(* Title: ZF/ZF_Base.thy
Author: Lawrence C Paulson and Martin D Coen, CU Computer Laboratory
Copyright 1993 University of Cambridge
*)
section \<open>Base of Zermelo-Fraenkel Set Theory\<close>
theory ZF_Base
imports FOL
begin
subsection \<open>Signature\<close>
declare [[eta_contract = false]]
typedecl i
instance i :: "term" ..
axiomatization mem :: "[i, i] \<Rightarrow> o" (infixl "\<in>" 50) \<comment> \<open>membership relation\<close>
and zero :: "i" ("0") \<comment> \<open>the empty set\<close>
and Pow :: "i \<Rightarrow> i" \<comment> \<open>power sets\<close>
and Inf :: "i" \<comment> \<open>infinite set\<close>
and Union :: "i \<Rightarrow> i" ("\<Union>_" [90] 90)
and PrimReplace :: "[i, [i, i] \<Rightarrow> o] \<Rightarrow> i"
abbreviation not_mem :: "[i, i] \<Rightarrow> o" (infixl "\<notin>" 50) \<comment> \<open>negated membership relation\<close>
where "x \<notin> y \<equiv> \<not> (x \<in> y)"
subsection \<open>Bounded Quantifiers\<close>
definition Ball :: "[i, i \<Rightarrow> o] \<Rightarrow> o"
where "Ball(A, P) \<equiv> \<forall>x. x\<in>A \<longrightarrow> P(x)"
definition Bex :: "[i, i \<Rightarrow> o] \<Rightarrow> o"
where "Bex(A, P) \<equiv> \<exists>x. x\<in>A \<and> P(x)"
syntax
"_Ball" :: "[pttrn, i, o] \<Rightarrow> o" ("(3\<forall>_\<in>_./ _)" 10)
"_Bex" :: "[pttrn, i, o] \<Rightarrow> o" ("(3\<exists>_\<in>_./ _)" 10)
translations
"\<forall>x\<in>A. P" \<rightleftharpoons> "CONST Ball(A, \<lambda>x. P)"
"\<exists>x\<in>A. P" \<rightleftharpoons> "CONST Bex(A, \<lambda>x. P)"
subsection \<open>Variations on Replacement\<close>
(* Derived form of replacement, restricting P to its functional part.
The resulting set (for functional P) is the same as with
PrimReplace, but the rules are simpler. *)
definition Replace :: "[i, [i, i] \<Rightarrow> o] \<Rightarrow> i"
where "Replace(A,P) == PrimReplace(A, %x y. (\<exists>!z. P(x,z)) & P(x,y))"
syntax
"_Replace" :: "[pttrn, pttrn, i, o] => i" ("(1{_ ./ _ \<in> _, _})")
translations
"{y. x\<in>A, Q}" \<rightleftharpoons> "CONST Replace(A, \<lambda>x y. Q)"
(* Functional form of replacement -- analgous to ML's map functional *)
definition RepFun :: "[i, i \<Rightarrow> i] \<Rightarrow> i"
where "RepFun(A,f) == {y . x\<in>A, y=f(x)}"
syntax
"_RepFun" :: "[i, pttrn, i] => i" ("(1{_ ./ _ \<in> _})" [51,0,51])
translations
"{b. x\<in>A}" \<rightleftharpoons> "CONST RepFun(A, \<lambda>x. b)"
(* Separation and Pairing can be derived from the Replacement
and Powerset Axioms using the following definitions. *)
definition Collect :: "[i, i \<Rightarrow> o] \<Rightarrow> i"
where "Collect(A,P) == {y . x\<in>A, x=y & P(x)}"
syntax
"_Collect" :: "[pttrn, i, o] \<Rightarrow> i" ("(1{_ \<in> _ ./ _})")
translations
"{x\<in>A. P}" \<rightleftharpoons> "CONST Collect(A, \<lambda>x. P)"
subsection \<open>General union and intersection\<close>
definition Inter :: "i => i" ("\<Inter>_" [90] 90)
where "\<Inter>(A) == { x\<in>\<Union>(A) . \<forall>y\<in>A. x\<in>y}"
syntax
"_UNION" :: "[pttrn, i, i] => i" ("(3\<Union>_\<in>_./ _)" 10)
"_INTER" :: "[pttrn, i, i] => i" ("(3\<Inter>_\<in>_./ _)" 10)
translations
"\<Union>x\<in>A. B" == "CONST Union({B. x\<in>A})"
"\<Inter>x\<in>A. B" == "CONST Inter({B. x\<in>A})"
subsection \<open>Finite sets and binary operations\<close>
(*Unordered pairs (Upair) express binary union/intersection and cons;
set enumerations translate as {a,...,z} = cons(a,...,cons(z,0)...)*)
definition Upair :: "[i, i] => i"
where "Upair(a,b) == {y. x\<in>Pow(Pow(0)), (x=0 & y=a) | (x=Pow(0) & y=b)}"
definition Subset :: "[i, i] \<Rightarrow> o" (infixl "\<subseteq>" 50) \<comment> \<open>subset relation\<close>
where subset_def: "A \<subseteq> B \<equiv> \<forall>x\<in>A. x\<in>B"
definition Diff :: "[i, i] \<Rightarrow> i" (infixl "-" 65) \<comment> \<open>set difference\<close>
where "A - B == { x\<in>A . ~(x\<in>B) }"
definition Un :: "[i, i] \<Rightarrow> i" (infixl "\<union>" 65) \<comment> \<open>binary union\<close>
where "A \<union> B == \<Union>(Upair(A,B))"
definition Int :: "[i, i] \<Rightarrow> i" (infixl "\<inter>" 70) \<comment> \<open>binary intersection\<close>
where "A \<inter> B == \<Inter>(Upair(A,B))"
definition cons :: "[i, i] => i"
where "cons(a,A) == Upair(a,a) \<union> A"
definition succ :: "i => i"
where "succ(i) == cons(i, i)"
nonterminal "is"
syntax
"" :: "i \<Rightarrow> is" ("_")
"_Enum" :: "[i, is] \<Rightarrow> is" ("_,/ _")
"_Finset" :: "is \<Rightarrow> i" ("{(_)}")
translations
"{x, xs}" == "CONST cons(x, {xs})"
"{x}" == "CONST cons(x, 0)"
subsection \<open>Axioms\<close>
(* ZF axioms -- see Suppes p.238
Axioms for Union, Pow and Replace state existence only,
uniqueness is derivable using extensionality. *)
axiomatization
where
extension: "A = B \<longleftrightarrow> A \<subseteq> B \<and> B \<subseteq> A" and
Union_iff: "A \<in> \<Union>(C) \<longleftrightarrow> (\<exists>B\<in>C. A\<in>B)" and
Pow_iff: "A \<in> Pow(B) \<longleftrightarrow> A \<subseteq> B" and
(*We may name this set, though it is not uniquely defined.*)
infinity: "0 \<in> Inf \<and> (\<forall>y\<in>Inf. succ(y) \<in> Inf)" and
(*This formulation facilitates case analysis on A.*)
foundation: "A = 0 \<or> (\<exists>x\<in>A. \<forall>y\<in>x. y\<notin>A)" and
(*Schema axiom since predicate P is a higher-order variable*)
replacement: "(\<forall>x\<in>A. \<forall>y z. P(x,y) \<and> P(x,z) \<longrightarrow> y = z) \<Longrightarrow>
b \<in> PrimReplace(A,P) \<longleftrightarrow> (\<exists>x\<in>A. P(x,b))"
subsection \<open>Definite descriptions -- via Replace over the set "1"\<close>
definition The :: "(i \<Rightarrow> o) \<Rightarrow> i" (binder "THE " 10)
where the_def: "The(P) == \<Union>({y . x \<in> {0}, P(y)})"
definition If :: "[o, i, i] \<Rightarrow> i" ("(if (_)/ then (_)/ else (_))" [10] 10)
where if_def: "if P then a else b == THE z. P & z=a | ~P & z=b"
abbreviation (input)
old_if :: "[o, i, i] => i" ("if '(_,_,_')")
where "if(P,a,b) == If(P,a,b)"
subsection \<open>Ordered Pairing\<close>
(* this "symmetric" definition works better than {{a}, {a,b}} *)
definition Pair :: "[i, i] => i"
where "Pair(a,b) == {{a,a}, {a,b}}"
definition fst :: "i \<Rightarrow> i"
where "fst(p) == THE a. \<exists>b. p = Pair(a, b)"
definition snd :: "i \<Rightarrow> i"
where "snd(p) == THE b. \<exists>a. p = Pair(a, b)"
definition split :: "[[i, i] \<Rightarrow> 'a, i] \<Rightarrow> 'a::{}" \<comment> \<open>for pattern-matching\<close>
where "split(c) == \<lambda>p. c(fst(p), snd(p))"
(* Patterns -- extends pre-defined type "pttrn" used in abstractions *)
nonterminal patterns
syntax
"_pattern" :: "patterns => pttrn" ("\<langle>_\<rangle>")
"" :: "pttrn => patterns" ("_")
"_patterns" :: "[pttrn, patterns] => patterns" ("_,/_")
"_Tuple" :: "[i, is] => i" ("\<langle>(_,/ _)\<rangle>")
translations
"\<langle>x, y, z\<rangle>" == "\<langle>x, \<langle>y, z\<rangle>\<rangle>"
"\<langle>x, y\<rangle>" == "CONST Pair(x, y)"
"\<lambda>\<langle>x,y,zs\<rangle>.b" == "CONST split(\<lambda>x \<langle>y,zs\<rangle>.b)"
"\<lambda>\<langle>x,y\<rangle>.b" == "CONST split(\<lambda>x y. b)"
definition Sigma :: "[i, i \<Rightarrow> i] \<Rightarrow> i"
where "Sigma(A,B) == \<Union>x\<in>A. \<Union>y\<in>B(x). {\<langle>x,y\<rangle>}"
abbreviation cart_prod :: "[i, i] => i" (infixr "\<times>" 80) \<comment> \<open>Cartesian product\<close>
where "A \<times> B \<equiv> Sigma(A, \<lambda>_. B)"
subsection \<open>Relations and Functions\<close>
(*converse of relation r, inverse of function*)
definition converse :: "i \<Rightarrow> i"
where "converse(r) == {z. w\<in>r, \<exists>x y. w=\<langle>x,y\<rangle> \<and> z=\<langle>y,x\<rangle>}"
definition domain :: "i \<Rightarrow> i"
where "domain(r) == {x. w\<in>r, \<exists>y. w=\<langle>x,y\<rangle>}"
definition range :: "i \<Rightarrow> i"
where "range(r) == domain(converse(r))"
definition field :: "i \<Rightarrow> i"
where "field(r) == domain(r) \<union> range(r)"
definition relation :: "i \<Rightarrow> o" \<comment> \<open>recognizes sets of pairs\<close>
where "relation(r) == \<forall>z\<in>r. \<exists>x y. z = \<langle>x,y\<rangle>"
definition "function" :: "i \<Rightarrow> o" \<comment> \<open>recognizes functions; can have non-pairs\<close>
where "function(r) == \<forall>x y. \<langle>x,y\<rangle> \<in> r \<longrightarrow> (\<forall>y'. \<langle>x,y'\<rangle> \<in> r \<longrightarrow> y = y')"
definition Image :: "[i, i] \<Rightarrow> i" (infixl "``" 90) \<comment> \<open>image\<close>
where image_def: "r `` A == {y \<in> range(r). \<exists>x\<in>A. \<langle>x,y\<rangle> \<in> r}"
definition vimage :: "[i, i] \<Rightarrow> i" (infixl "-``" 90) \<comment> \<open>inverse image\<close>
where vimage_def: "r -`` A == converse(r)``A"
(* Restrict the relation r to the domain A *)
definition restrict :: "[i, i] \<Rightarrow> i"
where "restrict(r,A) == {z \<in> r. \<exists>x\<in>A. \<exists>y. z = \<langle>x,y\<rangle>}"
(* Abstraction, application and Cartesian product of a family of sets *)
definition Lambda :: "[i, i \<Rightarrow> i] \<Rightarrow> i"
where lam_def: "Lambda(A,b) == {\<langle>x,b(x)\<rangle>. x\<in>A}"
definition "apply" :: "[i, i] \<Rightarrow> i" (infixl "`" 90) \<comment> \<open>function application\<close>
where "f`a == \<Union>(f``{a})"
definition Pi :: "[i, i \<Rightarrow> i] \<Rightarrow> i"
where "Pi(A,B) == {f\<in>Pow(Sigma(A,B)). A\<subseteq>domain(f) & function(f)}"
abbreviation function_space :: "[i, i] \<Rightarrow> i" (infixr "->" 60) \<comment> \<open>function space\<close>
where "A -> B \<equiv> Pi(A, \<lambda>_. B)"
(* binder syntax *)
syntax
"_PROD" :: "[pttrn, i, i] => i" ("(3\<Prod>_\<in>_./ _)" 10)
"_SUM" :: "[pttrn, i, i] => i" ("(3\<Sum>_\<in>_./ _)" 10)
"_lam" :: "[pttrn, i, i] => i" ("(3\<lambda>_\<in>_./ _)" 10)
translations
"\<Prod>x\<in>A. B" == "CONST Pi(A, \<lambda>x. B)"
"\<Sum>x\<in>A. B" == "CONST Sigma(A, \<lambda>x. B)"
"\<lambda>x\<in>A. f" == "CONST Lambda(A, \<lambda>x. f)"
subsection \<open>ASCII syntax\<close>
notation (ASCII)
cart_prod (infixr "*" 80) and
Int (infixl "Int" 70) and
Un (infixl "Un" 65) and
function_space (infixr "\<rightarrow>" 60) and
Subset (infixl "<=" 50) and
mem (infixl ":" 50) and
not_mem (infixl "~:" 50)
syntax (ASCII)
"_Ball" :: "[pttrn, i, o] => o" ("(3ALL _:_./ _)" 10)
"_Bex" :: "[pttrn, i, o] => o" ("(3EX _:_./ _)" 10)
"_Collect" :: "[pttrn, i, o] => i" ("(1{_: _ ./ _})")
"_Replace" :: "[pttrn, pttrn, i, o] => i" ("(1{_ ./ _: _, _})")
"_RepFun" :: "[i, pttrn, i] => i" ("(1{_ ./ _: _})" [51,0,51])
"_UNION" :: "[pttrn, i, i] => i" ("(3UN _:_./ _)" 10)
"_INTER" :: "[pttrn, i, i] => i" ("(3INT _:_./ _)" 10)
"_PROD" :: "[pttrn, i, i] => i" ("(3PROD _:_./ _)" 10)
"_SUM" :: "[pttrn, i, i] => i" ("(3SUM _:_./ _)" 10)
"_lam" :: "[pttrn, i, i] => i" ("(3lam _:_./ _)" 10)
"_Tuple" :: "[i, is] => i" ("<(_,/ _)>")
"_pattern" :: "patterns => pttrn" ("<_>")
subsection \<open>Substitution\<close>
(*Useful examples: singletonI RS subst_elem, subst_elem RSN (2,IntI) *)
lemma subst_elem: "[| b\<in>A; a=b |] ==> a\<in>A"
by (erule ssubst, assumption)
subsection\<open>Bounded universal quantifier\<close>
lemma ballI [intro!]: "[| !!x. x\<in>A ==> P(x) |] ==> \<forall>x\<in>A. P(x)"
by (simp add: Ball_def)
lemmas strip = impI allI ballI
lemma bspec [dest?]: "[| \<forall>x\<in>A. P(x); x: A |] ==> P(x)"
by (simp add: Ball_def)
(*Instantiates x first: better for automatic theorem proving?*)
lemma rev_ballE [elim]:
"[| \<forall>x\<in>A. P(x); x\<notin>A ==> Q; P(x) ==> Q |] ==> Q"
by (simp add: Ball_def, blast)
lemma ballE: "[| \<forall>x\<in>A. P(x); P(x) ==> Q; x\<notin>A ==> Q |] ==> Q"
by blast
(*Used in the datatype package*)
lemma rev_bspec: "[| x: A; \<forall>x\<in>A. P(x) |] ==> P(x)"
by (simp add: Ball_def)
(*Trival rewrite rule; @{term"(\<forall>x\<in>A.P)<->P"} holds only if A is nonempty!*)
lemma ball_triv [simp]: "(\<forall>x\<in>A. P) <-> ((\<exists>x. x\<in>A) \<longrightarrow> P)"
by (simp add: Ball_def)
(*Congruence rule for rewriting*)
lemma ball_cong [cong]:
"[| A=A'; !!x. x\<in>A' ==> P(x) <-> P'(x) |] ==> (\<forall>x\<in>A. P(x)) <-> (\<forall>x\<in>A'. P'(x))"
by (simp add: Ball_def)
lemma atomize_ball:
"(!!x. x \<in> A ==> P(x)) == Trueprop (\<forall>x\<in>A. P(x))"
by (simp only: Ball_def atomize_all atomize_imp)
lemmas [symmetric, rulify] = atomize_ball
and [symmetric, defn] = atomize_ball
subsection\<open>Bounded existential quantifier\<close>
lemma bexI [intro]: "[| P(x); x: A |] ==> \<exists>x\<in>A. P(x)"
by (simp add: Bex_def, blast)
(*The best argument order when there is only one @{term"x\<in>A"}*)
lemma rev_bexI: "[| x\<in>A; P(x) |] ==> \<exists>x\<in>A. P(x)"
by blast
(*Not of the general form for such rules. The existential quanitifer becomes universal. *)
lemma bexCI: "[| \<forall>x\<in>A. ~P(x) ==> P(a); a: A |] ==> \<exists>x\<in>A. P(x)"
by blast
lemma bexE [elim!]: "[| \<exists>x\<in>A. P(x); !!x. [| x\<in>A; P(x) |] ==> Q |] ==> Q"
by (simp add: Bex_def, blast)
(*We do not even have @{term"(\<exists>x\<in>A. True) <-> True"} unless @{term"A" is nonempty!!*)
lemma bex_triv [simp]: "(\<exists>x\<in>A. P) <-> ((\<exists>x. x\<in>A) & P)"
by (simp add: Bex_def)
lemma bex_cong [cong]:
"[| A=A'; !!x. x\<in>A' ==> P(x) <-> P'(x) |]
==> (\<exists>x\<in>A. P(x)) <-> (\<exists>x\<in>A'. P'(x))"
by (simp add: Bex_def cong: conj_cong)
subsection\<open>Rules for subsets\<close>
lemma subsetI [intro!]:
"(!!x. x\<in>A ==> x\<in>B) ==> A \<subseteq> B"
by (simp add: subset_def)
(*Rule in Modus Ponens style [was called subsetE] *)
lemma subsetD [elim]: "[| A \<subseteq> B; c\<in>A |] ==> c\<in>B"
apply (unfold subset_def)
apply (erule bspec, assumption)
done
(*Classical elimination rule*)
lemma subsetCE [elim]:
"[| A \<subseteq> B; c\<notin>A ==> P; c\<in>B ==> P |] ==> P"
by (simp add: subset_def, blast)
(*Sometimes useful with premises in this order*)
lemma rev_subsetD: "[| c\<in>A; A<=B |] ==> c\<in>B"
by blast
lemma contra_subsetD: "[| A \<subseteq> B; c \<notin> B |] ==> c \<notin> A"
by blast
lemma rev_contra_subsetD: "[| c \<notin> B; A \<subseteq> B |] ==> c \<notin> A"
by blast
lemma subset_refl [simp]: "A \<subseteq> A"
by blast
lemma subset_trans: "[| A<=B; B<=C |] ==> A<=C"
by blast
(*Useful for proving A<=B by rewriting in some cases*)
lemma subset_iff:
"A<=B <-> (\<forall>x. x\<in>A \<longrightarrow> x\<in>B)"
apply (unfold subset_def Ball_def)
apply (rule iff_refl)
done
text\<open>For calculations\<close>
declare subsetD [trans] rev_subsetD [trans] subset_trans [trans]
subsection\<open>Rules for equality\<close>
(*Anti-symmetry of the subset relation*)
lemma equalityI [intro]: "[| A \<subseteq> B; B \<subseteq> A |] ==> A = B"
by (rule extension [THEN iffD2], rule conjI)
lemma equality_iffI: "(!!x. x\<in>A <-> x\<in>B) ==> A = B"
by (rule equalityI, blast+)
lemmas equalityD1 = extension [THEN iffD1, THEN conjunct1]
lemmas equalityD2 = extension [THEN iffD1, THEN conjunct2]
lemma equalityE: "[| A = B; [| A<=B; B<=A |] ==> P |] ==> P"
by (blast dest: equalityD1 equalityD2)
lemma equalityCE:
"[| A = B; [| c\<in>A; c\<in>B |] ==> P; [| c\<notin>A; c\<notin>B |] ==> P |] ==> P"
by (erule equalityE, blast)
lemma equality_iffD:
"A = B ==> (!!x. x \<in> A <-> x \<in> B)"
by auto
subsection\<open>Rules for Replace -- the derived form of replacement\<close>
lemma Replace_iff:
"b \<in> {y. x\<in>A, P(x,y)} <-> (\<exists>x\<in>A. P(x,b) & (\<forall>y. P(x,y) \<longrightarrow> y=b))"
apply (unfold Replace_def)
apply (rule replacement [THEN iff_trans], blast+)
done
(*Introduction; there must be a unique y such that P(x,y), namely y=b. *)
lemma ReplaceI [intro]:
"[| P(x,b); x: A; !!y. P(x,y) ==> y=b |] ==>
b \<in> {y. x\<in>A, P(x,y)}"
by (rule Replace_iff [THEN iffD2], blast)
(*Elimination; may asssume there is a unique y such that P(x,y), namely y=b. *)
lemma ReplaceE:
"[| b \<in> {y. x\<in>A, P(x,y)};
!!x. [| x: A; P(x,b); \<forall>y. P(x,y)\<longrightarrow>y=b |] ==> R
|] ==> R"
by (rule Replace_iff [THEN iffD1, THEN bexE], simp+)
(*As above but without the (generally useless) 3rd assumption*)
lemma ReplaceE2 [elim!]:
"[| b \<in> {y. x\<in>A, P(x,y)};
!!x. [| x: A; P(x,b) |] ==> R
|] ==> R"
by (erule ReplaceE, blast)
lemma Replace_cong [cong]:
"[| A=B; !!x y. x\<in>B ==> P(x,y) <-> Q(x,y) |] ==>
Replace(A,P) = Replace(B,Q)"
apply (rule equality_iffI)
apply (simp add: Replace_iff)
done
subsection\<open>Rules for RepFun\<close>
lemma RepFunI: "a \<in> A ==> f(a) \<in> {f(x). x\<in>A}"
by (simp add: RepFun_def Replace_iff, blast)
(*Useful for coinduction proofs*)
lemma RepFun_eqI [intro]: "[| b=f(a); a \<in> A |] ==> b \<in> {f(x). x\<in>A}"
apply (erule ssubst)
apply (erule RepFunI)
done
lemma RepFunE [elim!]:
"[| b \<in> {f(x). x\<in>A};
!!x.[| x\<in>A; b=f(x) |] ==> P |] ==>
P"
by (simp add: RepFun_def Replace_iff, blast)
lemma RepFun_cong [cong]:
"[| A=B; !!x. x\<in>B ==> f(x)=g(x) |] ==> RepFun(A,f) = RepFun(B,g)"
by (simp add: RepFun_def)
lemma RepFun_iff [simp]: "b \<in> {f(x). x\<in>A} <-> (\<exists>x\<in>A. b=f(x))"
by (unfold Bex_def, blast)
lemma triv_RepFun [simp]: "{x. x\<in>A} = A"
by blast
subsection\<open>Rules for Collect -- forming a subset by separation\<close>
(*Separation is derivable from Replacement*)
lemma separation [simp]: "a \<in> {x\<in>A. P(x)} <-> a\<in>A & P(a)"
by (unfold Collect_def, blast)
lemma CollectI [intro!]: "[| a\<in>A; P(a) |] ==> a \<in> {x\<in>A. P(x)}"
by simp
lemma CollectE [elim!]: "[| a \<in> {x\<in>A. P(x)}; [| a\<in>A; P(a) |] ==> R |] ==> R"
by simp
lemma CollectD1: "a \<in> {x\<in>A. P(x)} ==> a\<in>A"
by (erule CollectE, assumption)
lemma CollectD2: "a \<in> {x\<in>A. P(x)} ==> P(a)"
by (erule CollectE, assumption)
lemma Collect_cong [cong]:
"[| A=B; !!x. x\<in>B ==> P(x) <-> Q(x) |]
==> Collect(A, %x. P(x)) = Collect(B, %x. Q(x))"
by (simp add: Collect_def)
subsection\<open>Rules for Unions\<close>
declare Union_iff [simp]
(*The order of the premises presupposes that C is rigid; A may be flexible*)
lemma UnionI [intro]: "[| B: C; A: B |] ==> A: \<Union>(C)"
by (simp, blast)
lemma UnionE [elim!]: "[| A \<in> \<Union>(C); !!B.[| A: B; B: C |] ==> R |] ==> R"
by (simp, blast)
subsection\<open>Rules for Unions of families\<close>
(* @{term"\<Union>x\<in>A. B(x)"} abbreviates @{term"\<Union>({B(x). x\<in>A})"} *)
lemma UN_iff [simp]: "b \<in> (\<Union>x\<in>A. B(x)) <-> (\<exists>x\<in>A. b \<in> B(x))"
by (simp add: Bex_def, blast)
(*The order of the premises presupposes that A is rigid; b may be flexible*)
lemma UN_I: "[| a: A; b: B(a) |] ==> b: (\<Union>x\<in>A. B(x))"
by (simp, blast)
lemma UN_E [elim!]:
"[| b \<in> (\<Union>x\<in>A. B(x)); !!x.[| x: A; b: B(x) |] ==> R |] ==> R"
by blast
lemma UN_cong:
"[| A=B; !!x. x\<in>B ==> C(x)=D(x) |] ==> (\<Union>x\<in>A. C(x)) = (\<Union>x\<in>B. D(x))"
by simp
(*No "Addcongs [UN_cong]" because @{term\<Union>} is a combination of constants*)
(* UN_E appears before UnionE so that it is tried first, to avoid expensive
calls to hyp_subst_tac. Cannot include UN_I as it is unsafe: would enlarge
the search space.*)
subsection\<open>Rules for the empty set\<close>
(*The set @{term"{x\<in>0. False}"} is empty; by foundation it equals 0
See Suppes, page 21.*)
lemma not_mem_empty [simp]: "a \<notin> 0"
apply (cut_tac foundation)
apply (best dest: equalityD2)
done
lemmas emptyE [elim!] = not_mem_empty [THEN notE]
lemma empty_subsetI [simp]: "0 \<subseteq> A"
by blast
lemma equals0I: "[| !!y. y\<in>A ==> False |] ==> A=0"
by blast
lemma equals0D [dest]: "A=0 ==> a \<notin> A"
by blast
declare sym [THEN equals0D, dest]
lemma not_emptyI: "a\<in>A ==> A \<noteq> 0"
by blast
lemma not_emptyE: "[| A \<noteq> 0; !!x. x\<in>A ==> R |] ==> R"
by blast
subsection\<open>Rules for Inter\<close>
(*Not obviously useful for proving InterI, InterD, InterE*)
lemma Inter_iff: "A \<in> \<Inter>(C) <-> (\<forall>x\<in>C. A: x) & C\<noteq>0"
by (simp add: Inter_def Ball_def, blast)
(* Intersection is well-behaved only if the family is non-empty! *)
lemma InterI [intro!]:
"[| !!x. x: C ==> A: x; C\<noteq>0 |] ==> A \<in> \<Inter>(C)"
by (simp add: Inter_iff)
(*A "destruct" rule -- every B in C contains A as an element, but
A\<in>B can hold when B\<in>C does not! This rule is analogous to "spec". *)
lemma InterD [elim, Pure.elim]: "[| A \<in> \<Inter>(C); B \<in> C |] ==> A \<in> B"
by (unfold Inter_def, blast)
(*"Classical" elimination rule -- does not require exhibiting @{term"B\<in>C"} *)
lemma InterE [elim]:
"[| A \<in> \<Inter>(C); B\<notin>C ==> R; A\<in>B ==> R |] ==> R"
by (simp add: Inter_def, blast)
subsection\<open>Rules for Intersections of families\<close>
(* @{term"\<Inter>x\<in>A. B(x)"} abbreviates @{term"\<Inter>({B(x). x\<in>A})"} *)
lemma INT_iff: "b \<in> (\<Inter>x\<in>A. B(x)) <-> (\<forall>x\<in>A. b \<in> B(x)) & A\<noteq>0"
by (force simp add: Inter_def)
lemma INT_I: "[| !!x. x: A ==> b: B(x); A\<noteq>0 |] ==> b: (\<Inter>x\<in>A. B(x))"
by blast
lemma INT_E: "[| b \<in> (\<Inter>x\<in>A. B(x)); a: A |] ==> b \<in> B(a)"
by blast
lemma INT_cong:
"[| A=B; !!x. x\<in>B ==> C(x)=D(x) |] ==> (\<Inter>x\<in>A. C(x)) = (\<Inter>x\<in>B. D(x))"
by simp
(*No "Addcongs [INT_cong]" because @{term\<Inter>} is a combination of constants*)
subsection\<open>Rules for Powersets\<close>
lemma PowI: "A \<subseteq> B ==> A \<in> Pow(B)"
by (erule Pow_iff [THEN iffD2])
lemma PowD: "A \<in> Pow(B) ==> A<=B"
by (erule Pow_iff [THEN iffD1])
declare Pow_iff [iff]
lemmas Pow_bottom = empty_subsetI [THEN PowI] \<comment>\<open>@{term"0 \<in> Pow(B)"}\<close>
lemmas Pow_top = subset_refl [THEN PowI] \<comment>\<open>@{term"A \<in> Pow(A)"}\<close>
subsection\<open>Cantor's Theorem: There is no surjection from a set to its powerset.\<close>
(*The search is undirected. Allowing redundant introduction rules may
make it diverge. Variable b represents ANY map, such as
(lam x\<in>A.b(x)): A->Pow(A). *)
lemma cantor: "\<exists>S \<in> Pow(A). \<forall>x\<in>A. b(x) \<noteq> S"
by (best elim!: equalityCE del: ReplaceI RepFun_eqI)
end