(* Title: ZF/ZF.thy
Author: Lawrence C Paulson and Martin D Coen, CU Computer Laboratory
Copyright 1993 University of Cambridge
*)
header{*Zermelo-Fraenkel Set Theory*}
theory ZF imports FOL begin
ML {* Unsynchronized.reset eta_contract *}
global
typedecl i
arities i :: "term"
consts
"0" :: "i" ("0") --{*the empty set*}
Pow :: "i => i" --{*power sets*}
Inf :: "i" --{*infinite set*}
text {*Bounded Quantifiers *}
consts
Ball :: "[i, i => o] => o"
Bex :: "[i, i => o] => o"
text {*General Union and Intersection *}
consts
Union :: "i => i"
Inter :: "i => i"
text {*Variations on Replacement *}
consts
PrimReplace :: "[i, [i, i] => o] => i"
Replace :: "[i, [i, i] => o] => i"
RepFun :: "[i, i => i] => i"
Collect :: "[i, i => o] => i"
text{*Definite descriptions -- via Replace over the set "1"*}
consts
The :: "(i => o) => i" (binder "THE " 10)
If :: "[o, i, i] => i" ("(if (_)/ then (_)/ else (_))" [10] 10)
abbreviation (input)
old_if :: "[o, i, i] => i" ("if '(_,_,_')") where
"if(P,a,b) == If(P,a,b)"
text {*Finite Sets *}
consts
Upair :: "[i, i] => i"
cons :: "[i, i] => i"
succ :: "i => i"
text {*Ordered Pairing *}
consts
Pair :: "[i, i] => i"
fst :: "i => i"
snd :: "i => i"
split :: "[[i, i] => 'a, i] => 'a::{}" --{*for pattern-matching*}
text {*Sigma and Pi Operators *}
consts
Sigma :: "[i, i => i] => i"
Pi :: "[i, i => i] => i"
text {*Relations and Functions *}
consts
"domain" :: "i => i"
range :: "i => i"
field :: "i => i"
converse :: "i => i"
relation :: "i => o" --{*recognizes sets of pairs*}
"function" :: "i => o" --{*recognizes functions; can have non-pairs*}
Lambda :: "[i, i => i] => i"
restrict :: "[i, i] => i"
text {*Infixes in order of decreasing precedence *}
consts
Image :: "[i, i] => i" (infixl "``" 90) --{*image*}
vimage :: "[i, i] => i" (infixl "-``" 90) --{*inverse image*}
"apply" :: "[i, i] => i" (infixl "`" 90) --{*function application*}
"Int" :: "[i, i] => i" (infixl "Int" 70) --{*binary intersection*}
"Un" :: "[i, i] => i" (infixl "Un" 65) --{*binary union*}
Diff :: "[i, i] => i" (infixl "-" 65) --{*set difference*}
Subset :: "[i, i] => o" (infixl "<=" 50) --{*subset relation*}
mem :: "[i, i] => o" (infixl ":" 50) --{*membership relation*}
abbreviation
not_mem :: "[i, i] => o" (infixl "~:" 50) --{*negated membership relation*}
where "x ~: y == ~ (x : y)"
abbreviation
cart_prod :: "[i, i] => i" (infixr "*" 80) --{*Cartesian product*}
where "A * B == Sigma(A, %_. B)"
abbreviation
function_space :: "[i, i] => i" (infixr "->" 60) --{*function space*}
where "A -> B == Pi(A, %_. B)"
nonterminals "is" patterns
syntax
"" :: "i => is" ("_")
"_Enum" :: "[i, is] => is" ("_,/ _")
"_Finset" :: "is => i" ("{(_)}")
"_Tuple" :: "[i, is] => i" ("<(_,/ _)>")
"_Collect" :: "[pttrn, i, o] => i" ("(1{_: _ ./ _})")
"_Replace" :: "[pttrn, pttrn, i, o] => i" ("(1{_ ./ _: _, _})")
"_RepFun" :: "[i, pttrn, i] => i" ("(1{_ ./ _: _})" [51,0,51])
"_INTER" :: "[pttrn, i, i] => i" ("(3INT _:_./ _)" 10)
"_UNION" :: "[pttrn, i, i] => i" ("(3UN _:_./ _)" 10)
"_PROD" :: "[pttrn, i, i] => i" ("(3PROD _:_./ _)" 10)
"_SUM" :: "[pttrn, i, i] => i" ("(3SUM _:_./ _)" 10)
"_lam" :: "[pttrn, i, i] => i" ("(3lam _:_./ _)" 10)
"_Ball" :: "[pttrn, i, o] => o" ("(3ALL _:_./ _)" 10)
"_Bex" :: "[pttrn, i, o] => o" ("(3EX _:_./ _)" 10)
(** Patterns -- extends pre-defined type "pttrn" used in abstractions **)
"_pattern" :: "patterns => pttrn" ("<_>")
"" :: "pttrn => patterns" ("_")
"_patterns" :: "[pttrn, patterns] => patterns" ("_,/_")
translations
"{x, xs}" == "CONST cons(x, {xs})"
"{x}" == "CONST cons(x, 0)"
"{x:A. P}" == "CONST Collect(A, %x. P)"
"{y. x:A, Q}" == "CONST Replace(A, %x y. Q)"
"{b. x:A}" == "CONST RepFun(A, %x. b)"
"INT x:A. B" == "CONST Inter({B. x:A})"
"UN x:A. B" == "CONST Union({B. x:A})"
"PROD x:A. B" == "CONST Pi(A, %x. B)"
"SUM x:A. B" == "CONST Sigma(A, %x. B)"
"lam x:A. f" == "CONST Lambda(A, %x. f)"
"ALL x:A. P" == "CONST Ball(A, %x. P)"
"EX x:A. P" == "CONST Bex(A, %x. P)"
"<x, y, z>" == "<x, <y, z>>"
"<x, y>" == "CONST Pair(x, y)"
"%<x,y,zs>.b" == "CONST split(%x <y,zs>.b)"
"%<x,y>.b" == "CONST split(%x y. b)"
notation (xsymbols)
cart_prod (infixr "\<times>" 80) and
Int (infixl "\<inter>" 70) and
Un (infixl "\<union>" 65) and
function_space (infixr "\<rightarrow>" 60) and
Subset (infixl "\<subseteq>" 50) and
mem (infixl "\<in>" 50) and
not_mem (infixl "\<notin>" 50) and
Union ("\<Union>_" [90] 90) and
Inter ("\<Inter>_" [90] 90)
syntax (xsymbols)
"_Collect" :: "[pttrn, i, o] => i" ("(1{_ \<in> _ ./ _})")
"_Replace" :: "[pttrn, pttrn, i, o] => i" ("(1{_ ./ _ \<in> _, _})")
"_RepFun" :: "[i, pttrn, i] => i" ("(1{_ ./ _ \<in> _})" [51,0,51])
"_UNION" :: "[pttrn, i, i] => i" ("(3\<Union>_\<in>_./ _)" 10)
"_INTER" :: "[pttrn, i, i] => i" ("(3\<Inter>_\<in>_./ _)" 10)
"_PROD" :: "[pttrn, i, i] => i" ("(3\<Pi>_\<in>_./ _)" 10)
"_SUM" :: "[pttrn, i, i] => i" ("(3\<Sigma>_\<in>_./ _)" 10)
"_lam" :: "[pttrn, i, i] => i" ("(3\<lambda>_\<in>_./ _)" 10)
"_Ball" :: "[pttrn, i, o] => o" ("(3\<forall>_\<in>_./ _)" 10)
"_Bex" :: "[pttrn, i, o] => o" ("(3\<exists>_\<in>_./ _)" 10)
"_Tuple" :: "[i, is] => i" ("\<langle>(_,/ _)\<rangle>")
"_pattern" :: "patterns => pttrn" ("\<langle>_\<rangle>")
notation (HTML output)
cart_prod (infixr "\<times>" 80) and
Int (infixl "\<inter>" 70) and
Un (infixl "\<union>" 65) and
Subset (infixl "\<subseteq>" 50) and
mem (infixl "\<in>" 50) and
not_mem (infixl "\<notin>" 50) and
Union ("\<Union>_" [90] 90) and
Inter ("\<Inter>_" [90] 90)
syntax (HTML output)
"_Collect" :: "[pttrn, i, o] => i" ("(1{_ \<in> _ ./ _})")
"_Replace" :: "[pttrn, pttrn, i, o] => i" ("(1{_ ./ _ \<in> _, _})")
"_RepFun" :: "[i, pttrn, i] => i" ("(1{_ ./ _ \<in> _})" [51,0,51])
"_UNION" :: "[pttrn, i, i] => i" ("(3\<Union>_\<in>_./ _)" 10)
"_INTER" :: "[pttrn, i, i] => i" ("(3\<Inter>_\<in>_./ _)" 10)
"_PROD" :: "[pttrn, i, i] => i" ("(3\<Pi>_\<in>_./ _)" 10)
"_SUM" :: "[pttrn, i, i] => i" ("(3\<Sigma>_\<in>_./ _)" 10)
"_lam" :: "[pttrn, i, i] => i" ("(3\<lambda>_\<in>_./ _)" 10)
"_Ball" :: "[pttrn, i, o] => o" ("(3\<forall>_\<in>_./ _)" 10)
"_Bex" :: "[pttrn, i, o] => o" ("(3\<exists>_\<in>_./ _)" 10)
"_Tuple" :: "[i, is] => i" ("\<langle>(_,/ _)\<rangle>")
"_pattern" :: "patterns => pttrn" ("\<langle>_\<rangle>")
finalconsts
0 Pow Inf Union PrimReplace mem
defs (* Bounded Quantifiers *)
Ball_def: "Ball(A, P) == \<forall>x. x\<in>A --> P(x)"
Bex_def: "Bex(A, P) == \<exists>x. x\<in>A & P(x)"
subset_def: "A <= B == \<forall>x\<in>A. x\<in>B"
local
axioms
(* ZF axioms -- see Suppes p.238
Axioms for Union, Pow and Replace state existence only,
uniqueness is derivable using extensionality. *)
extension: "A = B <-> A <= B & B <= A"
Union_iff: "A \<in> Union(C) <-> (\<exists>B\<in>C. A\<in>B)"
Pow_iff: "A \<in> Pow(B) <-> A <= B"
(*We may name this set, though it is not uniquely defined.*)
infinity: "0\<in>Inf & (\<forall>y\<in>Inf. succ(y): Inf)"
(*This formulation facilitates case analysis on A.*)
foundation: "A=0 | (\<exists>x\<in>A. \<forall>y\<in>x. y~:A)"
(*Schema axiom since predicate P is a higher-order variable*)
replacement: "(\<forall>x\<in>A. \<forall>y z. P(x,y) & P(x,z) --> y=z) ==>
b \<in> PrimReplace(A,P) <-> (\<exists>x\<in>A. P(x,b))"
defs
(* 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. *)
Replace_def: "Replace(A,P) == PrimReplace(A, %x y. (EX!z. P(x,z)) & P(x,y))"
(* Functional form of replacement -- analgous to ML's map functional *)
RepFun_def: "RepFun(A,f) == {y . x\<in>A, y=f(x)}"
(* Separation and Pairing can be derived from the Replacement
and Powerset Axioms using the following definitions. *)
Collect_def: "Collect(A,P) == {y . x\<in>A, x=y & P(x)}"
(*Unordered pairs (Upair) express binary union/intersection and cons;
set enumerations translate as {a,...,z} = cons(a,...,cons(z,0)...)*)
Upair_def: "Upair(a,b) == {y. x\<in>Pow(Pow(0)), (x=0 & y=a) | (x=Pow(0) & y=b)}"
cons_def: "cons(a,A) == Upair(a,a) Un A"
succ_def: "succ(i) == cons(i, i)"
(* Difference, general intersection, binary union and small intersection *)
Diff_def: "A - B == { x\<in>A . ~(x\<in>B) }"
Inter_def: "Inter(A) == { x\<in>Union(A) . \<forall>y\<in>A. x\<in>y}"
Un_def: "A Un B == Union(Upair(A,B))"
Int_def: "A Int B == Inter(Upair(A,B))"
(* definite descriptions *)
the_def: "The(P) == Union({y . x \<in> {0}, P(y)})"
if_def: "if(P,a,b) == THE z. P & z=a | ~P & z=b"
(* this "symmetric" definition works better than {{a}, {a,b}} *)
Pair_def: "<a,b> == {{a,a}, {a,b}}"
fst_def: "fst(p) == THE a. \<exists>b. p=<a,b>"
snd_def: "snd(p) == THE b. \<exists>a. p=<a,b>"
split_def: "split(c) == %p. c(fst(p), snd(p))"
Sigma_def: "Sigma(A,B) == \<Union>x\<in>A. \<Union>y\<in>B(x). {<x,y>}"
(* Operations on relations *)
(*converse of relation r, inverse of function*)
converse_def: "converse(r) == {z. w\<in>r, \<exists>x y. w=<x,y> & z=<y,x>}"
domain_def: "domain(r) == {x. w\<in>r, \<exists>y. w=<x,y>}"
range_def: "range(r) == domain(converse(r))"
field_def: "field(r) == domain(r) Un range(r)"
relation_def: "relation(r) == \<forall>z\<in>r. \<exists>x y. z = <x,y>"
function_def: "function(r) ==
\<forall>x y. <x,y>:r --> (\<forall>y'. <x,y'>:r --> y=y')"
image_def: "r `` A == {y : range(r) . \<exists>x\<in>A. <x,y> : r}"
vimage_def: "r -`` A == converse(r)``A"
(* Abstraction, application and Cartesian product of a family of sets *)
lam_def: "Lambda(A,b) == {<x,b(x)> . x\<in>A}"
apply_def: "f`a == Union(f``{a})"
Pi_def: "Pi(A,B) == {f\<in>Pow(Sigma(A,B)). A<=domain(f) & function(f)}"
(* Restrict the relation r to the domain A *)
restrict_def: "restrict(r,A) == {z : r. \<exists>x\<in>A. \<exists>y. z = <x,y>}"
subsection {* Substitution*}
(*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{*Bounded universal quantifier*}
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~:A ==> Q; P(x) ==> Q |] ==> Q"
by (simp add: Ball_def, blast)
lemma ballE: "[| \<forall>x\<in>A. P(x); P(x) ==> Q; x~: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; (\<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) --> 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{*Bounded existential quantifier*}
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 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; ~\<exists>has become ALL~ *)
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 (\<exists>x\<in>A. True) <-> True unless 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{*Rules for subsets*}
lemma subsetI [intro!]:
"(!!x. x\<in>A ==> x\<in>B) ==> A <= B"
by (simp add: subset_def)
(*Rule in Modus Ponens style [was called subsetE] *)
lemma subsetD [elim]: "[| A <= B; c\<in>A |] ==> c\<in>B"
apply (unfold subset_def)
apply (erule bspec, assumption)
done
(*Classical elimination rule*)
lemma subsetCE [elim]:
"[| A <= B; c~: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 <= B; c ~: B |] ==> c ~: A"
by blast
lemma rev_contra_subsetD: "[| c ~: B; A <= B |] ==> c ~: A"
by blast
lemma subset_refl [simp]: "A <= 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 --> x\<in>B)"
apply (unfold subset_def Ball_def)
apply (rule iff_refl)
done
subsection{*Rules for equality*}
(*Anti-symmetry of the subset relation*)
lemma equalityI [intro]: "[| A <= B; B <= 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, standard]
lemmas equalityD2 = extension [THEN iffD1, THEN conjunct2, standard]
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~:A; c~:B |] ==> P |] ==> P"
by (erule equalityE, blast)
lemma equality_iffD:
"A = B ==> (!!x. x : A <-> x : B)"
by auto
subsection{*Rules for Replace -- the derived form of replacement*}
lemma Replace_iff:
"b : {y. x\<in>A, P(x,y)} <-> (\<exists>x\<in>A. P(x,b) & (\<forall>y. P(x,y) --> 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 : {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 : {y. x\<in>A, P(x,y)};
!!x. [| x: A; P(x,b); \<forall>y. P(x,y)-->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 : {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{*Rules for RepFun*}
lemma RepFunI: "a \<in> A ==> f(a) : {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 : {f(x). x\<in>A}"
apply (erule ssubst)
apply (erule RepFunI)
done
lemma RepFunE [elim!]:
"[| b : {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 : {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{*Rules for Collect -- forming a subset by separation*}
(*Separation is derivable from Replacement*)
lemma separation [simp]: "a : {x\<in>A. P(x)} <-> a\<in>A & P(a)"
by (unfold Collect_def, blast)
lemma CollectI [intro!]: "[| a\<in>A; P(a) |] ==> a : {x\<in>A. P(x)}"
by simp
lemma CollectE [elim!]: "[| a : {x\<in>A. P(x)}; [| a\<in>A; P(a) |] ==> R |] ==> R"
by simp
lemma CollectD1: "a : {x\<in>A. P(x)} ==> a\<in>A"
by (erule CollectE, assumption)
lemma CollectD2: "a : {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{*Rules for Unions*}
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{*Rules for Unions of families*}
(* \<Union>x\<in>A. B(x) abbreviates Union({B(x). x\<in>A}) *)
lemma UN_iff [simp]: "b : (\<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 : (\<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 \<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{*Rules for the empty set*}
(*The set {x\<in>0. False} is empty; by foundation it equals 0
See Suppes, page 21.*)
lemma not_mem_empty [simp]: "a ~: 0"
apply (cut_tac foundation)
apply (best dest: equalityD2)
done
lemmas emptyE [elim!] = not_mem_empty [THEN notE, standard]
lemma empty_subsetI [simp]: "0 <= A"
by blast
lemma equals0I: "[| !!y. y\<in>A ==> False |] ==> A=0"
by blast
lemma equals0D [dest]: "A=0 ==> a ~: A"
by blast
declare sym [THEN equals0D, dest]
lemma not_emptyI: "a\<in>A ==> A ~= 0"
by blast
lemma not_emptyE: "[| A ~= 0; !!x. x\<in>A ==> R |] ==> R"
by blast
subsection{*Rules for Inter*}
(*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]: "[| A \<in> Inter(C); B \<in> C |] ==> A \<in> B"
by (unfold Inter_def, blast)
(*"Classical" elimination rule -- does not require exhibiting B\<in>C *)
lemma InterE [elim]:
"[| A \<in> Inter(C); B~:C ==> R; A\<in>B ==> R |] ==> R"
by (simp add: Inter_def, blast)
subsection{*Rules for Intersections of families*}
(* \<Inter>x\<in>A. B(x) abbreviates Inter({B(x). x\<in>A}) *)
lemma INT_iff: "b : (\<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 : (\<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 \<Inter>is a combination of constants*)
subsection{*Rules for Powersets*}
lemma PowI: "A <= 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] (* 0 \<in> Pow(B) *)
lemmas Pow_top = subset_refl [THEN PowI] (* A \<in> Pow(A) *)
subsection{*Cantor's Theorem: There is no surjection from a set to its powerset.*}
(*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) ~= S"
by (best elim!: equalityCE del: ReplaceI RepFun_eqI)
(*Functions for ML scripts*)
ML
{*
(*Converts A<=B to x\<in>A ==> x\<in>B*)
fun impOfSubs th = th RSN (2, @{thm rev_subsetD});
(*Takes assumptions \<forall>x\<in>A.P(x) and a\<in>A; creates assumption P(a)*)
val ball_tac = dtac @{thm bspec} THEN' assume_tac
*}
end