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