# Theory L_axioms

```(*  Title:      ZF/Constructible/L_axioms.thy
Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
*)

section ‹The ZF Axioms (Except Separation) in L›

theory L_axioms imports Formula Relative Reflection MetaExists begin

text ‹The class L satisfies the premises of locale ‹M_trivial››

lemma transL: "[| y∈x; L(x) |] ==> L(y)"
apply (insert Transset_Lset)
apply (simp add: Transset_def L_def, blast)
done

lemma nonempty: "L(0)"
apply (blast intro: zero_in_Lset)
done

theorem upair_ax: "upair_ax(L)"
apply (simp add: upair_ax_def upair_def, clarify)
apply (rule_tac x="{x,y}" in rexI)
done

theorem Union_ax: "Union_ax(L)"
apply (simp add: Union_ax_def big_union_def, clarify)
apply (rule_tac x="⋃(x)" in rexI)
apply (blast intro: transL)
done

theorem power_ax: "power_ax(L)"
apply (simp add: power_ax_def powerset_def Relative.subset_def, clarify)
apply (rule_tac x="{y ∈ Pow(x). L(y)}" in rexI)
apply (blast intro: transL)
done

text‹We don't actually need \<^term>‹L› to satisfy the foundation axiom.›
theorem foundation_ax: "foundation_ax(L)"
apply (rule rallI)
apply (cut_tac A=x in foundation)
apply (blast intro: transL)
done

subsection‹For L to satisfy Replacement›

(*Can't move these to Formula unless the definition of univalent is moved
there too!*)

lemma LReplace_in_Lset:
"[|X ∈ Lset(i); univalent(L,X,Q); Ord(i)|]
==> ∃j. Ord(j) & Replace(X, %x y. Q(x,y) & L(y)) ⊆ Lset(j)"
apply (rule_tac x="⋃y ∈ Replace(X, %x y. Q(x,y) & L(y)). succ(lrank(y))"
in exI)
apply simp
apply clarify
apply (rule_tac a=x in UN_I)
apply (blast dest: transL L_I)
done

lemma LReplace_in_L:
"[|L(X); univalent(L,X,Q)|]
==> ∃Y. L(Y) & Replace(X, %x y. Q(x,y) & L(y)) ⊆ Y"
apply (drule L_D, clarify)
apply (drule LReplace_in_Lset, assumption+)
apply (blast intro: L_I Lset_in_Lset_succ)
done

theorem replacement: "replacement(L,P)"
apply (frule LReplace_in_L, assumption+, clarify)
apply (rule_tac x=Y in rexI)
apply (simp_all add: Replace_iff univalent_def, blast)
done

lemma strong_replacementI [rule_format]:
"[| ∀B[L]. separation(L, %u. ∃x[L]. x∈B & P(x,u)) |]
==> strong_replacement(L,P)"
apply (frule replacementD [OF replacement], assumption, clarify)
apply (drule_tac x=A in rspec, clarify)
apply (drule_tac z=Y in separationD, assumption, clarify)
apply (rule_tac x=y in rexI, force, assumption)
done

subsection‹Instantiating the locale ‹M_trivial››
text‹No instances of Separation yet.›

lemma Lset_mono_le: "mono_le_subset(Lset)"
by (simp add: mono_le_subset_def le_imp_subset Lset_mono)

lemma Lset_cont: "cont_Ord(Lset)"
by (simp add: cont_Ord_def Limit_Lset_eq OUnion_def Limit_is_Ord)

lemmas L_nat = Ord_in_L [OF Ord_nat]

theorem M_trivial_L: "M_trivial(L)"
apply (rule M_trivial.intro)
apply (rule M_trans.intro)
apply (erule (1) transL)
apply(rule exI,rule  nonempty)
apply (rule M_trivial_axioms.intro)
apply (rule upair_ax)
apply (rule Union_ax)
done

interpretation L: M_trivial L by (rule M_trivial_L)

(* Replaces the following declarations...
lemmas rall_abs = M_trivial.rall_abs [OF M_trivial_L]
and rex_abs = M_trivial.rex_abs [OF M_trivial_L]
...
declare rall_abs [simp]
declare rex_abs [simp]
...and dozens of similar ones.
*)

subsection‹Instantiation of the locale ‹reflection››

text‹instances of locale constants›

definition
L_F0 :: "[i=>o,i] => i" where
"L_F0(P,y) == μ b. (∃z. L(z) ∧ P(<y,z>)) ⟶ (∃z∈Lset(b). P(<y,z>))"

definition
L_FF :: "[i=>o,i] => i" where
"L_FF(P)   == λa. ⋃y∈Lset(a). L_F0(P,y)"

definition
L_ClEx :: "[i=>o,i] => o" where
"L_ClEx(P) == λa. Limit(a) ∧ normalize(L_FF(P),a) = a"

text‹We must use the meta-existential quantifier; otherwise the reflection
terms become enormous!›
definition
L_Reflects :: "[i=>o,[i,i]=>o] => prop"  (‹(3REFLECTS/ [_,/ _])›) where
"REFLECTS[P,Q] == (⋁Cl. Closed_Unbounded(Cl) &
(∀a. Cl(a) ⟶ (∀x ∈ Lset(a). P(x) ⟷ Q(a,x))))"

theorem Triv_reflection:
"REFLECTS[P, λa x. P(x)]"
apply (rule meta_exI)
apply (rule Closed_Unbounded_Ord)
done

theorem Not_reflection:
"REFLECTS[P,Q] ==> REFLECTS[λx. ~P(x), λa x. ~Q(a,x)]"
apply (unfold L_Reflects_def)
apply (erule meta_exE)
apply (rule_tac x=Cl in meta_exI, simp)
done

theorem And_reflection:
"[| REFLECTS[P,Q]; REFLECTS[P',Q'] |]
==> REFLECTS[λx. P(x) ∧ P'(x), λa x. Q(a,x) ∧ Q'(a,x)]"
apply (unfold L_Reflects_def)
apply (elim meta_exE)
apply (rule_tac x="λa. Cl(a) ∧ Cla(a)" in meta_exI)
done

theorem Or_reflection:
"[| REFLECTS[P,Q]; REFLECTS[P',Q'] |]
==> REFLECTS[λx. P(x) ∨ P'(x), λa x. Q(a,x) ∨ Q'(a,x)]"
apply (unfold L_Reflects_def)
apply (elim meta_exE)
apply (rule_tac x="λa. Cl(a) ∧ Cla(a)" in meta_exI)
done

theorem Imp_reflection:
"[| REFLECTS[P,Q]; REFLECTS[P',Q'] |]
==> REFLECTS[λx. P(x) ⟶ P'(x), λa x. Q(a,x) ⟶ Q'(a,x)]"
apply (unfold L_Reflects_def)
apply (elim meta_exE)
apply (rule_tac x="λa. Cl(a) ∧ Cla(a)" in meta_exI)
done

theorem Iff_reflection:
"[| REFLECTS[P,Q]; REFLECTS[P',Q'] |]
==> REFLECTS[λx. P(x) ⟷ P'(x), λa x. Q(a,x) ⟷ Q'(a,x)]"
apply (unfold L_Reflects_def)
apply (elim meta_exE)
apply (rule_tac x="λa. Cl(a) ∧ Cla(a)" in meta_exI)
done

lemma reflection_Lset: "reflection(Lset)"
by (blast intro: reflection.intro Lset_mono_le Lset_cont
Formula.Pair_in_LLimit)+

theorem Ex_reflection:
"REFLECTS[λx. P(fst(x),snd(x)), λa x. Q(a,fst(x),snd(x))]
==> REFLECTS[λx. ∃z. L(z) ∧ P(x,z), λa x. ∃z∈Lset(a). Q(a,x,z)]"
apply (unfold L_Reflects_def L_ClEx_def L_FF_def L_F0_def L_def)
apply (elim meta_exE)
apply (rule meta_exI)
apply (erule reflection.Ex_reflection [OF reflection_Lset])
done

theorem All_reflection:
"REFLECTS[λx. P(fst(x),snd(x)), λa x. Q(a,fst(x),snd(x))]
==> REFLECTS[λx. ∀z. L(z) ⟶ P(x,z), λa x. ∀z∈Lset(a). Q(a,x,z)]"
apply (unfold L_Reflects_def L_ClEx_def L_FF_def L_F0_def L_def)
apply (elim meta_exE)
apply (rule meta_exI)
apply (erule reflection.All_reflection [OF reflection_Lset])
done

theorem Rex_reflection:
"REFLECTS[ λx. P(fst(x),snd(x)), λa x. Q(a,fst(x),snd(x))]
==> REFLECTS[λx. ∃z[L]. P(x,z), λa x. ∃z∈Lset(a). Q(a,x,z)]"
apply (unfold rex_def)
apply (intro And_reflection Ex_reflection, assumption)
done

theorem Rall_reflection:
"REFLECTS[λx. P(fst(x),snd(x)), λa x. Q(a,fst(x),snd(x))]
==> REFLECTS[λx. ∀z[L]. P(x,z), λa x. ∀z∈Lset(a). Q(a,x,z)]"
apply (unfold rall_def)
apply (intro Imp_reflection All_reflection, assumption)
done

text‹This version handles an alternative form of the bounded quantifier
in the second argument of ‹REFLECTS›.›
theorem Rex_reflection':
"REFLECTS[λx. P(fst(x),snd(x)), λa x. Q(a,fst(x),snd(x))]
==> REFLECTS[λx. ∃z[L]. P(x,z), λa x. ∃z[##Lset(a)]. Q(a,x,z)]"
apply (unfold setclass_def rex_def)
apply (erule Rex_reflection [unfolded rex_def Bex_def])
done

text‹As above.›
theorem Rall_reflection':
"REFLECTS[λx. P(fst(x),snd(x)), λa x. Q(a,fst(x),snd(x))]
==> REFLECTS[λx. ∀z[L]. P(x,z), λa x. ∀z[##Lset(a)]. Q(a,x,z)]"
apply (unfold setclass_def rall_def)
apply (erule Rall_reflection [unfolded rall_def Ball_def])
done

lemmas FOL_reflections =
Triv_reflection Not_reflection And_reflection Or_reflection
Imp_reflection Iff_reflection Ex_reflection All_reflection
Rex_reflection Rall_reflection Rex_reflection' Rall_reflection'

lemma ReflectsD:
"[|REFLECTS[P,Q]; Ord(i)|]
==> ∃j. i<j & (∀x ∈ Lset(j). P(x) ⟷ Q(j,x))"
apply (unfold L_Reflects_def Closed_Unbounded_def)
apply (elim meta_exE, clarify)
apply (blast dest!: UnboundedD)
done

lemma ReflectsE:
"[| REFLECTS[P,Q]; Ord(i);
!!j. [|i<j;  ∀x ∈ Lset(j). P(x) ⟷ Q(j,x)|] ==> R |]
==> R"
by (drule ReflectsD, assumption, blast)

lemma Collect_mem_eq: "{x∈A. x∈B} = A ∩ B"
by blast

subsection‹Internalized Formulas for some Set-Theoretic Concepts›

subsubsection‹Some numbers to help write de Bruijn indices›

abbreviation
digit3 :: i   (‹3›) where "3 == succ(2)"

abbreviation
digit4 :: i   (‹4›) where "4 == succ(3)"

abbreviation
digit5 :: i   (‹5›) where "5 == succ(4)"

abbreviation
digit6 :: i   (‹6›) where "6 == succ(5)"

abbreviation
digit7 :: i   (‹7›) where "7 == succ(6)"

abbreviation
digit8 :: i   (‹8›) where "8 == succ(7)"

abbreviation
digit9 :: i   (‹9›) where "9 == succ(8)"

subsubsection‹The Empty Set, Internalized›

definition
empty_fm :: "i=>i" where
"empty_fm(x) == Forall(Neg(Member(0,succ(x))))"

lemma empty_type [TC]:
"x ∈ nat ==> empty_fm(x) ∈ formula"

lemma sats_empty_fm [simp]:
"[| x ∈ nat; env ∈ list(A)|]
==> sats(A, empty_fm(x), env) ⟷ empty(##A, nth(x,env))"

lemma empty_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y;
i ∈ nat; env ∈ list(A)|]
==> empty(##A, x) ⟷ sats(A, empty_fm(i), env)"
by simp

theorem empty_reflection:
"REFLECTS[λx. empty(L,f(x)),
λi x. empty(##Lset(i),f(x))]"
apply (simp only: empty_def)
apply (intro FOL_reflections)
done

text‹Not used.  But maybe useful?›
lemma Transset_sats_empty_fm_eq_0:
"[| n ∈ nat; env ∈ list(A); Transset(A)|]
==> sats(A, empty_fm(n), env) ⟷ nth(n,env) = 0"
apply (simp add: empty_fm_def empty_def Transset_def, auto)
apply (case_tac "n < length(env)")
apply (frule nth_type, assumption+, blast)
done

subsubsection‹Unordered Pairs, Internalized›

definition
upair_fm :: "[i,i,i]=>i" where
"upair_fm(x,y,z) ==
And(Member(x,z),
And(Member(y,z),
Forall(Implies(Member(0,succ(z)),
Or(Equal(0,succ(x)), Equal(0,succ(y)))))))"

lemma upair_type [TC]:
"[| x ∈ nat; y ∈ nat; z ∈ nat |] ==> upair_fm(x,y,z) ∈ formula"

lemma sats_upair_fm [simp]:
"[| x ∈ nat; y ∈ nat; z ∈ nat; env ∈ list(A)|]
==> sats(A, upair_fm(x,y,z), env) ⟷
upair(##A, nth(x,env), nth(y,env), nth(z,env))"

lemma upair_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y; nth(k,env) = z;
i ∈ nat; j ∈ nat; k ∈ nat; env ∈ list(A)|]
==> upair(##A, x, y, z) ⟷ sats(A, upair_fm(i,j,k), env)"
by (simp)

text‹Useful? At least it refers to "real" unordered pairs›
lemma sats_upair_fm2 [simp]:
"[| x ∈ nat; y ∈ nat; z < length(env); env ∈ list(A); Transset(A)|]
==> sats(A, upair_fm(x,y,z), env) ⟷
nth(z,env) = {nth(x,env), nth(y,env)}"
apply (frule lt_length_in_nat, assumption)
apply (simp add: upair_fm_def Transset_def, auto)
apply (blast intro: nth_type)
done

theorem upair_reflection:
"REFLECTS[λx. upair(L,f(x),g(x),h(x)),
λi x. upair(##Lset(i),f(x),g(x),h(x))]"
apply (intro FOL_reflections)
done

subsubsection‹Ordered pairs, Internalized›

definition
pair_fm :: "[i,i,i]=>i" where
"pair_fm(x,y,z) ==
Exists(And(upair_fm(succ(x),succ(x),0),
Exists(And(upair_fm(succ(succ(x)),succ(succ(y)),0),
upair_fm(1,0,succ(succ(z)))))))"

lemma pair_type [TC]:
"[| x ∈ nat; y ∈ nat; z ∈ nat |] ==> pair_fm(x,y,z) ∈ formula"

lemma sats_pair_fm [simp]:
"[| x ∈ nat; y ∈ nat; z ∈ nat; env ∈ list(A)|]
==> sats(A, pair_fm(x,y,z), env) ⟷
pair(##A, nth(x,env), nth(y,env), nth(z,env))"

lemma pair_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y; nth(k,env) = z;
i ∈ nat; j ∈ nat; k ∈ nat; env ∈ list(A)|]
==> pair(##A, x, y, z) ⟷ sats(A, pair_fm(i,j,k), env)"
by (simp)

theorem pair_reflection:
"REFLECTS[λx. pair(L,f(x),g(x),h(x)),
λi x. pair(##Lset(i),f(x),g(x),h(x))]"
apply (simp only: pair_def)
apply (intro FOL_reflections upair_reflection)
done

subsubsection‹Binary Unions, Internalized›

definition
union_fm :: "[i,i,i]=>i" where
"union_fm(x,y,z) ==
Forall(Iff(Member(0,succ(z)),
Or(Member(0,succ(x)),Member(0,succ(y)))))"

lemma union_type [TC]:
"[| x ∈ nat; y ∈ nat; z ∈ nat |] ==> union_fm(x,y,z) ∈ formula"

lemma sats_union_fm [simp]:
"[| x ∈ nat; y ∈ nat; z ∈ nat; env ∈ list(A)|]
==> sats(A, union_fm(x,y,z), env) ⟷
union(##A, nth(x,env), nth(y,env), nth(z,env))"

lemma union_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y; nth(k,env) = z;
i ∈ nat; j ∈ nat; k ∈ nat; env ∈ list(A)|]
==> union(##A, x, y, z) ⟷ sats(A, union_fm(i,j,k), env)"
by (simp)

theorem union_reflection:
"REFLECTS[λx. union(L,f(x),g(x),h(x)),
λi x. union(##Lset(i),f(x),g(x),h(x))]"
apply (simp only: union_def)
apply (intro FOL_reflections)
done

subsubsection‹Set ``Cons,'' Internalized›

definition
cons_fm :: "[i,i,i]=>i" where
"cons_fm(x,y,z) ==
Exists(And(upair_fm(succ(x),succ(x),0),
union_fm(0,succ(y),succ(z))))"

lemma cons_type [TC]:
"[| x ∈ nat; y ∈ nat; z ∈ nat |] ==> cons_fm(x,y,z) ∈ formula"

lemma sats_cons_fm [simp]:
"[| x ∈ nat; y ∈ nat; z ∈ nat; env ∈ list(A)|]
==> sats(A, cons_fm(x,y,z), env) ⟷
is_cons(##A, nth(x,env), nth(y,env), nth(z,env))"

lemma cons_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y; nth(k,env) = z;
i ∈ nat; j ∈ nat; k ∈ nat; env ∈ list(A)|]
==> is_cons(##A, x, y, z) ⟷ sats(A, cons_fm(i,j,k), env)"
by simp

theorem cons_reflection:
"REFLECTS[λx. is_cons(L,f(x),g(x),h(x)),
λi x. is_cons(##Lset(i),f(x),g(x),h(x))]"
apply (simp only: is_cons_def)
apply (intro FOL_reflections upair_reflection union_reflection)
done

subsubsection‹Successor Function, Internalized›

definition
succ_fm :: "[i,i]=>i" where
"succ_fm(x,y) == cons_fm(x,x,y)"

lemma succ_type [TC]:
"[| x ∈ nat; y ∈ nat |] ==> succ_fm(x,y) ∈ formula"

lemma sats_succ_fm [simp]:
"[| x ∈ nat; y ∈ nat; env ∈ list(A)|]
==> sats(A, succ_fm(x,y), env) ⟷
successor(##A, nth(x,env), nth(y,env))"

lemma successor_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y;
i ∈ nat; j ∈ nat; env ∈ list(A)|]
==> successor(##A, x, y) ⟷ sats(A, succ_fm(i,j), env)"
by simp

theorem successor_reflection:
"REFLECTS[λx. successor(L,f(x),g(x)),
λi x. successor(##Lset(i),f(x),g(x))]"
apply (simp only: successor_def)
apply (intro cons_reflection)
done

subsubsection‹The Number 1, Internalized›

(* "number1(M,a) == (∃x[M]. empty(M,x) & successor(M,x,a))" *)
definition
number1_fm :: "i=>i" where
"number1_fm(a) == Exists(And(empty_fm(0), succ_fm(0,succ(a))))"

lemma number1_type [TC]:
"x ∈ nat ==> number1_fm(x) ∈ formula"

lemma sats_number1_fm [simp]:
"[| x ∈ nat; env ∈ list(A)|]
==> sats(A, number1_fm(x), env) ⟷ number1(##A, nth(x,env))"

lemma number1_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y;
i ∈ nat; env ∈ list(A)|]
==> number1(##A, x) ⟷ sats(A, number1_fm(i), env)"
by simp

theorem number1_reflection:
"REFLECTS[λx. number1(L,f(x)),
λi x. number1(##Lset(i),f(x))]"
apply (simp only: number1_def)
apply (intro FOL_reflections empty_reflection successor_reflection)
done

subsubsection‹Big Union, Internalized›

(*  "big_union(M,A,z) == ∀x[M]. x ∈ z ⟷ (∃y[M]. y∈A & x ∈ y)" *)
definition
big_union_fm :: "[i,i]=>i" where
"big_union_fm(A,z) ==
Forall(Iff(Member(0,succ(z)),
Exists(And(Member(0,succ(succ(A))), Member(1,0)))))"

lemma big_union_type [TC]:
"[| x ∈ nat; y ∈ nat |] ==> big_union_fm(x,y) ∈ formula"

lemma sats_big_union_fm [simp]:
"[| x ∈ nat; y ∈ nat; env ∈ list(A)|]
==> sats(A, big_union_fm(x,y), env) ⟷
big_union(##A, nth(x,env), nth(y,env))"

lemma big_union_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y;
i ∈ nat; j ∈ nat; env ∈ list(A)|]
==> big_union(##A, x, y) ⟷ sats(A, big_union_fm(i,j), env)"
by simp

theorem big_union_reflection:
"REFLECTS[λx. big_union(L,f(x),g(x)),
λi x. big_union(##Lset(i),f(x),g(x))]"
apply (simp only: big_union_def)
apply (intro FOL_reflections)
done

subsubsection‹Variants of Satisfaction Definitions for Ordinals, etc.›

text‹The ‹sats› theorems below are standard versions of the ones proved
in theory ‹Formula›.  They relate elements of type \<^term>‹formula› to
relativized concepts such as \<^term>‹subset› or \<^term>‹ordinal› rather than to
real concepts such as \<^term>‹Ord›.  Now that we have instantiated the locale
‹M_trivial›, we no longer require the earlier versions.›

lemma sats_subset_fm':
"[|x ∈ nat; y ∈ nat; env ∈ list(A)|]
==> sats(A, subset_fm(x,y), env) ⟷ subset(##A, nth(x,env), nth(y,env))"

theorem subset_reflection:
"REFLECTS[λx. subset(L,f(x),g(x)),
λi x. subset(##Lset(i),f(x),g(x))]"
apply (simp only: Relative.subset_def)
apply (intro FOL_reflections)
done

lemma sats_transset_fm':
"[|x ∈ nat; env ∈ list(A)|]
==> sats(A, transset_fm(x), env) ⟷ transitive_set(##A, nth(x,env))"
by (simp add: sats_subset_fm' transset_fm_def transitive_set_def)

theorem transitive_set_reflection:
"REFLECTS[λx. transitive_set(L,f(x)),
λi x. transitive_set(##Lset(i),f(x))]"
apply (simp only: transitive_set_def)
apply (intro FOL_reflections subset_reflection)
done

lemma sats_ordinal_fm':
"[|x ∈ nat; env ∈ list(A)|]
==> sats(A, ordinal_fm(x), env) ⟷ ordinal(##A,nth(x,env))"
by (simp add: sats_transset_fm' ordinal_fm_def ordinal_def)

lemma ordinal_iff_sats:
"[| nth(i,env) = x;  i ∈ nat; env ∈ list(A)|]
==> ordinal(##A, x) ⟷ sats(A, ordinal_fm(i), env)"

theorem ordinal_reflection:
"REFLECTS[λx. ordinal(L,f(x)), λi x. ordinal(##Lset(i),f(x))]"
apply (simp only: ordinal_def)
apply (intro FOL_reflections transitive_set_reflection)
done

subsubsection‹Membership Relation, Internalized›

definition
Memrel_fm :: "[i,i]=>i" where
"Memrel_fm(A,r) ==
Forall(Iff(Member(0,succ(r)),
Exists(And(Member(0,succ(succ(A))),
Exists(And(Member(0,succ(succ(succ(A)))),
And(Member(1,0),
pair_fm(1,0,2))))))))"

lemma Memrel_type [TC]:
"[| x ∈ nat; y ∈ nat |] ==> Memrel_fm(x,y) ∈ formula"

lemma sats_Memrel_fm [simp]:
"[| x ∈ nat; y ∈ nat; env ∈ list(A)|]
==> sats(A, Memrel_fm(x,y), env) ⟷
membership(##A, nth(x,env), nth(y,env))"

lemma Memrel_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y;
i ∈ nat; j ∈ nat; env ∈ list(A)|]
==> membership(##A, x, y) ⟷ sats(A, Memrel_fm(i,j), env)"
by simp

theorem membership_reflection:
"REFLECTS[λx. membership(L,f(x),g(x)),
λi x. membership(##Lset(i),f(x),g(x))]"
apply (simp only: membership_def)
apply (intro FOL_reflections pair_reflection)
done

subsubsection‹Predecessor Set, Internalized›

definition
pred_set_fm :: "[i,i,i,i]=>i" where
"pred_set_fm(A,x,r,B) ==
Forall(Iff(Member(0,succ(B)),
Exists(And(Member(0,succ(succ(r))),
And(Member(1,succ(succ(A))),
pair_fm(1,succ(succ(x)),0))))))"

lemma pred_set_type [TC]:
"[| A ∈ nat; x ∈ nat; r ∈ nat; B ∈ nat |]
==> pred_set_fm(A,x,r,B) ∈ formula"

lemma sats_pred_set_fm [simp]:
"[| U ∈ nat; x ∈ nat; r ∈ nat; B ∈ nat; env ∈ list(A)|]
==> sats(A, pred_set_fm(U,x,r,B), env) ⟷
pred_set(##A, nth(U,env), nth(x,env), nth(r,env), nth(B,env))"

lemma pred_set_iff_sats:
"[| nth(i,env) = U; nth(j,env) = x; nth(k,env) = r; nth(l,env) = B;
i ∈ nat; j ∈ nat; k ∈ nat; l ∈ nat; env ∈ list(A)|]
==> pred_set(##A,U,x,r,B) ⟷ sats(A, pred_set_fm(i,j,k,l), env)"
by (simp)

theorem pred_set_reflection:
"REFLECTS[λx. pred_set(L,f(x),g(x),h(x),b(x)),
λi x. pred_set(##Lset(i),f(x),g(x),h(x),b(x))]"
apply (simp only: pred_set_def)
apply (intro FOL_reflections pair_reflection)
done

subsubsection‹Domain of a Relation, Internalized›

(* "is_domain(M,r,z) ==
∀x[M]. (x ∈ z ⟷ (∃w[M]. w∈r & (∃y[M]. pair(M,x,y,w))))" *)
definition
domain_fm :: "[i,i]=>i" where
"domain_fm(r,z) ==
Forall(Iff(Member(0,succ(z)),
Exists(And(Member(0,succ(succ(r))),
Exists(pair_fm(2,0,1))))))"

lemma domain_type [TC]:
"[| x ∈ nat; y ∈ nat |] ==> domain_fm(x,y) ∈ formula"

lemma sats_domain_fm [simp]:
"[| x ∈ nat; y ∈ nat; env ∈ list(A)|]
==> sats(A, domain_fm(x,y), env) ⟷
is_domain(##A, nth(x,env), nth(y,env))"

lemma domain_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y;
i ∈ nat; j ∈ nat; env ∈ list(A)|]
==> is_domain(##A, x, y) ⟷ sats(A, domain_fm(i,j), env)"
by simp

theorem domain_reflection:
"REFLECTS[λx. is_domain(L,f(x),g(x)),
λi x. is_domain(##Lset(i),f(x),g(x))]"
apply (simp only: is_domain_def)
apply (intro FOL_reflections pair_reflection)
done

subsubsection‹Range of a Relation, Internalized›

(* "is_range(M,r,z) ==
∀y[M]. (y ∈ z ⟷ (∃w[M]. w∈r & (∃x[M]. pair(M,x,y,w))))" *)
definition
range_fm :: "[i,i]=>i" where
"range_fm(r,z) ==
Forall(Iff(Member(0,succ(z)),
Exists(And(Member(0,succ(succ(r))),
Exists(pair_fm(0,2,1))))))"

lemma range_type [TC]:
"[| x ∈ nat; y ∈ nat |] ==> range_fm(x,y) ∈ formula"

lemma sats_range_fm [simp]:
"[| x ∈ nat; y ∈ nat; env ∈ list(A)|]
==> sats(A, range_fm(x,y), env) ⟷
is_range(##A, nth(x,env), nth(y,env))"

lemma range_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y;
i ∈ nat; j ∈ nat; env ∈ list(A)|]
==> is_range(##A, x, y) ⟷ sats(A, range_fm(i,j), env)"
by simp

theorem range_reflection:
"REFLECTS[λx. is_range(L,f(x),g(x)),
λi x. is_range(##Lset(i),f(x),g(x))]"
apply (simp only: is_range_def)
apply (intro FOL_reflections pair_reflection)
done

subsubsection‹Field of a Relation, Internalized›

(* "is_field(M,r,z) ==
∃dr[M]. is_domain(M,r,dr) &
(∃rr[M]. is_range(M,r,rr) & union(M,dr,rr,z))" *)
definition
field_fm :: "[i,i]=>i" where
"field_fm(r,z) ==
Exists(And(domain_fm(succ(r),0),
Exists(And(range_fm(succ(succ(r)),0),
union_fm(1,0,succ(succ(z)))))))"

lemma field_type [TC]:
"[| x ∈ nat; y ∈ nat |] ==> field_fm(x,y) ∈ formula"

lemma sats_field_fm [simp]:
"[| x ∈ nat; y ∈ nat; env ∈ list(A)|]
==> sats(A, field_fm(x,y), env) ⟷
is_field(##A, nth(x,env), nth(y,env))"

lemma field_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y;
i ∈ nat; j ∈ nat; env ∈ list(A)|]
==> is_field(##A, x, y) ⟷ sats(A, field_fm(i,j), env)"
by simp

theorem field_reflection:
"REFLECTS[λx. is_field(L,f(x),g(x)),
λi x. is_field(##Lset(i),f(x),g(x))]"
apply (simp only: is_field_def)
apply (intro FOL_reflections domain_reflection range_reflection
union_reflection)
done

subsubsection‹Image under a Relation, Internalized›

(* "image(M,r,A,z) ==
∀y[M]. (y ∈ z ⟷ (∃w[M]. w∈r & (∃x[M]. x∈A & pair(M,x,y,w))))" *)
definition
image_fm :: "[i,i,i]=>i" where
"image_fm(r,A,z) ==
Forall(Iff(Member(0,succ(z)),
Exists(And(Member(0,succ(succ(r))),
Exists(And(Member(0,succ(succ(succ(A)))),
pair_fm(0,2,1)))))))"

lemma image_type [TC]:
"[| x ∈ nat; y ∈ nat; z ∈ nat |] ==> image_fm(x,y,z) ∈ formula"

lemma sats_image_fm [simp]:
"[| x ∈ nat; y ∈ nat; z ∈ nat; env ∈ list(A)|]
==> sats(A, image_fm(x,y,z), env) ⟷
image(##A, nth(x,env), nth(y,env), nth(z,env))"

lemma image_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y; nth(k,env) = z;
i ∈ nat; j ∈ nat; k ∈ nat; env ∈ list(A)|]
==> image(##A, x, y, z) ⟷ sats(A, image_fm(i,j,k), env)"
by (simp)

theorem image_reflection:
"REFLECTS[λx. image(L,f(x),g(x),h(x)),
λi x. image(##Lset(i),f(x),g(x),h(x))]"
apply (simp only: Relative.image_def)
apply (intro FOL_reflections pair_reflection)
done

subsubsection‹Pre-Image under a Relation, Internalized›

(* "pre_image(M,r,A,z) ==
∀x[M]. x ∈ z ⟷ (∃w[M]. w∈r & (∃y[M]. y∈A & pair(M,x,y,w)))" *)
definition
pre_image_fm :: "[i,i,i]=>i" where
"pre_image_fm(r,A,z) ==
Forall(Iff(Member(0,succ(z)),
Exists(And(Member(0,succ(succ(r))),
Exists(And(Member(0,succ(succ(succ(A)))),
pair_fm(2,0,1)))))))"

lemma pre_image_type [TC]:
"[| x ∈ nat; y ∈ nat; z ∈ nat |] ==> pre_image_fm(x,y,z) ∈ formula"

lemma sats_pre_image_fm [simp]:
"[| x ∈ nat; y ∈ nat; z ∈ nat; env ∈ list(A)|]
==> sats(A, pre_image_fm(x,y,z), env) ⟷
pre_image(##A, nth(x,env), nth(y,env), nth(z,env))"

lemma pre_image_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y; nth(k,env) = z;
i ∈ nat; j ∈ nat; k ∈ nat; env ∈ list(A)|]
==> pre_image(##A, x, y, z) ⟷ sats(A, pre_image_fm(i,j,k), env)"
by (simp)

theorem pre_image_reflection:
"REFLECTS[λx. pre_image(L,f(x),g(x),h(x)),
λi x. pre_image(##Lset(i),f(x),g(x),h(x))]"
apply (simp only: Relative.pre_image_def)
apply (intro FOL_reflections pair_reflection)
done

subsubsection‹Function Application, Internalized›

(* "fun_apply(M,f,x,y) ==
(∃xs[M]. ∃fxs[M].
upair(M,x,x,xs) & image(M,f,xs,fxs) & big_union(M,fxs,y))" *)
definition
fun_apply_fm :: "[i,i,i]=>i" where
"fun_apply_fm(f,x,y) ==
Exists(Exists(And(upair_fm(succ(succ(x)), succ(succ(x)), 1),
And(image_fm(succ(succ(f)), 1, 0),
big_union_fm(0,succ(succ(y)))))))"

lemma fun_apply_type [TC]:
"[| x ∈ nat; y ∈ nat; z ∈ nat |] ==> fun_apply_fm(x,y,z) ∈ formula"

lemma sats_fun_apply_fm [simp]:
"[| x ∈ nat; y ∈ nat; z ∈ nat; env ∈ list(A)|]
==> sats(A, fun_apply_fm(x,y,z), env) ⟷
fun_apply(##A, nth(x,env), nth(y,env), nth(z,env))"

lemma fun_apply_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y; nth(k,env) = z;
i ∈ nat; j ∈ nat; k ∈ nat; env ∈ list(A)|]
==> fun_apply(##A, x, y, z) ⟷ sats(A, fun_apply_fm(i,j,k), env)"
by simp

theorem fun_apply_reflection:
"REFLECTS[λx. fun_apply(L,f(x),g(x),h(x)),
λi x. fun_apply(##Lset(i),f(x),g(x),h(x))]"
apply (simp only: fun_apply_def)
apply (intro FOL_reflections upair_reflection image_reflection
big_union_reflection)
done

subsubsection‹The Concept of Relation, Internalized›

(* "is_relation(M,r) ==
(∀z[M]. z∈r ⟶ (∃x[M]. ∃y[M]. pair(M,x,y,z)))" *)
definition
relation_fm :: "i=>i" where
"relation_fm(r) ==
Forall(Implies(Member(0,succ(r)), Exists(Exists(pair_fm(1,0,2)))))"

lemma relation_type [TC]:
"[| x ∈ nat |] ==> relation_fm(x) ∈ formula"

lemma sats_relation_fm [simp]:
"[| x ∈ nat; env ∈ list(A)|]
==> sats(A, relation_fm(x), env) ⟷ is_relation(##A, nth(x,env))"

lemma relation_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y;
i ∈ nat; env ∈ list(A)|]
==> is_relation(##A, x) ⟷ sats(A, relation_fm(i), env)"
by simp

theorem is_relation_reflection:
"REFLECTS[λx. is_relation(L,f(x)),
λi x. is_relation(##Lset(i),f(x))]"
apply (simp only: is_relation_def)
apply (intro FOL_reflections pair_reflection)
done

subsubsection‹The Concept of Function, Internalized›

(* "is_function(M,r) ==
∀x[M]. ∀y[M]. ∀y'[M]. ∀p[M]. ∀p'[M].
pair(M,x,y,p) ⟶ pair(M,x,y',p') ⟶ p∈r ⟶ p'∈r ⟶ y=y'" *)
definition
function_fm :: "i=>i" where
"function_fm(r) ==
Forall(Forall(Forall(Forall(Forall(
Implies(pair_fm(4,3,1),
Implies(pair_fm(4,2,0),
Implies(Member(1,r#+5),
Implies(Member(0,r#+5), Equal(3,2))))))))))"

lemma function_type [TC]:
"[| x ∈ nat |] ==> function_fm(x) ∈ formula"

lemma sats_function_fm [simp]:
"[| x ∈ nat; env ∈ list(A)|]
==> sats(A, function_fm(x), env) ⟷ is_function(##A, nth(x,env))"

lemma is_function_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y;
i ∈ nat; env ∈ list(A)|]
==> is_function(##A, x) ⟷ sats(A, function_fm(i), env)"
by simp

theorem is_function_reflection:
"REFLECTS[λx. is_function(L,f(x)),
λi x. is_function(##Lset(i),f(x))]"
apply (simp only: is_function_def)
apply (intro FOL_reflections pair_reflection)
done

subsubsection‹Typed Functions, Internalized›

(* "typed_function(M,A,B,r) ==
is_function(M,r) & is_relation(M,r) & is_domain(M,r,A) &
(∀u[M]. u∈r ⟶ (∀x[M]. ∀y[M]. pair(M,x,y,u) ⟶ y∈B))" *)

definition
typed_function_fm :: "[i,i,i]=>i" where
"typed_function_fm(A,B,r) ==
And(function_fm(r),
And(relation_fm(r),
And(domain_fm(r,A),
Forall(Implies(Member(0,succ(r)),
Forall(Forall(Implies(pair_fm(1,0,2),Member(0,B#+3)))))))))"

lemma typed_function_type [TC]:
"[| x ∈ nat; y ∈ nat; z ∈ nat |] ==> typed_function_fm(x,y,z) ∈ formula"

lemma sats_typed_function_fm [simp]:
"[| x ∈ nat; y ∈ nat; z ∈ nat; env ∈ list(A)|]
==> sats(A, typed_function_fm(x,y,z), env) ⟷
typed_function(##A, nth(x,env), nth(y,env), nth(z,env))"

lemma typed_function_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y; nth(k,env) = z;
i ∈ nat; j ∈ nat; k ∈ nat; env ∈ list(A)|]
==> typed_function(##A, x, y, z) ⟷ sats(A, typed_function_fm(i,j,k), env)"
by simp

lemmas function_reflections =
empty_reflection number1_reflection
upair_reflection pair_reflection union_reflection
big_union_reflection cons_reflection successor_reflection
fun_apply_reflection subset_reflection
transitive_set_reflection membership_reflection
pred_set_reflection domain_reflection range_reflection field_reflection
image_reflection pre_image_reflection
is_relation_reflection is_function_reflection

lemmas function_iff_sats =
empty_iff_sats number1_iff_sats
upair_iff_sats pair_iff_sats union_iff_sats
big_union_iff_sats cons_iff_sats successor_iff_sats
fun_apply_iff_sats  Memrel_iff_sats
pred_set_iff_sats domain_iff_sats range_iff_sats field_iff_sats
image_iff_sats pre_image_iff_sats
relation_iff_sats is_function_iff_sats

theorem typed_function_reflection:
"REFLECTS[λx. typed_function(L,f(x),g(x),h(x)),
λi x. typed_function(##Lset(i),f(x),g(x),h(x))]"
apply (simp only: typed_function_def)
apply (intro FOL_reflections function_reflections)
done

subsubsection‹Composition of Relations, Internalized›

(* "composition(M,r,s,t) ==
∀p[M]. p ∈ t ⟷
(∃x[M]. ∃y[M]. ∃z[M]. ∃xy[M]. ∃yz[M].
pair(M,x,z,p) & pair(M,x,y,xy) & pair(M,y,z,yz) &
xy ∈ s & yz ∈ r)" *)
definition
composition_fm :: "[i,i,i]=>i" where
"composition_fm(r,s,t) ==
Forall(Iff(Member(0,succ(t)),
Exists(Exists(Exists(Exists(Exists(
And(pair_fm(4,2,5),
And(pair_fm(4,3,1),
And(pair_fm(3,2,0),
And(Member(1,s#+6), Member(0,r#+6))))))))))))"

lemma composition_type [TC]:
"[| x ∈ nat; y ∈ nat; z ∈ nat |] ==> composition_fm(x,y,z) ∈ formula"

lemma sats_composition_fm [simp]:
"[| x ∈ nat; y ∈ nat; z ∈ nat; env ∈ list(A)|]
==> sats(A, composition_fm(x,y,z), env) ⟷
composition(##A, nth(x,env), nth(y,env), nth(z,env))"

lemma composition_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y; nth(k,env) = z;
i ∈ nat; j ∈ nat; k ∈ nat; env ∈ list(A)|]
==> composition(##A, x, y, z) ⟷ sats(A, composition_fm(i,j,k), env)"
by simp

theorem composition_reflection:
"REFLECTS[λx. composition(L,f(x),g(x),h(x)),
λi x. composition(##Lset(i),f(x),g(x),h(x))]"
apply (simp only: composition_def)
apply (intro FOL_reflections pair_reflection)
done

subsubsection‹Injections, Internalized›

(* "injection(M,A,B,f) ==
typed_function(M,A,B,f) &
(∀x[M]. ∀x'[M]. ∀y[M]. ∀p[M]. ∀p'[M].
pair(M,x,y,p) ⟶ pair(M,x',y,p') ⟶ p∈f ⟶ p'∈f ⟶ x=x')" *)
definition
injection_fm :: "[i,i,i]=>i" where
"injection_fm(A,B,f) ==
And(typed_function_fm(A,B,f),
Forall(Forall(Forall(Forall(Forall(
Implies(pair_fm(4,2,1),
Implies(pair_fm(3,2,0),
Implies(Member(1,f#+5),
Implies(Member(0,f#+5), Equal(4,3)))))))))))"

lemma injection_type [TC]:
"[| x ∈ nat; y ∈ nat; z ∈ nat |] ==> injection_fm(x,y,z) ∈ formula"

lemma sats_injection_fm [simp]:
"[| x ∈ nat; y ∈ nat; z ∈ nat; env ∈ list(A)|]
==> sats(A, injection_fm(x,y,z), env) ⟷
injection(##A, nth(x,env), nth(y,env), nth(z,env))"

lemma injection_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y; nth(k,env) = z;
i ∈ nat; j ∈ nat; k ∈ nat; env ∈ list(A)|]
==> injection(##A, x, y, z) ⟷ sats(A, injection_fm(i,j,k), env)"
by simp

theorem injection_reflection:
"REFLECTS[λx. injection(L,f(x),g(x),h(x)),
λi x. injection(##Lset(i),f(x),g(x),h(x))]"
apply (simp only: injection_def)
apply (intro FOL_reflections function_reflections typed_function_reflection)
done

subsubsection‹Surjections, Internalized›

(*  surjection :: "[i=>o,i,i,i] => o"
"surjection(M,A,B,f) ==
typed_function(M,A,B,f) &
(∀y[M]. y∈B ⟶ (∃x[M]. x∈A & fun_apply(M,f,x,y)))" *)
definition
surjection_fm :: "[i,i,i]=>i" where
"surjection_fm(A,B,f) ==
And(typed_function_fm(A,B,f),
Forall(Implies(Member(0,succ(B)),
Exists(And(Member(0,succ(succ(A))),
fun_apply_fm(succ(succ(f)),0,1))))))"

lemma surjection_type [TC]:
"[| x ∈ nat; y ∈ nat; z ∈ nat |] ==> surjection_fm(x,y,z) ∈ formula"

lemma sats_surjection_fm [simp]:
"[| x ∈ nat; y ∈ nat; z ∈ nat; env ∈ list(A)|]
==> sats(A, surjection_fm(x,y,z), env) ⟷
surjection(##A, nth(x,env), nth(y,env), nth(z,env))"

lemma surjection_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y; nth(k,env) = z;
i ∈ nat; j ∈ nat; k ∈ nat; env ∈ list(A)|]
==> surjection(##A, x, y, z) ⟷ sats(A, surjection_fm(i,j,k), env)"
by simp

theorem surjection_reflection:
"REFLECTS[λx. surjection(L,f(x),g(x),h(x)),
λi x. surjection(##Lset(i),f(x),g(x),h(x))]"
apply (simp only: surjection_def)
apply (intro FOL_reflections function_reflections typed_function_reflection)
done

subsubsection‹Bijections, Internalized›

(*   bijection :: "[i=>o,i,i,i] => o"
"bijection(M,A,B,f) == injection(M,A,B,f) & surjection(M,A,B,f)" *)
definition
bijection_fm :: "[i,i,i]=>i" where
"bijection_fm(A,B,f) == And(injection_fm(A,B,f), surjection_fm(A,B,f))"

lemma bijection_type [TC]:
"[| x ∈ nat; y ∈ nat; z ∈ nat |] ==> bijection_fm(x,y,z) ∈ formula"

lemma sats_bijection_fm [simp]:
"[| x ∈ nat; y ∈ nat; z ∈ nat; env ∈ list(A)|]
==> sats(A, bijection_fm(x,y,z), env) ⟷
bijection(##A, nth(x,env), nth(y,env), nth(z,env))"

lemma bijection_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y; nth(k,env) = z;
i ∈ nat; j ∈ nat; k ∈ nat; env ∈ list(A)|]
==> bijection(##A, x, y, z) ⟷ sats(A, bijection_fm(i,j,k), env)"
by simp

theorem bijection_reflection:
"REFLECTS[λx. bijection(L,f(x),g(x),h(x)),
λi x. bijection(##Lset(i),f(x),g(x),h(x))]"
apply (simp only: bijection_def)
apply (intro And_reflection injection_reflection surjection_reflection)
done

subsubsection‹Restriction of a Relation, Internalized›

(* "restriction(M,r,A,z) ==
∀x[M]. x ∈ z ⟷ (x ∈ r & (∃u[M]. u∈A & (∃v[M]. pair(M,u,v,x))))" *)
definition
restriction_fm :: "[i,i,i]=>i" where
"restriction_fm(r,A,z) ==
Forall(Iff(Member(0,succ(z)),
And(Member(0,succ(r)),
Exists(And(Member(0,succ(succ(A))),
Exists(pair_fm(1,0,2)))))))"

lemma restriction_type [TC]:
"[| x ∈ nat; y ∈ nat; z ∈ nat |] ==> restriction_fm(x,y,z) ∈ formula"

lemma sats_restriction_fm [simp]:
"[| x ∈ nat; y ∈ nat; z ∈ nat; env ∈ list(A)|]
==> sats(A, restriction_fm(x,y,z), env) ⟷
restriction(##A, nth(x,env), nth(y,env), nth(z,env))"

lemma restriction_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y; nth(k,env) = z;
i ∈ nat; j ∈ nat; k ∈ nat; env ∈ list(A)|]
==> restriction(##A, x, y, z) ⟷ sats(A, restriction_fm(i,j,k), env)"
by simp

theorem restriction_reflection:
"REFLECTS[λx. restriction(L,f(x),g(x),h(x)),
λi x. restriction(##Lset(i),f(x),g(x),h(x))]"
apply (simp only: restriction_def)
apply (intro FOL_reflections pair_reflection)
done

subsubsection‹Order-Isomorphisms, Internalized›

(*  order_isomorphism :: "[i=>o,i,i,i,i,i] => o"
"order_isomorphism(M,A,r,B,s,f) ==
bijection(M,A,B,f) &
(∀x[M]. x∈A ⟶ (∀y[M]. y∈A ⟶
(∀p[M]. ∀fx[M]. ∀fy[M]. ∀q[M].
pair(M,x,y,p) ⟶ fun_apply(M,f,x,fx) ⟶ fun_apply(M,f,y,fy) ⟶
pair(M,fx,fy,q) ⟶ (p∈r ⟷ q∈s))))"
*)

definition
order_isomorphism_fm :: "[i,i,i,i,i]=>i" where
"order_isomorphism_fm(A,r,B,s,f) ==
And(bijection_fm(A,B,f),
Forall(Implies(Member(0,succ(A)),
Forall(Implies(Member(0,succ(succ(A))),
Forall(Forall(Forall(Forall(
Implies(pair_fm(5,4,3),
Implies(fun_apply_fm(f#+6,5,2),
Implies(fun_apply_fm(f#+6,4,1),
Implies(pair_fm(2,1,0),
Iff(Member(3,r#+6), Member(0,s#+6)))))))))))))))"

lemma order_isomorphism_type [TC]:
"[| A ∈ nat; r ∈ nat; B ∈ nat; s ∈ nat; f ∈ nat |]
==> order_isomorphism_fm(A,r,B,s,f) ∈ formula"

lemma sats_order_isomorphism_fm [simp]:
"[| U ∈ nat; r ∈ nat; B ∈ nat; s ∈ nat; f ∈ nat; env ∈ list(A)|]
==> sats(A, order_isomorphism_fm(U,r,B,s,f), env) ⟷
order_isomorphism(##A, nth(U,env), nth(r,env), nth(B,env),
nth(s,env), nth(f,env))"

lemma order_isomorphism_iff_sats:
"[| nth(i,env) = U; nth(j,env) = r; nth(k,env) = B; nth(j',env) = s;
nth(k',env) = f;
i ∈ nat; j ∈ nat; k ∈ nat; j' ∈ nat; k' ∈ nat; env ∈ list(A)|]
==> order_isomorphism(##A,U,r,B,s,f) ⟷
sats(A, order_isomorphism_fm(i,j,k,j',k'), env)"
by simp

theorem order_isomorphism_reflection:
"REFLECTS[λx. order_isomorphism(L,f(x),g(x),h(x),g'(x),h'(x)),
λi x. order_isomorphism(##Lset(i),f(x),g(x),h(x),g'(x),h'(x))]"
apply (simp only: order_isomorphism_def)
apply (intro FOL_reflections function_reflections bijection_reflection)
done

subsubsection‹Limit Ordinals, Internalized›

text‹A limit ordinal is a non-empty, successor-closed ordinal›

(* "limit_ordinal(M,a) ==
ordinal(M,a) & ~ empty(M,a) &
(∀x[M]. x∈a ⟶ (∃y[M]. y∈a & successor(M,x,y)))" *)

definition
limit_ordinal_fm :: "i=>i" where
"limit_ordinal_fm(x) ==
And(ordinal_fm(x),
And(Neg(empty_fm(x)),
Forall(Implies(Member(0,succ(x)),
Exists(And(Member(0,succ(succ(x))),
succ_fm(1,0)))))))"

lemma limit_ordinal_type [TC]:
"x ∈ nat ==> limit_ordinal_fm(x) ∈ formula"

lemma sats_limit_ordinal_fm [simp]:
"[| x ∈ nat; env ∈ list(A)|]
==> sats(A, limit_ordinal_fm(x), env) ⟷ limit_ordinal(##A, nth(x,env))"
by (simp add: limit_ordinal_fm_def limit_ordinal_def sats_ordinal_fm')

lemma limit_ordinal_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y;
i ∈ nat; env ∈ list(A)|]
==> limit_ordinal(##A, x) ⟷ sats(A, limit_ordinal_fm(i), env)"
by simp

theorem limit_ordinal_reflection:
"REFLECTS[λx. limit_ordinal(L,f(x)),
λi x. limit_ordinal(##Lset(i),f(x))]"
apply (simp only: limit_ordinal_def)
apply (intro FOL_reflections ordinal_reflection
empty_reflection successor_reflection)
done

subsubsection‹Finite Ordinals: The Predicate ``Is A Natural Number''›

(*     "finite_ordinal(M,a) ==
ordinal(M,a) & ~ limit_ordinal(M,a) &
(∀x[M]. x∈a ⟶ ~ limit_ordinal(M,x))" *)
definition
finite_ordinal_fm :: "i=>i" where
"finite_ordinal_fm(x) ==
And(ordinal_fm(x),
And(Neg(limit_ordinal_fm(x)),
Forall(Implies(Member(0,succ(x)),
Neg(limit_ordinal_fm(0))))))"

lemma finite_ordinal_type [TC]:
"x ∈ nat ==> finite_ordinal_fm(x) ∈ formula"

lemma sats_finite_ordinal_fm [simp]:
"[| x ∈ nat; env ∈ list(A)|]
==> sats(A, finite_ordinal_fm(x), env) ⟷ finite_ordinal(##A, nth(x,env))"
by (simp add: finite_ordinal_fm_def sats_ordinal_fm' finite_ordinal_def)

lemma finite_ordinal_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y;
i ∈ nat; env ∈ list(A)|]
==> finite_ordinal(##A, x) ⟷ sats(A, finite_ordinal_fm(i), env)"
by simp

theorem finite_ordinal_reflection:
"REFLECTS[λx. finite_ordinal(L,f(x)),
λi x. finite_ordinal(##Lset(i),f(x))]"
apply (simp only: finite_ordinal_def)
apply (intro FOL_reflections ordinal_reflection limit_ordinal_reflection)
done

subsubsection‹Omega: The Set of Natural Numbers›

(* omega(M,a) == limit_ordinal(M,a) & (∀x[M]. x∈a ⟶ ~ limit_ordinal(M,x)) *)
definition
omega_fm :: "i=>i" where
"omega_fm(x) ==
And(limit_ordinal_fm(x),
Forall(Implies(Member(0,succ(x)),
Neg(limit_ordinal_fm(0)))))"

lemma omega_type [TC]:
"x ∈ nat ==> omega_fm(x) ∈ formula"

lemma sats_omega_fm [simp]:
"[| x ∈ nat; env ∈ list(A)|]
==> sats(A, omega_fm(x), env) ⟷ omega(##A, nth(x,env))"

lemma omega_iff_sats:
"[| nth(i,env) = x; nth(j,env) = y;
i ∈ nat; env ∈ list(A)|]
==> omega(##A, x) ⟷ sats(A, omega_fm(i), env)"
by simp

theorem omega_reflection:
"REFLECTS[λx. omega(L,f(x)),
λi x. omega(##Lset(i),f(x))]"
apply (simp only: omega_def)
apply (intro FOL_reflections limit_ordinal_reflection)
done

lemmas fun_plus_reflections =
typed_function_reflection composition_reflection
injection_reflection surjection_reflection
bijection_reflection restriction_reflection
order_isomorphism_reflection finite_ordinal_reflection
ordinal_reflection limit_ordinal_reflection omega_reflection

lemmas fun_plus_iff_sats =
typed_function_iff_sats composition_iff_sats
injection_iff_sats surjection_iff_sats
bijection_iff_sats restriction_iff_sats
order_isomorphism_iff_sats finite_ordinal_iff_sats
ordinal_iff_sats limit_ordinal_iff_sats omega_iff_sats

end
```