{-# OPTIONS --allow-unsolved-metas #-}
open import Level
open import Ordinals
module OD {n : Level } (O : Ordinals {n} ) where
open import Data.Nat renaming ( zero to Zero ; suc to Suc ; ℕ to Nat ; _⊔_ to _n⊔_ )
open import Relation.Binary.PropositionalEquality hiding ( [_] )
open import Data.Nat.Properties
open import Data.Empty
open import Data.Unit
open import Relation.Nullary
open import Relation.Binary hiding (_⇔_)
open import Relation.Binary.Core hiding (_⇔_)
open import logic
import OrdUtil
open import nat
open Ordinals.Ordinals O
open Ordinals.IsOrdinals isOrdinal
open OrdUtil O
record OD : Set (suc n ) where
field
def : (x : Ordinal ) → Set n
open OD
open _∧_
open _∨_
open Bool
record _==_ ( a b : OD ) : Set n where
field
eq→ : ∀ { x : Ordinal } → def a x → def b x
eq← : ∀ { x : Ordinal } → def b x → def a x
==-refl : { x : OD } → x == x
==-refl {x} = record { eq→ = λ x → x ; eq← = λ x → x }
open _==_
==-trans : { x y z : OD } → x == y → y == z → x == z
==-trans x=y y=z = record { eq→ = λ {m} t → eq→ y=z (eq→ x=y t) ; eq← = λ {m} t → eq← x=y (eq← y=z t) }
==-sym : { x y : OD } → x == y → y == x
==-sym x=y = record { eq→ = λ {m} t → eq← x=y t ; eq← = λ {m} t → eq→ x=y t }
⇔→== : { x y : OD } → ( {z : Ordinal } → (def x z ⇔ def y z)) → x == y
eq→ ( ⇔→== {x} {y} eq ) {z} m = proj1 eq m
eq← ( ⇔→== {x} {y} eq ) {z} m = proj2 eq m
Ords : OD
Ords = record { def = λ x → Lift n ⊤ }
record HOD : Set (suc n) where
field
od : OD
odmax : Ordinal
<odmax : {y : Ordinal} → def od y → y o< odmax
open HOD
open import Relation.Binary.HeterogeneousEquality as HE using (_≅_ )
record ODAxiom : Set (suc n) where
field
& : HOD → Ordinal
* : Ordinal → HOD
c<→o< : {x y : HOD } → def (od y) ( & x ) → & x o< & y
⊆→o≤ : {y z : HOD } → ({x : Ordinal} → def (od y) x → def (od z) x ) → & y o< osuc (& z)
*iso : {x : HOD } → * ( & x ) ≡ x
&iso : {x : Ordinal } → & ( * x ) ≡ x
==→o≡ : {x y : HOD } → (od x == od y) → x ≡ y
∋-irr : {X : HOD} {x : Ordinal } → (a b : def (od X) x) → a ≅ b
postulate odAxiom : ODAxiom
open ODAxiom odAxiom
odmaxmin : Set (suc n)
odmaxmin = (y : HOD) (z : Ordinal) → ((x : Ordinal)→ def (od y) x → x o< z) → odmax y o< osuc z
¬OD-order : ( & : OD → Ordinal ) → ( * : Ordinal → OD ) → ( { x y : OD } → def y ( & x ) → & x o< & y) → ⊥
¬OD-order & * c<→o< = o≤> <-osuc (c<→o< {Ords} (lift tt) )
Ord : ( a : Ordinal ) → HOD
Ord a = record { od = record { def = λ y → y o< a } ; odmax = a ; <odmax = lemma } where
lemma : {x : Ordinal} → x o< a → x o< a
lemma {x} lt = lt
od∅ : HOD
od∅ = Ord o∅
odef : HOD → Ordinal → Set n
odef A x = def ( od A ) x
_∋_ : ( a x : HOD ) → Set n
_∋_ a x = odef a ( & x )
d→∋ : ( a : HOD ) { x : Ordinal} → odef a x → a ∋ (* x)
d→∋ a lt = subst (λ k → odef a k ) (sym &iso) lt
otrans : {a x y : Ordinal } → odef (Ord a) x → odef (Ord x) y → odef (Ord a) y
otrans x<a y<x = ordtrans y<x x<a
∈→c<→HOD=Ord : ( o<→c< : {x y : Ordinal } → x o< y → odef (* y) x ) → {x : HOD } → x ≡ Ord (& x)
∈→c<→HOD=Ord o<→c< {x} = ==→o≡ ( record { eq→ = lemma1 ; eq← = lemma2 } ) where
lemma1 : {y : Ordinal} → odef x y → odef (Ord (& x)) y
lemma1 {y} lt = subst ( λ k → k o< & x ) &iso (c<→o< {* y} {x} (d→∋ x lt))
lemma2 : {y : Ordinal} → odef (Ord (& x)) y → odef x y
lemma2 {y} lt = subst (λ k → odef k y ) *iso (o<→c< {y} {& x} lt )
orefl : { x : HOD } → { y : Ordinal } → & x ≡ y → & x ≡ y
orefl refl = refl
==-iso : { x y : HOD } → od (* (& x)) == od (* (& y)) → od x == od y
==-iso {x} {y} eq = record {
eq→ = λ {z} d → lemma ( eq→ eq (subst (λ k → odef k z ) (sym *iso) d )) ;
eq← = λ {z} d → lemma ( eq← eq (subst (λ k → odef k z ) (sym *iso) d )) }
where
lemma : {x : HOD } {z : Ordinal } → odef (* (& x)) z → odef x z
lemma {x} {z} d = subst (λ k → odef k z) (*iso) d
=-iso : {x y : HOD } → (od x == od y) ≡ (od (* (& x)) == od y)
=-iso {_} {y} = cong ( λ k → od k == od y ) (sym *iso)
ord→== : { x y : HOD } → & x ≡ & y → od x == od y
ord→== {x} {y} eq = ==-iso (lemma (& x) (& y) (orefl eq)) where
lemma : ( ox oy : Ordinal ) → ox ≡ oy → od (* ox) == od (* oy)
lemma ox ox refl = ==-refl
o≡→== : { x y : Ordinal } → x ≡ y → od (* x) == od (* y)
o≡→== {x} {.x} refl = ==-refl
*≡*→≡ : { x y : Ordinal } → * x ≡ * y → x ≡ y
*≡*→≡ eq = subst₂ (λ j k → j ≡ k ) &iso &iso ( cong (&) eq )
&≡&→≡ : { x y : HOD } → & x ≡ & y → x ≡ y
&≡&→≡ eq = subst₂ (λ j k → j ≡ k ) *iso *iso ( cong (*) eq )
o∅≡od∅ : * (o∅ ) ≡ od∅
o∅≡od∅ = ==→o≡ lemma where
lemma0 : {x : Ordinal} → odef (* o∅) x → odef od∅ x
lemma0 {x} lt with c<→o< {* x} {* o∅} (subst (λ k → odef (* o∅) k ) (sym &iso) lt)
... | t = subst₂ (λ j k → j o< k ) &iso &iso t
lemma1 : {x : Ordinal} → odef od∅ x → odef (* o∅) x
lemma1 {x} lt = ⊥-elim (¬x<0 lt)
lemma : od (* o∅) == od od∅
lemma = record { eq→ = lemma0 ; eq← = lemma1 }
ord-od∅ : & (od∅ ) ≡ o∅
ord-od∅ = sym ( subst (λ k → k ≡ & (od∅ ) ) &iso (cong ( λ k → & k ) o∅≡od∅ ) )
≡o∅→=od∅ : {x : HOD} → & x ≡ o∅ → od x == od od∅
≡o∅→=od∅ {x} eq = record { eq→ = λ {y} lt → ⊥-elim ( ¬x<0 {y} (subst₂ (λ j k → j o< k ) &iso eq ( c<→o< {* y} {x} (d→∋ x lt))))
; eq← = λ {y} lt → ⊥-elim ( ¬x<0 lt )}
=od∅→≡o∅ : {x : HOD} → od x == od od∅ → & x ≡ o∅
=od∅→≡o∅ {x} eq = trans (cong (λ k → & k ) (==→o≡ {x} {od∅} eq)) ord-od∅
≡od∅→=od∅ : {x : HOD} → x ≡ od∅ → od x == od od∅
≡od∅→=od∅ {x} eq = ≡o∅→=od∅ (subst (λ k → & x ≡ k ) ord-od∅ ( cong & eq ) )
∅0 : record { def = λ x → Lift n ⊥ } == od od∅
eq→ ∅0 {w} (lift ())
eq← ∅0 {w} lt = lift (¬x<0 lt)
∅< : { x y : HOD } → odef x (& y ) → ¬ ( od x == od od∅ )
∅< {x} {y} d eq with eq→ (==-trans eq (==-sym ∅0) ) d
∅< {x} {y} d eq | lift ()
¬x∋y→x≡od∅ : { x : HOD } → ({y : Ordinal } → ¬ odef x y ) → x ≡ od∅
¬x∋y→x≡od∅ {x} nxy = ==→o≡ record { eq→ = λ {y} lt → ⊥-elim (nxy lt) ; eq← = λ {y} lt → ⊥-elim (¬x<0 lt) }
0<P→ne : { x : HOD } → o∅ o< & x → ¬ ( od x == od od∅ )
0<P→ne {x} 0<x eq = ⊥-elim ( o<¬≡ (sym (=od∅→≡o∅ eq)) 0<x )
∈∅< : { x : HOD } {y : Ordinal } → odef x y → o∅ o< (& x)
∈∅< {x} {y} d with trio< o∅ (& x)
... | tri< a ¬b ¬c = a
... | tri≈ ¬a b ¬c = ⊥-elim ( ∅< {x} {* y} (subst (λ k → odef x k ) (sym &iso) d ) ( ≡o∅→=od∅ (sym b) ) )
... | tri> ¬a ¬b c = ⊥-elim ( ¬x<0 c )
∅6 : { x : HOD } → ¬ ( x ∋ x )
∅6 {x} x∋x = o<¬≡ refl ( c<→o< {x} {x} x∋x )
odef-iso : {A B : HOD } {x y : Ordinal } → x ≡ y → (odef A y → odef B y) → odef A x → odef B x
odef-iso refl t = t
is-o∅ : ( x : Ordinal ) → Dec ( x ≡ o∅ )
is-o∅ x with trio< x o∅
is-o∅ x | tri< a ¬b ¬c = no ¬b
is-o∅ x | tri≈ ¬a b ¬c = yes b
is-o∅ x | tri> ¬a ¬b c = no ¬b
odef< : {b : Ordinal } { A : HOD } → odef A b → b o< & A
odef< {b} {A} ab = subst (λ k → k o< & A) &iso ( c<→o< (subst (λ k → odef A k ) (sym &iso ) ab))
odef∧< : {A : HOD } {y : Ordinal} {n : Level } → {P : Set n} → odef A y ∧ P → y o< & A
odef∧< {A } {y} p = subst (λ k → k o< & A) &iso ( c<→o< (subst (λ k → odef A k ) (sym &iso ) (proj1 p )))
_,_ : HOD → HOD → HOD
x , y = record { od = record { def = λ t → (t ≡ & x ) ∨ ( t ≡ & y ) } ; odmax = omax (& x) (& y) ; <odmax = lemma } where
lemma : {t : Ordinal} → (t ≡ & x) ∨ (t ≡ & y) → t o< omax (& x) (& y)
lemma {t} (case1 refl) = omax-x _ _
lemma {t} (case2 refl) = omax-y _ _
pair<y : {x y : HOD } → y ∋ x → & (x , x) o< osuc (& y)
pair<y {x} {y} y∋x = ⊆→o≤ lemma where
lemma : {z : Ordinal} → def (od (x , x)) z → def (od y) z
lemma (case1 refl) = y∋x
lemma (case2 refl) = y∋x
odmax<& : { x y : HOD } → x ∋ y → Set n
odmax<& {x} {y} x∋y = odmax x o< & x
in-codomain : (X : HOD ) → ( ψ : HOD → HOD ) → OD
in-codomain X ψ = record { def = λ x → ¬ ( (y : Ordinal ) → ¬ ( odef X y ∧ ( x ≡ & (ψ (* y ))))) }
_∩_ : ( A B : HOD ) → HOD
A ∩ B = record { od = record { def = λ x → odef A x ∧ odef B x }
; odmax = omin (odmax A) (odmax B) ; <odmax = λ y → min1 (<odmax A (proj1 y)) (<odmax B (proj2 y))}
_⊆_ : ( A B : HOD) → Set n
_⊆_ A B = { x : Ordinal } → odef A x → odef B x
infixr 220 _⊆_
⊆→o≤→c<→o< : ({x : HOD} → & (x , x) ≡ osuc (& x) )
→ ({y z : HOD } → ({x : Ordinal} → def (od y) x → def (od z) x ) → & y o< osuc (& z) )
→ {x y : HOD } → def (od y) ( & x ) → & x o< & y
⊆→o≤→c<→o< peq ⊆→o≤ {x} {y} y∋x with trio< (& x) (& y)
⊆→o≤→c<→o< peq ⊆→o≤ {x} {y} y∋x | tri< a ¬b ¬c = a
⊆→o≤→c<→o< peq ⊆→o≤ {x} {y} y∋x | tri≈ ¬a b ¬c = ⊥-elim ( o<¬≡ (peq {x}) (pair<y (subst (λ k → k ∋ x) (sym ( ==→o≡ {x} {y} (ord→== b))) y∋x )))
⊆→o≤→c<→o< peq ⊆→o≤ {x} {y} y∋x | tri> ¬a ¬b c =
⊥-elim ( o<> (⊆→o≤ {x , x} {y} y⊆x,x ) lemma1 ) where
lemma : {z : Ordinal} → (z ≡ & x) ∨ (z ≡ & x) → & x ≡ z
lemma (case1 refl) = refl
lemma (case2 refl) = refl
y⊆x,x : {z : Ordinal} → def (od (x , x)) z → def (od y) z
y⊆x,x {z} lt = subst (λ k → def (od y) k ) (lemma lt) y∋x
lemma1 : osuc (& y) o< & (x , x)
lemma1 = subst (λ k → osuc (& y) o< k ) (sym (peq {x})) (osucc c )
ε-induction : { ψ : HOD → Set (suc n)}
→ ( {x : HOD } → ({ y : HOD } → x ∋ y → ψ y ) → ψ x )
→ (x : HOD ) → ψ x
ε-induction {ψ} ind x = subst (λ k → ψ k ) *iso (ε-induction-ord (osuc (& x)) <-osuc ) where
induction : (ox : Ordinal) → ((oy : Ordinal) → oy o< ox → ψ (* oy)) → ψ (* ox)
induction ox prev = ind ( λ {y} lt → subst (λ k → ψ k ) *iso (prev (& y) (o<-subst (c<→o< lt) refl &iso )))
ε-induction-ord : (ox : Ordinal) { oy : Ordinal } → oy o< ox → ψ (* oy)
ε-induction-ord ox {oy} lt = TransFinite {λ oy → ψ (* oy)} induction oy
ε-induction0 : { ψ : HOD → Set n}
→ ( {x : HOD } → ({ y : HOD } → x ∋ y → ψ y ) → ψ x )
→ (x : HOD ) → ψ x
ε-induction0 {ψ} ind x = subst (λ k → ψ k ) *iso (ε-induction-ord (osuc (& x)) <-osuc ) where
induction : (ox : Ordinal) → ((oy : Ordinal) → oy o< ox → ψ (* oy)) → ψ (* ox)
induction ox prev = ind ( λ {y} lt → subst (λ k → ψ k ) *iso (prev (& y) (o<-subst (c<→o< lt) refl &iso )))
ε-induction-ord : (ox : Ordinal) { oy : Ordinal } → oy o< ox → ψ (* oy)
ε-induction-ord ox {oy} lt = inOrdinal.TransFinite0 O {λ oy → ψ (* oy)} induction oy
¬open-sup : ( sup-o : (Ordinal → Ordinal ) → Ordinal) → ((ψ : Ordinal → Ordinal ) → (x : Ordinal) → ψ x o< sup-o ψ ) → ⊥
¬open-sup sup-o sup-o< = o<> <-osuc (sup-o< next-ord (sup-o next-ord)) where
next-ord : Ordinal → Ordinal
next-ord x = osuc x
Select : (X : HOD ) → ((x : HOD ) → Set n ) → HOD
Select X ψ = record { od = record { def = λ x → ( odef X x ∧ ψ ( * x )) } ; odmax = odmax X ; <odmax = λ y → <odmax X (proj1 y) }
_=h=_ : (x y : HOD) → Set n
x =h= y = od x == od y
record Own (A : HOD) (x : Ordinal) : Set n where
field
owner : Ordinal
ao : odef A owner
ox : odef (* owner) x
Union : HOD → HOD
Union U = record { od = record { def = λ x → Own U x } ; odmax = osuc (& U) ; <odmax = umax } where
umax : {y : Ordinal} → Own U y → y o< osuc (& U)
umax {y} uy = o<→≤ ( ordtrans (odef< (Own.ox uy)) (subst (λ k → k o< & U) (sym &iso) umax1) ) where
umax1 : Own.owner uy o< & U
umax1 = odef< (Own.ao uy)
union→ : (X z u : HOD) → (X ∋ u) ∧ (u ∋ z) → Union X ∋ z
union→ X z u xx = record { owner = & u ; ao = proj1 xx ; ox = subst (λ k → odef k (& z)) (sym *iso) (proj2 xx) }
union← : (X z : HOD) (X∋z : Union X ∋ z) → ¬ ( (u : HOD ) → ¬ ((X ∋ u) ∧ (u ∋ z )))
union← X z UX∋z not = ⊥-elim ( not (* (Own.owner UX∋z)) ⟪ subst (λ k → odef X k) (sym &iso) ( Own.ao UX∋z) , Own.ox UX∋z ⟫ )
record RCod (COD : HOD) (ψ : HOD → HOD) : Set (suc n) where
field
≤COD : ∀ {x : HOD } → ψ x ⊆ COD
record Replaced (A : HOD) (ψ : Ordinal → Ordinal ) (x : Ordinal ) : Set n where
field
z : Ordinal
az : odef A z
x=ψz : x ≡ ψ z
Replace : (D : HOD) → (ψ : HOD → HOD) → {C : HOD} → RCod C ψ → HOD
Replace X ψ {C} rc = record { od = record { def = λ x → Replaced X (λ z → & (ψ (* z))) x } ; odmax = osuc (& C)
; <odmax = rmax< } where
rmax< : {y : Ordinal} → Replaced X (λ z → & (ψ (* z))) y → y o< osuc (& C)
rmax< {y} lt = subst (λ k → k o< osuc (& C)) r01 ( ⊆→o≤ (RCod.≤COD rc) ) where
r01 : & (ψ ( * (Replaced.z lt ) )) ≡ y
r01 = sym (Replaced.x=ψz lt )
replacement← : {ψ : HOD → HOD} (X x : HOD) → X ∋ x → {C : HOD} → (rc : RCod C ψ) → Replace X ψ rc ∋ ψ x
replacement← {ψ} X x lt {C} rc = record { z = & x ; az = lt ; x=ψz = cong (λ k → & (ψ k)) (sym *iso) }
replacement→ : {ψ : HOD → HOD} (X x : HOD) → {C : HOD} → (rc : RCod C ψ ) → (lt : Replace X ψ rc ∋ x)
→ ¬ ( (y : HOD) → ¬ (x =h= ψ y))
replacement→ {ψ} X x {C} rc lt eq = eq (* (Replaced.z lt)) (ord→== (Replaced.x=ψz lt))
record RXCod (X COD : HOD) (ψ : (x : HOD) → X ∋ x → HOD) : Set (suc n) where
field
≤COD : ∀ {x : HOD } → (lt : X ∋ x) → ψ x lt ⊆ COD
record Replaced1 (A : HOD) (ψ : (x : Ordinal ) → odef A x → Ordinal ) (x : Ordinal ) : Set n where
field
z : Ordinal
az : odef A z
x=ψz : x ≡ ψ z az
Replace' : (X : HOD) → (ψ : (x : HOD) → X ∋ x → HOD) → {C : HOD} → RXCod X C ψ → HOD
Replace' X ψ {C} rc = record { od = record { def = λ x → Replaced1 X (λ z xz → & (ψ (* z) (subst (λ k → odef X k) (sym &iso) xz) )) x } ; odmax = osuc (& C) ; <odmax = rmax< } where
rmax< : {y : Ordinal} → Replaced1 X (λ z xz → & (ψ (* z) (subst (λ k → odef X k) (sym &iso) xz) )) y → y o< osuc (& C)
rmax< {y} lt = subst (λ k → k o< osuc (& C)) r01 ( ⊆→o≤ (RXCod.≤COD rc (subst (λ k → odef X k) (sym &iso) (Replaced1.az lt) ))) where
r01 : & (ψ ( * (Replaced1.z lt ) ) (subst (λ k → odef X k) (sym &iso) (Replaced1.az lt) )) ≡ y
r01 = sym (Replaced1.x=ψz lt )
cod-conv : (X : HOD) → (ψ : (x : HOD) → X ∋ x → HOD) → {C : HOD} → (rc : RXCod X C ψ )
→ RXCod (* (& X)) C (λ y xy → ψ y (subst (λ k → k ∋ y) *iso xy))
cod-conv X ψ {C} rc = record { ≤COD = λ {x} lt → RXCod.≤COD rc (subst (λ k → odef k (& x)) *iso lt) }
Replace'-iso : {X Y : HOD} → {fx : (x : HOD) → X ∋ x → HOD} {fy : (x : HOD) → Y ∋ x → HOD}
→ {CX : HOD} → (rcx : RXCod X CX fx ) → {CY : HOD} → (rcy : RXCod Y CY fy )
→ X ≡ Y → ( (x : HOD) → (xx : X ∋ x ) → (yy : Y ∋ x ) → fx _ xx ≡ fy _ yy )
→ Replace' X fx rcx ≡ Replace' Y fy rcy
Replace'-iso {X} {X} {fx} {fy} _ _ refl eq = ==→o≡ record { eq→ = ri0 ; eq← = ri1 } where
ri0 : {x : Ordinal} → Replaced1 X (λ z xz → & (fx (* z) (subst (odef X) (sym &iso) xz))) x
→ Replaced1 X (λ z xz → & (fy (* z) (subst (odef X) (sym &iso) xz))) x
ri0 {x} record { z = z ; az = az ; x=ψz = x=ψz } = record { z = z ; az = az ; x=ψz = trans x=ψz (cong (&) ( eq _ xz xz )) } where
xz : X ∋ * z
xz = subst (λ k → odef X k ) (sym &iso) az
ri1 : {x : Ordinal} → Replaced1 X (λ z xz → & (fy (* z) (subst (odef X) (sym &iso) xz))) x
→ Replaced1 X (λ z xz → & (fx (* z) (subst (odef X) (sym &iso) xz))) x
ri1 {x} record { z = z ; az = az ; x=ψz = x=ψz } = record { z = z ; az = az ; x=ψz = trans x=ψz (cong (&) (sym ( eq _ xz xz ))) } where
xz : X ∋ * z
xz = subst (λ k → odef X k ) (sym &iso) az
Replace'-iso1 : (X : HOD) → (ψ : (x : HOD) → X ∋ x → HOD) → {C : HOD} → (rc : RXCod X C ψ )
→ Replace' (* (& X)) (λ y xy → ψ y (subst (λ k → k ∋ y ) *iso xy) ) (cod-conv X ψ rc)
≡ Replace' X ( λ y xy → ψ y xy ) rc
Replace'-iso1 X ψ rc = Replace'-iso {* (& X)} {X} {λ y xy → ψ y (subst (λ k → k ∋ y ) *iso xy) } { λ y xy → ψ y xy }
(cod-conv X ψ rc) rc
*iso (λ x xx yx → fi00 x xx yx ) where
fi00 : (x : HOD ) → (xx : (* (& X)) ∋ x ) → (yx : X ∋ x) → ψ x (subst (λ k → k ∋ x) *iso xx) ≡ ψ x yx
fi00 x xx yx = cong (λ k → ψ x k ) ( HE.≅-to-≡ ( ∋-irr {X} {& x} (subst (λ k → k ∋ x) *iso xx) yx ) )
_∈_ : ( A B : HOD ) → Set n
A ∈ B = B ∋ A
Power : HOD → HOD
Power A = record { od = record { def = λ x → ( z : Ordinal) → odef (* x) z → odef A z } ; odmax = osuc (& A)
; <odmax = p00 } where
p00 : {y : Ordinal} → ((z : Ordinal) → odef (* y) z → odef A z) → y o< osuc (& A)
p00 {y} y⊆A = p01 where
p01 : y o≤ & A
p01 = subst (λ k → k o≤ & A) &iso ( ⊆→o≤ (λ {x} yx → y⊆A x yx ))
power→ : ( A t : HOD) → Power A ∋ t → {x : HOD} → t ∋ x → A ∋ x
power→ A t P∋t {x} t∋x = P∋t (& x) (subst (λ k → odef k (& x) ) (sym *iso) t∋x )
power← : (A t : HOD) → ({x : HOD} → (t ∋ x → A ∋ x)) → Power A ∋ t
power← A t t⊆A z xz = subst (λ k → odef A k ) &iso ( t⊆A (subst₂ (λ j k → odef j k) *iso (sym &iso) xz ))
Power∋∅ : {S : HOD} → odef (Power S) o∅
Power∋∅ z xz = ⊥-elim (¬x<0 (subst (λ k → odef k z) o∅≡od∅ xz) )
Intersection : (X : HOD ) → HOD
Intersection X = record { od = record { def = λ x → (x o≤ & X ) ∧ ( {y : Ordinal} → odef X y → odef (* y) x )} ; odmax = osuc (& X) ; <odmax = λ lt → proj1 lt }
empty : (x : HOD ) → ¬ (od∅ ∋ x)
empty x = ¬x<0
data Omega-d : ( x : Ordinal ) → Set n where
iφ : Omega-d o∅
isuc : {x : Ordinal } → Omega-d x →
Omega-d (& ( Union (* x , (* x , * x ) ) ))
Omega-od : OD
Omega-od = record { def = λ x → Omega-d x }
o∅<x : {x : Ordinal} → o∅ o≤ x
o∅<x {x} with trio< o∅ x
... | tri< a ¬b ¬c = o<→≤ a
... | tri≈ ¬a b ¬c = o≤-refl0 b
... | tri> ¬a ¬b c = ⊥-elim (¬x<0 c)
¬0=ux : {x : HOD} → ¬ o∅ ≡ & (Union ( x , ( x , x)))
¬0=ux {x} eq = ⊥-elim ( o<¬≡ eq (ordtrans≤-< o∅<x (subst (λ k → k o< & (Union (x , (x , x)))) &iso (c<→o< lemma ) ))) where
lemma : Own (x , (x , x)) (& ( * (& x )))
lemma = record { owner = _ ; ao = case2 refl ; ox = subst₂ (λ j k → odef j k ) (sym *iso) (sym &iso) (case1 refl) }
ux-2cases : {x y : HOD } → Union ( x , ( x , x)) ∋ y → ( x ≡ y ) ∨ ( x ∋ y )
ux-2cases {x} {y} record { owner = owner ; ao = (case1 eq) ; ox = ox } = case2 (subst (λ k → odef k (& y)) (trans (cong (*) eq) *iso) ox)
ux-2cases {x} {y} record { owner = owner ; ao = (case2 eq) ; ox = ox } with subst (λ k → odef k (& y)) (trans (cong (*) eq) *iso) ox
... | case1 eq = case1 (sym (&≡&→≡ eq))
... | case2 eq = case1 (sym (&≡&→≡ eq))
ux-transitve : {x y : HOD} → x ∋ y → Union ( x , ( x , x)) ∋ y
ux-transitve {x} {y} ox = record { owner = _ ; ao = case1 refl ; ox = subst (λ k → odef k (& y)) (sym *iso) ox }
record ODAxiom-ho< : Set (suc n) where
field
omega : Ordinal
ho< : {x : Ordinal } → Omega-d x → x o< omega
postulate
odaxion-ho< : ODAxiom-ho<
open ODAxiom-ho< odaxion-ho<
Omega : HOD
Omega = record { od = record { def = λ x → Omega-d x } ; odmax = omega ; <odmax = ho<}
infinity∅ : Omega ∋ od∅
infinity∅ = subst (λ k → odef Omega k ) lemma iφ where
lemma : o∅ ≡ & od∅
lemma = let open ≡-Reasoning in begin
o∅
≡⟨ sym &iso ⟩
& ( * o∅ )
≡⟨ cong ( λ k → & k ) o∅≡od∅ ⟩
& od∅
∎
infinity : (x : HOD) → Omega ∋ x → Omega ∋ Union (x , (x , x ))
infinity x lt = subst (λ k → odef Omega k ) lemma (isuc {& x} lt) where
lemma : & (Union (* (& x) , (* (& x) , * (& x))))
≡ & (Union (x , (x , x)))
lemma = cong (λ k → & (Union ( k , ( k , k ) ))) *iso
pair→ : ( x y t : HOD ) → (x , y) ∋ t → ( t =h= x ) ∨ ( t =h= y )
pair→ x y t (case1 t≡x ) = case1 (subst₂ (λ j k → j =h= k ) *iso *iso (o≡→== t≡x ))
pair→ x y t (case2 t≡y ) = case2 (subst₂ (λ j k → j =h= k ) *iso *iso (o≡→== t≡y ))
pair← : ( x y t : HOD ) → ( t =h= x ) ∨ ( t =h= y ) → (x , y) ∋ t
pair← x y t (case1 t=h=x) = case1 (cong (λ k → & k ) (==→o≡ t=h=x))
pair← x y t (case2 t=h=y) = case2 (cong (λ k → & k ) (==→o≡ t=h=y))
o<→c< : {x y : Ordinal } → x o< y → (Ord x) ⊆ (Ord y)
o<→c< lt {z} ox = ordtrans ox lt
⊆→o< : {x y : Ordinal } → (Ord x) ⊆ (Ord y) → x o< osuc y
⊆→o< {x} {y} lt with trio< x y
⊆→o< {x} {y} lt | tri< a ¬b ¬c = ordtrans a <-osuc
⊆→o< {x} {y} lt | tri≈ ¬a b ¬c = subst ( λ k → k o< osuc y) (sym b) <-osuc
⊆→o< {x} {y} lt | tri> ¬a ¬b c with lt (o<-subst c (sym &iso) refl )
... | ttt = ⊥-elim ( o<¬≡ refl (o<-subst ttt &iso refl ))
ψiso : {ψ : HOD → Set n} {x y : HOD } → ψ x → x ≡ y → ψ y
ψiso {ψ} t refl = t
selection : {ψ : HOD → Set n} {X y : HOD} → ((X ∋ y) ∧ ψ y) ⇔ (Select X ψ ∋ y)
selection {ψ} {X} {y} = ⟪
( λ cond → ⟪ proj1 cond , ψiso {ψ} (proj2 cond) (sym *iso) ⟫ )
, ( λ select → ⟪ proj1 select , ψiso {ψ} (proj2 select) *iso ⟫ )
⟫
selection-in-domain : {ψ : HOD → Set n} {X y : HOD} → Select X ψ ∋ y → X ∋ y
selection-in-domain {ψ} {X} {y} lt = proj1 ((proj2 (selection {ψ} {X} )) lt)
∩-≡ : { a b : HOD } → ({x : HOD } → (a ∋ x → b ∋ x)) → a =h= ( b ∩ a )
∩-≡ {a} {b} inc = record {
eq→ = λ {x} x<a → ⟪ (subst (λ k → odef b k ) &iso (inc (d→∋ a x<a))) , x<a ⟫ ;
eq← = λ {x} x<a∩b → proj2 x<a∩b }
extensionality0 : {A B : HOD } → ((z : HOD) → (A ∋ z) ⇔ (B ∋ z)) → A =h= B
eq→ (extensionality0 {A} {B} eq ) {x} d = odef-iso {A} {B} (sym &iso) (proj1 (eq (* x))) d
eq← (extensionality0 {A} {B} eq ) {x} d = odef-iso {B} {A} (sym &iso) (proj2 (eq (* x))) d
extensionality : {A B w : HOD } → ((z : HOD ) → (A ∋ z) ⇔ (B ∋ z)) → (w ∋ A) ⇔ (w ∋ B)
proj1 (extensionality {A} {B} {w} eq ) d = subst (λ k → w ∋ k) ( ==→o≡ (extensionality0 {A} {B} eq) ) d
proj2 (extensionality {A} {B} {w} eq ) d = subst (λ k → w ∋ k) (sym ( ==→o≡ (extensionality0 {A} {B} eq) )) d
open import zf
record ODAxiom-sup : Set (suc n) where
field
sup-o : (A : HOD) → ( ( x : Ordinal ) → def (od A) x → Ordinal ) → Ordinal
sup-o≤ : (A : HOD) → { ψ : ( x : Ordinal ) → def (od A) x → Ordinal }
→ ∀ {x : Ordinal } → (lt : def (od A) x ) → ψ x lt o≤ sup-o A ψ
sup-c≤ : (ψ : HOD → HOD) → {X x : HOD} → def (od X) (& x) → & (ψ x) o≤ (sup-o X (λ y X∋y → & (ψ (* y))))
sup-c≤ ψ {X} {x} lt = subst (λ k → & (ψ k) o< _ ) *iso (sup-o≤ X lt )
open ODAxiom-sup
ZFReplace : ODAxiom-sup → HOD → (HOD → HOD) → HOD
ZFReplace os X ψ = record { od = record { def = λ x → Replaced X (λ z → & (ψ (* z))) x } ; odmax = rmax ; <odmax = rmax< } where
rmax : Ordinal
rmax = osuc ( sup-o os X (λ y X∋y → & (ψ (* y) )) )
rmax< : {y : Ordinal} → Replaced X (λ z → & (ψ (* z))) y → y o< rmax
rmax< {y} lt = subst (λ k → k o< rmax) r01 ( sup-o≤ os X (Replaced.az lt) ) where
r01 : & (ψ ( * (Replaced.z lt ) )) ≡ y
r01 = sym (Replaced.x=ψz lt )
zf-replacement← : (os : ODAxiom-sup) → {ψ : HOD → HOD} (X x : HOD) → X ∋ x → ZFReplace os X ψ ∋ ψ x
zf-replacement← os {ψ} X x lt = record { z = & x ; az = lt ; x=ψz = cong (λ k → & (ψ k)) (sym *iso) }
zf-replacement→ : (os : ODAxiom-sup ) → {ψ : HOD → HOD} (X x : HOD) → (lt : ZFReplace os X ψ ∋ x) → ¬ ( (y : HOD) → ¬ (x =h= ψ y))
zf-replacement→ os {ψ} X x lt eq = eq (* (Replaced.z lt)) (ord→== (Replaced.x=ψz lt))
isZF : (os : ODAxiom-sup) → IsZF HOD _∋_ _=h=_ od∅ _,_ Union Power Select (ZFReplace os) Omega
isZF os = record {
isEquivalence = record { refl = ==-refl ; sym = ==-sym; trans = ==-trans }
; pair→ = pair→
; pair← = pair←
; union→ = union→
; union← = union←
; empty = empty
; power→ = power→
; power← = power←
; extensionality = λ {A} {B} {w} → extensionality {A} {B} {w}
; ε-induction = ε-induction
; infinity∅ = infinity∅
; infinity = infinity
; selection = λ {X} {ψ} {y} → selection {X} {ψ} {y}
; replacement← = zf-replacement← os
; replacement→ = λ {ψ} → zf-replacement→ os {ψ}
}
HOD→ZF : ODAxiom-sup → ZF
HOD→ZF os = record {
ZFSet = HOD
; _∋_ = _∋_
; _≈_ = _=h=_
; ∅ = od∅
; _,_ = _,_
; Union = Union
; Power = Power
; Select = Select
; Replace = ZFReplace os
; infinite = Omega
; isZF = isZF os
}