src/HOL/Library/Extended_Real.thy
author wenzelm
Thu Mar 22 16:44:19 2012 +0100 (2012-03-22)
changeset 47082 737d7bc8e50f
parent 45934 9321cd2572fe
child 47108 2a1953f0d20d
permissions -rw-r--r--
tuned proofs;
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(*  Title:      HOL/Library/Extended_Real.thy
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    Author:     Johannes Hölzl, TU München
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    Author:     Robert Himmelmann, TU München
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    Author:     Armin Heller, TU München
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    Author:     Bogdan Grechuk, University of Edinburgh
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*)
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header {* Extended real number line *}
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theory Extended_Real
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imports Complex_Main Extended_Nat
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begin
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text {*
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For more lemmas about the extended real numbers go to
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  @{file "~~/src/HOL/Multivariate_Analysis/Extended_Real_Limits.thy"}
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*}
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lemma (in complete_lattice) atLeast_eq_UNIV_iff: "{x..} = UNIV \<longleftrightarrow> x = bot"
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proof
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  assume "{x..} = UNIV"
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  show "x = bot"
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  proof (rule ccontr)
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    assume "x \<noteq> bot" then have "bot \<notin> {x..}" by (simp add: le_less)
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    then show False using `{x..} = UNIV` by simp
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  qed
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qed auto
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lemma SUPR_pair:
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  "(SUP i : A. SUP j : B. f i j) = (SUP p : A \<times> B. f (fst p) (snd p))"
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  by (rule antisym) (auto intro!: SUP_least SUP_upper2)
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lemma INFI_pair:
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  "(INF i : A. INF j : B. f i j) = (INF p : A \<times> B. f (fst p) (snd p))"
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  by (rule antisym) (auto intro!: INF_greatest INF_lower2)
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subsection {* Definition and basic properties *}
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datatype ereal = ereal real | PInfty | MInfty
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instantiation ereal :: uminus
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begin
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  fun uminus_ereal where
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    "- (ereal r) = ereal (- r)"
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  | "- PInfty = MInfty"
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  | "- MInfty = PInfty"
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  instance ..
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end
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instantiation ereal :: infinity
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begin
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  definition "(\<infinity>::ereal) = PInfty"
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  instance ..
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end
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declare [[coercion "ereal :: real \<Rightarrow> ereal"]]
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lemma ereal_uminus_uminus[simp]:
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  fixes a :: ereal shows "- (- a) = a"
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  by (cases a) simp_all
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lemma
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  shows PInfty_eq_infinity[simp]: "PInfty = \<infinity>"
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    and MInfty_eq_minfinity[simp]: "MInfty = - \<infinity>"
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    and MInfty_neq_PInfty[simp]: "\<infinity> \<noteq> - (\<infinity>::ereal)" "- \<infinity> \<noteq> (\<infinity>::ereal)"
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    and MInfty_neq_ereal[simp]: "ereal r \<noteq> - \<infinity>" "- \<infinity> \<noteq> ereal r"
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    and PInfty_neq_ereal[simp]: "ereal r \<noteq> \<infinity>" "\<infinity> \<noteq> ereal r"
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    and PInfty_cases[simp]: "(case \<infinity> of ereal r \<Rightarrow> f r | PInfty \<Rightarrow> y | MInfty \<Rightarrow> z) = y"
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    and MInfty_cases[simp]: "(case - \<infinity> of ereal r \<Rightarrow> f r | PInfty \<Rightarrow> y | MInfty \<Rightarrow> z) = z"
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  by (simp_all add: infinity_ereal_def)
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declare
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  PInfty_eq_infinity[code_post]
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  MInfty_eq_minfinity[code_post]
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lemma [code_unfold]:
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  "\<infinity> = PInfty"
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  "-PInfty = MInfty"
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  by simp_all
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lemma inj_ereal[simp]: "inj_on ereal A"
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  unfolding inj_on_def by auto
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lemma ereal_cases[case_names real PInf MInf, cases type: ereal]:
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  assumes "\<And>r. x = ereal r \<Longrightarrow> P"
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  assumes "x = \<infinity> \<Longrightarrow> P"
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  assumes "x = -\<infinity> \<Longrightarrow> P"
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  shows P
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  using assms by (cases x) auto
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lemmas ereal2_cases = ereal_cases[case_product ereal_cases]
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lemmas ereal3_cases = ereal2_cases[case_product ereal_cases]
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lemma ereal_uminus_eq_iff[simp]:
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  fixes a b :: ereal shows "-a = -b \<longleftrightarrow> a = b"
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  by (cases rule: ereal2_cases[of a b]) simp_all
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function of_ereal :: "ereal \<Rightarrow> real" where
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"of_ereal (ereal r) = r" |
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"of_ereal \<infinity> = 0" |
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"of_ereal (-\<infinity>) = 0"
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  by (auto intro: ereal_cases)
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termination proof qed (rule wf_empty)
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defs (overloaded)
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  real_of_ereal_def [code_unfold]: "real \<equiv> of_ereal"
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lemma real_of_ereal[simp]:
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    "real (- x :: ereal) = - (real x)"
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    "real (ereal r) = r"
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    "real (\<infinity>::ereal) = 0"
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  by (cases x) (simp_all add: real_of_ereal_def)
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lemma range_ereal[simp]: "range ereal = UNIV - {\<infinity>, -\<infinity>}"
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proof safe
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  fix x assume "x \<notin> range ereal" "x \<noteq> \<infinity>"
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  then show "x = -\<infinity>" by (cases x) auto
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qed auto
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lemma ereal_range_uminus[simp]: "range uminus = (UNIV::ereal set)"
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proof safe
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  fix x :: ereal show "x \<in> range uminus" by (intro image_eqI[of _ _ "-x"]) auto
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qed auto
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instantiation ereal :: number
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begin
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definition [simp]: "number_of x = ereal (number_of x)"
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instance ..
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end
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instantiation ereal :: abs
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begin
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  function abs_ereal where
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    "\<bar>ereal r\<bar> = ereal \<bar>r\<bar>"
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  | "\<bar>-\<infinity>\<bar> = (\<infinity>::ereal)"
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  | "\<bar>\<infinity>\<bar> = (\<infinity>::ereal)"
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  by (auto intro: ereal_cases)
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  termination proof qed (rule wf_empty)
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  instance ..
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end
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lemma abs_eq_infinity_cases[elim!]: "\<lbrakk> \<bar>x :: ereal\<bar> = \<infinity> ; x = \<infinity> \<Longrightarrow> P ; x = -\<infinity> \<Longrightarrow> P \<rbrakk> \<Longrightarrow> P"
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  by (cases x) auto
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lemma abs_neq_infinity_cases[elim!]: "\<lbrakk> \<bar>x :: ereal\<bar> \<noteq> \<infinity> ; \<And>r. x = ereal r \<Longrightarrow> P \<rbrakk> \<Longrightarrow> P"
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  by (cases x) auto
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lemma abs_ereal_uminus[simp]: "\<bar>- x\<bar> = \<bar>x::ereal\<bar>"
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  by (cases x) auto
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subsubsection "Addition"
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instantiation ereal :: comm_monoid_add
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begin
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definition "0 = ereal 0"
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function plus_ereal where
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"ereal r + ereal p = ereal (r + p)" |
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"\<infinity> + a = (\<infinity>::ereal)" |
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"a + \<infinity> = (\<infinity>::ereal)" |
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"ereal r + -\<infinity> = - \<infinity>" |
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"-\<infinity> + ereal p = -(\<infinity>::ereal)" |
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"-\<infinity> + -\<infinity> = -(\<infinity>::ereal)"
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proof -
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  case (goal1 P x)
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  moreover then obtain a b where "x = (a, b)" by (cases x) auto
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  ultimately show P
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   by (cases rule: ereal2_cases[of a b]) auto
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qed auto
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termination proof qed (rule wf_empty)
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lemma Infty_neq_0[simp]:
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  "(\<infinity>::ereal) \<noteq> 0" "0 \<noteq> (\<infinity>::ereal)"
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  "-(\<infinity>::ereal) \<noteq> 0" "0 \<noteq> -(\<infinity>::ereal)"
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  by (simp_all add: zero_ereal_def)
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lemma ereal_eq_0[simp]:
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  "ereal r = 0 \<longleftrightarrow> r = 0"
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  "0 = ereal r \<longleftrightarrow> r = 0"
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  unfolding zero_ereal_def by simp_all
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instance
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proof
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  fix a b c :: ereal
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  show "0 + a = a"
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    by (cases a) (simp_all add: zero_ereal_def)
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  show "a + b = b + a"
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    by (cases rule: ereal2_cases[of a b]) simp_all
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  show "a + b + c = a + (b + c)"
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    by (cases rule: ereal3_cases[of a b c]) simp_all
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qed
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end
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lemma real_of_ereal_0[simp]: "real (0::ereal) = 0"
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  unfolding real_of_ereal_def zero_ereal_def by simp
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lemma abs_ereal_zero[simp]: "\<bar>0\<bar> = (0::ereal)"
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  unfolding zero_ereal_def abs_ereal.simps by simp
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lemma ereal_uminus_zero[simp]:
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  "- 0 = (0::ereal)"
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  by (simp add: zero_ereal_def)
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lemma ereal_uminus_zero_iff[simp]:
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  fixes a :: ereal shows "-a = 0 \<longleftrightarrow> a = 0"
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  by (cases a) simp_all
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lemma ereal_plus_eq_PInfty[simp]:
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  fixes a b :: ereal shows "a + b = \<infinity> \<longleftrightarrow> a = \<infinity> \<or> b = \<infinity>"
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  by (cases rule: ereal2_cases[of a b]) auto
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lemma ereal_plus_eq_MInfty[simp]:
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  fixes a b :: ereal shows "a + b = -\<infinity> \<longleftrightarrow>
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    (a = -\<infinity> \<or> b = -\<infinity>) \<and> a \<noteq> \<infinity> \<and> b \<noteq> \<infinity>"
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  by (cases rule: ereal2_cases[of a b]) auto
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lemma ereal_add_cancel_left:
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  fixes a b :: ereal assumes "a \<noteq> -\<infinity>"
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  shows "a + b = a + c \<longleftrightarrow> (a = \<infinity> \<or> b = c)"
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  using assms by (cases rule: ereal3_cases[of a b c]) auto
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lemma ereal_add_cancel_right:
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  fixes a b :: ereal assumes "a \<noteq> -\<infinity>"
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  shows "b + a = c + a \<longleftrightarrow> (a = \<infinity> \<or> b = c)"
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  using assms by (cases rule: ereal3_cases[of a b c]) auto
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lemma ereal_real:
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  "ereal (real x) = (if \<bar>x\<bar> = \<infinity> then 0 else x)"
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  by (cases x) simp_all
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lemma real_of_ereal_add:
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  fixes a b :: ereal
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  shows "real (a + b) =
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    (if (\<bar>a\<bar> = \<infinity>) \<and> (\<bar>b\<bar> = \<infinity>) \<or> (\<bar>a\<bar> \<noteq> \<infinity>) \<and> (\<bar>b\<bar> \<noteq> \<infinity>) then real a + real b else 0)"
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  by (cases rule: ereal2_cases[of a b]) auto
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subsubsection "Linear order on @{typ ereal}"
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instantiation ereal :: linorder
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begin
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function less_ereal
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where
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  "   ereal x < ereal y     \<longleftrightarrow> x < y"
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| "(\<infinity>::ereal) < a           \<longleftrightarrow> False"
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| "         a < -(\<infinity>::ereal) \<longleftrightarrow> False"
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| "ereal x    < \<infinity>           \<longleftrightarrow> True"
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| "        -\<infinity> < ereal r     \<longleftrightarrow> True"
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| "        -\<infinity> < (\<infinity>::ereal) \<longleftrightarrow> True"
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proof -
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  case (goal1 P x)
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  moreover then obtain a b where "x = (a,b)" by (cases x) auto
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  ultimately show P by (cases rule: ereal2_cases[of a b]) auto
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qed simp_all
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termination by (relation "{}") simp
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definition "x \<le> (y::ereal) \<longleftrightarrow> x < y \<or> x = y"
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lemma ereal_infty_less[simp]:
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  fixes x :: ereal
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  shows "x < \<infinity> \<longleftrightarrow> (x \<noteq> \<infinity>)"
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    "-\<infinity> < x \<longleftrightarrow> (x \<noteq> -\<infinity>)"
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  by (cases x, simp_all) (cases x, simp_all)
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lemma ereal_infty_less_eq[simp]:
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  fixes x :: ereal
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  shows "\<infinity> \<le> x \<longleftrightarrow> x = \<infinity>"
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  "x \<le> -\<infinity> \<longleftrightarrow> x = -\<infinity>"
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  by (auto simp add: less_eq_ereal_def)
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lemma ereal_less[simp]:
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  "ereal r < 0 \<longleftrightarrow> (r < 0)"
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  "0 < ereal r \<longleftrightarrow> (0 < r)"
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  "0 < (\<infinity>::ereal)"
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  "-(\<infinity>::ereal) < 0"
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  by (simp_all add: zero_ereal_def)
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lemma ereal_less_eq[simp]:
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  "x \<le> (\<infinity>::ereal)"
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  "-(\<infinity>::ereal) \<le> x"
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  "ereal r \<le> ereal p \<longleftrightarrow> r \<le> p"
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  "ereal r \<le> 0 \<longleftrightarrow> r \<le> 0"
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  "0 \<le> ereal r \<longleftrightarrow> 0 \<le> r"
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  by (auto simp add: less_eq_ereal_def zero_ereal_def)
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lemma ereal_infty_less_eq2:
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  "a \<le> b \<Longrightarrow> a = \<infinity> \<Longrightarrow> b = (\<infinity>::ereal)"
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  "a \<le> b \<Longrightarrow> b = -\<infinity> \<Longrightarrow> a = -(\<infinity>::ereal)"
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  by simp_all
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instance
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proof
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  fix x y z :: ereal
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  show "x \<le> x"
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    by (cases x) simp_all
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  show "x < y \<longleftrightarrow> x \<le> y \<and> \<not> y \<le> x"
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    by (cases rule: ereal2_cases[of x y]) auto
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  show "x \<le> y \<or> y \<le> x "
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    by (cases rule: ereal2_cases[of x y]) auto
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  { assume "x \<le> y" "y \<le> x" then show "x = y"
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    by (cases rule: ereal2_cases[of x y]) auto }
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  { assume "x \<le> y" "y \<le> z" then show "x \<le> z"
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   306
    by (cases rule: ereal3_cases[of x y z]) auto }
hoelzl@41973
   307
qed
wenzelm@47082
   308
hoelzl@41973
   309
end
hoelzl@41973
   310
hoelzl@43920
   311
instance ereal :: ordered_ab_semigroup_add
hoelzl@41978
   312
proof
hoelzl@43920
   313
  fix a b c :: ereal assume "a \<le> b" then show "c + a \<le> c + b"
hoelzl@43920
   314
    by (cases rule: ereal3_cases[of a b c]) auto
hoelzl@41978
   315
qed
hoelzl@41978
   316
hoelzl@43920
   317
lemma real_of_ereal_positive_mono:
hoelzl@43923
   318
  fixes x y :: ereal shows "\<lbrakk>0 \<le> x; x \<le> y; y \<noteq> \<infinity>\<rbrakk> \<Longrightarrow> real x \<le> real y"
hoelzl@43920
   319
  by (cases rule: ereal2_cases[of x y]) auto
hoelzl@42950
   320
hoelzl@43920
   321
lemma ereal_MInfty_lessI[intro, simp]:
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   322
  fixes a :: ereal shows "a \<noteq> -\<infinity> \<Longrightarrow> -\<infinity> < a"
hoelzl@41973
   323
  by (cases a) auto
hoelzl@41973
   324
hoelzl@43920
   325
lemma ereal_less_PInfty[intro, simp]:
hoelzl@43923
   326
  fixes a :: ereal shows "a \<noteq> \<infinity> \<Longrightarrow> a < \<infinity>"
hoelzl@41973
   327
  by (cases a) auto
hoelzl@41973
   328
hoelzl@43920
   329
lemma ereal_less_ereal_Ex:
hoelzl@43920
   330
  fixes a b :: ereal
hoelzl@43920
   331
  shows "x < ereal r \<longleftrightarrow> x = -\<infinity> \<or> (\<exists>p. p < r \<and> x = ereal p)"
hoelzl@41973
   332
  by (cases x) auto
hoelzl@41973
   333
hoelzl@43920
   334
lemma less_PInf_Ex_of_nat: "x \<noteq> \<infinity> \<longleftrightarrow> (\<exists>n::nat. x < ereal (real n))"
hoelzl@41979
   335
proof (cases x)
hoelzl@41979
   336
  case (real r) then show ?thesis
hoelzl@41980
   337
    using reals_Archimedean2[of r] by simp
hoelzl@41979
   338
qed simp_all
hoelzl@41979
   339
hoelzl@43920
   340
lemma ereal_add_mono:
hoelzl@43920
   341
  fixes a b c d :: ereal assumes "a \<le> b" "c \<le> d" shows "a + c \<le> b + d"
hoelzl@41973
   342
  using assms
hoelzl@41973
   343
  apply (cases a)
hoelzl@43920
   344
  apply (cases rule: ereal3_cases[of b c d], auto)
hoelzl@43920
   345
  apply (cases rule: ereal3_cases[of b c d], auto)
hoelzl@41973
   346
  done
hoelzl@41973
   347
hoelzl@43920
   348
lemma ereal_minus_le_minus[simp]:
hoelzl@43920
   349
  fixes a b :: ereal shows "- a \<le> - b \<longleftrightarrow> b \<le> a"
hoelzl@43920
   350
  by (cases rule: ereal2_cases[of a b]) auto
hoelzl@41973
   351
hoelzl@43920
   352
lemma ereal_minus_less_minus[simp]:
hoelzl@43920
   353
  fixes a b :: ereal shows "- a < - b \<longleftrightarrow> b < a"
hoelzl@43920
   354
  by (cases rule: ereal2_cases[of a b]) auto
hoelzl@41973
   355
hoelzl@43920
   356
lemma ereal_le_real_iff:
hoelzl@43920
   357
  "x \<le> real y \<longleftrightarrow> ((\<bar>y\<bar> \<noteq> \<infinity> \<longrightarrow> ereal x \<le> y) \<and> (\<bar>y\<bar> = \<infinity> \<longrightarrow> x \<le> 0))"
hoelzl@41973
   358
  by (cases y) auto
hoelzl@41973
   359
hoelzl@43920
   360
lemma real_le_ereal_iff:
hoelzl@43920
   361
  "real y \<le> x \<longleftrightarrow> ((\<bar>y\<bar> \<noteq> \<infinity> \<longrightarrow> y \<le> ereal x) \<and> (\<bar>y\<bar> = \<infinity> \<longrightarrow> 0 \<le> x))"
hoelzl@41973
   362
  by (cases y) auto
hoelzl@41973
   363
hoelzl@43920
   364
lemma ereal_less_real_iff:
hoelzl@43920
   365
  "x < real y \<longleftrightarrow> ((\<bar>y\<bar> \<noteq> \<infinity> \<longrightarrow> ereal x < y) \<and> (\<bar>y\<bar> = \<infinity> \<longrightarrow> x < 0))"
hoelzl@41973
   366
  by (cases y) auto
hoelzl@41973
   367
hoelzl@43920
   368
lemma real_less_ereal_iff:
hoelzl@43920
   369
  "real y < x \<longleftrightarrow> ((\<bar>y\<bar> \<noteq> \<infinity> \<longrightarrow> y < ereal x) \<and> (\<bar>y\<bar> = \<infinity> \<longrightarrow> 0 < x))"
hoelzl@41973
   370
  by (cases y) auto
hoelzl@41973
   371
hoelzl@43920
   372
lemma real_of_ereal_pos:
hoelzl@43920
   373
  fixes x :: ereal shows "0 \<le> x \<Longrightarrow> 0 \<le> real x" by (cases x) auto
hoelzl@41979
   374
hoelzl@43920
   375
lemmas real_of_ereal_ord_simps =
hoelzl@43920
   376
  ereal_le_real_iff real_le_ereal_iff ereal_less_real_iff real_less_ereal_iff
hoelzl@41973
   377
hoelzl@43920
   378
lemma abs_ereal_ge0[simp]: "0 \<le> x \<Longrightarrow> \<bar>x :: ereal\<bar> = x"
hoelzl@42950
   379
  by (cases x) auto
hoelzl@42950
   380
hoelzl@43920
   381
lemma abs_ereal_less0[simp]: "x < 0 \<Longrightarrow> \<bar>x :: ereal\<bar> = -x"
hoelzl@42950
   382
  by (cases x) auto
hoelzl@42950
   383
hoelzl@43920
   384
lemma abs_ereal_pos[simp]: "0 \<le> \<bar>x :: ereal\<bar>"
hoelzl@42950
   385
  by (cases x) auto
hoelzl@42950
   386
hoelzl@43923
   387
lemma real_of_ereal_le_0[simp]: "real (x :: ereal) \<le> 0 \<longleftrightarrow> (x \<le> 0 \<or> x = \<infinity>)"
hoelzl@43923
   388
  by (cases x) auto
hoelzl@42950
   389
hoelzl@43923
   390
lemma abs_real_of_ereal[simp]: "\<bar>real (x :: ereal)\<bar> = real \<bar>x\<bar>"
hoelzl@43923
   391
  by (cases x) auto
hoelzl@42950
   392
hoelzl@43923
   393
lemma zero_less_real_of_ereal:
hoelzl@43923
   394
  fixes x :: ereal shows "0 < real x \<longleftrightarrow> (0 < x \<and> x \<noteq> \<infinity>)"
hoelzl@43923
   395
  by (cases x) auto
hoelzl@42950
   396
hoelzl@43920
   397
lemma ereal_0_le_uminus_iff[simp]:
hoelzl@43920
   398
  fixes a :: ereal shows "0 \<le> -a \<longleftrightarrow> a \<le> 0"
hoelzl@43920
   399
  by (cases rule: ereal2_cases[of a]) auto
hoelzl@42950
   400
hoelzl@43920
   401
lemma ereal_uminus_le_0_iff[simp]:
hoelzl@43920
   402
  fixes a :: ereal shows "-a \<le> 0 \<longleftrightarrow> 0 \<le> a"
hoelzl@43920
   403
  by (cases rule: ereal2_cases[of a]) auto
hoelzl@42950
   404
hoelzl@43923
   405
lemma ereal_dense2: "x < y \<Longrightarrow> \<exists>z. x < ereal z \<and> ereal z < y"
hoelzl@43923
   406
  using lt_ex gt_ex dense by (cases x y rule: ereal2_cases) auto
hoelzl@43923
   407
hoelzl@43920
   408
lemma ereal_dense:
hoelzl@43920
   409
  fixes x y :: ereal assumes "x < y"
hoelzl@43923
   410
  shows "\<exists>z. x < z \<and> z < y"
hoelzl@43923
   411
  using ereal_dense2[OF `x < y`] by blast
hoelzl@41973
   412
hoelzl@43920
   413
lemma ereal_add_strict_mono:
hoelzl@43920
   414
  fixes a b c d :: ereal
hoelzl@41979
   415
  assumes "a = b" "0 \<le> a" "a \<noteq> \<infinity>" "c < d"
hoelzl@41979
   416
  shows "a + c < b + d"
hoelzl@43920
   417
  using assms by (cases rule: ereal3_cases[case_product ereal_cases, of a b c d]) auto
hoelzl@41979
   418
hoelzl@43923
   419
lemma ereal_less_add: 
hoelzl@43923
   420
  fixes a b c :: ereal shows "\<bar>a\<bar> \<noteq> \<infinity> \<Longrightarrow> c < b \<Longrightarrow> a + c < a + b"
hoelzl@43920
   421
  by (cases rule: ereal2_cases[of b c]) auto
hoelzl@41979
   422
hoelzl@43920
   423
lemma ereal_uminus_eq_reorder: "- a = b \<longleftrightarrow> a = (-b::ereal)" by auto
hoelzl@41979
   424
hoelzl@43920
   425
lemma ereal_uminus_less_reorder: "- a < b \<longleftrightarrow> -b < (a::ereal)"
hoelzl@43920
   426
  by (subst (3) ereal_uminus_uminus[symmetric]) (simp only: ereal_minus_less_minus)
hoelzl@41979
   427
hoelzl@43920
   428
lemma ereal_uminus_le_reorder: "- a \<le> b \<longleftrightarrow> -b \<le> (a::ereal)"
hoelzl@43920
   429
  by (subst (3) ereal_uminus_uminus[symmetric]) (simp only: ereal_minus_le_minus)
hoelzl@41979
   430
hoelzl@43920
   431
lemmas ereal_uminus_reorder =
hoelzl@43920
   432
  ereal_uminus_eq_reorder ereal_uminus_less_reorder ereal_uminus_le_reorder
hoelzl@41979
   433
hoelzl@43920
   434
lemma ereal_bot:
hoelzl@43920
   435
  fixes x :: ereal assumes "\<And>B. x \<le> ereal B" shows "x = - \<infinity>"
hoelzl@41979
   436
proof (cases x)
hoelzl@41979
   437
  case (real r) with assms[of "r - 1"] show ?thesis by auto
wenzelm@47082
   438
next
wenzelm@47082
   439
  case PInf with assms[of 0] show ?thesis by auto
wenzelm@47082
   440
next
wenzelm@47082
   441
  case MInf then show ?thesis by simp
hoelzl@41979
   442
qed
hoelzl@41979
   443
hoelzl@43920
   444
lemma ereal_top:
hoelzl@43920
   445
  fixes x :: ereal assumes "\<And>B. x \<ge> ereal B" shows "x = \<infinity>"
hoelzl@41979
   446
proof (cases x)
hoelzl@41979
   447
  case (real r) with assms[of "r + 1"] show ?thesis by auto
wenzelm@47082
   448
next
wenzelm@47082
   449
  case MInf with assms[of 0] show ?thesis by auto
wenzelm@47082
   450
next
wenzelm@47082
   451
  case PInf then show ?thesis by simp
hoelzl@41979
   452
qed
hoelzl@41979
   453
hoelzl@41979
   454
lemma
hoelzl@43920
   455
  shows ereal_max[simp]: "ereal (max x y) = max (ereal x) (ereal y)"
hoelzl@43920
   456
    and ereal_min[simp]: "ereal (min x y) = min (ereal x) (ereal y)"
hoelzl@41979
   457
  by (simp_all add: min_def max_def)
hoelzl@41979
   458
hoelzl@43920
   459
lemma ereal_max_0: "max 0 (ereal r) = ereal (max 0 r)"
hoelzl@43920
   460
  by (auto simp: zero_ereal_def)
hoelzl@41979
   461
hoelzl@41978
   462
lemma
hoelzl@43920
   463
  fixes f :: "nat \<Rightarrow> ereal"
hoelzl@41978
   464
  shows incseq_uminus[simp]: "incseq (\<lambda>x. - f x) \<longleftrightarrow> decseq f"
hoelzl@41978
   465
  and decseq_uminus[simp]: "decseq (\<lambda>x. - f x) \<longleftrightarrow> incseq f"
hoelzl@41978
   466
  unfolding decseq_def incseq_def by auto
hoelzl@41978
   467
hoelzl@43920
   468
lemma incseq_ereal: "incseq f \<Longrightarrow> incseq (\<lambda>x. ereal (f x))"
hoelzl@42950
   469
  unfolding incseq_def by auto
hoelzl@42950
   470
hoelzl@43920
   471
lemma ereal_add_nonneg_nonneg:
hoelzl@43920
   472
  fixes a b :: ereal shows "0 \<le> a \<Longrightarrow> 0 \<le> b \<Longrightarrow> 0 \<le> a + b"
hoelzl@41978
   473
  using add_mono[of 0 a 0 b] by simp
hoelzl@41978
   474
hoelzl@41978
   475
lemma image_eqD: "f ` A = B \<Longrightarrow> (\<forall>x\<in>A. f x \<in> B)"
hoelzl@41978
   476
  by auto
hoelzl@41978
   477
hoelzl@41978
   478
lemma incseq_setsumI:
hoelzl@41979
   479
  fixes f :: "nat \<Rightarrow> 'a::{comm_monoid_add, ordered_ab_semigroup_add}"
hoelzl@41978
   480
  assumes "\<And>i. 0 \<le> f i"
hoelzl@41978
   481
  shows "incseq (\<lambda>i. setsum f {..< i})"
hoelzl@41978
   482
proof (intro incseq_SucI)
hoelzl@41978
   483
  fix n have "setsum f {..< n} + 0 \<le> setsum f {..<n} + f n"
hoelzl@41978
   484
    using assms by (rule add_left_mono)
hoelzl@41978
   485
  then show "setsum f {..< n} \<le> setsum f {..< Suc n}"
hoelzl@41978
   486
    by auto
hoelzl@41978
   487
qed
hoelzl@41978
   488
hoelzl@41979
   489
lemma incseq_setsumI2:
hoelzl@41979
   490
  fixes f :: "'i \<Rightarrow> nat \<Rightarrow> 'a::{comm_monoid_add, ordered_ab_semigroup_add}"
hoelzl@41979
   491
  assumes "\<And>n. n \<in> A \<Longrightarrow> incseq (f n)"
hoelzl@41979
   492
  shows "incseq (\<lambda>i. \<Sum>n\<in>A. f n i)"
hoelzl@41979
   493
  using assms unfolding incseq_def by (auto intro: setsum_mono)
hoelzl@41979
   494
hoelzl@41973
   495
subsubsection "Multiplication"
hoelzl@41973
   496
hoelzl@43920
   497
instantiation ereal :: "{comm_monoid_mult, sgn}"
hoelzl@41973
   498
begin
hoelzl@41973
   499
hoelzl@43920
   500
definition "1 = ereal 1"
hoelzl@41973
   501
hoelzl@43920
   502
function sgn_ereal where
hoelzl@43920
   503
  "sgn (ereal r) = ereal (sgn r)"
hoelzl@43923
   504
| "sgn (\<infinity>::ereal) = 1"
hoelzl@43923
   505
| "sgn (-\<infinity>::ereal) = -1"
hoelzl@43920
   506
by (auto intro: ereal_cases)
hoelzl@41976
   507
termination proof qed (rule wf_empty)
hoelzl@41976
   508
hoelzl@43920
   509
function times_ereal where
hoelzl@43920
   510
"ereal r * ereal p = ereal (r * p)" |
hoelzl@43920
   511
"ereal r * \<infinity> = (if r = 0 then 0 else if r > 0 then \<infinity> else -\<infinity>)" |
hoelzl@43920
   512
"\<infinity> * ereal r = (if r = 0 then 0 else if r > 0 then \<infinity> else -\<infinity>)" |
hoelzl@43920
   513
"ereal r * -\<infinity> = (if r = 0 then 0 else if r > 0 then -\<infinity> else \<infinity>)" |
hoelzl@43920
   514
"-\<infinity> * ereal r = (if r = 0 then 0 else if r > 0 then -\<infinity> else \<infinity>)" |
hoelzl@43923
   515
"(\<infinity>::ereal) * \<infinity> = \<infinity>" |
hoelzl@43923
   516
"-(\<infinity>::ereal) * \<infinity> = -\<infinity>" |
hoelzl@43923
   517
"(\<infinity>::ereal) * -\<infinity> = -\<infinity>" |
hoelzl@43923
   518
"-(\<infinity>::ereal) * -\<infinity> = \<infinity>"
hoelzl@41973
   519
proof -
hoelzl@41973
   520
  case (goal1 P x)
hoelzl@41973
   521
  moreover then obtain a b where "x = (a, b)" by (cases x) auto
hoelzl@43920
   522
  ultimately show P by (cases rule: ereal2_cases[of a b]) auto
hoelzl@41973
   523
qed simp_all
hoelzl@41973
   524
termination by (relation "{}") simp
hoelzl@41973
   525
hoelzl@41973
   526
instance
hoelzl@41973
   527
proof
wenzelm@47082
   528
  fix a b c :: ereal show "1 * a = a"
hoelzl@43920
   529
    by (cases a) (simp_all add: one_ereal_def)
wenzelm@47082
   530
  show "a * b = b * a"
hoelzl@43920
   531
    by (cases rule: ereal2_cases[of a b]) simp_all
wenzelm@47082
   532
  show "a * b * c = a * (b * c)"
hoelzl@43920
   533
    by (cases rule: ereal3_cases[of a b c])
hoelzl@43920
   534
       (simp_all add: zero_ereal_def zero_less_mult_iff)
hoelzl@41973
   535
qed
hoelzl@41973
   536
end
hoelzl@41973
   537
hoelzl@43920
   538
lemma real_of_ereal_le_1:
hoelzl@43920
   539
  fixes a :: ereal shows "a \<le> 1 \<Longrightarrow> real a \<le> 1"
hoelzl@43920
   540
  by (cases a) (auto simp: one_ereal_def)
hoelzl@42950
   541
hoelzl@43920
   542
lemma abs_ereal_one[simp]: "\<bar>1\<bar> = (1::ereal)"
hoelzl@43920
   543
  unfolding one_ereal_def by simp
hoelzl@41976
   544
hoelzl@43920
   545
lemma ereal_mult_zero[simp]:
hoelzl@43920
   546
  fixes a :: ereal shows "a * 0 = 0"
hoelzl@43920
   547
  by (cases a) (simp_all add: zero_ereal_def)
hoelzl@41973
   548
hoelzl@43920
   549
lemma ereal_zero_mult[simp]:
hoelzl@43920
   550
  fixes a :: ereal shows "0 * a = 0"
hoelzl@43920
   551
  by (cases a) (simp_all add: zero_ereal_def)
hoelzl@41973
   552
hoelzl@43920
   553
lemma ereal_m1_less_0[simp]:
hoelzl@43920
   554
  "-(1::ereal) < 0"
hoelzl@43920
   555
  by (simp add: zero_ereal_def one_ereal_def)
hoelzl@41973
   556
hoelzl@43920
   557
lemma ereal_zero_m1[simp]:
hoelzl@43920
   558
  "1 \<noteq> (0::ereal)"
hoelzl@43920
   559
  by (simp add: zero_ereal_def one_ereal_def)
hoelzl@41973
   560
hoelzl@43920
   561
lemma ereal_times_0[simp]:
hoelzl@43920
   562
  fixes x :: ereal shows "0 * x = 0"
hoelzl@43920
   563
  by (cases x) (auto simp: zero_ereal_def)
hoelzl@41973
   564
hoelzl@43920
   565
lemma ereal_times[simp]:
hoelzl@43923
   566
  "1 \<noteq> (\<infinity>::ereal)" "(\<infinity>::ereal) \<noteq> 1"
hoelzl@43923
   567
  "1 \<noteq> -(\<infinity>::ereal)" "-(\<infinity>::ereal) \<noteq> 1"
hoelzl@43920
   568
  by (auto simp add: times_ereal_def one_ereal_def)
hoelzl@41973
   569
hoelzl@43920
   570
lemma ereal_plus_1[simp]:
hoelzl@43920
   571
  "1 + ereal r = ereal (r + 1)" "ereal r + 1 = ereal (r + 1)"
hoelzl@43923
   572
  "1 + -(\<infinity>::ereal) = -\<infinity>" "-(\<infinity>::ereal) + 1 = -\<infinity>"
hoelzl@43920
   573
  unfolding one_ereal_def by auto
hoelzl@41973
   574
hoelzl@43920
   575
lemma ereal_zero_times[simp]:
hoelzl@43920
   576
  fixes a b :: ereal shows "a * b = 0 \<longleftrightarrow> a = 0 \<or> b = 0"
hoelzl@43920
   577
  by (cases rule: ereal2_cases[of a b]) auto
hoelzl@41973
   578
hoelzl@43920
   579
lemma ereal_mult_eq_PInfty[simp]:
hoelzl@43923
   580
  shows "a * b = (\<infinity>::ereal) \<longleftrightarrow>
hoelzl@41973
   581
    (a = \<infinity> \<and> b > 0) \<or> (a > 0 \<and> b = \<infinity>) \<or> (a = -\<infinity> \<and> b < 0) \<or> (a < 0 \<and> b = -\<infinity>)"
hoelzl@43920
   582
  by (cases rule: ereal2_cases[of a b]) auto
hoelzl@41973
   583
hoelzl@43920
   584
lemma ereal_mult_eq_MInfty[simp]:
hoelzl@43923
   585
  shows "a * b = -(\<infinity>::ereal) \<longleftrightarrow>
hoelzl@41973
   586
    (a = \<infinity> \<and> b < 0) \<or> (a < 0 \<and> b = \<infinity>) \<or> (a = -\<infinity> \<and> b > 0) \<or> (a > 0 \<and> b = -\<infinity>)"
hoelzl@43920
   587
  by (cases rule: ereal2_cases[of a b]) auto
hoelzl@41973
   588
hoelzl@43920
   589
lemma ereal_0_less_1[simp]: "0 < (1::ereal)"
hoelzl@43920
   590
  by (simp_all add: zero_ereal_def one_ereal_def)
hoelzl@41973
   591
hoelzl@43920
   592
lemma ereal_zero_one[simp]: "0 \<noteq> (1::ereal)"
hoelzl@43920
   593
  by (simp_all add: zero_ereal_def one_ereal_def)
hoelzl@41973
   594
hoelzl@43920
   595
lemma ereal_mult_minus_left[simp]:
hoelzl@43920
   596
  fixes a b :: ereal shows "-a * b = - (a * b)"
hoelzl@43920
   597
  by (cases rule: ereal2_cases[of a b]) auto
hoelzl@41973
   598
hoelzl@43920
   599
lemma ereal_mult_minus_right[simp]:
hoelzl@43920
   600
  fixes a b :: ereal shows "a * -b = - (a * b)"
hoelzl@43920
   601
  by (cases rule: ereal2_cases[of a b]) auto
hoelzl@41973
   602
hoelzl@43920
   603
lemma ereal_mult_infty[simp]:
hoelzl@43923
   604
  "a * (\<infinity>::ereal) = (if a = 0 then 0 else if 0 < a then \<infinity> else - \<infinity>)"
hoelzl@41973
   605
  by (cases a) auto
hoelzl@41973
   606
hoelzl@43920
   607
lemma ereal_infty_mult[simp]:
hoelzl@43923
   608
  "(\<infinity>::ereal) * a = (if a = 0 then 0 else if 0 < a then \<infinity> else - \<infinity>)"
hoelzl@41973
   609
  by (cases a) auto
hoelzl@41973
   610
hoelzl@43920
   611
lemma ereal_mult_strict_right_mono:
hoelzl@43923
   612
  assumes "a < b" and "0 < c" "c < (\<infinity>::ereal)"
hoelzl@41973
   613
  shows "a * c < b * c"
hoelzl@41973
   614
  using assms
hoelzl@43920
   615
  by (cases rule: ereal3_cases[of a b c])
huffman@44142
   616
     (auto simp: zero_le_mult_iff)
hoelzl@41973
   617
hoelzl@43920
   618
lemma ereal_mult_strict_left_mono:
hoelzl@43923
   619
  "\<lbrakk> a < b ; 0 < c ; c < (\<infinity>::ereal)\<rbrakk> \<Longrightarrow> c * a < c * b"
hoelzl@43920
   620
  using ereal_mult_strict_right_mono by (simp add: mult_commute[of c])
hoelzl@41973
   621
hoelzl@43920
   622
lemma ereal_mult_right_mono:
hoelzl@43920
   623
  fixes a b c :: ereal shows "\<lbrakk>a \<le> b; 0 \<le> c\<rbrakk> \<Longrightarrow> a*c \<le> b*c"
hoelzl@41973
   624
  using assms
hoelzl@41973
   625
  apply (cases "c = 0") apply simp
hoelzl@43920
   626
  by (cases rule: ereal3_cases[of a b c])
huffman@44142
   627
     (auto simp: zero_le_mult_iff)
hoelzl@41973
   628
hoelzl@43920
   629
lemma ereal_mult_left_mono:
hoelzl@43920
   630
  fixes a b c :: ereal shows "\<lbrakk>a \<le> b; 0 \<le> c\<rbrakk> \<Longrightarrow> c * a \<le> c * b"
hoelzl@43920
   631
  using ereal_mult_right_mono by (simp add: mult_commute[of c])
hoelzl@41973
   632
hoelzl@43920
   633
lemma zero_less_one_ereal[simp]: "0 \<le> (1::ereal)"
hoelzl@43920
   634
  by (simp add: one_ereal_def zero_ereal_def)
hoelzl@41978
   635
hoelzl@43920
   636
lemma ereal_0_le_mult[simp]: "0 \<le> a \<Longrightarrow> 0 \<le> b \<Longrightarrow> 0 \<le> a * (b :: ereal)"
hoelzl@43920
   637
  by (cases rule: ereal2_cases[of a b]) (auto simp: mult_nonneg_nonneg)
hoelzl@41979
   638
hoelzl@43920
   639
lemma ereal_right_distrib:
hoelzl@43920
   640
  fixes r a b :: ereal shows "0 \<le> a \<Longrightarrow> 0 \<le> b \<Longrightarrow> r * (a + b) = r * a + r * b"
hoelzl@43920
   641
  by (cases rule: ereal3_cases[of r a b]) (simp_all add: field_simps)
hoelzl@41979
   642
hoelzl@43920
   643
lemma ereal_left_distrib:
hoelzl@43920
   644
  fixes r a b :: ereal shows "0 \<le> a \<Longrightarrow> 0 \<le> b \<Longrightarrow> (a + b) * r = a * r + b * r"
hoelzl@43920
   645
  by (cases rule: ereal3_cases[of r a b]) (simp_all add: field_simps)
hoelzl@41979
   646
hoelzl@43920
   647
lemma ereal_mult_le_0_iff:
hoelzl@43920
   648
  fixes a b :: ereal
hoelzl@41979
   649
  shows "a * b \<le> 0 \<longleftrightarrow> (0 \<le> a \<and> b \<le> 0) \<or> (a \<le> 0 \<and> 0 \<le> b)"
hoelzl@43920
   650
  by (cases rule: ereal2_cases[of a b]) (simp_all add: mult_le_0_iff)
hoelzl@41979
   651
hoelzl@43920
   652
lemma ereal_zero_le_0_iff:
hoelzl@43920
   653
  fixes a b :: ereal
hoelzl@41979
   654
  shows "0 \<le> a * b \<longleftrightarrow> (0 \<le> a \<and> 0 \<le> b) \<or> (a \<le> 0 \<and> b \<le> 0)"
hoelzl@43920
   655
  by (cases rule: ereal2_cases[of a b]) (simp_all add: zero_le_mult_iff)
hoelzl@41979
   656
hoelzl@43920
   657
lemma ereal_mult_less_0_iff:
hoelzl@43920
   658
  fixes a b :: ereal
hoelzl@41979
   659
  shows "a * b < 0 \<longleftrightarrow> (0 < a \<and> b < 0) \<or> (a < 0 \<and> 0 < b)"
hoelzl@43920
   660
  by (cases rule: ereal2_cases[of a b]) (simp_all add: mult_less_0_iff)
hoelzl@41979
   661
hoelzl@43920
   662
lemma ereal_zero_less_0_iff:
hoelzl@43920
   663
  fixes a b :: ereal
hoelzl@41979
   664
  shows "0 < a * b \<longleftrightarrow> (0 < a \<and> 0 < b) \<or> (a < 0 \<and> b < 0)"
hoelzl@43920
   665
  by (cases rule: ereal2_cases[of a b]) (simp_all add: zero_less_mult_iff)
hoelzl@41979
   666
hoelzl@43920
   667
lemma ereal_distrib:
hoelzl@43920
   668
  fixes a b c :: ereal
hoelzl@41979
   669
  assumes "a \<noteq> \<infinity> \<or> b \<noteq> -\<infinity>" "a \<noteq> -\<infinity> \<or> b \<noteq> \<infinity>" "\<bar>c\<bar> \<noteq> \<infinity>"
hoelzl@41979
   670
  shows "(a + b) * c = a * c + b * c"
hoelzl@41979
   671
  using assms
hoelzl@43920
   672
  by (cases rule: ereal3_cases[of a b c]) (simp_all add: field_simps)
hoelzl@41979
   673
hoelzl@43920
   674
lemma ereal_le_epsilon:
hoelzl@43920
   675
  fixes x y :: ereal
hoelzl@41979
   676
  assumes "ALL e. 0 < e --> x <= y + e"
hoelzl@41979
   677
  shows "x <= y"
hoelzl@41979
   678
proof-
hoelzl@43920
   679
{ assume a: "EX r. y = ereal r"
wenzelm@47082
   680
  then obtain r where r_def: "y = ereal r" by auto
hoelzl@41979
   681
  { assume "x=(-\<infinity>)" hence ?thesis by auto }
hoelzl@41979
   682
  moreover
hoelzl@41979
   683
  { assume "~(x=(-\<infinity>))"
wenzelm@47082
   684
    then obtain p where p_def: "x = ereal p"
hoelzl@41979
   685
    using a assms[rule_format, of 1] by (cases x) auto
hoelzl@41979
   686
    { fix e have "0 < e --> p <= r + e"
hoelzl@43920
   687
      using assms[rule_format, of "ereal e"] p_def r_def by auto }
hoelzl@41979
   688
    hence "p <= r" apply (subst field_le_epsilon) by auto
hoelzl@41979
   689
    hence ?thesis using r_def p_def by auto
hoelzl@41979
   690
  } ultimately have ?thesis by blast
hoelzl@41979
   691
}
hoelzl@41979
   692
moreover
hoelzl@41979
   693
{ assume "y=(-\<infinity>) | y=\<infinity>" hence ?thesis
hoelzl@41979
   694
    using assms[rule_format, of 1] by (cases x) auto
hoelzl@41979
   695
} ultimately show ?thesis by (cases y) auto
hoelzl@41979
   696
qed
hoelzl@41979
   697
hoelzl@41979
   698
hoelzl@43920
   699
lemma ereal_le_epsilon2:
hoelzl@43920
   700
  fixes x y :: ereal
hoelzl@43920
   701
  assumes "ALL e. 0 < e --> x <= y + ereal e"
hoelzl@41979
   702
  shows "x <= y"
hoelzl@41979
   703
proof-
hoelzl@43920
   704
{ fix e :: ereal assume "e>0"
hoelzl@41979
   705
  { assume "e=\<infinity>" hence "x<=y+e" by auto }
hoelzl@41979
   706
  moreover
hoelzl@41979
   707
  { assume "e~=\<infinity>"
wenzelm@47082
   708
    then obtain r where "e = ereal r" using `e>0` apply (cases e) by auto
hoelzl@41979
   709
    hence "x<=y+e" using assms[rule_format, of r] `e>0` by auto
hoelzl@41979
   710
  } ultimately have "x<=y+e" by blast
wenzelm@47082
   711
} then show ?thesis using ereal_le_epsilon by auto
hoelzl@41979
   712
qed
hoelzl@41979
   713
hoelzl@43920
   714
lemma ereal_le_real:
hoelzl@43920
   715
  fixes x y :: ereal
hoelzl@43920
   716
  assumes "ALL z. x <= ereal z --> y <= ereal z"
hoelzl@41979
   717
  shows "y <= x"
huffman@44142
   718
by (metis assms ereal_bot ereal_cases ereal_infty_less_eq(2) ereal_less_eq(1) linorder_le_cases)
hoelzl@41979
   719
hoelzl@43920
   720
lemma ereal_le_ereal:
hoelzl@43920
   721
  fixes x y :: ereal
hoelzl@41979
   722
  assumes "\<And>B. B < x \<Longrightarrow> B <= y"
hoelzl@41979
   723
  shows "x <= y"
hoelzl@43920
   724
by (metis assms ereal_dense leD linorder_le_less_linear)
hoelzl@41979
   725
hoelzl@43920
   726
lemma ereal_ge_ereal:
hoelzl@43920
   727
  fixes x y :: ereal
hoelzl@41979
   728
  assumes "ALL B. B>x --> B >= y"
hoelzl@41979
   729
  shows "x >= y"
hoelzl@43920
   730
by (metis assms ereal_dense leD linorder_le_less_linear)
hoelzl@41978
   731
hoelzl@43920
   732
lemma setprod_ereal_0:
hoelzl@43920
   733
  fixes f :: "'a \<Rightarrow> ereal"
hoelzl@42950
   734
  shows "(\<Prod>i\<in>A. f i) = 0 \<longleftrightarrow> (finite A \<and> (\<exists>i\<in>A. f i = 0))"
hoelzl@42950
   735
proof cases
hoelzl@42950
   736
  assume "finite A"
hoelzl@42950
   737
  then show ?thesis by (induct A) auto
hoelzl@42950
   738
qed auto
hoelzl@42950
   739
hoelzl@43920
   740
lemma setprod_ereal_pos:
hoelzl@43920
   741
  fixes f :: "'a \<Rightarrow> ereal" assumes pos: "\<And>i. i \<in> I \<Longrightarrow> 0 \<le> f i" shows "0 \<le> (\<Prod>i\<in>I. f i)"
hoelzl@42950
   742
proof cases
hoelzl@42950
   743
  assume "finite I" from this pos show ?thesis by induct auto
hoelzl@42950
   744
qed simp
hoelzl@42950
   745
hoelzl@42950
   746
lemma setprod_PInf:
hoelzl@43923
   747
  fixes f :: "'a \<Rightarrow> ereal"
hoelzl@42950
   748
  assumes "\<And>i. i \<in> I \<Longrightarrow> 0 \<le> f i"
hoelzl@42950
   749
  shows "(\<Prod>i\<in>I. f i) = \<infinity> \<longleftrightarrow> finite I \<and> (\<exists>i\<in>I. f i = \<infinity>) \<and> (\<forall>i\<in>I. f i \<noteq> 0)"
hoelzl@42950
   750
proof cases
hoelzl@42950
   751
  assume "finite I" from this assms show ?thesis
hoelzl@42950
   752
  proof (induct I)
hoelzl@42950
   753
    case (insert i I)
hoelzl@43920
   754
    then have pos: "0 \<le> f i" "0 \<le> setprod f I" by (auto intro!: setprod_ereal_pos)
hoelzl@42950
   755
    from insert have "(\<Prod>j\<in>insert i I. f j) = \<infinity> \<longleftrightarrow> setprod f I * f i = \<infinity>" by auto
hoelzl@42950
   756
    also have "\<dots> \<longleftrightarrow> (setprod f I = \<infinity> \<or> f i = \<infinity>) \<and> f i \<noteq> 0 \<and> setprod f I \<noteq> 0"
hoelzl@43920
   757
      using setprod_ereal_pos[of I f] pos
hoelzl@43920
   758
      by (cases rule: ereal2_cases[of "f i" "setprod f I"]) auto
hoelzl@42950
   759
    also have "\<dots> \<longleftrightarrow> finite (insert i I) \<and> (\<exists>j\<in>insert i I. f j = \<infinity>) \<and> (\<forall>j\<in>insert i I. f j \<noteq> 0)"
hoelzl@43920
   760
      using insert by (auto simp: setprod_ereal_0)
hoelzl@42950
   761
    finally show ?case .
hoelzl@42950
   762
  qed simp
hoelzl@42950
   763
qed simp
hoelzl@42950
   764
hoelzl@43920
   765
lemma setprod_ereal: "(\<Prod>i\<in>A. ereal (f i)) = ereal (setprod f A)"
hoelzl@42950
   766
proof cases
hoelzl@42950
   767
  assume "finite A" then show ?thesis
hoelzl@43920
   768
    by induct (auto simp: one_ereal_def)
hoelzl@43920
   769
qed (simp add: one_ereal_def)
hoelzl@42950
   770
hoelzl@41978
   771
subsubsection {* Power *}
hoelzl@41978
   772
hoelzl@43920
   773
lemma ereal_power[simp]: "(ereal x) ^ n = ereal (x^n)"
hoelzl@43920
   774
  by (induct n) (auto simp: one_ereal_def)
hoelzl@41978
   775
hoelzl@43923
   776
lemma ereal_power_PInf[simp]: "(\<infinity>::ereal) ^ n = (if n = 0 then 1 else \<infinity>)"
hoelzl@43920
   777
  by (induct n) (auto simp: one_ereal_def)
hoelzl@41978
   778
hoelzl@43920
   779
lemma ereal_power_uminus[simp]:
hoelzl@43920
   780
  fixes x :: ereal
hoelzl@41978
   781
  shows "(- x) ^ n = (if even n then x ^ n else - (x^n))"
hoelzl@43920
   782
  by (induct n) (auto simp: one_ereal_def)
hoelzl@41978
   783
hoelzl@43920
   784
lemma ereal_power_number_of[simp]:
hoelzl@43920
   785
  "(number_of num :: ereal) ^ n = ereal (number_of num ^ n)"
hoelzl@43920
   786
  by (induct n) (auto simp: one_ereal_def)
hoelzl@41979
   787
hoelzl@43920
   788
lemma zero_le_power_ereal[simp]:
hoelzl@43920
   789
  fixes a :: ereal assumes "0 \<le> a"
hoelzl@41979
   790
  shows "0 \<le> a ^ n"
hoelzl@43920
   791
  using assms by (induct n) (auto simp: ereal_zero_le_0_iff)
hoelzl@41979
   792
hoelzl@41973
   793
subsubsection {* Subtraction *}
hoelzl@41973
   794
hoelzl@43920
   795
lemma ereal_minus_minus_image[simp]:
hoelzl@43920
   796
  fixes S :: "ereal set"
hoelzl@41973
   797
  shows "uminus ` uminus ` S = S"
hoelzl@41973
   798
  by (auto simp: image_iff)
hoelzl@41973
   799
hoelzl@43920
   800
lemma ereal_uminus_lessThan[simp]:
hoelzl@43920
   801
  fixes a :: ereal shows "uminus ` {..<a} = {-a<..}"
wenzelm@47082
   802
proof -
wenzelm@47082
   803
  {
wenzelm@47082
   804
    fix x assume "-a < x"
wenzelm@47082
   805
    then have "- x < - (- a)" by (simp del: ereal_uminus_uminus)
wenzelm@47082
   806
    then have "- x < a" by simp
wenzelm@47082
   807
  }
wenzelm@47082
   808
  then show ?thesis by (auto intro!: image_eqI)
wenzelm@47082
   809
qed
hoelzl@41973
   810
hoelzl@43920
   811
lemma ereal_uminus_greaterThan[simp]:
hoelzl@43920
   812
  "uminus ` {(a::ereal)<..} = {..<-a}"
hoelzl@43920
   813
  by (metis ereal_uminus_lessThan ereal_uminus_uminus
hoelzl@43920
   814
            ereal_minus_minus_image)
hoelzl@41973
   815
hoelzl@43920
   816
instantiation ereal :: minus
hoelzl@41973
   817
begin
hoelzl@43920
   818
definition "x - y = x + -(y::ereal)"
hoelzl@41973
   819
instance ..
hoelzl@41973
   820
end
hoelzl@41973
   821
hoelzl@43920
   822
lemma ereal_minus[simp]:
hoelzl@43920
   823
  "ereal r - ereal p = ereal (r - p)"
hoelzl@43920
   824
  "-\<infinity> - ereal r = -\<infinity>"
hoelzl@43920
   825
  "ereal r - \<infinity> = -\<infinity>"
hoelzl@43923
   826
  "(\<infinity>::ereal) - x = \<infinity>"
hoelzl@43923
   827
  "-(\<infinity>::ereal) - \<infinity> = -\<infinity>"
hoelzl@41973
   828
  "x - -y = x + y"
hoelzl@41973
   829
  "x - 0 = x"
hoelzl@41973
   830
  "0 - x = -x"
hoelzl@43920
   831
  by (simp_all add: minus_ereal_def)
hoelzl@41973
   832
hoelzl@43920
   833
lemma ereal_x_minus_x[simp]:
hoelzl@43923
   834
  "x - x = (if \<bar>x\<bar> = \<infinity> then \<infinity> else 0::ereal)"
hoelzl@41973
   835
  by (cases x) simp_all
hoelzl@41973
   836
hoelzl@43920
   837
lemma ereal_eq_minus_iff:
hoelzl@43920
   838
  fixes x y z :: ereal
hoelzl@41973
   839
  shows "x = z - y \<longleftrightarrow>
hoelzl@41976
   840
    (\<bar>y\<bar> \<noteq> \<infinity> \<longrightarrow> x + y = z) \<and>
hoelzl@41973
   841
    (y = -\<infinity> \<longrightarrow> x = \<infinity>) \<and>
hoelzl@41973
   842
    (y = \<infinity> \<longrightarrow> z = \<infinity> \<longrightarrow> x = \<infinity>) \<and>
hoelzl@41973
   843
    (y = \<infinity> \<longrightarrow> z \<noteq> \<infinity> \<longrightarrow> x = -\<infinity>)"
hoelzl@43920
   844
  by (cases rule: ereal3_cases[of x y z]) auto
hoelzl@41973
   845
hoelzl@43920
   846
lemma ereal_eq_minus:
hoelzl@43920
   847
  fixes x y z :: ereal
hoelzl@41976
   848
  shows "\<bar>y\<bar> \<noteq> \<infinity> \<Longrightarrow> x = z - y \<longleftrightarrow> x + y = z"
hoelzl@43920
   849
  by (auto simp: ereal_eq_minus_iff)
hoelzl@41973
   850
hoelzl@43920
   851
lemma ereal_less_minus_iff:
hoelzl@43920
   852
  fixes x y z :: ereal
hoelzl@41973
   853
  shows "x < z - y \<longleftrightarrow>
hoelzl@41973
   854
    (y = \<infinity> \<longrightarrow> z = \<infinity> \<and> x \<noteq> \<infinity>) \<and>
hoelzl@41973
   855
    (y = -\<infinity> \<longrightarrow> x \<noteq> \<infinity>) \<and>
hoelzl@41976
   856
    (\<bar>y\<bar> \<noteq> \<infinity>\<longrightarrow> x + y < z)"
hoelzl@43920
   857
  by (cases rule: ereal3_cases[of x y z]) auto
hoelzl@41973
   858
hoelzl@43920
   859
lemma ereal_less_minus:
hoelzl@43920
   860
  fixes x y z :: ereal
hoelzl@41976
   861
  shows "\<bar>y\<bar> \<noteq> \<infinity> \<Longrightarrow> x < z - y \<longleftrightarrow> x + y < z"
hoelzl@43920
   862
  by (auto simp: ereal_less_minus_iff)
hoelzl@41973
   863
hoelzl@43920
   864
lemma ereal_le_minus_iff:
hoelzl@43920
   865
  fixes x y z :: ereal
hoelzl@41973
   866
  shows "x \<le> z - y \<longleftrightarrow>
hoelzl@41973
   867
    (y = \<infinity> \<longrightarrow> z \<noteq> \<infinity> \<longrightarrow> x = -\<infinity>) \<and>
hoelzl@41976
   868
    (\<bar>y\<bar> \<noteq> \<infinity> \<longrightarrow> x + y \<le> z)"
hoelzl@43920
   869
  by (cases rule: ereal3_cases[of x y z]) auto
hoelzl@41973
   870
hoelzl@43920
   871
lemma ereal_le_minus:
hoelzl@43920
   872
  fixes x y z :: ereal
hoelzl@41976
   873
  shows "\<bar>y\<bar> \<noteq> \<infinity> \<Longrightarrow> x \<le> z - y \<longleftrightarrow> x + y \<le> z"
hoelzl@43920
   874
  by (auto simp: ereal_le_minus_iff)
hoelzl@41973
   875
hoelzl@43920
   876
lemma ereal_minus_less_iff:
hoelzl@43920
   877
  fixes x y z :: ereal
hoelzl@41973
   878
  shows "x - y < z \<longleftrightarrow>
hoelzl@41973
   879
    y \<noteq> -\<infinity> \<and> (y = \<infinity> \<longrightarrow> x \<noteq> \<infinity> \<and> z \<noteq> -\<infinity>) \<and>
hoelzl@41973
   880
    (y \<noteq> \<infinity> \<longrightarrow> x < z + y)"
hoelzl@43920
   881
  by (cases rule: ereal3_cases[of x y z]) auto
hoelzl@41973
   882
hoelzl@43920
   883
lemma ereal_minus_less:
hoelzl@43920
   884
  fixes x y z :: ereal
hoelzl@41976
   885
  shows "\<bar>y\<bar> \<noteq> \<infinity> \<Longrightarrow> x - y < z \<longleftrightarrow> x < z + y"
hoelzl@43920
   886
  by (auto simp: ereal_minus_less_iff)
hoelzl@41973
   887
hoelzl@43920
   888
lemma ereal_minus_le_iff:
hoelzl@43920
   889
  fixes x y z :: ereal
hoelzl@41973
   890
  shows "x - y \<le> z \<longleftrightarrow>
hoelzl@41973
   891
    (y = -\<infinity> \<longrightarrow> z = \<infinity>) \<and>
hoelzl@41973
   892
    (y = \<infinity> \<longrightarrow> x = \<infinity> \<longrightarrow> z = \<infinity>) \<and>
hoelzl@41976
   893
    (\<bar>y\<bar> \<noteq> \<infinity> \<longrightarrow> x \<le> z + y)"
hoelzl@43920
   894
  by (cases rule: ereal3_cases[of x y z]) auto
hoelzl@41973
   895
hoelzl@43920
   896
lemma ereal_minus_le:
hoelzl@43920
   897
  fixes x y z :: ereal
hoelzl@41976
   898
  shows "\<bar>y\<bar> \<noteq> \<infinity> \<Longrightarrow> x - y \<le> z \<longleftrightarrow> x \<le> z + y"
hoelzl@43920
   899
  by (auto simp: ereal_minus_le_iff)
hoelzl@41973
   900
hoelzl@43920
   901
lemma ereal_minus_eq_minus_iff:
hoelzl@43920
   902
  fixes a b c :: ereal
hoelzl@41973
   903
  shows "a - b = a - c \<longleftrightarrow>
hoelzl@41973
   904
    b = c \<or> a = \<infinity> \<or> (a = -\<infinity> \<and> b \<noteq> -\<infinity> \<and> c \<noteq> -\<infinity>)"
hoelzl@43920
   905
  by (cases rule: ereal3_cases[of a b c]) auto
hoelzl@41973
   906
hoelzl@43920
   907
lemma ereal_add_le_add_iff:
hoelzl@43923
   908
  fixes a b c :: ereal
hoelzl@43923
   909
  shows "c + a \<le> c + b \<longleftrightarrow>
hoelzl@41973
   910
    a \<le> b \<or> c = \<infinity> \<or> (c = -\<infinity> \<and> a \<noteq> \<infinity> \<and> b \<noteq> \<infinity>)"
hoelzl@43920
   911
  by (cases rule: ereal3_cases[of a b c]) (simp_all add: field_simps)
hoelzl@41973
   912
hoelzl@43920
   913
lemma ereal_mult_le_mult_iff:
hoelzl@43923
   914
  fixes a b c :: ereal
hoelzl@43923
   915
  shows "\<bar>c\<bar> \<noteq> \<infinity> \<Longrightarrow> c * a \<le> c * b \<longleftrightarrow> (0 < c \<longrightarrow> a \<le> b) \<and> (c < 0 \<longrightarrow> b \<le> a)"
hoelzl@43920
   916
  by (cases rule: ereal3_cases[of a b c]) (simp_all add: mult_le_cancel_left)
hoelzl@41973
   917
hoelzl@43920
   918
lemma ereal_minus_mono:
hoelzl@43920
   919
  fixes A B C D :: ereal assumes "A \<le> B" "D \<le> C"
hoelzl@41979
   920
  shows "A - C \<le> B - D"
hoelzl@41979
   921
  using assms
hoelzl@43920
   922
  by (cases rule: ereal3_cases[case_product ereal_cases, of A B C D]) simp_all
hoelzl@41979
   923
hoelzl@43920
   924
lemma real_of_ereal_minus:
hoelzl@43923
   925
  fixes a b :: ereal
hoelzl@43923
   926
  shows "real (a - b) = (if \<bar>a\<bar> = \<infinity> \<or> \<bar>b\<bar> = \<infinity> then 0 else real a - real b)"
hoelzl@43920
   927
  by (cases rule: ereal2_cases[of a b]) auto
hoelzl@41979
   928
hoelzl@43920
   929
lemma ereal_diff_positive:
hoelzl@43920
   930
  fixes a b :: ereal shows "a \<le> b \<Longrightarrow> 0 \<le> b - a"
hoelzl@43920
   931
  by (cases rule: ereal2_cases[of a b]) auto
hoelzl@41979
   932
hoelzl@43920
   933
lemma ereal_between:
hoelzl@43920
   934
  fixes x e :: ereal
hoelzl@41976
   935
  assumes "\<bar>x\<bar> \<noteq> \<infinity>" "0 < e"
hoelzl@41973
   936
  shows "x - e < x" "x < x + e"
hoelzl@41973
   937
using assms apply (cases x, cases e) apply auto
wenzelm@47082
   938
using assms apply (cases x, cases e) apply auto
wenzelm@47082
   939
done
hoelzl@41973
   940
hoelzl@41973
   941
subsubsection {* Division *}
hoelzl@41973
   942
hoelzl@43920
   943
instantiation ereal :: inverse
hoelzl@41973
   944
begin
hoelzl@41973
   945
hoelzl@43920
   946
function inverse_ereal where
hoelzl@43920
   947
"inverse (ereal r) = (if r = 0 then \<infinity> else ereal (inverse r))" |
hoelzl@43923
   948
"inverse (\<infinity>::ereal) = 0" |
hoelzl@43923
   949
"inverse (-\<infinity>::ereal) = 0"
hoelzl@43920
   950
  by (auto intro: ereal_cases)
hoelzl@41973
   951
termination by (relation "{}") simp
hoelzl@41973
   952
hoelzl@43920
   953
definition "x / y = x * inverse (y :: ereal)"
hoelzl@41973
   954
wenzelm@47082
   955
instance ..
hoelzl@41973
   956
end
hoelzl@41973
   957
hoelzl@43920
   958
lemma real_of_ereal_inverse[simp]:
hoelzl@43920
   959
  fixes a :: ereal
hoelzl@42950
   960
  shows "real (inverse a) = 1 / real a"
hoelzl@42950
   961
  by (cases a) (auto simp: inverse_eq_divide)
hoelzl@42950
   962
hoelzl@43920
   963
lemma ereal_inverse[simp]:
hoelzl@43923
   964
  "inverse (0::ereal) = \<infinity>"
hoelzl@43920
   965
  "inverse (1::ereal) = 1"
hoelzl@43920
   966
  by (simp_all add: one_ereal_def zero_ereal_def)
hoelzl@41973
   967
hoelzl@43920
   968
lemma ereal_divide[simp]:
hoelzl@43920
   969
  "ereal r / ereal p = (if p = 0 then ereal r * \<infinity> else ereal (r / p))"
hoelzl@43920
   970
  unfolding divide_ereal_def by (auto simp: divide_real_def)
hoelzl@41973
   971
hoelzl@43920
   972
lemma ereal_divide_same[simp]:
hoelzl@43923
   973
  fixes x :: ereal shows "x / x = (if \<bar>x\<bar> = \<infinity> \<or> x = 0 then 0 else 1)"
hoelzl@41973
   974
  by (cases x)
hoelzl@43920
   975
     (simp_all add: divide_real_def divide_ereal_def one_ereal_def)
hoelzl@41973
   976
hoelzl@43920
   977
lemma ereal_inv_inv[simp]:
hoelzl@43923
   978
  fixes x :: ereal shows "inverse (inverse x) = (if x \<noteq> -\<infinity> then x else \<infinity>)"
hoelzl@41973
   979
  by (cases x) auto
hoelzl@41973
   980
hoelzl@43920
   981
lemma ereal_inverse_minus[simp]:
hoelzl@43923
   982
  fixes x :: ereal shows "inverse (- x) = (if x = 0 then \<infinity> else -inverse x)"
hoelzl@41973
   983
  by (cases x) simp_all
hoelzl@41973
   984
hoelzl@43920
   985
lemma ereal_uminus_divide[simp]:
hoelzl@43920
   986
  fixes x y :: ereal shows "- x / y = - (x / y)"
hoelzl@43920
   987
  unfolding divide_ereal_def by simp
hoelzl@41973
   988
hoelzl@43920
   989
lemma ereal_divide_Infty[simp]:
hoelzl@43923
   990
  fixes x :: ereal shows "x / \<infinity> = 0" "x / -\<infinity> = 0"
hoelzl@43920
   991
  unfolding divide_ereal_def by simp_all
hoelzl@41973
   992
hoelzl@43920
   993
lemma ereal_divide_one[simp]:
hoelzl@43920
   994
  "x / 1 = (x::ereal)"
hoelzl@43920
   995
  unfolding divide_ereal_def by simp
hoelzl@41973
   996
hoelzl@43920
   997
lemma ereal_divide_ereal[simp]:
hoelzl@43920
   998
  "\<infinity> / ereal r = (if 0 \<le> r then \<infinity> else -\<infinity>)"
hoelzl@43920
   999
  unfolding divide_ereal_def by simp
hoelzl@41973
  1000
hoelzl@43920
  1001
lemma zero_le_divide_ereal[simp]:
hoelzl@43920
  1002
  fixes a :: ereal assumes "0 \<le> a" "0 \<le> b"
hoelzl@41978
  1003
  shows "0 \<le> a / b"
hoelzl@43920
  1004
  using assms by (cases rule: ereal2_cases[of a b]) (auto simp: zero_le_divide_iff)
hoelzl@41978
  1005
hoelzl@43920
  1006
lemma ereal_le_divide_pos:
hoelzl@43923
  1007
  fixes x y z :: ereal shows "x > 0 \<Longrightarrow> x \<noteq> \<infinity> \<Longrightarrow> y \<le> z / x \<longleftrightarrow> x * y \<le> z"
hoelzl@43920
  1008
  by (cases rule: ereal3_cases[of x y z]) (auto simp: field_simps)
hoelzl@41973
  1009
hoelzl@43920
  1010
lemma ereal_divide_le_pos:
hoelzl@43923
  1011
  fixes x y z :: ereal shows "x > 0 \<Longrightarrow> x \<noteq> \<infinity> \<Longrightarrow> z / x \<le> y \<longleftrightarrow> z \<le> x * y"
hoelzl@43920
  1012
  by (cases rule: ereal3_cases[of x y z]) (auto simp: field_simps)
hoelzl@41973
  1013
hoelzl@43920
  1014
lemma ereal_le_divide_neg:
hoelzl@43923
  1015
  fixes x y z :: ereal shows "x < 0 \<Longrightarrow> x \<noteq> -\<infinity> \<Longrightarrow> y \<le> z / x \<longleftrightarrow> z \<le> x * y"
hoelzl@43920
  1016
  by (cases rule: ereal3_cases[of x y z]) (auto simp: field_simps)
hoelzl@41973
  1017
hoelzl@43920
  1018
lemma ereal_divide_le_neg:
hoelzl@43923
  1019
  fixes x y z :: ereal shows "x < 0 \<Longrightarrow> x \<noteq> -\<infinity> \<Longrightarrow> z / x \<le> y \<longleftrightarrow> x * y \<le> z"
hoelzl@43920
  1020
  by (cases rule: ereal3_cases[of x y z]) (auto simp: field_simps)
hoelzl@41973
  1021
hoelzl@43920
  1022
lemma ereal_inverse_antimono_strict:
hoelzl@43920
  1023
  fixes x y :: ereal
hoelzl@41973
  1024
  shows "0 \<le> x \<Longrightarrow> x < y \<Longrightarrow> inverse y < inverse x"
hoelzl@43920
  1025
  by (cases rule: ereal2_cases[of x y]) auto
hoelzl@41973
  1026
hoelzl@43920
  1027
lemma ereal_inverse_antimono:
hoelzl@43920
  1028
  fixes x y :: ereal
hoelzl@41973
  1029
  shows "0 \<le> x \<Longrightarrow> x <= y \<Longrightarrow> inverse y <= inverse x"
hoelzl@43920
  1030
  by (cases rule: ereal2_cases[of x y]) auto
hoelzl@41973
  1031
hoelzl@41973
  1032
lemma inverse_inverse_Pinfty_iff[simp]:
hoelzl@43923
  1033
  fixes x :: ereal shows "inverse x = \<infinity> \<longleftrightarrow> x = 0"
hoelzl@41973
  1034
  by (cases x) auto
hoelzl@41973
  1035
hoelzl@43920
  1036
lemma ereal_inverse_eq_0:
hoelzl@43923
  1037
  fixes x :: ereal shows "inverse x = 0 \<longleftrightarrow> x = \<infinity> \<or> x = -\<infinity>"
hoelzl@41973
  1038
  by (cases x) auto
hoelzl@41973
  1039
hoelzl@43920
  1040
lemma ereal_0_gt_inverse:
hoelzl@43920
  1041
  fixes x :: ereal shows "0 < inverse x \<longleftrightarrow> x \<noteq> \<infinity> \<and> 0 \<le> x"
hoelzl@41979
  1042
  by (cases x) auto
hoelzl@41979
  1043
hoelzl@43920
  1044
lemma ereal_mult_less_right:
hoelzl@43923
  1045
  fixes a b c :: ereal
hoelzl@41973
  1046
  assumes "b * a < c * a" "0 < a" "a < \<infinity>"
hoelzl@41973
  1047
  shows "b < c"
hoelzl@41973
  1048
  using assms
hoelzl@43920
  1049
  by (cases rule: ereal3_cases[of a b c])
hoelzl@41973
  1050
     (auto split: split_if_asm simp: zero_less_mult_iff zero_le_mult_iff)
hoelzl@41973
  1051
hoelzl@43920
  1052
lemma ereal_power_divide:
hoelzl@43923
  1053
  fixes x y :: ereal shows "y \<noteq> 0 \<Longrightarrow> (x / y) ^ n = x^n / y^n"
hoelzl@43920
  1054
  by (cases rule: ereal2_cases[of x y])
hoelzl@43920
  1055
     (auto simp: one_ereal_def zero_ereal_def power_divide not_le
hoelzl@41979
  1056
                 power_less_zero_eq zero_le_power_iff)
hoelzl@41979
  1057
hoelzl@43920
  1058
lemma ereal_le_mult_one_interval:
hoelzl@43920
  1059
  fixes x y :: ereal
hoelzl@41979
  1060
  assumes y: "y \<noteq> -\<infinity>"
hoelzl@41979
  1061
  assumes z: "\<And>z. \<lbrakk> 0 < z ; z < 1 \<rbrakk> \<Longrightarrow> z * x \<le> y"
hoelzl@41979
  1062
  shows "x \<le> y"
hoelzl@41979
  1063
proof (cases x)
hoelzl@43920
  1064
  case PInf with z[of "1 / 2"] show "x \<le> y" by (simp add: one_ereal_def)
hoelzl@41979
  1065
next
hoelzl@41979
  1066
  case (real r) note r = this
hoelzl@41979
  1067
  show "x \<le> y"
hoelzl@41979
  1068
  proof (cases y)
hoelzl@41979
  1069
    case (real p) note p = this
hoelzl@41979
  1070
    have "r \<le> p"
hoelzl@41979
  1071
    proof (rule field_le_mult_one_interval)
hoelzl@41979
  1072
      fix z :: real assume "0 < z" and "z < 1"
hoelzl@43920
  1073
      with z[of "ereal z"]
hoelzl@43920
  1074
      show "z * r \<le> p" using p r by (auto simp: zero_le_mult_iff one_ereal_def)
hoelzl@41979
  1075
    qed
hoelzl@41979
  1076
    then show "x \<le> y" using p r by simp
hoelzl@41979
  1077
  qed (insert y, simp_all)
hoelzl@41979
  1078
qed simp
hoelzl@41978
  1079
noschinl@45934
  1080
lemma ereal_divide_right_mono[simp]:
noschinl@45934
  1081
  fixes x y z :: ereal
noschinl@45934
  1082
  assumes "x \<le> y" "0 < z" shows "x / z \<le> y / z"
noschinl@45934
  1083
using assms by (cases x y z rule: ereal3_cases) (auto intro: divide_right_mono)
noschinl@45934
  1084
noschinl@45934
  1085
lemma ereal_divide_left_mono[simp]:
noschinl@45934
  1086
  fixes x y z :: ereal
noschinl@45934
  1087
  assumes "y \<le> x" "0 < z" "0 < x * y"
noschinl@45934
  1088
  shows "z / x \<le> z / y"
noschinl@45934
  1089
using assms by (cases x y z rule: ereal3_cases)
noschinl@45934
  1090
  (auto intro: divide_left_mono simp: field_simps sign_simps split: split_if_asm)
noschinl@45934
  1091
noschinl@45934
  1092
lemma ereal_divide_zero_left[simp]:
noschinl@45934
  1093
  fixes a :: ereal
noschinl@45934
  1094
  shows "0 / a = 0"
noschinl@45934
  1095
  by (cases a) (auto simp: zero_ereal_def)
noschinl@45934
  1096
noschinl@45934
  1097
lemma ereal_times_divide_eq_left[simp]:
noschinl@45934
  1098
  fixes a b c :: ereal
noschinl@45934
  1099
  shows "b / c * a = b * a / c"
noschinl@45934
  1100
  by (cases a b c rule: ereal3_cases) (auto simp: field_simps sign_simps)
noschinl@45934
  1101
hoelzl@41973
  1102
subsection "Complete lattice"
hoelzl@41973
  1103
hoelzl@43920
  1104
instantiation ereal :: lattice
hoelzl@41973
  1105
begin
hoelzl@43920
  1106
definition [simp]: "sup x y = (max x y :: ereal)"
hoelzl@43920
  1107
definition [simp]: "inf x y = (min x y :: ereal)"
wenzelm@47082
  1108
instance by default simp_all
hoelzl@41973
  1109
end
hoelzl@41973
  1110
hoelzl@43920
  1111
instantiation ereal :: complete_lattice
hoelzl@41973
  1112
begin
hoelzl@41973
  1113
hoelzl@43923
  1114
definition "bot = (-\<infinity>::ereal)"
hoelzl@43923
  1115
definition "top = (\<infinity>::ereal)"
hoelzl@41973
  1116
hoelzl@43923
  1117
definition "Sup S = (LEAST z. \<forall>x\<in>S. x \<le> z :: ereal)"
hoelzl@43923
  1118
definition "Inf S = (GREATEST z. \<forall>x\<in>S. z \<le> x :: ereal)"
hoelzl@41973
  1119
hoelzl@43920
  1120
lemma ereal_complete_Sup:
hoelzl@43920
  1121
  fixes S :: "ereal set" assumes "S \<noteq> {}"
hoelzl@41973
  1122
  shows "\<exists>x. (\<forall>y\<in>S. y \<le> x) \<and> (\<forall>z. (\<forall>y\<in>S. y \<le> z) \<longrightarrow> x \<le> z)"
hoelzl@41973
  1123
proof cases
hoelzl@43920
  1124
  assume "\<exists>x. \<forall>a\<in>S. a \<le> ereal x"
hoelzl@43920
  1125
  then obtain y where y: "\<And>a. a\<in>S \<Longrightarrow> a \<le> ereal y" by auto
hoelzl@41973
  1126
  then have "\<infinity> \<notin> S" by force
hoelzl@41973
  1127
  show ?thesis
hoelzl@41973
  1128
  proof cases
hoelzl@41973
  1129
    assume "S = {-\<infinity>}"
hoelzl@41973
  1130
    then show ?thesis by (auto intro!: exI[of _ "-\<infinity>"])
hoelzl@41973
  1131
  next
hoelzl@41973
  1132
    assume "S \<noteq> {-\<infinity>}"
hoelzl@41973
  1133
    with `S \<noteq> {}` `\<infinity> \<notin> S` obtain x where "x \<in> S - {-\<infinity>}" "x \<noteq> \<infinity>" by auto
hoelzl@41973
  1134
    with y `\<infinity> \<notin> S` have "\<forall>z\<in>real ` (S - {-\<infinity>}). z \<le> y"
hoelzl@43920
  1135
      by (auto simp: real_of_ereal_ord_simps)
huffman@44669
  1136
    with complete_real[of "real ` (S - {-\<infinity>})"] `x \<in> S - {-\<infinity>}`
hoelzl@41973
  1137
    obtain s where s:
hoelzl@41973
  1138
       "\<forall>y\<in>S - {-\<infinity>}. real y \<le> s" "\<And>z. (\<forall>y\<in>S - {-\<infinity>}. real y \<le> z) \<Longrightarrow> s \<le> z"
hoelzl@41973
  1139
       by auto
hoelzl@41973
  1140
    show ?thesis
hoelzl@43920
  1141
    proof (safe intro!: exI[of _ "ereal s"])
hoelzl@43920
  1142
      fix z assume "z \<in> S" with `\<infinity> \<notin> S` show "z \<le> ereal s"
hoelzl@41973
  1143
      proof (cases z)
hoelzl@41973
  1144
        case (real r)
hoelzl@41973
  1145
        then show ?thesis
hoelzl@43920
  1146
          using s(1)[rule_format, of z] `z \<in> S` `z = ereal r` by auto
hoelzl@41973
  1147
      qed auto
hoelzl@41973
  1148
    next
hoelzl@41973
  1149
      fix z assume *: "\<forall>y\<in>S. y \<le> z"
hoelzl@43920
  1150
      with `S \<noteq> {-\<infinity>}` `S \<noteq> {}` show "ereal s \<le> z"
hoelzl@41973
  1151
      proof (cases z)
hoelzl@41973
  1152
        case (real u)
hoelzl@41973
  1153
        with * have "s \<le> u"
hoelzl@43920
  1154
          by (intro s(2)[of u]) (auto simp: real_of_ereal_ord_simps)
hoelzl@41973
  1155
        then show ?thesis using real by simp
hoelzl@41973
  1156
      qed auto
hoelzl@41973
  1157
    qed
hoelzl@41973
  1158
  qed
hoelzl@41973
  1159
next
hoelzl@43920
  1160
  assume *: "\<not> (\<exists>x. \<forall>a\<in>S. a \<le> ereal x)"
hoelzl@41973
  1161
  show ?thesis
hoelzl@41973
  1162
  proof (safe intro!: exI[of _ \<infinity>])
hoelzl@41973
  1163
    fix y assume **: "\<forall>z\<in>S. z \<le> y"
hoelzl@41973
  1164
    with * show "\<infinity> \<le> y"
hoelzl@41973
  1165
    proof (cases y)
hoelzl@41973
  1166
      case MInf with * ** show ?thesis by (force simp: not_le)
hoelzl@41973
  1167
    qed auto
hoelzl@41973
  1168
  qed simp
hoelzl@41973
  1169
qed
hoelzl@41973
  1170
hoelzl@43920
  1171
lemma ereal_complete_Inf:
hoelzl@43920
  1172
  fixes S :: "ereal set" assumes "S ~= {}"
hoelzl@41973
  1173
  shows "EX x. (ALL y:S. x <= y) & (ALL z. (ALL y:S. z <= y) --> z <= x)"
hoelzl@41973
  1174
proof-
hoelzl@41973
  1175
def S1 == "uminus ` S"
hoelzl@41973
  1176
hence "S1 ~= {}" using assms by auto
wenzelm@47082
  1177
then obtain x where x_def: "(ALL y:S1. y <= x) & (ALL z. (ALL y:S1. y <= z) --> x <= z)"
hoelzl@43920
  1178
   using ereal_complete_Sup[of S1] by auto
hoelzl@41973
  1179
{ fix z assume "ALL y:S. z <= y"
hoelzl@41973
  1180
  hence "ALL y:S1. y <= -z" unfolding S1_def by auto
hoelzl@41973
  1181
  hence "x <= -z" using x_def by auto
hoelzl@41973
  1182
  hence "z <= -x"
hoelzl@43920
  1183
    apply (subst ereal_uminus_uminus[symmetric])
hoelzl@43920
  1184
    unfolding ereal_minus_le_minus . }
hoelzl@41973
  1185
moreover have "(ALL y:S. -x <= y)"
hoelzl@41973
  1186
   using x_def unfolding S1_def
hoelzl@41973
  1187
   apply simp
hoelzl@43920
  1188
   apply (subst (3) ereal_uminus_uminus[symmetric])
hoelzl@43920
  1189
   unfolding ereal_minus_le_minus by simp
hoelzl@41973
  1190
ultimately show ?thesis by auto
hoelzl@41973
  1191
qed
hoelzl@41973
  1192
hoelzl@43920
  1193
lemma ereal_complete_uminus_eq:
hoelzl@43920
  1194
  fixes S :: "ereal set"
hoelzl@41973
  1195
  shows "(\<forall>y\<in>uminus`S. y \<le> x) \<and> (\<forall>z. (\<forall>y\<in>uminus`S. y \<le> z) \<longrightarrow> x \<le> z)
hoelzl@41973
  1196
     \<longleftrightarrow> (\<forall>y\<in>S. -x \<le> y) \<and> (\<forall>z. (\<forall>y\<in>S. z \<le> y) \<longrightarrow> z \<le> -x)"
hoelzl@43920
  1197
  by simp (metis ereal_minus_le_minus ereal_uminus_uminus)
hoelzl@41973
  1198
hoelzl@43920
  1199
lemma ereal_Sup_uminus_image_eq:
hoelzl@43920
  1200
  fixes S :: "ereal set"
hoelzl@41973
  1201
  shows "Sup (uminus ` S) = - Inf S"
hoelzl@41973
  1202
proof cases
hoelzl@41973
  1203
  assume "S = {}"
hoelzl@43920
  1204
  moreover have "(THE x. All (op \<le> x)) = (-\<infinity>::ereal)"
hoelzl@43920
  1205
    by (rule the_equality) (auto intro!: ereal_bot)
hoelzl@43920
  1206
  moreover have "(SOME x. \<forall>y. y \<le> x) = (\<infinity>::ereal)"
hoelzl@43920
  1207
    by (rule some_equality) (auto intro!: ereal_top)
hoelzl@43920
  1208
  ultimately show ?thesis unfolding Inf_ereal_def Sup_ereal_def
hoelzl@41973
  1209
    Least_def Greatest_def GreatestM_def by simp
hoelzl@41973
  1210
next
hoelzl@41973
  1211
  assume "S \<noteq> {}"
hoelzl@43920
  1212
  with ereal_complete_Sup[of "uminus`S"]
hoelzl@41973
  1213
  obtain x where x: "(\<forall>y\<in>S. -x \<le> y) \<and> (\<forall>z. (\<forall>y\<in>S. z \<le> y) \<longrightarrow> z \<le> -x)"
hoelzl@43920
  1214
    unfolding ereal_complete_uminus_eq by auto
hoelzl@41973
  1215
  show "Sup (uminus ` S) = - Inf S"
hoelzl@43920
  1216
    unfolding Inf_ereal_def Greatest_def GreatestM_def
hoelzl@41973
  1217
  proof (intro someI2[of _ _ "\<lambda>x. Sup (uminus`S) = - x"])
hoelzl@41973
  1218
    show "(\<forall>y\<in>S. -x \<le> y) \<and> (\<forall>y. (\<forall>z\<in>S. y \<le> z) \<longrightarrow> y \<le> -x)"
hoelzl@41973
  1219
      using x .
hoelzl@41973
  1220
    fix x' assume "(\<forall>y\<in>S. x' \<le> y) \<and> (\<forall>y. (\<forall>z\<in>S. y \<le> z) \<longrightarrow> y \<le> x')"
hoelzl@41973
  1221
    then have "(\<forall>y\<in>uminus`S. y \<le> - x') \<and> (\<forall>y. (\<forall>z\<in>uminus`S. z \<le> y) \<longrightarrow> - x' \<le> y)"
hoelzl@43920
  1222
      unfolding ereal_complete_uminus_eq by simp
hoelzl@41973
  1223
    then show "Sup (uminus ` S) = -x'"
hoelzl@43920
  1224
      unfolding Sup_ereal_def ereal_uminus_eq_iff
hoelzl@41973
  1225
      by (intro Least_equality) auto
hoelzl@41973
  1226
  qed
hoelzl@41973
  1227
qed
hoelzl@41973
  1228
hoelzl@41973
  1229
instance
hoelzl@41973
  1230
proof
hoelzl@43920
  1231
  { fix x :: ereal and A
hoelzl@43920
  1232
    show "bot <= x" by (cases x) (simp_all add: bot_ereal_def)
hoelzl@43920
  1233
    show "x <= top" by (simp add: top_ereal_def) }
hoelzl@41973
  1234
hoelzl@43920
  1235
  { fix x :: ereal and A assume "x : A"
hoelzl@43920
  1236
    with ereal_complete_Sup[of A]
hoelzl@41973
  1237
    obtain s where s: "\<forall>y\<in>A. y <= s" "\<forall>z. (\<forall>y\<in>A. y <= z) \<longrightarrow> s <= z" by auto
hoelzl@41973
  1238
    hence "x <= s" using `x : A` by auto
hoelzl@43920
  1239
    also have "... = Sup A" using s unfolding Sup_ereal_def
hoelzl@41973
  1240
      by (auto intro!: Least_equality[symmetric])
hoelzl@41973
  1241
    finally show "x <= Sup A" . }
hoelzl@41973
  1242
  note le_Sup = this
hoelzl@41973
  1243
hoelzl@43920
  1244
  { fix x :: ereal and A assume *: "!!z. (z : A ==> z <= x)"
hoelzl@41973
  1245
    show "Sup A <= x"
hoelzl@41973
  1246
    proof (cases "A = {}")
hoelzl@41973
  1247
      case True
hoelzl@43920
  1248
      hence "Sup A = -\<infinity>" unfolding Sup_ereal_def
hoelzl@41973
  1249
        by (auto intro!: Least_equality)
hoelzl@41973
  1250
      thus "Sup A <= x" by simp
hoelzl@41973
  1251
    next
hoelzl@41973
  1252
      case False
hoelzl@43920
  1253
      with ereal_complete_Sup[of A]
hoelzl@41973
  1254
      obtain s where s: "\<forall>y\<in>A. y <= s" "\<forall>z. (\<forall>y\<in>A. y <= z) \<longrightarrow> s <= z" by auto
hoelzl@41973
  1255
      hence "Sup A = s"
hoelzl@43920
  1256
        unfolding Sup_ereal_def by (auto intro!: Least_equality)
hoelzl@41973
  1257
      also have "s <= x" using * s by auto
hoelzl@41973
  1258
      finally show "Sup A <= x" .
hoelzl@41973
  1259
    qed }
hoelzl@41973
  1260
  note Sup_le = this
hoelzl@41973
  1261
hoelzl@43920
  1262
  { fix x :: ereal and A assume "x \<in> A"
hoelzl@41973
  1263
    with le_Sup[of "-x" "uminus`A"] show "Inf A \<le> x"
hoelzl@43920
  1264
      unfolding ereal_Sup_uminus_image_eq by simp }
hoelzl@41973
  1265
hoelzl@43920
  1266
  { fix x :: ereal and A assume *: "!!z. (z : A ==> x <= z)"
hoelzl@41973
  1267
    with Sup_le[of "uminus`A" "-x"] show "x \<le> Inf A"
hoelzl@43920
  1268
      unfolding ereal_Sup_uminus_image_eq by force }
hoelzl@41973
  1269
qed
haftmann@43941
  1270
hoelzl@41973
  1271
end
hoelzl@41973
  1272
haftmann@43941
  1273
instance ereal :: complete_linorder ..
haftmann@43941
  1274
hoelzl@43920
  1275
lemma ereal_SUPR_uminus:
hoelzl@43920
  1276
  fixes f :: "'a => ereal"
hoelzl@41973
  1277
  shows "(SUP i : R. -(f i)) = -(INF i : R. f i)"
hoelzl@44928
  1278
  unfolding SUP_def INF_def
hoelzl@43920
  1279
  using ereal_Sup_uminus_image_eq[of "f`R"]
hoelzl@41973
  1280
  by (simp add: image_image)
hoelzl@41973
  1281
hoelzl@43920
  1282
lemma ereal_INFI_uminus:
hoelzl@43920
  1283
  fixes f :: "'a => ereal"
hoelzl@41973
  1284
  shows "(INF i : R. -(f i)) = -(SUP i : R. f i)"
hoelzl@43920
  1285
  using ereal_SUPR_uminus[of _ "\<lambda>x. - f x"] by simp
hoelzl@41973
  1286
hoelzl@43920
  1287
lemma ereal_Inf_uminus_image_eq: "Inf (uminus ` S) = - Sup (S::ereal set)"
hoelzl@43920
  1288
  using ereal_Sup_uminus_image_eq[of "uminus ` S"] by (simp add: image_image)
hoelzl@41979
  1289
hoelzl@43920
  1290
lemma ereal_inj_on_uminus[intro, simp]: "inj_on uminus (A :: ereal set)"
hoelzl@41973
  1291
  by (auto intro!: inj_onI)
hoelzl@41973
  1292
hoelzl@43920
  1293
lemma ereal_image_uminus_shift:
hoelzl@43920
  1294
  fixes X Y :: "ereal set" shows "uminus ` X = Y \<longleftrightarrow> X = uminus ` Y"
hoelzl@41973
  1295
proof
hoelzl@41973
  1296
  assume "uminus ` X = Y"
hoelzl@41973
  1297
  then have "uminus ` uminus ` X = uminus ` Y"
hoelzl@41973
  1298
    by (simp add: inj_image_eq_iff)
hoelzl@41973
  1299
  then show "X = uminus ` Y" by (simp add: image_image)
hoelzl@41973
  1300
qed (simp add: image_image)
hoelzl@41973
  1301
hoelzl@43920
  1302
lemma Inf_ereal_iff:
hoelzl@43920
  1303
  fixes z :: ereal
hoelzl@41973
  1304
  shows "(!!x. x:X ==> z <= x) ==> (EX x:X. x<y) <-> Inf X < y"
hoelzl@41973
  1305
  by (metis complete_lattice_class.Inf_greatest complete_lattice_class.Inf_lower less_le_not_le linear
hoelzl@41973
  1306
            order_less_le_trans)
hoelzl@41973
  1307
hoelzl@41973
  1308
lemma Sup_eq_MInfty:
hoelzl@43920
  1309
  fixes S :: "ereal set" shows "Sup S = -\<infinity> \<longleftrightarrow> S = {} \<or> S = {-\<infinity>}"
hoelzl@41973
  1310
proof
hoelzl@41973
  1311
  assume a: "Sup S = -\<infinity>"
hoelzl@41973
  1312
  with complete_lattice_class.Sup_upper[of _ S]
hoelzl@41973
  1313
  show "S={} \<or> S={-\<infinity>}" by auto
hoelzl@41973
  1314
next
hoelzl@41973
  1315
  assume "S={} \<or> S={-\<infinity>}" then show "Sup S = -\<infinity>"
hoelzl@43920
  1316
    unfolding Sup_ereal_def by (auto intro!: Least_equality)
hoelzl@41973
  1317
qed
hoelzl@41973
  1318
hoelzl@41973
  1319
lemma Inf_eq_PInfty:
hoelzl@43920
  1320
  fixes S :: "ereal set" shows "Inf S = \<infinity> \<longleftrightarrow> S = {} \<or> S = {\<infinity>}"
hoelzl@41973
  1321
  using Sup_eq_MInfty[of "uminus`S"]
hoelzl@43920
  1322
  unfolding ereal_Sup_uminus_image_eq ereal_image_uminus_shift by simp
hoelzl@41973
  1323
hoelzl@43923
  1324
lemma Inf_eq_MInfty: 
hoelzl@43923
  1325
  fixes S :: "ereal set" shows "-\<infinity> \<in> S \<Longrightarrow> Inf S = -\<infinity>"
hoelzl@43920
  1326
  unfolding Inf_ereal_def
hoelzl@41973
  1327
  by (auto intro!: Greatest_equality)
hoelzl@41973
  1328
hoelzl@43923
  1329
lemma Sup_eq_PInfty:
hoelzl@43923
  1330
  fixes S :: "ereal set" shows "\<infinity> \<in> S \<Longrightarrow> Sup S = \<infinity>"
hoelzl@43920
  1331
  unfolding Sup_ereal_def
hoelzl@41973
  1332
  by (auto intro!: Least_equality)
hoelzl@41973
  1333
hoelzl@43920
  1334
lemma ereal_SUPI:
hoelzl@43920
  1335
  fixes x :: ereal
hoelzl@41973
  1336
  assumes "!!i. i : A ==> f i <= x"
hoelzl@41973
  1337
  assumes "!!y. (!!i. i : A ==> f i <= y) ==> x <= y"
hoelzl@41973
  1338
  shows "(SUP i:A. f i) = x"
hoelzl@44928
  1339
  unfolding SUP_def Sup_ereal_def
hoelzl@41973
  1340
  using assms by (auto intro!: Least_equality)
hoelzl@41973
  1341
hoelzl@43920
  1342
lemma ereal_INFI:
hoelzl@43920
  1343
  fixes x :: ereal
hoelzl@41973
  1344
  assumes "!!i. i : A ==> f i >= x"
hoelzl@41973
  1345
  assumes "!!y. (!!i. i : A ==> f i >= y) ==> x >= y"
hoelzl@41973
  1346
  shows "(INF i:A. f i) = x"
hoelzl@44928
  1347
  unfolding INF_def Inf_ereal_def
hoelzl@41973
  1348
  using assms by (auto intro!: Greatest_equality)
hoelzl@41973
  1349
hoelzl@43920
  1350
lemma Sup_ereal_close:
hoelzl@43920
  1351
  fixes e :: ereal
hoelzl@41976
  1352
  assumes "0 < e" and S: "\<bar>Sup S\<bar> \<noteq> \<infinity>" "S \<noteq> {}"
hoelzl@41973
  1353
  shows "\<exists>x\<in>S. Sup S - e < x"
hoelzl@41976
  1354
  using assms by (cases e) (auto intro!: less_Sup_iff[THEN iffD1])
hoelzl@41973
  1355
hoelzl@43920
  1356
lemma Inf_ereal_close:
hoelzl@43920
  1357
  fixes e :: ereal assumes "\<bar>Inf X\<bar> \<noteq> \<infinity>" "0 < e"
hoelzl@41973
  1358
  shows "\<exists>x\<in>X. x < Inf X + e"
hoelzl@41973
  1359
proof (rule Inf_less_iff[THEN iffD1])
hoelzl@41973
  1360
  show "Inf X < Inf X + e" using assms
hoelzl@41976
  1361
    by (cases e) auto
hoelzl@41973
  1362
qed
hoelzl@41973
  1363
hoelzl@43920
  1364
lemma SUP_nat_Infty: "(SUP i::nat. ereal (real i)) = \<infinity>"
hoelzl@41973
  1365
proof -
hoelzl@43923
  1366
  { fix x ::ereal assume "x \<noteq> \<infinity>"
hoelzl@43920
  1367
    then have "\<exists>k::nat. x < ereal (real k)"
hoelzl@41973
  1368
    proof (cases x)
hoelzl@41973
  1369
      case MInf then show ?thesis by (intro exI[of _ 0]) auto
hoelzl@41973
  1370
    next
hoelzl@41973
  1371
      case (real r)
hoelzl@41973
  1372
      moreover obtain k :: nat where "r < real k"
hoelzl@41973
  1373
        using ex_less_of_nat by (auto simp: real_eq_of_nat)
hoelzl@41973
  1374
      ultimately show ?thesis by auto
hoelzl@41973
  1375
    qed simp }
hoelzl@41973
  1376
  then show ?thesis
hoelzl@43920
  1377
    using SUP_eq_top_iff[of UNIV "\<lambda>n::nat. ereal (real n)"]
hoelzl@43920
  1378
    by (auto simp: top_ereal_def)
hoelzl@41973
  1379
qed
hoelzl@41973
  1380
hoelzl@43920
  1381
lemma ereal_le_Sup:
hoelzl@43920
  1382
  fixes x :: ereal
hoelzl@41973
  1383
  shows "(x <= (SUP i:A. f i)) <-> (ALL y. y < x --> (EX i. i : A & y <= f i))"
hoelzl@41973
  1384
(is "?lhs <-> ?rhs")
hoelzl@41973
  1385
proof-
hoelzl@41973
  1386
{ assume "?rhs"
hoelzl@41973
  1387
  { assume "~(x <= (SUP i:A. f i))" hence "(SUP i:A. f i)<x" by (simp add: not_le)
wenzelm@47082
  1388
    then obtain y where y_def: "(SUP i:A. f i)<y & y<x" using ereal_dense by auto
wenzelm@47082
  1389
    then obtain i where "i : A & y <= f i" using `?rhs` by auto
hoelzl@44928
  1390
    hence "y <= (SUP i:A. f i)" using SUP_upper[of i A f] by auto
hoelzl@41973
  1391
    hence False using y_def by auto
hoelzl@41973
  1392
  } hence "?lhs" by auto
hoelzl@41973
  1393
}
hoelzl@41973
  1394
moreover
hoelzl@41973
  1395
{ assume "?lhs" hence "?rhs"
bulwahn@45236
  1396
  by (metis less_SUP_iff order_less_imp_le order_less_le_trans)
hoelzl@41973
  1397
} ultimately show ?thesis by auto
hoelzl@41973
  1398
qed
hoelzl@41973
  1399
hoelzl@43920
  1400
lemma ereal_Inf_le:
hoelzl@43920
  1401
  fixes x :: ereal
hoelzl@41973
  1402
  shows "((INF i:A. f i) <= x) <-> (ALL y. x < y --> (EX i. i : A & f i <= y))"
hoelzl@41973
  1403
(is "?lhs <-> ?rhs")
hoelzl@41973
  1404
proof-
hoelzl@41973
  1405
{ assume "?rhs"
hoelzl@41973
  1406
  { assume "~((INF i:A. f i) <= x)" hence "x < (INF i:A. f i)" by (simp add: not_le)
wenzelm@47082
  1407
    then obtain y where y_def: "x<y & y<(INF i:A. f i)" using ereal_dense by auto
wenzelm@47082
  1408
    then obtain i where "i : A & f i <= y" using `?rhs` by auto
hoelzl@44928
  1409
    hence "(INF i:A. f i) <= y" using INF_lower[of i A f] by auto
hoelzl@41973
  1410
    hence False using y_def by auto
hoelzl@41973
  1411
  } hence "?lhs" by auto
hoelzl@41973
  1412
}
hoelzl@41973
  1413
moreover
hoelzl@41973
  1414
{ assume "?lhs" hence "?rhs"
bulwahn@45236
  1415
  by (metis INF_less_iff order_le_less order_less_le_trans)
hoelzl@41973
  1416
} ultimately show ?thesis by auto
hoelzl@41973
  1417
qed
hoelzl@41973
  1418
hoelzl@41973
  1419
lemma Inf_less:
hoelzl@43920
  1420
  fixes x :: ereal
hoelzl@41973
  1421
  assumes "(INF i:A. f i) < x"
hoelzl@41973
  1422
  shows "EX i. i : A & f i <= x"
hoelzl@41973
  1423
proof(rule ccontr)
hoelzl@41973
  1424
  assume "~ (EX i. i : A & f i <= x)"
hoelzl@41973
  1425
  hence "ALL i:A. f i > x" by auto
hoelzl@44928
  1426
  hence "(INF i:A. f i) >= x" apply (subst INF_greatest) by auto
hoelzl@41973
  1427
  thus False using assms by auto
hoelzl@41973
  1428
qed
hoelzl@41973
  1429
hoelzl@41973
  1430
lemma same_INF:
hoelzl@41973
  1431
  assumes "ALL e:A. f e = g e"
hoelzl@41973
  1432
  shows "(INF e:A. f e) = (INF e:A. g e)"
hoelzl@41973
  1433
proof-
hoelzl@41973
  1434
have "f ` A = g ` A" unfolding image_def using assms by auto
hoelzl@44928
  1435
thus ?thesis unfolding INF_def by auto
hoelzl@41973
  1436
qed
hoelzl@41973
  1437
hoelzl@41973
  1438
lemma same_SUP:
hoelzl@41973
  1439
  assumes "ALL e:A. f e = g e"
hoelzl@41973
  1440
  shows "(SUP e:A. f e) = (SUP e:A. g e)"
hoelzl@41973
  1441
proof-
hoelzl@41973
  1442
have "f ` A = g ` A" unfolding image_def using assms by auto
hoelzl@44928
  1443
thus ?thesis unfolding SUP_def by auto
hoelzl@41973
  1444
qed
hoelzl@41973
  1445
hoelzl@41979
  1446
lemma SUPR_eq:
hoelzl@41979
  1447
  assumes "\<forall>i\<in>A. \<exists>j\<in>B. f i \<le> g j"
hoelzl@41979
  1448
  assumes "\<forall>j\<in>B. \<exists>i\<in>A. g j \<le> f i"
hoelzl@41979
  1449
  shows "(SUP i:A. f i) = (SUP j:B. g j)"
hoelzl@41979
  1450
proof (intro antisym)
hoelzl@41979
  1451
  show "(SUP i:A. f i) \<le> (SUP j:B. g j)"
hoelzl@44928
  1452
    using assms by (metis SUP_least SUP_upper2)
hoelzl@41979
  1453
  show "(SUP i:B. g i) \<le> (SUP j:A. f j)"
hoelzl@44928
  1454
    using assms by (metis SUP_least SUP_upper2)
hoelzl@41979
  1455
qed
hoelzl@41979
  1456
hoelzl@43920
  1457
lemma SUP_ereal_le_addI:
hoelzl@43923
  1458
  fixes f :: "'i \<Rightarrow> ereal"
hoelzl@41978
  1459
  assumes "\<And>i. f i + y \<le> z" and "y \<noteq> -\<infinity>"
hoelzl@41978
  1460
  shows "SUPR UNIV f + y \<le> z"
hoelzl@41978
  1461
proof (cases y)
hoelzl@41978
  1462
  case (real r)
hoelzl@43920
  1463
  then have "\<And>i. f i \<le> z - y" using assms by (simp add: ereal_le_minus_iff)
hoelzl@44928
  1464
  then have "SUPR UNIV f \<le> z - y" by (rule SUP_least)
hoelzl@43920
  1465
  then show ?thesis using real by (simp add: ereal_le_minus_iff)
hoelzl@41978
  1466
qed (insert assms, auto)
hoelzl@41978
  1467
hoelzl@43920
  1468
lemma SUPR_ereal_add:
hoelzl@43920
  1469
  fixes f g :: "nat \<Rightarrow> ereal"
hoelzl@41979
  1470
  assumes "incseq f" "incseq g" and pos: "\<And>i. f i \<noteq> -\<infinity>" "\<And>i. g i \<noteq> -\<infinity>"
hoelzl@41978
  1471
  shows "(SUP i. f i + g i) = SUPR UNIV f + SUPR UNIV g"
hoelzl@43920
  1472
proof (rule ereal_SUPI)
hoelzl@41978
  1473
  fix y assume *: "\<And>i. i \<in> UNIV \<Longrightarrow> f i + g i \<le> y"
hoelzl@41978
  1474
  have f: "SUPR UNIV f \<noteq> -\<infinity>" using pos
hoelzl@44928
  1475
    unfolding SUP_def Sup_eq_MInfty by (auto dest: image_eqD)
hoelzl@41978
  1476
  { fix j
hoelzl@41978
  1477
    { fix i
hoelzl@41978
  1478
      have "f i + g j \<le> f i + g (max i j)"
hoelzl@41978
  1479
        using `incseq g`[THEN incseqD] by (rule add_left_mono) auto
hoelzl@41978
  1480
      also have "\<dots> \<le> f (max i j) + g (max i j)"
hoelzl@41978
  1481
        using `incseq f`[THEN incseqD] by (rule add_right_mono) auto
hoelzl@41978
  1482
      also have "\<dots> \<le> y" using * by auto
hoelzl@41978
  1483
      finally have "f i + g j \<le> y" . }
hoelzl@41978
  1484
    then have "SUPR UNIV f + g j \<le> y"
hoelzl@43920
  1485
      using assms(4)[of j] by (intro SUP_ereal_le_addI) auto
hoelzl@41978
  1486
    then have "g j + SUPR UNIV f \<le> y" by (simp add: ac_simps) }
hoelzl@41978
  1487
  then have "SUPR UNIV g + SUPR UNIV f \<le> y"
hoelzl@43920
  1488
    using f by (rule SUP_ereal_le_addI)
hoelzl@41978
  1489
  then show "SUPR UNIV f + SUPR UNIV g \<le> y" by (simp add: ac_simps)
hoelzl@44928
  1490
qed (auto intro!: add_mono SUP_upper)
hoelzl@41978
  1491
hoelzl@43920
  1492
lemma SUPR_ereal_add_pos:
hoelzl@43920
  1493
  fixes f g :: "nat \<Rightarrow> ereal"
hoelzl@41979
  1494
  assumes inc: "incseq f" "incseq g" and pos: "\<And>i. 0 \<le> f i" "\<And>i. 0 \<le> g i"
hoelzl@41979
  1495
  shows "(SUP i. f i + g i) = SUPR UNIV f + SUPR UNIV g"
hoelzl@43920
  1496
proof (intro SUPR_ereal_add inc)
hoelzl@41979
  1497
  fix i show "f i \<noteq> -\<infinity>" "g i \<noteq> -\<infinity>" using pos[of i] by auto
hoelzl@41979
  1498
qed
hoelzl@41979
  1499
hoelzl@43920
  1500
lemma SUPR_ereal_setsum:
hoelzl@43920
  1501
  fixes f g :: "'a \<Rightarrow> nat \<Rightarrow> ereal"
hoelzl@41979
  1502
  assumes "\<And>n. n \<in> A \<Longrightarrow> incseq (f n)" and pos: "\<And>n i. n \<in> A \<Longrightarrow> 0 \<le> f n i"
hoelzl@41979
  1503
  shows "(SUP i. \<Sum>n\<in>A. f n i) = (\<Sum>n\<in>A. SUPR UNIV (f n))"
hoelzl@41979
  1504
proof cases
hoelzl@41979
  1505
  assume "finite A" then show ?thesis using assms
hoelzl@43920
  1506
    by induct (auto simp: incseq_setsumI2 setsum_nonneg SUPR_ereal_add_pos)
hoelzl@41979
  1507
qed simp
hoelzl@41979
  1508
hoelzl@43920
  1509
lemma SUPR_ereal_cmult:
hoelzl@43920
  1510
  fixes f :: "nat \<Rightarrow> ereal" assumes "\<And>i. 0 \<le> f i" "0 \<le> c"
hoelzl@41978
  1511
  shows "(SUP i. c * f i) = c * SUPR UNIV f"
hoelzl@43920
  1512
proof (rule ereal_SUPI)
hoelzl@44928
  1513
  fix i have "f i \<le> SUPR UNIV f" by (rule SUP_upper) auto
hoelzl@41978
  1514
  then show "c * f i \<le> c * SUPR UNIV f"
hoelzl@43920
  1515
    using `0 \<le> c` by (rule ereal_mult_left_mono)
hoelzl@41978
  1516
next
hoelzl@41978
  1517
  fix y assume *: "\<And>i. i \<in> UNIV \<Longrightarrow> c * f i \<le> y"
hoelzl@41978
  1518
  show "c * SUPR UNIV f \<le> y"
hoelzl@41978
  1519
  proof cases
hoelzl@41978
  1520
    assume c: "0 < c \<and> c \<noteq> \<infinity>"
hoelzl@41978
  1521
    with * have "SUPR UNIV f \<le> y / c"
hoelzl@44928
  1522
      by (intro SUP_least) (auto simp: ereal_le_divide_pos)
hoelzl@41978
  1523
    with c show ?thesis
hoelzl@43920
  1524
      by (auto simp: ereal_le_divide_pos)
hoelzl@41978
  1525
  next
hoelzl@41978
  1526
    { assume "c = \<infinity>" have ?thesis
hoelzl@41978
  1527
      proof cases
hoelzl@41978
  1528
        assume "\<forall>i. f i = 0"
hoelzl@41978
  1529
        moreover then have "range f = {0}" by auto
noschinl@44918
  1530
        ultimately show "c * SUPR UNIV f \<le> y" using *
hoelzl@44928
  1531
          by (auto simp: SUP_def min_max.sup_absorb1)
hoelzl@41978
  1532
      next
hoelzl@41978
  1533
        assume "\<not> (\<forall>i. f i = 0)"
hoelzl@41978
  1534
        then obtain i where "f i \<noteq> 0" by auto
hoelzl@41978
  1535
        with *[of i] `c = \<infinity>` `0 \<le> f i` show ?thesis by (auto split: split_if_asm)
hoelzl@41978
  1536
      qed }
hoelzl@41978
  1537
    moreover assume "\<not> (0 < c \<and> c \<noteq> \<infinity>)"
hoelzl@41978
  1538
    ultimately show ?thesis using * `0 \<le> c` by auto
hoelzl@41978
  1539
  qed
hoelzl@41978
  1540
qed
hoelzl@41978
  1541
hoelzl@41979
  1542
lemma SUP_PInfty:
hoelzl@43920
  1543
  fixes f :: "'a \<Rightarrow> ereal"
hoelzl@43920
  1544
  assumes "\<And>n::nat. \<exists>i\<in>A. ereal (real n) \<le> f i"
hoelzl@41979
  1545
  shows "(SUP i:A. f i) = \<infinity>"
hoelzl@44928
  1546
  unfolding SUP_def Sup_eq_top_iff[where 'a=ereal, unfolded top_ereal_def]
hoelzl@41979
  1547
  apply simp
hoelzl@41979
  1548
proof safe
hoelzl@43923
  1549
  fix x :: ereal assume "x \<noteq> \<infinity>"
hoelzl@41979
  1550
  show "\<exists>i\<in>A. x < f i"
hoelzl@41979
  1551
  proof (cases x)
hoelzl@41979
  1552
    case PInf with `x \<noteq> \<infinity>` show ?thesis by simp
hoelzl@41979
  1553
  next
hoelzl@41979
  1554
    case MInf with assms[of "0"] show ?thesis by force
hoelzl@41979
  1555
  next
hoelzl@41979
  1556
    case (real r)
hoelzl@43920
  1557
    with less_PInf_Ex_of_nat[of x] obtain n :: nat where "x < ereal (real n)" by auto
hoelzl@41979
  1558
    moreover from assms[of n] guess i ..
hoelzl@41979
  1559
    ultimately show ?thesis
hoelzl@41979
  1560
      by (auto intro!: bexI[of _ i])
hoelzl@41979
  1561
  qed
hoelzl@41979
  1562
qed
hoelzl@41979
  1563
hoelzl@41979
  1564
lemma Sup_countable_SUPR:
hoelzl@41979
  1565
  assumes "A \<noteq> {}"
hoelzl@43920
  1566
  shows "\<exists>f::nat \<Rightarrow> ereal. range f \<subseteq> A \<and> Sup A = SUPR UNIV f"
hoelzl@41979
  1567
proof (cases "Sup A")
hoelzl@41979
  1568
  case (real r)
hoelzl@43920
  1569
  have "\<forall>n::nat. \<exists>x. x \<in> A \<and> Sup A < x + 1 / ereal (real n)"
hoelzl@41979
  1570
  proof
hoelzl@43920
  1571
    fix n ::nat have "\<exists>x\<in>A. Sup A - 1 / ereal (real n) < x"
hoelzl@43920
  1572
      using assms real by (intro Sup_ereal_close) (auto simp: one_ereal_def)
hoelzl@41979
  1573
    then guess x ..
hoelzl@43920
  1574
    then show "\<exists>x. x \<in> A \<and> Sup A < x + 1 / ereal (real n)"
hoelzl@43920
  1575
      by (auto intro!: exI[of _ x] simp: ereal_minus_less_iff)
hoelzl@41979
  1576
  qed
hoelzl@41979
  1577
  from choice[OF this] guess f .. note f = this
hoelzl@41979
  1578
  have "SUPR UNIV f = Sup A"
hoelzl@43920
  1579
  proof (rule ereal_SUPI)
hoelzl@41979
  1580
    fix i show "f i \<le> Sup A" using f
hoelzl@41979
  1581
      by (auto intro!: complete_lattice_class.Sup_upper)
hoelzl@41979
  1582
  next
hoelzl@41979
  1583
    fix y assume bound: "\<And>i. i \<in> UNIV \<Longrightarrow> f i \<le> y"
hoelzl@41979
  1584
    show "Sup A \<le> y"
hoelzl@43920
  1585
    proof (rule ereal_le_epsilon, intro allI impI)
hoelzl@43920
  1586
      fix e :: ereal assume "0 < e"
hoelzl@41979
  1587
      show "Sup A \<le> y + e"
hoelzl@41979
  1588
      proof (cases e)
hoelzl@41979
  1589
        case (real r)
hoelzl@41979
  1590
        hence "0 < r" using `0 < e` by auto
hoelzl@41979
  1591
        then obtain n ::nat where *: "1 / real n < r" "0 < n"
hoelzl@41979
  1592
          using ex_inverse_of_nat_less by (auto simp: real_eq_of_nat inverse_eq_divide)
noschinl@44918
  1593
        have "Sup A \<le> f n + 1 / ereal (real n)" using f[THEN spec, of n]
noschinl@44918
  1594
          by auto
hoelzl@43920
  1595
        also have "1 / ereal (real n) \<le> e" using real * by (auto simp: one_ereal_def )
hoelzl@43920
  1596
        with bound have "f n + 1 / ereal (real n) \<le> y + e" by (rule add_mono) simp
hoelzl@41979
  1597
        finally show "Sup A \<le> y + e" .
hoelzl@41979
  1598
      qed (insert `0 < e`, auto)
hoelzl@41979
  1599
    qed
hoelzl@41979
  1600
  qed
hoelzl@41979
  1601
  with f show ?thesis by (auto intro!: exI[of _ f])
hoelzl@41979
  1602
next
hoelzl@41979
  1603
  case PInf
hoelzl@41979
  1604
  from `A \<noteq> {}` obtain x where "x \<in> A" by auto
hoelzl@41979
  1605
  show ?thesis
hoelzl@41979
  1606
  proof cases
hoelzl@41979
  1607
    assume "\<infinity> \<in> A"
hoelzl@41979
  1608
    moreover then have "\<infinity> \<le> Sup A" by (intro complete_lattice_class.Sup_upper)
hoelzl@41979
  1609
    ultimately show ?thesis by (auto intro!: exI[of _ "\<lambda>x. \<infinity>"])
hoelzl@41979
  1610
  next
hoelzl@41979
  1611
    assume "\<infinity> \<notin> A"
hoelzl@41979
  1612
    have "\<exists>x\<in>A. 0 \<le> x"
hoelzl@43920
  1613
      by (metis Infty_neq_0 PInf complete_lattice_class.Sup_least ereal_infty_less_eq2 linorder_linear)
hoelzl@41979
  1614
    then obtain x where "x \<in> A" "0 \<le> x" by auto
hoelzl@43920
  1615
    have "\<forall>n::nat. \<exists>f. f \<in> A \<and> x + ereal (real n) \<le> f"
hoelzl@41979
  1616
    proof (rule ccontr)
hoelzl@41979
  1617
      assume "\<not> ?thesis"
hoelzl@43920
  1618
      then have "\<exists>n::nat. Sup A \<le> x + ereal (real n)"
hoelzl@41979
  1619
        by (simp add: Sup_le_iff not_le less_imp_le Ball_def) (metis less_imp_le)
hoelzl@41979
  1620
      then show False using `x \<in> A` `\<infinity> \<notin> A` PInf
hoelzl@41979
  1621
        by(cases x) auto
hoelzl@41979
  1622
    qed
hoelzl@41979
  1623
    from choice[OF this] guess f .. note f = this
hoelzl@41979
  1624
    have "SUPR UNIV f = \<infinity>"
hoelzl@41979
  1625
    proof (rule SUP_PInfty)
hoelzl@43920
  1626
      fix n :: nat show "\<exists>i\<in>UNIV. ereal (real n) \<le> f i"
hoelzl@41979
  1627
        using f[THEN spec, of n] `0 \<le> x`
hoelzl@43920
  1628
        by (cases rule: ereal2_cases[of "f n" x]) (auto intro!: exI[of _ n])
hoelzl@41979
  1629
    qed
hoelzl@41979
  1630
    then show ?thesis using f PInf by (auto intro!: exI[of _ f])
hoelzl@41979
  1631
  qed
hoelzl@41979
  1632
next
hoelzl@41979
  1633
  case MInf
hoelzl@41979
  1634
  with `A \<noteq> {}` have "A = {-\<infinity>}" by (auto simp: Sup_eq_MInfty)
hoelzl@41979
  1635
  then show ?thesis using MInf by (auto intro!: exI[of _ "\<lambda>x. -\<infinity>"])
hoelzl@41979
  1636
qed
hoelzl@41979
  1637
hoelzl@41979
  1638
lemma SUPR_countable_SUPR:
hoelzl@43920
  1639
  "A \<noteq> {} \<Longrightarrow> \<exists>f::nat \<Rightarrow> ereal. range f \<subseteq> g`A \<and> SUPR A g = SUPR UNIV f"
hoelzl@44928
  1640
  using Sup_countable_SUPR[of "g`A"] by (auto simp: SUP_def)
hoelzl@41979
  1641
hoelzl@43920
  1642
lemma Sup_ereal_cadd:
hoelzl@43920
  1643
  fixes A :: "ereal set" assumes "A \<noteq> {}" and "a \<noteq> -\<infinity>"
hoelzl@41979
  1644
  shows "Sup ((\<lambda>x. a + x) ` A) = a + Sup A"
hoelzl@41979
  1645
proof (rule antisym)
hoelzl@43920
  1646
  have *: "\<And>a::ereal. \<And>A. Sup ((\<lambda>x. a + x) ` A) \<le> a + Sup A"
hoelzl@41979
  1647
    by (auto intro!: add_mono complete_lattice_class.Sup_least complete_lattice_class.Sup_upper)
hoelzl@41979
  1648
  then show "Sup ((\<lambda>x. a + x) ` A) \<le> a + Sup A" .
hoelzl@41979
  1649
  show "a + Sup A \<le> Sup ((\<lambda>x. a + x) ` A)"
hoelzl@41979
  1650
  proof (cases a)
noschinl@44918
  1651
    case PInf with `A \<noteq> {}` show ?thesis by (auto simp: image_constant min_max.sup_absorb1)
hoelzl@41979
  1652
  next
hoelzl@41979
  1653
    case (real r)
hoelzl@41979
  1654
    then have **: "op + (- a) ` op + a ` A = A"
hoelzl@43920
  1655
      by (auto simp: image_iff ac_simps zero_ereal_def[symmetric])
hoelzl@41979
  1656
    from *[of "-a" "(\<lambda>x. a + x) ` A"] real show ?thesis unfolding **
hoelzl@43920
  1657
      by (cases rule: ereal2_cases[of "Sup A" "Sup (op + a ` A)"]) auto
hoelzl@41979
  1658
  qed (insert `a \<noteq> -\<infinity>`, auto)
hoelzl@41979
  1659
qed
hoelzl@41979
  1660
hoelzl@43920
  1661
lemma Sup_ereal_cminus:
hoelzl@43920
  1662
  fixes A :: "ereal set" assumes "A \<noteq> {}" and "a \<noteq> -\<infinity>"
hoelzl@41979
  1663
  shows "Sup ((\<lambda>x. a - x) ` A) = a - Inf A"
hoelzl@43920
  1664
  using Sup_ereal_cadd[of "uminus ` A" a] assms
hoelzl@43920
  1665
  by (simp add: comp_def image_image minus_ereal_def
hoelzl@43920
  1666
                 ereal_Sup_uminus_image_eq)
hoelzl@41979
  1667
hoelzl@43920
  1668
lemma SUPR_ereal_cminus:
hoelzl@43923
  1669
  fixes f :: "'i \<Rightarrow> ereal"
hoelzl@41979
  1670
  fixes A assumes "A \<noteq> {}" and "a \<noteq> -\<infinity>"
hoelzl@41979
  1671
  shows "(SUP x:A. a - f x) = a - (INF x:A. f x)"
hoelzl@43920
  1672
  using Sup_ereal_cminus[of "f`A" a] assms
hoelzl@44928
  1673
  unfolding SUP_def INF_def image_image by auto
hoelzl@41979
  1674
hoelzl@43920
  1675
lemma Inf_ereal_cminus:
hoelzl@43920
  1676
  fixes A :: "ereal set" assumes "A \<noteq> {}" and "\<bar>a\<bar> \<noteq> \<infinity>"
hoelzl@41979
  1677
  shows "Inf ((\<lambda>x. a - x) ` A) = a - Sup A"
hoelzl@41979
  1678
proof -
hoelzl@41979
  1679
  { fix x have "-a - -x = -(a - x)" using assms by (cases x) auto }
hoelzl@41979
  1680
  moreover then have "(\<lambda>x. -a - x)`uminus`A = uminus ` (\<lambda>x. a - x) ` A"
hoelzl@41979
  1681
    by (auto simp: image_image)
hoelzl@41979
  1682
  ultimately show ?thesis
hoelzl@43920
  1683
    using Sup_ereal_cminus[of "uminus ` A" "-a"] assms
hoelzl@43920
  1684
    by (auto simp add: ereal_Sup_uminus_image_eq ereal_Inf_uminus_image_eq)
hoelzl@41979
  1685
qed
hoelzl@41979
  1686
hoelzl@43920
  1687
lemma INFI_ereal_cminus:
hoelzl@43923
  1688
  fixes a :: ereal assumes "A \<noteq> {}" and "\<bar>a\<bar> \<noteq> \<infinity>"
hoelzl@41979
  1689
  shows "(INF x:A. a - f x) = a - (SUP x:A. f x)"
hoelzl@43920
  1690
  using Inf_ereal_cminus[of "f`A" a] assms
hoelzl@44928
  1691
  unfolding SUP_def INF_def image_image
hoelzl@41979
  1692
  by auto
hoelzl@41979
  1693
hoelzl@43920
  1694
lemma uminus_ereal_add_uminus_uminus:
hoelzl@43920
  1695
  fixes a b :: ereal shows "a \<noteq> \<infinity> \<Longrightarrow> b \<noteq> \<infinity> \<Longrightarrow> - (- a + - b) = a + b"
hoelzl@43920
  1696
  by (cases rule: ereal2_cases[of a b]) auto
hoelzl@42950
  1697
hoelzl@43920
  1698
lemma INFI_ereal_add:
hoelzl@43923
  1699
  fixes f :: "nat \<Rightarrow> ereal"
hoelzl@42950
  1700
  assumes "decseq f" "decseq g" and fin: "\<And>i. f i \<noteq> \<infinity>" "\<And>i. g i \<noteq> \<infinity>"
hoelzl@42950
  1701
  shows "(INF i. f i + g i) = INFI UNIV f + INFI UNIV g"
hoelzl@42950
  1702
proof -
hoelzl@42950
  1703
  have INF_less: "(INF i. f i) < \<infinity>" "(INF i. g i) < \<infinity>"
hoelzl@42950
  1704
    using assms unfolding INF_less_iff by auto
hoelzl@42950
  1705
  { fix i from fin[of i] have "- ((- f i) + (- g i)) = f i + g i"
hoelzl@43920
  1706
      by (rule uminus_ereal_add_uminus_uminus) }
hoelzl@42950
  1707
  then have "(INF i. f i + g i) = (INF i. - ((- f i) + (- g i)))"
hoelzl@42950
  1708
    by simp
hoelzl@42950
  1709
  also have "\<dots> = INFI UNIV f + INFI UNIV g"
hoelzl@43920
  1710
    unfolding ereal_INFI_uminus
hoelzl@42950
  1711
    using assms INF_less
hoelzl@43920
  1712
    by (subst SUPR_ereal_add)
hoelzl@43920
  1713
       (auto simp: ereal_SUPR_uminus intro!: uminus_ereal_add_uminus_uminus)
hoelzl@42950
  1714
  finally show ?thesis .
hoelzl@42950
  1715
qed
hoelzl@42950
  1716
noschinl@45934
  1717
subsection "Relation to @{typ enat}"
noschinl@45934
  1718
noschinl@45934
  1719
definition "ereal_of_enat n = (case n of enat n \<Rightarrow> ereal (real n) | \<infinity> \<Rightarrow> \<infinity>)"
noschinl@45934
  1720
noschinl@45934
  1721
declare [[coercion "ereal_of_enat :: enat \<Rightarrow> ereal"]]
noschinl@45934
  1722
declare [[coercion "(\<lambda>n. ereal (real n)) :: nat \<Rightarrow> ereal"]]
noschinl@45934
  1723
noschinl@45934
  1724
lemma ereal_of_enat_simps[simp]:
noschinl@45934
  1725
  "ereal_of_enat (enat n) = ereal n"
noschinl@45934
  1726
  "ereal_of_enat \<infinity> = \<infinity>"
noschinl@45934
  1727
  by (simp_all add: ereal_of_enat_def)
noschinl@45934
  1728
noschinl@45934
  1729
lemma ereal_of_enat_le_iff[simp]:
noschinl@45934
  1730
  "ereal_of_enat m \<le> ereal_of_enat n \<longleftrightarrow> m \<le> n"
noschinl@45934
  1731
by (cases m n rule: enat2_cases) auto
noschinl@45934
  1732
noschinl@45934
  1733
lemma number_of_le_ereal_of_enat_iff[simp]:
noschinl@45934
  1734
  shows "number_of m \<le> ereal_of_enat n \<longleftrightarrow> number_of m \<le> n"
noschinl@45934
  1735
by (cases n) (auto dest: natceiling_le intro: natceiling_le_eq[THEN iffD1])
noschinl@45934
  1736
noschinl@45934
  1737
lemma ereal_of_enat_ge_zero_cancel_iff[simp]:
noschinl@45934
  1738
  "0 \<le> ereal_of_enat n \<longleftrightarrow> 0 \<le> n"
noschinl@45934
  1739
by (cases n) (auto simp: enat_0[symmetric])
noschinl@45934
  1740
noschinl@45934
  1741
lemma ereal_of_enat_gt_zero_cancel_iff[simp]:
noschinl@45934
  1742
  "0 < ereal_of_enat n \<longleftrightarrow> 0 < n"
noschinl@45934
  1743
by (cases n) (auto simp: enat_0[symmetric])
noschinl@45934
  1744
noschinl@45934
  1745
lemma ereal_of_enat_zero[simp]:
noschinl@45934
  1746
  "ereal_of_enat 0 = 0"
noschinl@45934
  1747
by (auto simp: enat_0[symmetric])
noschinl@45934
  1748
noschinl@45934
  1749
lemma ereal_of_enat_add:
noschinl@45934
  1750
  "ereal_of_enat (m + n) = ereal_of_enat m + ereal_of_enat n"
noschinl@45934
  1751
by (cases m n rule: enat2_cases) auto
noschinl@45934
  1752
noschinl@45934
  1753
lemma ereal_of_enat_sub:
noschinl@45934
  1754
  assumes "n \<le> m" shows "ereal_of_enat (m - n) = ereal_of_enat m - ereal_of_enat n "
noschinl@45934
  1755
using assms by (cases m n rule: enat2_cases) auto
noschinl@45934
  1756
noschinl@45934
  1757
lemma ereal_of_enat_mult:
noschinl@45934
  1758
  "ereal_of_enat (m * n) = ereal_of_enat m * ereal_of_enat n"
noschinl@45934
  1759
by (cases m n rule: enat2_cases) auto
noschinl@45934
  1760
noschinl@45934
  1761
lemmas ereal_of_enat_pushin = ereal_of_enat_add ereal_of_enat_sub ereal_of_enat_mult
noschinl@45934
  1762
lemmas ereal_of_enat_pushout = ereal_of_enat_pushin[symmetric]
noschinl@45934
  1763
noschinl@45934
  1764
hoelzl@43920
  1765
subsection "Limits on @{typ ereal}"
hoelzl@41973
  1766
hoelzl@41973
  1767
subsubsection "Topological space"
hoelzl@41973
  1768
hoelzl@43920
  1769
instantiation ereal :: topological_space
hoelzl@41973
  1770
begin
hoelzl@41973
  1771
hoelzl@43920
  1772
definition "open A \<longleftrightarrow> open (ereal -` A)
hoelzl@43920
  1773
       \<and> (\<infinity> \<in> A \<longrightarrow> (\<exists>x. {ereal x <..} \<subseteq> A))
hoelzl@43920
  1774
       \<and> (-\<infinity> \<in> A \<longrightarrow> (\<exists>x. {..<ereal x} \<subseteq> A))"
hoelzl@41973
  1775
hoelzl@43920
  1776
lemma open_PInfty: "open A \<Longrightarrow> \<infinity> \<in> A \<Longrightarrow> (\<exists>x. {ereal x<..} \<subseteq> A)"
hoelzl@43920
  1777
  unfolding open_ereal_def by auto
hoelzl@41973
  1778
hoelzl@43920
  1779
lemma open_MInfty: "open A \<Longrightarrow> -\<infinity> \<in> A \<Longrightarrow> (\<exists>x. {..<ereal x} \<subseteq> A)"
hoelzl@43920
  1780
  unfolding open_ereal_def by auto
hoelzl@41973
  1781
hoelzl@43920
  1782
lemma open_PInfty2: assumes "open A" "\<infinity> \<in> A" obtains x where "{ereal x<..} \<subseteq> A"
hoelzl@41973
  1783
  using open_PInfty[OF assms] by auto
hoelzl@41973
  1784
hoelzl@43920
  1785
lemma open_MInfty2: assumes "open A" "-\<infinity> \<in> A" obtains x where "{..<ereal x} \<subseteq> A"
hoelzl@41973
  1786
  using open_MInfty[OF assms] by auto
hoelzl@41973
  1787
hoelzl@43920
  1788
lemma ereal_openE: assumes "open A" obtains x y where
hoelzl@43920
  1789
  "open (ereal -` A)"
hoelzl@43920
  1790
  "\<infinity> \<in> A \<Longrightarrow> {ereal x<..} \<subseteq> A"
hoelzl@43920
  1791
  "-\<infinity> \<in> A \<Longrightarrow> {..<ereal y} \<subseteq> A"
hoelzl@43920
  1792
  using assms open_ereal_def by auto
hoelzl@41973
  1793
hoelzl@41973
  1794
instance
hoelzl@41973
  1795
proof
hoelzl@43920
  1796
  let ?U = "UNIV::ereal set"
hoelzl@43920
  1797
  show "open ?U" unfolding open_ereal_def
hoelzl@41975
  1798
    by (auto intro!: exI[of _ 0])
hoelzl@41973
  1799
next
hoelzl@43920
  1800
  fix S T::"ereal set" assume "open S" and "open T"
hoelzl@43920
  1801
  from `open S`[THEN ereal_openE] guess xS yS .
hoelzl@43920
  1802
  moreover from `open T`[THEN ereal_openE] guess xT yT .
hoelzl@41975
  1803
  ultimately have
hoelzl@43920
  1804
    "open (ereal -` (S \<inter> T))"
hoelzl@43920
  1805
    "\<infinity> \<in> S \<inter> T \<Longrightarrow> {ereal (max xS xT) <..} \<subseteq> S \<inter> T"
hoelzl@43920
  1806
    "-\<infinity> \<in> S \<inter> T \<Longrightarrow> {..< ereal (min yS yT)} \<subseteq> S \<inter> T"
hoelzl@41975
  1807
    by auto
hoelzl@43920
  1808
  then show "open (S Int T)" unfolding open_ereal_def by blast
hoelzl@41973
  1809
next
hoelzl@43920
  1810
  fix K :: "ereal set set" assume "\<forall>S\<in>K. open S"
hoelzl@43920
  1811
  then have *: "\<forall>S. \<exists>x y. S \<in> K \<longrightarrow> open (ereal -` S) \<and>
hoelzl@43920
  1812
    (\<infinity> \<in> S \<longrightarrow> {ereal x <..} \<subseteq> S) \<and> (-\<infinity> \<in> S \<longrightarrow> {..< ereal y} \<subseteq> S)"
hoelzl@43920
  1813
    by (auto simp: open_ereal_def)
hoelzl@43920
  1814
  then show "open (Union K)" unfolding open_ereal_def
hoelzl@41975
  1815
  proof (intro conjI impI)
hoelzl@43920
  1816
    show "open (ereal -` \<Union>K)"
hoelzl@41980
  1817
      using *[THEN choice] by (auto simp: vimage_Union)
hoelzl@41975
  1818
  qed ((metis UnionE Union_upper subset_trans *)+)
hoelzl@41973
  1819
qed
hoelzl@41973
  1820
end
hoelzl@41973
  1821
hoelzl@43920
  1822
lemma open_ereal: "open S \<Longrightarrow> open (ereal ` S)"
hoelzl@43920
  1823
  by (auto simp: inj_vimage_image_eq open_ereal_def)
hoelzl@41976
  1824
hoelzl@43920
  1825
lemma open_ereal_vimage: "open S \<Longrightarrow> open (ereal -` S)"
hoelzl@43920
  1826
  unfolding open_ereal_def by auto
hoelzl@41976
  1827
hoelzl@43920
  1828
lemma open_ereal_lessThan[intro, simp]: "open {..< a :: ereal}"
hoelzl@41975
  1829
proof -
hoelzl@43920
  1830
  have "\<And>x. ereal -` {..<ereal x} = {..< x}"
hoelzl@43920
  1831
    "ereal -` {..< \<infinity>} = UNIV" "ereal -` {..< -\<infinity>} = {}" by auto
hoelzl@43920
  1832
  then show ?thesis by (cases a) (auto simp: open_ereal_def)
hoelzl@41975
  1833
qed
hoelzl@41975
  1834
hoelzl@43920
  1835
lemma open_ereal_greaterThan[intro, simp]:
hoelzl@43920
  1836
  "open {a :: ereal <..}"
hoelzl@41975
  1837
proof -
hoelzl@43920
  1838
  have "\<And>x. ereal -` {ereal x<..} = {x<..}"
hoelzl@43920
  1839
    "ereal -` {\<infinity><..} = {}" "ereal -` {-\<infinity><..} = UNIV" by auto
hoelzl@43920
  1840
  then show ?thesis by (cases a) (auto simp: open_ereal_def)
hoelzl@41975
  1841
qed
hoelzl@41975
  1842
hoelzl@43920
  1843
lemma ereal_open_greaterThanLessThan[intro, simp]: "open {a::ereal <..< b}"
hoelzl@41973
  1844
  unfolding greaterThanLessThan_def by auto
hoelzl@41973
  1845
hoelzl@43920
  1846
lemma closed_ereal_atLeast[simp, intro]: "closed {a :: ereal ..}"
hoelzl@41973
  1847
proof -
hoelzl@41973
  1848
  have "- {a ..} = {..< a}" by auto
hoelzl@41973
  1849
  then show "closed {a ..}"
hoelzl@43920
  1850
    unfolding closed_def using open_ereal_lessThan by auto
hoelzl@41973
  1851
qed
hoelzl@41973
  1852
hoelzl@43920
  1853
lemma closed_ereal_atMost[simp, intro]: "closed {.. b :: ereal}"
hoelzl@41973
  1854
proof -
hoelzl@41973
  1855
  have "- {.. b} = {b <..}" by auto
hoelzl@41973
  1856
  then show "closed {.. b}"
hoelzl@43920
  1857
    unfolding closed_def using open_ereal_greaterThan by auto
hoelzl@41973
  1858
qed
hoelzl@41973
  1859
hoelzl@43920
  1860
lemma closed_ereal_atLeastAtMost[simp, intro]:
hoelzl@43920
  1861
  shows "closed {a :: ereal .. b}"
hoelzl@41973
  1862
  unfolding atLeastAtMost_def by auto
hoelzl@41973
  1863
hoelzl@43920
  1864
lemma closed_ereal_singleton:
hoelzl@43920
  1865
  "closed {a :: ereal}"
hoelzl@43920
  1866
by (metis atLeastAtMost_singleton closed_ereal_atLeastAtMost)
hoelzl@41973
  1867
hoelzl@43920
  1868
lemma ereal_open_cont_interval:
hoelzl@43923
  1869
  fixes S :: "ereal set"
hoelzl@41976
  1870
  assumes "open S" "x \<in> S" "\<bar>x\<bar> \<noteq> \<infinity>"
hoelzl@41973
  1871
  obtains e where "e>0" "{x-e <..< x+e} \<subseteq> S"
hoelzl@41973
  1872
proof-
hoelzl@43920
  1873
  from `open S` have "open (ereal -` S)" by (rule ereal_openE)
hoelzl@43920
  1874
  then obtain e where "0 < e" and e: "\<And>y. dist y (real x) < e \<Longrightarrow> ereal y \<in> S"
hoelzl@41980
  1875
    using assms unfolding open_dist by force
hoelzl@41975
  1876
  show thesis
hoelzl@41975
  1877
  proof (intro that subsetI)
hoelzl@43920
  1878
    show "0 < ereal e" using `0 < e` by auto
hoelzl@43920
  1879
    fix y assume "y \<in> {x - ereal e<..<x + ereal e}"
hoelzl@43920
  1880
    with assms obtain t where "y = ereal t" "dist t (real x) < e"
hoelzl@41980
  1881
      apply (cases y) by (auto simp: dist_real_def)
hoelzl@41980
  1882
    then show "y \<in> S" using e[of t] by auto
hoelzl@41975
  1883
  qed
hoelzl@41973
  1884
qed
hoelzl@41973
  1885
hoelzl@43920
  1886
lemma ereal_open_cont_interval2:
hoelzl@43923
  1887
  fixes S :: "ereal set"
hoelzl@41976
  1888
  assumes "open S" "x \<in> S" and x: "\<bar>x\<bar> \<noteq> \<infinity>"
hoelzl@41973
  1889
  obtains a b where "a < x" "x < b" "{a <..< b} \<subseteq> S"
hoelzl@41973
  1890
proof-
hoelzl@43920
  1891
  guess e using ereal_open_cont_interval[OF assms] .
hoelzl@43920
  1892
  with that[of "x-e" "x+e"] ereal_between[OF x, of e]
hoelzl@41973
  1893
  show thesis by auto
hoelzl@41973
  1894
qed
hoelzl@41973
  1895
hoelzl@43920
  1896
instance ereal :: t2_space
hoelzl@41973
  1897
proof
hoelzl@43920
  1898
  fix x y :: ereal assume "x ~= y"
hoelzl@43920
  1899
  let "?P x (y::ereal)" = "EX U V. open U & open V & x : U & y : V & U Int V = {}"
hoelzl@41973
  1900
hoelzl@43920
  1901
  { fix x y :: ereal assume "x < y"
hoelzl@43920
  1902
    from ereal_dense[OF this] obtain z where z: "x < z" "z < y" by auto
hoelzl@41973
  1903
    have "?P x y"
hoelzl@41973
  1904
      apply (rule exI[of _ "{..<z}"])
hoelzl@41973
  1905
      apply (rule exI[of _ "{z<..}"])
hoelzl@41973
  1906
      using z by auto }
hoelzl@41973
  1907
  note * = this
hoelzl@41973
  1908
hoelzl@41973
  1909
  from `x ~= y`
hoelzl@41973
  1910
  show "EX U V. open U & open V & x : U & y : V & U Int V = {}"
hoelzl@41973
  1911
  proof (cases rule: linorder_cases)
hoelzl@41973
  1912
    assume "x = y" with `x ~= y` show ?thesis by simp
hoelzl@41973
  1913
  next assume "x < y" from *[OF this] show ?thesis by auto
hoelzl@41973
  1914
  next assume "y < x" from *[OF this] show ?thesis by auto
hoelzl@41973
  1915
  qed
hoelzl@41973
  1916
qed
hoelzl@41973
  1917
hoelzl@41973
  1918
subsubsection {* Convergent sequences *}
hoelzl@41973
  1919
hoelzl@43920
  1920
lemma lim_ereal[simp]:
hoelzl@43920
  1921
  "((\<lambda>n. ereal (f n)) ---> ereal x) net \<longleftrightarrow> (f ---> x) net" (is "?l = ?r")
hoelzl@41973
  1922
proof (intro iffI topological_tendstoI)
hoelzl@41973
  1923
  fix S assume "?l" "open S" "x \<in> S"
hoelzl@41973
  1924
  then show "eventually (\<lambda>x. f x \<in> S) net"
hoelzl@43920
  1925
    using `?l`[THEN topological_tendstoD, OF open_ereal, OF `open S`]
hoelzl@41973
  1926
    by (simp add: inj_image_mem_iff)
hoelzl@41973
  1927
next
hoelzl@43920
  1928
  fix S assume "?r" "open S" "ereal x \<in> S"
hoelzl@43920
  1929
  show "eventually (\<lambda>x. ereal (f x) \<in> S) net"
hoelzl@43920
  1930
    using `?r`[THEN topological_tendstoD, OF open_ereal_vimage, OF `open S`]
hoelzl@43920
  1931
    using `ereal x \<in> S` by auto
hoelzl@41973
  1932
qed
hoelzl@41973
  1933
hoelzl@43920
  1934
lemma lim_real_of_ereal[simp]:
hoelzl@43920
  1935
  assumes lim: "(f ---> ereal x) net"
hoelzl@41973
  1936
  shows "((\<lambda>x. real (f x)) ---> x) net"
hoelzl@41973
  1937
proof (intro topological_tendstoI)
hoelzl@41973
  1938
  fix S assume "open S" "x \<in> S"
hoelzl@43920
  1939
  then have S: "open S" "ereal x \<in> ereal ` S"
hoelzl@41973
  1940
    by (simp_all add: inj_image_mem_iff)
hoelzl@43920
  1941
  have "\<forall>x. f x \<in> ereal ` S \<longrightarrow> real (f x) \<in> S" by auto
hoelzl@43920
  1942
  from this lim[THEN topological_tendstoD, OF open_ereal, OF S]
hoelzl@41973
  1943
  show "eventually (\<lambda>x. real (f x) \<in> S) net"
hoelzl@41973
  1944
    by (rule eventually_mono)
hoelzl@41973
  1945
qed
hoelzl@41973
  1946
hoelzl@43920
  1947
lemma Lim_PInfty: "f ----> \<infinity> <-> (ALL B. EX N. ALL n>=N. f n >= ereal B)" (is "?l = ?r")
hoelzl@43923
  1948
proof
hoelzl@43923
  1949
  assume ?r
hoelzl@43923
  1950
  show ?l
hoelzl@43923
  1951
    apply(rule topological_tendstoI)
hoelzl@41973
  1952
    unfolding eventually_sequentially
hoelzl@43923
  1953
  proof-
hoelzl@43923
  1954
    fix S :: "ereal set" assume "open S" "\<infinity> : S"
hoelzl@41973
  1955
    from open_PInfty[OF this] guess B .. note B=this
hoelzl@41973
  1956
    from `?r`[rule_format,of "B+1"] guess N .. note N=this
hoelzl@41973
  1957
    show "EX N. ALL n>=N. f n : S" apply(rule_tac x=N in exI)
hoelzl@41973
  1958
    proof safe case goal1
hoelzl@43920
  1959
      have "ereal B < ereal (B + 1)" by auto
hoelzl@41973
  1960
      also have "... <= f n" using goal1 N by auto
nipkow@44890
  1961
      finally show ?case using B by fastforce
hoelzl@41973
  1962
    qed
hoelzl@41973
  1963
  qed
hoelzl@43923
  1964
next
hoelzl@43923
  1965
  assume ?l
hoelzl@43923
  1966
  show ?r
hoelzl@43920
  1967
  proof fix B::real have "open {ereal B<..}" "\<infinity> : {ereal B<..}" by auto
hoelzl@41973
  1968
    from topological_tendstoD[OF `?l` this,unfolded eventually_sequentially]
hoelzl@41973
  1969
    guess N .. note N=this
hoelzl@43920
  1970
    show "EX N. ALL n>=N. ereal B <= f n" apply(rule_tac x=N in exI) using N by auto
hoelzl@41973
  1971
  qed
hoelzl@41973
  1972
qed
hoelzl@41973
  1973
hoelzl@41973
  1974
hoelzl@43920
  1975
lemma Lim_MInfty: "f ----> (-\<infinity>) <-> (ALL B. EX N. ALL n>=N. f n <= ereal B)" (is "?l = ?r")
hoelzl@43923
  1976
proof
hoelzl@43923
  1977
  assume ?r
hoelzl@43923
  1978
  show ?l
hoelzl@43923
  1979
    apply(rule topological_tendstoI)
hoelzl@41973
  1980
    unfolding eventually_sequentially
hoelzl@43923
  1981
  proof-
hoelzl@43923
  1982
    fix S :: "ereal set"
hoelzl@43923
  1983
    assume "open S" "(-\<infinity>) : S"
hoelzl@41973
  1984
    from open_MInfty[OF this] guess B .. note B=this
hoelzl@41973
  1985
    from `?r`[rule_format,of "B-(1::real)"] guess N .. note N=this
hoelzl@41973
  1986
    show "EX N. ALL n>=N. f n : S" apply(rule_tac x=N in exI)
hoelzl@41973
  1987
    proof safe case goal1
hoelzl@43920
  1988
      have "ereal (B - 1) >= f n" using goal1 N by auto
hoelzl@43920
  1989
      also have "... < ereal B" by auto
nipkow@44890
  1990
      finally show ?case using B by fastforce
hoelzl@41973
  1991
    qed
hoelzl@41973
  1992
  qed
hoelzl@41973
  1993
next assume ?l show ?r
hoelzl@43920
  1994
  proof fix B::real have "open {..<ereal B}" "(-\<infinity>) : {..<ereal B}" by auto
hoelzl@41973
  1995
    from topological_tendstoD[OF `?l` this,unfolded eventually_sequentially]
hoelzl@41973
  1996
    guess N .. note N=this
hoelzl@43920
  1997
    show "EX N. ALL n>=N. ereal B >= f n" apply(rule_tac x=N in exI) using N by auto
hoelzl@41973
  1998
  qed
hoelzl@41973
  1999
qed
hoelzl@41973
  2000
hoelzl@41973
  2001
hoelzl@43920
  2002
lemma Lim_bounded_PInfty: assumes lim:"f ----> l" and "!!n. f n <= ereal B" shows "l ~= \<infinity>"
hoelzl@41973
  2003
proof(rule ccontr,unfold not_not) let ?B = "B + 1" assume as:"l=\<infinity>"
hoelzl@41973
  2004
  from lim[unfolded this Lim_PInfty,rule_format,of "?B"]
hoelzl@41973
  2005
  guess N .. note N=this[rule_format,OF le_refl]
hoelzl@43920
  2006
  hence "ereal ?B <= ereal B" using assms(2)[of N] by(rule order_trans)
hoelzl@43920
  2007
  hence "ereal ?B < ereal ?B" apply (rule le_less_trans) by auto
hoelzl@41973
  2008
  thus False by auto
hoelzl@41973
  2009
qed
hoelzl@41973
  2010
hoelzl@41973
  2011
hoelzl@43920
  2012
lemma Lim_bounded_MInfty: assumes lim:"f ----> l" and "!!n. f n >= ereal B" shows "l ~= (-\<infinity>)"
hoelzl@41973
  2013
proof(rule ccontr,unfold not_not) let ?B = "B - 1" assume as:"l=(-\<infinity>)"
hoelzl@41973
  2014
  from lim[unfolded this Lim_MInfty,rule_format,of "?B"]
hoelzl@41973
  2015
  guess N .. note N=this[rule_format,OF le_refl]
hoelzl@43920
  2016
  hence "ereal B <= ereal ?B" using assms(2)[of N] order_trans[of "ereal B" "f N" "ereal(B - 1)"] by blast
hoelzl@41973
  2017
  thus False by auto
hoelzl@41973
  2018
qed
hoelzl@41973
  2019
hoelzl@41973
  2020
hoelzl@41973
  2021
lemma tendsto_explicit:
hoelzl@41973
  2022
  "f ----> f0 <-> (ALL S. open S --> f0 : S --> (EX N. ALL n>=N. f n : S))"
hoelzl@41973
  2023
  unfolding tendsto_def eventually_sequentially by auto
hoelzl@41973
  2024
hoelzl@41973
  2025
hoelzl@41973
  2026
lemma tendsto_obtains_N:
hoelzl@41973
  2027
  assumes "f ----> f0"
hoelzl@41973
  2028
  assumes "open S" "f0 : S"
hoelzl@41973
  2029
  obtains N where "ALL n>=N. f n : S"
hoelzl@41973
  2030
  using tendsto_explicit[of f f0] assms by auto
hoelzl@41973
  2031
hoelzl@41973
  2032
hoelzl@41973
  2033
lemma tail_same_limit:
hoelzl@41973
  2034
  fixes X Y N
hoelzl@41973
  2035
  assumes "X ----> L" "ALL n>=N. X n = Y n"
hoelzl@41973
  2036
  shows "Y ----> L"
hoelzl@41973
  2037
proof-
hoelzl@41973
  2038
{ fix S assume "open S" and "L:S"
wenzelm@47082
  2039
  then obtain N1 where "ALL n>=N1. X n : S"
hoelzl@41973
  2040
     using assms unfolding tendsto_def eventually_sequentially by auto
hoelzl@41973
  2041
  hence "ALL n>=max N N1. Y n : S" using assms by auto
hoelzl@41973
  2042
  hence "EX N. ALL n>=N. Y n : S" apply(rule_tac x="max N N1" in exI) by auto
hoelzl@41973
  2043
}
hoelzl@41973
  2044
thus ?thesis using tendsto_explicit by auto
hoelzl@41973
  2045
qed
hoelzl@41973
  2046
hoelzl@41973
  2047
hoelzl@41973
  2048
lemma Lim_bounded_PInfty2:
hoelzl@43920
  2049
assumes lim:"f ----> l" and "ALL n>=N. f n <= ereal B"
hoelzl@41973
  2050
shows "l ~= \<infinity>"
hoelzl@41973
  2051
proof-
hoelzl@43920
  2052
  def g == "(%n. if n>=N then f n else ereal B)"
hoelzl@41973
  2053
  hence "g ----> l" using tail_same_limit[of f l N g] lim by auto
hoelzl@43920
  2054
  moreover have "!!n. g n <= ereal B" using g_def assms by auto
hoelzl@41973
  2055
  ultimately show ?thesis using  Lim_bounded_PInfty by auto
hoelzl@41973
  2056
qed
hoelzl@41973
  2057
hoelzl@43920
  2058
lemma Lim_bounded_ereal:
hoelzl@43920
  2059
  assumes lim:"f ----> (l :: ereal)"
hoelzl@41973
  2060
  and "ALL n>=M. f n <= C"
hoelzl@41973
  2061
  shows "l<=C"
hoelzl@41973
  2062
proof-
hoelzl@41973
  2063
{ assume "l=(-\<infinity>)" hence ?thesis by auto }
hoelzl@41973
  2064
moreover
hoelzl@41973
  2065
{ assume "~(l=(-\<infinity>))"
hoelzl@41973
  2066
  { assume "C=\<infinity>" hence ?thesis by auto }
hoelzl@41973
  2067
  moreover
hoelzl@41973
  2068
  { assume "C=(-\<infinity>)" hence "ALL n>=M. f n = (-\<infinity>)" using assms by auto
hoelzl@41973
  2069
    hence "l=(-\<infinity>)" using assms
hoelzl@41980
  2070
       tendsto_unique[OF trivial_limit_sequentially] tail_same_limit[of "\<lambda>n. -\<infinity>" "-\<infinity>" M f, OF tendsto_const] by auto
hoelzl@41973
  2071
    hence ?thesis by auto }
hoelzl@41973
  2072
  moreover
hoelzl@43920
  2073
  { assume "EX B. C = ereal B"
wenzelm@47082
  2074
    then obtain B where B_def: "C=ereal B" by auto
hoelzl@41973
  2075
    hence "~(l=\<infinity>)" using Lim_bounded_PInfty2 assms by auto
wenzelm@47082
  2076
    then obtain m where m_def: "ereal m=l" using `~(l=(-\<infinity>))` by (cases l) auto
wenzelm@47082
  2077
    then obtain N where N_def: "ALL n>=N. f n : {ereal(m - 1) <..< ereal(m+1)}"
hoelzl@43920
  2078
       apply (subst tendsto_obtains_N[of f l "{ereal(m - 1) <..< ereal(m+1)}"]) using assms by auto
hoelzl@41973
  2079
    { fix n assume "n>=N"
hoelzl@43920
  2080
      hence "EX r. ereal r = f n" using N_def by (cases "f n") auto
wenzelm@47082
  2081
    } then obtain g where g_def: "ALL n>=N. ereal (g n) = f n" by metis
hoelzl@43920
  2082
    hence "(%n. ereal (g n)) ----> l" using tail_same_limit[of f l N] assms by auto
hoelzl@41973
  2083
    hence *: "(%n. g n) ----> m" using m_def by auto
hoelzl@41973
  2084
    { fix n assume "n>=max N M"
hoelzl@43920
  2085
      hence "ereal (g n) <= ereal B" using assms g_def B_def by auto
hoelzl@41973
  2086
      hence "g n <= B" by auto
hoelzl@41973
  2087
    } hence "EX N. ALL n>=N. g n <= B" by blast
hoelzl@41973
  2088
    hence "m<=B" using * LIMSEQ_le_const2[of g m B] by auto
hoelzl@41973
  2089
    hence ?thesis using m_def B_def by auto
hoelzl@41973
  2090
  } ultimately have ?thesis by (cases C) auto
hoelzl@41973
  2091
} ultimately show ?thesis by blast
hoelzl@41973
  2092
qed
hoelzl@41973
  2093
hoelzl@43920
  2094
lemma real_of_ereal_mult[simp]:
hoelzl@43920
  2095
  fixes a b :: ereal shows "real (a * b) = real a * real b"
hoelzl@43920
  2096
  by (cases rule: ereal2_cases[of a b]) auto
hoelzl@41973
  2097
hoelzl@43920
  2098
lemma real_of_ereal_eq_0:
hoelzl@43923
  2099
  fixes x :: ereal shows "real x = 0 \<longleftrightarrow> x = \<infinity> \<or> x = -\<infinity> \<or> x = 0"
hoelzl@41973
  2100
  by (cases x) auto
hoelzl@41973
  2101
hoelzl@43920
  2102
lemma tendsto_ereal_realD:
hoelzl@43920
  2103
  fixes f :: "'a \<Rightarrow> ereal"
hoelzl@43920
  2104
  assumes "x \<noteq> 0" and tendsto: "((\<lambda>x. ereal (real (f x))) ---> x) net"
hoelzl@41973
  2105
  shows "(f ---> x) net"
hoelzl@41973
  2106
proof (intro topological_tendstoI)
hoelzl@41973
  2107
  fix S assume S: "open S" "x \<in> S"
hoelzl@41973
  2108
  with `x \<noteq> 0` have "open (S - {0})" "x \<in> S - {0}" by auto
hoelzl@41973
  2109
  from tendsto[THEN topological_tendstoD, OF this]
hoelzl@41973
  2110
  show "eventually (\<lambda>x. f x \<in> S) net"
huffman@44142
  2111
    by (rule eventually_rev_mp) (auto simp: ereal_real)
hoelzl@41973
  2112
qed
hoelzl@41973
  2113
hoelzl@43920
  2114
lemma tendsto_ereal_realI:
hoelzl@43920
  2115
  fixes f :: "'a \<Rightarrow> ereal"
hoelzl@41976
  2116
  assumes x: "\<bar>x\<bar> \<noteq> \<infinity>" and tendsto: "(f ---> x) net"
hoelzl@43920
  2117
  shows "((\<lambda>x. ereal (real (f x))) ---> x) net"
hoelzl@41973
  2118
proof (intro topological_tendstoI)
hoelzl@41973
  2119
  fix S assume "open S" "x \<in> S"
hoelzl@41973
  2120
  with x have "open (S - {\<infinity>, -\<infinity>})" "x \<in> S - {\<infinity>, -\<infinity>}" by auto
hoelzl@41973
  2121
  from tendsto[THEN topological_tendstoD, OF this]
hoelzl@43920
  2122
  show "eventually (\<lambda>x. ereal (real (f x)) \<in> S) net"
hoelzl@43920
  2123
    by (elim eventually_elim1) (auto simp: ereal_real)
hoelzl@41973
  2124
qed
hoelzl@41973
  2125
hoelzl@43920
  2126
lemma ereal_mult_cancel_left:
hoelzl@43920
  2127
  fixes a b c :: ereal shows "a * b = a * c \<longleftrightarrow>
hoelzl@41976
  2128
    ((\<bar>a\<bar> = \<infinity> \<and> 0 < b * c) \<or> a = 0 \<or> b = c)"
hoelzl@43920
  2129
  by (cases rule: ereal3_cases[of a b c])
hoelzl@41973
  2130
     (simp_all add: zero_less_mult_iff)
hoelzl@41973
  2131
hoelzl@43920
  2132
lemma ereal_inj_affinity:
hoelzl@43923
  2133
  fixes m t :: ereal
hoelzl@41976
  2134
  assumes "\<bar>m\<bar> \<noteq> \<infinity>" "m \<noteq> 0" "\<bar>t\<bar> \<noteq> \<infinity>"
hoelzl@41973
  2135
  shows "inj_on (\<lambda>x. m * x + t) A"
hoelzl@41973
  2136
  using assms
hoelzl@43920
  2137
  by (cases rule: ereal2_cases[of m t])
hoelzl@43920
  2138
     (auto intro!: inj_onI simp: ereal_add_cancel_right ereal_mult_cancel_left)
hoelzl@41973
  2139
hoelzl@43920
  2140
lemma ereal_PInfty_eq_plus[simp]:
hoelzl@43923
  2141
  fixes a b :: ereal
hoelzl@41973
  2142
  shows "\<infinity> = a + b \<longleftrightarrow> a = \<infinity> \<or> b = \<infinity>"
hoelzl@43920
  2143
  by (cases rule: ereal2_cases[of a b]) auto
hoelzl@41973
  2144
hoelzl@43920
  2145
lemma ereal_MInfty_eq_plus[simp]:
hoelzl@43923
  2146
  fixes a b :: ereal
hoelzl@41973
  2147
  shows "-\<infinity> = a + b \<longleftrightarrow> (a = -\<infinity> \<and> b \<noteq> \<infinity>) \<or> (b = -\<infinity> \<and> a \<noteq> \<infinity>)"
hoelzl@43920
  2148
  by (cases rule: ereal2_cases[of a b]) auto
hoelzl@41973
  2149
hoelzl@43920
  2150
lemma ereal_less_divide_pos:
hoelzl@43923
  2151
  fixes x y :: ereal
hoelzl@43923
  2152
  shows "x > 0 \<Longrightarrow> x \<noteq> \<infinity> \<Longrightarrow> y < z / x \<longleftrightarrow> x * y < z"
hoelzl@43920
  2153
  by (cases rule: ereal3_cases[of x y z]) (auto simp: field_simps)
hoelzl@41973
  2154
hoelzl@43920
  2155
lemma ereal_divide_less_pos:
hoelzl@43923
  2156
  fixes x y z :: ereal
hoelzl@43923
  2157
  shows "x > 0 \<Longrightarrow> x \<noteq> \<infinity> \<Longrightarrow> y / x < z \<longleftrightarrow> y < x * z"
hoelzl@43920
  2158
  by (cases rule: ereal3_cases[of x y z]) (auto simp: field_simps)
hoelzl@41973
  2159
hoelzl@43920
  2160
lemma ereal_divide_eq:
hoelzl@43923
  2161
  fixes a b c :: ereal
hoelzl@43923
  2162
  shows "b \<noteq> 0 \<Longrightarrow> \<bar>b\<bar> \<noteq> \<infinity> \<Longrightarrow> a / b = c \<longleftrightarrow> a = b * c"
hoelzl@43920
  2163
  by (cases rule: ereal3_cases[of a b c])
hoelzl@41973
  2164
     (simp_all add: field_simps)
hoelzl@41973
  2165
hoelzl@43923
  2166
lemma ereal_inverse_not_MInfty[simp]: "inverse (a::ereal) \<noteq> -\<infinity>"
hoelzl@41973
  2167
  by (cases a) auto
hoelzl@41973
  2168
hoelzl@43920
  2169
lemma ereal_mult_m1[simp]: "x * ereal (-1) = -x"
hoelzl@41973
  2170
  by (cases x) auto
hoelzl@41973
  2171
hoelzl@43920
  2172
lemma ereal_LimI_finite:
hoelzl@43923
  2173
  fixes x :: ereal
hoelzl@41976
  2174
  assumes "\<bar>x\<bar> \<noteq> \<infinity>"
hoelzl@41973
  2175
  assumes "!!r. 0 < r ==> EX N. ALL n>=N. u n < x + r & x < u n + r"
hoelzl@41973
  2176
  shows "u ----> x"
hoelzl@41973
  2177
proof (rule topological_tendstoI, unfold eventually_sequentially)
hoelzl@43920
  2178
  obtain rx where rx_def: "x=ereal rx" using assms by (cases x) auto
hoelzl@41973
  2179
  fix S assume "open S" "x : S"
hoelzl@43920
  2180
  then have "open (ereal -` S)" unfolding open_ereal_def by auto
hoelzl@43920
  2181
  with `x \<in> S` obtain r where "0 < r" and dist: "!!y. dist y rx < r ==> ereal y \<in> S"
hoelzl@41975
  2182
    unfolding open_real_def rx_def by auto
hoelzl@41973
  2183
  then obtain n where
hoelzl@43920
  2184
    upper: "!!N. n <= N ==> u N < x + ereal r" and
hoelzl@43920
  2185
    lower: "!!N. n <= N ==> x < u N + ereal r" using assms(2)[of "ereal r"] by auto
hoelzl@41973
  2186
  show "EX N. ALL n>=N. u n : S"
hoelzl@41973
  2187
  proof (safe intro!: exI[of _ n])
hoelzl@41973
  2188
    fix N assume "n <= N"
hoelzl@41973
  2189
    from upper[OF this] lower[OF this] assms `0 < r`
hoelzl@41973
  2190
    have "u N ~: {\<infinity>,(-\<infinity>)}" by auto
wenzelm@47082
  2191
    then obtain ra where ra_def: "(u N) = ereal ra" by (cases "u N") auto
hoelzl@41973
  2192
    hence "rx < ra + r" and "ra < rx + r"
hoelzl@41973
  2193
       using rx_def assms `0 < r` lower[OF `n <= N`] upper[OF `n <= N`] by auto
hoelzl@41975
  2194
    hence "dist (real (u N)) rx < r"
hoelzl@41973
  2195
      using rx_def ra_def
hoelzl@41973
  2196
      by (auto simp: dist_real_def abs_diff_less_iff field_simps)
hoelzl@41976
  2197
    from dist[OF this] show "u N : S" using `u N  ~: {\<infinity>, -\<infinity>}`
hoelzl@43920
  2198
      by (auto simp: ereal_real split: split_if_asm)
hoelzl@41973
  2199
  qed
hoelzl@41973
  2200
qed
hoelzl@41973
  2201
hoelzl@43920
  2202
lemma ereal_LimI_finite_iff:
hoelzl@43923
  2203
  fixes x :: ereal
hoelzl@41976
  2204
  assumes "\<bar>x\<bar> \<noteq> \<infinity>"
hoelzl@41973
  2205
  shows "u ----> x <-> (ALL r. 0 < r --> (EX N. ALL n>=N. u n < x + r & x < u n + r))"
hoelzl@41973
  2206
  (is "?lhs <-> ?rhs")
hoelzl@41976
  2207
proof
hoelzl@41976
  2208
  assume lim: "u ----> x"
hoelzl@43920
  2209
  { fix r assume "(r::ereal)>0"
wenzelm@47082
  2210
    then obtain N where N_def: "ALL n>=N. u n : {x - r <..< x + r}"
hoelzl@41973
  2211
       apply (subst tendsto_obtains_N[of u x "{x - r <..< x + r}"])
hoelzl@43920
  2212
       using lim ereal_between[of x r] assms `r>0` by auto
hoelzl@41973
  2213
    hence "EX N. ALL n>=N. u n < x + r & x < u n + r"
hoelzl@43920
  2214
      using ereal_minus_less[of r x] by (cases r) auto
hoelzl@41976
  2215
  } then show "?rhs" by auto
hoelzl@41976
  2216
next
hoelzl@41976
  2217
  assume ?rhs then show "u ----> x"
hoelzl@43920
  2218
    using ereal_LimI_finite[of x] assms by auto
hoelzl@41973
  2219
qed
hoelzl@41973
  2220
hoelzl@41973
  2221
hoelzl@41973
  2222
subsubsection {* @{text Liminf} and @{text Limsup} *}
hoelzl@41973
  2223
hoelzl@41973
  2224
definition
hoelzl@41973
  2225
  "Liminf net f = (GREATEST l. \<forall>y<l. eventually (\<lambda>x. y < f x) net)"
hoelzl@41973
  2226
hoelzl@41973
  2227
definition
hoelzl@41973
  2228
  "Limsup net f = (LEAST l. \<forall>y>l. eventually (\<lambda>x. f x < y) net)"
hoelzl@41973
  2229
hoelzl@41973
  2230
lemma Liminf_Sup:
haftmann@43941
  2231
  fixes f :: "'a => 'b::complete_linorder"
hoelzl@41973
  2232
  shows "Liminf net f = Sup {l. \<forall>y<l. eventually (\<lambda>x. y < f x) net}"
hoelzl@41973
  2233
  by (auto intro!: Greatest_equality complete_lattice_class.Sup_upper simp: less_Sup_iff Liminf_def)
hoelzl@41973
  2234
hoelzl@41973
  2235
lemma Limsup_Inf:
haftmann@43941
  2236
  fixes f :: "'a => 'b::complete_linorder"
hoelzl@41973
  2237
  shows "Limsup net f = Inf {l. \<forall>y>l. eventually (\<lambda>x. f x < y) net}"
hoelzl@41973
  2238
  by (auto intro!: Least_equality complete_lattice_class.Inf_lower simp: Inf_less_iff Limsup_def)
hoelzl@41973
  2239
hoelzl@43920
  2240
lemma ereal_SupI:
hoelzl@43920
  2241
  fixes x :: ereal
hoelzl@41973
  2242
  assumes "\<And>y. y \<in> A \<Longrightarrow> y \<le> x"
hoelzl@41973
  2243
  assumes "\<And>y. (\<And>z. z \<in> A \<Longrightarrow> z \<le> y) \<Longrightarrow> x \<le> y"
hoelzl@41973
  2244
  shows "Sup A = x"
hoelzl@43920
  2245
  unfolding Sup_ereal_def
hoelzl@41973
  2246
  using assms by (auto intro!: Least_equality)
hoelzl@41973
  2247
hoelzl@43920
  2248
lemma ereal_InfI:
hoelzl@43920
  2249
  fixes x :: ereal
hoelzl@41973
  2250
  assumes "\<And>i. i \<in> A \<Longrightarrow> x \<le> i"
hoelzl@41973
  2251
  assumes "\<And>y. (\<And>i. i \<in> A \<Longrightarrow> y \<le> i) \<Longrightarrow> y \<le> x"
hoelzl@41973
  2252
  shows "Inf A = x"
hoelzl@43920
  2253
  unfolding Inf_ereal_def
hoelzl@41973
  2254
  using assms by (auto intro!: Greatest_equality)
hoelzl@41973
  2255
hoelzl@41973
  2256
lemma Limsup_const:
haftmann@43941
  2257
  fixes c :: "'a::complete_linorder"
hoelzl@41973
  2258
  assumes ntriv: "\<not> trivial_limit net"
hoelzl@41973
  2259
  shows "Limsup net (\<lambda>x. c) = c"
hoelzl@41973
  2260
  unfolding Limsup_Inf
hoelzl@41973
  2261
proof (safe intro!: antisym complete_lattice_class.Inf_greatest complete_lattice_class.Inf_lower)
hoelzl@41973
  2262
  fix x assume *: "\<forall>y>x. eventually (\<lambda>_. c < y) net"
hoelzl@41973
  2263
  show "c \<le> x"
hoelzl@41973
  2264
  proof (rule ccontr)
hoelzl@41973
  2265
    assume "\<not> c \<le> x" then have "x < c" by auto
hoelzl@41973
  2266
    then show False using ntriv * by (auto simp: trivial_limit_def)
hoelzl@41973
  2267
  qed
hoelzl@41973
  2268
qed auto
hoelzl@41973
  2269
hoelzl@41973
  2270
lemma Liminf_const:
haftmann@43941
  2271
  fixes c :: "'a::complete_linorder"
hoelzl@41973
  2272
  assumes ntriv: "\<not> trivial_limit net"
hoelzl@41973
  2273
  shows "Liminf net (\<lambda>x. c) = c"
hoelzl@41973
  2274
  unfolding Liminf_Sup
hoelzl@41973
  2275
proof (safe intro!: antisym complete_lattice_class.Sup_least complete_lattice_class.Sup_upper)
hoelzl@41973
  2276
  fix x assume *: "\<forall>y<x. eventually (\<lambda>_. y < c) net"
hoelzl@41973
  2277
  show "x \<le> c"
hoelzl@41973
  2278
  proof (rule ccontr)
hoelzl@41973
  2279
    assume "\<not> x \<le> c" then have "c < x" by auto
hoelzl@41973
  2280
    then show False using ntriv * by (auto simp: trivial_limit_def)
hoelzl@41973
  2281
  qed
hoelzl@41973
  2282
qed auto
hoelzl@41973
  2283
huffman@44170
  2284
definition (in order) mono_set:
huffman@44170
  2285
  "mono_set S \<longleftrightarrow> (\<forall>x y. x \<le> y \<longrightarrow> x \<in> S \<longrightarrow> y \<in> S)"
hoelzl@41973
  2286
huffman@44170
  2287
lemma (in order) mono_greaterThan [intro, simp]: "mono_set {B<..}" unfolding mono_set by auto
huffman@44170
  2288
lemma (in order) mono_atLeast [intro, simp]: "mono_set {B..}" unfolding mono_set by auto
huffman@44170
  2289
lemma (in order) mono_UNIV [intro, simp]: "mono_set UNIV" unfolding mono_set by auto
huffman@44170
  2290
lemma (in order) mono_empty [intro, simp]: "mono_set {}" unfolding mono_set by auto
hoelzl@41973
  2291
haftmann@43941
  2292
lemma (in complete_linorder) mono_set_iff:
haftmann@43941
  2293
  fixes S :: "'a set"
hoelzl@41973
  2294
  defines "a \<equiv> Inf S"
huffman@44170
  2295
  shows "mono_set S \<longleftrightarrow> (S = {a <..} \<or> S = {a..})" (is "_ = ?c")
hoelzl@41973
  2296
proof
huffman@44170
  2297
  assume "mono_set S"
hoelzl@41973
  2298
  then have mono: "\<And>x y. x \<le> y \<Longrightarrow> x \<in> S \<Longrightarrow> y \<in> S" by (auto simp: mono_set)
hoelzl@41973
  2299
  show ?c
hoelzl@41973
  2300
  proof cases
hoelzl@41973
  2301
    assume "a \<in> S"
hoelzl@41973
  2302
    show ?c
hoelzl@41973
  2303
      using mono[OF _ `a \<in> S`]
haftmann@43941
  2304
      by (auto intro: Inf_lower simp: a_def)
hoelzl@41973
  2305
  next
hoelzl@41973
  2306
    assume "a \<notin> S"
hoelzl@41973
  2307
    have "S = {a <..}"
hoelzl@41973
  2308
    proof safe
hoelzl@41973
  2309
      fix x assume "x \<in> S"
haftmann@43941
  2310
      then have "a \<le> x" unfolding a_def by (rule Inf_lower)
hoelzl@41973
  2311
      then show "a < x" using `x \<in> S` `a \<notin> S` by (cases "a = x") auto
hoelzl@41973
  2312
    next
hoelzl@41973
  2313
      fix x assume "a < x"
hoelzl@41973
  2314
      then obtain y where "y < x" "y \<in> S" unfolding a_def Inf_less_iff ..
hoelzl@41973
  2315
      with mono[of y x] show "x \<in> S" by auto
hoelzl@41973
  2316
    qed
hoelzl@41973
  2317
    then show ?c ..
hoelzl@41973
  2318
  qed
hoelzl@41973
  2319
qed auto
hoelzl@41973
  2320
hoelzl@41973
  2321
lemma lim_imp_Liminf:
hoelzl@43920
  2322
  fixes f :: "'a \<Rightarrow> ereal"
hoelzl@41973
  2323
  assumes ntriv: "\<not> trivial_limit net"
hoelzl@41973
  2324
  assumes lim: "(f ---> f0) net"
hoelzl@41973
  2325
  shows "Liminf net f = f0"
hoelzl@41973
  2326
  unfolding Liminf_Sup
hoelzl@43920
  2327
proof (safe intro!: ereal_SupI)
hoelzl@41973
  2328
  fix y assume *: "\<forall>y'<y. eventually (\<lambda>x. y' < f x) net"
hoelzl@41973
  2329
  show "y \<le> f0"
hoelzl@43920
  2330
  proof (rule ereal_le_ereal)
hoelzl@41973
  2331
    fix B assume "B < y"
hoelzl@41973
  2332
    { assume "f0 < B"
hoelzl@41973
  2333
      then have "eventually (\<lambda>x. f x < B \<and> B < f x) net"
hoelzl@41973
  2334
         using topological_tendstoD[OF lim, of "{..<B}"] *[rule_format, OF `B < y`]
hoelzl@41973
  2335
         by (auto intro: eventually_conj)
hoelzl@41973
  2336
      also have "(\<lambda>x. f x < B \<and> B < f x) = (\<lambda>x. False)" by (auto simp: fun_eq_iff)
hoelzl@41973
  2337
      finally have False using ntriv[unfolded trivial_limit_def] by auto
hoelzl@41973
  2338
    } then show "B \<le> f0" by (metis linorder_le_less_linear)
hoelzl@41973
  2339
  qed
hoelzl@41973
  2340
next
hoelzl@41973
  2341
  fix y assume *: "\<forall>z. z \<in> {l. \<forall>y<l. eventually (\<lambda>x. y < f x) net} \<longrightarrow> z \<le> y"
hoelzl@41973
  2342
  show "f0 \<le> y"
hoelzl@41973
  2343
  proof (safe intro!: *[rule_format])
hoelzl@41973
  2344
    fix y assume "y < f0" then show "eventually (\<lambda>x. y < f x) net"
hoelzl@41973
  2345
      using lim[THEN topological_tendstoD, of "{y <..}"] by auto
hoelzl@41973
  2346
  qed
hoelzl@41973
  2347
qed
hoelzl@41973
  2348
hoelzl@43920
  2349
lemma ereal_Liminf_le_Limsup:
hoelzl@43920
  2350
  fixes f :: "'a \<Rightarrow> ereal"
hoelzl@41973
  2351
  assumes ntriv: "\<not> trivial_limit net"
hoelzl@41973
  2352
  shows "Liminf net f \<le> Limsup net f"
hoelzl@41973
  2353
  unfolding Limsup_Inf Liminf_Sup
hoelzl@41973
  2354
proof (safe intro!: complete_lattice_class.Inf_greatest  complete_lattice_class.Sup_least)
hoelzl@41973
  2355
  fix u v assume *: "\<forall>y<u. eventually (\<lambda>x. y < f x) net" "\<forall>y>v. eventually (\<lambda>x. f x < y) net"
hoelzl@41973
  2356
  show "u \<le> v"
hoelzl@41973
  2357
  proof (rule ccontr)
hoelzl@41973
  2358
    assume "\<not> u \<le> v"
hoelzl@41973
  2359
    then obtain t where "t < u" "v < t"
hoelzl@43920
  2360
      using ereal_dense[of v u] by (auto simp: not_le)
hoelzl@41973
  2361
    then have "eventually (\<lambda>x. t < f x \<and> f x < t) net"
hoelzl@41973
  2362
      using * by (auto intro: eventually_conj)
hoelzl@41973
  2363
    also have "(\<lambda>x. t < f x \<and> f x < t) = (\<lambda>x. False)" by (auto simp: fun_eq_iff)
hoelzl@41973
  2364
    finally show False using ntriv by (auto simp: trivial_limit_def)
hoelzl@41973
  2365
  qed
hoelzl@41973
  2366
qed
hoelzl@41973
  2367
hoelzl@41973
  2368
lemma Liminf_mono:
hoelzl@43920
  2369
  fixes f g :: "'a => ereal"
hoelzl@41973
  2370
  assumes ev: "eventually (\<lambda>x. f x \<le> g x) net"
hoelzl@41973
  2371
  shows "Liminf net f \<le> Liminf net g"
hoelzl@41973
  2372
  unfolding Liminf_Sup
hoelzl@41973
  2373
proof (safe intro!: Sup_mono bexI)
hoelzl@41973
  2374
  fix a y assume "\<forall>y<a. eventually (\<lambda>x. y < f x) net" and "y < a"
hoelzl@41973
  2375
  then have "eventually (\<lambda>x. y < f x) net" by auto
hoelzl@41973
  2376
  then show "eventually (\<lambda>x. y < g x) net"
hoelzl@41973
  2377
    by (rule eventually_rev_mp) (rule eventually_mono[OF _ ev], auto)
hoelzl@41973
  2378
qed simp
hoelzl@41973
  2379
hoelzl@41973
  2380
lemma Liminf_eq:
hoelzl@43920
  2381
  fixes f g :: "'a \<Rightarrow> ereal"
hoelzl@41973
  2382
  assumes "eventually (\<lambda>x. f x = g x) net"
hoelzl@41973
  2383
  shows "Liminf net f = Liminf net g"
hoelzl@41973
  2384
  by (intro antisym Liminf_mono eventually_mono[OF _ assms]) auto
hoelzl@41973
  2385
hoelzl@41973
  2386
lemma Liminf_mono_all:
hoelzl@43920
  2387
  fixes f g :: "'a \<Rightarrow> ereal"
hoelzl@41973
  2388
  assumes "\<And>x. f x \<le> g x"
hoelzl@41973
  2389
  shows "Liminf net f \<le> Liminf net g"
hoelzl@41973
  2390
  using assms by (intro Liminf_mono always_eventually) auto
hoelzl@41973
  2391
hoelzl@41973
  2392
lemma Limsup_mono:
hoelzl@43920
  2393
  fixes f g :: "'a \<Rightarrow> ereal"
hoelzl@41973
  2394
  assumes ev: "eventually (\<lambda>x. f x \<le> g x) net"
hoelzl@41973
  2395
  shows "Limsup net f \<le> Limsup net g"
hoelzl@41973
  2396
  unfolding Limsup_Inf
hoelzl@41973
  2397
proof (safe intro!: Inf_mono bexI)
hoelzl@41973
  2398
  fix a y assume "\<forall>y>a. eventually (\<lambda>x. g x < y) net" and "a < y"
hoelzl@41973
  2399
  then have "eventually (\<lambda>x. g x < y) net" by auto
hoelzl@41973
  2400
  then show "eventually (\<lambda>x. f x < y) net"
hoelzl@41973
  2401
    by (rule eventually_rev_mp) (rule eventually_mono[OF _ ev], auto)
hoelzl@41973
  2402
qed simp
hoelzl@41973
  2403
hoelzl@41973
  2404
lemma Limsup_mono_all:
hoelzl@43920
  2405
  fixes f g :: "'a \<Rightarrow> ereal"
hoelzl@41973
  2406
  assumes "\<And>x. f x \<le> g x"
hoelzl@41973
  2407
  shows "Limsup net f \<le> Limsup net g"
hoelzl@41973
  2408
  using assms by (intro Limsup_mono always_eventually) auto
hoelzl@41973
  2409
hoelzl@41973
  2410
lemma Limsup_eq:
hoelzl@43920
  2411
  fixes f g :: "'a \<Rightarrow> ereal"
hoelzl@41973
  2412
  assumes "eventually (\<lambda>x. f x = g x) net"
hoelzl@41973
  2413
  shows "Limsup net f = Limsup net g"
hoelzl@41973
  2414
  by (intro antisym Limsup_mono eventually_mono[OF _ assms]) auto
hoelzl@41973
  2415
hoelzl@41973
  2416
abbreviation "liminf \<equiv> Liminf sequentially"
hoelzl@41973
  2417
hoelzl@41973
  2418
abbreviation "limsup \<equiv> Limsup sequentially"
hoelzl@41973
  2419
hoelzl@41973
  2420
lemma liminf_SUPR_INFI:
hoelzl@43920
  2421
  fixes f :: "nat \<Rightarrow> ereal"
hoelzl@41973
  2422
  shows "liminf f = (SUP n. INF m:{n..}. f m)"
hoelzl@41973
  2423
  unfolding Liminf_Sup eventually_sequentially
hoelzl@41973
  2424
proof (safe intro!: antisym complete_lattice_class.Sup_least)
hoelzl@41973
  2425
  fix x assume *: "\<forall>y<x. \<exists>N. \<forall>n\<ge>N. y < f n" show "x \<le> (SUP n. INF m:{n..}. f m)"
hoelzl@43920
  2426
  proof (rule ereal_le_ereal)
hoelzl@41973
  2427
    fix y assume "y < x"
hoelzl@41973
  2428
    with * obtain N where "\<And>n. N \<le> n \<Longrightarrow> y < f n" by auto
hoelzl@41973
  2429
    then have "y \<le> (INF m:{N..}. f m)" by (force simp: le_INF_iff)
hoelzl@44928
  2430
    also have "\<dots> \<le> (SUP n. INF m:{n..}. f m)" by (intro SUP_upper) auto
hoelzl@41973
  2431
    finally show "y \<le> (SUP n. INF m:{n..}. f m)" .
hoelzl@41973
  2432
  qed
hoelzl@41973
  2433
next
hoelzl@41973
  2434
  show "(SUP n. INF m:{n..}. f m) \<le> Sup {l. \<forall>y<l. \<exists>N. \<forall>n\<ge>N. y < f n}"
hoelzl@44928
  2435
  proof (unfold SUP_def, safe intro!: Sup_mono bexI)
hoelzl@41973
  2436
    fix y n assume "y < INFI {n..} f"
hoelzl@44928
  2437
    from less_INF_D[OF this] show "\<exists>N. \<forall>n\<ge>N. y < f n" by (intro exI[of _ n]) auto
hoelzl@41973
  2438
  qed (rule order_refl)
hoelzl@41973
  2439
qed
hoelzl@41973
  2440
hoelzl@41973
  2441
lemma tail_same_limsup:
hoelzl@43920
  2442
  fixes X Y :: "nat => ereal"
hoelzl@41973
  2443
  assumes "\<And>n. N \<le> n \<Longrightarrow> X n = Y n"
hoelzl@41973
  2444
  shows "limsup X = limsup Y"
hoelzl@41973
  2445
  using Limsup_eq[of X Y sequentially] eventually_sequentially assms by auto
hoelzl@41973
  2446
hoelzl@41973
  2447
lemma tail_same_liminf:
hoelzl@43920
  2448
  fixes X Y :: "nat => ereal"
hoelzl@41973
  2449
  assumes "\<And>n. N \<le> n \<Longrightarrow> X n = Y n"
hoelzl@41973
  2450
  shows "liminf X = liminf Y"
hoelzl@41973
  2451
  using Liminf_eq[of X Y sequentially] eventually_sequentially assms by auto
hoelzl@41973
  2452
hoelzl@41973
  2453
lemma liminf_mono:
hoelzl@43920
  2454
  fixes X Y :: "nat \<Rightarrow> ereal"
hoelzl@41973
  2455
  assumes "\<And>n. N \<le> n \<Longrightarrow> X n <= Y n"
hoelzl@41973
  2456
  shows "liminf X \<le> liminf Y"
hoelzl@41973
  2457
  using Liminf_mono[of X Y sequentially] eventually_sequentially assms by auto
hoelzl@41973
  2458
hoelzl@41973
  2459
lemma limsup_mono:
hoelzl@43920
  2460
  fixes X Y :: "nat => ereal"
hoelzl@41973
  2461
  assumes "\<And>n. N \<le> n \<Longrightarrow> X n <= Y n"
hoelzl@41973
  2462
  shows "limsup X \<le> limsup Y"
hoelzl@41973
  2463
  using Limsup_mono[of X Y sequentially] eventually_sequentially assms by auto
hoelzl@41973
  2464
hoelzl@41978
  2465
lemma
hoelzl@43920
  2466
  fixes X :: "nat \<Rightarrow> ereal"
hoelzl@43920
  2467
  shows ereal_incseq_uminus[simp]: "incseq (\<lambda>i. - X i) = decseq X"
hoelzl@43920
  2468
    and ereal_decseq_uminus[simp]: "decseq (\<lambda>i. - X i) = incseq X"
hoelzl@41978
  2469
  unfolding incseq_def decseq_def by auto
hoelzl@41978
  2470
hoelzl@41973
  2471
lemma liminf_bounded:
hoelzl@43920
  2472
  fixes X Y :: "nat \<Rightarrow> ereal"
hoelzl@41973
  2473
  assumes "\<And>n. N \<le> n \<Longrightarrow> C \<le> X n"
hoelzl@41973
  2474
  shows "C \<le> liminf X"
hoelzl@41973
  2475
  using liminf_mono[of N "\<lambda>n. C" X] assms Liminf_const[of sequentially C] by simp
hoelzl@41973
  2476
hoelzl@41973
  2477
lemma limsup_bounded:
hoelzl@43920
  2478
  fixes X Y :: "nat => ereal"
hoelzl@41973
  2479
  assumes "\<And>n. N \<le> n \<Longrightarrow> X n <= C"
hoelzl@41973
  2480
  shows "limsup X \<le> C"
hoelzl@41973
  2481
  using limsup_mono[of N X "\<lambda>n. C"] assms Limsup_const[of sequentially C] by simp
hoelzl@41973
  2482
hoelzl@41973
  2483
lemma liminf_bounded_iff:
hoelzl@43920
  2484
  fixes x :: "nat \<Rightarrow> ereal"
hoelzl@41973
  2485
  shows "C \<le> liminf x \<longleftrightarrow> (\<forall>B<C. \<exists>N. \<forall>n\<ge>N. B < x n)" (is "?lhs <-> ?rhs")
hoelzl@41973
  2486
proof safe