src/ZF/Constructible/Formula.thy

renamed M_triv_axioms to M_trivial and M_axioms to M_basic

(*  Title:      ZF/Constructible/Formula.thy
    ID: $Id$
    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
    Copyright   2002  University of Cambridge
*)

header {* First-Order Formulas and the Definition of the Class L *}

theory Formula = Main:

subsection{*Internalized formulas of FOL*}

text{*De Bruijn representation.
  Unbound variables get their denotations from an environment.*}

consts   formula :: i
datatype
  "formula" = Member ("x: nat", "y: nat")
            | Equal  ("x: nat", "y: nat")
            | Nand ("p: formula", "q: formula")
            | Forall ("p: formula")

declare formula.intros [TC]

constdefs Neg :: "i=>i"
    "Neg(p) == Nand(p,p)"

constdefs And :: "[i,i]=>i"
    "And(p,q) == Neg(Nand(p,q))"

constdefs Or :: "[i,i]=>i"
    "Or(p,q) == Nand(Neg(p),Neg(q))"

constdefs Implies :: "[i,i]=>i"
    "Implies(p,q) == Nand(p,Neg(q))"

constdefs Iff :: "[i,i]=>i"
    "Iff(p,q) == And(Implies(p,q), Implies(q,p))"

constdefs Exists :: "i=>i"
    "Exists(p) == Neg(Forall(Neg(p)))";

lemma Neg_type [TC]: "p \<in> formula ==> Neg(p) \<in> formula"
by (simp add: Neg_def) 

lemma And_type [TC]: "[| p \<in> formula; q \<in> formula |] ==> And(p,q) \<in> formula"
by (simp add: And_def) 

lemma Or_type [TC]: "[| p \<in> formula; q \<in> formula |] ==> Or(p,q) \<in> formula"
by (simp add: Or_def) 

lemma Implies_type [TC]:
     "[| p \<in> formula; q \<in> formula |] ==> Implies(p,q) \<in> formula"
by (simp add: Implies_def) 

lemma Iff_type [TC]:
     "[| p \<in> formula; q \<in> formula |] ==> Iff(p,q) \<in> formula"
by (simp add: Iff_def) 

lemma Exists_type [TC]: "p \<in> formula ==> Exists(p) \<in> formula"
by (simp add: Exists_def) 


consts   satisfies :: "[i,i]=>i"
primrec (*explicit lambda is required because the environment varies*)
  "satisfies(A,Member(x,y)) = 
      (\<lambda>env \<in> list(A). bool_of_o (nth(x,env) \<in> nth(y,env)))"

  "satisfies(A,Equal(x,y)) = 
      (\<lambda>env \<in> list(A). bool_of_o (nth(x,env) = nth(y,env)))"

  "satisfies(A,Nand(p,q)) =
      (\<lambda>env \<in> list(A). not ((satisfies(A,p)`env) and (satisfies(A,q)`env)))"

  "satisfies(A,Forall(p)) = 
      (\<lambda>env \<in> list(A). bool_of_o (\<forall>x\<in>A. satisfies(A,p) ` (Cons(x,env)) = 1))"


lemma "p \<in> formula ==> satisfies(A,p) \<in> list(A) -> bool"
by (induct_tac p, simp_all) 

syntax sats :: "[i,i,i] => o"
translations "sats(A,p,env)" == "satisfies(A,p)`env = 1"

lemma [simp]:
  "env \<in> list(A) 
   ==> sats(A, Member(x,y), env) <-> nth(x,env) \<in> nth(y,env)"
by simp

lemma [simp]:
  "env \<in> list(A) 
   ==> sats(A, Equal(x,y), env) <-> nth(x,env) = nth(y,env)"
by simp

lemma sats_Nand_iff [simp]:
  "env \<in> list(A) 
   ==> (sats(A, Nand(p,q), env)) <-> ~ (sats(A,p,env) & sats(A,q,env))" 
by (simp add: Bool.and_def Bool.not_def cond_def) 

lemma sats_Forall_iff [simp]:
  "env \<in> list(A) 
   ==> sats(A, Forall(p), env) <-> (\<forall>x\<in>A. sats(A, p, Cons(x,env)))"
by simp

declare satisfies.simps [simp del]; 

subsection{*Dividing line between primitive and derived connectives*}

lemma sats_Neg_iff [simp]:
  "env \<in> list(A) 
   ==> sats(A, Neg(p), env) <-> ~ sats(A,p,env)"
by (simp add: Neg_def) 

lemma sats_And_iff [simp]:
  "env \<in> list(A) 
   ==> (sats(A, And(p,q), env)) <-> sats(A,p,env) & sats(A,q,env)"
by (simp add: And_def) 

lemma sats_Or_iff [simp]:
  "env \<in> list(A) 
   ==> (sats(A, Or(p,q), env)) <-> sats(A,p,env) | sats(A,q,env)"
by (simp add: Or_def)

lemma sats_Implies_iff [simp]:
  "env \<in> list(A) 
   ==> (sats(A, Implies(p,q), env)) <-> (sats(A,p,env) --> sats(A,q,env))"
by (simp add: Implies_def, blast) 

lemma sats_Iff_iff [simp]:
  "env \<in> list(A) 
   ==> (sats(A, Iff(p,q), env)) <-> (sats(A,p,env) <-> sats(A,q,env))"
by (simp add: Iff_def, blast) 

lemma sats_Exists_iff [simp]:
  "env \<in> list(A) 
   ==> sats(A, Exists(p), env) <-> (\<exists>x\<in>A. sats(A, p, Cons(x,env)))"
by (simp add: Exists_def)


subsubsection{*Derived rules to help build up formulas*}

lemma mem_iff_sats:
      "[| nth(i,env) = x; nth(j,env) = y; env \<in> list(A)|]
       ==> (x\<in>y) <-> sats(A, Member(i,j), env)" 
by (simp add: satisfies.simps)

lemma equal_iff_sats:
      "[| nth(i,env) = x; nth(j,env) = y; env \<in> list(A)|]
       ==> (x=y) <-> sats(A, Equal(i,j), env)" 
by (simp add: satisfies.simps)

lemma not_iff_sats:
      "[| P <-> sats(A,p,env); env \<in> list(A)|]
       ==> (~P) <-> sats(A, Neg(p), env)"
by simp

lemma conj_iff_sats:
      "[| P <-> sats(A,p,env); Q <-> sats(A,q,env); env \<in> list(A)|]
       ==> (P & Q) <-> sats(A, And(p,q), env)"
by (simp add: sats_And_iff)

lemma disj_iff_sats:
      "[| P <-> sats(A,p,env); Q <-> sats(A,q,env); env \<in> list(A)|]
       ==> (P | Q) <-> sats(A, Or(p,q), env)"
by (simp add: sats_Or_iff)

lemma iff_iff_sats:
      "[| P <-> sats(A,p,env); Q <-> sats(A,q,env); env \<in> list(A)|]
       ==> (P <-> Q) <-> sats(A, Iff(p,q), env)"
by (simp add: sats_Forall_iff) 

lemma imp_iff_sats:
      "[| P <-> sats(A,p,env); Q <-> sats(A,q,env); env \<in> list(A)|]
       ==> (P --> Q) <-> sats(A, Implies(p,q), env)"
by (simp add: sats_Forall_iff) 

lemma ball_iff_sats:
      "[| !!x. x\<in>A ==> P(x) <-> sats(A, p, Cons(x, env)); env \<in> list(A)|]
       ==> (\<forall>x\<in>A. P(x)) <-> sats(A, Forall(p), env)"
by (simp add: sats_Forall_iff) 

lemma bex_iff_sats:
      "[| !!x. x\<in>A ==> P(x) <-> sats(A, p, Cons(x, env)); env \<in> list(A)|]
       ==> (\<exists>x\<in>A. P(x)) <-> sats(A, Exists(p), env)"
by (simp add: sats_Exists_iff) 

lemmas FOL_iff_sats = 
        mem_iff_sats equal_iff_sats not_iff_sats conj_iff_sats
        disj_iff_sats imp_iff_sats iff_iff_sats imp_iff_sats ball_iff_sats
        bex_iff_sats

constdefs incr_var :: "[i,i]=>i"
    "incr_var(x,lev) == if x<lev then x else succ(x)"

lemma incr_var_lt: "x<lev ==> incr_var(x,lev) = x"
by (simp add: incr_var_def)

lemma incr_var_le: "lev\<le>x ==> incr_var(x,lev) = succ(x)"
apply (simp add: incr_var_def) 
apply (blast dest: lt_trans1) 
done

consts   incr_bv :: "i=>i"
primrec
  "incr_bv(Member(x,y)) = 
      (\<lambda>lev \<in> nat. Member (incr_var(x,lev), incr_var(y,lev)))"

  "incr_bv(Equal(x,y)) = 
      (\<lambda>lev \<in> nat. Equal (incr_var(x,lev), incr_var(y,lev)))"

  "incr_bv(Nand(p,q)) =
      (\<lambda>lev \<in> nat. Nand (incr_bv(p)`lev, incr_bv(q)`lev))"

  "incr_bv(Forall(p)) = 
      (\<lambda>lev \<in> nat. Forall (incr_bv(p) ` succ(lev)))"


constdefs incr_boundvars :: "i => i"
    "incr_boundvars(p) == incr_bv(p)`0"


lemma [TC]: "x \<in> nat ==> incr_var(x,lev) \<in> nat"
by (simp add: incr_var_def) 

lemma incr_bv_type [TC]: "p \<in> formula ==> incr_bv(p) \<in> nat -> formula"
by (induct_tac p, simp_all) 

lemma incr_boundvars_type [TC]: "p \<in> formula ==> incr_boundvars(p) \<in> formula"
by (simp add: incr_boundvars_def) 

(*Obviously DPow is closed under complements and finite intersections and
unions.  Needs an inductive lemma to allow two lists of parameters to 
be combined.*)

lemma sats_incr_bv_iff [rule_format]:
  "[| p \<in> formula; env \<in> list(A); x \<in> A |]
   ==> \<forall>bvs \<in> list(A). 
           sats(A, incr_bv(p) ` length(bvs), bvs @ Cons(x,env)) <-> 
           sats(A, p, bvs@env)"
apply (induct_tac p)
apply (simp_all add: incr_var_def nth_append succ_lt_iff length_type)
apply (auto simp add: diff_succ not_lt_iff_le)
done

(*UNUSED*)
lemma sats_incr_boundvars_iff:
  "[| p \<in> formula; env \<in> list(A); x \<in> A |]
   ==> sats(A, incr_boundvars(p), Cons(x,env)) <-> sats(A, p, env)"
apply (insert sats_incr_bv_iff [of p env A x Nil])
apply (simp add: incr_boundvars_def) 
done

(*UNUSED
lemma formula_add_params [rule_format]:
  "[| p \<in> formula; n \<in> nat |]
   ==> \<forall>bvs \<in> list(A). \<forall>env \<in> list(A). 
         length(bvs) = n --> 
         sats(A, iterates(incr_boundvars,n,p), bvs@env) <-> sats(A, p, env)"
apply (induct_tac n, simp, clarify) 
apply (erule list.cases)
apply (auto simp add: sats_incr_boundvars_iff)  
done
*)

consts   arity :: "i=>i"
primrec
  "arity(Member(x,y)) = succ(x) \<union> succ(y)"

  "arity(Equal(x,y)) = succ(x) \<union> succ(y)"

  "arity(Nand(p,q)) = arity(p) \<union> arity(q)"

  "arity(Forall(p)) = nat_case(0, %x. x, arity(p))"


lemma arity_type [TC]: "p \<in> formula ==> arity(p) \<in> nat"
by (induct_tac p, simp_all) 

lemma arity_Neg [simp]: "arity(Neg(p)) = arity(p)"
by (simp add: Neg_def) 

lemma arity_And [simp]: "arity(And(p,q)) = arity(p) \<union> arity(q)"
by (simp add: And_def) 

lemma arity_Or [simp]: "arity(Or(p,q)) = arity(p) \<union> arity(q)"
by (simp add: Or_def) 

lemma arity_Implies [simp]: "arity(Implies(p,q)) = arity(p) \<union> arity(q)"
by (simp add: Implies_def) 

lemma arity_Iff [simp]: "arity(Iff(p,q)) = arity(p) \<union> arity(q)"
by (simp add: Iff_def, blast)

lemma arity_Exists [simp]: "arity(Exists(p)) = nat_case(0, %x. x, arity(p))"
by (simp add: Exists_def) 


lemma arity_sats_iff [rule_format]:
  "[| p \<in> formula; extra \<in> list(A) |]
   ==> \<forall>env \<in> list(A). 
           arity(p) \<le> length(env) --> 
           sats(A, p, env @ extra) <-> sats(A, p, env)"
apply (induct_tac p)
apply (simp_all add: nth_append Un_least_lt_iff arity_type nat_imp_quasinat
                split: split_nat_case, auto) 
done

lemma arity_sats1_iff:
  "[| arity(p) \<le> succ(length(env)); p \<in> formula; x \<in> A; env \<in> list(A); 
    extra \<in> list(A) |]
   ==> sats(A, p, Cons(x, env @ extra)) <-> sats(A, p, Cons(x, env))"
apply (insert arity_sats_iff [of p extra A "Cons(x,env)"])
apply simp 
done

(*the following two lemmas prevent huge case splits in arity_incr_bv_lemma*)
lemma incr_var_lemma:
     "[| x \<in> nat; y \<in> nat; lev \<le> x |]
      ==> succ(x) \<union> incr_var(y,lev) = succ(x \<union> y)"
apply (simp add: incr_var_def Ord_Un_if, auto)
  apply (blast intro: leI)
 apply (simp add: not_lt_iff_le)  
 apply (blast intro: le_anti_sym) 
apply (blast dest: lt_trans2) 
done

lemma incr_And_lemma:
     "y < x ==> y \<union> succ(x) = succ(x \<union> y)"
apply (simp add: Ord_Un_if lt_Ord lt_Ord2 succ_lt_iff) 
apply (blast dest: lt_asym) 
done

lemma arity_incr_bv_lemma [rule_format]:
  "p \<in> formula 
   ==> \<forall>n \<in> nat. arity (incr_bv(p) ` n) = 
                 (if n < arity(p) then succ(arity(p)) else arity(p))"
apply (induct_tac p) 
apply (simp_all add: imp_disj not_lt_iff_le Un_least_lt_iff lt_Un_iff le_Un_iff
                     succ_Un_distrib [symmetric] incr_var_lt incr_var_le
                     Un_commute incr_var_lemma arity_type nat_imp_quasinat
            split: split_nat_case) 
 txt{*the Forall case reduces to linear arithmetic*}
 prefer 2
 apply clarify 
 apply (blast dest: lt_trans1) 
txt{*left with the And case*}
apply safe
 apply (blast intro: incr_And_lemma lt_trans1) 
apply (subst incr_And_lemma)
 apply (blast intro: lt_trans1) 
apply (simp add: Un_commute)
done

lemma arity_incr_boundvars_eq:
  "p \<in> formula
   ==> arity(incr_boundvars(p)) =
        (if 0 < arity(p) then succ(arity(p)) else arity(p))"
apply (insert arity_incr_bv_lemma [of p 0])
apply (simp add: incr_boundvars_def) 
done

lemma arity_iterates_incr_boundvars_eq:
  "[| p \<in> formula; n \<in> nat |]
   ==> arity(incr_boundvars^n(p)) =
         (if 0 < arity(p) then n #+ arity(p) else arity(p))"
apply (induct_tac n) 
apply (simp_all add: arity_incr_boundvars_eq not_lt_iff_le) 
done


subsection{*Renaming all but the first bound variable*}

constdefs incr_bv1 :: "i => i"
    "incr_bv1(p) == incr_bv(p)`1"


lemma incr_bv1_type [TC]: "p \<in> formula ==> incr_bv1(p) \<in> formula"
by (simp add: incr_bv1_def) 

(*For renaming all but the bound variable at level 0*)
lemma sats_incr_bv1_iff [rule_format]:
  "[| p \<in> formula; env \<in> list(A); x \<in> A; y \<in> A |]
   ==> sats(A, incr_bv1(p), Cons(x, Cons(y, env))) <-> 
       sats(A, p, Cons(x,env))"
apply (insert sats_incr_bv_iff [of p env A y "Cons(x,Nil)"])
apply (simp add: incr_bv1_def) 
done

lemma formula_add_params1 [rule_format]:
  "[| p \<in> formula; n \<in> nat; x \<in> A |]
   ==> \<forall>bvs \<in> list(A). \<forall>env \<in> list(A). 
          length(bvs) = n --> 
          sats(A, iterates(incr_bv1, n, p), Cons(x, bvs@env)) <-> 
          sats(A, p, Cons(x,env))"
apply (induct_tac n, simp, clarify) 
apply (erule list.cases)
apply (simp_all add: sats_incr_bv1_iff) 
done


lemma arity_incr_bv1_eq:
  "p \<in> formula
   ==> arity(incr_bv1(p)) =
        (if 1 < arity(p) then succ(arity(p)) else arity(p))"
apply (insert arity_incr_bv_lemma [of p 1])
apply (simp add: incr_bv1_def) 
done

lemma arity_iterates_incr_bv1_eq:
  "[| p \<in> formula; n \<in> nat |]
   ==> arity(incr_bv1^n(p)) =
         (if 1 < arity(p) then n #+ arity(p) else arity(p))"
apply (induct_tac n) 
apply (simp_all add: arity_incr_bv1_eq)
apply (simp add: not_lt_iff_le)
apply (blast intro: le_trans add_le_self2 arity_type) 
done


(*Definable powerset operation: Kunen's definition 1.1, page 165.*)
constdefs DPow :: "i => i"
  "DPow(A) == {X \<in> Pow(A). 
               \<exists>env \<in> list(A). \<exists>p \<in> formula. 
                 arity(p) \<le> succ(length(env)) & 
                 X = {x\<in>A. sats(A, p, Cons(x,env))}}"

lemma DPowI:
  "[|env \<in> list(A);  p \<in> formula;  arity(p) \<le> succ(length(env))|]
   ==> {x\<in>A. sats(A, p, Cons(x,env))} \<in> DPow(A)"
by (simp add: DPow_def, blast) 

text{*With this rule we can specify @{term p} later.*}
lemma DPowI2 [rule_format]:
  "[|\<forall>x\<in>A. P(x) <-> sats(A, p, Cons(x,env));
     env \<in> list(A);  p \<in> formula;  arity(p) \<le> succ(length(env))|]
   ==> {x\<in>A. P(x)} \<in> DPow(A)"
by (simp add: DPow_def, blast) 

lemma DPowD:
  "X \<in> DPow(A) 
   ==> X <= A &
       (\<exists>env \<in> list(A). 
        \<exists>p \<in> formula. arity(p) \<le> succ(length(env)) & 
                      X = {x\<in>A. sats(A, p, Cons(x,env))})"
by (simp add: DPow_def) 

lemmas DPow_imp_subset = DPowD [THEN conjunct1]

(*Lemma 1.2*)
lemma "[| p \<in> formula; env \<in> list(A); arity(p) \<le> succ(length(env)) |] 
       ==> {x\<in>A. sats(A, p, Cons(x,env))} \<in> DPow(A)"
by (blast intro: DPowI)

lemma DPow_subset_Pow: "DPow(A) <= Pow(A)"
by (simp add: DPow_def, blast)

lemma empty_in_DPow: "0 \<in> DPow(A)"
apply (simp add: DPow_def)
apply (rule_tac x=Nil in bexI) 
 apply (rule_tac x="Neg(Equal(0,0))" in bexI) 
  apply (auto simp add: Un_least_lt_iff) 
done

lemma Compl_in_DPow: "X \<in> DPow(A) ==> (A-X) \<in> DPow(A)"
apply (simp add: DPow_def, clarify, auto) 
apply (rule bexI) 
 apply (rule_tac x="Neg(p)" in bexI) 
  apply auto 
done

lemma Int_in_DPow: "[| X \<in> DPow(A); Y \<in> DPow(A) |] ==> X Int Y \<in> DPow(A)"
apply (simp add: DPow_def, auto) 
apply (rename_tac envp p envq q) 
apply (rule_tac x="envp@envq" in bexI) 
 apply (rule_tac x="And(p, iterates(incr_bv1,length(envp),q))" in bexI)
  apply typecheck
apply (rule conjI) 
(*finally check the arity!*)
 apply (simp add: arity_iterates_incr_bv1_eq length_app Un_least_lt_iff)
 apply (force intro: add_le_self le_trans) 
apply (simp add: arity_sats1_iff formula_add_params1, blast) 
done

lemma Un_in_DPow: "[| X \<in> DPow(A); Y \<in> DPow(A) |] ==> X Un Y \<in> DPow(A)"
apply (subgoal_tac "X Un Y = A - ((A-X) Int (A-Y))") 
apply (simp add: Int_in_DPow Compl_in_DPow) 
apply (simp add: DPow_def, blast) 
done

lemma singleton_in_DPow: "x \<in> A ==> {x} \<in> DPow(A)"
apply (simp add: DPow_def)
apply (rule_tac x="Cons(x,Nil)" in bexI) 
 apply (rule_tac x="Equal(0,1)" in bexI) 
  apply typecheck
apply (force simp add: succ_Un_distrib [symmetric])  
done

lemma cons_in_DPow: "[| a \<in> A; X \<in> DPow(A) |] ==> cons(a,X) \<in> DPow(A)"
apply (rule cons_eq [THEN subst]) 
apply (blast intro: singleton_in_DPow Un_in_DPow) 
done

(*Part of Lemma 1.3*)
lemma Fin_into_DPow: "X \<in> Fin(A) ==> X \<in> DPow(A)"
apply (erule Fin.induct) 
 apply (rule empty_in_DPow) 
apply (blast intro: cons_in_DPow) 
done

(*DPow is not monotonic.  For example, let A be some non-constructible set
  of natural numbers, and let B be nat.  Then A<=B and obviously A : DPow(A)
  but A ~: DPow(B).*)
lemma DPow_mono: "A : DPow(B) ==> DPow(A) <= DPow(B)"
apply (simp add: DPow_def, auto) 
(*must use the formula defining A in B to relativize the new formula...*)
oops

lemma DPow_0: "DPow(0) = {0}" 
by (blast intro: empty_in_DPow dest: DPow_imp_subset)

lemma Finite_Pow_subset_Pow: "Finite(A) ==> Pow(A) <= DPow(A)" 
by (blast intro: Fin_into_DPow Finite_into_Fin Fin_subset)

lemma Finite_DPow_eq_Pow: "Finite(A) ==> DPow(A) = Pow(A)"
apply (rule equalityI) 
apply (rule DPow_subset_Pow) 
apply (erule Finite_Pow_subset_Pow) 
done

(*This may be true but the proof looks difficult, requiring relativization 
lemma DPow_insert: "DPow (cons(a,A)) = DPow(A) Un {cons(a,X) . X: DPow(A)}"
apply (rule equalityI, safe)
oops
*)


subsection{*Internalized formulas for basic concepts*}

subsubsection{*The subset relation*}

constdefs subset_fm :: "[i,i]=>i"
    "subset_fm(x,y) == Forall(Implies(Member(0,succ(x)), Member(0,succ(y))))"

lemma subset_type [TC]: "[| x \<in> nat; y \<in> nat |] ==> subset_fm(x,y) \<in> formula"
by (simp add: subset_fm_def) 

lemma arity_subset_fm [simp]:
     "[| x \<in> nat; y \<in> nat |] ==> arity(subset_fm(x,y)) = succ(x) \<union> succ(y)"
by (simp add: subset_fm_def succ_Un_distrib [symmetric]) 

lemma sats_subset_fm [simp]:
   "[|x < length(env); y \<in> nat; env \<in> list(A); Transset(A)|]
    ==> sats(A, subset_fm(x,y), env) <-> nth(x,env) \<subseteq> nth(y,env)"
apply (frule lt_length_in_nat, assumption)  
apply (simp add: subset_fm_def Transset_def) 
apply (blast intro: nth_type) 
done

subsubsection{*Transitive sets*}

constdefs transset_fm :: "i=>i"
   "transset_fm(x) == Forall(Implies(Member(0,succ(x)), subset_fm(0,succ(x))))"

lemma transset_type [TC]: "x \<in> nat ==> transset_fm(x) \<in> formula"
by (simp add: transset_fm_def) 

lemma arity_transset_fm [simp]:
     "x \<in> nat ==> arity(transset_fm(x)) = succ(x)"
by (simp add: transset_fm_def succ_Un_distrib [symmetric]) 

lemma sats_transset_fm [simp]:
   "[|x < length(env); env \<in> list(A); Transset(A)|]
    ==> sats(A, transset_fm(x), env) <-> Transset(nth(x,env))"
apply (frule lt_nat_in_nat, erule length_type) 
apply (simp add: transset_fm_def Transset_def) 
apply (blast intro: nth_type) 
done

subsubsection{*Ordinals*}

constdefs ordinal_fm :: "i=>i"
   "ordinal_fm(x) == 
      And(transset_fm(x), Forall(Implies(Member(0,succ(x)), transset_fm(0))))"

lemma ordinal_type [TC]: "x \<in> nat ==> ordinal_fm(x) \<in> formula"
by (simp add: ordinal_fm_def) 

lemma arity_ordinal_fm [simp]:
     "x \<in> nat ==> arity(ordinal_fm(x)) = succ(x)"
by (simp add: ordinal_fm_def succ_Un_distrib [symmetric]) 

lemma sats_ordinal_fm:
   "[|x < length(env); env \<in> list(A); Transset(A)|]
    ==> sats(A, ordinal_fm(x), env) <-> Ord(nth(x,env))"
apply (frule lt_nat_in_nat, erule length_type) 
apply (simp add: ordinal_fm_def Ord_def Transset_def)
apply (blast intro: nth_type) 
done


subsection{* Constant Lset: Levels of the Constructible Universe *}

constdefs Lset :: "i=>i"
    "Lset(i) == transrec(i, %x f. \<Union>y\<in>x. DPow(f`y))"

text{*NOT SUITABLE FOR REWRITING -- RECURSIVE!*}
lemma Lset: "Lset(i) = (UN j:i. DPow(Lset(j)))"
by (subst Lset_def [THEN def_transrec], simp)

lemma LsetI: "[|y\<in>x; A \<in> DPow(Lset(y))|] ==> A \<in> Lset(x)";
by (subst Lset, blast)

lemma LsetD: "A \<in> Lset(x) ==> \<exists>y\<in>x. A \<in> DPow(Lset(y))";
apply (insert Lset [of x]) 
apply (blast intro: elim: equalityE) 
done

subsubsection{* Transitivity *}

lemma elem_subset_in_DPow: "[|X \<in> A; X \<subseteq> A|] ==> X \<in> DPow(A)"
apply (simp add: Transset_def DPow_def)
apply (rule_tac x="[X]" in bexI) 
 apply (rule_tac x="Member(0,1)" in bexI) 
  apply (auto simp add: Un_least_lt_iff) 
done

lemma Transset_subset_DPow: "Transset(A) ==> A <= DPow(A)"
apply clarify  
apply (simp add: Transset_def)
apply (blast intro: elem_subset_in_DPow) 
done

lemma Transset_DPow: "Transset(A) ==> Transset(DPow(A))"
apply (simp add: Transset_def) 
apply (blast intro: elem_subset_in_DPow dest: DPowD) 
done

text{*Kunen's VI, 1.6 (a)*}
lemma Transset_Lset: "Transset(Lset(i))"
apply (rule_tac a=i in eps_induct)
apply (subst Lset)
apply (blast intro!: Transset_Union_family Transset_Un Transset_DPow)
done

lemma mem_Lset_imp_subset_Lset: "a \<in> Lset(i) ==> a \<subseteq> Lset(i)"
apply (insert Transset_Lset) 
apply (simp add: Transset_def) 
done

subsubsection{* Monotonicity *}

text{*Kunen's VI, 1.6 (b)*}
lemma Lset_mono [rule_format]:
     "ALL j. i<=j --> Lset(i) <= Lset(j)"
apply (rule_tac a=i in eps_induct)
apply (rule impI [THEN allI])
apply (subst Lset)
apply (subst Lset, blast) 
done

text{*This version lets us remove the premise @{term "Ord(i)"} sometimes.*}
lemma Lset_mono_mem [rule_format]:
     "ALL j. i:j --> Lset(i) <= Lset(j)"
apply (rule_tac a=i in eps_induct)
apply (rule impI [THEN allI])
apply (subst Lset, auto) 
apply (rule rev_bexI, assumption)
apply (blast intro: elem_subset_in_DPow dest: LsetD DPowD) 
done

text{*Useful with Reflection to bump up the ordinal*}
lemma subset_Lset_ltD: "[|A \<subseteq> Lset(i); i < j|] ==> A \<subseteq> Lset(j)"
by (blast dest: ltD [THEN Lset_mono_mem]) 

subsubsection{* 0, successor and limit equations fof Lset *}

lemma Lset_0 [simp]: "Lset(0) = 0"
by (subst Lset, blast)

lemma Lset_succ_subset1: "DPow(Lset(i)) <= Lset(succ(i))"
by (subst Lset, rule succI1 [THEN RepFunI, THEN Union_upper])

lemma Lset_succ_subset2: "Lset(succ(i)) <= DPow(Lset(i))"
apply (subst Lset, rule UN_least)
apply (erule succE) 
 apply blast 
apply clarify
apply (rule elem_subset_in_DPow)
 apply (subst Lset)
 apply blast 
apply (blast intro: dest: DPowD Lset_mono_mem) 
done

lemma Lset_succ: "Lset(succ(i)) = DPow(Lset(i))"
by (intro equalityI Lset_succ_subset1 Lset_succ_subset2) 

lemma Lset_Union [simp]: "Lset(\<Union>(X)) = (\<Union>y\<in>X. Lset(y))"
apply (subst Lset)
apply (rule equalityI)
 txt{*first inclusion*}
 apply (rule UN_least)
 apply (erule UnionE)
 apply (rule subset_trans)
  apply (erule_tac [2] UN_upper, subst Lset, erule UN_upper)
txt{*opposite inclusion*}
apply (rule UN_least)
apply (subst Lset, blast)
done

subsubsection{* Lset applied to Limit ordinals *}

lemma Limit_Lset_eq:
    "Limit(i) ==> Lset(i) = (\<Union>y\<in>i. Lset(y))"
by (simp add: Lset_Union [symmetric] Limit_Union_eq)

lemma lt_LsetI: "[| a: Lset(j);  j<i |] ==> a : Lset(i)"
by (blast dest: Lset_mono [OF le_imp_subset [OF leI]])

lemma Limit_LsetE:
    "[| a: Lset(i);  ~R ==> Limit(i);
        !!x. [| x<i;  a: Lset(x) |] ==> R
     |] ==> R"
apply (rule classical)
apply (rule Limit_Lset_eq [THEN equalityD1, THEN subsetD, THEN UN_E])
  prefer 2 apply assumption
 apply blast 
apply (blast intro: ltI  Limit_is_Ord)
done

subsubsection{* Basic closure properties *}

lemma zero_in_Lset: "y:x ==> 0 : Lset(x)"
by (subst Lset, blast intro: empty_in_DPow)

lemma notin_Lset: "x \<notin> Lset(x)"
apply (rule_tac a=x in eps_induct)
apply (subst Lset)
apply (blast dest: DPowD)  
done


subsection{*Constructible Ordinals: Kunen's VI, 1.9 (b)*}

text{*The subset consisting of the ordinals is definable.*}
lemma Ords_in_DPow: "Transset(A) ==> {x \<in> A. Ord(x)} \<in> DPow(A)"
apply (simp add: DPow_def Collect_subset) 
apply (rule_tac x=Nil in bexI) 
 apply (rule_tac x="ordinal_fm(0)" in bexI) 
apply (simp_all add: sats_ordinal_fm)
done 

lemma Ords_of_Lset_eq: "Ord(i) ==> {x\<in>Lset(i). Ord(x)} = i"
apply (erule trans_induct3)
  apply (simp_all add: Lset_succ Limit_Lset_eq Limit_Union_eq)
txt{*The successor case remains.*} 
apply (rule equalityI)
txt{*First inclusion*}
 apply clarify  
 apply (erule Ord_linear_lt, assumption) 
   apply (blast dest: DPow_imp_subset ltD notE [OF notin_Lset]) 
  apply blast 
 apply (blast dest: ltD)
txt{*Opposite inclusion, @{term "succ(x) \<subseteq> DPow(Lset(x)) \<inter> ON"}*}
apply auto
txt{*Key case: *}
  apply (erule subst, rule Ords_in_DPow [OF Transset_Lset]) 
 apply (blast intro: elem_subset_in_DPow dest: OrdmemD elim: equalityE) 
apply (blast intro: Ord_in_Ord) 
done


lemma Ord_subset_Lset: "Ord(i) ==> i \<subseteq> Lset(i)"
by (subst Ords_of_Lset_eq [symmetric], assumption, fast)

lemma Ord_in_Lset: "Ord(i) ==> i \<in> Lset(succ(i))"
apply (simp add: Lset_succ)
apply (subst Ords_of_Lset_eq [symmetric], assumption, 
       rule Ords_in_DPow [OF Transset_Lset]) 
done

subsubsection{* Unions *}

lemma Union_in_Lset:
     "X \<in> Lset(j) ==> Union(X) \<in> Lset(succ(j))"
apply (insert Transset_Lset)
apply (rule LsetI [OF succI1])
apply (simp add: Transset_def DPow_def) 
apply (intro conjI, blast)
txt{*Now to create the formula @{term "\<exists>y. y \<in> X \<and> x \<in> y"} *}
apply (rule_tac x="Cons(X,Nil)" in bexI) 
 apply (rule_tac x="Exists(And(Member(0,2), Member(1,0)))" in bexI) 
  apply typecheck
apply (simp add: succ_Un_distrib [symmetric], blast) 
done

lemma Union_in_LLimit:
     "[| X: Lset(i);  Limit(i) |] ==> Union(X) : Lset(i)"
apply (rule Limit_LsetE, assumption+)
apply (blast intro: Limit_has_succ lt_LsetI Union_in_Lset)
done

subsubsection{* Finite sets and ordered pairs *}

lemma singleton_in_Lset: "a: Lset(i) ==> {a} : Lset(succ(i))"
by (simp add: Lset_succ singleton_in_DPow) 

lemma doubleton_in_Lset:
     "[| a: Lset(i);  b: Lset(i) |] ==> {a,b} : Lset(succ(i))"
by (simp add: Lset_succ empty_in_DPow cons_in_DPow) 

lemma Pair_in_Lset:
    "[| a: Lset(i);  b: Lset(i); Ord(i) |] ==> <a,b> : Lset(succ(succ(i)))"
apply (unfold Pair_def)
apply (blast intro: doubleton_in_Lset) 
done

lemma singleton_in_LLimit:
    "[| a: Lset(i);  Limit(i) |] ==> {a} : Lset(i)"
apply (erule Limit_LsetE, assumption)
apply (erule singleton_in_Lset [THEN lt_LsetI])
apply (blast intro: Limit_has_succ) 
done

lemmas Lset_UnI1 = Un_upper1 [THEN Lset_mono [THEN subsetD], standard]
lemmas Lset_UnI2 = Un_upper2 [THEN Lset_mono [THEN subsetD], standard]

text{*Hard work is finding a single j:i such that {a,b}<=Lset(j)*}
lemma doubleton_in_LLimit:
    "[| a: Lset(i);  b: Lset(i);  Limit(i) |] ==> {a,b} : Lset(i)"
apply (erule Limit_LsetE, assumption)
apply (erule Limit_LsetE, assumption)
apply (blast intro: lt_LsetI [OF doubleton_in_Lset]
                    Lset_UnI1 Lset_UnI2 Limit_has_succ Un_least_lt)
done

lemma Pair_in_LLimit:
    "[| a: Lset(i);  b: Lset(i);  Limit(i) |] ==> <a,b> : Lset(i)"
txt{*Infer that a, b occur at ordinals x,xa < i.*}
apply (erule Limit_LsetE, assumption)
apply (erule Limit_LsetE, assumption)
txt{*Infer that succ(succ(x Un xa)) < i *}
apply (blast intro: lt_Ord lt_LsetI [OF Pair_in_Lset]
                    Lset_UnI1 Lset_UnI2 Limit_has_succ Un_least_lt)
done

lemma product_LLimit: "Limit(i) ==> Lset(i) * Lset(i) <= Lset(i)"
by (blast intro: Pair_in_LLimit)

lemmas Sigma_subset_LLimit = subset_trans [OF Sigma_mono product_LLimit]

lemma nat_subset_LLimit: "Limit(i) ==> nat \<subseteq> Lset(i)"
by (blast dest: Ord_subset_Lset nat_le_Limit le_imp_subset Limit_is_Ord)

lemma nat_into_LLimit: "[| n: nat;  Limit(i) |] ==> n : Lset(i)"
by (blast intro: nat_subset_LLimit [THEN subsetD])


subsubsection{* Closure under disjoint union *}

lemmas zero_in_LLimit = Limit_has_0 [THEN ltD, THEN zero_in_Lset, standard]

lemma one_in_LLimit: "Limit(i) ==> 1 : Lset(i)"
by (blast intro: nat_into_LLimit)

lemma Inl_in_LLimit:
    "[| a: Lset(i); Limit(i) |] ==> Inl(a) : Lset(i)"
apply (unfold Inl_def)
apply (blast intro: zero_in_LLimit Pair_in_LLimit)
done

lemma Inr_in_LLimit:
    "[| b: Lset(i); Limit(i) |] ==> Inr(b) : Lset(i)"
apply (unfold Inr_def)
apply (blast intro: one_in_LLimit Pair_in_LLimit)
done

lemma sum_LLimit: "Limit(i) ==> Lset(i) + Lset(i) <= Lset(i)"
by (blast intro!: Inl_in_LLimit Inr_in_LLimit)

lemmas sum_subset_LLimit = subset_trans [OF sum_mono sum_LLimit]


text{*The constructible universe and its rank function*}
constdefs
  L :: "i=>o" --{*Kunen's definition VI, 1.5, page 167*}
    "L(x) == \<exists>i. Ord(i) & x \<in> Lset(i)"
  
  lrank :: "i=>i" --{*Kunen's definition VI, 1.7*}
    "lrank(x) == \<mu>i. x \<in> Lset(succ(i))"

lemma L_I: "[|x \<in> Lset(i); Ord(i)|] ==> L(x)"
by (simp add: L_def, blast)

lemma L_D: "L(x) ==> \<exists>i. Ord(i) & x \<in> Lset(i)"
by (simp add: L_def)

lemma Ord_lrank [simp]: "Ord(lrank(a))"
by (simp add: lrank_def)

lemma Lset_lrank_lt [rule_format]: "Ord(i) ==> x \<in> Lset(i) --> lrank(x) < i"
apply (erule trans_induct3)
  apply simp   
 apply (simp only: lrank_def) 
 apply (blast intro: Least_le) 
apply (simp_all add: Limit_Lset_eq) 
apply (blast intro: ltI Limit_is_Ord lt_trans) 
done

text{*Kunen's VI, 1.8, and the proof is much less trivial than the text
would suggest.  For a start it need the previous lemma, proved by induction.*}
lemma Lset_iff_lrank_lt: "Ord(i) ==> x \<in> Lset(i) <-> L(x) & lrank(x) < i"
apply (simp add: L_def, auto) 
 apply (blast intro: Lset_lrank_lt) 
 apply (unfold lrank_def) 
apply (drule succI1 [THEN Lset_mono_mem, THEN subsetD]) 
apply (drule_tac P="\<lambda>i. x \<in> Lset(succ(i))" in LeastI, assumption) 
apply (blast intro!: le_imp_subset Lset_mono [THEN subsetD]) 
done

lemma Lset_succ_lrank_iff [simp]: "x \<in> Lset(succ(lrank(x))) <-> L(x)"
by (simp add: Lset_iff_lrank_lt)

text{*Kunen's VI, 1.9 (a)*}
lemma lrank_of_Ord: "Ord(i) ==> lrank(i) = i"
apply (unfold lrank_def) 
apply (rule Least_equality) 
  apply (erule Ord_in_Lset) 
 apply assumption
apply (insert notin_Lset [of i]) 
apply (blast intro!: le_imp_subset Lset_mono [THEN subsetD]) 
done


lemma Ord_in_L: "Ord(i) ==> L(i)"
by (blast intro: Ord_in_Lset L_I)

text{*This is lrank(lrank(a)) = lrank(a) *}
declare Ord_lrank [THEN lrank_of_Ord, simp]

text{*Kunen's VI, 1.10 *}
lemma Lset_in_Lset_succ: "Lset(i) \<in> Lset(succ(i))";
apply (simp add: Lset_succ DPow_def) 
apply (rule_tac x=Nil in bexI) 
 apply (rule_tac x="Equal(0,0)" in bexI) 
apply auto 
done

lemma lrank_Lset: "Ord(i) ==> lrank(Lset(i)) = i"
apply (unfold lrank_def) 
apply (rule Least_equality) 
  apply (rule Lset_in_Lset_succ) 
 apply assumption
apply clarify 
apply (subgoal_tac "Lset(succ(ia)) <= Lset(i)")
 apply (blast dest: mem_irrefl) 
apply (blast intro!: le_imp_subset Lset_mono) 
done

text{*Kunen's VI, 1.11 *}
lemma Lset_subset_Vset: "Ord(i) ==> Lset(i) <= Vset(i)";
apply (erule trans_induct)
apply (subst Lset) 
apply (subst Vset) 
apply (rule UN_mono [OF subset_refl]) 
apply (rule subset_trans [OF DPow_subset_Pow]) 
apply (rule Pow_mono, blast) 
done

text{*Kunen's VI, 1.12 *}
lemma Lset_subset_Vset': "i \<in> nat ==> Lset(i) = Vset(i)";
apply (erule nat_induct)
 apply (simp add: Vfrom_0) 
apply (simp add: Lset_succ Vset_succ Finite_Vset Finite_DPow_eq_Pow) 
done

text{*Every set of constructible sets is included in some @{term Lset}*} 
lemma subset_Lset:
     "(\<forall>x\<in>A. L(x)) ==> \<exists>i. Ord(i) & A \<subseteq> Lset(i)"
by (rule_tac x = "\<Union>x\<in>A. succ(lrank(x))" in exI, force)

lemma subset_LsetE:
     "[|\<forall>x\<in>A. L(x);
        !!i. [|Ord(i); A \<subseteq> Lset(i)|] ==> P|]
      ==> P"
by (blast dest: subset_Lset) 

subsection{*For L to satisfy the ZF axioms*}

theorem Union_in_L: "L(X) ==> L(Union(X))"
apply (simp add: L_def, clarify) 
apply (drule Ord_imp_greater_Limit) 
apply (blast intro: lt_LsetI Union_in_LLimit Limit_is_Ord) 
done

theorem doubleton_in_L: "[| L(a); L(b) |] ==> L({a, b})"
apply (simp add: L_def, clarify) 
apply (drule Ord2_imp_greater_Limit, assumption) 
apply (blast intro: lt_LsetI doubleton_in_LLimit Limit_is_Ord) 
done

subsubsection{*For L to satisfy Powerset *}

lemma LPow_env_typing:
    "[| y : Lset(i); Ord(i); y \<subseteq> X |] 
     ==> \<exists>z \<in> Pow(X). y \<in> Lset(succ(lrank(z)))"
by (auto intro: L_I iff: Lset_succ_lrank_iff) 

lemma LPow_in_Lset:
     "[|X \<in> Lset(i); Ord(i)|] ==> \<exists>j. Ord(j) & {y \<in> Pow(X). L(y)} \<in> Lset(j)"
apply (rule_tac x="succ(\<Union>y \<in> Pow(X). succ(lrank(y)))" in exI)
apply simp 
apply (rule LsetI [OF succI1])
apply (simp add: DPow_def) 
apply (intro conjI, clarify) 
 apply (rule_tac a=x in UN_I, simp+)  
txt{*Now to create the formula @{term "y \<subseteq> X"} *}
apply (rule_tac x="Cons(X,Nil)" in bexI) 
 apply (rule_tac x="subset_fm(0,1)" in bexI) 
  apply typecheck
 apply (rule conjI) 
apply (simp add: succ_Un_distrib [symmetric]) 
apply (rule equality_iffI) 
apply (simp add: Transset_UN [OF Transset_Lset] LPow_env_typing)
apply (auto intro: L_I iff: Lset_succ_lrank_iff) 
done

theorem LPow_in_L: "L(X) ==> L({y \<in> Pow(X). L(y)})"
by (blast intro: L_I dest: L_D LPow_in_Lset)


subsection{*Eliminating @{term arity} from the Definition of @{term Lset}*}


lemma nth_zero_eq_0: "n \<in> nat ==> nth(n,[0]) = 0"
by (induct_tac n, auto)

lemma sats_app_0_iff [rule_format]:
  "[| p \<in> formula; 0 \<in> A |]
   ==> \<forall>env \<in> list(A). sats(A,p, env@[0]) <-> sats(A,p,env)"
apply (induct_tac p)
apply (simp_all del: app_Cons add: app_Cons [symmetric]
		add: nth_zero_eq_0 nth_append not_lt_iff_le nth_eq_0)
done

lemma sats_app_zeroes_iff:
  "[| p \<in> formula; 0 \<in> A; env \<in> list(A); n \<in> nat |]
   ==> sats(A,p,env @ repeat(0,n)) <-> sats(A,p,env)"
apply (induct_tac n, simp) 
apply (simp del: repeat.simps
            add: repeat_succ_app sats_app_0_iff app_assoc [symmetric]) 
done

lemma exists_bigger_env:
  "[| p \<in> formula; 0 \<in> A; env \<in> list(A) |]
   ==> \<exists>env' \<in> list(A). arity(p) \<le> succ(length(env')) & 
              (\<forall>a\<in>A. sats(A,p,Cons(a,env')) <-> sats(A,p,Cons(a,env)))"
apply (rule_tac x="env @ repeat(0,arity(p))" in bexI) 
apply (simp del: app_Cons add: app_Cons [symmetric]
	    add: length_repeat sats_app_zeroes_iff, typecheck)
done


text{*A simpler version of @{term DPow}: no arity check!*}
constdefs DPow' :: "i => i"
  "DPow'(A) == {X \<in> Pow(A). 
                \<exists>env \<in> list(A). \<exists>p \<in> formula. 
                    X = {x\<in>A. sats(A, p, Cons(x,env))}}"

lemma DPow_subset_DPow': "DPow(A) <= DPow'(A)";
by (simp add: DPow_def DPow'_def, blast)

lemma DPow'_0: "DPow'(0) = {0}"
by (auto simp add: DPow'_def)

lemma DPow'_subset_DPow: "0 \<in> A ==> DPow'(A) \<subseteq> DPow(A)"
apply (auto simp add: DPow'_def DPow_def) 
apply (frule exists_bigger_env, assumption+, force)  
done

lemma DPow_eq_DPow': "Transset(A) ==> DPow(A) = DPow'(A)"
apply (drule Transset_0_disj) 
apply (erule disjE) 
 apply (simp add: DPow'_0 DPow_0) 
apply (rule equalityI)
 apply (rule DPow_subset_DPow') 
apply (erule DPow'_subset_DPow) 
done

text{*And thus we can relativize @{term Lset} without bothering with
      @{term arity} and @{term length}*}
lemma Lset_eq_transrec_DPow': "Lset(i) = transrec(i, %x f. \<Union>y\<in>x. DPow'(f`y))"
apply (rule_tac a=i in eps_induct)
apply (subst Lset)
apply (subst transrec)
apply (simp only: DPow_eq_DPow' [OF Transset_Lset], simp) 
done

text{*With this rule we can specify @{term p} later and don't worry about
      arities at all!*}
lemma DPow_LsetI [rule_format]:
  "[|\<forall>x\<in>Lset(i). P(x) <-> sats(Lset(i), p, Cons(x,env));
     env \<in> list(Lset(i));  p \<in> formula|]
   ==> {x\<in>Lset(i). P(x)} \<in> DPow(Lset(i))"
by (simp add: DPow_eq_DPow' [OF Transset_Lset] DPow'_def, blast) 

end