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1 {-# OPTIONS --allow-unsolved-metas #-}
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2 open import Level
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3 open import Ordinals
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4 module OD {n : Level } (O : Ordinals {n} ) where
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5
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6 open import zf
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7 open import Data.Nat renaming ( zero to Zero ; suc to Suc ; ℕ to Nat ; _⊔_ to _n⊔_ )
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8 open import Relation.Binary.PropositionalEquality hiding ( [_] )
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9 open import Data.Nat.Properties
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10 open import Data.Empty
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11 open import Data.Unit
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12 open import Relation.Nullary
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13 open import Relation.Binary hiding (_⇔_)
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14 open import Relation.Binary.Core hiding (_⇔_)
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15
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16 open import logic
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17 import OrdUtil
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18 open import nat
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19
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20 open Ordinals.Ordinals O
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21 open Ordinals.IsOrdinals isOrdinal
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22 open Ordinals.IsNext isNext
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23 open OrdUtil O
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24
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25 -- Ordinal Definable Set
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26
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27 record OD : Set (suc n ) where
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28 field
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29 def : (x : Ordinal ) → Set n
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30
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31 open OD
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32
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33 open _∧_
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34 open _∨_
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35 open Bool
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36
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37 record _==_ ( a b : OD ) : Set n where
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38 field
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39 eq→ : ∀ { x : Ordinal } → def a x → def b x
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40 eq← : ∀ { x : Ordinal } → def b x → def a x
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41
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42 ==-refl : { x : OD } → x == x
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43 ==-refl {x} = record { eq→ = λ x → x ; eq← = λ x → x }
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44
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45 open _==_
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46
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47 ==-trans : { x y z : OD } → x == y → y == z → x == z
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48 ==-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) }
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49
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50 ==-sym : { x y : OD } → x == y → y == x
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51 ==-sym x=y = record { eq→ = λ {m} t → eq← x=y t ; eq← = λ {m} t → eq→ x=y t }
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52
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53
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54 ⇔→== : { x y : OD } → ( {z : Ordinal } → (def x z ⇔ def y z)) → x == y
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55 eq→ ( ⇔→== {x} {y} eq ) {z} m = proj1 eq m
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56 eq← ( ⇔→== {x} {y} eq ) {z} m = proj2 eq m
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57
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58 -- next assumptions are our axiom
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59 --
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60 -- OD is an equation on Ordinals, so it contains Ordinals. If these Ordinals have one-to-one
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61 -- correspondence to the OD then the OD looks like a ZF Set.
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62 --
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63 -- If all ZF Set have supreme upper bound, the solutions of OD have to be bounded, i.e.
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64 -- bbounded ODs are ZF Set. Unbounded ODs are classes.
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65 --
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66 -- In classical Set Theory, HOD is used, as a subset of OD,
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67 -- HOD = { x | TC x ⊆ OD }
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68 -- where TC x is a transitive clusure of x, i.e. Union of all elemnts of all subset of x.
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69 -- This is not possible because we don't have V yet. So we assumes HODs are bounded OD.
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70 --
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71 -- We also assumes HODs are isomorphic to Ordinals, which is ususally proved by Goedel number tricks.
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72 -- There two contraints on the HOD order, one is ∋, the other one is ⊂.
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73 -- ODs have an ovbious maximum, but Ordinals are not, but HOD has no maximum because there is an aribtrary
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74 -- bound on each HOD.
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75 --
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76 -- In classical Set Theory, sup is defined by Uion, since we are working on constructive logic,
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77 -- we need explict assumption on sup.
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78 --
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79 -- ==→o≡ is necessary to prove axiom of extensionality.
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80
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81 -- Ordinals in OD , the maximum
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82 Ords : OD
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83 Ords = record { def = λ x → Lift n ⊤ }
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84
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85 record HOD : Set (suc n) where
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86 field
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87 od : OD
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88 odmax : Ordinal
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89 <odmax : {y : Ordinal} → def od y → y o< odmax
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90
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91 open HOD
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92
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93 record ODAxiom : Set (suc n) where
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94 field
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95 -- HOD is isomorphic to Ordinal (by means of Goedel number)
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96 & : HOD → Ordinal
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97 * : Ordinal → HOD
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98 c<→o< : {x y : HOD } → def (od y) ( & x ) → & x o< & y
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99 ⊆→o≤ : {y z : HOD } → ({x : Ordinal} → def (od y) x → def (od z) x ) → & y o< osuc (& z)
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100 *iso : {x : HOD } → * ( & x ) ≡ x
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101 &iso : {x : Ordinal } → & ( * x ) ≡ x
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102 ==→o≡ : {x y : HOD } → (od x == od y) → x ≡ y
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103 sup-o : (A : HOD) → ( ( x : Ordinal ) → def (od A) x → Ordinal ) → Ordinal -- required in Replace
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104 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
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105 -- possible order restriction (required in the axiom of infinite )
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106 ho< : {x : HOD} → & x o< next (odmax x)
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107
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108
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109 postulate odAxiom : ODAxiom
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110 open ODAxiom odAxiom
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111
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112 -- odmax minimality
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113 --
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114 -- since we have ==→o≡ , so odmax have to be unique. We should have odmaxmin in HOD.
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115 -- We can calculate the minimum using sup but it is tedius.
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116 -- Only Select has non minimum odmax.
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117 -- We have the same problem on 'def' itself, but we leave it.
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118
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119 odmaxmin : Set (suc n)
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120 odmaxmin = (y : HOD) (z : Ordinal) → ((x : Ordinal)→ def (od y) x → x o< z) → odmax y o< osuc z
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121
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122 -- OD ⇔ Ordinal leads a contradiction, so we need bounded HOD
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123 ¬OD-order : ( & : OD → Ordinal ) → ( * : Ordinal → OD ) → ( { x y : OD } → def y ( & x ) → & x o< & y) → ⊥
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124 ¬OD-order & * c<→o< = o≤> <-osuc (c<→o< {Ords} (lift tt) )
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125
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126 -- Ordinal in OD ( and ZFSet ) Transitive Set
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127 Ord : ( a : Ordinal ) → HOD
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128 Ord a = record { od = record { def = λ y → y o< a } ; odmax = a ; <odmax = lemma } where
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129 lemma : {x : Ordinal} → x o< a → x o< a
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130 lemma {x} lt = lt
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131
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132 od∅ : HOD
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133 od∅ = Ord o∅
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134
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135 odef : HOD → Ordinal → Set n
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136 odef A x = def ( od A ) x
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137
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138 _∋_ : ( a x : HOD ) → Set n
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139 _∋_ a x = odef a ( & x )
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140
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141 -- _c<_ : ( x a : HOD ) → Set n
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142 -- x c< a = a ∋ x
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143
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144 d→∋ : ( a : HOD ) { x : Ordinal} → odef a x → a ∋ (* x)
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145 d→∋ a lt = subst (λ k → odef a k ) (sym &iso) lt
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146
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147 -- odef-subst : {Z : HOD } {X : Ordinal }{z : HOD } {x : Ordinal }→ odef Z X → Z ≡ z → X ≡ x → odef z x
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148 -- odef-subst df refl refl = df
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149
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150 otrans : {a x y : Ordinal } → odef (Ord a) x → odef (Ord x) y → odef (Ord a) y
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151 otrans x<a y<x = ordtrans y<x x<a
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152
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153 -- If we have reverse of c<→o<, everything becomes Ordinal
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154 ∈→c<→HOD=Ord : ( o<→c< : {x y : Ordinal } → x o< y → odef (* y) x ) → {x : HOD } → x ≡ Ord (& x)
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155 ∈→c<→HOD=Ord o<→c< {x} = ==→o≡ ( record { eq→ = lemma1 ; eq← = lemma2 } ) where
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156 lemma1 : {y : Ordinal} → odef x y → odef (Ord (& x)) y
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157 lemma1 {y} lt = subst ( λ k → k o< & x ) &iso (c<→o< {* y} {x} (d→∋ x lt))
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158 lemma2 : {y : Ordinal} → odef (Ord (& x)) y → odef x y
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159 lemma2 {y} lt = subst (λ k → odef k y ) *iso (o<→c< {y} {& x} lt )
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160
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161 -- avoiding lv != Zero error
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162 orefl : { x : HOD } → { y : Ordinal } → & x ≡ y → & x ≡ y
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163 orefl refl = refl
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164
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165 ==-iso : { x y : HOD } → od (* (& x)) == od (* (& y)) → od x == od y
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166 ==-iso {x} {y} eq = record {
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167 eq→ = λ {z} d → lemma ( eq→ eq (subst (λ k → odef k z ) (sym *iso) d )) ;
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168 eq← = λ {z} d → lemma ( eq← eq (subst (λ k → odef k z ) (sym *iso) d )) }
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169 where
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170 lemma : {x : HOD } {z : Ordinal } → odef (* (& x)) z → odef x z
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171 lemma {x} {z} d = subst (λ k → odef k z) (*iso) d
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172
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173 =-iso : {x y : HOD } → (od x == od y) ≡ (od (* (& x)) == od y)
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174 =-iso {_} {y} = cong ( λ k → od k == od y ) (sym *iso)
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175
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176 ord→== : { x y : HOD } → & x ≡ & y → od x == od y
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177 ord→== {x} {y} eq = ==-iso (lemma (& x) (& y) (orefl eq)) where
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178 lemma : ( ox oy : Ordinal ) → ox ≡ oy → od (* ox) == od (* oy)
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179 lemma ox ox refl = ==-refl
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180
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181 o≡→== : { x y : Ordinal } → x ≡ y → od (* x) == od (* y)
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182 o≡→== {x} {.x} refl = ==-refl
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183
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184 *≡*→≡ : { x y : Ordinal } → * x ≡ * y → x ≡ y
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185 *≡*→≡ eq = subst₂ (λ j k → j ≡ k ) &iso &iso ( cong (&) eq )
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186
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187 &≡&→≡ : { x y : HOD } → & x ≡ & y → x ≡ y
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188 &≡&→≡ eq = subst₂ (λ j k → j ≡ k ) *iso *iso ( cong (*) eq )
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189
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190 o∅≡od∅ : * (o∅ ) ≡ od∅
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191 o∅≡od∅ = ==→o≡ lemma where
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192 lemma0 : {x : Ordinal} → odef (* o∅) x → odef od∅ x
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193 lemma0 {x} lt with c<→o< {* x} {* o∅} (subst (λ k → odef (* o∅) k ) (sym &iso) lt)
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194 ... | t = subst₂ (λ j k → j o< k ) &iso &iso t
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195 lemma1 : {x : Ordinal} → odef od∅ x → odef (* o∅) x
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196 lemma1 {x} lt = ⊥-elim (¬x<0 lt)
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197 lemma : od (* o∅) == od od∅
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198 lemma = record { eq→ = lemma0 ; eq← = lemma1 }
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199
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200 ord-od∅ : & (od∅ ) ≡ o∅
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201 ord-od∅ = sym ( subst (λ k → k ≡ & (od∅ ) ) &iso (cong ( λ k → & k ) o∅≡od∅ ) )
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202
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203 ≡o∅→=od∅ : {x : HOD} → & x ≡ o∅ → od x == od od∅
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204 ≡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))))
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205 ; eq← = λ {y} lt → ⊥-elim ( ¬x<0 lt )}
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206
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207 =od∅→≡o∅ : {x : HOD} → od x == od od∅ → & x ≡ o∅
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208 =od∅→≡o∅ {x} eq = trans (cong (λ k → & k ) (==→o≡ {x} {od∅} eq)) ord-od∅
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209
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210 ≡od∅→=od∅ : {x : HOD} → x ≡ od∅ → od x == od od∅
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211 ≡od∅→=od∅ {x} eq = ≡o∅→=od∅ (subst (λ k → & x ≡ k ) ord-od∅ ( cong & eq ) )
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212
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213 ∅0 : record { def = λ x → Lift n ⊥ } == od od∅
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214 eq→ ∅0 {w} (lift ())
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215 eq← ∅0 {w} lt = lift (¬x<0 lt)
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216
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217 ∅< : { x y : HOD } → odef x (& y ) → ¬ ( od x == od od∅ )
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218 ∅< {x} {y} d eq with eq→ (==-trans eq (==-sym ∅0) ) d
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219 ∅< {x} {y} d eq | lift ()
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220
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221 0<P→ne : { x : HOD } → o∅ o< & x → ¬ ( od x == od od∅ )
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222 0<P→ne {x} 0<x eq = ⊥-elim ( o<¬≡ (sym (=od∅→≡o∅ eq)) 0<x )
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223
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224 ∈∅< : { x : HOD } {y : Ordinal } → odef x y → o∅ o< (& x)
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225 ∈∅< {x} {y} d with trio< o∅ (& x)
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226 ... | tri< a ¬b ¬c = a
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227 ... | tri≈ ¬a b ¬c = ⊥-elim ( ∅< {x} {* y} (subst (λ k → odef x k ) (sym &iso) d ) ( ≡o∅→=od∅ (sym b) ) )
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228 ... | tri> ¬a ¬b c = ⊥-elim ( ¬x<0 c )
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229
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230 ∅6 : { x : HOD } → ¬ ( x ∋ x ) -- no Russel paradox
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231 ∅6 {x} x∋x = o<¬≡ refl ( c<→o< {x} {x} x∋x )
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232
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233 odef-iso : {A B : HOD } {x y : Ordinal } → x ≡ y → (odef A y → odef B y) → odef A x → odef B x
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234 odef-iso refl t = t
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235
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236 is-o∅ : ( x : Ordinal ) → Dec ( x ≡ o∅ )
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237 is-o∅ x with trio< x o∅
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238 is-o∅ x | tri< a ¬b ¬c = no ¬b
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239 is-o∅ x | tri≈ ¬a b ¬c = yes b
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240 is-o∅ x | tri> ¬a ¬b c = no ¬b
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241
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242 odef< : {b : Ordinal } { A : HOD } → odef A b → b o< & A
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243 odef< {b} {A} ab = subst (λ k → k o< & A) &iso ( c<→o< (subst (λ k → odef A k ) (sym &iso ) ab))
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244
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245 odef∧< : {A : HOD } {y : Ordinal} {n : Level } → {P : Set n} → odef A y ∧ P → y o< & A
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246 odef∧< {A } {y} p = subst (λ k → k o< & A) &iso ( c<→o< (subst (λ k → odef A k ) (sym &iso ) (proj1 p )))
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247
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248 -- the pair
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249 _,_ : HOD → HOD → HOD
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250 x , y = record { od = record { def = λ t → (t ≡ & x ) ∨ ( t ≡ & y ) } ; odmax = omax (& x) (& y) ; <odmax = lemma } where
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251 lemma : {t : Ordinal} → (t ≡ & x) ∨ (t ≡ & y) → t o< omax (& x) (& y)
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252 lemma {t} (case1 refl) = omax-x _ _
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253 lemma {t} (case2 refl) = omax-y _ _
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254
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255 pair<y : {x y : HOD } → y ∋ x → & (x , x) o< osuc (& y)
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256 pair<y {x} {y} y∋x = ⊆→o≤ lemma where
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257 lemma : {z : Ordinal} → def (od (x , x)) z → def (od y) z
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258 lemma (case1 refl) = y∋x
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259 lemma (case2 refl) = y∋x
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260
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261 -- another possible restriction. We require no minimality on odmax, so it may arbitrary larger.
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262 odmax<& : { x y : HOD } → x ∋ y → Set n
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263 odmax<& {x} {y} x∋y = odmax x o< & x
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264
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265 in-codomain : (X : HOD ) → ( ψ : HOD → HOD ) → OD
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266 in-codomain X ψ = record { def = λ x → ¬ ( (y : Ordinal ) → ¬ ( odef X y ∧ ( x ≡ & (ψ (* y ))))) }
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267
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268 _∩_ : ( A B : HOD ) → HOD
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269 A ∩ B = record { od = record { def = λ x → odef A x ∧ odef B x }
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270 ; odmax = omin (odmax A) (odmax B) ; <odmax = λ y → min1 (<odmax A (proj1 y)) (<odmax B (proj2 y))}
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271
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272 _⊆_ : ( A B : HOD) → Set n
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273 _⊆_ A B = { x : Ordinal } → odef A x → odef B x
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274
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275 infixr 220 _⊆_
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276
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277 -- if we have & (x , x) ≡ osuc (& x), ⊆→o≤ → c<→o<
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278 ⊆→o≤→c<→o< : ({x : HOD} → & (x , x) ≡ osuc (& x) )
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279 → ({y z : HOD } → ({x : Ordinal} → def (od y) x → def (od z) x ) → & y o< osuc (& z) )
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280 → {x y : HOD } → def (od y) ( & x ) → & x o< & y
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431
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281 ⊆→o≤→c<→o< peq ⊆→o≤ {x} {y} y∋x with trio< (& x) (& y)
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282 ⊆→o≤→c<→o< peq ⊆→o≤ {x} {y} y∋x | tri< a ¬b ¬c = a
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283 ⊆→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 )))
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284 ⊆→o≤→c<→o< peq ⊆→o≤ {x} {y} y∋x | tri> ¬a ¬b c =
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285 ⊥-elim ( o<> (⊆→o≤ {x , x} {y} y⊆x,x ) lemma1 ) where
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286 lemma : {z : Ordinal} → (z ≡ & x) ∨ (z ≡ & x) → & x ≡ z
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287 lemma (case1 refl) = refl
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288 lemma (case2 refl) = refl
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289 y⊆x,x : {z : Ordinal} → def (od (x , x)) z → def (od y) z
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1091
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290 y⊆x,x {z} lt = subst (λ k → def (od y) k ) (lemma lt) y∋x
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431
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291 lemma1 : osuc (& y) o< & (x , x)
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1091
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292 lemma1 = subst (λ k → osuc (& y) o< k ) (sym (peq {x})) (osucc c )
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431
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293
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294 ε-induction : { ψ : HOD → Set (suc n)}
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295 → ( {x : HOD } → ({ y : HOD } → x ∋ y → ψ y ) → ψ x )
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296 → (x : HOD ) → ψ x
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297 ε-induction {ψ} ind x = subst (λ k → ψ k ) *iso (ε-induction-ord (osuc (& x)) <-osuc ) where
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298 induction : (ox : Ordinal) → ((oy : Ordinal) → oy o< ox → ψ (* oy)) → ψ (* ox)
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1091
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299 induction ox prev = ind ( λ {y} lt → subst (λ k → ψ k ) *iso (prev (& y) (o<-subst (c<→o< lt) refl &iso )))
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431
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300 ε-induction-ord : (ox : Ordinal) { oy : Ordinal } → oy o< ox → ψ (* oy)
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301 ε-induction-ord ox {oy} lt = TransFinite {λ oy → ψ (* oy)} induction oy
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302
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1109
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303 ε-induction0 : { ψ : HOD → Set n}
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304 → ( {x : HOD } → ({ y : HOD } → x ∋ y → ψ y ) → ψ x )
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305 → (x : HOD ) → ψ x
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306 ε-induction0 {ψ} ind x = subst (λ k → ψ k ) *iso (ε-induction-ord (osuc (& x)) <-osuc ) where
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307 induction : (ox : Ordinal) → ((oy : Ordinal) → oy o< ox → ψ (* oy)) → ψ (* ox)
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308 induction ox prev = ind ( λ {y} lt → subst (λ k → ψ k ) *iso (prev (& y) (o<-subst (c<→o< lt) refl &iso )))
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309 ε-induction-ord : (ox : Ordinal) { oy : Ordinal } → oy o< ox → ψ (* oy)
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310 ε-induction-ord ox {oy} lt = inOrdinal.TransFinite0 O {λ oy → ψ (* oy)} induction oy
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311
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1091
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312 -- Open supreme upper bound leads a contradition, so we use domain restriction on sup
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313 ¬open-sup : ( sup-o : (Ordinal → Ordinal ) → Ordinal) → ((ψ : Ordinal → Ordinal ) → (x : Ordinal) → ψ x o< sup-o ψ ) → ⊥
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314 ¬open-sup sup-o sup-o< = o<> <-osuc (sup-o< next-ord (sup-o next-ord)) where
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315 next-ord : Ordinal → Ordinal
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316 next-ord x = osuc x
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317
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318 Select : (X : HOD ) → ((x : HOD ) → Set n ) → HOD
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431
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319 Select X ψ = record { od = record { def = λ x → ( odef X x ∧ ψ ( * x )) } ; odmax = odmax X ; <odmax = λ y → <odmax X (proj1 y) }
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320
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1095
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321 _=h=_ : (x y : HOD) → Set n
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322 x =h= y = od x == od y
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323
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324 record Own (A : HOD) (x : Ordinal) : Set n where
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325 field
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326 owner : Ordinal
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327 ao : odef A owner
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328 ox : odef (* owner) x
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329
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330 Union : HOD → HOD
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331 Union U = record { od = record { def = λ x → Own U x } ; odmax = osuc (& U) ; <odmax = umax } where
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332 umax : {y : Ordinal} → Own U y → y o< osuc (& U)
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333 umax {y} uy = o<→≤ ( ordtrans (odef< (Own.ox uy)) (subst (λ k → k o< & U) (sym &iso) umax1) ) where
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334 umax1 : Own.owner uy o< & U
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335 umax1 = odef< (Own.ao uy)
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336
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337 union→ : (X z u : HOD) → (X ∋ u) ∧ (u ∋ z) → Union X ∋ z
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338 union→ X z u xx = record { owner = & u ; ao = proj1 xx ; ox = subst (λ k → odef k (& z)) (sym *iso) (proj2 xx) }
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339 union← : (X z : HOD) (X∋z : Union X ∋ z) → ¬ ( (u : HOD ) → ¬ ((X ∋ u) ∧ (u ∋ z )))
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340 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 ⟫ )
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341
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342 record Replaced (A : HOD) (ψ : Ordinal → Ordinal ) (x : Ordinal ) : Set n where
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343 field
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344 z : Ordinal
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345 az : odef A z
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346 x=ψz : x ≡ ψ z
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347
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1091
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348 Replace : HOD → (HOD → HOD) → HOD
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1095
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349 Replace X ψ = record { od = record { def = λ x → Replaced X (λ z → & (ψ (* z))) x } ; odmax = rmax ; <odmax = rmax< } where
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431
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350 rmax : Ordinal
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1095
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351 rmax = osuc ( sup-o X (λ y X∋y → & (ψ (* y) )) )
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352 rmax< : {y : Ordinal} → Replaced X (λ z → & (ψ (* z))) y → y o< rmax
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353 rmax< {y} lt = subst (λ k → k o< rmax) r01 ( sup-o≤ X (Replaced.az lt) ) where
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354 r01 : & (ψ ( * (Replaced.z lt ) )) ≡ y
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355 r01 = sym (Replaced.x=ψz lt )
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356
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357 replacement← : {ψ : HOD → HOD} (X x : HOD) → X ∋ x → Replace X ψ ∋ ψ x
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358 replacement← {ψ} X x lt = record { z = & x ; az = lt ; x=ψz = cong (λ k → & (ψ k)) (sym *iso) }
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359 replacement→ : {ψ : HOD → HOD} (X x : HOD) → (lt : Replace X ψ ∋ x) → ¬ ( (y : HOD) → ¬ (x =h= ψ y))
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360 replacement→ {ψ} X x lt eq = eq (* (Replaced.z lt)) (ord→== (Replaced.x=ψz lt))
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431
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361
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362 --
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1091
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363 -- If we have LEM, Replace' is equivalent to Replace
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431
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364 --
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1095
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365
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366 record Replaced1 (A : HOD) (ψ : (x : Ordinal ) → odef A x → Ordinal ) (x : Ordinal ) : Set n where
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367 field
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368 z : Ordinal
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369 az : odef A z
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370 x=ψz : x ≡ ψ z az
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431
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371
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1095
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372 Replace' : (X : HOD) → ((x : HOD) → X ∋ x → HOD) → HOD
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373 Replace' X ψ = record { od = record { def = λ x → Replaced1 X (λ z xz → & (ψ (* z) (subst (λ k → odef X k) (sym &iso) xz) )) x } ; odmax = rmax ; <odmax = rmax< } where
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374 rmax : Ordinal
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375 rmax = osuc ( sup-o X (λ y X∋y → & (ψ (* y) (d→∋ X X∋y) )) )
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376 rmax< : {y : Ordinal} → Replaced1 X (λ z xz → & (ψ (* z) (subst (λ k → odef X k) (sym &iso) xz) )) y → y o< rmax
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377 rmax< {y} lt = subst (λ k → k o< rmax) r01 ( sup-o≤ X (Replaced1.az lt) ) where
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378 r01 : & (ψ ( * (Replaced1.z lt ) ) (subst (λ k → odef X k) (sym &iso) (Replaced1.az lt) )) ≡ y
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379 r01 = sym (Replaced1.x=ψz lt )
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380
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381 -- replacement←1 : {ψ : HOD → HOD} (X x : HOD) → X ∋ x → Replace1 X ψ ∋ ψ x
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382 -- replacement←1 {ψ} X x lt = record { z = & x ; az = lt ; x=ψz = cong (λ k → & (ψ k)) (sym *iso) }
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383 -- replacement→1 : {ψ : HOD → HOD} (X x : HOD) → (lt : Replace1 X ψ ∋ x) → ¬ ( (y : HOD) → ¬ (x =h= ψ y))
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384 -- replacement→1 {ψ} X x lt eq = eq (* (Replaced.z lt)) (ord→== (Replaced.x=ψz lt))
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385
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431
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386 _∈_ : ( A B : HOD ) → Set n
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387 A ∈ B = B ∋ A
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388
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1095
|
389 Power : HOD → HOD
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390 Power A = record { od = record { def = λ x → ( ( z : Ordinal) → odef (* x) z → odef A z ) } ; odmax = osuc (& A)
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391 ; <odmax = p00 } where
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392 p00 : {y : Ordinal} → ((z : Ordinal) → odef (* y) z → odef A z) → y o< osuc (& A)
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393 p00 {y} y⊆A = p01 where
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394 p01 : y o≤ & A
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395 p01 = subst (λ k → k o≤ & A) &iso ( ⊆→o≤ (λ {x} yx → y⊆A x yx ))
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431
|
396
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1095
|
397 power→ : ( A t : HOD) → Power A ∋ t → {x : HOD} → t ∋ x → A ∋ x
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398 power→ A t P∋t {x} t∋x = P∋t (& x) (subst (λ k → odef k (& x) ) (sym *iso) t∋x )
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399
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400 power← : (A t : HOD) → ({x : HOD} → (t ∋ x → A ∋ x)) → Power A ∋ t
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401 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 ))
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402
|
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1180
|
403 Intersection : (X : HOD ) → HOD -- ∩ X
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404 Intersection X = record { od = record { def = λ x → (x o< & X ) ∧ ( {y : Ordinal} → odef X y → odef (* y) x )} ; odmax = & X ; <odmax = λ lt → proj1 lt }
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405
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406
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431
|
407 -- ｛_｝ : ZFSet → ZFSet
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408 -- ｛ x ｝ = ( x , x ) -- better to use (x , x) directly
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409
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410
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411 data infinite-d : ( x : Ordinal ) → Set n where
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412 iφ : infinite-d o∅
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413 isuc : {x : Ordinal } → infinite-d x →
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414 infinite-d (& ( Union (* x , (* x , * x ) ) ))
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415
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416 -- ω can be diverged in our case, since we have no restriction on the corresponding ordinal of a pair.
|
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417 -- We simply assumes infinite-d y has a maximum.
|
|
1091
|
418 --
|
|
431
|
419 -- This means that many of OD may not be HODs because of the & mapping divergence.
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420 -- We should have some axioms to prevent this such as & x o< next (odmax x).
|
|
1091
|
421 --
|
|
1097
|
422 -- Since we have Ord (next o∅), we don't need this, but ZF axiom requires this and ho<
|
|
431
|
423
|
|
1091
|
424 infinite : HOD
|
|
431
|
425 infinite = record { od = record { def = λ x → infinite-d x } ; odmax = next o∅ ; <odmax = lemma } where
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|
426 u : (y : Ordinal ) → HOD
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|
427 u y = Union (* y , (* y , * y))
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428 -- next< : {x y z : Ordinal} → x o< next z → y o< next x → y o< next z
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429 lemma8 : {y : Ordinal} → & (* y , * y) o< next (odmax (* y , * y))
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|
430 lemma8 = ho<
|
|
1091
|
431 --- (x,y) < next (omax x y) < next (osuc y) = next y
|
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431
|
432 lemmaa : {x y : HOD} → & x o< & y → & (x , y) o< next (& y)
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433 lemmaa {x} {y} x<y = subst (λ k → & (x , y) o< k ) (sym nexto≡) (subst (λ k → & (x , y) o< next k ) (sym (omax< _ _ x<y)) ho< )
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434 lemma81 : {y : Ordinal} → & (* y , * y) o< next (& (* y))
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435 lemma81 {y} = nexto=n (subst (λ k → & (* y , * y) o< k ) (cong (λ k → next k) (omxx _)) lemma8)
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436 lemma9 : {y : Ordinal} → & (* y , (* y , * y)) o< next (& (* y , * y))
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|
437 lemma9 = lemmaa (c<→o< (case1 refl))
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|
438 lemma71 : {y : Ordinal} → & (* y , (* y , * y)) o< next (& (* y))
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|
439 lemma71 = next< lemma81 lemma9
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|
440 lemma1 : {y : Ordinal} → & (u y) o< next (osuc (& (* y , (* y , * y))))
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441 lemma1 = ho<
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442 --- main recursion
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443 lemma : {y : Ordinal} → infinite-d y → y o< next o∅
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444 lemma {o∅} iφ = x<nx
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445 lemma (isuc {y} x) = next< (lemma x) (next< (subst (λ k → & (* y , (* y , * y)) o< next k) &iso lemma71 ) (nexto=n lemma1))
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446
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447 empty : (x : HOD ) → ¬ (od∅ ∋ x)
|
|
1091
|
448 empty x = ¬x<0
|
|
431
|
449
|
|
1091
|
450 pair→ : ( x y t : HOD ) → (x , y) ∋ t → ( t =h= x ) ∨ ( t =h= y )
|
|
431
|
451 pair→ x y t (case1 t≡x ) = case1 (subst₂ (λ j k → j =h= k ) *iso *iso (o≡→== t≡x ))
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452 pair→ x y t (case2 t≡y ) = case2 (subst₂ (λ j k → j =h= k ) *iso *iso (o≡→== t≡y ))
|
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453
|
|
1091
|
454 pair← : ( x y t : HOD ) → ( t =h= x ) ∨ ( t =h= y ) → (x , y) ∋ t
|
|
431
|
455 pair← x y t (case1 t=h=x) = case1 (cong (λ k → & k ) (==→o≡ t=h=x))
|
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|
456 pair← x y t (case2 t=h=y) = case2 (cong (λ k → & k ) (==→o≡ t=h=y))
|
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457
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1091
|
458 o<→c< : {x y : Ordinal } → x o< y → (Ord x) ⊆ (Ord y)
|
|
1096
|
459 o<→c< lt {z} ox = ordtrans ox lt
|
|
431
|
460
|
|
|
461 ⊆→o< : {x y : Ordinal } → (Ord x) ⊆ (Ord y) → x o< osuc y
|
|
1091
|
462 ⊆→o< {x} {y} lt with trio< x y
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|
431
|
463 ⊆→o< {x} {y} lt | tri< a ¬b ¬c = ordtrans a <-osuc
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464 ⊆→o< {x} {y} lt | tri≈ ¬a b ¬c = subst ( λ k → k o< osuc y) (sym b) <-osuc
|
|
1096
|
465 ⊆→o< {x} {y} lt | tri> ¬a ¬b c with lt (o<-subst c (sym &iso) refl )
|
|
431
|
466 ... | ttt = ⊥-elim ( o<¬≡ refl (o<-subst ttt &iso refl ))
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467
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468 ψiso : {ψ : HOD → Set n} {x y : HOD } → ψ x → x ≡ y → ψ y
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469 ψiso {ψ} t refl = t
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470 selection : {ψ : HOD → Set n} {X y : HOD} → ((X ∋ y) ∧ ψ y) ⇔ (Select X ψ ∋ y)
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|
471 selection {ψ} {X} {y} = ⟪
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|
472 ( λ cond → ⟪ proj1 cond , ψiso {ψ} (proj2 cond) (sym *iso) ⟫ )
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473 , ( λ select → ⟪ proj1 select , ψiso {ψ} (proj2 select) *iso ⟫ )
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474 ⟫
|
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|
475
|
|
1091
|
476 selection-in-domain : {ψ : HOD → Set n} {X y : HOD} → Select X ψ ∋ y → X ∋ y
|
|
431
|
477 selection-in-domain {ψ} {X} {y} lt = proj1 ((proj2 (selection {ψ} {X} )) lt)
|
|
|
478
|
|
1007
|
479 sup-c≤ : (ψ : HOD → HOD) → {X x : HOD} → X ∋ x → & (ψ x) o≤ (sup-o X (λ y X∋y → & (ψ (* y))))
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480 sup-c≤ ψ {X} {x} lt = subst (λ k → & (ψ k) o< _ ) *iso (sup-o≤ X lt )
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481
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431
|
482 ---
|
|
|
483 --- Power Set
|
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484 ---
|
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|
485 --- First consider ordinals in HOD
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486 ---
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487 --- A ∩ x = record { def = λ y → odef A y ∧ odef x y } subset of A
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488 --
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489 --
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490 ∩-≡ : { a b : HOD } → ({x : HOD } → (a ∋ x → b ∋ x)) → a =h= ( b ∩ a )
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491 ∩-≡ {a} {b} inc = record {
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492 eq→ = λ {x} x<a → ⟪ (subst (λ k → odef b k ) &iso (inc (d→∋ a x<a))) , x<a ⟫ ;
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493 eq← = λ {x} x<a∩b → proj2 x<a∩b }
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494
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495 extensionality0 : {A B : HOD } → ((z : HOD) → (A ∋ z) ⇔ (B ∋ z)) → A =h= B
|
|
1091
|
496 eq→ (extensionality0 {A} {B} eq ) {x} d = odef-iso {A} {B} (sym &iso) (proj1 (eq (* x))) d
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497 eq← (extensionality0 {A} {B} eq ) {x} d = odef-iso {B} {A} (sym &iso) (proj2 (eq (* x))) d
|
|
431
|
498
|
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|
499 extensionality : {A B w : HOD } → ((z : HOD ) → (A ∋ z) ⇔ (B ∋ z)) → (w ∋ A) ⇔ (w ∋ B)
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500 proj1 (extensionality {A} {B} {w} eq ) d = subst (λ k → w ∋ k) ( ==→o≡ (extensionality0 {A} {B} eq) ) d
|
|
1091
|
501 proj2 (extensionality {A} {B} {w} eq ) d = subst (λ k → w ∋ k) (sym ( ==→o≡ (extensionality0 {A} {B} eq) )) d
|
|
431
|
502
|
|
1091
|
503 infinity∅ : infinite ∋ od∅
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|
504 infinity∅ = subst (λ k → odef infinite k ) lemma iφ where
|
|
431
|
505 lemma : o∅ ≡ & od∅
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506 lemma = let open ≡-Reasoning in begin
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507 o∅
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508 ≡⟨ sym &iso ⟩
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509 & ( * o∅ )
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510 ≡⟨ cong ( λ k → & k ) o∅≡od∅ ⟩
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511 & od∅
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512 ∎
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513 infinity : (x : HOD) → infinite ∋ x → infinite ∋ Union (x , (x , x ))
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|
514 infinity x lt = subst (λ k → odef infinite k ) lemma (isuc {& x} lt) where
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|
515 lemma : & (Union (* (& x) , (* (& x) , * (& x))))
|
|
|
516 ≡ & (Union (x , (x , x)))
|
|
1091
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517 lemma = cong (λ k → & (Union ( k , ( k , k ) ))) *iso
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431
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518
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519 isZF : IsZF (HOD ) _∋_ _=h=_ od∅ _,_ Union Power Select Replace infinite
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520 isZF = record {
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521 isEquivalence = record { refl = ==-refl ; sym = ==-sym; trans = ==-trans }
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522 ; pair→ = pair→
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523 ; pair← = pair←
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524 ; union→ = union→
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525 ; union← = union←
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526 ; empty = empty
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1091
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527 ; power→ = power→
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528 ; power← = power←
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529 ; extensionality = λ {A} {B} {w} → extensionality {A} {B} {w}
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431
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530 ; ε-induction = ε-induction
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531 ; infinity∅ = infinity∅
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532 ; infinity = infinity
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533 ; selection = λ {X} {ψ} {y} → selection {X} {ψ} {y}
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534 ; replacement← = replacement←
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535 ; replacement→ = λ {ψ} → replacement→ {ψ}
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1091
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536 }
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431
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537
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1091
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538 HOD→ZF : ZF
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539 HOD→ZF = record {
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540 ZFSet = HOD
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541 ; _∋_ = _∋_
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542 ; _≈_ = _=h=_
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431
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543 ; ∅ = od∅
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544 ; _,_ = _,_
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545 ; Union = Union
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546 ; Power = Power
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547 ; Select = Select
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548 ; Replace = Replace
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549 ; infinite = infinite
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1091
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550 ; isZF = isZF
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551 }
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431
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552
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1091
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553
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