Theory StarDef

Up to index of Isabelle/HOL/HOL-Complex

theory StarDef
imports Filter
uses (transfer.ML)
begin

(*  Title       : HOL/Hyperreal/StarDef.thy
    ID          : $Id: StarDef.thy,v 1.9 2006/12/19 18:34:35 huffman Exp $
    Author      : Jacques D. Fleuriot and Brian Huffman
*)

header {* Construction of Star Types Using Ultrafilters *}

theory StarDef
imports Filter
uses ("transfer.ML")
begin

subsection {* A Free Ultrafilter over the Naturals *}

definition
  FreeUltrafilterNat :: "nat set set"  ("\<U>") where
  "\<U> = (SOME U. freeultrafilter U)"

lemma freeultrafilter_FreeUltrafilterNat: "freeultrafilter \<U>"
apply (unfold FreeUltrafilterNat_def)
apply (rule someI_ex)
apply (rule freeultrafilter_Ex)
apply (rule nat_infinite)
done

interpretation FreeUltrafilterNat: freeultrafilter [FreeUltrafilterNat]
by (rule freeultrafilter_FreeUltrafilterNat)

text {* This rule takes the place of the old ultra tactic *}

lemma ultra:
  "[|{n. P n} ∈ \<U>; {n. P n --> Q n} ∈ \<U>|] ==> {n. Q n} ∈ \<U>"
by (simp add: Collect_imp_eq
    FreeUltrafilterNat.Un_iff FreeUltrafilterNat.Compl_iff)


subsection {* Definition of @{text star} type constructor *}

definition
  starrel :: "((nat => 'a) × (nat => 'a)) set" where
  "starrel = {(X,Y). {n. X n = Y n} ∈ \<U>}"

typedef 'a star = "(UNIV :: (nat => 'a) set) // starrel"
by (auto intro: quotientI)

definition
  star_n :: "(nat => 'a) => 'a star" where
  "star_n X = Abs_star (starrel `` {X})"

theorem star_cases [case_names star_n, cases type: star]:
  "(!!X. x = star_n X ==> P) ==> P"
by (cases x, unfold star_n_def star_def, erule quotientE, fast)

lemma all_star_eq: "(∀x. P x) = (∀X. P (star_n X))"
by (auto, rule_tac x=x in star_cases, simp)

lemma ex_star_eq: "(∃x. P x) = (∃X. P (star_n X))"
by (auto, rule_tac x=x in star_cases, auto)

text {* Proving that @{term starrel} is an equivalence relation *}

lemma starrel_iff [iff]: "((X,Y) ∈ starrel) = ({n. X n = Y n} ∈ \<U>)"
by (simp add: starrel_def)

lemma equiv_starrel: "equiv UNIV starrel"
proof (rule equiv.intro)
  show "reflexive starrel" by (simp add: refl_def)
  show "sym starrel" by (simp add: sym_def eq_commute)
  show "trans starrel" by (auto intro: transI elim!: ultra)
qed

lemmas equiv_starrel_iff =
  eq_equiv_class_iff [OF equiv_starrel UNIV_I UNIV_I]

lemma starrel_in_star: "starrel``{x} ∈ star"
by (simp add: star_def quotientI)

lemma star_n_eq_iff: "(star_n X = star_n Y) = ({n. X n = Y n} ∈ \<U>)"
by (simp add: star_n_def Abs_star_inject starrel_in_star equiv_starrel_iff)


subsection {* Transfer principle *}

text {* This introduction rule starts each transfer proof. *}
lemma transfer_start:
  "P ≡ {n. Q} ∈ \<U> ==> Trueprop P ≡ Trueprop Q"
by (subgoal_tac "P ≡ Q", simp, simp add: atomize_eq)

text {*Initialize transfer tactic.*}
use "transfer.ML"
setup Transfer.setup

text {* Transfer introduction rules. *}

lemma transfer_ex [transfer_intro]:
  "[|!!X. p (star_n X) ≡ {n. P n (X n)} ∈ \<U>|]
    ==> ∃x::'a star. p x ≡ {n. ∃x. P n x} ∈ \<U>"
by (simp only: ex_star_eq FreeUltrafilterNat.Collect_ex)

lemma transfer_all [transfer_intro]:
  "[|!!X. p (star_n X) ≡ {n. P n (X n)} ∈ \<U>|]
    ==> ∀x::'a star. p x ≡ {n. ∀x. P n x} ∈ \<U>"
by (simp only: all_star_eq FreeUltrafilterNat.Collect_all)

lemma transfer_not [transfer_intro]:
  "[|p ≡ {n. P n} ∈ \<U>|] ==> ¬ p ≡ {n. ¬ P n} ∈ \<U>"
by (simp only: FreeUltrafilterNat.Collect_not)

lemma transfer_conj [transfer_intro]:
  "[|p ≡ {n. P n} ∈ \<U>; q ≡ {n. Q n} ∈ \<U>|]
    ==> p ∧ q ≡ {n. P n ∧ Q n} ∈ \<U>"
by (simp only: FreeUltrafilterNat.Collect_conj)

lemma transfer_disj [transfer_intro]:
  "[|p ≡ {n. P n} ∈ \<U>; q ≡ {n. Q n} ∈ \<U>|]
    ==> p ∨ q ≡ {n. P n ∨ Q n} ∈ \<U>"
by (simp only: FreeUltrafilterNat.Collect_disj)

lemma transfer_imp [transfer_intro]:
  "[|p ≡ {n. P n} ∈ \<U>; q ≡ {n. Q n} ∈ \<U>|]
    ==> p --> q ≡ {n. P n --> Q n} ∈ \<U>"
by (simp only: imp_conv_disj transfer_disj transfer_not)

lemma transfer_iff [transfer_intro]:
  "[|p ≡ {n. P n} ∈ \<U>; q ≡ {n. Q n} ∈ \<U>|]
    ==> p = q ≡ {n. P n = Q n} ∈ \<U>"
by (simp only: iff_conv_conj_imp transfer_conj transfer_imp)

lemma transfer_if_bool [transfer_intro]:
  "[|p ≡ {n. P n} ∈ \<U>; x ≡ {n. X n} ∈ \<U>; y ≡ {n. Y n} ∈ \<U>|]
    ==> (if p then x else y) ≡ {n. if P n then X n else Y n} ∈ \<U>"
by (simp only: if_bool_eq_conj transfer_conj transfer_imp transfer_not)

lemma transfer_eq [transfer_intro]:
  "[|x ≡ star_n X; y ≡ star_n Y|] ==> x = y ≡ {n. X n = Y n} ∈ \<U>"
by (simp only: star_n_eq_iff)

lemma transfer_if [transfer_intro]:
  "[|p ≡ {n. P n} ∈ \<U>; x ≡ star_n X; y ≡ star_n Y|]
    ==> (if p then x else y) ≡ star_n (λn. if P n then X n else Y n)"
apply (rule eq_reflection)
apply (auto simp add: star_n_eq_iff transfer_not elim!: ultra)
done

lemma transfer_fun_eq [transfer_intro]:
  "[|!!X. f (star_n X) = g (star_n X) 
    ≡ {n. F n (X n) = G n (X n)} ∈ \<U>|]
      ==> f = g ≡ {n. F n = G n} ∈ \<U>"
by (simp only: expand_fun_eq transfer_all)

lemma transfer_star_n [transfer_intro]: "star_n X ≡ star_n (λn. X n)"
by (rule reflexive)

lemma transfer_bool [transfer_intro]: "p ≡ {n. p} ∈ \<U>"
by (simp add: atomize_eq)


subsection {* Standard elements *}

definition
  star_of :: "'a => 'a star" where
  "star_of x == star_n (λn. x)"

definition
  Standard :: "'a star set" where
  "Standard = range star_of"

text {* Transfer tactic should remove occurrences of @{term star_of} *}
setup {* Transfer.add_const "StarDef.star_of" *}

declare star_of_def [transfer_intro]

lemma star_of_inject: "(star_of x = star_of y) = (x = y)"
by (transfer, rule refl)

lemma Standard_star_of [simp]: "star_of x ∈ Standard"
by (simp add: Standard_def)


subsection {* Internal functions *}

definition
  Ifun :: "('a => 'b) star => 'a star => 'b star" ("_ ∗ _" [300,301] 300) where
  "Ifun f ≡ λx. Abs_star
       (\<Union>F∈Rep_star f. \<Union>X∈Rep_star x. starrel``{λn. F n (X n)})"

lemma Ifun_congruent2:
  "congruent2 starrel starrel (λF X. starrel``{λn. F n (X n)})"
by (auto simp add: congruent2_def equiv_starrel_iff elim!: ultra)

lemma Ifun_star_n: "star_n F ∗ star_n X = star_n (λn. F n (X n))"
by (simp add: Ifun_def star_n_def Abs_star_inverse starrel_in_star
    UN_equiv_class2 [OF equiv_starrel equiv_starrel Ifun_congruent2])

text {* Transfer tactic should remove occurrences of @{term Ifun} *}
setup {* Transfer.add_const "StarDef.Ifun" *}

lemma transfer_Ifun [transfer_intro]:
  "[|f ≡ star_n F; x ≡ star_n X|] ==> f ∗ x ≡ star_n (λn. F n (X n))"
by (simp only: Ifun_star_n)

lemma Ifun_star_of [simp]: "star_of f ∗ star_of x = star_of (f x)"
by (transfer, rule refl)

lemma Standard_Ifun [simp]:
  "[|f ∈ Standard; x ∈ Standard|] ==> f ∗ x ∈ Standard"
by (auto simp add: Standard_def)

text {* Nonstandard extensions of functions *}

definition
  starfun :: "('a => 'b) => ('a star => 'b star)"  ("*f* _" [80] 80) where
  "starfun f == λx. star_of f ∗ x"

definition
  starfun2 :: "('a => 'b => 'c) => ('a star => 'b star => 'c star)"
    ("*f2* _" [80] 80) where
  "starfun2 f == λx y. star_of f ∗ x ∗ y"

declare starfun_def [transfer_unfold]
declare starfun2_def [transfer_unfold]

lemma starfun_star_n: "( *f* f) (star_n X) = star_n (λn. f (X n))"
by (simp only: starfun_def star_of_def Ifun_star_n)

lemma starfun2_star_n:
  "( *f2* f) (star_n X) (star_n Y) = star_n (λn. f (X n) (Y n))"
by (simp only: starfun2_def star_of_def Ifun_star_n)

lemma starfun_star_of [simp]: "( *f* f) (star_of x) = star_of (f x)"
by (transfer, rule refl)

lemma starfun2_star_of [simp]: "( *f2* f) (star_of x) = *f* f x"
by (transfer, rule refl)

lemma Standard_starfun [simp]: "x ∈ Standard ==> starfun f x ∈ Standard"
by (simp add: starfun_def)

lemma Standard_starfun2 [simp]:
  "[|x ∈ Standard; y ∈ Standard|] ==> starfun2 f x y ∈ Standard"
by (simp add: starfun2_def)

lemma Standard_starfun_iff:
  assumes inj: "!!x y. f x = f y ==> x = y"
  shows "(starfun f x ∈ Standard) = (x ∈ Standard)"
proof
  assume "x ∈ Standard"
  thus "starfun f x ∈ Standard" by simp
next
  have inj': "!!x y. starfun f x = starfun f y ==> x = y"
    using inj by transfer
  assume "starfun f x ∈ Standard"
  then obtain b where b: "starfun f x = star_of b"
    unfolding Standard_def ..
  hence "∃x. starfun f x = star_of b" ..
  hence "∃a. f a = b" by transfer
  then obtain a where "f a = b" ..
  hence "starfun f (star_of a) = star_of b" by transfer
  with b have "starfun f x = starfun f (star_of a)" by simp
  hence "x = star_of a" by (rule inj')
  thus "x ∈ Standard"
    unfolding Standard_def by auto
qed

lemma Standard_starfun2_iff:
  assumes inj: "!!a b a' b'. f a b = f a' b' ==> a = a' ∧ b = b'"
  shows "(starfun2 f x y ∈ Standard) = (x ∈ Standard ∧ y ∈ Standard)"
proof
  assume "x ∈ Standard ∧ y ∈ Standard"
  thus "starfun2 f x y ∈ Standard" by simp
next
  have inj': "!!x y z w. starfun2 f x y = starfun2 f z w ==> x = z ∧ y = w"
    using inj by transfer
  assume "starfun2 f x y ∈ Standard"
  then obtain c where c: "starfun2 f x y = star_of c"
    unfolding Standard_def ..
  hence "∃x y. starfun2 f x y = star_of c" by auto
  hence "∃a b. f a b = c" by transfer
  then obtain a b where "f a b = c" by auto
  hence "starfun2 f (star_of a) (star_of b) = star_of c"
    by transfer
  with c have "starfun2 f x y = starfun2 f (star_of a) (star_of b)"
    by simp
  hence "x = star_of a ∧ y = star_of b"
    by (rule inj')
  thus "x ∈ Standard ∧ y ∈ Standard"
    unfolding Standard_def by auto
qed


subsection {* Internal predicates *}

definition
  unstar :: "bool star => bool" where
  "unstar b = (b = star_of True)"

lemma unstar_star_n: "unstar (star_n P) = ({n. P n} ∈ \<U>)"
by (simp add: unstar_def star_of_def star_n_eq_iff)

lemma unstar_star_of [simp]: "unstar (star_of p) = p"
by (simp add: unstar_def star_of_inject)

text {* Transfer tactic should remove occurrences of @{term unstar} *}
setup {* Transfer.add_const "StarDef.unstar" *}

lemma transfer_unstar [transfer_intro]:
  "p ≡ star_n P ==> unstar p ≡ {n. P n} ∈ \<U>"
by (simp only: unstar_star_n)

definition
  starP :: "('a => bool) => 'a star => bool"  ("*p* _" [80] 80) where
  "*p* P = (λx. unstar (star_of P ∗ x))"

definition
  starP2 :: "('a => 'b => bool) => 'a star => 'b star => bool"  ("*p2* _" [80] 80) where
  "*p2* P = (λx y. unstar (star_of P ∗ x ∗ y))"

declare starP_def [transfer_unfold]
declare starP2_def [transfer_unfold]

lemma starP_star_n: "( *p* P) (star_n X) = ({n. P (X n)} ∈ \<U>)"
by (simp only: starP_def star_of_def Ifun_star_n unstar_star_n)

lemma starP2_star_n:
  "( *p2* P) (star_n X) (star_n Y) = ({n. P (X n) (Y n)} ∈ \<U>)"
by (simp only: starP2_def star_of_def Ifun_star_n unstar_star_n)

lemma starP_star_of [simp]: "( *p* P) (star_of x) = P x"
by (transfer, rule refl)

lemma starP2_star_of [simp]: "( *p2* P) (star_of x) = *p* P x"
by (transfer, rule refl)


subsection {* Internal sets *}

definition
  Iset :: "'a set star => 'a star set" where
  "Iset A = {x. ( *p2* op ∈) x A}"

lemma Iset_star_n:
  "(star_n X ∈ Iset (star_n A)) = ({n. X n ∈ A n} ∈ \<U>)"
by (simp add: Iset_def starP2_star_n)

text {* Transfer tactic should remove occurrences of @{term Iset} *}
setup {* Transfer.add_const "StarDef.Iset" *}

lemma transfer_mem [transfer_intro]:
  "[|x ≡ star_n X; a ≡ Iset (star_n A)|]
    ==> x ∈ a ≡ {n. X n ∈ A n} ∈ \<U>"
by (simp only: Iset_star_n)

lemma transfer_Collect [transfer_intro]:
  "[|!!X. p (star_n X) ≡ {n. P n (X n)} ∈ \<U>|]
    ==> Collect p ≡ Iset (star_n (λn. Collect (P n)))"
by (simp add: atomize_eq expand_set_eq all_star_eq Iset_star_n)

lemma transfer_set_eq [transfer_intro]:
  "[|a ≡ Iset (star_n A); b ≡ Iset (star_n B)|]
    ==> a = b ≡ {n. A n = B n} ∈ \<U>"
by (simp only: expand_set_eq transfer_all transfer_iff transfer_mem)

lemma transfer_ball [transfer_intro]:
  "[|a ≡ Iset (star_n A); !!X. p (star_n X) ≡ {n. P n (X n)} ∈ \<U>|]
    ==> ∀x∈a. p x ≡ {n. ∀x∈A n. P n x} ∈ \<U>"
by (simp only: Ball_def transfer_all transfer_imp transfer_mem)

lemma transfer_bex [transfer_intro]:
  "[|a ≡ Iset (star_n A); !!X. p (star_n X) ≡ {n. P n (X n)} ∈ \<U>|]
    ==> ∃x∈a. p x ≡ {n. ∃x∈A n. P n x} ∈ \<U>"
by (simp only: Bex_def transfer_ex transfer_conj transfer_mem)

lemma transfer_Iset [transfer_intro]:
  "[|a ≡ star_n A|] ==> Iset a ≡ Iset (star_n (λn. A n))"
by simp

text {* Nonstandard extensions of sets. *}

definition
  starset :: "'a set => 'a star set" ("*s* _" [80] 80) where
  "starset A = Iset (star_of A)"

declare starset_def [transfer_unfold]

lemma starset_mem: "(star_of x ∈ *s* A) = (x ∈ A)"
by (transfer, rule refl)

lemma starset_UNIV: "*s* (UNIV::'a set) = (UNIV::'a star set)"
by (transfer UNIV_def, rule refl)

lemma starset_empty: "*s* {} = {}"
by (transfer empty_def, rule refl)

lemma starset_insert: "*s* (insert x A) = insert (star_of x) ( *s* A)"
by (transfer insert_def Un_def, rule refl)

lemma starset_Un: "*s* (A ∪ B) = *s* A ∪ *s* B"
by (transfer Un_def, rule refl)

lemma starset_Int: "*s* (A ∩ B) = *s* A ∩ *s* B"
by (transfer Int_def, rule refl)

lemma starset_Compl: "*s* -A = -( *s* A)"
by (transfer Compl_def, rule refl)

lemma starset_diff: "*s* (A - B) = *s* A - *s* B"
by (transfer set_diff_def, rule refl)

lemma starset_image: "*s* (f ` A) = ( *f* f) ` ( *s* A)"
by (transfer image_def, rule refl)

lemma starset_vimage: "*s* (f -` A) = ( *f* f) -` ( *s* A)"
by (transfer vimage_def, rule refl)

lemma starset_subset: "( *s* A ⊆ *s* B) = (A ⊆ B)"
by (transfer subset_def, rule refl)

lemma starset_eq: "( *s* A = *s* B) = (A = B)"
by (transfer, rule refl)

lemmas starset_simps [simp] =
  starset_mem     starset_UNIV
  starset_empty   starset_insert
  starset_Un      starset_Int
  starset_Compl   starset_diff
  starset_image   starset_vimage
  starset_subset  starset_eq

end

A Free Ultrafilter over the Naturals

lemma freeultrafilter_FreeUltrafilterNat:

  freeultrafilter \<U>

lemma ultra:

  [| {n. P n} ∈ \<U>; {n. P n --> Q n} ∈ \<U> |] ==> {n. Q n} ∈ \<U>

Definition of @{text star} type constructor

theorem star_cases:

  (!!X. x = star_n X ==> P) ==> P

lemma all_star_eq:

  (∀x. P x) = (∀X. P (star_n X))

lemma ex_star_eq:

  (∃x. P x) = (∃X. P (star_n X))

lemma starrel_iff:

  ((X, Y) ∈ starrel) = ({n. X n = Y n} ∈ \<U>)

lemma equiv_starrel:

  equiv UNIV starrel

lemma equiv_starrel_iff:

  (starrel `` {x} = starrel `` {y}) = ((x, y) ∈ starrel)

lemma starrel_in_star:

  starrel `` {x} ∈ star

lemma star_n_eq_iff:

  (star_n X = star_n Y) = ({n. X n = Y n} ∈ \<U>)

Transfer principle

lemma transfer_start:

  P == {n. Q} ∈ \<U> ==> P == Q

lemma transfer_ex:

  (!!X. p (star_n X) == {n. P n (X n)} ∈ \<U>)
  ==> ∃x. p x == {n. ∃x. P n x} ∈ \<U>

lemma transfer_all:

  (!!X. p (star_n X) == {n. P n (X n)} ∈ \<U>)
  ==> ∀x. p x == {n. ∀x. P n x} ∈ \<U>

lemma transfer_not:

  p == {n. P n} ∈ \<U> ==> ¬ p == {n. ¬ P n} ∈ \<U>

lemma transfer_conj:

  [| p == {n. P n} ∈ \<U>; q == {n. Q n} ∈ \<U> |]
  ==> pq == {n. P nQ n} ∈ \<U>

lemma transfer_disj:

  [| p == {n. P n} ∈ \<U>; q == {n. Q n} ∈ \<U> |]
  ==> pq == {n. P nQ n} ∈ \<U>

lemma transfer_imp:

  [| p == {n. P n} ∈ \<U>; q == {n. Q n} ∈ \<U> |]
  ==> p --> q == {n. P n --> Q n} ∈ \<U>

lemma transfer_iff:

  [| p == {n. P n} ∈ \<U>; q == {n. Q n} ∈ \<U> |]
  ==> p = q == {n. P n = Q n} ∈ \<U>

lemma transfer_if_bool:

  [| p == {n. P n} ∈ \<U>; x == {n. X n} ∈ \<U>; y == {n. Y n} ∈ \<U> |]
  ==> if p then x else y == {n. if P n then X n else Y n} ∈ \<U>

lemma transfer_eq:

  [| x == star_n X; y == star_n Y |] ==> x = y == {n. X n = Y n} ∈ \<U>

lemma transfer_if:

  [| p == {n. P n} ∈ \<U>; x == star_n X; y == star_n Y |]
  ==> if p then x else y == star_nn. if P n then X n else Y n)

lemma transfer_fun_eq:

  (!!X. f (star_n X) = g (star_n X) == {n. F n (X n) = G n (X n)} ∈ \<U>)
  ==> f = g == {n. F n = G n} ∈ \<U>

lemma transfer_star_n:

  star_n X == star_n X

lemma transfer_bool:

  p == {n. p} ∈ \<U>

Standard elements

lemma star_of_inject:

  (star_of x = star_of y) = (x = y)

lemma Standard_star_of:

  star_of xStandard

Internal functions

lemma Ifun_congruent2:

  congruent2 starrel starrelF X. starrel ``n. F n (X n)})

lemma Ifun_star_n:

  star_n F  star_n X = star_nn. F n (X n))

lemma transfer_Ifun:

  [| f == star_n F; x == star_n X |] ==> f  x == star_nn. F n (X n))

lemma Ifun_star_of:

  star_of f  star_of x = star_of (f x)

lemma Standard_Ifun:

  [| fStandard; xStandard |] ==> f  xStandard

lemma starfun_star_n:

  (*f* f) (star_n X) = star_nn. f (X n))

lemma starfun2_star_n:

  (*f2* f) (star_n X) (star_n Y) = star_nn. f (X n) (Y n))

lemma starfun_star_of:

  (*f* f) (star_of x) = star_of (f x)

lemma starfun2_star_of:

  (*f2* f) (star_of x) = *f* f x

lemma Standard_starfun:

  xStandard ==> (*f* f) xStandard

lemma Standard_starfun2:

  [| xStandard; yStandard |] ==> (*f2* f) x yStandard

lemma Standard_starfun_iff:

  (!!x y. f x = f y ==> x = y) ==> ((*f* f) xStandard) = (xStandard)

lemma Standard_starfun2_iff:

  (!!a b a' b'. f a b = f a' b' ==> a = a'b = b')
  ==> ((*f2* f) x yStandard) = (xStandardyStandard)

Internal predicates

lemma unstar_star_n:

  unstar (star_n P) = ({n. P n} ∈ \<U>)

lemma unstar_star_of:

  unstar (star_of p) = p

lemma transfer_unstar:

  p == star_n P ==> unstar p == {n. P n} ∈ \<U>

lemma starP_star_n:

  (*p* P) (star_n X) = ({n. P (X n)} ∈ \<U>)

lemma starP2_star_n:

  (*p2* P) (star_n X) (star_n Y) = ({n. P (X n) (Y n)} ∈ \<U>)

lemma starP_star_of:

  (*p* P) (star_of x) = P x

lemma starP2_star_of:

  (*p2* P) (star_of x) = *p* P x

Internal sets

lemma Iset_star_n:

  (star_n XIset (star_n A)) = ({n. X nA n} ∈ \<U>)

lemma transfer_mem:

  [| x == star_n X; a == Iset (star_n A) |] ==> xa == {n. X nA n} ∈ \<U>

lemma transfer_Collect:

  (!!X. p (star_n X) == {n. P n (X n)} ∈ \<U>)
  ==> Collect p == Iset (star_nn. Collect (P n)))

lemma transfer_set_eq:

  [| a == Iset (star_n A); b == Iset (star_n B) |]
  ==> a = b == {n. A n = B n} ∈ \<U>

lemma transfer_ball:

  [| a == Iset (star_n A); !!X. p (star_n X) == {n. P n (X n)} ∈ \<U> |]
  ==> ∀xa. p x == {n. ∀xA n. P n x} ∈ \<U>

lemma transfer_bex:

  [| a == Iset (star_n A); !!X. p (star_n X) == {n. P n (X n)} ∈ \<U> |]
  ==> ∃xa. p x == {n. ∃xA n. P n x} ∈ \<U>

lemma transfer_Iset:

  a == star_n A ==> Iset a == Iset (star_n A)

lemma starset_mem:

  (star_of x*s* A) = (xA)

lemma starset_UNIV:

  *s* UNIV = UNIV

lemma starset_empty:

  *s* {} = {}

lemma starset_insert:

  *s* insert x A = insert (star_of x) (*s* A)

lemma starset_Un:

  *s* (AB) = *s* A*s* B

lemma starset_Int:

  *s* (AB) = *s* A*s* B

lemma starset_Compl:

  *s* - A = - (*s* A)

lemma starset_diff:

  *s* (A - B) = *s* A - *s* B

lemma starset_image:

  *s* f ` A = (*f* f) ` (*s* A)

lemma starset_vimage:

  *s* f -` A = (*f* f) -` (*s* A)

lemma starset_subset:

  (*s* A  *s* B) = (A  B)

lemma starset_eq:

  (*s* A = *s* B) = (A = B)

lemma starset_simps:

  (star_of x*s* A) = (xA)
  *s* UNIV = UNIV
  *s* {} = {}
  *s* insert x A = insert (star_of x) (*s* A)
  *s* (AB) = *s* A*s* B
  *s* (AB) = *s* A*s* B
  *s* - A = - (*s* A)
  *s* (A - B) = *s* A - *s* B
  *s* f ` A = (*f* f) ` (*s* A)
  *s* f -` A = (*f* f) -` (*s* A)
  (*s* A  *s* B) = (A  B)
  (*s* A = *s* B) = (A = B)