)"
+  define G' where "G' = fls_regpart (fls_shift m G)"
+  have F_eq: "F = fls_shift (-n) (fps_to_fls F')" and G_eq: "G = fls_shift (-m) (fps_to_fls G')"
+    by (simp_all add: F'_def G'_def n_m_def)
+  have "fls_compose_fps (F * G) H = fls_compose_fps (fls_shift (-(n + m)) (fps_to_fls (F' * G'))) H"
+    by (simp add: fls_times_fps_to_fls F_eq G_eq fls_shifted_times_simps)
+  also have "\<dots> = fps_to_fls ((F' oo H) * (G' oo H)) * fps_to_fls H powi (m + n)"
+    by (simp add: fls_compose_fps_shift fps_compose_mult_distrib)
+  also have "\<dots> = fls_compose_fps F H * fls_compose_fps G H"
+    by (simp add: F_eq G_eq fls_compose_fps_shift fls_times_fps_to_fls power_int_add)
+  finally show ?thesis .
+qed auto
+
+lemma fls_compose_fps_power:
+  assumes [simp]: "G \<noteq> 0" "fps_nth G 0 = 0"
+  shows   "fls_compose_fps (F ^ n) G = fls_compose_fps F G ^ n"
+  by (induction n) (auto simp: fls_compose_fps_mult)
+
+lemma fls_compose_fps_add:
+  assumes [simp]: "H \<noteq> 0" "fps_nth H 0 = 0"
+  shows   "fls_compose_fps (F + G) H = fls_compose_fps F H + fls_compose_fps G H"
+proof (cases "F = 0 \<or> G = 0")
+  case False
+  hence [simp]: "F \<noteq> 0" "G \<noteq> 0"
+    by auto
+  define n where "n = min (fls_subdegree F) (fls_subdegree G)"
+  define F' where "F' = fls_regpart (fls_shift n F)"
+  define G' where "G' = fls_regpart (fls_shift n G)"
+  have F_eq: "F = fls_shift (-n) (fps_to_fls F')" and G_eq: "G = fls_shift (-n) (fps_to_fls G')"
+    unfolding n_def by (simp_all add: F'_def G'_def n_def)
+  have "F + G = fls_shift (-n) (fps_to_fls (F' + G'))"
+    by (simp add: F_eq G_eq)
+  also have "fls_compose_fps \<dots> H = fls_compose_fps (fps_to_fls (F' + G')) H * fps_to_fls H powi n"
+    by (subst fls_compose_fps_shift) auto
+  also have "\<dots> = fps_to_fls (fps_compose (F' + G') H) * fps_to_fls H powi n"
+    by (subst fls_compose_fps_to_fls) auto
+  also have "\<dots> = fls_compose_fps F H + fls_compose_fps G H"
+    by (simp add: F_eq G_eq fls_compose_fps_shift fps_compose_add_distrib algebra_simps)
+  finally show ?thesis .
+qed auto
+
+lemma fls_compose_fps_uminus [simp]: "fls_compose_fps (-F) H = -fls_compose_fps F H"
+  by (simp add: fls_compose_fps_def fps_compose_uminus)
+
+lemma fls_compose_fps_diff:
+  assumes [simp]: "H \<noteq> 0" "fps_nth H 0 = 0"
+  shows   "fls_compose_fps (F - G) H = fls_compose_fps F H - fls_compose_fps G H"
+  using fls_compose_fps_add[of H F "-G"] by simp
+
+lemma fps_compose_eq_0_iff:
+  fixes F G :: "'a :: idom fps"
+  assumes "fps_nth G 0 = 0"
+  shows "fps_compose F G = 0 \<longleftrightarrow> F = 0 \<or> (G = 0 \<and> fps_nth F 0 = 0)"
+proof safe
+  assume *: "fps_compose F G = 0" "F \<noteq> 0"
+  have "fps_nth (fps_compose F G) 0 = fps_nth F 0"
+    by simp
+  also have "fps_compose F G = 0"
+    by (simp add: *)
+  finally show "fps_nth F 0 = 0"
+    by simp
+  show "G = 0"
+  proof (rule ccontr)
+    assume "G \<noteq> 0"
+    hence "subdegree G > 0" using assms
+      using subdegree_eq_0_iff by blast
+    define N where "N = subdegree F * subdegree G"
+    have "fps_nth (fps_compose F G) N = (\<Sum>i = 0..N. fps_nth F i * fps_nth (G ^ i) N)"
+      unfolding fps_compose_def by (simp add: N_def)
+    also have "\<dots> = (\<Sum>i\<in>{subdegree F}. fps_nth F i * fps_nth (G ^ i) N)"
+    proof (intro sum.mono_neutral_right ballI)
+      fix i assume i: "i \<in> {0..N} - {subdegree F}"
+      show "fps_nth F i * fps_nth (G ^ i) N = 0"
+      proof (cases i "subdegree F" rule: linorder_cases)
+        assume "i > subdegree F"
+        hence "fps_nth (G ^ i) N = 0"
+          using i \<open>subdegree G > 0\<close> by (intro fps_pow_nth_below_subdegree) (auto simp: N_def)
+        thus ?thesis by simp
+      qed (use i in \<open>auto simp: N_def\<close>)
+    qed (use \<open>subdegree G > 0\<close> in \<open>auto simp: N_def\<close>)
+    also have "\<dots> = fps_nth F (subdegree F) * fps_nth (G ^ subdegree F) N"
+      by simp
+    also have "\<dots> \<noteq> 0"
+      using \<open>G \<noteq> 0\<close> \<open>F \<noteq> 0\<close> by (auto simp: N_def)
+    finally show False using * by auto
+  qed
+qed auto
+
+lemma fls_compose_fps_eq_0_iff:
+  assumes "H \<noteq> 0" "fps_nth H 0 = 0"
+  shows   "fls_compose_fps F H = 0 \<longleftrightarrow> F = 0"
+  using assms fls_base_factor_to_fps_nonzero[of F]
+  by (cases "F = 0") (auto simp: fls_compose_fps_def fps_compose_eq_0_iff)
+
+lemma fls_compose_fps_inverse:
+  assumes [simp]: "H \<noteq> 0" "fps_nth H 0 = 0"
+  shows   "fls_compose_fps (inverse F) H = inverse (fls_compose_fps F H)"
+proof (cases "F = 0")
+  case False
+  have "fls_compose_fps (inverse F) H * fls_compose_fps F H =
+        fls_compose_fps (inverse F * F) H"
+    by (subst fls_compose_fps_mult) auto
+  also have "inverse F * F = 1"
+    using False by simp
+  finally show ?thesis
+    using False by (simp add: field_simps fls_compose_fps_eq_0_iff)
+qed auto
+
+lemma fls_compose_fps_divide:
+  assumes [simp]: "H \<noteq> 0" "fps_nth H 0 = 0"
+  shows   "fls_compose_fps (F / G) H = fls_compose_fps F H / fls_compose_fps G H"
+  using fls_compose_fps_mult[of H F "inverse G"] fls_compose_fps_inverse[of H G]
+  by (simp add: field_simps)
+
+lemma fls_compose_fps_powi:
+  assumes [simp]: "H \<noteq> 0" "fps_nth H 0 = 0"
+  shows   "fls_compose_fps (F powi n) H = fls_compose_fps F H powi n"
+  by (simp add: power_int_def fls_compose_fps_power fls_compose_fps_inverse)
+
+lemma fls_compose_fps_assoc:
+  assumes [simp]: "G \<noteq> 0" "fps_nth G 0 = 0" "H \<noteq> 0" "fps_nth H 0 = 0"
+  shows "fls_compose_fps (fls_compose_fps F G) H = fls_compose_fps F (fps_compose G H)"
+proof (cases "F = 0")
+  case [simp]: False
+  define n where "n = fls_subdegree F"
+  define F' where "F' = fls_regpart (fls_shift n F)"
+  have F_eq: "F = fls_shift (-n) (fps_to_fls F')"
+    by (simp add: F'_def n_def)
+  show ?thesis
+    by (simp add: F_eq fls_compose_fps_shift fls_compose_fps_mult fls_compose_fps_powi
+                  fps_compose_eq_0_iff fps_compose_assoc)
+qed auto
+
+lemma subdegree_pos_iff: "subdegree F > 0 \<longleftrightarrow> F \<noteq> 0 \<and> fps_nth F 0 = 0"
+  using subdegree_eq_0_iff[of F] by auto
+
+lemma has_fps_expansion_fps_to_fls:
+  assumes "f has_laurent_expansion fps_to_fls F"
+  shows   "(\<lambda>z. if z = 0 then fps_nth F 0 else f z) has_fps_expansion F"
+  (is "?f' has_fps_expansion _")
+proof -
+  have "f has_laurent_expansion fps_to_fls F \<longleftrightarrow> ?f' has_laurent_expansion fps_to_fls F"
+    by (intro has_laurent_expansion_cong) (auto simp: eventually_at_filter)
+  with assms show ?thesis
+    by (auto simp: has_fps_expansion_to_laurent)
+qed
+
+
+lemma has_laurent_expansion_compose [laurent_expansion_intros]:
+  fixes f g :: "complex \<Rightarrow> complex"
+  assumes F: "f has_laurent_expansion F"
+  assumes G: "g has_laurent_expansion fps_to_fls G" "fps_nth G 0 = 0" "G \<noteq> 0"
+  shows   "(f \<circ> g) has_laurent_expansion fls_compose_fps F G"
+proof -
+  from assms have lim_g: "g \<midarrow>0\<rightarrow> 0"
+    by (subst tendsto_0_subdegree_iff_0[OF G(1)])
+       (auto simp: fls_subdegree_fls_to_fps subdegree_pos_iff)
+  have ev1: "eventually (\<lambda>z. g z \<noteq> 0) (at 0)"
+    using \<open>G \<noteq> 0\<close> G(1) fps_to_fls_eq_0_iff has_laurent_expansion_fps
+           has_laurent_expansion_nonzero_imp_eventually_nonzero by blast
+  moreover have "eventually (\<lambda>z. z \<noteq> 0) (at (0 :: complex))"
+    by (auto simp: eventually_at_filter)
+  ultimately have ev: "eventually (\<lambda>z. z \<noteq> 0 \<and> g z \<noteq> 0) (at 0)"
+    by eventually_elim blast
+  from ev1 and lim_g have lim_g': "filterlim g (at 0) (at 0)"
+    by (auto simp: filterlim_at)
+  define g' where "g' = (\<lambda>z. if z = 0 then fps_nth G 0 else g z)"
+
+  show ?thesis
+  proof (cases "F = 0")
+    assume [simp]: "F = 0"
+    have "eventually (\<lambda>z. f z = 0) (at 0)"
+      using F by (auto simp: has_laurent_expansion_def)
+    hence "eventually (\<lambda>z. f (g z) = 0) (at 0)"
+      using lim_g' by (rule eventually_compose_filterlim)
+    thus ?thesis
+      by (auto simp: has_laurent_expansion_def)
+  next
+    assume [simp]: "F \<noteq> 0"
+    define n where "n = fls_subdegree F"
+    define f' where
+      "f' = (\<lambda>z. if z = 0 then fps_nth (fls_base_factor_to_fps F) 0 else f z * z powi -n)"
+    have "((\<lambda>z. (f' \<circ> g') z * g z powi n)) has_laurent_expansion fls_compose_fps F G"
+      unfolding f'_def n_def fls_compose_fps_def g'_def
+      by (intro fps_expansion_intros laurent_expansion_intros has_fps_expansion_fps_to_fls
+                has_fps_expansion_fls_base_factor_to_fps assms has_laurent_expansion_fps)
+    also have "?this \<longleftrightarrow> ?thesis"
+      by (intro has_laurent_expansion_cong eventually_mono[OF ev])
+         (auto simp: f'_def power_int_minus g'_def)
+    finally show ?thesis .
+  qed
+qed
+
+lemma has_laurent_expansion_fls_X_inv [laurent_expansion_intros]:
+  "inverse has_laurent_expansion fls_X_inv"
+  using has_laurent_expansion_inverse[OF has_laurent_expansion_fps_X]
+  by (simp add: fls_inverse_X)
+
+lemma fls_X_power_int [simp]: "fls_X powi n = (fls_X_intpow n :: 'a :: division_ring fls)"
+  by (auto simp: power_int_def fls_X_power_conv_shift_1 fls_inverse_X fls_inverse_shift
+           simp flip: fls_inverse_X_power)
+
+lemma fls_const_power_int: "fls_const (c powi n) = fls_const (c :: 'a :: division_ring) powi n"
+  by (auto simp: power_int_def fls_const_power fls_inverse_const)
+
+lemma fls_nth_fls_compose_fps_linear:
+  fixes c :: "'a :: field"
+  assumes [simp]: "c \<noteq> 0"
+  shows "fls_nth (fls_compose_fps F (fps_const c * fps_X)) n = fls_nth F n * c powi n"
+proof -
+  {
+    assume *: "n \<ge> fls_subdegree F"
+    hence "c ^ nat (n - fls_subdegree F) = c powi int (nat (n - fls_subdegree F))"
+      by (simp add: power_int_def)
+    also have "\<dots> * c powi fls_subdegree F = c powi (int (nat (n - fls_subdegree F)) + fls_subdegree F)"
+      using * by (subst power_int_add) auto
+    also have "\<dots> = c powi n"
+      using * by simp
+    finally have "c ^ nat (n - fls_subdegree F) * c powi fls_subdegree F = c powi n" .
+  }
+  thus ?thesis
+    by (simp add: fls_compose_fps_def fps_compose_linear fls_times_fps_to_fls power_int_mult_distrib
+                  fls_shifted_times_simps
+             flip: fls_const_power_int)
+qed
+
+lemma zorder_times_analytic:
+  assumes "f analytic_on {z}" "g analytic_on {z}"
+  assumes "eventually (\<lambda>z. f z * g z \<noteq> 0) (at z)"
+  shows   "zorder (\<lambda>z. f z * g z) z = zorder f z + zorder g z"
+proof -
+  have *: "(\<lambda>w. f (z + w)) has_fps_expansion fps_expansion f z"
+          "(\<lambda>w. g (z + w)) has_fps_expansion fps_expansion g z"
+          "(\<lambda>w. f (z + w) * g (z + w)) has_fps_expansion fps_expansion f z * fps_expansion g z"
+    by (intro fps_expansion_intros analytic_at_imp_has_fps_expansion assms)+
+  have [simp]: "fps_expansion f z \<noteq> 0"
+  proof
+    assume "fps_expansion f z = 0"
+    hence "eventually (\<lambda>z. f z * g z = 0) (at z)" using *(1)
+      by (auto simp: has_fps_expansion_0_iff nhds_to_0' eventually_filtermap eventually_at_filter
+               elim: eventually_mono)
+    with assms(3) have "eventually (\<lambda>z. False) (at z)"
+      by eventually_elim auto
+    thus False by simp
+  qed
+  have [simp]: "fps_expansion g z \<noteq> 0"
+  proof
+    assume "fps_expansion g z = 0"
+    hence "eventually (\<lambda>z. f z * g z = 0) (at z)" using *(2)
+      by (auto simp: has_fps_expansion_0_iff nhds_to_0' eventually_filtermap eventually_at_filter
+               elim: eventually_mono)
+    with assms(3) have "eventually (\<lambda>z. False) (at z)"
+      by eventually_elim auto
+    thus False by simp
+  qed
+  from *[THEN has_fps_expansion_zorder] show ?thesis
+    by auto
+qed
+
+lemma analytic_on_prod [analytic_intros]:
+  assumes "\<And>x. x \<in> A \<Longrightarrow> f x analytic_on B"
+  shows   "(\<lambda>z. \<Prod>x\<in>A. f x z) analytic_on B"
+  using assms by (induction A rule: infinite_finite_induct) (auto intro!: analytic_intros)
+
+lemma zorder_const [simp]: "c \<noteq> 0 \<Longrightarrow> zorder (\<lambda>_. c) z = 0"
+  by (intro zorder_eqI[where s = UNIV]) auto
+
+lemma zorder_prod_analytic:
+  assumes "\<And>x. x \<in> A \<Longrightarrow> f x analytic_on {z}"
+  assumes "eventually (\<lambda>z. (\<Prod>x\<in>A. f x z) \<noteq> 0) (at z)"
+  shows   "zorder (\<lambda>z. \<Prod>x\<in>A. f x z) z = (\<Sum>x\<in>A. zorder (f x) z)"
+  using assms
+proof (induction A rule: infinite_finite_induct)
+  case (insert x A)
+  have "zorder (\<lambda>z. f x z * (\<Prod>x\<in>A. f x z)) z = zorder (f x) z + zorder (\<lambda>z. \<Prod>x\<in>A. f x z) z"
+    using insert.prems insert.hyps by (intro zorder_times_analytic analytic_intros) auto
+  also have "zorder (\<lambda>z. \<Prod>x\<in>A. f x z) z = (\<Sum>x\<in>A. zorder (f x) z)"
+    using insert.prems insert.hyps by (intro insert.IH) (auto elim!: eventually_mono)
+  finally show ?case using insert
+    by simp
+qed auto
+
+lemma zorder_eq_0I:
+  assumes "g analytic_on {z}" "g z \<noteq> 0"
+  shows   "zorder g z = 0"
+proof -
+  from assms obtain r where r: "r > 0" "g holomorphic_on ball z r"
+    unfolding analytic_on_def by blast
+  thus ?thesis using assms
+    by (intro zorder_eqI[of "ball z r" _ g]) auto
+qed
+
+lemma zorder_pos_iff:
+  assumes "f holomorphic_on A" "open A" "z \<in> A" "frequently (\<lambda>z. f z \<noteq> 0) (at z)"
+  shows   "zorder f z > 0 \<longleftrightarrow> f z = 0"
+proof -
+  have "f analytic_on {z}"
+    using assms analytic_at by blast
+  hence *: "(\<lambda>w. f (z + w)) has_fps_expansion fps_expansion f z"
+    using analytic_at_imp_has_fps_expansion by blast
+  have nz: "fps_expansion f z \<noteq> 0"
+  proof
+    assume "fps_expansion f z = 0"
+    hence "eventually (\<lambda>z. f z = 0) (nhds z)"
+      using * by (auto simp: has_fps_expansion_def nhds_to_0' eventually_filtermap add_ac)
+    hence "eventually (\<lambda>z. f z = 0) (at z)"
+      by (auto simp: eventually_at_filter elim: eventually_mono)
+    with assms show False
+      by (auto simp: frequently_def)
+  qed
+  from has_fps_expansion_zorder[OF * this] have eq: "zorder f z = int (subdegree (fps_expansion f z))"
+    by auto
+  moreover have "subdegree (fps_expansion f z) = 0 \<longleftrightarrow> fps_nth (fps_expansion f z) 0 \<noteq> 0"
+    using nz by (auto simp: subdegree_eq_0_iff)
+  moreover have "fps_nth (fps_expansion f z) 0 = f z"
+    by (auto simp: fps_expansion_def)
+  ultimately show ?thesis
+    by auto
+qed
+
+lemma zorder_pos_iff':
+  assumes "f analytic_on {z}" "frequently (\<lambda>z. f z \<noteq> 0) (at z)"
+  shows   "zorder f z > 0 \<longleftrightarrow> f z = 0"
+proof -
+  from assms(1) obtain A where A: "open A" "{z} \<subseteq> A" "f holomorphic_on A"
+    unfolding analytic_on_holomorphic by auto
+  with zorder_pos_iff [OF A(3,1), of z] assms show ?thesis
+    by auto
+qed
+
+lemma zorder_ge_0:
+  assumes "f analytic_on {z}" "frequently (\<lambda>z. f z \<noteq> 0) (at z)"
+  shows   "zorder f z \<ge> 0"
+proof -
+  have *: "(\<lambda>w. f (z + w)) has_laurent_expansion fps_to_fls (fps_expansion f z)"
+    using assms by (simp add: analytic_at_imp_has_fps_expansion has_laurent_expansion_fps)
+  from * assms(2) have "fps_to_fls (fps_expansion f z) \<noteq> 0"
+    by (auto simp: has_laurent_expansion_def frequently_def at_to_0' eventually_filtermap add_ac)
+  with has_laurent_expansion_zorder[OF *] show ?thesis
+    by (simp add: fls_subdegree_fls_to_fps)
+qed
+
+lemma zorder_eq_0_iff:
+  assumes "f analytic_on {z}" "frequently (\<lambda>w. f w \<noteq> 0) (at z)"
+  shows   "zorder f z = 0 \<longleftrightarrow> f z \<noteq> 0"
+proof
+  assume "f z \<noteq> 0"
+  thus "zorder f z = 0"
+    using assms zorder_eq_0I by blast
+next
+  assume "zorder f z = 0"
+  thus "f z \<noteq> 0"
+    using assms zorder_pos_iff' by fastforce
+qed
+
+lemma dist_mult_left:
+  "dist (a * b) (a * c :: 'a :: real_normed_field) = norm a * dist b c"
+  unfolding dist_norm right_diff_distrib [symmetric] norm_mult by simp
+
+lemma dist_mult_right:
+  "dist (b * a) (c * a :: 'a :: real_normed_field) = norm a * dist b c"
+  using dist_mult_left[of a b c] by (simp add: mult_ac)
+
+lemma zorder_scale:
+  assumes "f analytic_on {a * z}" "eventually (\<lambda>w. f w \<noteq> 0) (at (a * z))" "a \<noteq> 0"
+  shows "zorder (\<lambda>w. f (a * w)) z = zorder f (a * z)"
+proof -
+  from assms(1) obtain r where r: "r > 0" "f holomorphic_on ball (a * z) r"
+    by (auto simp: analytic_on_def)
+  have *: "open (ball (a * z) r)" "connected (ball (a * z) r)" "a * z \<in> ball (a * z) r"
+    using r \<open>a \<noteq> 0\<close> by (auto simp: dist_norm)
+  from assms(2) have "eventually (\<lambda>w. f w \<noteq> 0 \<and> w \<in> ball (a * z) r - {a * z}) (at (a * z))"
+    using \<open>r > 0\<close> by (intro eventually_conj eventually_at_in_open) auto
+  then obtain z0 where "f z0 \<noteq> 0 \<and> z0 \<in> ball (a * z) r - {a * z}"
+    using eventually_happens[of _ "at (a * z)"] by force
+  hence **: "\<exists>w\<in>ball (a * z) r. f w \<noteq> 0"
+    by blast
+
+  define n where "n = nat (zorder f (a * z))"
+  obtain r' where r':
+     "(if f (a * z) = 0 then 0 < zorder f (a * z) else zorder f (a * z) = 0)"
+     "r' > 0" "cball (a * z) r' \<subseteq> ball (a * z) r" "zor_poly f (a * z) holomorphic_on cball (a * z) r'"
+     "\<And>w. w \<in> cball (a * z) r' \<Longrightarrow>
+        f w = zor_poly f (a * z) w * (w - a * z) ^ n \<and> zor_poly f (a * z) w \<noteq> 0"
+    unfolding n_def using zorder_exist_zero[OF r(2) * **] by blast
+
+  show ?thesis
+  proof (rule zorder_eqI)
+    show "open (ball z (r' / norm a))" "z \<in> ball z (r' / norm a)"
+      using r \<open>r' > 0\<close> \<open>a \<noteq> 0\<close> by auto
+    have "(*) a ` ball z (r' / cmod a) \<subseteq> cball (a * z) r'"
+    proof safe
+      fix w assume "w \<in> ball z (r' / cmod a)"
+      thus "a * w \<in> cball (a * z) r'"
+        using dist_mult_left[of a z w] \<open>a \<noteq> 0\<close> by (auto simp: divide_simps mult_ac)
+    qed
+    thus "(\<lambda>w. a ^ n * (zor_poly f (a * z) \<circ> (\<lambda>w. a * w)) w) holomorphic_on ball z (r' / norm a)"
+      using \<open>a \<noteq> 0\<close> by (intro holomorphic_on_compose_gen[OF _ r'(4)] holomorphic_intros) auto
+    show "a ^ n * (zor_poly f (a * z) \<circ> (\<lambda>w. a * w)) z \<noteq> 0"
+      using r' \<open>a \<noteq> 0\<close> by auto
+    show "f (a * w) = a ^ n * (zor_poly f (a * z) \<circ> (*) a) w * (w - z) powr of_int (zorder f (a * z))"
+      if "w \<in> ball z (r' / norm a)" "w \<noteq> z" for w
+    proof -
+      have "f (a * w) = zor_poly f (a * z) (a * w) * (a * (w - z)) ^ n"
+        using that r'(5)[of "a * w"] dist_mult_left[of a z w] \<open>a \<noteq> 0\<close> unfolding ring_distribs
+        by (auto simp: divide_simps mult_ac)
+      also have "\<dots> = a ^ n * zor_poly f (a * z) (a * w) * (w - z) ^ n"
+        by (subst power_mult_distrib) (auto simp: mult_ac)
+      also have "(w - z) ^ n = (w - z) powr of_nat n"
+        using \<open>w \<noteq> z\<close> by (subst powr_nat') auto
+      also have "of_nat n = of_int (zorder f (a * z))"
+        using r'(1) by (auto simp: n_def split: if_splits)
+      finally show ?thesis
+        unfolding o_def n_def .
+    qed
+  qed
+qed
+
+lemma subdegree_fps_compose [simp]:
+  fixes F G :: "'a :: idom fps"
+  assumes [simp]: "fps_nth G 0 = 0"
+  shows "subdegree (fps_compose F G) = subdegree F * subdegree G"
+proof (cases "G = 0"; cases "F = 0")
+  assume [simp]: "G \<noteq> 0" "F \<noteq> 0"
+  define m where "m = subdegree F"
+  define F' where "F' = fps_shift m F"
+  have F_eq: "F = F' * fps_X ^ m"
+    unfolding F'_def by (simp add: fps_shift_times_fps_X_power m_def)
+  have [simp]: "F' \<noteq> 0"
+    using \<open>F \<noteq> 0\<close> unfolding F_eq by auto
+  have "subdegree (fps_compose F G) = subdegree (fps_compose F' G) + m * subdegree G"
+    by (simp add: F_eq fps_compose_mult_distrib fps_compose_eq_0_iff flip: fps_compose_power)
+  also have "subdegree (fps_compose F' G) = 0"
+    by (intro subdegree_eq_0) (auto simp: F'_def m_def)
+  finally show ?thesis by (simp add: m_def)
+qed auto
+
+lemma fls_subdegree_power_int [simp]:
+  fixes   F :: "'a :: field fls"
+  shows "fls_subdegree (F powi n) = n * fls_subdegree F"
+  by (auto simp: power_int_def fls_subdegree_pow)
+
+lemma subdegree_fls_compose_fps [simp]:
+  fixes G :: "'a :: field fps"
+  assumes [simp]: "fps_nth G 0 = 0"
+  shows "fls_subdegree (fls_compose_fps F G) = fls_subdegree F * subdegree G"
+proof (cases "F = 0"; cases "G = 0")
+  assume [simp]: "G \<noteq> 0" "F \<noteq> 0"
+  have nz1: "fls_base_factor_to_fps F \<noteq> 0"
+    using \<open>F \<noteq> 0\<close> fls_base_factor_to_fps_nonzero by blast
+  show ?thesis
+    unfolding fls_compose_fps_def using nz1
+    by (subst fls_subdegree_mult) (simp_all add: fps_compose_eq_0_iff fls_subdegree_fls_to_fps)
+qed (auto simp: fls_compose_fps_0_right)
+
+lemma zorder_compose_aux:
+  assumes "isolated_singularity_at f 0" "not_essential f 0"
+  assumes G: "g has_fps_expansion G" "G \<noteq> 0" "g 0 = 0"
+  assumes "eventually (\<lambda>w. f w \<noteq> 0) (at 0)"
+  shows   "zorder (f \<circ> g) 0 = zorder f 0 * subdegree G"
+proof -
+  obtain F where F: "f has_laurent_expansion F"
+    using not_essential_has_laurent_expansion_0[OF assms(1,2)] by blast
+  have [simp]: "fps_nth G 0 = 0"
+   using G \<open>g 0 = 0\<close> by (simp add: has_fps_expansion_imp_0_eq_fps_nth_0)
+  note [simp] = \<open>G \<noteq> 0\<close> \<open>g 0 = 0\<close>
+  have [simp]: "F \<noteq> 0"
+    using has_laurent_expansion_eventually_nonzero_iff[of f 0 F] F assms by simp
+  have FG: "(f \<circ> g) has_laurent_expansion fls_compose_fps F G"
+    by (intro has_laurent_expansion_compose has_laurent_expansion_fps F G) auto
+
+  have "zorder (f \<circ> g) 0 = fls_subdegree (fls_compose_fps F G)"
+    using has_laurent_expansion_zorder_0 [OF FG] by (auto simp: fls_compose_fps_eq_0_iff)
+  also have "\<dots> = fls_subdegree F * int (subdegree G)"
+    by simp
+  also have "fls_subdegree F = zorder f 0"
+    using has_laurent_expansion_zorder_0 [OF F] by auto
+  finally show ?thesis .
+qed
+
+lemma zorder_compose:
+  assumes "isolated_singularity_at f (g z)" "not_essential f (g z)"
+  assumes G: "(\<lambda>x. g (z + x) - g z) has_fps_expansion G" "G \<noteq> 0"
+  assumes "eventually (\<lambda>w. f w \<noteq> 0) (at (g z))"
+  shows   "zorder (f \<circ> g) z = zorder f (g z) * subdegree G"
+proof -
+  define f' where "f' = (\<lambda>w. f (g z + w))"
+  define g' where "g' = (\<lambda>w. g (z + w) - g z)"
+  have "zorder f (g z) = zorder f' 0"
+    by (simp add: f'_def zorder_shift' add_ac)
+  have "zorder (\<lambda>x. g x - g z) z = zorder g' 0"
+    by (simp add: g'_def zorder_shift' add_ac)
+  have "zorder (f \<circ> g) z = zorder (f' \<circ> g') 0"
+    by (simp add: zorder_shift' f'_def g'_def add_ac o_def)
+  also have "\<dots> = zorder f' 0 * int (subdegree G)"
+  proof (rule zorder_compose_aux)
+    show "isolated_singularity_at f' 0" unfolding f'_def
+      using assms has_laurent_expansion_isolated_0 not_essential_has_laurent_expansion by blast
+    show "not_essential f' 0" unfolding f'_def
+      using assms has_laurent_expansion_not_essential_0 not_essential_has_laurent_expansion by blast
+  qed (use assms in \<open>auto simp: f'_def g'_def at_to_0' eventually_filtermap add_ac\<close>)
+  also have "zorder f' 0 = zorder f (g z)"
+    by (simp add: f'_def zorder_shift' add_ac)
+  finally show ?thesis .
+qed
+
+lemma fps_to_fls_eq_fls_const_iff [simp]: "fps_to_fls F = fls_const c \<longleftrightarrow> F = fps_const c"
+proof
+  assume "F = fps_const c"
+  thus "fps_to_fls F = fls_const c"
+    by simp
+next
+  assume "fps_to_fls F = fls_const c"
+  thus "F = fps_const c"
+    by (metis fls_regpart_const fls_regpart_fps_trivial)
+qed
+
+lemma zorder_compose':
+  assumes "isolated_singularity_at f (g z)" "not_essential f (g z)"
+  assumes "g analytic_on {z}"
+  assumes "eventually (\<lambda>w. f w \<noteq> 0) (at (g z))"
+  assumes "eventually (\<lambda>w. g w \<noteq> g z) (at z)"
+  shows   "zorder (f \<circ> g) z = zorder f (g z) * zorder (\<lambda>x. g x - g z) z"
+proof -
+  obtain G where G [fps_expansion_intros]: "(\<lambda>x. g (z + x)) has_fps_expansion G"
+    using assms analytic_at_imp_has_fps_expansion by blast
+  have G': "(\<lambda>x. g (z + x) - g z) has_fps_expansion G - fps_const (g z)"
+    by (intro fps_expansion_intros)
+  hence G'': "(\<lambda>x. g (z + x) - g z) has_laurent_expansion fps_to_fls (G - fps_const (g z))"
+    using has_laurent_expansion_fps by blast
+  have nz: "G - fps_const (g z) \<noteq> 0"
+    using has_laurent_expansion_eventually_nonzero_iff[OF G''] assms by auto
+  have "zorder (f \<circ> g) z = zorder f (g z) * subdegree (G - fps_const (g z))"
+  proof (rule zorder_compose)
+    show "(\<lambda>x. g (z + x) - g z) has_fps_expansion G - fps_const (g z)"
+      by (intro fps_expansion_intros)
+  qed (use assms nz in auto)
+  also have "int (subdegree (G - fps_const (g z))) = fls_subdegree (fps_to_fls G - fls_const (g z))"
+    by (simp flip: fls_subdegree_fls_to_fps)
+  also have "\<dots> = zorder (\<lambda>x. g x - g z) z"
+    using has_laurent_expansion_zorder [OF G''] nz by auto
+  finally show ?thesis .
+qed
+
+lemma analytic_at_cong:
+  assumes "eventually (\<lambda>x. f x = g x) (nhds x)" "x = y"
+  shows "f analytic_on {x} \<longleftrightarrow> g analytic_on {y}"
+proof -
+  have "g analytic_on {x}" if "f analytic_on {x}" "eventually (\<lambda>x. f x = g x) (nhds x)" for f g
+  proof -
+    have "(\<lambda>y. f (x + y)) has_fps_expansion fps_expansion f x"
+      by (rule analytic_at_imp_has_fps_expansion) fact
+    also have "?this \<longleftrightarrow> (\<lambda>y. g (x + y)) has_fps_expansion fps_expansion f x"
+      using that by (intro has_fps_expansion_cong refl) (auto simp: nhds_to_0' eventually_filtermap)
+    finally show ?thesis
+      by (rule has_fps_expansion_imp_analytic)
+  qed
+  from this[of f g] this[of g f] show ?thesis using assms
+    by (auto simp: eq_commute)
+qed
+
+
+lemma has_laurent_expansion_sin' [laurent_expansion_intros]:
+  "sin has_laurent_expansion fps_to_fls (fps_sin 1)"
+  using has_fps_expansion_sin' has_fps_expansion_to_laurent by blast
+
+lemma has_laurent_expansion_cos' [laurent_expansion_intros]:
+  "cos has_laurent_expansion fps_to_fls (fps_cos 1)"
+  using has_fps_expansion_cos' has_fps_expansion_to_laurent by blast
+
+lemma has_laurent_expansion_sin [laurent_expansion_intros]:
+  "(\<lambda>z. sin (c * z)) has_laurent_expansion fps_to_fls (fps_sin c)"
+  by (intro has_laurent_expansion_fps has_fps_expansion_sin)
+
+lemma has_laurent_expansion_cos [laurent_expansion_intros]:
+  "(\<lambda>z. cos (c * z)) has_laurent_expansion fps_to_fls (fps_cos c)"
+  by (intro has_laurent_expansion_fps has_fps_expansion_cos)
+
+lemma has_laurent_expansion_tan' [laurent_expansion_intros]:
+  "tan has_laurent_expansion fps_to_fls (fps_tan 1)"
+  using has_fps_expansion_tan' has_fps_expansion_to_laurent by blast
+
+lemma has_laurent_expansion_tan [laurent_expansion_intros]:
+  "(\<lambda>z. tan (c * z)) has_laurent_expansion fps_to_fls (fps_tan c)"
+  by (intro has_laurent_expansion_fps has_fps_expansion_tan)
+
+end
diff -r 29032b496f2e -r c6b50597abbc src/HOL/Complex_Analysis/Meromorphic.thy
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/Complex_Analysis/Meromorphic.thy	Thu Feb 16 12:21:21 2023 +0000
@@ -0,0 +1,2333 @@
+theory Meromorphic
+  imports Laurent_Convergence Riemann_Mapping
+begin
+
+lemma analytic_at_cong:
+  assumes "eventually (\<lambda>x. f x = g x) (nhds x)" "x = y"
+  shows "f analytic_on {x} \<longleftrightarrow> g analytic_on {y}"
+proof -
+  have "g analytic_on {x}" if "f analytic_on {x}" "eventually (\<lambda>x. f x = g x) (nhds x)" for f g
+  proof -
+    have "(\<lambda>y. f (x + y)) has_fps_expansion fps_expansion f x"
+      by (rule analytic_at_imp_has_fps_expansion) fact
+    also have "?this \<longleftrightarrow> (\<lambda>y. g (x + y)) has_fps_expansion fps_expansion f x"
+      using that by (intro has_fps_expansion_cong refl) (auto simp: nhds_to_0' eventually_filtermap)
+    finally show ?thesis
+      by (rule has_fps_expansion_imp_analytic)
+  qed
+  from this[of f g] this[of g f] show ?thesis using assms
+    by (auto simp: eq_commute)
+qed
+
+definition remove_sings :: "(complex \<Rightarrow> complex) \<Rightarrow> complex \<Rightarrow> complex" where
+  "remove_sings f z = (if \<exists>c. f \<midarrow>z\<rightarrow> c then Lim (at z) f else 0)"
+
+lemma remove_sings_eqI [intro]:
+  assumes "f \<midarrow>z\<rightarrow> c"
+  shows   "remove_sings f z = c"
+  using assms unfolding remove_sings_def by (auto simp: tendsto_Lim)
+
+lemma remove_sings_at_analytic [simp]:
+  assumes "f analytic_on {z}"
+  shows   "remove_sings f z = f z"
+  using assms by (intro remove_sings_eqI) (simp add: analytic_at_imp_isCont isContD)
+
+lemma remove_sings_at_pole [simp]:
+  assumes "is_pole f z"
+  shows   "remove_sings f z = 0"
+  using assms unfolding remove_sings_def is_pole_def
+  by (meson at_neq_bot not_tendsto_and_filterlim_at_infinity)
+
+lemma eventually_remove_sings_eq_at:
+  assumes "isolated_singularity_at f z"
+  shows   "eventually (\<lambda>w. remove_sings f w = f w) (at z)"
+proof -
+  from assms obtain r where r: "r > 0" "f analytic_on ball z r - {z}"
+    by (auto simp: isolated_singularity_at_def)
+  hence *: "f analytic_on {w}" if "w \<in> ball z r - {z}" for w
+    using r that by (auto intro: analytic_on_subset)
+  have "eventually (\<lambda>w. w \<in> ball z r - {z}) (at z)"
+    using r by (intro eventually_at_in_open) auto
+  thus ?thesis
+    by eventually_elim (auto simp: remove_sings_at_analytic *)
+qed
+
+lemma eventually_remove_sings_eq_nhds:
+  assumes "f analytic_on {z}"
+  shows   "eventually (\<lambda>w. remove_sings f w = f w) (nhds z)"
+proof -
+  from assms obtain A where A: "open A" "z \<in> A" "f holomorphic_on A"
+    by (auto simp: analytic_at)
+  have "eventually (\<lambda>z. z \<in> A) (nhds z)"
+    by (intro eventually_nhds_in_open A)
+  thus ?thesis
+  proof eventually_elim
+    case (elim w)
+    from elim have "f analytic_on {w}"
+      using A analytic_at by blast
+    thus ?case by auto
+  qed
+qed
+
+lemma remove_sings_compose:
+  assumes "filtermap g (at z) = at z'"
+  shows   "remove_sings (f \<circ> g) z = remove_sings f z'"
+proof (cases "\<exists>c. f \<midarrow>z'\<rightarrow> c")
+  case True
+  then obtain c where c: "f \<midarrow>z'\<rightarrow> c"
+    by auto
+  from c have "remove_sings f z' = c"
+    by blast
+  moreover from c have "remove_sings (f \<circ> g) z = c"
+    using c by (intro remove_sings_eqI) (auto simp: filterlim_def filtermap_compose assms)
+  ultimately show ?thesis
+    by simp
+next
+  case False
+  hence "\<not>(\<exists>c. (f \<circ> g) \<midarrow>z\<rightarrow> c)"
+    by (auto simp: filterlim_def filtermap_compose assms)
+  with False show ?thesis
+    by (auto simp: remove_sings_def)
+qed
+
+lemma remove_sings_cong:
+  assumes "eventually (\<lambda>x. f x = g x) (at z)" "z = z'"
+  shows   "remove_sings f z = remove_sings g z'"
+proof (cases "\<exists>c. f \<midarrow>z\<rightarrow> c")
+  case True
+  then obtain c where c: "f \<midarrow>z\<rightarrow> c" by blast
+  hence "remove_sings f z = c"
+    by blast
+  moreover have "f \<midarrow>z\<rightarrow> c \<longleftrightarrow> g \<midarrow>z'\<rightarrow> c"
+    using assms by (intro filterlim_cong refl) auto
+  with c have "remove_sings g z' = c"
+    by (intro remove_sings_eqI) auto
+  ultimately show ?thesis
+    by simp
+next
+  case False
+  have "f \<midarrow>z\<rightarrow> c \<longleftrightarrow> g \<midarrow>z'\<rightarrow> c" for c
+    using assms by (intro filterlim_cong) auto
+  with False show ?thesis
+    by (auto simp: remove_sings_def)
+qed
+
+
+lemma deriv_remove_sings_at_analytic [simp]:
+  assumes "f analytic_on {z}"
+  shows   "deriv (remove_sings f) z = deriv f z"
+  apply (rule deriv_cong_ev)
+  apply (rule eventually_remove_sings_eq_nhds)
+  using assms by auto
+
+lemma isolated_singularity_at_remove_sings [simp, intro]:
+  assumes "isolated_singularity_at f z"
+  shows   "isolated_singularity_at (remove_sings f) z"
+  using isolated_singularity_at_cong[OF eventually_remove_sings_eq_at[OF assms] refl] assms
+  by simp
+
+lemma not_essential_remove_sings_iff [simp]:
+  assumes "isolated_singularity_at f z"
+  shows   "not_essential (remove_sings f) z \<longleftrightarrow> not_essential f z"
+  using not_essential_cong[OF eventually_remove_sings_eq_at[OF assms(1)] refl]
+  by simp
+
+lemma not_essential_remove_sings [intro]:
+  assumes "isolated_singularity_at f z" "not_essential f z"
+  shows   "not_essential (remove_sings f) z"
+  by (subst not_essential_remove_sings_iff) (use assms in auto)
+
+lemma
+  assumes "isolated_singularity_at f z"
+  shows is_pole_remove_sings_iff [simp]:
+        "is_pole (remove_sings f) z \<longleftrightarrow> is_pole f z"
+  and zorder_remove_sings [simp]:
+        "zorder (remove_sings f) z = zorder f z"
+  and zor_poly_remove_sings [simp]:
+        "zor_poly (remove_sings f) z = zor_poly f z"
+  and has_laurent_expansion_remove_sings_iff [simp]:
+        "(\<lambda>w. remove_sings f (z + w)) has_laurent_expansion F \<longleftrightarrow>
+         (\<lambda>w. f (z + w)) has_laurent_expansion F"
+  and tendsto_remove_sings_iff [simp]:
+        "remove_sings f \<midarrow>z\<rightarrow> c \<longleftrightarrow> f \<midarrow>z\<rightarrow> c"
+  by (intro is_pole_cong eventually_remove_sings_eq_at refl zorder_cong
+            zor_poly_cong has_laurent_expansion_cong' tendsto_cong assms)+
+
+lemma get_all_poles_from_remove_sings:
+  fixes f:: "complex \<Rightarrow> complex"
+  defines "ff\<equiv>remove_sings f"
+  assumes f_holo:"f holomorphic_on s - pts" and "finite pts" 
+    "pts\<subseteq>s" "open s" and not_ess:"\<forall>x\<in>pts. not_essential f x"
+  obtains pts' where 
+    "pts' \<subseteq> pts" "finite pts'" "ff holomorphic_on s - pts'" "\<forall>x\<in>pts'. is_pole ff x"
+proof -
+  define pts' where "pts' = {x\<in>pts. is_pole f x}"
+
+  have "pts' \<subseteq> pts" unfolding pts'_def by auto
+  then have "finite pts'" using \<open>finite pts\<close> 
+    using rev_finite_subset by blast
+  then have "open (s - pts')" using \<open>open s\<close>
+    by (simp add: finite_imp_closed open_Diff)
+
+  have isolated:"isolated_singularity_at f z" if "z\<in>pts" for z
+  proof (rule isolated_singularity_at_holomorphic)
+    show "f holomorphic_on (s-(pts-{z})) - {z}" 
+      by (metis Diff_insert f_holo insert_Diff that)
+    show " open (s - (pts - {z}))" 
+      by (meson assms(3) assms(5) finite_Diff finite_imp_closed open_Diff)
+    show "z \<in> s - (pts - {z})" 
+      using assms(4) that by auto
+  qed
+
+  have "ff holomorphic_on s - pts'"
+  proof (rule no_isolated_singularity')
+    show "(ff \<longlongrightarrow> ff z) (at z within s - pts')" if "z \<in> pts-pts'" for z
+    proof -
+      have "at z within s - pts' = at z"
+        apply (rule at_within_open)
+        using \<open>open (s - pts')\<close> that \<open>pts\<subseteq>s\<close>  by auto
+      moreover have "ff \<midarrow>z\<rightarrow> ff z"
+        unfolding ff_def
+      proof (subst tendsto_remove_sings_iff)
+        show "isolated_singularity_at f z"
+          apply (rule isolated)
+          using that by auto
+        have "not_essential f z" 
+          using not_ess that by auto
+        moreover have "\<not>is_pole f z"
+          using that unfolding pts'_def by auto
+        ultimately have "\<exists>c. f \<midarrow>z\<rightarrow> c" 
+          unfolding not_essential_def by auto
+        then show "f \<midarrow>z\<rightarrow> remove_sings f z"
+          using remove_sings_eqI by blast
+      qed
+      ultimately show ?thesis by auto
+    qed
+    have "ff holomorphic_on s - pts"
+      using f_holo 
+    proof (elim holomorphic_transform)
+      fix x assume "x \<in> s - pts"
+      then have "f analytic_on {x}" 
+        using assms(3) assms(5) f_holo
+        by (meson finite_imp_closed 
+            holomorphic_on_imp_analytic_at open_Diff) 
+      from remove_sings_at_analytic[OF this]
+      show "f x = ff x" unfolding ff_def by auto 
+    qed
+    then show "ff holomorphic_on s - pts' - (pts - pts')"
+      apply (elim holomorphic_on_subset)
+      by blast
+    show "open (s - pts')" 
+      by (simp add: \<open>open (s - pts')\<close>)
+    show "finite (pts - pts')" 
+      by (simp add: assms(3))
+  qed
+  moreover have "\<forall>x\<in>pts'. is_pole ff x"
+    unfolding pts'_def 
+    using ff_def is_pole_remove_sings_iff isolated by blast
+  moreover note \<open>pts' \<subseteq> pts\<close> \<open>finite pts'\<close> 
+  ultimately show ?thesis using that by auto
+qed
+
+lemma remove_sings_eq_0_iff:
+  assumes "not_essential f w"
+  shows "remove_sings f w = 0 \<longleftrightarrow> is_pole f w \<or> f \<midarrow>w\<rightarrow> 0"
+proof (cases "is_pole f w")
+  case True
+  then show ?thesis by simp
+next
+  case False
+  then obtain c where c:"f \<midarrow>w\<rightarrow> c"
+    using \<open>not_essential f w\<close> unfolding not_essential_def by auto
+  then show ?thesis 
+    using False remove_sings_eqI by auto
+qed
+
+definition meromorphic_on:: "[complex \<Rightarrow> complex, complex set, complex set] \<Rightarrow> bool" 
+  ("_ (meromorphic'_on) _ _" [50,50,50]50) where 
+  "f meromorphic_on D pts \<equiv> 
+     open D \<and> pts \<subseteq> D \<and> (\<forall>z\<in>pts. isolated_singularity_at f z \<and> not_essential f z) \<and>
+     (\<forall>z\<in>D. \<not>(z islimpt pts)) \<and> (f holomorphic_on D-pts)"
+
+lemma meromorphic_imp_holomorphic: "f meromorphic_on D pts \<Longrightarrow> f holomorphic_on (D - pts)"
+  unfolding meromorphic_on_def by auto
+
+lemma meromorphic_imp_closedin_pts:
+  assumes "f meromorphic_on D pts"
+  shows "closedin (top_of_set D) pts"
+  by (meson assms closedin_limpt meromorphic_on_def)
+
+lemma meromorphic_imp_open_diff':
+  assumes "f meromorphic_on D pts" "pts' \<subseteq> pts"
+  shows "open (D - pts')"
+proof -
+  have "D - pts' = D - closure pts'"
+  proof safe
+    fix x assume x: "x \<in> D" "x \<in> closure pts'" "x \<notin> pts'"
+    hence "x islimpt pts'"
+      by (subst islimpt_in_closure) auto
+    hence "x islimpt pts"
+      by (rule islimpt_subset) fact
+    with assms x show False
+      by (auto simp: meromorphic_on_def)
+  qed (use closure_subset in auto)
+  then show ?thesis
+    using assms meromorphic_on_def by auto
+qed
+
+lemma meromorphic_imp_open_diff: "f meromorphic_on D pts \<Longrightarrow> open (D - pts)"
+  by (erule meromorphic_imp_open_diff') auto
+
+lemma meromorphic_pole_subset:
+  assumes merf: "f meromorphic_on D pts" 
+  shows "{x\<in>D. is_pole f x} \<subseteq> pts"
+  by (smt (verit) Diff_iff assms mem_Collect_eq meromorphic_imp_open_diff 
+      meromorphic_on_def not_is_pole_holomorphic subsetI)
+
+named_theorems meromorphic_intros
+
+lemma meromorphic_on_subset:
+  assumes "f meromorphic_on A pts" "open B" "B \<subseteq> A" "pts' = pts \<inter> B"
+  shows   "f meromorphic_on B pts'"
+  unfolding meromorphic_on_def
+proof (intro ballI conjI)
+  fix z assume "z \<in> B"
+  show "\<not>z islimpt pts'"
+  proof
+    assume "z islimpt pts'"
+    hence "z islimpt pts"
+      by (rule islimpt_subset) (use \<open>pts' = _\<close> in auto)
+    thus False using \<open>z \<in> B\<close> \<open>B \<subseteq> A\<close> assms(1)
+      by (auto simp: meromorphic_on_def)
+  qed
+qed (use assms in \<open>auto simp: meromorphic_on_def\<close>)
+
+lemma meromorphic_on_superset_pts:
+  assumes "f meromorphic_on A pts" "pts \<subseteq> pts'" "pts' \<subseteq> A" "\<forall>x\<in>A. \<not>x islimpt pts'"
+  shows   "f meromorphic_on A pts'"
+  unfolding meromorphic_on_def
+proof (intro conjI ballI impI)
+  fix z assume "z \<in> pts'"
+  from assms(1) have holo: "f holomorphic_on A - pts" and "open A"
+    unfolding meromorphic_on_def by blast+
+  have "open (A - pts)"
+    by (intro meromorphic_imp_open_diff[OF assms(1)])
+
+  show "isolated_singularity_at f z"
+  proof (cases "z \<in> pts")
+    case False
+    thus ?thesis
+      using \<open>open (A - pts)\<close> assms \<open>z \<in> pts'\<close>
+      by (intro isolated_singularity_at_holomorphic[of _ "A - pts"] holomorphic_on_subset[OF holo])
+         auto
+  qed (use assms in \<open>auto simp: meromorphic_on_def\<close>)
+
+  show "not_essential f z"
+  proof (cases "z \<in> pts")
+    case False
+    thus ?thesis
+      using \<open>open (A - pts)\<close> assms \<open>z \<in> pts'\<close>
+      by (intro not_essential_holomorphic[of _ "A - pts"] holomorphic_on_subset[OF holo])
+         auto
+  qed (use assms in \<open>auto simp: meromorphic_on_def\<close>)
+qed (use assms in \<open>auto simp: meromorphic_on_def\<close>)
+
+lemma meromorphic_on_no_singularities: "f meromorphic_on A {} \<longleftrightarrow> f holomorphic_on A \<and> open A"
+  by (auto simp: meromorphic_on_def)
+
+lemma holomorphic_on_imp_meromorphic_on:
+  "f holomorphic_on A \<Longrightarrow> pts \<subseteq> A \<Longrightarrow> open A \<Longrightarrow> \<forall>x\<in>A. \<not>x islimpt pts \<Longrightarrow> f meromorphic_on A pts"
+  by (rule meromorphic_on_superset_pts[where pts = "{}"])
+     (auto simp: meromorphic_on_no_singularities)
+
+lemma meromorphic_on_const [meromorphic_intros]: 
+  assumes "open A" "\<forall>x\<in>A. \<not>x islimpt pts" "pts \<subseteq> A"
+  shows   "(\<lambda>_. c) meromorphic_on A pts"
+  by (rule holomorphic_on_imp_meromorphic_on) (use assms in auto)
+
+lemma meromorphic_on_ident [meromorphic_intros]:
+  assumes "open A" "\<forall>x\<in>A. \<not>x islimpt pts" "pts \<subseteq> A"
+  shows   "(\<lambda>x. x) meromorphic_on A pts"
+  by (rule holomorphic_on_imp_meromorphic_on) (use assms in auto)
+
+lemma meromorphic_on_id [meromorphic_intros]:
+  assumes "open A" "\<forall>x\<in>A. \<not>x islimpt pts" "pts \<subseteq> A"
+  shows   "id meromorphic_on A pts"
+  using meromorphic_on_ident assms unfolding id_def .
+
+lemma not_essential_add [singularity_intros]:
+  assumes f_ness: "not_essential f z" and g_ness: "not_essential g z"
+  assumes f_iso: "isolated_singularity_at f z" and g_iso: "isolated_singularity_at g z"
+  shows "not_essential (\<lambda>w. f w + g w) z"
+proof -
+  have "(\<lambda>w. f (z + w) + g (z + w)) has_laurent_expansion laurent_expansion f z + laurent_expansion g z"
+    by (intro not_essential_has_laurent_expansion laurent_expansion_intros assms)
+  hence "not_essential (\<lambda>w. f (z + w) + g (z + w)) 0"
+    using has_laurent_expansion_not_essential_0 by blast
+  thus ?thesis
+    by (simp add: not_essential_shift_0)
+qed
+
+lemma meromorphic_on_uminus [meromorphic_intros]:
+  assumes "f meromorphic_on A pts"
+  shows   "(\<lambda>z. -f z) meromorphic_on A pts"
+  unfolding meromorphic_on_def
+  by (use assms in \<open>auto simp: meromorphic_on_def intro!: holomorphic_intros singularity_intros\<close>)
+
+lemma meromorphic_on_add [meromorphic_intros]:
+  assumes "f meromorphic_on A pts" "g meromorphic_on A pts"
+  shows   "(\<lambda>z. f z + g z) meromorphic_on A pts"
+  unfolding meromorphic_on_def
+  by (use assms in \<open>auto simp: meromorphic_on_def intro!: holomorphic_intros singularity_intros\<close>)
+
+lemma meromorphic_on_add':
+  assumes "f meromorphic_on A pts1" "g meromorphic_on A pts2"
+  shows   "(\<lambda>z. f z + g z) meromorphic_on A (pts1 \<union> pts2)"
+proof (rule meromorphic_intros)
+  show "f meromorphic_on A (pts1 \<union> pts2)"
+    by (rule meromorphic_on_superset_pts[OF assms(1)])
+       (use assms in \<open>auto simp: meromorphic_on_def islimpt_Un\<close>)
+  show "g meromorphic_on A (pts1 \<union> pts2)"
+    by (rule meromorphic_on_superset_pts[OF assms(2)])
+       (use assms in \<open>auto simp: meromorphic_on_def islimpt_Un\<close>)
+qed
+
+lemma meromorphic_on_add_const [meromorphic_intros]:
+  assumes "f meromorphic_on A pts" 
+  shows   "(\<lambda>z. f z + c) meromorphic_on A pts"
+  unfolding meromorphic_on_def
+  by (use assms in \<open>auto simp: meromorphic_on_def intro!: holomorphic_intros singularity_intros\<close>)
+
+lemma meromorphic_on_minus_const [meromorphic_intros]:
+  assumes "f meromorphic_on A pts" 
+  shows   "(\<lambda>z. f z - c) meromorphic_on A pts"
+  using meromorphic_on_add_const[OF assms,of "-c"] by simp
+
+lemma meromorphic_on_diff [meromorphic_intros]:
+  assumes "f meromorphic_on A pts" "g meromorphic_on A pts"
+  shows   "(\<lambda>z. f z - g z) meromorphic_on A pts"
+  using meromorphic_on_add[OF assms(1) meromorphic_on_uminus[OF assms(2)]] by simp
+
+lemma meromorphic_on_diff':
+  assumes "f meromorphic_on A pts1" "g meromorphic_on A pts2"
+  shows   "(\<lambda>z. f z - g z) meromorphic_on A (pts1 \<union> pts2)"
+proof (rule meromorphic_intros)
+  show "f meromorphic_on A (pts1 \<union> pts2)"
+    by (rule meromorphic_on_superset_pts[OF assms(1)])
+       (use assms in \<open>auto simp: meromorphic_on_def islimpt_Un\<close>)
+  show "g meromorphic_on A (pts1 \<union> pts2)"
+    by (rule meromorphic_on_superset_pts[OF assms(2)])
+       (use assms in \<open>auto simp: meromorphic_on_def islimpt_Un\<close>)
+qed
+
+lemma meromorphic_on_mult [meromorphic_intros]:
+  assumes "f meromorphic_on A pts" "g meromorphic_on A pts"
+  shows   "(\<lambda>z. f z * g z) meromorphic_on A pts"
+  unfolding meromorphic_on_def
+  by (use assms in \<open>auto simp: meromorphic_on_def intro!: holomorphic_intros singularity_intros\<close>)
+
+lemma meromorphic_on_mult':
+  assumes "f meromorphic_on A pts1" "g meromorphic_on A pts2"
+  shows   "(\<lambda>z. f z * g z) meromorphic_on A (pts1 \<union> pts2)"
+proof (rule meromorphic_intros)
+  show "f meromorphic_on A (pts1 \<union> pts2)"
+    by (rule meromorphic_on_superset_pts[OF assms(1)])
+       (use assms in \<open>auto simp: meromorphic_on_def islimpt_Un\<close>)
+  show "g meromorphic_on A (pts1 \<union> pts2)"
+    by (rule meromorphic_on_superset_pts[OF assms(2)])
+       (use assms in \<open>auto simp: meromorphic_on_def islimpt_Un\<close>)
+qed
+
+
+
+lemma meromorphic_on_imp_not_essential:
+  assumes "f meromorphic_on A pts" "z \<in> A"
+  shows   "not_essential f z"
+proof (cases "z \<in> pts")
+  case False
+  thus ?thesis
+    using not_essential_holomorphic[of f "A - pts" z] meromorphic_imp_open_diff[OF assms(1)] assms
+    by (auto simp: meromorphic_on_def)
+qed (use assms in \<open>auto simp: meromorphic_on_def\<close>)
+
+lemma meromorphic_imp_analytic: "f meromorphic_on D pts \<Longrightarrow> f analytic_on (D - pts)"
+  unfolding meromorphic_on_def 
+  apply (subst analytic_on_open)
+  using meromorphic_imp_open_diff meromorphic_on_id apply blast
+  apply auto
+  done
+
+lemma not_islimpt_isolated_zeros:
+  assumes mero: "f meromorphic_on A pts" and "z \<in> A"
+  shows "\<not>z islimpt {w\<in>A. isolated_zero f w}"
+proof
+  assume islimpt: "z islimpt {w\<in>A. isolated_zero f w}"
+  have holo: "f holomorphic_on A - pts" and "open A"
+    using assms by (auto simp: meromorphic_on_def)
+  have open': "open (A - (pts - {z}))"
+    by (intro meromorphic_imp_open_diff'[OF mero]) auto
+  then obtain r where r: "r > 0" "ball z r \<subseteq> A - (pts - {z})"
+    using meromorphic_imp_open_diff[OF mero] \<open>z \<in> A\<close> openE by blast
+
+  have "not_essential f z"
+    using assms by (rule meromorphic_on_imp_not_essential)
+  then consider c where "f \<midarrow>z\<rightarrow> c" | "is_pole f z"
+    unfolding not_essential_def by blast
+  thus False
+  proof cases
+    assume "is_pole f z"
+    hence "eventually (\<lambda>w. f w \<noteq> 0) (at z)"
+      by (rule non_zero_neighbour_pole)
+    hence "\<not>z islimpt {w. f w = 0}"
+      by (simp add: islimpt_conv_frequently_at frequently_def)
+    moreover have "z islimpt {w. f w = 0}"
+      using islimpt by (rule islimpt_subset) (auto simp: isolated_zero_def)
+    ultimately show False by contradiction
+  next
+    fix c assume c: "f \<midarrow>z\<rightarrow> c"
+    define g where "g = (\<lambda>w. if w = z then c else f w)"
+    have holo': "g holomorphic_on A - (pts - {z})" unfolding g_def
+      by (intro removable_singularity holomorphic_on_subset[OF holo] open' c) auto
+
+    have eq_zero: "g w = 0" if "w \<in> ball z r" for w
+    proof (rule analytic_continuation[where f = g])
+      show "open (ball z r)" "connected (ball z r)" "{w\<in>ball z r. isolated_zero f w} \<subseteq> ball z r"
+        by auto
+      have "z islimpt {w\<in>A. isolated_zero f w} \<inter> ball z r"
+        using islimpt \<open>r > 0\<close> by (intro islimpt_Int_eventually eventually_at_in_open') auto
+      also have "\<dots> = {w\<in>ball z r. isolated_zero f w}"
+        using r by auto
+      finally show "z islimpt {w\<in>ball z r. isolated_zero f w}"
+        by simp
+    next
+      fix w assume w: "w \<in> {w\<in>ball z r. isolated_zero f w}"
+      show "g w = 0"
+      proof (cases "w = z")
+        case False
+        thus ?thesis using w by (auto simp: g_def isolated_zero_def)
+      next
+        case True
+        have "z islimpt {z. f z = 0}"
+          using islimpt by (rule islimpt_subset) (auto simp: isolated_zero_def)
+        thus ?thesis
+          using w by (simp add: isolated_zero_altdef True)
+      qed
+    qed (use r that in \<open>auto intro!: holomorphic_on_subset[OF holo'] simp: isolated_zero_def\<close>)
+
+    have "infinite ({w\<in>A. isolated_zero f w} \<inter> ball z r)"
+      using islimpt \<open>r > 0\<close> unfolding islimpt_eq_infinite_ball by blast
+    hence "{w\<in>A. isolated_zero f w} \<inter> ball z r \<noteq> {}"
+      by force
+    then obtain z0 where z0: "z0 \<in> A" "isolated_zero f z0" "z0 \<in> ball z r"
+      by blast
+    have "\<forall>\<^sub>F y in at z0. y \<in> ball z r - (if z = z0 then {} else {z}) - {z0}"
+      using r z0 by (intro eventually_at_in_open) auto
+    hence "eventually (\<lambda>w. f w = 0) (at z0)"
+    proof eventually_elim
+      case (elim w)
+      show ?case
+        using eq_zero[of w] elim by (auto simp: g_def split: if_splits)
+    qed
+    hence "eventually (\<lambda>w. f w = 0) (at z0)"
+      by (auto simp: g_def eventually_at_filter elim!: eventually_mono split: if_splits)
+    moreover from z0 have "eventually (\<lambda>w. f w \<noteq> 0) (at z0)"
+      by (simp add: isolated_zero_def)
+    ultimately have "eventually (\<lambda>_. False) (at z0)"
+      by eventually_elim auto
+    thus False
+      by simp
+  qed
+qed
+  
+lemma closedin_isolated_zeros:
+  assumes "f meromorphic_on A pts"
+  shows   "closedin (top_of_set A) {z\<in>A. isolated_zero f z}"
+  unfolding closedin_limpt using not_islimpt_isolated_zeros[OF assms] by auto
+
+lemma meromorphic_on_deriv':
+  assumes "f meromorphic_on A pts" "open A"
+  assumes "\<And>x. x \<in> A - pts \<Longrightarrow> (f has_field_derivative f' x) (at x)"
+  shows   "f' meromorphic_on A pts"
+  unfolding meromorphic_on_def
+proof (intro conjI ballI)
+  have "open (A - pts)"
+    by (intro meromorphic_imp_open_diff[OF assms(1)])
+  thus "f' holomorphic_on A - pts"
+    by (rule derivative_is_holomorphic) (use assms in auto)
+next
+  fix z assume "z \<in> pts"
+  hence "z \<in> A"
+    using assms(1) by (auto simp: meromorphic_on_def)
+  from \<open>z \<in> pts\<close> obtain r where r: "r > 0" "f analytic_on ball z r - {z}"
+    using assms(1) by (auto simp: meromorphic_on_def isolated_singularity_at_def)
+
+  have "open (ball z r \<inter> (A - (pts - {z})))"
+    by (intro open_Int assms meromorphic_imp_open_diff'[OF assms(1)]) auto
+  then obtain r' where r': "r' > 0" "ball z r' \<subseteq> ball z r \<inter> (A - (pts - {z}))"
+    using r \<open>z \<in> A\<close> by (subst (asm) open_contains_ball) fastforce
+
+  have "open (ball z r' - {z})"
+    by auto
+  hence "f' holomorphic_on ball z r' - {z}"
+    by (rule derivative_is_holomorphic[of _ f]) (use r' in \<open>auto intro!: assms(3)\<close>)
+  moreover have "open (ball z r' - {z})"
+    by auto
+  ultimately show "isolated_singularity_at f' z"
+    unfolding isolated_singularity_at_def using \<open>r' > 0\<close>
+    by (auto simp: analytic_on_open intro!: exI[of _ r'])
+next
+  fix z assume z: "z \<in> pts"
+  hence z': "not_essential f z" "z \<in> A"
+    using assms by (auto simp: meromorphic_on_def)
+  from z'(1) show "not_essential f' z"
+  proof (rule not_essential_deriv')
+    show "z \<in> A - (pts - {z})"
+      using \<open>z \<in> A\<close> by blast
+    show "open (A - (pts - {z}))"
+      by (intro meromorphic_imp_open_diff'[OF assms(1)]) auto
+  qed (use assms in auto)
+qed (use assms in \<open>auto simp: meromorphic_on_def\<close>)
+
+lemma meromorphic_on_deriv [meromorphic_intros]:
+  assumes "f meromorphic_on A pts" "open A"
+  shows   "deriv f meromorphic_on A pts"
+proof (intro meromorphic_on_deriv'[OF assms(1)])
+  have *: "open (A - pts)"
+    by (intro meromorphic_imp_open_diff[OF assms(1)])
+  show "(f has_field_derivative deriv f x) (at x)" if "x \<in> A - pts" for x
+    using assms(1) by (intro holomorphic_derivI[OF _ * that]) (auto simp: meromorphic_on_def)
+qed fact
+
+lemma meromorphic_on_imp_analytic_at:
+  assumes "f meromorphic_on A pts" "z \<in> A - pts"
+  shows   "f analytic_on {z}"
+  using assms by (metis analytic_at meromorphic_imp_open_diff meromorphic_on_def)
+
+lemma meromorphic_compact_finite_pts:
+  assumes "f meromorphic_on D pts" "compact S" "S \<subseteq> D"
+  shows "finite (S \<inter> pts)"
+proof -
+  { assume "infinite (S \<inter> pts)"
+    then obtain z where "z \<in> S" and z: "z islimpt (S \<inter> pts)"
+      using assms by (metis compact_eq_Bolzano_Weierstrass inf_le1) 
+    then have False
+        using assms by (meson in_mono inf_le2 islimpt_subset meromorphic_on_def) }
+  then show ?thesis by metis
+qed
+
+lemma meromorphic_imp_countable:
+  assumes "f meromorphic_on D pts" 
+  shows "countable pts"
+proof -
+  obtain K :: "nat \<Rightarrow> complex set" where K: "D = (\<Union>n. K n)" "\<And>n. compact (K n)"
+    using assms unfolding meromorphic_on_def by (metis open_Union_compact_subsets)
+  then have "pts = (\<Union>n. K n \<inter> pts)"
+    using assms meromorphic_on_def by auto
+  moreover have "\<And>n. finite (K n \<inter> pts)"
+    by (metis K(1) K(2) UN_I assms image_iff meromorphic_compact_finite_pts rangeI subset_eq)
+  ultimately show ?thesis
+    by (metis countableI_type countable_UN countable_finite)
+qed
+
+lemma meromorphic_imp_connected_diff':
+  assumes "f meromorphic_on D pts" "connected D" "pts' \<subseteq> pts"
+  shows "connected (D - pts')"
+proof (rule connected_open_diff_countable)
+  show "countable pts'"
+    by (rule countable_subset [OF assms(3)]) (use assms(1) in \<open>auto simp: meromorphic_imp_countable\<close>)
+qed (use assms in \<open>auto simp: meromorphic_on_def\<close>)
+
+lemma meromorphic_imp_connected_diff:
+  assumes "f meromorphic_on D pts" "connected D"
+  shows "connected (D - pts)"
+  using meromorphic_imp_connected_diff'[OF assms order.refl] .
+
+lemma meromorphic_on_compose [meromorphic_intros]:
+  assumes f: "f meromorphic_on A pts" and g: "g holomorphic_on B"
+  assumes "open B" and "g ` B \<subseteq> A"
+  shows   "(\<lambda>x. f (g x)) meromorphic_on B (isolated_points_of (g -` pts \<inter> B))"
+  unfolding meromorphic_on_def
+proof (intro ballI conjI)
+  fix z assume z: "z \<in> isolated_points_of (g -` pts \<inter> B)"
+  hence z': "z \<in> B" "g z \<in> pts"
+    using isolated_points_of_subset by blast+
+  have g': "g analytic_on {z}"
+    using g z' \<open>open B\<close> analytic_at by blast
+
+  show "isolated_singularity_at (\<lambda>x. f (g x)) z"
+    by (rule isolated_singularity_at_compose[OF _ g']) (use f z' in \<open>auto simp: meromorphic_on_def\<close>)
+  show "not_essential (\<lambda>x. f (g x)) z"
+    by (rule not_essential_compose[OF _ g']) (use f z' in \<open>auto simp: meromorphic_on_def\<close>)
+next
+  fix z assume z: "z \<in> B"
+  hence "g z \<in> A"
+    using assms by auto
+  hence "\<not>g z islimpt pts"
+    using f by (auto simp: meromorphic_on_def)
+  hence ev: "eventually (\<lambda>w. w \<notin> pts) (at (g z))"
+    by (auto simp: islimpt_conv_frequently_at frequently_def)
+  have g': "g analytic_on {z}"
+    by (rule holomorphic_on_imp_analytic_at[OF g]) (use assms z in auto)
+
+  (* TODO: There's probably a useful lemma somewhere in here to extract... *)
+  have "eventually (\<lambda>w. w \<notin> isolated_points_of (g -` pts \<inter> B)) (at z)"
+  proof (cases "isolated_zero (\<lambda>w. g w - g z) z")
+    case True
+    have "eventually (\<lambda>w. w \<notin> pts) (at (g z))"
+      using ev by (auto simp: islimpt_conv_frequently_at frequently_def)
+    moreover have "g \<midarrow>z\<rightarrow> g z"
+      using analytic_at_imp_isCont[OF g'] isContD by blast
+    hence lim: "filterlim g (at (g z)) (at z)"
+      using True by (auto simp: filterlim_at isolated_zero_def)
+    have "eventually (\<lambda>w. g w \<notin> pts) (at z)"
+      using ev lim by (rule eventually_compose_filterlim)
+    thus ?thesis
+      by eventually_elim (auto simp: isolated_points_of_def)
+  next
+    case False
+    have "eventually (\<lambda>w. g w - g z = 0) (nhds z)"
+      using False by (rule non_isolated_zero) (auto intro!: analytic_intros g')
+    hence "eventually (\<lambda>w. g w = g z \<and> w \<in> B) (nhds z)"
+      using eventually_nhds_in_open[OF \<open>open B\<close> \<open>z \<in> B\<close>]
+      by eventually_elim auto
+    then obtain X where X: "open X" "z \<in> X" "X \<subseteq> B" "\<forall>x\<in>X. g x = g z"
+      unfolding eventually_nhds by blast
+
+    have "z0 \<notin> isolated_points_of (g -` pts \<inter> B)" if "z0 \<in> X" for z0
+    proof (cases "g z \<in> pts")
+      case False
+      with that have "g z0 \<notin> pts"
+        using X by metis
+      thus ?thesis
+        by (auto simp: isolated_points_of_def)
+    next
+      case True
+      have "eventually (\<lambda>w. w \<in> X) (at z0)"
+        by (intro eventually_at_in_open') fact+
+      hence "eventually (\<lambda>w. w \<in> g -` pts \<inter> B) (at z0)"
+        by eventually_elim (use X True in fastforce)
+      hence "frequently (\<lambda>w. w \<in> g -` pts \<inter> B) (at z0)"
+        by (meson at_neq_bot eventually_frequently)
+      thus "z0 \<notin> isolated_points_of (g -` pts \<inter> B)"
+        unfolding isolated_points_of_def by (auto simp: frequently_def)
+    qed
+    moreover have "eventually (\<lambda>x. x \<in> X) (at z)"
+      by (intro eventually_at_in_open') fact+
+    ultimately show ?thesis
+      by (auto elim!: eventually_mono)
+  qed
+  thus "\<not>z islimpt isolated_points_of (g -` pts \<inter> B)"
+    by (auto simp: islimpt_conv_frequently_at frequently_def)
+next
+  have "f \<circ> g analytic_on (\<Union>z\<in>B - isolated_points_of (g -` pts \<inter> B). {z})"
+    unfolding analytic_on_UN
+  proof
+    fix z assume z: "z \<in> B - isolated_points_of (g -` pts \<inter> B)"
+    hence "z \<in> B" by blast
+    have g': "g analytic_on {z}"
+      by (rule holomorphic_on_imp_analytic_at[OF g]) (use assms z in auto)
+    show "f \<circ> g analytic_on {z}"
+    proof (cases "g z \<in> pts")
+      case False
+      show ?thesis
+      proof (rule analytic_on_compose)
+        show "f analytic_on g ` {z}" using False z assms
+          by (auto intro!: meromorphic_on_imp_analytic_at[OF f])
+      qed fact
+    next
+      case True
+      show ?thesis
+      proof (cases "isolated_zero (\<lambda>w. g w - g z) z")
+        case False
+        hence "eventually (\<lambda>w. g w - g z = 0) (nhds z)"
+          by (rule non_isolated_zero) (auto intro!: analytic_intros g')
+        hence "f \<circ> g analytic_on {z} \<longleftrightarrow> (\<lambda>_. f (g z)) analytic_on {z}"
+          by (intro analytic_at_cong) (auto elim!: eventually_mono)
+        thus ?thesis
+          by simp
+      next
+        case True
+        hence ev: "eventually (\<lambda>w. g w \<noteq> g z) (at z)"
+          by (auto simp: isolated_zero_def)
+  
+        have "\<not>g z islimpt pts"
+          using \<open>g z \<in> pts\<close> f by (auto simp: meromorphic_on_def)
+        hence "eventually (\<lambda>w. w \<notin> pts) (at (g z))"
+          by (auto simp: islimpt_conv_frequently_at frequently_def)
+        moreover have "g \<midarrow>z\<rightarrow> g z"
+          using analytic_at_imp_isCont[OF g'] isContD by blast
+        with ev have "filterlim g (at (g z)) (at z)"
+          by (auto simp: filterlim_at)
+        ultimately have "eventually (\<lambda>w. g w \<notin> pts) (at z)"
+          using eventually_compose_filterlim by blast
+        hence "z \<in> isolated_points_of (g -` pts \<inter> B)"
+          using \<open>g z \<in> pts\<close> \<open>z \<in> B\<close>
+          by (auto simp: isolated_points_of_def elim!: eventually_mono)
+        with z show ?thesis by simp
+      qed
+    qed
+  qed
+  also have "\<dots> = B - isolated_points_of (g -` pts \<inter> B)"
+    by blast
+  finally show "(\<lambda>x. f (g x)) holomorphic_on B - isolated_points_of (g -` pts \<inter> B)"
+    unfolding o_def using analytic_imp_holomorphic by blast
+qed (auto simp: isolated_points_of_def \<open>open B\<close>)
+
+lemma meromorphic_on_compose':
+  assumes f: "f meromorphic_on A pts" and g: "g holomorphic_on B"
+  assumes "open B" and "g ` B \<subseteq> A" and "pts' = (isolated_points_of (g -` pts \<inter> B))"
+  shows   "(\<lambda>x. f (g x)) meromorphic_on B pts'"
+  using meromorphic_on_compose[OF assms(1-4)] assms(5) by simp
+
+lemma meromorphic_on_inverse': "inverse meromorphic_on UNIV 0"
+  unfolding meromorphic_on_def
+  by (auto intro!: holomorphic_intros singularity_intros not_essential_inverse 
+                   isolated_singularity_at_inverse simp: islimpt_finite)
+
+lemma meromorphic_on_inverse [meromorphic_intros]:
+  assumes mero: "f meromorphic_on A pts"
+  shows   "(\<lambda>z. inverse (f z)) meromorphic_on A (pts \<union> {z\<in>A. isolated_zero f z})"
+proof -
+  have "open A"
+    using mero by (auto simp: meromorphic_on_def)
+  have open': "open (A - pts)"
+    by (intro meromorphic_imp_open_diff[OF mero])
+  have holo: "f holomorphic_on A - pts"
+    using assms by (auto simp: meromorphic_on_def)
+  have ana: "f analytic_on A - pts"
+    using open' holo by (simp add: analytic_on_open)
+
+  show ?thesis
+    unfolding meromorphic_on_def
+  proof (intro conjI ballI)
+    fix z assume z: "z \<in> pts \<union> {z\<in>A. isolated_zero f z}"
+    have "isolated_singularity_at f z \<and> not_essential f z"
+    proof (cases "z \<in> pts")
+      case False
+      have "f holomorphic_on A - pts - {z}"
+        by (intro holomorphic_on_subset[OF holo]) auto
+      hence "isolated_singularity_at f z"
+        by (rule isolated_singularity_at_holomorphic)
+           (use z False in \<open>auto intro!: meromorphic_imp_open_diff[OF mero]\<close>)
+      moreover have "not_essential f z"
+        using z False
+        by (intro not_essential_holomorphic[OF holo] meromorphic_imp_open_diff[OF mero]) auto
+      ultimately show ?thesis by blast
+    qed (use assms in \<open>auto simp: meromorphic_on_def\<close>)
+    thus "isolated_singularity_at (\<lambda>z. inverse (f z)) z" "not_essential (\<lambda>z. inverse (f z)) z"
+      by (auto intro!: isolated_singularity_at_inverse not_essential_inverse)
+  next
+    fix z assume "z \<in> A"
+    hence "\<not> z islimpt {z\<in>A. isolated_zero f z}"
+      by (rule not_islimpt_isolated_zeros[OF mero])
+    thus "\<not> z islimpt pts \<union> {z \<in> A. isolated_zero f z}" using \<open>z \<in> A\<close>
+      using mero by (auto simp: islimpt_Un meromorphic_on_def)
+  next
+    show "pts \<union> {z \<in> A. isolated_zero f z} \<subseteq> A"
+      using mero by (auto simp: meromorphic_on_def)
+  next
+    have "(\<lambda>z. inverse (f z)) analytic_on (\<Union>w\<in>A - (pts \<union> {z \<in> A. isolated_zero f z}) . {w})"
+      unfolding analytic_on_UN
+    proof (intro ballI)
+      fix w assume w: "w \<in> A - (pts \<union> {z \<in> A. isolated_zero f z})"
+      show "(\<lambda>z. inverse (f z)) analytic_on {w}"
+      proof (cases "f w = 0")
+        case False
+        thus ?thesis using w
+          by (intro analytic_intros analytic_on_subset[OF ana]) auto
+      next
+        case True
+        have "eventually (\<lambda>w. f w = 0) (nhds w)"
+          using True w by (intro non_isolated_zero analytic_on_subset[OF ana]) auto
+        hence "(\<lambda>z. inverse (f z)) analytic_on {w} \<longleftrightarrow> (\<lambda>_. 0) analytic_on {w}"
+          using w by (intro analytic_at_cong refl) auto
+        thus ?thesis
+          by simp
+      qed
+    qed
+    also have "\<dots> = A - (pts \<union> {z \<in> A. isolated_zero f z})"
+      by blast
+    finally have "(\<lambda>z. inverse (f z)) analytic_on \<dots>" .
+    moreover have "open (A - (pts \<union> {z \<in> A. isolated_zero f z}))"
+      using closedin_isolated_zeros[OF mero] open' \<open>open A\<close>
+      by (metis (no_types, lifting) Diff_Diff_Int Diff_Un closedin_closed open_Diff open_Int)
+    ultimately show "(\<lambda>z. inverse (f z)) holomorphic_on A - (pts \<union> {z \<in> A. isolated_zero f z})"
+      by (subst (asm) analytic_on_open) auto
+  qed (use assms in \<open>auto simp: meromorphic_on_def islimpt_Un 
+                          intro!: holomorphic_intros singularity_intros\<close>)
+qed
+
+lemma meromorphic_on_inverse'' [meromorphic_intros]:
+  assumes "f meromorphic_on A pts" "{z\<in>A. f z = 0} \<subseteq> pts"
+  shows   "(\<lambda>z. inverse (f z)) meromorphic_on A pts"
+proof -
+  have "(\<lambda>z. inverse (f z)) meromorphic_on A (pts \<union> {z \<in> A. isolated_zero f z})"
+    by (intro meromorphic_on_inverse assms)
+  also have "(pts \<union> {z \<in> A. isolated_zero f z}) = pts"
+    using assms(2) by (auto simp: isolated_zero_def)
+  finally show ?thesis .
+qed
+
+lemma meromorphic_on_divide [meromorphic_intros]:
+  assumes "f meromorphic_on A pts" and "g meromorphic_on A pts"
+  shows   "(\<lambda>z. f z / g z) meromorphic_on A (pts \<union> {z\<in>A. isolated_zero g z})"
+proof -
+  have mero1: "(\<lambda>z. inverse (g z)) meromorphic_on A (pts \<union> {z\<in>A. isolated_zero g z})"
+    by (intro meromorphic_intros assms)
+  have sparse: "\<forall>x\<in>A. \<not> x islimpt pts \<union> {z\<in>A. isolated_zero g z}" and "pts \<subseteq> A"
+    using mero1 by (auto simp: meromorphic_on_def)
+  have mero2: "f meromorphic_on A (pts \<union> {z\<in>A. isolated_zero g z})"
+    by (rule meromorphic_on_superset_pts[OF assms(1)]) (use sparse \<open>pts \<subseteq> A\<close> in auto)
+  have "(\<lambda>z. f z * inverse (g z)) meromorphic_on A (pts \<union> {z\<in>A. isolated_zero g z})"
+    by (intro meromorphic_on_mult mero1 mero2)
+  thus ?thesis
+    by (simp add: field_simps)
+qed
+
+lemma meromorphic_on_divide' [meromorphic_intros]:
+  assumes "f meromorphic_on A pts" "g meromorphic_on A pts" "{z\<in>A. g z = 0} \<subseteq> pts"
+  shows   "(\<lambda>z. f z / g z) meromorphic_on A pts"
+proof -
+  have "(\<lambda>z. f z * inverse (g z)) meromorphic_on A pts"
+    by (intro meromorphic_intros assms)
+  thus ?thesis
+    by (simp add: field_simps)
+qed
+
+lemma meromorphic_on_cmult_left [meromorphic_intros]:
+  assumes "f meromorphic_on A pts"
+  shows   "(\<lambda>x. c * f x) meromorphic_on A pts"
+  using assms by (intro meromorphic_intros) (auto simp: meromorphic_on_def)
+
+lemma meromorphic_on_cmult_right [meromorphic_intros]:
+  assumes "f meromorphic_on A pts"
+  shows   "(\<lambda>x. f x * c) meromorphic_on A pts"
+  using assms by (intro meromorphic_intros) (auto simp: meromorphic_on_def)
+
+lemma meromorphic_on_scaleR [meromorphic_intros]:
+  assumes "f meromorphic_on A pts"
+  shows   "(\<lambda>x. c *\<^sub>R f x) meromorphic_on A pts"
+  using assms unfolding scaleR_conv_of_real
+  by (intro meromorphic_intros) (auto simp: meromorphic_on_def)
+
+lemma meromorphic_on_sum [meromorphic_intros]:
+  assumes "\<And>y. y \<in> I \<Longrightarrow> f y meromorphic_on A pts"
+  assumes "I \<noteq> {} \<or> open A \<and> pts \<subseteq> A \<and> (\<forall>x\<in>A. \<not>x islimpt pts)"
+  shows   "(\<lambda>x. \<Sum>y\<in>I. f y x) meromorphic_on A pts"
+proof -
+  have *: "open A \<and> pts \<subseteq> A \<and> (\<forall>x\<in>A. \<not>x islimpt pts)"
+    using assms(2)
+  proof
+    assume "I \<noteq> {}"
+    then obtain x where "x \<in> I"
+      by blast
+    from assms(1)[OF this] show ?thesis
+      by (auto simp: meromorphic_on_def)
+  qed auto
+  show ?thesis
+    using assms(1)
+    by (induction I rule: infinite_finite_induct) (use * in \<open>auto intro!: meromorphic_intros\<close>)
+qed
+
+lemma meromorphic_on_prod [meromorphic_intros]:
+  assumes "\<And>y. y \<in> I \<Longrightarrow> f y meromorphic_on A pts"
+  assumes "I \<noteq> {} \<or> open A \<and> pts \<subseteq> A \<and> (\<forall>x\<in>A. \<not>x islimpt pts)"
+  shows   "(\<lambda>x. \<Prod>y\<in>I. f y x) meromorphic_on A pts"
+proof -
+  have *: "open A \<and> pts \<subseteq> A \<and> (\<forall>x\<in>A. \<not>x islimpt pts)"
+    using assms(2)
+  proof
+    assume "I \<noteq> {}"
+    then obtain x where "x \<in> I"
+      by blast
+    from assms(1)[OF this] show ?thesis
+      by (auto simp: meromorphic_on_def)
+  qed auto
+  show ?thesis
+    using assms(1)
+    by (induction I rule: infinite_finite_induct) (use * in \<open>auto intro!: meromorphic_intros\<close>)
+qed
+
+lemma meromorphic_on_power [meromorphic_intros]:
+  assumes "f meromorphic_on A pts"
+  shows   "(\<lambda>x. f x ^ n) meromorphic_on A pts"
+proof -
+  have "(\<lambda>x. \<Prod>i\<in>{..<n}. f x) meromorphic_on A pts"
+    by (intro meromorphic_intros assms(1)) (use assms in \<open>auto simp: meromorphic_on_def\<close>)
+  thus ?thesis
+    by simp
+qed
+
+lemma meromorphic_on_power_int [meromorphic_intros]:
+  assumes "f meromorphic_on A pts"
+  shows   "(\<lambda>z. f z powi n) meromorphic_on A (pts \<union> {z \<in> A. isolated_zero f z})"
+proof -
+  have inv: "(\<lambda>x. inverse (f x)) meromorphic_on A (pts \<union> {z \<in> A. isolated_zero f z})"
+    by (intro meromorphic_intros assms)
+  have *: "f meromorphic_on A (pts \<union> {z \<in> A. isolated_zero f z})"
+    by (intro meromorphic_on_superset_pts [OF assms(1)])
+       (use inv in \<open>auto simp: meromorphic_on_def\<close>)
+  show ?thesis
+  proof (cases "n \<ge> 0")
+    case True   
+    have "(\<lambda>x. f x ^ nat n) meromorphic_on A (pts \<union> {z \<in> A. isolated_zero f z})"
+      by (intro meromorphic_intros *)
+    thus ?thesis
+      using True by (simp add: power_int_def)
+  next
+    case False
+    have "(\<lambda>x. inverse (f x) ^ nat (-n)) meromorphic_on A (pts \<union> {z \<in> A. isolated_zero f z})"
+      by (intro meromorphic_intros assms)
+    thus ?thesis
+      using False by (simp add: power_int_def)
+  qed
+qed
+
+lemma meromorphic_on_power_int' [meromorphic_intros]:
+  assumes "f meromorphic_on A pts" "n \<ge> 0 \<or> (\<forall>z\<in>A. isolated_zero f z \<longrightarrow> z \<in> pts)"
+  shows   "(\<lambda>z. f z powi n) meromorphic_on A pts"
+proof (cases "n \<ge> 0")
+  case True
+  have "(\<lambda>z. f z ^ nat n) meromorphic_on A pts"
+    by (intro meromorphic_intros assms)
+  thus ?thesis
+    using True by (simp add: power_int_def)
+next
+  case False
+  have "(\<lambda>z. f z powi n) meromorphic_on A (pts \<union> {z\<in>A. isolated_zero f z})"
+    by (rule meromorphic_on_power_int) fact
+  also from assms(2) False have "pts \<union> {z\<in>A. isolated_zero f z} = pts"
+    by auto
+  finally show ?thesis .
+qed
+
+lemma has_laurent_expansion_on_imp_meromorphic_on:
+  assumes "open A" 
+  assumes laurent: "\<And>z. z \<in> A \<Longrightarrow> \<exists>F. (\<lambda>w. f (z + w)) has_laurent_expansion F"
+  shows   "f meromorphic_on A {z\<in>A. \<not>f analytic_on {z}}"
+  unfolding meromorphic_on_def
+proof (intro conjI ballI)
+  fix z assume "z \<in> {z\<in>A. \<not>f analytic_on {z}}"
+  then obtain F where F: "(\<lambda>w. f (z + w)) has_laurent_expansion F"
+    using laurent[of z] by blast
+  from F show "not_essential f z" "isolated_singularity_at f z"
+    using has_laurent_expansion_not_essential has_laurent_expansion_isolated by blast+
+next
+  fix z assume z: "z \<in> A"
+  obtain F where F: "(\<lambda>w. f (z + w)) has_laurent_expansion F"
+    using laurent[of z] \<open>z \<in> A\<close> by blast
+  from F have "isolated_singularity_at f z"
+    using has_laurent_expansion_isolated z by blast
+  then obtain r where r: "r > 0" "f analytic_on ball z r - {z}"
+    unfolding isolated_singularity_at_def by blast
+  have "f analytic_on {w}" if "w \<in> ball z r - {z}" for w
+    by (rule analytic_on_subset[OF r(2)]) (use that in auto)
+  hence "eventually (\<lambda>w. f analytic_on {w}) (at z)"
+    using eventually_at_in_open[of "ball z r" z] \<open>r > 0\<close> by (auto elim!: eventually_mono)
+  hence "\<not>z islimpt {w. \<not>f analytic_on {w}}"
+    by (auto simp: islimpt_conv_frequently_at frequently_def)
+  thus "\<not>z islimpt {w\<in>A. \<not>f analytic_on {w}}"
+    using islimpt_subset[of z "{w\<in>A. \<not>f analytic_on {w}}" "{w. \<not>f analytic_on {w}}"] by blast
+next
+  have "f analytic_on A - {w\<in>A. \<not>f analytic_on {w}}"
+    by (subst analytic_on_analytic_at) auto
+  thus "f holomorphic_on A - {w\<in>A. \<not>f analytic_on {w}}"
+    by (meson analytic_imp_holomorphic)
+qed (use assms in auto)
+
+lemma meromorphic_on_imp_has_laurent_expansion:
+  assumes "f meromorphic_on A pts" "z \<in> A"
+  shows   "(\<lambda>w. f (z + w)) has_laurent_expansion laurent_expansion f z"
+proof (cases "z \<in> pts")
+  case True
+  thus ?thesis
+    using assms by (intro not_essential_has_laurent_expansion) (auto simp: meromorphic_on_def)
+next
+  case False
+  have "f holomorphic_on (A - pts)"
+    using assms by (auto simp: meromorphic_on_def)
+  moreover have "z \<in> A - pts" "open (A - pts)"
+    using assms(2) False by (auto intro!: meromorphic_imp_open_diff[OF assms(1)])
+  ultimately have "f analytic_on {z}"
+    unfolding analytic_at by blast
+  thus ?thesis
+    using isolated_singularity_at_analytic not_essential_analytic
+          not_essential_has_laurent_expansion by blast
+qed    
+
+lemma
+  assumes "isolated_singularity_at f z" "f \<midarrow>z\<rightarrow> c"
+  shows   eventually_remove_sings_eq_nhds':
+            "eventually (\<lambda>w. remove_sings f w = (if w = z then c else f w)) (nhds z)"
+    and   remove_sings_analytic_at_singularity: "remove_sings f analytic_on {z}"
+proof -
+  have "eventually (\<lambda>w. w \<noteq> z) (at z)"
+    by (auto simp: eventually_at_filter)
+  hence "eventually (\<lambda>w. remove_sings f w = (if w = z then c else f w)) (at z)"
+    using eventually_remove_sings_eq_at[OF assms(1)]
+    by eventually_elim auto
+  moreover have "remove_sings f z = c"
+    using assms by auto
+  ultimately show ev: "eventually (\<lambda>w. remove_sings f w = (if w = z then c else f w)) (nhds z)"
+    by (simp add: eventually_at_filter)
+
+  have "(\<lambda>w. if w = z then c else f w) analytic_on {z}"
+    by (intro removable_singularity' assms)
+  also have "?this \<longleftrightarrow> remove_sings f analytic_on {z}"
+    using ev by (intro analytic_at_cong) (auto simp: eq_commute)
+  finally show \<dots> .
+qed
+
+lemma remove_sings_meromorphic_on:
+  assumes "f meromorphic_on A pts" "\<And>z. z \<in> pts - pts' \<Longrightarrow> \<not>is_pole f z" "pts' \<subseteq> pts"
+  shows   "remove_sings f meromorphic_on A pts'"
+  unfolding meromorphic_on_def
+proof safe
+  have "remove_sings f analytic_on {z}" if "z \<in> A - pts'" for z
+  proof (cases "z \<in> pts")
+    case False
+    hence *: "f analytic_on {z}"
+      using assms meromorphic_imp_open_diff[OF assms(1)] that
+      by (force simp: meromorphic_on_def analytic_at) 
+    have "remove_sings f analytic_on {z} \<longleftrightarrow> f analytic_on {z}"
+      by (intro analytic_at_cong eventually_remove_sings_eq_nhds * refl)
+    thus ?thesis using * by simp
+  next
+    case True
+    have isol: "isolated_singularity_at f z"
+      using True using assms by (auto simp: meromorphic_on_def)
+    from assms(1) have "not_essential f z"
+      using True by (auto simp: meromorphic_on_def)
+    with assms(2) True that obtain c where "f \<midarrow>z\<rightarrow> c"
+      by (auto simp: not_essential_def)
+    thus "remove_sings f analytic_on {z}"
+      by (intro remove_sings_analytic_at_singularity isol)
+  qed
+  hence "remove_sings f analytic_on A - pts'"
+    by (subst analytic_on_analytic_at) auto
+  thus "remove_sings f holomorphic_on A - pts'"
+    using meromorphic_imp_open_diff'[OF assms(1,3)] by (subst (asm) analytic_on_open)
+qed (use assms islimpt_subset[OF _ assms(3)] in \<open>auto simp: meromorphic_on_def\<close>)
+
+lemma remove_sings_holomorphic_on:
+  assumes "f meromorphic_on A pts" "\<And>z. z \<in> pts \<Longrightarrow> \<not>is_pole f z"
+  shows   "remove_sings f holomorphic_on A"
+  using remove_sings_meromorphic_on[OF assms(1), of "{}"] assms(2)
+  by (auto simp: meromorphic_on_no_singularities)
+
+lemma meromorphic_on_Ex_iff:
+  "(\<exists>pts. f meromorphic_on A pts) \<longleftrightarrow>
+     open A \<and> (\<forall>z\<in>A. \<exists>F. (\<lambda>w. f (z + w)) has_laurent_expansion F)"
+proof safe
+  fix pts assume *: "f meromorphic_on A pts"
+  from * show "open A"
+    by (auto simp: meromorphic_on_def)
+  show "\<exists>F. (\<lambda>w. f (z + w)) has_laurent_expansion F" if "z \<in> A" for z
+    using that *
+    by (intro exI[of _ "laurent_expansion f z"] meromorphic_on_imp_has_laurent_expansion)
+qed (blast intro!: has_laurent_expansion_on_imp_meromorphic_on)
+
+lemma is_pole_inverse_holomorphic_pts:
+  fixes pts::"complex set" and f::"complex \<Rightarrow> complex"
+  defines "g \<equiv> \<lambda>x. (if x\<in>pts then 0 else inverse (f x))"
+  assumes mer: "f meromorphic_on D pts"
+    and non_z: "\<And>z. z \<in> D - pts \<Longrightarrow> f z \<noteq> 0"
+    and all_poles:"\<forall>x. is_pole f x \<longleftrightarrow> x\<in>pts"
+  shows "g holomorphic_on D"
+proof -
+  have "open D" and f_holo: "f holomorphic_on (D-pts)" 
+    using mer by (auto simp: meromorphic_on_def)
+  have "\<exists>r. r>0 \<and> f analytic_on ball z r - {z} 
+            \<and> (\<forall>x \<in> ball z r - {z}. f x\<noteq>0)" if "z\<in>pts" for z 
+  proof -
+    have "isolated_singularity_at f z" "is_pole f z"
+      using mer meromorphic_on_def that all_poles by blast+
+    then obtain r1 where "r1>0" and fan: "f analytic_on ball z r1 - {z}"
+      by (meson isolated_singularity_at_def)
+    obtain r2 where "r2>0" "\<forall>x \<in> ball z r2 - {z}. f x\<noteq>0"
+      using non_zero_neighbour_pole[OF \<open>is_pole f z\<close>] 
+      unfolding eventually_at by (metis Diff_iff UNIV_I dist_commute insertI1 mem_ball)
+    define r where "r = min r1 r2"
+    have "r>0" by (simp add: \<open>0 < r2\<close> \<open>r1>0\<close> r_def)
+    moreover have "f analytic_on ball z r - {z}"
+      using r_def by (force intro: analytic_on_subset [OF fan])
+    moreover have "\<forall>x \<in> ball z r - {z}. f x\<noteq>0"
+      by (simp add: \<open>\<forall>x\<in>ball z r2 - {z}. f x \<noteq> 0\<close> r_def)
+    ultimately show ?thesis by auto
+  qed
+  then obtain get_r where r_pos:"get_r z>0" 
+      and r_ana:"f analytic_on ball z (get_r z) - {z}"
+      and r_nz:"\<forall>x \<in> ball z (get_r z) - {z}. f x\<noteq>0"
+    if "z\<in>pts" for z
+    by metis
+  define p_balls where "p_balls \<equiv> \<Union>z\<in>pts. ball z (get_r z)"
+  have g_ball:"g holomorphic_on ball z (get_r z)" if "z\<in>pts" for z
+  proof -
+    have "(\<lambda>x. if x = z then 0 else inverse (f x)) holomorphic_on ball z (get_r z)"
+    proof (rule is_pole_inverse_holomorphic)
+      show "f holomorphic_on ball z (get_r z) - {z}"
+        using analytic_imp_holomorphic r_ana that by blast
+      show "is_pole f z"
+        using mer meromorphic_on_def that all_poles by force
+      show "\<forall>x\<in>ball z (get_r z) - {z}. f x \<noteq> 0"
+        using r_nz that by metis
+    qed auto
+    then show ?thesis unfolding g_def
+      by (smt (verit, ccfv_SIG) Diff_iff Elementary_Metric_Spaces.open_ball
+          all_poles analytic_imp_holomorphic empty_iff 
+          holomorphic_transform insert_iff not_is_pole_holomorphic 
+          open_delete r_ana that)
+  qed
+  then have "g holomorphic_on p_balls" 
+  proof -
+    have "g analytic_on p_balls"
+      unfolding p_balls_def analytic_on_UN
+      using g_ball by (simp add: analytic_on_open)
+    moreover have "open p_balls" using p_balls_def by blast
+    ultimately show ?thesis 
+      by (simp add: analytic_imp_holomorphic)
+  qed
+  moreover have "g holomorphic_on D-pts" 
+  proof -
+    have "(\<lambda>z. inverse (f z)) holomorphic_on D - pts"
+      using f_holo holomorphic_on_inverse non_z by blast
+    then show ?thesis
+      by (metis DiffD2 g_def holomorphic_transform) 
+  qed
+  moreover have "open p_balls" 
+    using p_balls_def by blast
+  ultimately have "g holomorphic_on (p_balls \<union> (D-pts))"
+    by (simp add: holomorphic_on_Un meromorphic_imp_open_diff[OF mer])
+  moreover have "D \<subseteq> p_balls \<union> (D-pts)"
+    unfolding p_balls_def using \<open>\<And>z. z \<in> pts \<Longrightarrow> 0 < get_r z\<close> by force
+  ultimately show "g holomorphic_on D" by (meson holomorphic_on_subset)
+qed
+
+lemma meromorphic_imp_analytic_on:
+  assumes "f meromorphic_on D pts"
+  shows "f analytic_on (D - pts)"
+  by (metis assms analytic_on_open meromorphic_imp_open_diff meromorphic_on_def)
+
+lemma meromorphic_imp_constant_on:
+  assumes merf: "f meromorphic_on D pts" 
+      and "f constant_on (D - pts)"
+      and "\<forall>x\<in>pts. is_pole f x"
+    shows "f constant_on D"
+proof -
+  obtain c where c:"\<And>z. z \<in> D-pts \<Longrightarrow> f z = c"
+    by (meson assms constant_on_def)
+
+  have "f z = c" if "z \<in> D" for z
+  proof (cases "is_pole f z")
+    case True
+    then obtain r0 where "r0 > 0" and r0: "f analytic_on ball z r0 - {z}" and pol: "is_pole f z"
+      using merf unfolding meromorphic_on_def isolated_singularity_at_def 
+      by (metis \<open>z \<in> D\<close> insert_Diff insert_Diff_if insert_iff merf 
+          meromorphic_imp_open_diff not_is_pole_holomorphic)
+    have "open D"
+      using merf meromorphic_on_def by auto
+    then obtain r where "r > 0" "ball z r \<subseteq> D" "r \<le> r0"
+      by (smt (verit, best) \<open>0 < r0\<close> \<open>z \<in> D\<close> openE order_subst2 subset_ball)
+    have r: "f analytic_on ball z r - {z}"
+      by (meson Diff_mono \<open>r \<le> r0\<close> analytic_on_subset order_refl r0 subset_ball)
+    have "ball z r - {z} \<subseteq> -pts"
+      using merf r unfolding meromorphic_on_def
+      by (meson ComplI Elementary_Metric_Spaces.open_ball 
+          analytic_imp_holomorphic assms(3) not_is_pole_holomorphic open_delete subsetI)
+    with \<open>ball z r \<subseteq> D\<close> have "ball z r - {z} \<subseteq> D-pts"
+      by fastforce
+    with c have c': "\<And>u. u \<in> ball z r - {z} \<Longrightarrow> f u = c"
+      by blast    
+    have False if "\<forall>\<^sub>F x in at z. cmod c + 1 \<le> cmod (f x)"
+    proof -
+      have "\<forall>\<^sub>F x in at z within ball z r - {z}. cmod c + 1 \<le> cmod (f x)"
+        by (smt (verit, best) Diff_UNIV Diff_eq_empty_iff eventually_at_topological insert_subset that)
+      with \<open>r > 0\<close> show ?thesis
+        apply (simp add: c' eventually_at_filter topological_space_class.eventually_nhds open_dist)
+        by (metis dist_commute min_less_iff_conj perfect_choose_dist)
+    qed
+    with pol show ?thesis
+      by (auto simp: is_pole_def filterlim_at_infinity_conv_norm_at_top filterlim_at_top)
+  next
+    case False
+    then show ?thesis by (meson DiffI assms(3) c that)
+  qed 
+  then show ?thesis
+    by (simp add: constant_on_def)
+qed
+
+
+lemma meromorphic_isolated:
+  assumes merf: "f meromorphic_on D pts" and "p\<in>pts"
+  obtains r where "r>0" "ball p r \<subseteq> D" "ball p r \<inter> pts = {p}"
+proof -
+  have "\<forall>z\<in>D. \<exists>e>0. finite (pts \<inter> ball z e)" 
+    using merf unfolding meromorphic_on_def islimpt_eq_infinite_ball
+    by auto
+  then obtain r0 where r0:"r0>0" "finite (pts \<inter> ball p r0)"
+    by (metis assms(2) in_mono merf meromorphic_on_def)
+  moreover define pts' where "pts' = pts \<inter> ball p r0 - {p}"
+  ultimately have "finite pts'"
+    by simp
+  
+  define r1 where "r1=(if pts'={} then r0 else 
+                          min (Min {dist p' p |p'. p'\<in>pts'}/2) r0)"
+  have "r1>0 \<and> pts \<inter> ball p r1 - {p} = {}"
+  proof (cases "pts'={}")
+    case True
+    then show ?thesis 
+      using pts'_def r0(1) r1_def by presburger
+  next
+    case False
+    define S where "S={dist p' p |p'. p'\<in>pts'}"
+
+    have nempty:"S \<noteq> {}"
+      using False S_def by blast
+    have finite:"finite S"
+      using \<open>finite pts'\<close> S_def by simp
+
+    have "r1>0"
+    proof -
+      have "r1=min (Min S/2) r0"
+        using False unfolding S_def r1_def by auto
+      moreover have "Min S\<in>S"
+        using \<open>S\<noteq>{}\<close> \<open>finite S\<close>  Min_in by auto
+      then have "Min S>0" unfolding S_def 
+        using pts'_def by force
+      ultimately show ?thesis using \<open>r0>0\<close> by auto
+    qed
+    moreover have "pts \<inter> ball p r1 - {p} = {}"
+    proof (rule ccontr)
+      assume "pts \<inter> ball p r1 - {p} \<noteq> {}"
+      then obtain p' where "p'\<in>pts \<inter> ball p r1 - {p}" by blast
+      moreover have "r1\<le>r0" using r1_def by auto
+      ultimately have "p'\<in>pts'" unfolding pts'_def 
+        by auto
+      then have "dist p' p\<ge>Min S" 
+        using S_def eq_Min_iff local.finite by blast
+      moreover have "dist p' p < Min S"
+        using \<open>p'\<in>pts \<inter> ball p r1 - {p}\<close> False unfolding r1_def
+        apply (fold S_def)
+        by (smt (verit, ccfv_threshold) DiffD1 Int_iff dist_commute 
+            dist_triangle_half_l mem_ball)
+      ultimately show False by auto
+    qed
+    ultimately show ?thesis by auto
+  qed
+  then have "r1>0" and r1_pts:"pts \<inter> ball p r1 - {p} = {}" by auto
+
+  obtain r2 where "r2>0" "ball p r2 \<subseteq> D"
+    by (metis assms(2) merf meromorphic_on_def openE subset_eq)
+  define r where "r=min r1 r2"
+  have "r > 0" unfolding r_def 
+    by (simp add: \<open>0 < r1\<close> \<open>0 < r2\<close>)
+  moreover have "ball p r \<subseteq> D" 
+    using \<open>ball p r2 \<subseteq> D\<close> r_def by auto
+  moreover have "ball p r \<inter> pts = {p}"
+    using assms(2) \<open>r>0\<close> r1_pts
+    unfolding r_def by auto
+  ultimately show ?thesis using that by auto
+qed
+
+lemma meromorphic_pts_closure:
+  assumes merf: "f meromorphic_on D pts" 
+  shows "pts \<subseteq> closure (D - pts)"
+proof -
+  have "p islimpt (D - pts)" if "p\<in>pts" for p 
+  proof -
+    obtain r where "r>0" "ball p r \<subseteq> D" "ball p r \<inter> pts = {p}"
+      using meromorphic_isolated[OF merf \<open>p\<in>pts\<close>] by auto
+    from \<open>r>0\<close>
+    have "p islimpt ball p r - {p}"
+      by (meson open_ball ball_subset_cball in_mono islimpt_ball 
+          islimpt_punctured le_less open_contains_ball_eq)
+    moreover have " ball p r - {p} \<subseteq> D - pts"
+      using \<open>ball p r \<inter> pts = {p}\<close> \<open>ball p r \<subseteq> D\<close> by fastforce
+    ultimately show ?thesis 
+      using islimpt_subset by auto
+  qed
+  then show ?thesis by (simp add: islimpt_in_closure subset_eq)
+qed
+
+lemma nconst_imp_nzero_neighbour:
+  assumes merf: "f meromorphic_on D pts" 
+    and f_nconst:"\<not>(\<forall>w\<in>D-pts. f w=0)"
+    and "z\<in>D" and "connected D"
+  shows "(\<forall>\<^sub>F w in at z. f w \<noteq> 0 \<and> w \<in> D - pts)"
+proof -
+  obtain \<beta> where \<beta>:"\<beta> \<in> D - pts" "f \<beta>\<noteq>0"
+    using f_nconst by auto
+
+  have ?thesis if "z\<notin>pts" 
+  proof -
+    have "\<forall>\<^sub>F w in at z. f w \<noteq> 0 \<and> w \<in> D - pts"
+      apply (rule non_zero_neighbour_alt[of f "D-pts" z  \<beta>])
+      subgoal using merf meromorphic_on_def by blast
+      subgoal using merf meromorphic_imp_open_diff by auto
+      subgoal using assms(4) merf meromorphic_imp_connected_diff by blast
+      subgoal by (simp add: assms(3) that)
+      using \<beta> by auto
+    then show ?thesis by (auto elim:eventually_mono)
+  qed
+  moreover have ?thesis if "z\<in>pts" "\<not> f \<midarrow>z\<rightarrow> 0" 
+  proof -
+    have "\<forall>\<^sub>F w in at z. w \<in> D - pts"
+      using merf[unfolded meromorphic_on_def islimpt_iff_eventually] \<open>z\<in>D\<close>
+      using eventually_at_in_open' eventually_elim2 by fastforce
+    moreover have "\<forall>\<^sub>F w in at z. f w \<noteq> 0" 
+    proof (cases  "is_pole f z")
+      case True
+      then show ?thesis using non_zero_neighbour_pole by auto
+    next
+      case False
+      moreover have "not_essential f z"
+        using merf meromorphic_on_def that(1) by fastforce
+      ultimately obtain c where "c\<noteq>0" "f \<midarrow>z\<rightarrow> c"
+        by (metis \<open>\<not> f \<midarrow>z\<rightarrow> 0\<close> not_essential_def)
+      then show ?thesis 
+        using tendsto_imp_eventually_ne by auto
+    qed
+    ultimately show ?thesis by eventually_elim auto
+  qed
+  moreover have ?thesis if "z\<in>pts" "f \<midarrow>z\<rightarrow> 0" 
+  proof -
+    define ff where "ff=(\<lambda>x. if x=z then 0 else f x)"
+    define A where "A=D - (pts - {z})"
+
+    have "f holomorphic_on A - {z}"
+      by (metis A_def Diff_insert analytic_imp_holomorphic 
+            insert_Diff merf meromorphic_imp_analytic_on that(1))
+    moreover have "open A"  
+      using A_def merf meromorphic_imp_open_diff' by force
+    ultimately have "ff holomorphic_on A" 
+      using \<open>f \<midarrow>z\<rightarrow> 0\<close> unfolding ff_def
+      by (rule removable_singularity)
+    moreover have "connected A"
+    proof -
+      have "connected (D - pts)" 
+        using assms(4) merf meromorphic_imp_connected_diff by auto
+      moreover have "D - pts \<subseteq> A"
+        unfolding A_def by auto
+      moreover have "A \<subseteq> closure (D - pts)" unfolding A_def
+        by (smt (verit, ccfv_SIG) Diff_empty Diff_insert 
+            closure_subset insert_Diff_single insert_absorb 
+            insert_subset merf meromorphic_pts_closure that(1))
+      ultimately show ?thesis using connected_intermediate_closure 
+        by auto
+    qed
+    moreover have "z \<in> A" using A_def assms(3) by blast
+    moreover have "ff z = 0" unfolding ff_def by auto
+    moreover have "\<beta> \<in> A " using A_def \<beta>(1) by blast
+    moreover have "ff \<beta> \<noteq> 0" using \<beta>(1) \<beta>(2) ff_def that(1) by auto
+    ultimately obtain r where "0 < r" 
+        "ball z r \<subseteq> A" "\<And>x. x \<in> ball z r - {z} \<Longrightarrow> ff x \<noteq> 0"
+      using \<open>open A\<close> isolated_zeros[of ff A z \<beta>] by auto
+    then show ?thesis unfolding eventually_at ff_def
+      by (intro exI[of _ r]) (auto simp: A_def dist_commute ball_def)
+  qed
+  ultimately show ?thesis by auto
+qed
+
+lemma nconst_imp_nzero_neighbour':
+  assumes merf: "f meromorphic_on D pts" 
+    and f_nconst:"\<not>(\<forall>w\<in>D-pts. f w=0)"
+    and "z\<in>D" and "connected D"
+  shows "\<forall>\<^sub>F w in at z. f w \<noteq> 0"
+  using nconst_imp_nzero_neighbour[OF assms]
+  by (auto elim:eventually_mono)
+
+lemma meromorphic_compact_finite_zeros:
+  assumes merf:"f meromorphic_on D pts" 
+    and "compact S" "S \<subseteq> D" "connected D"
+    and f_nconst:"\<not>(\<forall>w\<in>D-pts. f w=0)"
+  shows "finite ({x\<in>S. f x=0})"
+proof -
+  have "finite ({x\<in>S. f x=0 \<and> x \<notin> pts})" 
+  proof (rule ccontr)
+    assume "infinite {x \<in> S. f x = 0 \<and> x \<notin> pts}"
+    then obtain z where "z\<in>S" and z_lim:"z islimpt {x \<in> S. f x = 0
+                                              \<and> x \<notin> pts}"
+      using \<open>compact S\<close> unfolding compact_eq_Bolzano_Weierstrass
+      by auto
+  
+    from z_lim
+    have "\<exists>\<^sub>F x in at z. f x = 0 \<and> x \<in> S \<and> x \<notin> pts"
+      unfolding islimpt_iff_eventually not_eventually by simp
+    moreover have "\<forall>\<^sub>F w in at z. f w \<noteq> 0 \<and> w \<in> D - pts"
+      using nconst_imp_nzero_neighbour[OF merf f_nconst _ \<open>connected D\<close>]
+        \<open>z\<in>S\<close> \<open>S \<subseteq> D\<close>
+      by auto
+    ultimately have "\<exists>\<^sub>F x in at z. False"
+      by (simp add: eventually_mono frequently_def)
+    then show False by auto
+  qed
+  moreover have "finite (S \<inter> pts)" 
+    using meromorphic_compact_finite_pts[OF merf \<open>compact S\<close> \<open>S \<subseteq> D\<close>] .
+  ultimately have "finite ({x\<in>S. f x=0 \<and> x \<notin> pts} \<union> (S \<inter> pts))"
+    unfolding finite_Un by auto 
+  then show ?thesis by (elim rev_finite_subset) auto
+qed
+
+lemma meromorphic_onI [intro?]:
+  assumes "open A" "pts \<subseteq> A"
+  assumes "f holomorphic_on A - pts" "\<And>z. z \<in> A \<Longrightarrow> \<not>z islimpt pts"
+  assumes "\<And>z. z \<in> pts \<Longrightarrow> isolated_singularity_at f z"
+  assumes "\<And>z. z \<in> pts \<Longrightarrow> not_essential f z"
+  shows   "f meromorphic_on A pts"
+  using assms unfolding meromorphic_on_def by blast
+
+lemma Polygamma_plus_of_nat:
+  assumes "\<forall>k<m. z \<noteq> -of_nat k"
+  shows   "Polygamma n (z + of_nat m) =
+             Polygamma n z + (-1) ^ n * fact n * (\<Sum>k<m. 1 / (z + of_nat k) ^ Suc n)"
+  using assms
+proof (induction m)
+  case (Suc m)
+  have "Polygamma n (z + of_nat (Suc m)) = Polygamma n (z + of_nat m + 1)"
+    by (simp add: add_ac)
+  also have "\<dots> = Polygamma n (z + of_nat m) + (-1) ^ n * fact n * (1 / ((z + of_nat m) ^ Suc n))"
+    using Suc.prems by (subst Polygamma_plus1) (auto simp: add_eq_0_iff2)
+  also have "Polygamma n (z + of_nat m) =
+               Polygamma n z + (-1) ^ n * (\<Sum>k<m. 1 / (z + of_nat k) ^ Suc n) * fact n"
+    using Suc.prems by (subst Suc.IH) auto
+  finally show ?case
+    by (simp add: algebra_simps)
+qed auto
+
+lemma tendsto_Gamma [tendsto_intros]:
+  assumes "(f \<longlongrightarrow> c) F" "c \<notin> \<int>\<^sub>\<le>\<^sub>0"
+  shows   "((\<lambda>z. Gamma (f z)) \<longlongrightarrow> Gamma c) F"
+  by (intro isCont_tendsto_compose[OF _ assms(1)] continuous_intros assms)
+
+lemma tendsto_Polygamma [tendsto_intros]:
+  fixes f :: "_ \<Rightarrow> 'a :: {real_normed_field,euclidean_space}"
+  assumes "(f \<longlongrightarrow> c) F" "c \<notin> \<int>\<^sub>\<le>\<^sub>0"
+  shows   "((\<lambda>z. Polygamma n (f z)) \<longlongrightarrow> Polygamma n c) F"
+  by (intro isCont_tendsto_compose[OF _ assms(1)] continuous_intros assms)
+
+lemma analytic_on_Gamma' [analytic_intros]:
+  assumes "f analytic_on A" "\<forall>x\<in>A. f x \<notin> \<int>\<^sub>\<le>\<^sub>0" 
+  shows   "(\<lambda>z. Gamma (f z)) analytic_on A"
+  using analytic_on_compose_gen[OF assms(1) analytic_Gamma[of "f ` A"]] assms(2)
+  by (auto simp: o_def)
+
+lemma analytic_on_Polygamma' [analytic_intros]:
+  assumes "f analytic_on A" "\<forall>x\<in>A. f x \<notin> \<int>\<^sub>\<le>\<^sub>0" 
+  shows   "(\<lambda>z. Polygamma n (f z)) analytic_on A"
+  using analytic_on_compose_gen[OF assms(1) analytic_on_Polygamma[of "f ` A" n]] assms(2)
+  by (auto simp: o_def)
+
+lemma
+  shows is_pole_Polygamma: "is_pole (Polygamma n) (-of_nat m :: complex)"
+  and   zorder_Polygamma:  "zorder (Polygamma n) (-of_nat m) = -int (Suc n)"
+  and   residue_Polygamma: "residue (Polygamma n) (-of_nat m) = (if n = 0 then -1 else 0)"
+proof -
+  define g1 :: "complex \<Rightarrow> complex" where
+    "g1 = (\<lambda>z. Polygamma n (z + of_nat (Suc m)) +
+              (-1) ^ Suc n * fact n * (\<Sum>k<m. 1 / (z + of_nat k) ^ Suc n))"
+  define g :: "complex \<Rightarrow> complex" where
+    "g = (\<lambda>z. g1 z + (-1) ^ Suc n * fact n / (z + of_nat m) ^ Suc n)"
+  define F where "F = fps_to_fls (fps_expansion g1 (-of_nat m)) + fls_const ((-1) ^ Suc n * fact n) / fls_X ^ Suc n"
+  have F_altdef: "F = fps_to_fls (fps_expansion g1 (-of_nat m)) + fls_shift (n+1) (fls_const ((-1) ^ Suc n * fact n))"
+    by (simp add: F_def del: power_Suc)
+
+  have "\<not>(-of_nat m) islimpt (\<int>\<^sub>\<le>\<^sub>0 :: complex set)"
+    by (intro discrete_imp_not_islimpt[where e = 1])
+       (auto elim!: nonpos_Ints_cases simp: dist_of_int)
+  hence "eventually (\<lambda>z::complex. z \<notin> \<int>\<^sub>\<le>\<^sub>0) (at (-of_nat m))"
+    by (auto simp: islimpt_conv_frequently_at frequently_def)
+  hence ev: "eventually (\<lambda>z. Polygamma n z = g z) (at (-of_nat m))"
+  proof eventually_elim
+    case (elim z)
+    hence *: "\<forall>k<Suc m. z \<noteq> - of_nat k"
+      by auto
+    thus ?case
+      using Polygamma_plus_of_nat[of "Suc m" z n, OF *]
+      by (auto simp: g_def g1_def algebra_simps)
+  qed
+
+  have "(\<lambda>w. g (-of_nat m + w)) has_laurent_expansion F"
+    unfolding g_def F_def
+    by (intro laurent_expansion_intros has_laurent_expansion_fps analytic_at_imp_has_fps_expansion)
+       (auto simp: g1_def intro!: laurent_expansion_intros analytic_intros)
+  also have "?this \<longleftrightarrow> (\<lambda>w. Polygamma n (-of_nat m + w)) has_laurent_expansion F"
+    using ev by (intro has_laurent_expansion_cong refl)
+                (simp_all add: eq_commute at_to_0' eventually_filtermap)
+  finally have *: "(\<lambda>w. Polygamma n (-of_nat m + w)) has_laurent_expansion F" .
+
+  have subdegree: "fls_subdegree F = -int (Suc n)" unfolding F_def
+    by (subst fls_subdegree_add_eq2) (simp_all add: fls_subdegree_fls_to_fps fls_divide_subdegree)
+  have [simp]: "F \<noteq> 0"
+    using subdegree by auto
+  
+  show "is_pole (Polygamma n) (-of_nat m :: complex)"
+    using * by (rule has_laurent_expansion_imp_is_pole) (auto simp: subdegree)
+  show "zorder (Polygamma n) (-of_nat m :: complex) = -int (Suc n)"
+    by (subst has_laurent_expansion_zorder[OF *]) (auto simp: subdegree)
+  show "residue (Polygamma n) (-of_nat m :: complex) = (if n = 0 then -1 else 0)"
+    by (subst has_laurent_expansion_residue[OF *]) (auto simp: F_altdef)
+qed
+
+lemma Gamma_meromorphic_on [meromorphic_intros]: "Gamma meromorphic_on UNIV \<int>\<^sub>\<le>\<^sub>0"
+proof
+  show "\<not>z islimpt \<int>\<^sub>\<le>\<^sub>0" for z :: complex
+    by (intro discrete_imp_not_islimpt[of 1]) (auto elim!: nonpos_Ints_cases simp: dist_of_int)
+next
+  fix z :: complex assume z: "z \<in> \<int>\<^sub>\<le>\<^sub>0"
+  then obtain n where n: "z = -of_nat n"
+    by (elim nonpos_Ints_cases')
+  show "not_essential Gamma z"
+    by (auto simp: n intro!: is_pole_imp_not_essential is_pole_Gamma)
+  have *: "open (-(\<int>\<^sub>\<le>\<^sub>0 - {z}))"
+    by (intro open_Compl discrete_imp_closed[of 1]) (auto elim!: nonpos_Ints_cases simp: dist_of_int)
+  have "Gamma holomorphic_on -(\<int>\<^sub>\<le>\<^sub>0 - {z}) - {z}"
+    by (intro holomorphic_intros) auto
+  thus "isolated_singularity_at Gamma z"
+    by (rule isolated_singularity_at_holomorphic) (use z * in auto)
+qed (auto intro!: holomorphic_intros)
+
+lemma Polygamma_meromorphic_on [meromorphic_intros]: "Polygamma n meromorphic_on UNIV \<int>\<^sub>\<le>\<^sub>0"
+proof
+  show "\<not>z islimpt \<int>\<^sub>\<le>\<^sub>0" for z :: complex
+    by (intro discrete_imp_not_islimpt[of 1]) (auto elim!: nonpos_Ints_cases simp: dist_of_int)
+next
+  fix z :: complex assume z: "z \<in> \<int>\<^sub>\<le>\<^sub>0"
+  then obtain m where n: "z = -of_nat m"
+    by (elim nonpos_Ints_cases')
+  show "not_essential (Polygamma n) z"
+    by (auto simp: n intro!: is_pole_imp_not_essential is_pole_Polygamma)
+  have *: "open (-(\<int>\<^sub>\<le>\<^sub>0 - {z}))"
+    by (intro open_Compl discrete_imp_closed[of 1]) (auto elim!: nonpos_Ints_cases simp: dist_of_int)
+  have "Polygamma n holomorphic_on -(\<int>\<^sub>\<le>\<^sub>0 - {z}) - {z}"
+    by (intro holomorphic_intros) auto
+  thus "isolated_singularity_at (Polygamma n) z"
+    by (rule isolated_singularity_at_holomorphic) (use z * in auto)
+qed (auto intro!: holomorphic_intros)
+
+
+theorem argument_principle':
+  fixes f::"complex \<Rightarrow> complex" and poles s:: "complex set"
+  \<comment> \<open>\<^term>\<open>pz\<close> is the set of non-essential singularities and zeros\<close>
+  defines "pz \<equiv> {w\<in>s. f w = 0 \<or> w \<in> poles}"
+  assumes "open s" and
+          "connected s" and
+          f_holo:"f holomorphic_on s-poles" and
+          h_holo:"h holomorphic_on s" and
+          "valid_path g" and
+          loop:"pathfinish g = pathstart g" and
+          path_img:"path_image g \<subseteq> s - pz" and
+          homo:"\<forall>z. (z \<notin> s) \<longrightarrow> winding_number g z = 0" and
+          finite:"finite pz" and
+          poles:"\<forall>p\<in>s\<inter>poles. not_essential f p"
+  shows "contour_integral g (\<lambda>x. deriv f x * h x / f x) = 2 * pi * \<i> *
+          (\<Sum>p\<in>pz. winding_number g p * h p * zorder f p)"
+proof -
+  define ff where "ff = remove_sings f"
+
+  have finite':"finite (s \<inter> poles)"  
+    using finite unfolding pz_def by (auto elim:rev_finite_subset)
+
+  have isolated:"isolated_singularity_at f z" if "z\<in>s" for z 
+  proof (rule isolated_singularity_at_holomorphic)
+    show "f holomorphic_on (s-(poles-{z})) - {z}" 
+      by (metis Diff_empty Diff_insert Diff_insert0 Diff_subset 
+          f_holo holomorphic_on_subset insert_Diff)
+    show "open (s - (poles - {z}))" 
+      by (metis Diff_Diff_Int Int_Diff assms(2) finite' finite_Diff 
+          finite_imp_closed inf.idem open_Diff)
+    show "z \<in> s - (poles - {z})" 
+      using assms(4) that by auto
+  qed
+
+  have not_ess:"not_essential f w" if "w\<in>s" for w 
+    by (metis Diff_Diff_Int Diff_iff Int_Diff Int_absorb assms(2) 
+        f_holo finite' finite_imp_closed not_essential_holomorphic 
+        open_Diff poles that)
+
+  have nzero:"\<forall>\<^sub>F x in at w. f x \<noteq> 0" if "w\<in>s" for w
+  proof (rule ccontr) 
+    assume "\<not> (\<forall>\<^sub>F x in at w. f x \<noteq> 0)"
+    then have "\<exists>\<^sub>F x in at w. f x = 0" 
+      unfolding not_eventually by simp
+    moreover have "\<forall>\<^sub>F x in at w. x\<in>s" 
+      by (simp add: assms(2) eventually_at_in_open' that)
+    ultimately have "\<exists>\<^sub>F x in at w. x\<in>{w\<in>s. f w = 0}" 
+      apply (elim frequently_rev_mp)
+      by (auto elim:eventually_mono)
+    from frequently_at_imp_islimpt[OF this] 
+    have "w islimpt {w \<in> s. f w = 0}" .
+    then have "infinite({w \<in> s. f w = 0} \<inter> ball w 1)"
+      unfolding islimpt_eq_infinite_ball by auto
+    then have "infinite({w \<in> s. f w = 0})"
+      by auto
+    then have "infinite pz" unfolding pz_def 
+      by (smt (verit) Collect_mono_iff rev_finite_subset)
+    then show False using finite by auto
+  qed
+
+  obtain pts' where pts':"pts' \<subseteq> s \<inter> poles" 
+    "finite pts'" "ff holomorphic_on s - pts'" "\<forall>x\<in>pts'. is_pole ff x"
+    apply (elim get_all_poles_from_remove_sings
+        [of f,folded ff_def,rotated -1])
+    subgoal using f_holo by fastforce
+    using \<open>open s\<close> poles finite' by auto
+
+  have pts'_sub_pz:"{w \<in> s. ff w = 0 \<or> w \<in> pts'} \<subseteq> pz"
+  proof -
+    have "w\<in>poles" if "w\<in>s" "w\<in>pts'" for w 
+      by (meson in_mono le_infE pts'(1) that(2))
+    moreover have "f w=0" if" w\<in>s" "w\<notin>poles" "ff w=0" for w
+    proof -
+      have "\<not> is_pole f w"
+        by (metis DiffI Diff_Diff_Int Diff_subset assms(2) f_holo 
+            finite' finite_imp_closed inf.absorb_iff2 
+            not_is_pole_holomorphic open_Diff that(1) that(2))
+      then have "f \<midarrow>w\<rightarrow> 0" 
+        using remove_sings_eq_0_iff[OF not_ess[OF \<open>w\<in>s\<close>]] \<open>ff w=0\<close>
+        unfolding ff_def by auto
+      moreover have "f analytic_on {w}" 
+        using that(1,2) finite' f_holo assms(2)
+        by (metis Diff_Diff_Int Diff_empty Diff_iff Diff_subset 
+            double_diff finite_imp_closed 
+            holomorphic_on_imp_analytic_at open_Diff)
+      ultimately show ?thesis 
+        using ff_def remove_sings_at_analytic that(3) by presburger
+    qed
+    ultimately show ?thesis unfolding pz_def by auto
+  qed
+
+
+  have "contour_integral g (\<lambda>x. deriv f x * h x / f x)
+          = contour_integral g (\<lambda>x. deriv ff x * h x / ff x)"
+  proof (rule contour_integral_eq)
+    fix x assume "x \<in> path_image g" 
+    have "f analytic_on {x}"
+    proof (rule holomorphic_on_imp_analytic_at[of _ "s-poles"])
+      from finite' 
+      show "open (s - poles)" 
+        using \<open>open s\<close> 
+        by (metis Diff_Compl Diff_Diff_Int Diff_eq finite_imp_closed 
+            open_Diff)
+      show "x \<in> s - poles"
+        using path_img \<open>x \<in> path_image g\<close> unfolding pz_def by auto
+    qed (use f_holo in simp)
+    then show "deriv f x * h x / f x = deriv ff x * h x / ff x"
+      unfolding ff_def by auto
+  qed
+  also have "... = complex_of_real (2 * pi) * \<i> *
+                      (\<Sum>p\<in>{w \<in> s. ff w = 0 \<or> w \<in> pts'}. 
+                        winding_number g p * h p * of_int (zorder ff p))"
+  proof (rule argument_principle[OF \<open>open s\<close> \<open>connected s\<close>, of ff pts' h g])
+    show "path_image g \<subseteq> s - {w \<in> s. ff w = 0 \<or> w \<in> pts'}"
+      using path_img pts'_sub_pz  by auto
+    show "finite {w \<in> s. ff w = 0 \<or> w \<in> pts'}" 
+      using pts'_sub_pz finite 
+      using rev_finite_subset by blast  
+  qed (use pts' assms in auto)
+  also have "... = 2 * pi * \<i> *
+          (\<Sum>p\<in>pz. winding_number g p * h p * zorder f p)"
+  proof -
+    have "(\<Sum>p\<in>{w \<in> s. ff w = 0 \<or> w \<in> pts'}.
+       winding_number g p * h p * of_int (zorder ff p)) =
+      (\<Sum>p\<in>pz. winding_number g p * h p * of_int (zorder f p))"
+    proof (rule sum.mono_neutral_cong_left)
+      have "zorder f w = 0" 
+        if "w\<in>s" " f w = 0 \<or> w \<in> poles" "ff w \<noteq> 0" " w \<notin> pts'"
+        for w
+      proof -
+        define F where "F=laurent_expansion f w"
+        have has_l:"(\<lambda>x. f (w + x)) has_laurent_expansion F"
+          unfolding F_def
+          apply (rule not_essential_has_laurent_expansion)
+          using isolated not_ess \<open>w\<in>s\<close> by auto
+        from has_laurent_expansion_eventually_nonzero_iff[OF this]
+        have "F \<noteq>0"
+          using nzero \<open>w\<in>s\<close> by auto
+        from tendsto_0_subdegree_iff[OF has_l this] 
+        have "f \<midarrow>w\<rightarrow> 0 = (0 < fls_subdegree F)" .
+        moreover have "\<not> (is_pole f w \<or> f \<midarrow>w\<rightarrow> 0)"
+          using remove_sings_eq_0_iff[OF not_ess[OF \<open>w\<in>s\<close>]] \<open>ff w \<noteq> 0\<close>
+          unfolding ff_def by auto
+        moreover have "is_pole f w = (fls_subdegree F < 0)"
+          using is_pole_fls_subdegree_iff[OF has_l] .
+        ultimately have "fls_subdegree F = 0" by auto
+        then show ?thesis
+          using has_laurent_expansion_zorder[OF has_l \<open>F\<noteq>0\<close>] by auto
+      qed
+      then show "\<forall>i\<in>pz - {w \<in> s. ff w = 0 \<or> w \<in> pts'}.
+        winding_number g i * h i * of_int (zorder f i) = 0" 
+        unfolding pz_def by auto
+      show "\<And>x. x \<in> {w \<in> s. ff w = 0 \<or> w \<in> pts'} \<Longrightarrow>
+         winding_number g x * h x * of_int (zorder ff x) =
+         winding_number g x * h x * of_int (zorder f x)"
+        using isolated zorder_remove_sings[of f,folded ff_def] by auto
+    qed (use pts'_sub_pz finite in auto)
+    then show ?thesis by auto
+  qed
+  finally show ?thesis .
+qed
+
+lemma meromorphic_on_imp_isolated_singularity:
+  assumes "f meromorphic_on D pts" "z \<in> D"
+  shows   "isolated_singularity_at f z"
+  by (meson DiffI assms(1) assms(2) holomorphic_on_imp_analytic_at isolated_singularity_at_analytic 
+        meromorphic_imp_open_diff meromorphic_on_def)
+
+lemma meromorphic_imp_not_is_pole:
+  assumes "f meromorphic_on D pts" "z \<in> D - pts"
+  shows   "\<not>is_pole f z"
+proof -
+  from assms have "f analytic_on {z}"
+    using meromorphic_on_imp_analytic_at by blast
+  thus ?thesis
+    using analytic_at not_is_pole_holomorphic by blast
+qed
+
+lemma meromorphic_all_poles_iff_empty [simp]: "f meromorphic_on pts pts \<longleftrightarrow> pts = {}"
+  by (auto simp: meromorphic_on_def holomorphic_on_def open_imp_islimpt)
+
+lemma meromorphic_imp_nonsingular_point_exists:
+  assumes "f meromorphic_on A pts" "A \<noteq> {}"
+  obtains x where "x \<in> A - pts"
+proof -
+  have "A \<noteq> pts"
+    using assms by auto
+  moreover have "pts \<subseteq> A"
+    using assms by (auto simp: meromorphic_on_def)
+  ultimately show ?thesis
+    using that by blast
+qed
+
+lemma meromorphic_frequently_const_imp_const:
+  assumes "f meromorphic_on A pts" "connected A"
+  assumes "frequently (\<lambda>w. f w = c) (at z)"
+  assumes "z \<in> A - pts"
+  assumes "w \<in> A - pts"
+  shows   "f w = c"
+proof -
+  have "f w - c = 0"
+  proof (rule analytic_continuation[where f = "\<lambda>z. f z - c"])
+    show "(\<lambda>z. f z - c) holomorphic_on (A - pts)"
+      by (intro holomorphic_intros meromorphic_imp_holomorphic[OF assms(1)])
+    show [intro]: "open (A - pts)"
+      using assms meromorphic_imp_open_diff by blast
+    show "connected (A - pts)"
+      using assms meromorphic_imp_connected_diff by blast
+    show "{z\<in>A-pts. f z = c} \<subseteq> A - pts"
+      by blast
+    have "eventually (\<lambda>z. z \<in> A - pts) (at z)"
+      using assms by (intro eventually_at_in_open') auto
+    hence "frequently (\<lambda>z. f z = c \<and> z \<in> A - pts) (at z)"
+      by (intro frequently_eventually_frequently assms)
+    thus "z islimpt {z\<in>A-pts. f z = c}"
+      by (simp add: islimpt_conv_frequently_at conj_commute)
+  qed (use assms in auto)
+  thus ?thesis
+    by simp
+qed
+
+lemma meromorphic_imp_eventually_neq:
+  assumes "f meromorphic_on A pts" "connected A" "\<not>f constant_on A - pts"
+  assumes "z \<in> A - pts"
+  shows   "eventually (\<lambda>z. f z \<noteq> c) (at z)"
+proof (rule ccontr)
+  assume "\<not>eventually (\<lambda>z. f z \<noteq> c) (at z)"
+  hence *: "frequently (\<lambda>z. f z = c) (at z)"
+    by (auto simp: frequently_def)
+  have "\<forall>w\<in>A-pts. f w = c"
+    using meromorphic_frequently_const_imp_const [OF assms(1,2) * assms(4)] by blast
+  hence "f constant_on A - pts"
+    by (auto simp: constant_on_def)
+  thus False
+    using assms(3) by contradiction
+qed
+
+lemma meromorphic_frequently_const_imp_const':
+  assumes "f meromorphic_on A pts" "connected A" "\<forall>w\<in>pts. is_pole f w"
+  assumes "frequently (\<lambda>w. f w = c) (at z)"
+  assumes "z \<in> A"
+  assumes "w \<in> A"
+  shows   "f w = c"
+proof -
+  have "\<not>is_pole f z"
+    using frequently_const_imp_not_is_pole[OF assms(4)] .
+  with assms have z: "z \<in> A - pts"
+    by auto
+  have *: "f w = c" if "w \<in> A - pts" for w
+    using that meromorphic_frequently_const_imp_const [OF assms(1,2,4) z] by auto
+  have "\<not>is_pole f u" if "u \<in> A" for u
+  proof -
+    have "is_pole f u \<longleftrightarrow> is_pole (\<lambda>_. c) u"
+    proof (rule is_pole_cong)
+      have "eventually (\<lambda>w. w \<in> A - (pts - {u}) - {u}) (at u)"
+        by (intro eventually_at_in_open meromorphic_imp_open_diff' [OF assms(1)]) (use that in auto)
+      thus "eventually (\<lambda>w. f w = c) (at u)"
+        by eventually_elim (use * in auto)
+    qed auto
+    thus ?thesis
+      by auto
+  qed
+  moreover have "pts \<subseteq> A"
+    using assms(1) by (simp add: meromorphic_on_def)
+  ultimately have "pts = {}"
+    using assms(3) by auto
+  with * and \<open>w \<in> A\<close> show ?thesis
+    by blast
+qed
+
+lemma meromorphic_imp_eventually_neq':
+  assumes "f meromorphic_on A pts" "connected A" "\<forall>w\<in>pts. is_pole f w" "\<not>f constant_on A"
+  assumes "z \<in> A"
+  shows   "eventually (\<lambda>z. f z \<noteq> c) (at z)"
+proof (rule ccontr)
+  assume "\<not>eventually (\<lambda>z. f z \<noteq> c) (at z)"
+  hence *: "frequently (\<lambda>z. f z = c) (at z)"
+    by (auto simp: frequently_def)
+  have "\<forall>w\<in>A. f w = c"
+    using meromorphic_frequently_const_imp_const' [OF assms(1,2,3) * assms(5)] by blast
+  hence "f constant_on A"
+    by (auto simp: constant_on_def)
+  thus False
+    using assms(4) by contradiction
+qed
+
+lemma zorder_eq_0_iff_meromorphic:
+  assumes "f meromorphic_on A pts" "\<forall>z\<in>pts. is_pole f z" "z \<in> A"
+  assumes "eventually (\<lambda>x. f x \<noteq> 0) (at z)"
+  shows   "zorder f z = 0 \<longleftrightarrow> \<not>is_pole f z \<and> f z \<noteq> 0"
+proof (cases "z \<in> pts")
+  case True
+  from assms obtain F where F: "(\<lambda>x. f (z + x)) has_laurent_expansion F"
+    by (metis True meromorphic_on_def not_essential_has_laurent_expansion) (* TODO: better lemmas *)
+  from F and assms(4) have [simp]: "F \<noteq> 0"
+    using has_laurent_expansion_eventually_nonzero_iff by blast
+  show ?thesis using True assms(2)
+    using is_pole_fls_subdegree_iff [OF F] has_laurent_expansion_zorder [OF F]
+    by auto
+next
+  case False
+  have ana: "f analytic_on {z}"
+    using meromorphic_on_imp_analytic_at False assms by blast
+  hence "\<not>is_pole f z"
+    using analytic_at not_is_pole_holomorphic by blast
+  moreover have "frequently (\<lambda>w. f w \<noteq> 0) (at z)"
+    using assms(4) by (intro eventually_frequently) auto
+  ultimately show ?thesis using zorder_eq_0_iff[OF ana] False
+    by auto
+qed
+
+lemma zorder_pos_iff_meromorphic:
+  assumes "f meromorphic_on A pts" "\<forall>z\<in>pts. is_pole f z" "z \<in> A"
+  assumes "eventually (\<lambda>x. f x \<noteq> 0) (at z)"
+  shows   "zorder f z > 0 \<longleftrightarrow> \<not>is_pole f z \<and> f z = 0"
+proof (cases "z \<in> pts")
+  case True
+  from assms obtain F where F: "(\<lambda>x. f (z + x)) has_laurent_expansion F"
+    by (metis True meromorphic_on_def not_essential_has_laurent_expansion) (* TODO: better lemmas *)
+  from F and assms(4) have [simp]: "F \<noteq> 0"
+    using has_laurent_expansion_eventually_nonzero_iff by blast
+  show ?thesis using True assms(2)
+    using is_pole_fls_subdegree_iff [OF F] has_laurent_expansion_zorder [OF F]
+    by auto
+next
+  case False
+  have ana: "f analytic_on {z}"
+    using meromorphic_on_imp_analytic_at False assms by blast
+  hence "\<not>is_pole f z"
+    using analytic_at not_is_pole_holomorphic by blast
+  moreover have "frequently (\<lambda>w. f w \<noteq> 0) (at z)"
+    using assms(4) by (intro eventually_frequently) auto
+  ultimately show ?thesis using zorder_pos_iff'[OF ana] False
+    by auto
+qed
+
+lemma zorder_neg_iff_meromorphic:
+  assumes "f meromorphic_on A pts" "\<forall>z\<in>pts. is_pole f z" "z \<in> A"
+  assumes "eventually (\<lambda>x. f x \<noteq> 0) (at z)"
+  shows   "zorder f z < 0 \<longleftrightarrow> is_pole f z"
+proof -
+  have "frequently (\<lambda>x. f x \<noteq> 0) (at z)"
+    using assms by (intro eventually_frequently) auto
+  moreover from assms have "isolated_singularity_at f z" "not_essential f z"
+    using meromorphic_on_imp_isolated_singularity meromorphic_on_imp_not_essential by blast+
+  ultimately show ?thesis
+    using isolated_pole_imp_neg_zorder neg_zorder_imp_is_pole by blast
+qed
+
+lemma meromorphic_on_imp_discrete:
+  assumes mero:"f meromorphic_on S pts" and "connected S" 
+    and nconst:"\<not> (\<forall>w\<in>S - pts. f w = c)"
+  shows "discrete {x\<in>S. f x=c}" 
+proof -
+  define g where "g=(\<lambda>x. f x - c)"
+  have "\<forall>\<^sub>F w in at z. g w \<noteq> 0" if "z \<in> S" for z
+  proof (rule nconst_imp_nzero_neighbour'[of g S pts z])
+    show "g meromorphic_on S pts" using mero unfolding g_def
+      by (auto intro:meromorphic_intros)
+    show "\<not> (\<forall>w\<in>S - pts. g w = 0)" using nconst unfolding g_def by auto
+  qed fact+
+  then show ?thesis 
+    unfolding discrete_altdef g_def 
+    using eventually_mono by fastforce
+qed
+
+lemma meromorphic_isolated_in:
+  assumes merf: "f meromorphic_on D pts" "p\<in>pts"
+  shows "p isolated_in pts"
+  by (meson assms isolated_in_islimpt_iff meromorphic_on_def subsetD)
+
+lemma remove_sings_constant_on:
+  assumes merf: "f meromorphic_on D pts" and "connected D"
+      and const:"f constant_on (D - pts)"
+    shows "(remove_sings f) constant_on D"
+proof -
+  have remove_sings_const: "remove_sings f constant_on D - pts" 
+    using const
+    by (metis constant_onE merf meromorphic_on_imp_analytic_at remove_sings_at_analytic)
+
+  have ?thesis if "D = {}"
+    using that unfolding constant_on_def by auto
+  moreover have ?thesis if "D\<noteq>{}" "{x\<in>pts. is_pole f x} = {}"
+  proof -
+    obtain \<xi> where "\<xi> \<in> (D - pts)" "\<xi> islimpt (D - pts)"
+    proof -
+      have "open (D - pts)"
+        using meromorphic_imp_open_diff[OF merf] .
+      moreover have "(D - pts) \<noteq> {}" using \<open>D\<noteq>{}\<close>
+        by (metis Diff_empty closure_empty merf 
+            meromorphic_pts_closure subset_empty)
+      ultimately show ?thesis using open_imp_islimpt that by auto
+    qed
+    moreover have "remove_sings f holomorphic_on D"
+      using remove_sings_holomorphic_on[OF merf] that by auto
+    moreover note remove_sings_const
+    moreover have "open D" 
+      using assms(1) meromorphic_on_def by blast
+    ultimately show ?thesis
+      using Conformal_Mappings.analytic_continuation'
+              [of "remove_sings f" D "D-pts" \<xi>] \<open>connected D\<close>
+      by auto
+  qed
+  moreover have ?thesis if "D\<noteq>{}" "{x\<in>pts. is_pole f x} \<noteq> {}"
+  proof -
+    define PP where "PP={x\<in>D. is_pole f x}"
+    have "remove_sings f meromorphic_on D PP"
+      using merf unfolding PP_def
+      apply (elim remove_sings_meromorphic_on)
+      subgoal using assms(1) meromorphic_on_def by force
+      subgoal using meromorphic_pole_subset merf by auto
+      done
+    moreover have "remove_sings f constant_on D - PP"
+    proof -
+      obtain \<xi> where "\<xi> \<in> f ` (D - pts)" 
+        by (metis Diff_empty Diff_eq_empty_iff \<open>D \<noteq> {}\<close> assms(1) 
+            closure_empty ex_in_conv imageI meromorphic_pts_closure)
+      have \<xi>:"\<forall>x\<in>D - pts. f x = \<xi>"    
+        by (metis \<open>\<xi> \<in> f ` (D - pts)\<close> assms(3) constant_on_def image_iff)
+
+      have "remove_sings f x = \<xi>" if "x\<in>D - PP" for x
+      proof (cases "x\<in>pts")
+        case True
+        then have"x isolated_in pts" 
+          using meromorphic_isolated_in[OF merf] by auto
+        then obtain T0 where T0:"open T0" "T0 \<inter> pts = {x}"
+          unfolding isolated_in_def by auto
+        obtain T1 where T1:"open T1" "x\<in>T1" "T1 \<subseteq> D"
+          using merf unfolding meromorphic_on_def 
+          using True by blast
+        define T2 where "T2 = T1 \<inter> T0"
+        have "open T2" "x\<in>T2" "T2 - {x} \<subseteq> D - pts"
+          using T0 T1 unfolding T2_def by auto
+        then have "\<forall>w\<in>T2. w\<noteq>x \<longrightarrow> f w =\<xi>"
+          using \<xi> by auto
+        then have "\<forall>\<^sub>F x in at x. f x = \<xi>" 
+          unfolding eventually_at_topological
+          using \<open>open T2\<close> \<open>x\<in>T2\<close> by auto
+        then have "f \<midarrow>x\<rightarrow> \<xi>" 
+          using tendsto_eventually by auto
+        then show ?thesis by blast
+      next
+        case False
+        then show ?thesis 
+          using \<open>\<forall>x\<in>D - pts. f x = \<xi>\<close> assms(1) 
+            meromorphic_on_imp_analytic_at that by auto
+      qed
+
+      then show ?thesis unfolding constant_on_def by auto
+    qed
+
+    moreover have "is_pole (remove_sings f) x" if "x\<in>PP" for x
+    proof -
+      have "isolated_singularity_at f x"
+        by (metis (mono_tags, lifting) DiffI PP_def assms(1) 
+            isolated_singularity_at_analytic mem_Collect_eq 
+            meromorphic_on_def meromorphic_on_imp_analytic_at that)
+      then show ?thesis using that unfolding PP_def by simp
+    qed
+    ultimately show ?thesis
+      using meromorphic_imp_constant_on
+            [of "remove_sings f" D PP]
+      by auto
+  qed
+  ultimately show ?thesis by auto
+qed
+
+lemma meromorphic_eq_meromorphic_extend:
+  assumes "f meromorphic_on A pts1" "g meromorphic_on A pts1" "\<not>z islimpt pts2"
+  assumes "\<And>z. z \<in> A - pts2 \<Longrightarrow> f z = g z" "pts1 \<subseteq> pts2" "z \<in> A - pts1"
+  shows   "f z = g z"
+proof -
+  have "g analytic_on {z}"
+    using assms by (intro meromorphic_on_imp_analytic_at[OF assms(2)]) auto
+  hence "g \<midarrow>z\<rightarrow> g z"
+    using analytic_at_imp_isCont isContD by blast
+  also have "?this \<longleftrightarrow> f \<midarrow>z\<rightarrow> g z"
+  proof (intro filterlim_cong)
+    have "eventually (\<lambda>w. w \<notin> pts2) (at z)"
+      using assms by (auto simp: islimpt_conv_frequently_at frequently_def)
+    moreover have "eventually (\<lambda>w. w \<in> A) (at z)"
+      using assms by (intro eventually_at_in_open') (auto simp: meromorphic_on_def)
+    ultimately show "\<forall>\<^sub>F x in at z. g x = f x"
+      by eventually_elim (use assms in auto)
+  qed auto
+  finally have "f \<midarrow>z\<rightarrow> g z" .
+  moreover have "f analytic_on {z}"
+    using assms by (intro meromorphic_on_imp_analytic_at[OF assms(1)]) auto
+  hence "f \<midarrow>z\<rightarrow> f z"
+    using analytic_at_imp_isCont isContD by blast
+  ultimately show ?thesis
+    using tendsto_unique by force
+qed
+
+lemma meromorphic_constant_on_extend:
+  assumes "f constant_on A - pts1" "f meromorphic_on A pts1" "f meromorphic_on A pts2" "pts2 \<subseteq> pts1"
+  shows   "f constant_on A - pts2"
+proof -
+  from assms(1) obtain c where c: "\<And>z. z \<in> A - pts1 \<Longrightarrow> f z = c"
+    unfolding constant_on_def by auto
+  have "f z = c" if "z \<in> A - pts2" for z
+    using assms(3)
+  proof (rule meromorphic_eq_meromorphic_extend[where z = z])
+    show "(\<lambda>a. c) meromorphic_on A pts2"
+      by (intro meromorphic_on_const) (use assms in \<open>auto simp: meromorphic_on_def\<close>)
+    show "\<not>z islimpt pts1"
+      using that assms by (auto simp: meromorphic_on_def)
+  qed (use assms c that in auto)
+  thus ?thesis
+    by (auto simp: constant_on_def)
+qed
+
+lemma meromorphic_remove_sings_constant_on_imp_constant_on:
+  assumes "f meromorphic_on A pts"
+  assumes "remove_sings f constant_on A"
+  shows   "f constant_on A - pts"
+proof -
+  from assms(2) obtain c where c: "\<And>z. z \<in> A \<Longrightarrow> remove_sings f z = c"
+    by (auto simp: constant_on_def)
+  have "f z = c" if "z \<in> A - pts" for z
+    using meromorphic_on_imp_analytic_at[OF assms(1) that] c[of z] that
+    by auto
+  thus ?thesis
+    by (auto simp: constant_on_def)
+qed
+
+
+
+
+definition singularities_on :: "complex set \<Rightarrow> (complex \<Rightarrow> complex) \<Rightarrow> complex set" where
+  "singularities_on A f =
+     {z\<in>A. isolated_singularity_at f z \<and> not_essential f z \<and> \<not>f analytic_on {z}}"
+
+lemma singularities_on_subset: "singularities_on A f \<subseteq> A"
+  by (auto simp: singularities_on_def)
+
+lemma pole_in_singularities_on:
+  assumes "f meromorphic_on A pts" "z \<in> A" "is_pole f z"
+  shows   "z \<in> singularities_on A f"
+  unfolding singularities_on_def not_essential_def using assms
+  using analytic_at_imp_no_pole meromorphic_on_imp_isolated_singularity by force
+
+
+lemma meromorphic_on_subset_pts:
+  assumes "f meromorphic_on A pts" "pts' \<subseteq> pts" "f analytic_on pts - pts'"
+  shows   "f meromorphic_on A pts'"
+proof
+  show "open A" "pts' \<subseteq> A"
+    using assms by (auto simp: meromorphic_on_def)
+  show "isolated_singularity_at f z" "not_essential f z" if "z \<in> pts'" for z
+    using assms that by (auto simp: meromorphic_on_def)
+  show "\<not>z islimpt pts'" if "z \<in> A" for z
+    using assms that islimpt_subset unfolding meromorphic_on_def by blast
+  have "f analytic_on A - pts"
+    using assms(1) meromorphic_imp_analytic by blast
+  with assms have "f analytic_on (A - pts) \<union> (pts - pts')"
+    by (subst analytic_on_Un) auto
+  also have "(A - pts) \<union> (pts - pts') = A - pts'"
+    using assms by (auto simp: meromorphic_on_def)
+  finally show "f holomorphic_on A - pts'"
+    using analytic_imp_holomorphic by blast
+qed
+
+lemma meromorphic_on_imp_superset_singularities_on:
+  assumes "f meromorphic_on A pts"
+  shows   "singularities_on A f \<subseteq> pts"
+proof
+  fix z assume "z \<in> singularities_on A f"
+  hence "z \<in> A" "\<not>f analytic_on {z}"
+    by (auto simp: singularities_on_def)
+  with assms show "z \<in> pts"
+    by (meson DiffI meromorphic_on_imp_analytic_at)
+qed  
+
+lemma meromorphic_on_singularities_on:
+  assumes "f meromorphic_on A pts"
+  shows   "f meromorphic_on A (singularities_on A f)"
+  using assms meromorphic_on_imp_superset_singularities_on[OF assms]
+proof (rule meromorphic_on_subset_pts)
+  have "f analytic_on {z}" if "z \<in> pts - singularities_on A f" for z
+    using that assms by (auto simp: singularities_on_def meromorphic_on_def)
+  thus "f analytic_on pts - singularities_on A f"
+    using analytic_on_analytic_at by blast
+qed
+
+theorem Residue_theorem_inside:
+  assumes f: "f meromorphic_on s pts"
+             "simply_connected s"
+  assumes g: "valid_path g"
+             "pathfinish g = pathstart g"
+             "path_image g \<subseteq> s - pts"
+  defines "pts1 \<equiv> pts \<inter> inside (path_image g)"
+  shows "finite pts1"
+    and "contour_integral g f = 2 * pi * \<i> * (\<Sum>p\<in>pts1. winding_number g p * residue f p)"
+proof - 
+  note [dest] = valid_path_imp_path
+  have cl_g [intro]: "closed (path_image g)"
+    using g by (auto intro!: closed_path_image)
+  have "open s"
+    using f(1) by (auto simp: meromorphic_on_def)
+  define pts2 where "pts2 = pts - pts1"
+
+  define A where "A = path_image g \<union> inside (path_image g)"
+  have "closed A"
+    unfolding A_def using g by (intro closed_path_image_Un_inside) auto
+  moreover have "bounded A"
+    unfolding A_def using g by (auto intro!: bounded_path_image bounded_inside)
+  ultimately have 1: "compact A"
+    using compact_eq_bounded_closed by blast
+  have 2: "open (s - pts2)"
+    using f by (auto intro!: meromorphic_imp_open_diff' [OF f(1)] simp: pts2_def)
+  have 3: "A \<subseteq> s - pts2"
+    unfolding A_def pts2_def pts1_def
+    using f(2) g(3) 2 subset_simply_connected_imp_inside_subset[of s "path_image g"] \<open>open s\<close>
+    by auto
+
+  obtain \<epsilon> where \<epsilon>: "\<epsilon> > 0" "(\<Union>x\<in>A. ball x \<epsilon>) \<subseteq> s - pts2"
+    using compact_subset_open_imp_ball_epsilon_subset[OF 1 2 3] by blast
+  define B where "B = (\<Union>x\<in>A. ball x \<epsilon>)"
+
+  have "finite (A \<inter> pts)"
+    using 1 3 by (intro meromorphic_compact_finite_pts[OF f(1)]) auto
+  also have "A \<inter> pts = pts1"
+    unfolding pts1_def using g by (auto simp: A_def)
+  finally show fin: "finite pts1" .
+
+  show "contour_integral g f = 2 * pi * \<i> * (\<Sum>p\<in>pts1. winding_number g p * residue f p)"
+  proof (rule Residue_theorem)
+    show "open B"
+      by (auto simp: B_def)
+  next
+    have "connected A"
+      unfolding A_def using g
+      by (intro connected_with_inside closed_path_image connected_path_image) auto
+    hence "connected (A \<union> B)"
+      unfolding B_def using g \<open>\<epsilon> > 0\<close> f(2)
+      by (intro connected_Un_UN connected_path_image valid_path_imp_path)
+         (auto simp: simply_connected_imp_connected)
+    also have "A \<union> B = B"
+      using \<epsilon>(1) by (auto simp: B_def)
+    finally show "connected B" .
+  next
+    have "f holomorphic_on (s - pts)"
+      by (intro meromorphic_imp_holomorphic f)
+    moreover have "B - pts1 \<subseteq> s - pts"
+      using \<epsilon> unfolding B_def by (auto simp: pts1_def pts2_def)
+    ultimately show "f holomorphic_on (B - pts1)"
+      by (rule holomorphic_on_subset)
+  next
+    have "path_image g \<subseteq> A - pts1"
+      using g unfolding pts1_def by (auto simp: A_def)
+    also have "\<dots> \<subseteq> B - pts1"
+      unfolding B_def using \<epsilon>(1) by auto
+    finally show "path_image g \<subseteq> B - pts1" .
+  next
+    show "\<forall>z. z \<notin> B \<longrightarrow> winding_number g z = 0"
+    proof safe
+      fix z assume z: "z \<notin> B"
+      hence "z \<notin> A"
+        using \<epsilon>(1) by (auto simp: B_def)
+      hence "z \<in> outside (path_image g)"
+        unfolding A_def by (simp add: union_with_inside)
+      thus "winding_number g z = 0"
+        using g by (intro winding_number_zero_in_outside) auto
+    qed
+  qed (use g fin in auto)
+qed
+
+theorem Residue_theorem':
+  assumes f: "f meromorphic_on s pts"
+             "simply_connected s"
+  assumes g: "valid_path g" 
+             "pathfinish g = pathstart g"
+             "path_image g \<subseteq> s - pts"
+  assumes pts': "finite pts'"
+                "pts' \<subseteq> s"
+                "\<And>z. z \<in> pts - pts' \<Longrightarrow> winding_number g z = 0"
+  shows "contour_integral g f = 2 * pi * \<i> * (\<Sum>p\<in>pts'. winding_number g p * residue f p)"
+proof -
+  note [dest] = valid_path_imp_path
+  define pts1 where "pts1 = pts \<inter> inside (path_image g)"
+
+  have "contour_integral g f = 2 * pi * \<i> * (\<Sum>p\<in>pts1. winding_number g p * residue f p)"
+    unfolding pts1_def by (intro Residue_theorem_inside[OF f g])
+  also have "(\<Sum>p\<in>pts1. winding_number g p * residue f p) =
+             (\<Sum>p\<in>pts'. winding_number g p * residue f p)"
+  proof (intro sum.mono_neutral_cong refl)
+    show "finite pts1"
+      unfolding pts1_def by (intro Residue_theorem_inside[OF f g])
+    show "finite pts'"
+      by fact
+  next
+    fix z assume z: "z \<in> pts' - pts1"
+    show "winding_number g z * residue f z = 0"
+    proof (cases "z \<in> pts")
+      case True
+      with z have "z \<notin> path_image g \<union> inside (path_image g)"
+        using g(3) by (auto simp: pts1_def)
+      hence "z \<in> outside (path_image g)"
+        by (simp add: union_with_inside)
+      hence "winding_number g z = 0"
+        using g by (intro winding_number_zero_in_outside) auto
+      thus ?thesis
+        by simp
+    next
+      case False
+      with z pts' have "z \<in> s - pts"
+        by auto
+      with f(1) have "f analytic_on {z}"
+        by (intro meromorphic_on_imp_analytic_at)
+      hence "residue f z = 0"
+        using analytic_at residue_holo by blast
+      thus ?thesis
+        by simp
+    qed
+  next
+    fix z assume z: "z \<in> pts1 - pts'"
+    hence "winding_number g z = 0"
+      using pts' by (auto simp: pts1_def)
+    thus "winding_number g z * residue f z = 0"
+      by simp
+  qed
+  finally show ?thesis .
+qed
+
+end
\ No newline at end of file
diff -r 29032b496f2e -r c6b50597abbc src/HOL/Complex_Analysis/Residue_Theorem.thy
--- a/src/HOL/Complex_Analysis/Residue_Theorem.thy	Thu Feb 16 10:42:39 2023 +0000
+++ b/src/HOL/Complex_Analysis/Residue_Theorem.thy	Thu Feb 16 12:21:21 2023 +0000
@@ -3,6 +3,34 @@
   imports Complex_Residues "HOL-Library.Landau_Symbols"
 begin
 
+text \<open>Could be moved to a previous theory importing both Landau Symbols and Elementary Metric Spaces\<close>
+lemma continuous_bounded_at_infinity_imp_bounded:
+  fixes f :: "real \<Rightarrow> 'a :: real_normed_field"
+  assumes "f \<in> O[at_bot](\<lambda>_. 1)"
+  assumes "f \<in> O[at_top](\<lambda>_. 1)"
+  assumes "continuous_on UNIV f"
+  shows   "bounded (range f)"
+proof -
+  from assms(1) obtain c1 where "eventually (\<lambda>x. norm (f x) \<le> c1) at_bot"
+    by (auto elim!: landau_o.bigE)
+  then obtain x1 where x1: "\<And>x. x \<le> x1 \<Longrightarrow> norm (f x) \<le> c1"
+    by (auto simp: eventually_at_bot_linorder)
+  from assms(2) obtain c2 where "eventually (\<lambda>x. norm (f x) \<le> c2) at_top"
+    by (auto elim!: landau_o.bigE)
+  then obtain x2 where x2: "\<And>x. x \<ge> x2 \<Longrightarrow> norm (f x) \<le> c2"
+    by (auto simp: eventually_at_top_linorder)
+  have "compact (f ` {x1..x2})"
+    by (intro compact_continuous_image continuous_on_subset[OF assms(3)]) auto
+  hence "bounded (f ` {x1..x2})"
+    by (rule compact_imp_bounded)
+  then obtain c3 where c3: "\<And>x. x \<in> {x1..x2} \<Longrightarrow> norm (f x) \<le> c3"
+    unfolding bounded_iff by fast
+  have "norm (f x) \<le> Max {c1, c2, c3}" for x
+    by (cases "x \<le> x1"; cases "x \<ge> x2") (use x1 x2 c3 in \<open>auto simp: le_max_iff_disj\<close>)
+  thus ?thesis
+    unfolding bounded_iff by blast
+qed
+
 subsection \<open>Cauchy's residue theorem\<close>
 
 lemma get_integrable_path:
diff -r 29032b496f2e -r c6b50597abbc src/HOL/Complex_Analysis/Riemann_Mapping.thy
--- a/src/HOL/Complex_Analysis/Riemann_Mapping.thy	Thu Feb 16 10:42:39 2023 +0000
+++ b/src/HOL/Complex_Analysis/Riemann_Mapping.thy	Thu Feb 16 12:21:21 2023 +0000
@@ -1245,21 +1245,9 @@
   interpret SC_Chain
     using assms by (simp add: SC_Chain_def)
   have "?fp \<and> ?ucc \<and> ?ei"
-proof -
-  have *: "\<lbrakk>\<alpha> \<Longrightarrow> \<beta>; \<beta> \<Longrightarrow> \<gamma>; \<gamma> \<Longrightarrow> \<delta>; \<delta> \<Longrightarrow> \<alpha>\<rbrakk>
-           \<Longrightarrow> (\<alpha> \<longleftrightarrow> \<beta>) \<and> (\<alpha> \<longleftrightarrow> \<gamma>) \<and> (\<alpha> \<longleftrightarrow> \<delta>)" for \<alpha> \<beta> \<gamma> \<delta>
-    by blast
-  show ?thesis
-    apply (rule *)
-    using frontier_properties simply_connected_imp_connected apply blast
-apply clarify
-    using unbounded_complement_components simply_connected_imp_connected apply blast
-    using empty_inside apply blast
-    using empty_inside_imp_simply_connected apply blast
-    done
-qed
+    using empty_inside empty_inside_imp_simply_connected frontier_properties unbounded_complement_components winding_number_zero by blast
   then show ?fp ?ucc ?ei
-    by safe
+    by blast+
 qed
 
 lemma simply_connected_iff_simple:
@@ -1270,6 +1258,12 @@
    apply (metis DIM_complex assms(2) cobounded_has_bounded_component double_compl order_refl)
   by (meson assms inside_bounded_complement_connected_empty simply_connected_eq_empty_inside simply_connected_eq_unbounded_complement_components)
 
+lemma subset_simply_connected_imp_inside_subset:
+  fixes A :: "complex set"
+  assumes "simply_connected A" "open A" "B \<subseteq> A"
+  shows   "inside B \<subseteq> A" 
+by (metis assms Diff_eq_empty_iff inside_mono subset_empty simply_connected_eq_empty_inside)
+
 subsection\<open>Further equivalences based on continuous logs and sqrts\<close>
 
 context SC_Chain
@@ -1299,9 +1293,7 @@
              and expg: "\<And>z. z \<in> ball 0 1 \<Longrightarrow> (f \<circ> k) z = exp (g z)"
     proof (rule continuous_logarithm_on_ball)
       show "continuous_on (ball 0 1) (f \<circ> k)"
-        apply (rule continuous_on_compose [OF contk])
-        using kim continuous_on_subset [OF contf]
-        by blast
+        using contf continuous_on_compose contk kim by blast
       show "\<And>z. z \<in> ball 0 1 \<Longrightarrow> (f \<circ> k) z \<noteq> 0"
         using kim nz by auto
     qed auto
@@ -1438,9 +1430,7 @@
 lemma Borsukian_eq_simply_connected:
   fixes S :: "complex set"
   shows "open S \<Longrightarrow> Borsukian S \<longleftrightarrow> (\<forall>C \<in> components S. simply_connected C)"
-apply (auto simp: Borsukian_componentwise_eq open_imp_locally_connected)
-  using in_components_connected open_components simply_connected_eq_Borsukian apply blast
-  using open_components simply_connected_eq_Borsukian by blast
+  by (meson Borsukian_componentwise_eq in_components_connected open_components open_imp_locally_connected simply_connected_eq_Borsukian)
 
 lemma Borsukian_separation_open_closed:
   fixes S :: "complex set"
@@ -1451,7 +1441,7 @@
   assume "open S"
   show ?thesis
     unfolding Borsukian_eq_simply_connected [OF \<open>open S\<close>]
-    by (meson \<open>open S\<close> \<open>bounded S\<close> bounded_subset in_components_connected in_components_subset nonseparation_by_component_eq open_components simply_connected_iff_simple)
+    by (metis \<open>open S\<close> \<open>bounded S\<close> bounded_subset in_components_maximal nonseparation_by_component_eq open_components simply_connected_iff_simple)
 next
   assume "closed S"
   with \<open>bounded S\<close> show ?thesis
@@ -1659,10 +1649,8 @@
 proof
   assume ?lhs
   then show ?rhs
-    apply (auto simp: winding_number_homotopic_loops_null_eq [OF assms])
-    apply (rule homotopic_loops_imp_homotopic_paths_null)
-    apply (simp add: linepath_refl)
-    done
+    using homotopic_loops_imp_homotopic_paths_null 
+    by (force simp add: linepath_refl winding_number_homotopic_loops_null_eq [OF assms])
 next
   assume ?rhs
   then show ?lhs
@@ -1701,11 +1689,7 @@
   then show ?rhs
     using homotopic_paths_imp_pathstart assms
     by (fastforce simp add: dest: homotopic_paths_imp_homotopic_loops homotopic_paths_loop_parts)
-next
-  assume ?rhs
-  then show ?lhs
-    by (simp add: winding_number_homotopic_paths)
-qed
+qed (simp add: winding_number_homotopic_paths)
 
 lemma winding_number_homotopic_loops_eq:
   assumes "path p" and \<zeta>p: "\<zeta> \<notin> path_image p"
@@ -1725,17 +1709,20 @@
   then have "pathstart r \<noteq> \<zeta>" by blast
   have "homotopic_loops (- {\<zeta>}) p (r +++ q +++ reversepath r)"
   proof (rule homotopic_paths_imp_homotopic_loops)
-    show "homotopic_paths (- {\<zeta>}) p (r +++ q +++ reversepath r)"
-      by (metis (mono_tags, opaque_lifting) \<open>path r\<close> L \<zeta>p \<zeta>q \<open>path p\<close> \<open>path q\<close> homotopic_loops_conjugate loops not_in_path_image_join paf pas path_image_reversepath path_imp_reversepath path_join_eq pathfinish_join pathfinish_reversepath  pathstart_join pathstart_reversepath rim subset_Compl_singleton winding_number_homotopic_loops winding_number_homotopic_paths_eq)
+    have "path (r +++ q +++ reversepath r)"
+      by (simp add: \<open>path r\<close> \<open>path q\<close> loops paf)
+    moreover have "\<zeta> \<notin> path_image (r +++ q +++ reversepath r)"
+      by (metis \<zeta>q not_in_path_image_join path_image_reversepath rim subset_Compl_singleton)
+    moreover have "homotopic_loops (- {\<zeta>}) (r +++ q +++ reversepath r) q"
+      using \<open>path q\<close> \<open>path r\<close> \<zeta>q homotopic_loops_conjugate loops(2) paf rim by blast
+    ultimately show "homotopic_paths (- {\<zeta>}) p (r +++ q +++ reversepath r)"
+      using loops pathfinish_join pathfinish_reversepath pathstart_join
+      by (metis L \<zeta>p \<open>path p\<close> pas winding_number_homotopic_loops winding_number_homotopic_paths_eq)
   qed (use loops pas in auto)
   moreover have "homotopic_loops (- {\<zeta>}) (r +++ q +++ reversepath r) q"
     using rim \<zeta>q by (auto simp: homotopic_loops_conjugate paf \<open>path q\<close> \<open>path r\<close> loops)
   ultimately show ?rhs
     using homotopic_loops_trans by metis
-next
-  assume ?rhs
-  then show ?lhs
-    by (simp add: winding_number_homotopic_loops)
-qed
+qed (simp add: winding_number_homotopic_loops)
 
 end
diff -r 29032b496f2e -r c6b50597abbc src/HOL/Complex_Analysis/Winding_Numbers.thy
--- a/src/HOL/Complex_Analysis/Winding_Numbers.thy	Thu Feb 16 10:42:39 2023 +0000
+++ b/src/HOL/Complex_Analysis/Winding_Numbers.thy	Thu Feb 16 12:21:21 2023 +0000
@@ -901,6 +901,16 @@
     by metis
 qed
 
+lemma bounded_winding_number_nz:
+  assumes "path g" "pathfinish g = pathstart g"
+  shows   "bounded {z. winding_number g z \<noteq> 0}"
+proof -
+  obtain B where "\<And>x. norm x \<ge> B \<Longrightarrow> winding_number g x = 0"
+    using winding_number_zero_at_infinity[OF assms] by auto
+  thus ?thesis
+    unfolding bounded_iff by (intro exI[of _ "B + 1"]) force
+qed
+  
 lemma winding_number_zero_point:
     "\<lbrakk>path \<gamma>; convex S; pathfinish \<gamma> = pathstart \<gamma>; open S; path_image \<gamma> \<subseteq> S\<rbrakk>
      \<Longrightarrow> \<exists>z. z \<in> S \<and> winding_number \<gamma> z = 0"
diff -r 29032b496f2e -r c6b50597abbc src/HOL/Library/Landau_Symbols.thy
--- a/src/HOL/Library/Landau_Symbols.thy	Thu Feb 16 10:42:39 2023 +0000
+++ b/src/HOL/Library/Landau_Symbols.thy	Thu Feb 16 12:21:21 2023 +0000
@@ -1742,6 +1742,10 @@
     by (rule Lim_transform_eventually)
 qed (simp_all add: asymp_equiv_def)
 
+lemma tendsto_imp_asymp_equiv_const:
+  assumes "(f \<longlongrightarrow> c) F" "c \<noteq> 0"
+  shows   "f \<sim>[F] (\<lambda>_. c)"
+  by (rule asymp_equivI' tendsto_eq_intros assms refl)+ (use assms in auto)
 
 lemma asymp_equiv_cong:
   assumes "eventually (\<lambda>x. f1 x = f2 x) F" "eventually (\<lambda>x. g1 x = g2 x) F"