src/HOL/Fun.thy
author blanchet
Thu Jan 16 16:50:41 2014 +0100 (2014-01-16)
changeset 55019 0d5e831175de
parent 54578 9387251b6a46
child 55066 4e5ddf3162ac
permissions -rw-r--r--
moved lemmas from 'Fun_More_FP' to where they belong
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(*  Title:      HOL/Fun.thy
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    Author:     Tobias Nipkow, Cambridge University Computer Laboratory
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    Author:     Andrei Popescu, TU Muenchen
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    Copyright   1994, 2012
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*)
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header {* Notions about functions *}
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theory Fun
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imports Complete_Lattices
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keywords "enriched_type" :: thy_goal
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begin
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lemma apply_inverse:
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  "f x = u \<Longrightarrow> (\<And>x. P x \<Longrightarrow> g (f x) = x) \<Longrightarrow> P x \<Longrightarrow> x = g u"
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  by auto
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subsection {* The Identity Function @{text id} *}
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definition id :: "'a \<Rightarrow> 'a" where
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  "id = (\<lambda>x. x)"
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lemma id_apply [simp]: "id x = x"
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  by (simp add: id_def)
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lemma image_id [simp]: "image id = id"
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  by (simp add: id_def fun_eq_iff)
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lemma vimage_id [simp]: "vimage id = id"
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  by (simp add: id_def fun_eq_iff)
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code_printing
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  constant id \<rightharpoonup> (Haskell) "id"
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subsection {* The Composition Operator @{text "f \<circ> g"} *}
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definition comp :: "('b \<Rightarrow> 'c) \<Rightarrow> ('a \<Rightarrow> 'b) \<Rightarrow> 'a \<Rightarrow> 'c" (infixl "o" 55) where
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  "f o g = (\<lambda>x. f (g x))"
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notation (xsymbols)
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  comp  (infixl "\<circ>" 55)
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notation (HTML output)
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  comp  (infixl "\<circ>" 55)
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lemma comp_apply [simp]: "(f o g) x = f (g x)"
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  by (simp add: comp_def)
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lemma comp_assoc: "(f o g) o h = f o (g o h)"
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  by (simp add: fun_eq_iff)
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lemma id_comp [simp]: "id o g = g"
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  by (simp add: fun_eq_iff)
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lemma comp_id [simp]: "f o id = f"
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  by (simp add: fun_eq_iff)
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lemma comp_eq_dest:
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  "a o b = c o d \<Longrightarrow> a (b v) = c (d v)"
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  by (simp add: fun_eq_iff)
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lemma comp_eq_elim:
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  "a o b = c o d \<Longrightarrow> ((\<And>v. a (b v) = c (d v)) \<Longrightarrow> R) \<Longrightarrow> R"
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  by (simp add: fun_eq_iff) 
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lemma image_comp:
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  "(f o g) ` r = f ` (g ` r)"
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  by auto
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lemma vimage_comp:
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  "(g \<circ> f) -` x = f -` (g -` x)"
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  by auto
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lemma INF_comp:
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  "INFI A (g \<circ> f) = INFI (f ` A) g"
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  by (simp add: INF_def image_comp)
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lemma SUP_comp:
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  "SUPR A (g \<circ> f) = SUPR (f ` A) g"
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  by (simp add: SUP_def image_comp)
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code_printing
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  constant comp \<rightharpoonup> (SML) infixl 5 "o" and (Haskell) infixr 9 "."
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subsection {* The Forward Composition Operator @{text fcomp} *}
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definition fcomp :: "('a \<Rightarrow> 'b) \<Rightarrow> ('b \<Rightarrow> 'c) \<Rightarrow> 'a \<Rightarrow> 'c" (infixl "\<circ>>" 60) where
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  "f \<circ>> g = (\<lambda>x. g (f x))"
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lemma fcomp_apply [simp]:  "(f \<circ>> g) x = g (f x)"
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  by (simp add: fcomp_def)
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lemma fcomp_assoc: "(f \<circ>> g) \<circ>> h = f \<circ>> (g \<circ>> h)"
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  by (simp add: fcomp_def)
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lemma id_fcomp [simp]: "id \<circ>> g = g"
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  by (simp add: fcomp_def)
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lemma fcomp_id [simp]: "f \<circ>> id = f"
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  by (simp add: fcomp_def)
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code_printing
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  constant fcomp \<rightharpoonup> (Eval) infixl 1 "#>"
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no_notation fcomp (infixl "\<circ>>" 60)
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subsection {* Mapping functions *}
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definition map_fun :: "('c \<Rightarrow> 'a) \<Rightarrow> ('b \<Rightarrow> 'd) \<Rightarrow> ('a \<Rightarrow> 'b) \<Rightarrow> 'c \<Rightarrow> 'd" where
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  "map_fun f g h = g \<circ> h \<circ> f"
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lemma map_fun_apply [simp]:
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  "map_fun f g h x = g (h (f x))"
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  by (simp add: map_fun_def)
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subsection {* Injectivity and Bijectivity *}
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definition inj_on :: "('a \<Rightarrow> 'b) \<Rightarrow> 'a set \<Rightarrow> bool" where -- "injective"
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  "inj_on f A \<longleftrightarrow> (\<forall>x\<in>A. \<forall>y\<in>A. f x = f y \<longrightarrow> x = y)"
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definition bij_betw :: "('a \<Rightarrow> 'b) \<Rightarrow> 'a set \<Rightarrow> 'b set \<Rightarrow> bool" where -- "bijective"
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  "bij_betw f A B \<longleftrightarrow> inj_on f A \<and> f ` A = B"
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text{*A common special case: functions injective, surjective or bijective over
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the entire domain type.*}
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abbreviation
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  "inj f \<equiv> inj_on f UNIV"
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abbreviation surj :: "('a \<Rightarrow> 'b) \<Rightarrow> bool" where -- "surjective"
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  "surj f \<equiv> (range f = UNIV)"
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abbreviation
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  "bij f \<equiv> bij_betw f UNIV UNIV"
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text{* The negated case: *}
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translations
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"\<not> CONST surj f" <= "CONST range f \<noteq> CONST UNIV"
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lemma injI:
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  assumes "\<And>x y. f x = f y \<Longrightarrow> x = y"
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  shows "inj f"
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  using assms unfolding inj_on_def by auto
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theorem range_ex1_eq: "inj f \<Longrightarrow> b : range f = (EX! x. b = f x)"
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  by (unfold inj_on_def, blast)
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lemma injD: "[| inj(f); f(x) = f(y) |] ==> x=y"
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by (simp add: inj_on_def)
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lemma inj_on_eq_iff: "inj_on f A ==> x:A ==> y:A ==> (f(x) = f(y)) = (x=y)"
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by (force simp add: inj_on_def)
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lemma inj_on_cong:
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  "(\<And> a. a : A \<Longrightarrow> f a = g a) \<Longrightarrow> inj_on f A = inj_on g A"
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unfolding inj_on_def by auto
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lemma inj_on_strict_subset:
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  "\<lbrakk> inj_on f B; A < B \<rbrakk> \<Longrightarrow> f`A < f`B"
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unfolding inj_on_def unfolding image_def by blast
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lemma inj_comp:
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  "inj f \<Longrightarrow> inj g \<Longrightarrow> inj (f \<circ> g)"
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  by (simp add: inj_on_def)
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lemma inj_fun: "inj f \<Longrightarrow> inj (\<lambda>x y. f x)"
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  by (simp add: inj_on_def fun_eq_iff)
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lemma inj_eq: "inj f ==> (f(x) = f(y)) = (x=y)"
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by (simp add: inj_on_eq_iff)
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lemma inj_on_id[simp]: "inj_on id A"
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  by (simp add: inj_on_def)
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lemma inj_on_id2[simp]: "inj_on (%x. x) A"
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by (simp add: inj_on_def)
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lemma inj_on_Int: "inj_on f A \<or> inj_on f B \<Longrightarrow> inj_on f (A \<inter> B)"
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unfolding inj_on_def by blast
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lemma inj_on_INTER:
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  "\<lbrakk>I \<noteq> {}; \<And> i. i \<in> I \<Longrightarrow> inj_on f (A i)\<rbrakk> \<Longrightarrow> inj_on f (\<Inter> i \<in> I. A i)"
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unfolding inj_on_def by blast
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lemma inj_on_Inter:
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  "\<lbrakk>S \<noteq> {}; \<And> A. A \<in> S \<Longrightarrow> inj_on f A\<rbrakk> \<Longrightarrow> inj_on f (Inter S)"
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unfolding inj_on_def by blast
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lemma inj_on_UNION_chain:
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  assumes CH: "\<And> i j. \<lbrakk>i \<in> I; j \<in> I\<rbrakk> \<Longrightarrow> A i \<le> A j \<or> A j \<le> A i" and
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         INJ: "\<And> i. i \<in> I \<Longrightarrow> inj_on f (A i)"
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  shows "inj_on f (\<Union> i \<in> I. A i)"
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proof -
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  {
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    fix i j x y
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    assume *: "i \<in> I" "j \<in> I" and **: "x \<in> A i" "y \<in> A j"
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      and ***: "f x = f y"
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    have "x = y"
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    proof -
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      {
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        assume "A i \<le> A j"
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        with ** have "x \<in> A j" by auto
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        with INJ * ** *** have ?thesis
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        by(auto simp add: inj_on_def)
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      }
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      moreover
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      {
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        assume "A j \<le> A i"
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        with ** have "y \<in> A i" by auto
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        with INJ * ** *** have ?thesis
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        by(auto simp add: inj_on_def)
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      }
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      ultimately show ?thesis using CH * by blast
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    qed
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  }
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  then show ?thesis by (unfold inj_on_def UNION_eq) auto
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qed
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lemma surj_id: "surj id"
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by simp
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lemma bij_id[simp]: "bij id"
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by (simp add: bij_betw_def)
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lemma inj_onI:
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    "(!! x y. [|  x:A;  y:A;  f(x) = f(y) |] ==> x=y) ==> inj_on f A"
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by (simp add: inj_on_def)
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lemma inj_on_inverseI: "(!!x. x:A ==> g(f(x)) = x) ==> inj_on f A"
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by (auto dest:  arg_cong [of concl: g] simp add: inj_on_def)
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lemma inj_onD: "[| inj_on f A;  f(x)=f(y);  x:A;  y:A |] ==> x=y"
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by (unfold inj_on_def, blast)
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lemma inj_on_iff: "[| inj_on f A;  x:A;  y:A |] ==> (f(x)=f(y)) = (x=y)"
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by (blast dest!: inj_onD)
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lemma comp_inj_on:
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     "[| inj_on f A;  inj_on g (f`A) |] ==> inj_on (g o f) A"
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by (simp add: comp_def inj_on_def)
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lemma inj_on_imageI: "inj_on (g o f) A \<Longrightarrow> inj_on g (f ` A)"
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apply(simp add:inj_on_def image_def)
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apply blast
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done
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lemma inj_on_image_iff: "\<lbrakk> ALL x:A. ALL y:A. (g(f x) = g(f y)) = (g x = g y);
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  inj_on f A \<rbrakk> \<Longrightarrow> inj_on g (f ` A) = inj_on g A"
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apply(unfold inj_on_def)
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apply blast
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done
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lemma inj_on_contraD: "[| inj_on f A;  ~x=y;  x:A;  y:A |] ==> ~ f(x)=f(y)"
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by (unfold inj_on_def, blast)
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lemma inj_singleton: "inj (%s. {s})"
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by (simp add: inj_on_def)
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lemma inj_on_empty[iff]: "inj_on f {}"
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by(simp add: inj_on_def)
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lemma subset_inj_on: "[| inj_on f B; A <= B |] ==> inj_on f A"
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by (unfold inj_on_def, blast)
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lemma inj_on_Un:
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 "inj_on f (A Un B) =
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  (inj_on f A & inj_on f B & f`(A-B) Int f`(B-A) = {})"
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apply(unfold inj_on_def)
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apply (blast intro:sym)
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done
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lemma inj_on_insert[iff]:
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  "inj_on f (insert a A) = (inj_on f A & f a ~: f`(A-{a}))"
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apply(unfold inj_on_def)
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apply (blast intro:sym)
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done
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lemma inj_on_diff: "inj_on f A ==> inj_on f (A-B)"
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apply(unfold inj_on_def)
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apply (blast)
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done
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lemma comp_inj_on_iff:
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  "inj_on f A \<Longrightarrow> inj_on f' (f ` A) \<longleftrightarrow> inj_on (f' o f) A"
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by(auto simp add: comp_inj_on inj_on_def)
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lemma inj_on_imageI2:
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  "inj_on (f' o f) A \<Longrightarrow> inj_on f A"
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by(auto simp add: comp_inj_on inj_on_def)
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lemma inj_img_insertE:
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  assumes "inj_on f A"
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  assumes "x \<notin> B" and "insert x B = f ` A"
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  obtains x' A' where "x' \<notin> A'" and "A = insert x' A'"
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    and "x = f x'" and "B = f ` A'"
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proof -
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  from assms have "x \<in> f ` A" by auto
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  then obtain x' where *: "x' \<in> A" "x = f x'" by auto
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  then have "A = insert x' (A - {x'})" by auto
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  with assms * have "B = f ` (A - {x'})"
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    by (auto dest: inj_on_contraD)
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  have "x' \<notin> A - {x'}" by simp
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  from `x' \<notin> A - {x'}` `A = insert x' (A - {x'})` `x = f x'` `B = image f (A - {x'})`
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  show ?thesis ..
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qed
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lemma linorder_injI:
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  assumes hyp: "\<And>x y. x < (y::'a::linorder) \<Longrightarrow> f x \<noteq> f y"
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  shows "inj f"
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  -- {* Courtesy of Stephan Merz *}
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proof (rule inj_onI)
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  fix x y
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  assume f_eq: "f x = f y"
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  show "x = y" by (rule linorder_cases) (auto dest: hyp simp: f_eq)
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qed
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hoelzl@40702
   322
lemma surj_def: "surj f \<longleftrightarrow> (\<forall>y. \<exists>x. y = f x)"
hoelzl@40702
   323
  by auto
hoelzl@39076
   324
hoelzl@40702
   325
lemma surjI: assumes *: "\<And> x. g (f x) = x" shows "surj g"
hoelzl@40702
   326
  using *[symmetric] by auto
paulson@13585
   327
hoelzl@39076
   328
lemma surjD: "surj f \<Longrightarrow> \<exists>x. y = f x"
hoelzl@39076
   329
  by (simp add: surj_def)
paulson@13585
   330
hoelzl@39076
   331
lemma surjE: "surj f \<Longrightarrow> (\<And>x. y = f x \<Longrightarrow> C) \<Longrightarrow> C"
hoelzl@39076
   332
  by (simp add: surj_def, blast)
paulson@13585
   333
paulson@13585
   334
lemma comp_surj: "[| surj f;  surj g |] ==> surj (g o f)"
paulson@13585
   335
apply (simp add: comp_def surj_def, clarify)
paulson@13585
   336
apply (drule_tac x = y in spec, clarify)
paulson@13585
   337
apply (drule_tac x = x in spec, blast)
paulson@13585
   338
done
paulson@13585
   339
hoelzl@39074
   340
lemma bij_betw_imp_surj: "bij_betw f A UNIV \<Longrightarrow> surj f"
hoelzl@40702
   341
  unfolding bij_betw_def by auto
hoelzl@39074
   342
hoelzl@40703
   343
lemma bij_betw_empty1:
hoelzl@40703
   344
  assumes "bij_betw f {} A"
hoelzl@40703
   345
  shows "A = {}"
hoelzl@40703
   346
using assms unfolding bij_betw_def by blast
hoelzl@40703
   347
hoelzl@40703
   348
lemma bij_betw_empty2:
hoelzl@40703
   349
  assumes "bij_betw f A {}"
hoelzl@40703
   350
  shows "A = {}"
hoelzl@40703
   351
using assms unfolding bij_betw_def by blast
hoelzl@40703
   352
hoelzl@40703
   353
lemma inj_on_imp_bij_betw:
hoelzl@40703
   354
  "inj_on f A \<Longrightarrow> bij_betw f A (f ` A)"
hoelzl@40703
   355
unfolding bij_betw_def by simp
hoelzl@40703
   356
hoelzl@39076
   357
lemma bij_def: "bij f \<longleftrightarrow> inj f \<and> surj f"
hoelzl@40702
   358
  unfolding bij_betw_def ..
hoelzl@39074
   359
paulson@13585
   360
lemma bijI: "[| inj f; surj f |] ==> bij f"
paulson@13585
   361
by (simp add: bij_def)
paulson@13585
   362
paulson@13585
   363
lemma bij_is_inj: "bij f ==> inj f"
paulson@13585
   364
by (simp add: bij_def)
paulson@13585
   365
paulson@13585
   366
lemma bij_is_surj: "bij f ==> surj f"
paulson@13585
   367
by (simp add: bij_def)
paulson@13585
   368
nipkow@26105
   369
lemma bij_betw_imp_inj_on: "bij_betw f A B \<Longrightarrow> inj_on f A"
nipkow@26105
   370
by (simp add: bij_betw_def)
nipkow@26105
   371
nipkow@31438
   372
lemma bij_betw_trans:
nipkow@31438
   373
  "bij_betw f A B \<Longrightarrow> bij_betw g B C \<Longrightarrow> bij_betw (g o f) A C"
nipkow@31438
   374
by(auto simp add:bij_betw_def comp_inj_on)
nipkow@31438
   375
hoelzl@40702
   376
lemma bij_comp: "bij f \<Longrightarrow> bij g \<Longrightarrow> bij (g o f)"
hoelzl@40702
   377
  by (rule bij_betw_trans)
hoelzl@40702
   378
hoelzl@40703
   379
lemma bij_betw_comp_iff:
hoelzl@40703
   380
  "bij_betw f A A' \<Longrightarrow> bij_betw f' A' A'' \<longleftrightarrow> bij_betw (f' o f) A A''"
hoelzl@40703
   381
by(auto simp add: bij_betw_def inj_on_def)
hoelzl@40703
   382
hoelzl@40703
   383
lemma bij_betw_comp_iff2:
hoelzl@40703
   384
  assumes BIJ: "bij_betw f' A' A''" and IM: "f ` A \<le> A'"
hoelzl@40703
   385
  shows "bij_betw f A A' \<longleftrightarrow> bij_betw (f' o f) A A''"
hoelzl@40703
   386
using assms
hoelzl@40703
   387
proof(auto simp add: bij_betw_comp_iff)
hoelzl@40703
   388
  assume *: "bij_betw (f' \<circ> f) A A''"
hoelzl@40703
   389
  thus "bij_betw f A A'"
hoelzl@40703
   390
  using IM
hoelzl@40703
   391
  proof(auto simp add: bij_betw_def)
hoelzl@40703
   392
    assume "inj_on (f' \<circ> f) A"
hoelzl@40703
   393
    thus "inj_on f A" using inj_on_imageI2 by blast
hoelzl@40703
   394
  next
hoelzl@40703
   395
    fix a' assume **: "a' \<in> A'"
hoelzl@40703
   396
    hence "f' a' \<in> A''" using BIJ unfolding bij_betw_def by auto
hoelzl@40703
   397
    then obtain a where 1: "a \<in> A \<and> f'(f a) = f' a'" using *
hoelzl@40703
   398
    unfolding bij_betw_def by force
hoelzl@40703
   399
    hence "f a \<in> A'" using IM by auto
hoelzl@40703
   400
    hence "f a = a'" using BIJ ** 1 unfolding bij_betw_def inj_on_def by auto
hoelzl@40703
   401
    thus "a' \<in> f ` A" using 1 by auto
hoelzl@40703
   402
  qed
hoelzl@40703
   403
qed
hoelzl@40703
   404
nipkow@26105
   405
lemma bij_betw_inv: assumes "bij_betw f A B" shows "EX g. bij_betw g B A"
nipkow@26105
   406
proof -
nipkow@26105
   407
  have i: "inj_on f A" and s: "f ` A = B"
nipkow@26105
   408
    using assms by(auto simp:bij_betw_def)
nipkow@26105
   409
  let ?P = "%b a. a:A \<and> f a = b" let ?g = "%b. The (?P b)"
nipkow@26105
   410
  { fix a b assume P: "?P b a"
nipkow@26105
   411
    hence ex1: "\<exists>a. ?P b a" using s unfolding image_def by blast
nipkow@26105
   412
    hence uex1: "\<exists>!a. ?P b a" by(blast dest:inj_onD[OF i])
nipkow@26105
   413
    hence " ?g b = a" using the1_equality[OF uex1, OF P] P by simp
nipkow@26105
   414
  } note g = this
nipkow@26105
   415
  have "inj_on ?g B"
nipkow@26105
   416
  proof(rule inj_onI)
nipkow@26105
   417
    fix x y assume "x:B" "y:B" "?g x = ?g y"
nipkow@26105
   418
    from s `x:B` obtain a1 where a1: "?P x a1" unfolding image_def by blast
nipkow@26105
   419
    from s `y:B` obtain a2 where a2: "?P y a2" unfolding image_def by blast
nipkow@26105
   420
    from g[OF a1] a1 g[OF a2] a2 `?g x = ?g y` show "x=y" by simp
nipkow@26105
   421
  qed
nipkow@26105
   422
  moreover have "?g ` B = A"
nipkow@26105
   423
  proof(auto simp:image_def)
nipkow@26105
   424
    fix b assume "b:B"
nipkow@26105
   425
    with s obtain a where P: "?P b a" unfolding image_def by blast
nipkow@26105
   426
    thus "?g b \<in> A" using g[OF P] by auto
nipkow@26105
   427
  next
nipkow@26105
   428
    fix a assume "a:A"
nipkow@26105
   429
    then obtain b where P: "?P b a" using s unfolding image_def by blast
nipkow@26105
   430
    then have "b:B" using s unfolding image_def by blast
nipkow@26105
   431
    with g[OF P] show "\<exists>b\<in>B. a = ?g b" by blast
nipkow@26105
   432
  qed
nipkow@26105
   433
  ultimately show ?thesis by(auto simp:bij_betw_def)
nipkow@26105
   434
qed
nipkow@26105
   435
hoelzl@40703
   436
lemma bij_betw_cong:
hoelzl@40703
   437
  "(\<And> a. a \<in> A \<Longrightarrow> f a = g a) \<Longrightarrow> bij_betw f A A' = bij_betw g A A'"
hoelzl@40703
   438
unfolding bij_betw_def inj_on_def by force
hoelzl@40703
   439
hoelzl@40703
   440
lemma bij_betw_id[intro, simp]:
hoelzl@40703
   441
  "bij_betw id A A"
hoelzl@40703
   442
unfolding bij_betw_def id_def by auto
hoelzl@40703
   443
hoelzl@40703
   444
lemma bij_betw_id_iff:
hoelzl@40703
   445
  "bij_betw id A B \<longleftrightarrow> A = B"
hoelzl@40703
   446
by(auto simp add: bij_betw_def)
hoelzl@40703
   447
hoelzl@39075
   448
lemma bij_betw_combine:
hoelzl@39075
   449
  assumes "bij_betw f A B" "bij_betw f C D" "B \<inter> D = {}"
hoelzl@39075
   450
  shows "bij_betw f (A \<union> C) (B \<union> D)"
hoelzl@39075
   451
  using assms unfolding bij_betw_def inj_on_Un image_Un by auto
hoelzl@39075
   452
hoelzl@40703
   453
lemma bij_betw_UNION_chain:
hoelzl@40703
   454
  assumes CH: "\<And> i j. \<lbrakk>i \<in> I; j \<in> I\<rbrakk> \<Longrightarrow> A i \<le> A j \<or> A j \<le> A i" and
hoelzl@40703
   455
         BIJ: "\<And> i. i \<in> I \<Longrightarrow> bij_betw f (A i) (A' i)"
hoelzl@40703
   456
  shows "bij_betw f (\<Union> i \<in> I. A i) (\<Union> i \<in> I. A' i)"
haftmann@49905
   457
proof (unfold bij_betw_def, auto)
hoelzl@40703
   458
  have "\<And> i. i \<in> I \<Longrightarrow> inj_on f (A i)"
hoelzl@40703
   459
  using BIJ bij_betw_def[of f] by auto
hoelzl@40703
   460
  thus "inj_on f (\<Union> i \<in> I. A i)"
hoelzl@40703
   461
  using CH inj_on_UNION_chain[of I A f] by auto
hoelzl@40703
   462
next
hoelzl@40703
   463
  fix i x
hoelzl@40703
   464
  assume *: "i \<in> I" "x \<in> A i"
hoelzl@40703
   465
  hence "f x \<in> A' i" using BIJ bij_betw_def[of f] by auto
hoelzl@40703
   466
  thus "\<exists>j \<in> I. f x \<in> A' j" using * by blast
hoelzl@40703
   467
next
hoelzl@40703
   468
  fix i x'
hoelzl@40703
   469
  assume *: "i \<in> I" "x' \<in> A' i"
hoelzl@40703
   470
  hence "\<exists>x \<in> A i. x' = f x" using BIJ bij_betw_def[of f] by blast
haftmann@49905
   471
  then have "\<exists>j \<in> I. \<exists>x \<in> A j. x' = f x"
haftmann@49905
   472
    using * by blast
haftmann@49905
   473
  then show "x' \<in> f ` (\<Union>x\<in>I. A x)" by (simp add: image_def)
hoelzl@40703
   474
qed
hoelzl@40703
   475
hoelzl@40703
   476
lemma bij_betw_subset:
hoelzl@40703
   477
  assumes BIJ: "bij_betw f A A'" and
hoelzl@40703
   478
          SUB: "B \<le> A" and IM: "f ` B = B'"
hoelzl@40703
   479
  shows "bij_betw f B B'"
hoelzl@40703
   480
using assms
hoelzl@40703
   481
by(unfold bij_betw_def inj_on_def, auto simp add: inj_on_def)
hoelzl@40703
   482
paulson@13585
   483
lemma surj_image_vimage_eq: "surj f ==> f ` (f -` A) = A"
hoelzl@40702
   484
by simp
paulson@13585
   485
hoelzl@42903
   486
lemma surj_vimage_empty:
hoelzl@42903
   487
  assumes "surj f" shows "f -` A = {} \<longleftrightarrow> A = {}"
hoelzl@42903
   488
  using surj_image_vimage_eq[OF `surj f`, of A]
nipkow@44890
   489
  by (intro iffI) fastforce+
hoelzl@42903
   490
paulson@13585
   491
lemma inj_vimage_image_eq: "inj f ==> f -` (f ` A) = A"
paulson@13585
   492
by (simp add: inj_on_def, blast)
paulson@13585
   493
paulson@13585
   494
lemma vimage_subsetD: "surj f ==> f -` B <= A ==> B <= f ` A"
hoelzl@40702
   495
by (blast intro: sym)
paulson@13585
   496
paulson@13585
   497
lemma vimage_subsetI: "inj f ==> B <= f ` A ==> f -` B <= A"
paulson@13585
   498
by (unfold inj_on_def, blast)
paulson@13585
   499
paulson@13585
   500
lemma vimage_subset_eq: "bij f ==> (f -` B <= A) = (B <= f ` A)"
paulson@13585
   501
apply (unfold bij_def)
paulson@13585
   502
apply (blast del: subsetI intro: vimage_subsetI vimage_subsetD)
paulson@13585
   503
done
paulson@13585
   504
Andreas@53927
   505
lemma inj_on_image_eq_iff: "\<lbrakk> inj_on f C; A \<subseteq> C; B \<subseteq> C \<rbrakk> \<Longrightarrow> f ` A = f ` B \<longleftrightarrow> A = B"
Andreas@53927
   506
by(fastforce simp add: inj_on_def)
Andreas@53927
   507
nipkow@31438
   508
lemma inj_on_Un_image_eq_iff: "inj_on f (A \<union> B) \<Longrightarrow> f ` A = f ` B \<longleftrightarrow> A = B"
Andreas@53927
   509
by(erule inj_on_image_eq_iff) simp_all
nipkow@31438
   510
paulson@13585
   511
lemma inj_on_image_Int:
paulson@13585
   512
   "[| inj_on f C;  A<=C;  B<=C |] ==> f`(A Int B) = f`A Int f`B"
paulson@13585
   513
apply (simp add: inj_on_def, blast)
paulson@13585
   514
done
paulson@13585
   515
paulson@13585
   516
lemma inj_on_image_set_diff:
paulson@13585
   517
   "[| inj_on f C;  A<=C;  B<=C |] ==> f`(A-B) = f`A - f`B"
paulson@13585
   518
apply (simp add: inj_on_def, blast)
paulson@13585
   519
done
paulson@13585
   520
paulson@13585
   521
lemma image_Int: "inj f ==> f`(A Int B) = f`A Int f`B"
paulson@13585
   522
by (simp add: inj_on_def, blast)
paulson@13585
   523
paulson@13585
   524
lemma image_set_diff: "inj f ==> f`(A-B) = f`A - f`B"
paulson@13585
   525
by (simp add: inj_on_def, blast)
paulson@13585
   526
paulson@13585
   527
lemma inj_image_mem_iff: "inj f ==> (f a : f`A) = (a : A)"
paulson@13585
   528
by (blast dest: injD)
paulson@13585
   529
paulson@13585
   530
lemma inj_image_subset_iff: "inj f ==> (f`A <= f`B) = (A<=B)"
paulson@13585
   531
by (simp add: inj_on_def, blast)
paulson@13585
   532
paulson@13585
   533
lemma inj_image_eq_iff: "inj f ==> (f`A = f`B) = (A = B)"
paulson@13585
   534
by (blast dest: injD)
paulson@13585
   535
paulson@13585
   536
(*injectivity's required.  Left-to-right inclusion holds even if A is empty*)
paulson@13585
   537
lemma image_INT:
paulson@13585
   538
   "[| inj_on f C;  ALL x:A. B x <= C;  j:A |]
paulson@13585
   539
    ==> f ` (INTER A B) = (INT x:A. f ` B x)"
paulson@13585
   540
apply (simp add: inj_on_def, blast)
paulson@13585
   541
done
paulson@13585
   542
paulson@13585
   543
(*Compare with image_INT: no use of inj_on, and if f is surjective then
paulson@13585
   544
  it doesn't matter whether A is empty*)
paulson@13585
   545
lemma bij_image_INT: "bij f ==> f ` (INTER A B) = (INT x:A. f ` B x)"
paulson@13585
   546
apply (simp add: bij_def)
paulson@13585
   547
apply (simp add: inj_on_def surj_def, blast)
paulson@13585
   548
done
paulson@13585
   549
paulson@13585
   550
lemma surj_Compl_image_subset: "surj f ==> -(f`A) <= f`(-A)"
hoelzl@40702
   551
by auto
paulson@13585
   552
paulson@13585
   553
lemma inj_image_Compl_subset: "inj f ==> f`(-A) <= -(f`A)"
paulson@13585
   554
by (auto simp add: inj_on_def)
paulson@5852
   555
paulson@13585
   556
lemma bij_image_Compl_eq: "bij f ==> f`(-A) = -(f`A)"
paulson@13585
   557
apply (simp add: bij_def)
paulson@13585
   558
apply (rule equalityI)
paulson@13585
   559
apply (simp_all (no_asm_simp) add: inj_image_Compl_subset surj_Compl_image_subset)
paulson@13585
   560
done
paulson@13585
   561
haftmann@41657
   562
lemma inj_vimage_singleton: "inj f \<Longrightarrow> f -` {a} \<subseteq> {THE x. f x = a}"
haftmann@41657
   563
  -- {* The inverse image of a singleton under an injective function
haftmann@41657
   564
         is included in a singleton. *}
haftmann@41657
   565
  apply (auto simp add: inj_on_def)
haftmann@41657
   566
  apply (blast intro: the_equality [symmetric])
haftmann@41657
   567
  done
haftmann@41657
   568
hoelzl@43991
   569
lemma inj_on_vimage_singleton:
hoelzl@43991
   570
  "inj_on f A \<Longrightarrow> f -` {a} \<inter> A \<subseteq> {THE x. x \<in> A \<and> f x = a}"
hoelzl@43991
   571
  by (auto simp add: inj_on_def intro: the_equality [symmetric])
hoelzl@43991
   572
hoelzl@35584
   573
lemma (in ordered_ab_group_add) inj_uminus[simp, intro]: "inj_on uminus A"
hoelzl@35580
   574
  by (auto intro!: inj_onI)
paulson@13585
   575
hoelzl@35584
   576
lemma (in linorder) strict_mono_imp_inj_on: "strict_mono f \<Longrightarrow> inj_on f A"
hoelzl@35584
   577
  by (auto intro!: inj_onI dest: strict_mono_eq)
hoelzl@35584
   578
blanchet@55019
   579
lemma bij_betw_byWitness:
blanchet@55019
   580
assumes LEFT: "\<forall>a \<in> A. f'(f a) = a" and
blanchet@55019
   581
        RIGHT: "\<forall>a' \<in> A'. f(f' a') = a'" and
blanchet@55019
   582
        IM1: "f ` A \<le> A'" and IM2: "f' ` A' \<le> A"
blanchet@55019
   583
shows "bij_betw f A A'"
blanchet@55019
   584
using assms
blanchet@55019
   585
proof(unfold bij_betw_def inj_on_def, safe)
blanchet@55019
   586
  fix a b assume *: "a \<in> A" "b \<in> A" and **: "f a = f b"
blanchet@55019
   587
  have "a = f'(f a) \<and> b = f'(f b)" using * LEFT by simp
blanchet@55019
   588
  with ** show "a = b" by simp
blanchet@55019
   589
next
blanchet@55019
   590
  fix a' assume *: "a' \<in> A'"
blanchet@55019
   591
  hence "f' a' \<in> A" using IM2 by blast
blanchet@55019
   592
  moreover
blanchet@55019
   593
  have "a' = f(f' a')" using * RIGHT by simp
blanchet@55019
   594
  ultimately show "a' \<in> f ` A" by blast
blanchet@55019
   595
qed
blanchet@55019
   596
blanchet@55019
   597
corollary notIn_Un_bij_betw:
blanchet@55019
   598
assumes NIN: "b \<notin> A" and NIN': "f b \<notin> A'" and
blanchet@55019
   599
       BIJ: "bij_betw f A A'"
blanchet@55019
   600
shows "bij_betw f (A \<union> {b}) (A' \<union> {f b})"
blanchet@55019
   601
proof-
blanchet@55019
   602
  have "bij_betw f {b} {f b}"
blanchet@55019
   603
  unfolding bij_betw_def inj_on_def by simp
blanchet@55019
   604
  with assms show ?thesis
blanchet@55019
   605
  using bij_betw_combine[of f A A' "{b}" "{f b}"] by blast
blanchet@55019
   606
qed
blanchet@55019
   607
blanchet@55019
   608
lemma notIn_Un_bij_betw3:
blanchet@55019
   609
assumes NIN: "b \<notin> A" and NIN': "f b \<notin> A'"
blanchet@55019
   610
shows "bij_betw f A A' = bij_betw f (A \<union> {b}) (A' \<union> {f b})"
blanchet@55019
   611
proof
blanchet@55019
   612
  assume "bij_betw f A A'"
blanchet@55019
   613
  thus "bij_betw f (A \<union> {b}) (A' \<union> {f b})"
blanchet@55019
   614
  using assms notIn_Un_bij_betw[of b A f A'] by blast
blanchet@55019
   615
next
blanchet@55019
   616
  assume *: "bij_betw f (A \<union> {b}) (A' \<union> {f b})"
blanchet@55019
   617
  have "f ` A = A'"
blanchet@55019
   618
  proof(auto)
blanchet@55019
   619
    fix a assume **: "a \<in> A"
blanchet@55019
   620
    hence "f a \<in> A' \<union> {f b}" using * unfolding bij_betw_def by blast
blanchet@55019
   621
    moreover
blanchet@55019
   622
    {assume "f a = f b"
blanchet@55019
   623
     hence "a = b" using * ** unfolding bij_betw_def inj_on_def by blast
blanchet@55019
   624
     with NIN ** have False by blast
blanchet@55019
   625
    }
blanchet@55019
   626
    ultimately show "f a \<in> A'" by blast
blanchet@55019
   627
  next
blanchet@55019
   628
    fix a' assume **: "a' \<in> A'"
blanchet@55019
   629
    hence "a' \<in> f`(A \<union> {b})"
blanchet@55019
   630
    using * by (auto simp add: bij_betw_def)
blanchet@55019
   631
    then obtain a where 1: "a \<in> A \<union> {b} \<and> f a = a'" by blast
blanchet@55019
   632
    moreover
blanchet@55019
   633
    {assume "a = b" with 1 ** NIN' have False by blast
blanchet@55019
   634
    }
blanchet@55019
   635
    ultimately have "a \<in> A" by blast
blanchet@55019
   636
    with 1 show "a' \<in> f ` A" by blast
blanchet@55019
   637
  qed
blanchet@55019
   638
  thus "bij_betw f A A'" using * bij_betw_subset[of f "A \<union> {b}" _ A] by blast
blanchet@55019
   639
qed
blanchet@55019
   640
haftmann@41657
   641
paulson@13585
   642
subsection{*Function Updating*}
paulson@13585
   643
haftmann@44277
   644
definition fun_upd :: "('a => 'b) => 'a => 'b => ('a => 'b)" where
haftmann@26147
   645
  "fun_upd f a b == % x. if x=a then b else f x"
haftmann@26147
   646
wenzelm@41229
   647
nonterminal updbinds and updbind
wenzelm@41229
   648
haftmann@26147
   649
syntax
haftmann@26147
   650
  "_updbind" :: "['a, 'a] => updbind"             ("(2_ :=/ _)")
haftmann@26147
   651
  ""         :: "updbind => updbinds"             ("_")
haftmann@26147
   652
  "_updbinds":: "[updbind, updbinds] => updbinds" ("_,/ _")
wenzelm@35115
   653
  "_Update"  :: "['a, updbinds] => 'a"            ("_/'((_)')" [1000, 0] 900)
haftmann@26147
   654
haftmann@26147
   655
translations
wenzelm@35115
   656
  "_Update f (_updbinds b bs)" == "_Update (_Update f b) bs"
wenzelm@35115
   657
  "f(x:=y)" == "CONST fun_upd f x y"
haftmann@26147
   658
haftmann@26147
   659
(* Hint: to define the sum of two functions (or maps), use sum_case.
haftmann@26147
   660
         A nice infix syntax could be defined (in Datatype.thy or below) by
wenzelm@35115
   661
notation
wenzelm@35115
   662
  sum_case  (infixr "'(+')"80)
haftmann@26147
   663
*)
haftmann@26147
   664
paulson@13585
   665
lemma fun_upd_idem_iff: "(f(x:=y) = f) = (f x = y)"
paulson@13585
   666
apply (simp add: fun_upd_def, safe)
paulson@13585
   667
apply (erule subst)
paulson@13585
   668
apply (rule_tac [2] ext, auto)
paulson@13585
   669
done
paulson@13585
   670
wenzelm@45603
   671
lemma fun_upd_idem: "f x = y ==> f(x:=y) = f"
wenzelm@45603
   672
  by (simp only: fun_upd_idem_iff)
paulson@13585
   673
wenzelm@45603
   674
lemma fun_upd_triv [iff]: "f(x := f x) = f"
wenzelm@45603
   675
  by (simp only: fun_upd_idem)
paulson@13585
   676
paulson@13585
   677
lemma fun_upd_apply [simp]: "(f(x:=y))z = (if z=x then y else f z)"
paulson@17084
   678
by (simp add: fun_upd_def)
paulson@13585
   679
paulson@13585
   680
(* fun_upd_apply supersedes these two,   but they are useful
paulson@13585
   681
   if fun_upd_apply is intentionally removed from the simpset *)
paulson@13585
   682
lemma fun_upd_same: "(f(x:=y)) x = y"
paulson@13585
   683
by simp
paulson@13585
   684
paulson@13585
   685
lemma fun_upd_other: "z~=x ==> (f(x:=y)) z = f z"
paulson@13585
   686
by simp
paulson@13585
   687
paulson@13585
   688
lemma fun_upd_upd [simp]: "f(x:=y,x:=z) = f(x:=z)"
nipkow@39302
   689
by (simp add: fun_eq_iff)
paulson@13585
   690
paulson@13585
   691
lemma fun_upd_twist: "a ~= c ==> (m(a:=b))(c:=d) = (m(c:=d))(a:=b)"
paulson@13585
   692
by (rule ext, auto)
paulson@13585
   693
nipkow@15303
   694
lemma inj_on_fun_updI: "\<lbrakk> inj_on f A; y \<notin> f`A \<rbrakk> \<Longrightarrow> inj_on (f(x:=y)) A"
nipkow@44890
   695
by (fastforce simp:inj_on_def image_def)
nipkow@15303
   696
paulson@15510
   697
lemma fun_upd_image:
paulson@15510
   698
     "f(x:=y) ` A = (if x \<in> A then insert y (f ` (A-{x})) else f ` A)"
paulson@15510
   699
by auto
paulson@15510
   700
nipkow@31080
   701
lemma fun_upd_comp: "f \<circ> (g(x := y)) = (f \<circ> g)(x := f y)"
huffman@44921
   702
  by auto
nipkow@31080
   703
nipkow@44744
   704
lemma UNION_fun_upd:
nipkow@44744
   705
  "UNION J (A(i:=B)) = (UNION (J-{i}) A \<union> (if i\<in>J then B else {}))"
nipkow@44744
   706
by (auto split: if_splits)
nipkow@44744
   707
haftmann@26147
   708
haftmann@26147
   709
subsection {* @{text override_on} *}
haftmann@26147
   710
haftmann@44277
   711
definition override_on :: "('a \<Rightarrow> 'b) \<Rightarrow> ('a \<Rightarrow> 'b) \<Rightarrow> 'a set \<Rightarrow> 'a \<Rightarrow> 'b" where
haftmann@26147
   712
  "override_on f g A = (\<lambda>a. if a \<in> A then g a else f a)"
nipkow@13910
   713
nipkow@15691
   714
lemma override_on_emptyset[simp]: "override_on f g {} = f"
nipkow@15691
   715
by(simp add:override_on_def)
nipkow@13910
   716
nipkow@15691
   717
lemma override_on_apply_notin[simp]: "a ~: A ==> (override_on f g A) a = f a"
nipkow@15691
   718
by(simp add:override_on_def)
nipkow@13910
   719
nipkow@15691
   720
lemma override_on_apply_in[simp]: "a : A ==> (override_on f g A) a = g a"
nipkow@15691
   721
by(simp add:override_on_def)
nipkow@13910
   722
haftmann@26147
   723
haftmann@26147
   724
subsection {* @{text swap} *}
paulson@15510
   725
haftmann@44277
   726
definition swap :: "'a \<Rightarrow> 'a \<Rightarrow> ('a \<Rightarrow> 'b) \<Rightarrow> ('a \<Rightarrow> 'b)" where
haftmann@22744
   727
  "swap a b f = f (a := f b, b:= f a)"
paulson@15510
   728
huffman@34101
   729
lemma swap_self [simp]: "swap a a f = f"
nipkow@15691
   730
by (simp add: swap_def)
paulson@15510
   731
paulson@15510
   732
lemma swap_commute: "swap a b f = swap b a f"
paulson@15510
   733
by (rule ext, simp add: fun_upd_def swap_def)
paulson@15510
   734
paulson@15510
   735
lemma swap_nilpotent [simp]: "swap a b (swap a b f) = f"
paulson@15510
   736
by (rule ext, simp add: fun_upd_def swap_def)
paulson@15510
   737
huffman@34145
   738
lemma swap_triple:
huffman@34145
   739
  assumes "a \<noteq> c" and "b \<noteq> c"
huffman@34145
   740
  shows "swap a b (swap b c (swap a b f)) = swap a c f"
nipkow@39302
   741
  using assms by (simp add: fun_eq_iff swap_def)
huffman@34145
   742
huffman@34101
   743
lemma comp_swap: "f \<circ> swap a b g = swap a b (f \<circ> g)"
huffman@34101
   744
by (rule ext, simp add: fun_upd_def swap_def)
huffman@34101
   745
hoelzl@39076
   746
lemma swap_image_eq [simp]:
hoelzl@39076
   747
  assumes "a \<in> A" "b \<in> A" shows "swap a b f ` A = f ` A"
hoelzl@39076
   748
proof -
hoelzl@39076
   749
  have subset: "\<And>f. swap a b f ` A \<subseteq> f ` A"
hoelzl@39076
   750
    using assms by (auto simp: image_iff swap_def)
hoelzl@39076
   751
  then have "swap a b (swap a b f) ` A \<subseteq> (swap a b f) ` A" .
hoelzl@39076
   752
  with subset[of f] show ?thesis by auto
hoelzl@39076
   753
qed
hoelzl@39076
   754
paulson@15510
   755
lemma inj_on_imp_inj_on_swap:
hoelzl@39076
   756
  "\<lbrakk>inj_on f A; a \<in> A; b \<in> A\<rbrakk> \<Longrightarrow> inj_on (swap a b f) A"
hoelzl@39076
   757
  by (simp add: inj_on_def swap_def, blast)
paulson@15510
   758
paulson@15510
   759
lemma inj_on_swap_iff [simp]:
hoelzl@39076
   760
  assumes A: "a \<in> A" "b \<in> A" shows "inj_on (swap a b f) A \<longleftrightarrow> inj_on f A"
hoelzl@39075
   761
proof
paulson@15510
   762
  assume "inj_on (swap a b f) A"
hoelzl@39075
   763
  with A have "inj_on (swap a b (swap a b f)) A"
hoelzl@39075
   764
    by (iprover intro: inj_on_imp_inj_on_swap)
hoelzl@39075
   765
  thus "inj_on f A" by simp
paulson@15510
   766
next
paulson@15510
   767
  assume "inj_on f A"
krauss@34209
   768
  with A show "inj_on (swap a b f) A" by (iprover intro: inj_on_imp_inj_on_swap)
paulson@15510
   769
qed
paulson@15510
   770
hoelzl@39076
   771
lemma surj_imp_surj_swap: "surj f \<Longrightarrow> surj (swap a b f)"
hoelzl@40702
   772
  by simp
paulson@15510
   773
hoelzl@39076
   774
lemma surj_swap_iff [simp]: "surj (swap a b f) \<longleftrightarrow> surj f"
hoelzl@40702
   775
  by simp
haftmann@21547
   776
hoelzl@39076
   777
lemma bij_betw_swap_iff [simp]:
hoelzl@39076
   778
  "\<lbrakk> x \<in> A; y \<in> A \<rbrakk> \<Longrightarrow> bij_betw (swap x y f) A B \<longleftrightarrow> bij_betw f A B"
hoelzl@39076
   779
  by (auto simp: bij_betw_def)
hoelzl@39076
   780
hoelzl@39076
   781
lemma bij_swap_iff [simp]: "bij (swap a b f) \<longleftrightarrow> bij f"
hoelzl@39076
   782
  by simp
hoelzl@39075
   783
wenzelm@36176
   784
hide_const (open) swap
haftmann@21547
   785
haftmann@31949
   786
subsection {* Inversion of injective functions *}
haftmann@31949
   787
nipkow@33057
   788
definition the_inv_into :: "'a set => ('a => 'b) => ('b => 'a)" where
haftmann@44277
   789
  "the_inv_into A f == %x. THE y. y : A & f y = x"
nipkow@32961
   790
nipkow@33057
   791
lemma the_inv_into_f_f:
nipkow@33057
   792
  "[| inj_on f A;  x : A |] ==> the_inv_into A f (f x) = x"
nipkow@33057
   793
apply (simp add: the_inv_into_def inj_on_def)
krauss@34209
   794
apply blast
nipkow@32961
   795
done
nipkow@32961
   796
nipkow@33057
   797
lemma f_the_inv_into_f:
nipkow@33057
   798
  "inj_on f A ==> y : f`A  ==> f (the_inv_into A f y) = y"
nipkow@33057
   799
apply (simp add: the_inv_into_def)
nipkow@32961
   800
apply (rule the1I2)
nipkow@32961
   801
 apply(blast dest: inj_onD)
nipkow@32961
   802
apply blast
nipkow@32961
   803
done
nipkow@32961
   804
nipkow@33057
   805
lemma the_inv_into_into:
nipkow@33057
   806
  "[| inj_on f A; x : f ` A; A <= B |] ==> the_inv_into A f x : B"
nipkow@33057
   807
apply (simp add: the_inv_into_def)
nipkow@32961
   808
apply (rule the1I2)
nipkow@32961
   809
 apply(blast dest: inj_onD)
nipkow@32961
   810
apply blast
nipkow@32961
   811
done
nipkow@32961
   812
nipkow@33057
   813
lemma the_inv_into_onto[simp]:
nipkow@33057
   814
  "inj_on f A ==> the_inv_into A f ` (f ` A) = A"
nipkow@33057
   815
by (fast intro:the_inv_into_into the_inv_into_f_f[symmetric])
nipkow@32961
   816
nipkow@33057
   817
lemma the_inv_into_f_eq:
nipkow@33057
   818
  "[| inj_on f A; f x = y; x : A |] ==> the_inv_into A f y = x"
nipkow@32961
   819
  apply (erule subst)
nipkow@33057
   820
  apply (erule the_inv_into_f_f, assumption)
nipkow@32961
   821
  done
nipkow@32961
   822
nipkow@33057
   823
lemma the_inv_into_comp:
nipkow@32961
   824
  "[| inj_on f (g ` A); inj_on g A; x : f ` g ` A |] ==>
nipkow@33057
   825
  the_inv_into A (f o g) x = (the_inv_into A g o the_inv_into (g ` A) f) x"
nipkow@33057
   826
apply (rule the_inv_into_f_eq)
nipkow@32961
   827
  apply (fast intro: comp_inj_on)
nipkow@33057
   828
 apply (simp add: f_the_inv_into_f the_inv_into_into)
nipkow@33057
   829
apply (simp add: the_inv_into_into)
nipkow@32961
   830
done
nipkow@32961
   831
nipkow@33057
   832
lemma inj_on_the_inv_into:
nipkow@33057
   833
  "inj_on f A \<Longrightarrow> inj_on (the_inv_into A f) (f ` A)"
nipkow@33057
   834
by (auto intro: inj_onI simp: image_def the_inv_into_f_f)
nipkow@32961
   835
nipkow@33057
   836
lemma bij_betw_the_inv_into:
nipkow@33057
   837
  "bij_betw f A B \<Longrightarrow> bij_betw (the_inv_into A f) B A"
nipkow@33057
   838
by (auto simp add: bij_betw_def inj_on_the_inv_into the_inv_into_into)
nipkow@32961
   839
berghofe@32998
   840
abbreviation the_inv :: "('a \<Rightarrow> 'b) \<Rightarrow> ('b \<Rightarrow> 'a)" where
nipkow@33057
   841
  "the_inv f \<equiv> the_inv_into UNIV f"
berghofe@32998
   842
berghofe@32998
   843
lemma the_inv_f_f:
berghofe@32998
   844
  assumes "inj f"
berghofe@32998
   845
  shows "the_inv f (f x) = x" using assms UNIV_I
nipkow@33057
   846
  by (rule the_inv_into_f_f)
berghofe@32998
   847
haftmann@44277
   848
hoelzl@40703
   849
subsection {* Cantor's Paradox *}
hoelzl@40703
   850
blanchet@54147
   851
lemma Cantors_paradox:
hoelzl@40703
   852
  "\<not>(\<exists>f. f ` A = Pow A)"
hoelzl@40703
   853
proof clarify
hoelzl@40703
   854
  fix f assume "f ` A = Pow A" hence *: "Pow A \<le> f ` A" by blast
hoelzl@40703
   855
  let ?X = "{a \<in> A. a \<notin> f a}"
hoelzl@40703
   856
  have "?X \<in> Pow A" unfolding Pow_def by auto
hoelzl@40703
   857
  with * obtain x where "x \<in> A \<and> f x = ?X" by blast
hoelzl@40703
   858
  thus False by best
hoelzl@40703
   859
qed
haftmann@31949
   860
haftmann@40969
   861
subsection {* Setup *} 
haftmann@40969
   862
haftmann@40969
   863
subsubsection {* Proof tools *}
haftmann@22845
   864
haftmann@22845
   865
text {* simplifies terms of the form
haftmann@22845
   866
  f(...,x:=y,...,x:=z,...) to f(...,x:=z,...) *}
haftmann@22845
   867
wenzelm@24017
   868
simproc_setup fun_upd2 ("f(v := w, x := y)") = {* fn _ =>
haftmann@22845
   869
let
haftmann@22845
   870
  fun gen_fun_upd NONE T _ _ = NONE
wenzelm@24017
   871
    | gen_fun_upd (SOME f) T x y = SOME (Const (@{const_name fun_upd}, T) $ f $ x $ y)
haftmann@22845
   872
  fun dest_fun_T1 (Type (_, T :: Ts)) = T
haftmann@22845
   873
  fun find_double (t as Const (@{const_name fun_upd},T) $ f $ x $ y) =
haftmann@22845
   874
    let
haftmann@22845
   875
      fun find (Const (@{const_name fun_upd},T) $ g $ v $ w) =
haftmann@22845
   876
            if v aconv x then SOME g else gen_fun_upd (find g) T v w
haftmann@22845
   877
        | find t = NONE
haftmann@22845
   878
    in (dest_fun_T1 T, gen_fun_upd (find f) T x y) end
wenzelm@24017
   879
wenzelm@51717
   880
  val ss = simpset_of @{context}
wenzelm@51717
   881
wenzelm@51717
   882
  fun proc ctxt ct =
wenzelm@24017
   883
    let
wenzelm@24017
   884
      val t = Thm.term_of ct
wenzelm@24017
   885
    in
wenzelm@24017
   886
      case find_double t of
wenzelm@24017
   887
        (T, NONE) => NONE
wenzelm@24017
   888
      | (T, SOME rhs) =>
wenzelm@27330
   889
          SOME (Goal.prove ctxt [] [] (Logic.mk_equals (t, rhs))
wenzelm@24017
   890
            (fn _ =>
wenzelm@24017
   891
              rtac eq_reflection 1 THEN
wenzelm@24017
   892
              rtac ext 1 THEN
wenzelm@51717
   893
              simp_tac (put_simpset ss ctxt) 1))
wenzelm@24017
   894
    end
wenzelm@24017
   895
in proc end
haftmann@22845
   896
*}
haftmann@22845
   897
haftmann@22845
   898
haftmann@40969
   899
subsubsection {* Functorial structure of types *}
haftmann@40969
   900
wenzelm@48891
   901
ML_file "Tools/enriched_type.ML"
haftmann@40969
   902
haftmann@47488
   903
enriched_type map_fun: map_fun
haftmann@47488
   904
  by (simp_all add: fun_eq_iff)
haftmann@47488
   905
haftmann@47488
   906
enriched_type vimage
haftmann@49739
   907
  by (simp_all add: fun_eq_iff vimage_comp)
haftmann@49739
   908
haftmann@49739
   909
text {* Legacy theorem names *}
haftmann@49739
   910
haftmann@49739
   911
lemmas o_def = comp_def
haftmann@49739
   912
lemmas o_apply = comp_apply
haftmann@49739
   913
lemmas o_assoc = comp_assoc [symmetric]
haftmann@49739
   914
lemmas id_o = id_comp
haftmann@49739
   915
lemmas o_id = comp_id
haftmann@49739
   916
lemmas o_eq_dest = comp_eq_dest
haftmann@49739
   917
lemmas o_eq_elim = comp_eq_elim
haftmann@49739
   918
lemmas image_compose = image_comp
haftmann@49739
   919
lemmas vimage_compose = vimage_comp
haftmann@47488
   920
nipkow@2912
   921
end