(* Title: HOL/ZF/HOLZF.thy
Author: Steven Obua
Axiomatizes the ZFC universe as an HOL type. See "Partizan Games in
Isabelle/HOLZF", available from http://www4.in.tum.de/~obua/partizan
*)
theory HOLZF
imports Main
begin
typedecl ZF
axiomatization
Empty :: ZF and
Elem :: "ZF \<Rightarrow> ZF \<Rightarrow> bool" and
Sum :: "ZF \<Rightarrow> ZF" and
Power :: "ZF \<Rightarrow> ZF" and
Repl :: "ZF \<Rightarrow> (ZF \<Rightarrow> ZF) \<Rightarrow> ZF" and
Inf :: ZF
definition Upair :: "ZF \<Rightarrow> ZF \<Rightarrow> ZF" where
"Upair a b == Repl (Power (Power Empty)) (% x. if x = Empty then a else b)"
definition Singleton:: "ZF \<Rightarrow> ZF" where
"Singleton x == Upair x x"
definition union :: "ZF \<Rightarrow> ZF \<Rightarrow> ZF" where
"union A B == Sum (Upair A B)"
definition SucNat:: "ZF \<Rightarrow> ZF" where
"SucNat x == union x (Singleton x)"
definition subset :: "ZF \<Rightarrow> ZF \<Rightarrow> bool" where
"subset A B == ! x. Elem x A \<longrightarrow> Elem x B"
axiomatization where
Empty: "Not (Elem x Empty)" and
Ext: "(x = y) = (! z. Elem z x = Elem z y)" and
Sum: "Elem z (Sum x) = (? y. Elem z y & Elem y x)" and
Power: "Elem y (Power x) = (subset y x)" and
Repl: "Elem b (Repl A f) = (? a. Elem a A & b = f a)" and
Regularity: "A \<noteq> Empty \<longrightarrow> (? x. Elem x A & (! y. Elem y x \<longrightarrow> Not (Elem y A)))" and
Infinity: "Elem Empty Inf & (! x. Elem x Inf \<longrightarrow> Elem (SucNat x) Inf)"
definition Sep :: "ZF \<Rightarrow> (ZF \<Rightarrow> bool) \<Rightarrow> ZF" where
"Sep A p == (if (!x. Elem x A \<longrightarrow> Not (p x)) then Empty else
(let z = (\<some> x. Elem x A & p x) in
let f = % x. (if p x then x else z) in Repl A f))"
thm Power[unfolded subset_def]
theorem Sep: "Elem b (Sep A p) = (Elem b A & p b)"
apply (auto simp add: Sep_def Empty)
apply (auto simp add: Let_def Repl)
apply (rule someI2, auto)+
done
lemma subset_empty: "subset Empty A"
by (simp add: subset_def Empty)
theorem Upair: "Elem x (Upair a b) = (x = a | x = b)"
apply (auto simp add: Upair_def Repl)
apply (rule exI[where x=Empty])
apply (simp add: Power subset_empty)
apply (rule exI[where x="Power Empty"])
apply (auto)
apply (auto simp add: Ext Power subset_def Empty)
apply (drule spec[where x=Empty], simp add: Empty)+
done
lemma Singleton: "Elem x (Singleton y) = (x = y)"
by (simp add: Singleton_def Upair)
definition Opair :: "ZF \<Rightarrow> ZF \<Rightarrow> ZF" where
"Opair a b == Upair (Upair a a) (Upair a b)"
lemma Upair_singleton: "(Upair a a = Upair c d) = (a = c & a = d)"
by (auto simp add: Ext[where x="Upair a a"] Upair)
lemma Upair_fsteq: "(Upair a b = Upair a c) = ((a = b & a = c) | (b = c))"
by (auto simp add: Ext[where x="Upair a b"] Upair)
lemma Upair_comm: "Upair a b = Upair b a"
by (auto simp add: Ext Upair)
theorem Opair: "(Opair a b = Opair c d) = (a = c & b = d)"
proof -
have fst: "(Opair a b = Opair c d) \<Longrightarrow> a = c"
apply (simp add: Opair_def)
apply (simp add: Ext[where x="Upair (Upair a a) (Upair a b)"])
apply (drule spec[where x="Upair a a"])
apply (auto simp add: Upair Upair_singleton)
done
show ?thesis
apply (auto)
apply (erule fst)
apply (frule fst)
apply (auto simp add: Opair_def Upair_fsteq)
done
qed
definition Replacement :: "ZF \<Rightarrow> (ZF \<Rightarrow> ZF option) \<Rightarrow> ZF" where
"Replacement A f == Repl (Sep A (% a. f a \<noteq> None)) (the o f)"
theorem Replacement: "Elem y (Replacement A f) = (? x. Elem x A & f x = Some y)"
by (auto simp add: Replacement_def Repl Sep)
definition Fst :: "ZF \<Rightarrow> ZF" where
"Fst q == SOME x. ? y. q = Opair x y"
definition Snd :: "ZF \<Rightarrow> ZF" where
"Snd q == SOME y. ? x. q = Opair x y"
theorem Fst: "Fst (Opair x y) = x"
apply (simp add: Fst_def)
apply (rule someI2)
apply (simp_all add: Opair)
done
theorem Snd: "Snd (Opair x y) = y"
apply (simp add: Snd_def)
apply (rule someI2)
apply (simp_all add: Opair)
done
definition isOpair :: "ZF \<Rightarrow> bool" where
"isOpair q == ? x y. q = Opair x y"
lemma isOpair: "isOpair (Opair x y) = True"
by (auto simp add: isOpair_def)
lemma FstSnd: "isOpair x \<Longrightarrow> Opair (Fst x) (Snd x) = x"
by (auto simp add: isOpair_def Fst Snd)
definition CartProd :: "ZF \<Rightarrow> ZF \<Rightarrow> ZF" where
"CartProd A B == Sum(Repl A (% a. Repl B (% b. Opair a b)))"
lemma CartProd: "Elem x (CartProd A B) = (? a b. Elem a A & Elem b B & x = (Opair a b))"
apply (auto simp add: CartProd_def Sum Repl)
apply (rule_tac x="Repl B (Opair a)" in exI)
apply (auto simp add: Repl)
done
definition explode :: "ZF \<Rightarrow> ZF set" where
"explode z == { x. Elem x z }"
lemma explode_Empty: "(explode x = {}) = (x = Empty)"
by (auto simp add: explode_def Ext Empty)
lemma explode_Elem: "(x \<in> explode X) = (Elem x X)"
by (simp add: explode_def)
lemma Elem_explode_in: "\<lbrakk> Elem a A; explode A \<subseteq> B\<rbrakk> \<Longrightarrow> a \<in> B"
by (auto simp add: explode_def)
lemma explode_CartProd_eq: "explode (CartProd a b) = (% (x,y). Opair x y) ` ((explode a) \<times> (explode b))"
by (simp add: explode_def set_eq_iff CartProd image_def)
lemma explode_Repl_eq: "explode (Repl A f) = image f (explode A)"
by (simp add: explode_def Repl image_def)
definition Domain :: "ZF \<Rightarrow> ZF" where
"Domain f == Replacement f (% p. if isOpair p then Some (Fst p) else None)"
definition Range :: "ZF \<Rightarrow> ZF" where
"Range f == Replacement f (% p. if isOpair p then Some (Snd p) else None)"
theorem Domain: "Elem x (Domain f) = (? y. Elem (Opair x y) f)"
apply (auto simp add: Domain_def Replacement)
apply (rule_tac x="Snd xa" in exI)
apply (simp add: FstSnd)
apply (rule_tac x="Opair x y" in exI)
apply (simp add: isOpair Fst)
done
theorem Range: "Elem y (Range f) = (? x. Elem (Opair x y) f)"
apply (auto simp add: Range_def Replacement)
apply (rule_tac x="Fst x" in exI)
apply (simp add: FstSnd)
apply (rule_tac x="Opair x y" in exI)
apply (simp add: isOpair Snd)
done
theorem union: "Elem x (union A B) = (Elem x A | Elem x B)"
by (auto simp add: union_def Sum Upair)
definition Field :: "ZF \<Rightarrow> ZF" where
"Field A == union (Domain A) (Range A)"
definition app :: "ZF \<Rightarrow> ZF => ZF" (infixl "\<acute>" 90) --{*function application*} where
"f \<acute> x == (THE y. Elem (Opair x y) f)"
definition isFun :: "ZF \<Rightarrow> bool" where
"isFun f == (! x y1 y2. Elem (Opair x y1) f & Elem (Opair x y2) f \<longrightarrow> y1 = y2)"
definition Lambda :: "ZF \<Rightarrow> (ZF \<Rightarrow> ZF) \<Rightarrow> ZF" where
"Lambda A f == Repl A (% x. Opair x (f x))"
lemma Lambda_app: "Elem x A \<Longrightarrow> (Lambda A f)\<acute>x = f x"
by (simp add: app_def Lambda_def Repl Opair)
lemma isFun_Lambda: "isFun (Lambda A f)"
by (auto simp add: isFun_def Lambda_def Repl Opair)
lemma domain_Lambda: "Domain (Lambda A f) = A"
apply (auto simp add: Domain_def)
apply (subst Ext)
apply (auto simp add: Replacement)
apply (simp add: Lambda_def Repl)
apply (auto simp add: Fst)
apply (simp add: Lambda_def Repl)
apply (rule_tac x="Opair z (f z)" in exI)
apply (auto simp add: Fst isOpair_def)
done
lemma Lambda_ext: "(Lambda s f = Lambda t g) = (s = t & (! x. Elem x s \<longrightarrow> f x = g x))"
proof -
have "Lambda s f = Lambda t g \<Longrightarrow> s = t"
apply (subst domain_Lambda[where A = s and f = f, symmetric])
apply (subst domain_Lambda[where A = t and f = g, symmetric])
apply auto
done
then show ?thesis
apply auto
apply (subst Lambda_app[where f=f, symmetric], simp)
apply (subst Lambda_app[where f=g, symmetric], simp)
apply auto
apply (auto simp add: Lambda_def Repl Ext)
apply (auto simp add: Ext[symmetric])
done
qed
definition PFun :: "ZF \<Rightarrow> ZF \<Rightarrow> ZF" where
"PFun A B == Sep (Power (CartProd A B)) isFun"
definition Fun :: "ZF \<Rightarrow> ZF \<Rightarrow> ZF" where
"Fun A B == Sep (PFun A B) (\<lambda> f. Domain f = A)"
lemma Fun_Range: "Elem f (Fun U V) \<Longrightarrow> subset (Range f) V"
apply (simp add: Fun_def Sep PFun_def Power subset_def CartProd)
apply (auto simp add: Domain Range)
apply (erule_tac x="Opair xa x" in allE)
apply (auto simp add: Opair)
done
lemma Elem_Elem_PFun: "Elem F (PFun U V) \<Longrightarrow> Elem p F \<Longrightarrow> isOpair p & Elem (Fst p) U & Elem (Snd p) V"
apply (simp add: PFun_def Sep Power subset_def, clarify)
apply (erule_tac x=p in allE)
apply (auto simp add: CartProd isOpair Fst Snd)
done
lemma Fun_implies_PFun[simp]: "Elem f (Fun U V) \<Longrightarrow> Elem f (PFun U V)"
by (simp add: Fun_def Sep)
lemma Elem_Elem_Fun: "Elem F (Fun U V) \<Longrightarrow> Elem p F \<Longrightarrow> isOpair p & Elem (Fst p) U & Elem (Snd p) V"
by (auto simp add: Elem_Elem_PFun dest: Fun_implies_PFun)
lemma PFun_inj: "Elem F (PFun U V) \<Longrightarrow> Elem x F \<Longrightarrow> Elem y F \<Longrightarrow> Fst x = Fst y \<Longrightarrow> Snd x = Snd y"
apply (frule Elem_Elem_PFun[where p=x], simp)
apply (frule Elem_Elem_PFun[where p=y], simp)
apply (subgoal_tac "isFun F")
apply (simp add: isFun_def isOpair_def)
apply (auto simp add: Fst Snd)
apply (auto simp add: PFun_def Sep)
done
lemma Fun_total: "\<lbrakk>Elem F (Fun U V); Elem a U\<rbrakk> \<Longrightarrow> \<exists>x. Elem (Opair a x) F"
using [[simp_depth_limit = 2]]
by (auto simp add: Fun_def Sep Domain)
lemma unique_fun_value: "\<lbrakk>isFun f; Elem x (Domain f)\<rbrakk> \<Longrightarrow> ?! y. Elem (Opair x y) f"
by (auto simp add: Domain isFun_def)
lemma fun_value_in_range: "\<lbrakk>isFun f; Elem x (Domain f)\<rbrakk> \<Longrightarrow> Elem (f\<acute>x) (Range f)"
apply (auto simp add: Range)
apply (drule unique_fun_value)
apply simp
apply (simp add: app_def)
apply (rule exI[where x=x])
apply (auto simp add: the_equality)
done
lemma fun_range_witness: "\<lbrakk>isFun f; Elem y (Range f)\<rbrakk> \<Longrightarrow> ? x. Elem x (Domain f) & f\<acute>x = y"
apply (auto simp add: Range)
apply (rule_tac x="x" in exI)
apply (auto simp add: app_def the_equality isFun_def Domain)
done
lemma Elem_Fun_Lambda: "Elem F (Fun U V) \<Longrightarrow> ? f. F = Lambda U f"
apply (rule exI[where x= "% x. (THE y. Elem (Opair x y) F)"])
apply (simp add: Ext Lambda_def Repl Domain)
apply (simp add: Ext[symmetric])
apply auto
apply (frule Elem_Elem_Fun)
apply auto
apply (rule_tac x="Fst z" in exI)
apply (simp add: isOpair_def)
apply (auto simp add: Fst Snd Opair)
apply (rule the1I2)
apply auto
apply (drule Fun_implies_PFun)
apply (drule_tac x="Opair x ya" and y="Opair x yb" in PFun_inj)
apply (auto simp add: Fst Snd)
apply (drule Fun_implies_PFun)
apply (drule_tac x="Opair x y" and y="Opair x ya" in PFun_inj)
apply (auto simp add: Fst Snd)
apply (rule the1I2)
apply (auto simp add: Fun_total)
apply (drule Fun_implies_PFun)
apply (drule_tac x="Opair a x" and y="Opair a y" in PFun_inj)
apply (auto simp add: Fst Snd)
done
lemma Elem_Lambda_Fun: "Elem (Lambda A f) (Fun U V) = (A = U & (! x. Elem x A \<longrightarrow> Elem (f x) V))"
proof -
have "Elem (Lambda A f) (Fun U V) \<Longrightarrow> A = U"
by (simp add: Fun_def Sep domain_Lambda)
then show ?thesis
apply auto
apply (drule Fun_Range)
apply (subgoal_tac "f x = ((Lambda U f) \<acute> x)")
prefer 2
apply (simp add: Lambda_app)
apply simp
apply (subgoal_tac "Elem (Lambda U f \<acute> x) (Range (Lambda U f))")
apply (simp add: subset_def)
apply (rule fun_value_in_range)
apply (simp_all add: isFun_Lambda domain_Lambda)
apply (simp add: Fun_def Sep PFun_def Power domain_Lambda isFun_Lambda)
apply (auto simp add: subset_def CartProd)
apply (rule_tac x="Fst x" in exI)
apply (auto simp add: Lambda_def Repl Fst)
done
qed
definition is_Elem_of :: "(ZF * ZF) set" where
"is_Elem_of == { (a,b) | a b. Elem a b }"
lemma cond_wf_Elem:
assumes hyps:"\<forall>x. (\<forall>y. Elem y x \<longrightarrow> Elem y U \<longrightarrow> P y) \<longrightarrow> Elem x U \<longrightarrow> P x" "Elem a U"
shows "P a"
proof -
{
fix P
fix U
fix a
assume P_induct: "(\<forall>x. (\<forall>y. Elem y x \<longrightarrow> Elem y U \<longrightarrow> P y) \<longrightarrow> (Elem x U \<longrightarrow> P x))"
assume a_in_U: "Elem a U"
have "P a"
proof -
term "P"
term Sep
let ?Z = "Sep U (Not o P)"
have "?Z = Empty \<longrightarrow> P a" by (simp add: Ext Sep Empty a_in_U)
moreover have "?Z \<noteq> Empty \<longrightarrow> False"
proof
assume not_empty: "?Z \<noteq> Empty"
note thereis_x = Regularity[where A="?Z", simplified not_empty, simplified]
then obtain x where x_def: "Elem x ?Z & (! y. Elem y x \<longrightarrow> Not (Elem y ?Z))" ..
then have x_induct:"! y. Elem y x \<longrightarrow> Elem y U \<longrightarrow> P y" by (simp add: Sep)
have "Elem x U \<longrightarrow> P x"
by (rule impE[OF spec[OF P_induct, where x=x], OF x_induct], assumption)
moreover have "Elem x U & Not(P x)"
apply (insert x_def)
apply (simp add: Sep)
done
ultimately show "False" by auto
qed
ultimately show "P a" by auto
qed
}
with hyps show ?thesis by blast
qed
lemma cond2_wf_Elem:
assumes
special_P: "? U. ! x. Not(Elem x U) \<longrightarrow> (P x)"
and P_induct: "\<forall>x. (\<forall>y. Elem y x \<longrightarrow> P y) \<longrightarrow> P x"
shows
"P a"
proof -
have "? U Q. P = (\<lambda> x. (Elem x U \<longrightarrow> Q x))"
proof -
from special_P obtain U where U:"! x. Not(Elem x U) \<longrightarrow> (P x)" ..
show ?thesis
apply (rule_tac exI[where x=U])
apply (rule exI[where x="P"])
apply (rule ext)
apply (auto simp add: U)
done
qed
then obtain U where "? Q. P = (\<lambda> x. (Elem x U \<longrightarrow> Q x))" ..
then obtain Q where UQ: "P = (\<lambda> x. (Elem x U \<longrightarrow> Q x))" ..
show ?thesis
apply (auto simp add: UQ)
apply (rule cond_wf_Elem)
apply (rule P_induct[simplified UQ])
apply simp
done
qed
primrec nat2Nat :: "nat \<Rightarrow> ZF" where
nat2Nat_0[intro]: "nat2Nat 0 = Empty"
| nat2Nat_Suc[intro]: "nat2Nat (Suc n) = SucNat (nat2Nat n)"
definition Nat2nat :: "ZF \<Rightarrow> nat" where
"Nat2nat == inv nat2Nat"
lemma Elem_nat2Nat_inf[intro]: "Elem (nat2Nat n) Inf"
apply (induct n)
apply (simp_all add: Infinity)
done
definition Nat :: ZF
where "Nat == Sep Inf (\<lambda> N. ? n. nat2Nat n = N)"
lemma Elem_nat2Nat_Nat[intro]: "Elem (nat2Nat n) Nat"
by (auto simp add: Nat_def Sep)
lemma Elem_Empty_Nat: "Elem Empty Nat"
by (auto simp add: Nat_def Sep Infinity)
lemma Elem_SucNat_Nat: "Elem N Nat \<Longrightarrow> Elem (SucNat N) Nat"
by (auto simp add: Nat_def Sep Infinity)
lemma no_infinite_Elem_down_chain:
"Not (? f. isFun f & Domain f = Nat & (! N. Elem N Nat \<longrightarrow> Elem (f\<acute>(SucNat N)) (f\<acute>N)))"
proof -
{
fix f
assume f:"isFun f & Domain f = Nat & (! N. Elem N Nat \<longrightarrow> Elem (f\<acute>(SucNat N)) (f\<acute>N))"
let ?r = "Range f"
have "?r \<noteq> Empty"
apply (auto simp add: Ext Empty)
apply (rule exI[where x="f\<acute>Empty"])
apply (rule fun_value_in_range)
apply (auto simp add: f Elem_Empty_Nat)
done
then have "? x. Elem x ?r & (! y. Elem y x \<longrightarrow> Not(Elem y ?r))"
by (simp add: Regularity)
then obtain x where x: "Elem x ?r & (! y. Elem y x \<longrightarrow> Not(Elem y ?r))" ..
then have "? N. Elem N (Domain f) & f\<acute>N = x"
apply (rule_tac fun_range_witness)
apply (simp_all add: f)
done
then have "? N. Elem N Nat & f\<acute>N = x"
by (simp add: f)
then obtain N where N: "Elem N Nat & f\<acute>N = x" ..
from N have N': "Elem N Nat" by auto
let ?y = "f\<acute>(SucNat N)"
have Elem_y_r: "Elem ?y ?r"
by (simp_all add: f Elem_SucNat_Nat N fun_value_in_range)
have "Elem ?y (f\<acute>N)" by (auto simp add: f N')
then have "Elem ?y x" by (simp add: N)
with x have "Not (Elem ?y ?r)" by auto
with Elem_y_r have "False" by auto
}
then show ?thesis by auto
qed
lemma Upair_nonEmpty: "Upair a b \<noteq> Empty"
by (auto simp add: Ext Empty Upair)
lemma Singleton_nonEmpty: "Singleton x \<noteq> Empty"
by (auto simp add: Singleton_def Upair_nonEmpty)
lemma notsym_Elem: "Not(Elem a b & Elem b a)"
proof -
{
fix a b
assume ab: "Elem a b"
assume ba: "Elem b a"
let ?Z = "Upair a b"
have "?Z \<noteq> Empty" by (simp add: Upair_nonEmpty)
then have "? x. Elem x ?Z & (! y. Elem y x \<longrightarrow> Not(Elem y ?Z))"
by (simp add: Regularity)
then obtain x where x:"Elem x ?Z & (! y. Elem y x \<longrightarrow> Not(Elem y ?Z))" ..
then have "x = a \<or> x = b" by (simp add: Upair)
moreover have "x = a \<longrightarrow> Not (Elem b ?Z)"
by (auto simp add: x ba)
moreover have "x = b \<longrightarrow> Not (Elem a ?Z)"
by (auto simp add: x ab)
ultimately have "False"
by (auto simp add: Upair)
}
then show ?thesis by auto
qed
lemma irreflexiv_Elem: "Not(Elem a a)"
by (simp add: notsym_Elem[of a a, simplified])
lemma antisym_Elem: "Elem a b \<Longrightarrow> Not (Elem b a)"
apply (insert notsym_Elem[of a b])
apply auto
done
primrec NatInterval :: "nat \<Rightarrow> nat \<Rightarrow> ZF" where
"NatInterval n 0 = Singleton (nat2Nat n)"
| "NatInterval n (Suc m) = union (NatInterval n m) (Singleton (nat2Nat (n+m+1)))"
lemma n_Elem_NatInterval[rule_format]: "! q. q <= m \<longrightarrow> Elem (nat2Nat (n+q)) (NatInterval n m)"
apply (induct m)
apply (auto simp add: Singleton union)
apply (case_tac "q <= m")
apply auto
apply (subgoal_tac "q = Suc m")
apply auto
done
lemma NatInterval_not_Empty: "NatInterval n m \<noteq> Empty"
by (auto intro: n_Elem_NatInterval[where q = 0, simplified] simp add: Empty Ext)
lemma increasing_nat2Nat[rule_format]: "0 < n \<longrightarrow> Elem (nat2Nat (n - 1)) (nat2Nat n)"
apply (case_tac "? m. n = Suc m")
apply (auto simp add: SucNat_def union Singleton)
apply (drule spec[where x="n - 1"])
apply arith
done
lemma represent_NatInterval[rule_format]: "Elem x (NatInterval n m) \<longrightarrow> (? u. n \<le> u & u \<le> n+m & nat2Nat u = x)"
apply (induct m)
apply (auto simp add: Singleton union)
apply (rule_tac x="Suc (n+m)" in exI)
apply auto
done
lemma inj_nat2Nat: "inj nat2Nat"
proof -
{
fix n m :: nat
assume nm: "nat2Nat n = nat2Nat (n+m)"
assume mg0: "0 < m"
let ?Z = "NatInterval n m"
have "?Z \<noteq> Empty" by (simp add: NatInterval_not_Empty)
then have "? x. (Elem x ?Z) & (! y. Elem y x \<longrightarrow> Not (Elem y ?Z))"
by (auto simp add: Regularity)
then obtain x where x:"Elem x ?Z & (! y. Elem y x \<longrightarrow> Not (Elem y ?Z))" ..
then have "? u. n \<le> u & u \<le> n+m & nat2Nat u = x"
by (simp add: represent_NatInterval)
then obtain u where u: "n \<le> u & u \<le> n+m & nat2Nat u = x" ..
have "n < u \<longrightarrow> False"
proof
assume n_less_u: "n < u"
let ?y = "nat2Nat (u - 1)"
have "Elem ?y (nat2Nat u)"
apply (rule increasing_nat2Nat)
apply (insert n_less_u)
apply arith
done
with u have "Elem ?y x" by auto
with x have "Not (Elem ?y ?Z)" by auto
moreover have "Elem ?y ?Z"
apply (insert n_Elem_NatInterval[where q = "u - n - 1" and n=n and m=m])
apply (insert n_less_u)
apply (insert u)
apply auto
done
ultimately show False by auto
qed
moreover have "u = n \<longrightarrow> False"
proof
assume "u = n"
with u have "nat2Nat n = x" by auto
then have nm_eq_x: "nat2Nat (n+m) = x" by (simp add: nm)
let ?y = "nat2Nat (n+m - 1)"
have "Elem ?y (nat2Nat (n+m))"
apply (rule increasing_nat2Nat)
apply (insert mg0)
apply arith
done
with nm_eq_x have "Elem ?y x" by auto
with x have "Not (Elem ?y ?Z)" by auto
moreover have "Elem ?y ?Z"
apply (insert n_Elem_NatInterval[where q = "m - 1" and n=n and m=m])
apply (insert mg0)
apply auto
done
ultimately show False by auto
qed
ultimately have "False" using u by arith
}
note lemma_nat2Nat = this
have th:"\<And>x y. \<not> (x < y \<and> (\<forall>(m\<Colon>nat). y \<noteq> x + m))" by presburger
have th': "\<And>x y. \<not> (x \<noteq> y \<and> (\<not> x < y) \<and> (\<forall>(m\<Colon>nat). x \<noteq> y + m))" by presburger
show ?thesis
apply (auto simp add: inj_on_def)
apply (case_tac "x = y")
apply auto
apply (case_tac "x < y")
apply (case_tac "? m. y = x + m & 0 < m")
apply (auto intro: lemma_nat2Nat)
apply (case_tac "y < x")
apply (case_tac "? m. x = y + m & 0 < m")
apply simp
apply simp
using th apply blast
apply (case_tac "? m. x = y + m")
apply (auto intro: lemma_nat2Nat)
apply (drule sym)
using lemma_nat2Nat apply blast
using th' apply blast
done
qed
lemma Nat2nat_nat2Nat[simp]: "Nat2nat (nat2Nat n) = n"
by (simp add: Nat2nat_def inv_f_f[OF inj_nat2Nat])
lemma nat2Nat_Nat2nat[simp]: "Elem n Nat \<Longrightarrow> nat2Nat (Nat2nat n) = n"
apply (simp add: Nat2nat_def)
apply (rule_tac f_inv_into_f)
apply (auto simp add: image_def Nat_def Sep)
done
lemma Nat2nat_SucNat: "Elem N Nat \<Longrightarrow> Nat2nat (SucNat N) = Suc (Nat2nat N)"
apply (auto simp add: Nat_def Sep Nat2nat_def)
apply (auto simp add: inv_f_f[OF inj_nat2Nat])
apply (simp only: nat2Nat.simps[symmetric])
apply (simp only: inv_f_f[OF inj_nat2Nat])
done
(*lemma Elem_induct: "(\<And>x. \<forall>y. Elem y x \<longrightarrow> P y \<Longrightarrow> P x) \<Longrightarrow> P a"
by (erule wf_induct[OF wf_is_Elem_of, simplified is_Elem_of_def, simplified])*)
lemma Elem_Opair_exists: "? z. Elem x z & Elem y z & Elem z (Opair x y)"
apply (rule exI[where x="Upair x y"])
by (simp add: Upair Opair_def)
lemma UNIV_is_not_in_ZF: "UNIV \<noteq> explode R"
proof
let ?Russell = "{ x. Not(Elem x x) }"
have "?Russell = UNIV" by (simp add: irreflexiv_Elem)
moreover assume "UNIV = explode R"
ultimately have russell: "?Russell = explode R" by simp
then show "False"
proof(cases "Elem R R")
case True
then show ?thesis
by (insert irreflexiv_Elem, auto)
next
case False
then have "R \<in> ?Russell" by auto
then have "Elem R R" by (simp add: russell explode_def)
with False show ?thesis by auto
qed
qed
definition SpecialR :: "(ZF * ZF) set" where
"SpecialR \<equiv> { (x, y) . x \<noteq> Empty \<and> y = Empty}"
lemma "wf SpecialR"
apply (subst wf_def)
apply (auto simp add: SpecialR_def)
done
definition Ext :: "('a * 'b) set \<Rightarrow> 'b \<Rightarrow> 'a set" where
"Ext R y \<equiv> { x . (x, y) \<in> R }"
lemma Ext_Elem: "Ext is_Elem_of = explode"
by (auto simp add: Ext_def is_Elem_of_def explode_def)
lemma "Ext SpecialR Empty \<noteq> explode z"
proof
have "Ext SpecialR Empty = UNIV - {Empty}"
by (auto simp add: Ext_def SpecialR_def)
moreover assume "Ext SpecialR Empty = explode z"
ultimately have "UNIV = explode(union z (Singleton Empty)) "
by (auto simp add: explode_def union Singleton)
then show "False" by (simp add: UNIV_is_not_in_ZF)
qed
definition implode :: "ZF set \<Rightarrow> ZF" where
"implode == inv explode"
lemma inj_explode: "inj explode"
by (auto simp add: inj_on_def explode_def Ext)
lemma implode_explode[simp]: "implode (explode x) = x"
by (simp add: implode_def inj_explode)
definition regular :: "(ZF * ZF) set \<Rightarrow> bool" where
"regular R == ! A. A \<noteq> Empty \<longrightarrow> (? x. Elem x A & (! y. (y, x) \<in> R \<longrightarrow> Not (Elem y A)))"
definition set_like :: "(ZF * ZF) set \<Rightarrow> bool" where
"set_like R == ! y. Ext R y \<in> range explode"
definition wfzf :: "(ZF * ZF) set \<Rightarrow> bool" where
"wfzf R == regular R & set_like R"
lemma regular_Elem: "regular is_Elem_of"
by (simp add: regular_def is_Elem_of_def Regularity)
lemma set_like_Elem: "set_like is_Elem_of"
by (auto simp add: set_like_def image_def Ext_Elem)
lemma wfzf_is_Elem_of: "wfzf is_Elem_of"
by (auto simp add: wfzf_def regular_Elem set_like_Elem)
definition SeqSum :: "(nat \<Rightarrow> ZF) \<Rightarrow> ZF" where
"SeqSum f == Sum (Repl Nat (f o Nat2nat))"
lemma SeqSum: "Elem x (SeqSum f) = (? n. Elem x (f n))"
apply (auto simp add: SeqSum_def Sum Repl)
apply (rule_tac x = "f n" in exI)
apply auto
done
definition Ext_ZF :: "(ZF * ZF) set \<Rightarrow> ZF \<Rightarrow> ZF" where
"Ext_ZF R s == implode (Ext R s)"
lemma Elem_implode: "A \<in> range explode \<Longrightarrow> Elem x (implode A) = (x \<in> A)"
apply (auto)
apply (simp_all add: explode_def)
done
lemma Elem_Ext_ZF: "set_like R \<Longrightarrow> Elem x (Ext_ZF R s) = ((x,s) \<in> R)"
apply (simp add: Ext_ZF_def)
apply (subst Elem_implode)
apply (simp add: set_like_def)
apply (simp add: Ext_def)
done
primrec Ext_ZF_n :: "(ZF * ZF) set \<Rightarrow> ZF \<Rightarrow> nat \<Rightarrow> ZF" where
"Ext_ZF_n R s 0 = Ext_ZF R s"
| "Ext_ZF_n R s (Suc n) = Sum (Repl (Ext_ZF_n R s n) (Ext_ZF R))"
definition Ext_ZF_hull :: "(ZF * ZF) set \<Rightarrow> ZF \<Rightarrow> ZF" where
"Ext_ZF_hull R s == SeqSum (Ext_ZF_n R s)"
lemma Elem_Ext_ZF_hull:
assumes set_like_R: "set_like R"
shows "Elem x (Ext_ZF_hull R S) = (? n. Elem x (Ext_ZF_n R S n))"
by (simp add: Ext_ZF_hull_def SeqSum)
lemma Elem_Elem_Ext_ZF_hull:
assumes set_like_R: "set_like R"
and x_hull: "Elem x (Ext_ZF_hull R S)"
and y_R_x: "(y, x) \<in> R"
shows "Elem y (Ext_ZF_hull R S)"
proof -
from Elem_Ext_ZF_hull[OF set_like_R] x_hull
have "? n. Elem x (Ext_ZF_n R S n)" by auto
then obtain n where n:"Elem x (Ext_ZF_n R S n)" ..
with y_R_x have "Elem y (Ext_ZF_n R S (Suc n))"
apply (auto simp add: Repl Sum)
apply (rule_tac x="Ext_ZF R x" in exI)
apply (auto simp add: Elem_Ext_ZF[OF set_like_R])
done
with Elem_Ext_ZF_hull[OF set_like_R, where x=y] show ?thesis
by (auto simp del: Ext_ZF_n.simps)
qed
lemma wfzf_minimal:
assumes hyps: "wfzf R" "C \<noteq> {}"
shows "\<exists>x. x \<in> C \<and> (\<forall>y. (y, x) \<in> R \<longrightarrow> y \<notin> C)"
proof -
from hyps have "\<exists>S. S \<in> C" by auto
then obtain S where S:"S \<in> C" by auto
let ?T = "Sep (Ext_ZF_hull R S) (\<lambda> s. s \<in> C)"
from hyps have set_like_R: "set_like R" by (simp add: wfzf_def)
show ?thesis
proof (cases "?T = Empty")
case True
then have "\<forall> z. \<not> (Elem z (Sep (Ext_ZF R S) (\<lambda> s. s \<in> C)))"
apply (auto simp add: Ext Empty Sep Ext_ZF_hull_def SeqSum)
apply (erule_tac x="z" in allE, auto)
apply (erule_tac x=0 in allE, auto)
done
then show ?thesis
apply (rule_tac exI[where x=S])
apply (auto simp add: Sep Empty S)
apply (erule_tac x=y in allE)
apply (simp add: set_like_R Elem_Ext_ZF)
done
next
case False
from hyps have regular_R: "regular R" by (simp add: wfzf_def)
from
regular_R[simplified regular_def, rule_format, OF False, simplified Sep]
Elem_Elem_Ext_ZF_hull[OF set_like_R]
show ?thesis by blast
qed
qed
lemma wfzf_implies_wf: "wfzf R \<Longrightarrow> wf R"
proof (subst wf_def, rule allI)
assume wfzf: "wfzf R"
fix P :: "ZF \<Rightarrow> bool"
let ?C = "{x. P x}"
{
assume induct: "(\<forall>x. (\<forall>y. (y, x) \<in> R \<longrightarrow> P y) \<longrightarrow> P x)"
let ?C = "{x. \<not> (P x)}"
have "?C = {}"
proof (rule ccontr)
assume C: "?C \<noteq> {}"
from
wfzf_minimal[OF wfzf C]
obtain x where x: "x \<in> ?C \<and> (\<forall>y. (y, x) \<in> R \<longrightarrow> y \<notin> ?C)" ..
then have "P x"
apply (rule_tac induct[rule_format])
apply auto
done
with x show "False" by auto
qed
then have "! x. P x" by auto
}
then show "(\<forall>x. (\<forall>y. (y, x) \<in> R \<longrightarrow> P y) \<longrightarrow> P x) \<longrightarrow> (! x. P x)" by blast
qed
lemma wf_is_Elem_of: "wf is_Elem_of"
by (auto simp add: wfzf_is_Elem_of wfzf_implies_wf)
lemma in_Ext_RTrans_implies_Elem_Ext_ZF_hull:
"set_like R \<Longrightarrow> x \<in> (Ext (R^+) s) \<Longrightarrow> Elem x (Ext_ZF_hull R s)"
apply (simp add: Ext_def Elem_Ext_ZF_hull)
apply (erule converse_trancl_induct[where r="R"])
apply (rule exI[where x=0])
apply (simp add: Elem_Ext_ZF)
apply auto
apply (rule_tac x="Suc n" in exI)
apply (simp add: Sum Repl)
apply (rule_tac x="Ext_ZF R z" in exI)
apply (auto simp add: Elem_Ext_ZF)
done
lemma implodeable_Ext_trancl: "set_like R \<Longrightarrow> set_like (R^+)"
apply (subst set_like_def)
apply (auto simp add: image_def)
apply (rule_tac x="Sep (Ext_ZF_hull R y) (\<lambda> z. z \<in> (Ext (R^+) y))" in exI)
apply (auto simp add: explode_def Sep set_eqI
in_Ext_RTrans_implies_Elem_Ext_ZF_hull)
done
lemma Elem_Ext_ZF_hull_implies_in_Ext_RTrans[rule_format]:
"set_like R \<Longrightarrow> ! x. Elem x (Ext_ZF_n R s n) \<longrightarrow> x \<in> (Ext (R^+) s)"
apply (induct_tac n)
apply (auto simp add: Elem_Ext_ZF Ext_def Sum Repl)
done
lemma "set_like R \<Longrightarrow> Ext_ZF (R^+) s = Ext_ZF_hull R s"
apply (frule implodeable_Ext_trancl)
apply (auto simp add: Ext)
apply (erule in_Ext_RTrans_implies_Elem_Ext_ZF_hull)
apply (simp add: Elem_Ext_ZF Ext_def)
apply (auto simp add: Elem_Ext_ZF Elem_Ext_ZF_hull)
apply (erule Elem_Ext_ZF_hull_implies_in_Ext_RTrans[simplified Ext_def, simplified], assumption)
done
lemma wf_implies_regular: "wf R \<Longrightarrow> regular R"
proof (simp add: regular_def, rule allI)
assume wf: "wf R"
fix A
show "A \<noteq> Empty \<longrightarrow> (\<exists>x. Elem x A \<and> (\<forall>y. (y, x) \<in> R \<longrightarrow> \<not> Elem y A))"
proof
assume A: "A \<noteq> Empty"
then have "? x. x \<in> explode A"
by (auto simp add: explode_def Ext Empty)
then obtain x where x:"x \<in> explode A" ..
from iffD1[OF wf_eq_minimal wf, rule_format, where Q="explode A", OF x]
obtain z where "z \<in> explode A \<and> (\<forall>y. (y, z) \<in> R \<longrightarrow> y \<notin> explode A)" by auto
then show "\<exists>x. Elem x A \<and> (\<forall>y. (y, x) \<in> R \<longrightarrow> \<not> Elem y A)"
apply (rule_tac exI[where x = z])
apply (simp add: explode_def)
done
qed
qed
lemma wf_eq_wfzf: "(wf R \<and> set_like R) = wfzf R"
apply (auto simp add: wfzf_implies_wf)
apply (auto simp add: wfzf_def wf_implies_regular)
done
lemma wfzf_trancl: "wfzf R \<Longrightarrow> wfzf (R^+)"
by (auto simp add: wf_eq_wfzf[symmetric] implodeable_Ext_trancl wf_trancl)
lemma Ext_subset_mono: "R \<subseteq> S \<Longrightarrow> Ext R y \<subseteq> Ext S y"
by (auto simp add: Ext_def)
lemma set_like_subset: "set_like R \<Longrightarrow> S \<subseteq> R \<Longrightarrow> set_like S"
apply (auto simp add: set_like_def)
apply (erule_tac x=y in allE)
apply (drule_tac y=y in Ext_subset_mono)
apply (auto simp add: image_def)
apply (rule_tac x="Sep x (% z. z \<in> (Ext S y))" in exI)
apply (auto simp add: explode_def Sep)
done
lemma wfzf_subset: "wfzf S \<Longrightarrow> R \<subseteq> S \<Longrightarrow> wfzf R"
by (auto intro: set_like_subset wf_subset simp add: wf_eq_wfzf[symmetric])
end