Mercurial > hg > Members > kono > Proof > ZF-in-agda
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author | Shinji KONO <kono@ie.u-ryukyu.ac.jp> |
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date | Sat, 23 Apr 2022 18:35:20 +0900 |
parents | c9f80aea598e |
children | c43375ade2c5 |
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{-# OPTIONS --allow-unsolved-metas #-} open import Level hiding ( suc ; zero ) open import Ordinals import OD module zorn {n : Level } (O : Ordinals {n}) (_<_ : (x y : OD.HOD O ) → Set n ) where open import zf open import logic -- open import partfunc {n} O open import Relation.Nullary open import Relation.Binary open import Data.Empty open import Relation.Binary open import Relation.Binary.Core open import Relation.Binary.PropositionalEquality import BAlgbra open inOrdinal O open OD O open OD.OD open ODAxiom odAxiom import OrdUtil import ODUtil open Ordinals.Ordinals O open Ordinals.IsOrdinals isOrdinal open Ordinals.IsNext isNext open OrdUtil O open ODUtil O import ODC open _∧_ open _∨_ open Bool open HOD _≤_ : (x y : HOD) → Set (Level.suc n) x ≤ y = ( x ≡ y ) ∨ ( x < y ) record Element (A : HOD) : Set (Level.suc n) where field elm : HOD is-elm : A ∋ elm open Element _<A_ : {A : HOD} → (x y : Element A ) → Set n x <A y = elm x < elm y _≡A_ : {A : HOD} → (x y : Element A ) → Set (Level.suc n) x ≡A y = elm x ≡ elm y IsPartialOrderSet : ( A : HOD ) → Set (Level.suc n) IsPartialOrderSet A = IsStrictPartialOrder (_≡A_ {A}) _<A_ open _==_ open _⊆_ isA : { A B : HOD } → B ⊆ A → (x : Element B) → Element A isA B⊆A x = record { elm = elm x ; is-elm = incl B⊆A (is-elm x) } ⊆-IsPartialOrderSet : { A B : HOD } → B ⊆ A → IsPartialOrderSet A → IsPartialOrderSet B ⊆-IsPartialOrderSet {A} {B} B⊆A PA = record { isEquivalence = record { refl = refl ; sym = sym ; trans = trans } ; trans = λ {x} {y} {z} → trans1 {x} {y} {z} ; irrefl = λ {x} {y} → irrefl1 {x} {y} ; <-resp-≈ = resp0 } where _<B_ : (x y : Element B ) → Set n x <B y = elm x < elm y trans1 : {x y z : Element B} → x <B y → y <B z → x <B z trans1 {x} {y} {z} x<y y<z = IsStrictPartialOrder.trans PA {isA B⊆A x} {isA B⊆A y} {isA B⊆A z} x<y y<z irrefl1 : {x y : Element B} → elm x ≡ elm y → ¬ ( x <B y ) irrefl1 {x} {y} x=y x<y = IsStrictPartialOrder.irrefl PA {isA B⊆A x} {isA B⊆A y} x=y x<y open import Data.Product resp0 : ({x y z : Element B} → elm y ≡ elm z → x <B y → x <B z) × ({x y z : Element B} → elm y ≡ elm z → y <B x → z <B x) resp0 = Data.Product._,_ (λ {x} {y} {z} → proj₁ (IsStrictPartialOrder.<-resp-≈ PA) {isA B⊆A x } {isA B⊆A y }{isA B⊆A z }) (λ {x} {y} {z} → proj₂ (IsStrictPartialOrder.<-resp-≈ PA) {isA B⊆A x } {isA B⊆A y }{isA B⊆A z }) -- open import Relation.Binary.Properties.Poset as Poset IsTotalOrderSet : ( A : HOD ) → Set (Level.suc n) IsTotalOrderSet A = IsStrictTotalOrder (_≡A_ {A}) _<A_ me : { A a : HOD } → A ∋ a → Element A me {A} {a} lt = record { elm = a ; is-elm = lt } A∋x-irr : (A : HOD) {x y : HOD} → x ≡ y → (A ∋ x) ≡ (A ∋ y ) A∋x-irr A {x} {y} refl = refl me-elm-refl : (A : HOD) → (x : Element A) → elm (me {A} (d→∋ A (is-elm x))) ≡ elm x me-elm-refl A record { elm = ex ; is-elm = ax } = *iso open import Relation.Binary.HeterogeneousEquality as HE using (_≅_ ) -- Don't use Element other than Order, you'll be in a trouble -- postulate -- may be proved by transfinite induction and functional extentionality -- ∋x-irr : (A : HOD) {x y : HOD} → x ≡ y → (ax : A ∋ x) (ay : A ∋ y ) → ax ≅ ay -- odef-irr : (A : OD) {x y : Ordinal} → x ≡ y → (ax : def A x) (ay : def A y ) → ax ≅ ay -- is-elm-irr : (A : HOD) → {x y : Element A } → elm x ≡ elm y → is-elm x ≅ is-elm y -- is-elm-irr A {x} {y} eq = ∋x-irr A eq (is-elm x) (is-elm y ) El-irr2 : (A : HOD) → {x y : Element A } → elm x ≡ elm y → is-elm x ≅ is-elm y → x ≡ y El-irr2 A {x} {y} refl HE.refl = refl -- El-irr : {A : HOD} → {x y : Element A } → elm x ≡ elm y → x ≡ y -- El-irr {A} {x} {y} eq = El-irr2 A eq ( is-elm-irr A eq ) record _Set≈_ (A B : Ordinal ) : Set n where field fun← : {x : Ordinal } → odef (* A) x → Ordinal fun→ : {x : Ordinal } → odef (* B) x → Ordinal funB : {x : Ordinal } → ( lt : odef (* A) x ) → odef (* B) ( fun← lt ) funA : {x : Ordinal } → ( lt : odef (* B) x ) → odef (* A) ( fun→ lt ) fiso← : {x : Ordinal } → ( lt : odef (* B) x ) → fun← ( funA lt ) ≡ x fiso→ : {x : Ordinal } → ( lt : odef (* A) x ) → fun→ ( funB lt ) ≡ x open _Set≈_ record _OS≈_ {A B : HOD} (TA : IsTotalOrderSet A ) (TB : IsTotalOrderSet B ) : Set (Level.suc n) where field iso : (& A ) Set≈ (& B) fmap : {x y : Ordinal} → (ax : odef A x) → (ay : odef A y) → * x < * y → * (fun← iso (subst (λ k → odef k x) (sym *iso) ax)) < * (fun← iso (subst (λ k → odef k y) (sym *iso) ay)) Cut< : ( A x : HOD ) → HOD Cut< A x = record { od = record { def = λ y → ( odef A y ) ∧ ( x < * y ) } ; odmax = & A ; <odmax = λ lt → subst (λ k → k o< & A) &iso (c<→o< (subst (λ k → odef A k ) (sym &iso) (proj1 lt))) } Cut<T : {A : HOD} → (TA : IsTotalOrderSet A ) ( x : HOD )→ IsTotalOrderSet ( Cut< A x ) Cut<T {A} TA x = record { isEquivalence = record { refl = refl ; trans = trans ; sym = sym } ; trans = λ {x} {y} {z} → IsStrictTotalOrder.trans TA {me (proj1 (is-elm x))} {me (proj1 (is-elm y))} {me (proj1 (is-elm z))} ; compare = λ x y → IsStrictTotalOrder.compare TA (me (proj1 (is-elm x))) (me (proj1 (is-elm y))) } record _OS<_ {A B : HOD} (TA : IsTotalOrderSet A ) (TB : IsTotalOrderSet B ) : Set (Level.suc n) where field x : HOD iso : TA OS≈ (Cut<T TA x) -- OS<-cmp : {x : HOD} → Trichotomous {_} {IsTotalOrderSet x} _OS≈_ _OS<_ -- OS<-cmp A B = {!!} -- tree structure data IChain (A : HOD) : Ordinal → Set n where ifirst : {ox : Ordinal} → odef A ox → IChain A ox inext : {ox oy : Ordinal} → odef A oy → * ox < * oy → IChain A ox → IChain A oy -- * ox < .. < * oy ic-connect : {A : HOD} {oy : Ordinal} → (ox : Ordinal) → (iy : IChain A oy) → Set n ic-connect {A} ox (ifirst {oy} ay) = Lift n ⊥ ic-connect {A} ox (inext {oy} {oz} ay y<z iz) = (ox ≡ oy) ∨ ic-connect ox iz ic→odef : {A : HOD} {ox : Ordinal} → IChain A ox → odef A ox ic→odef {A} {ox} (ifirst ax) = ax ic→odef {A} {ox} (inext ax x<y ic) = ax ic→< : {A : HOD} → IsPartialOrderSet A → (x : Ordinal) → odef A x → {y : Ordinal} → (iy : IChain A y) → ic-connect {A} {y} x iy → * x < * y ic→< {A} PO x ax {y} (ifirst ay) () ic→< {A} PO x ax {y} (inext ay x<y iy) (case1 refl) = x<y ic→< {A} PO x ax {y} (inext {oy} ay x<y iy) (case2 ic) = IsStrictPartialOrder.trans PO {me (subst (λ k → odef A k) (sym &iso) ax )} {me (subst (λ k → odef A k) (sym &iso) (ic→odef {A} {oy} iy) ) } {me (subst (λ k → odef A k) (sym &iso) ay) } (ic→< {A} PO x ax iy ic ) x<y record IChained (A : HOD) (x y : Ordinal) : Set n where field iy : IChain A y ic : ic-connect x iy -- -- all tree from x -- IChainSet : (A : HOD) {x : Ordinal} → odef A x → HOD IChainSet A {x} ax = record { od = record { def = λ y → odef A y ∧ IChained A x y } ; odmax = & A ; <odmax = λ {y} lt → subst (λ k → k o< & A) &iso (c<→o< (subst (λ k → odef A k) (sym &iso) (proj1 lt))) } IChainSet⊆A : {A : HOD} → {x : Ordinal } → (ax : odef A x ) → IChainSet A ax ⊆ A IChainSet⊆A {A} x = record { incl = λ {oy} y → proj1 y } ¬IChained-refl : (A : HOD) {x : Ordinal} → IsPartialOrderSet A → ¬ IChained A x x ¬IChained-refl A {x} PO record { iy = iy ; ic = ic } = IsStrictPartialOrder.irrefl PO {me (subst (λ k → odef A k ) (sym &iso) ic0) } {me (subst (λ k → odef A k ) (sym &iso) ic0) } refl (ic→< {A} PO x ic0 iy ic ) where ic0 : odef A x ic0 = ic→odef {A} iy -- there is a y, & y > & x record OSup> (A : HOD) {x : Ordinal} (ax : A ∋ * x) : Set n where field y : Ordinal icy : odef (IChainSet A ax ) y y>x : x o< y record IChainSup> (A : HOD) {x : Ordinal} (ax : A ∋ * x) : Set n where field y : Ordinal A∋y : odef A y y>x : * x < * y -- finite IChain -- -- tree structured ic→A∋y : (A : HOD) {x y : Ordinal} (ax : A ∋ * x) → odef (IChainSet A ax) y → A ∋ * y ic→A∋y A {x} {y} ax ⟪ ay , _ ⟫ = subst (λ k → odef A k) (sym &iso) ay record InfiniteChain (A : HOD) (max : Ordinal) {x : Ordinal} (ax : A ∋ * x) : Set n where field chain<x : (y : Ordinal ) → odef (IChainSet A ax) y → y o< max c-infinite : (y : Ordinal ) → (cy : odef (IChainSet A ax) y ) → IChainSup> A (ic→A∋y A ax cy) open import Data.Nat hiding (_<_ ; _≤_ ) import Data.Nat.Properties as NP open import nat data Chain (A : HOD) (s : Ordinal) (next : Ordinal → Ordinal ) : ( x : Ordinal ) → Set n where cfirst : odef A s → Chain A s next s csuc : (x : Ordinal ) → (ax : odef A x ) → Chain A s next x → odef A (next x) → Chain A s next (next x ) ct∈A : (A : HOD ) (s : Ordinal) → (next : Ordinal → Ordinal ) → {x : Ordinal} → Chain A s next x → odef A x ct∈A A s next {x} (cfirst x₁) = x₁ ct∈A A s next {.(next x )} (csuc x ax t anx) = anx -- -- extract single chain from countable infinite chains -- TransitiveClosure : (A : HOD) (s : Ordinal) → (next : Ordinal → Ordinal ) → HOD TransitiveClosure A s next = record { od = record { def = λ x → Chain A s next x } ; odmax = & A ; <odmax = cc01 } where cc01 : {y : Ordinal} → Chain A s next y → y o< & A cc01 {y} cy = subst (λ k → k o< & A ) &iso ( c<→o< (subst (λ k → odef A k ) (sym &iso) ( ct∈A A s next cy ) ) ) cton0 : (A : HOD ) (s : Ordinal) → (next : Ordinal → Ordinal ) {y : Ordinal } → Chain A s next y → ℕ cton0 A s next (cfirst _) = zero cton0 A s next (csuc x ax z _) = suc (cton0 A s next z) cton : (A : HOD ) (s : Ordinal) → (next : Ordinal → Ordinal ) → Element (TransitiveClosure A s next) → ℕ cton A s next y = cton0 A s next (is-elm y) cinext : (A : HOD) {x max : Ordinal } → (ax : A ∋ * x ) → (ifc : InfiniteChain A max ax ) → Ordinal → Ordinal cinext A ax ifc y with ODC.∋-p O (IChainSet A ax) (* y) ... | yes ics-y = IChainSup>.y ( InfiniteChain.c-infinite ifc y (subst (λ k → odef (IChainSet A ax) k) &iso ics-y )) ... | no _ = o∅ InFCSet : (A : HOD) → {x max : Ordinal} (ax : A ∋ * x) → (ifc : InfiniteChain A max ax ) → HOD InFCSet A {x} ax ifc = TransitiveClosure (IChainSet A ax) x (cinext A ax ifc ) InFCSet⊆A : (A : HOD) → {x max : Ordinal} (ax : A ∋ * x) → (ifc : InfiniteChain A max ax ) → InFCSet A ax ifc ⊆ A InFCSet⊆A A {x} ax ifc = record { incl = λ {y} lt → incl (IChainSet⊆A ax) ( ct∈A (IChainSet A ax) x (cinext A ax ifc) lt ) } cinext→IChainSup : (A : HOD) {x max : Ordinal } → (ax : A ∋ * x ) → (ifc : InfiniteChain A max ax ) → (y : Ordinal ) → (ay1 : IChainSet A ax ∋ * y ) → IChainSup> A (subst (odef A) (sym &iso) (proj1 (subst (λ k → odef (IChainSet A ax) k) &iso ay1))) cinext→IChainSup A {x} ax ifc y ay with ODC.∋-p O (IChainSet A ax) (* y) ... | no not = ⊥-elim ( not ay ) ... | yes ay1 = InfiniteChain.c-infinite ifc y (subst (λ k → odef (IChainSet A ax) k) &iso ay ) TransitiveClosure-is-total : (A : HOD) → {x max : Ordinal} (ax : A ∋ * x) → IsPartialOrderSet A → (ifc : InfiniteChain A max ax ) → IsTotalOrderSet ( InFCSet A ax ifc ) TransitiveClosure-is-total A {x} ax PO ifc = record { isEquivalence = IsStrictPartialOrder.isEquivalence IPO ; trans = λ {x} {y} {z} → IsStrictPartialOrder.trans IPO {x} {y} {z} ; compare = cmp } where IPO : IsPartialOrderSet (InFCSet A ax ifc ) IPO = ⊆-IsPartialOrderSet record { incl = λ {y} lt → incl (InFCSet⊆A A {x} ax ifc) lt} PO B = IChainSet A ax cnext = cinext A ax ifc ct02 : {oy : Ordinal} → (y : Chain B x cnext oy ) → A ∋ * oy ct02 y = incl (IChainSet⊆A {A} ax) (subst (λ k → odef (IChainSet A ax) k) (sym &iso) (ct∈A B x cnext y) ) ct-inject : {ox oy : Ordinal} → (x1 : Chain B x cnext ox ) → (y : Chain B x cnext oy ) → (cton0 B x cnext x1) ≡ (cton0 B x cnext y) → ox ≡ oy ct-inject {ox} {ox} (cfirst x) (cfirst x₁) refl = refl ct-inject {.(cnext x₀ )} {.(cnext x₃ )} (csuc x₀ ax x₁ x₂) (csuc x₃ ax₁ y x₄) eq = cong cnext ct05 where ct06 : {x y : ℕ} → suc x ≡ suc y → x ≡ y ct06 refl = refl ct05 : x₀ ≡ x₃ ct05 = ct-inject x₁ y (ct06 eq) ct-monotonic : {ox oy : Ordinal} → (x1 : Chain B x cnext ox ) → (y : Chain B x cnext oy ) → (cton0 B x cnext x1) Data.Nat.< (cton0 B x cnext y) → * ox < * oy ct-monotonic {ox} {oy} x1 (csuc oy1 ay y _) (s≤s lt) with NP.<-cmp ( cton0 B x cnext x1 ) ( cton0 B x cnext y ) ... | tri< a ¬b ¬c = ct07 where ct07 : * ox < * (cnext oy1) ct07 with ODC.∋-p O (IChainSet A ax) (* oy1) ... | no not = ⊥-elim ( not (subst (λ k → odef (IChainSet A ax) k ) (sym &iso) ay ) ) ... | yes ay1 = IsStrictPartialOrder.trans PO {me (ct02 x1) } {me (ct02 y)} {me ct031 } (ct-monotonic x1 y a ) ct011 where ct031 : A ∋ * (IChainSup>.y (InfiniteChain.c-infinite ifc oy1 (subst (λ k → odef (IChainSet A ax) k) &iso ay1 ) )) ct031 = subst (λ k → odef A k ) (sym &iso) ( IChainSup>.A∋y (InfiniteChain.c-infinite ifc oy1 (subst (λ k → odef (IChainSet A ax) k) &iso ay1 )) ) ct011 : * oy1 < * ( IChainSup>.y (InfiniteChain.c-infinite ifc oy1 (subst (λ k → odef (IChainSet A ax) k) &iso ay1 )) ) ct011 = IChainSup>.y>x (InfiniteChain.c-infinite ifc oy1 (subst (λ k → odef (IChainSet A ax) k) &iso ay1 )) ... | tri≈ ¬a b ¬c = ct11 where ct11 : * ox < * (cnext oy1) ct11 with ODC.∋-p O (IChainSet A ax) (* oy1) ... | no not = ⊥-elim ( not (subst (λ k → odef (IChainSet A ax) k ) (sym &iso) ay ) ) ... | yes ay1 = subst (λ k → * k < _) (sym (ct-inject _ _ b)) ct011 where ct011 : * oy1 < * ( IChainSup>.y (InfiniteChain.c-infinite ifc oy1 (subst (λ k → odef (IChainSet A ax) k) &iso ay1 )) ) ct011 = IChainSup>.y>x (InfiniteChain.c-infinite ifc oy1 (subst (λ k → odef (IChainSet A ax) k) &iso ay1 )) ... | tri> ¬a ¬b c = ⊥-elim ( nat-≤> lt c ) ct12 : {y z : Element (TransitiveClosure B x cnext) } → elm y ≡ elm z → elm y < elm z → ⊥ ct12 {y} {z} y=z y<z = IsStrictPartialOrder.irrefl IPO {y} {z} y=z y<z ct13 : {y z : Element (TransitiveClosure B x cnext) } → elm y < elm z → elm z < elm y → ⊥ ct13 {y} {z} y<z y>z = IsStrictPartialOrder.irrefl IPO {y} {y} refl ( IsStrictPartialOrder.trans IPO {y} {z} {y} y<z y>z ) ct17 : (x1 : Element (TransitiveClosure B x cnext)) → Chain B x cnext (& (elm x1)) ct17 x1 = is-elm x1 cmp : Trichotomous _ _ cmp x1 y with NP.<-cmp (cton B x cnext x1) (cton B x cnext y) ... | tri< a ¬b ¬c = tri< ct04 ct14 ct15 where ct04 : elm x1 < elm y ct04 = subst₂ (λ j k → j < k ) *iso *iso (ct-monotonic (is-elm x1) (is-elm y) a) ct14 : ¬ elm x1 ≡ elm y ct14 eq = ct12 {x1} {y} eq (subst₂ (λ j k → j < k ) *iso *iso (ct-monotonic (is-elm x1) (is-elm y) a ) ) ct15 : ¬ (elm y < elm x1) ct15 lt = ct13 {y} {x1} lt (subst₂ (λ j k → j < k ) *iso *iso (ct-monotonic (is-elm x1) (is-elm y) a ) ) ... | tri≈ ¬a b ¬c = tri≈ (ct12 {x1} {y} ct16) ct16 (ct12 {y} {x1} (sym ct16)) where ct16 : elm x1 ≡ elm y ct16 = subst₂ (λ j k → j ≡ k ) *iso *iso (cong (*) (ct-inject {& (elm x1)} {& (elm y)} (is-elm x1) (is-elm y) b )) ... | tri> ¬a ¬b c = tri> ct15 ct14 ct04 where ct04 : elm y < elm x1 ct04 = subst₂ (λ j k → j < k ) *iso *iso (ct-monotonic (is-elm y) (is-elm x1) c) ct14 : ¬ elm x1 ≡ elm y ct14 eq = ct12 {y} {x1} (sym eq) (subst₂ (λ j k → j < k ) *iso *iso (ct-monotonic (is-elm y) (is-elm x1) c ) ) ct15 : ¬ (elm x1 < elm y) ct15 lt = ct13 {x1} {y} lt (subst₂ (λ j k → j < k ) *iso *iso (ct-monotonic (is-elm y) (is-elm x1) c ) ) record IsFC (A : HOD) {x : Ordinal} (ax : A ∋ * x) (y : Ordinal) : Set n where field icy : odef (IChainSet A ax) y c-finite : ¬ IChainSup> A (subst (λ k → odef A k ) (sym &iso) (proj1 icy) ) record Maximal ( A : HOD ) : Set (Level.suc n) where field maximal : HOD A∋maximal : A ∋ maximal ¬maximal<x : {x : HOD} → A ∋ x → ¬ maximal < x -- A is Partial, use negative -- -- possible three cases in a limit ordinal step -- -- case 1) < goes x o< -- case 2) no > x in some chain ( maximal ) -- case 3) countably infinite chain below x -- Zorn-lemma-3case : { A : HOD } → o∅ o< & A → IsPartialOrderSet A → (x : Ordinal ) → (ax : odef A x) → OSup> A (d→∋ A ax) ∨ Maximal A ∨ InfiniteChain A x (d→∋ A ax) Zorn-lemma-3case {A} 0<A PO x ax = zc2 where Gtx : HOD Gtx = record { od = record { def = λ y → odef ( IChainSet A ax ) y ∧ ( x o< y ) } ; odmax = & A ; <odmax = λ lt → subst (λ k → k o< & A) &iso (c<→o< (d→∋ A (proj1 (proj1 lt)))) } HG : HOD HG = record { od = record { def = λ y → odef A y ∧ IsFC A (d→∋ A ax ) y } ; odmax = & A ; <odmax = λ lt → subst (λ k → k o< & A) &iso (c<→o< (d→∋ A (proj1 lt) )) } zc2 : OSup> A (d→∋ A ax) ∨ Maximal A ∨ InfiniteChain A x (d→∋ A ax ) zc2 with is-o∅ (& Gtx) ... | no not = case1 record { y = & y ; icy = zc4 ; y>x = proj2 zc3 } where y : HOD y = ODC.minimal O Gtx (λ eq → not (=od∅→≡o∅ eq)) zc3 : odef ( IChainSet A ax ) (& y) ∧ ( x o< (& y )) zc3 = ODC.x∋minimal O Gtx (λ eq → not (=od∅→≡o∅ eq)) zc4 : odef (IChainSet A (subst (OD.def (od A)) (sym &iso) ax)) (& y) zc4 = ⟪ proj1 (proj1 zc3) , (subst (λ k → IChained A k (& y)) (sym &iso) (proj2 (proj1 zc3))) ⟫ ... | yes nogt with is-o∅ (& HG) ... | no finite-chain = case2 (case1 record { maximal = y ; A∋maximal = proj1 zc3 ; ¬maximal<x = zc4 } ) where y : HOD y = ODC.minimal O HG (λ eq → finite-chain (=od∅→≡o∅ eq)) zc3 : odef A (& y) ∧ IsFC A (d→∋ A ax ) (& y) zc3 = ODC.x∋minimal O HG (λ eq → finite-chain (=od∅→≡o∅ eq)) zc4 : {z : HOD} → A ∋ z → ¬ (y < z) zc4 {z} az y<z = IsFC.c-finite (proj2 zc3) record { y = & z ; A∋y = az ; y>x = subst₂ (λ j k → j < k ) (sym *iso) (sym *iso) y<z } ... | yes inifite = case2 (case2 record { c-infinite = zc91 ; chain<x = zc10 } ) where B : HOD B = IChainSet A ax -- (me (subst (OD.def (od A)) (sym &iso) (is-elm x))) B1 : HOD B1 = IChainSet A (subst (OD.def (od A)) (sym &iso) ax) Nx : (y : Ordinal) → odef A y → HOD Nx y ay = record { od = record { def = λ x → odef A x ∧ ( * y < * x ) } ; odmax = & A ; <odmax = λ lt → subst (λ k → k o< & A) &iso (c<→o< (d→∋ A (proj1 lt))) } zc10 : (y : Ordinal) → odef (IChainSet A (subst (OD.def (od A)) (sym &iso) ax)) y → y o< x zc10 oy icsy = zc21 where zc20 : (y : HOD) → (IChainSet A ax) ∋ y → x o< & y → ⊥ zc20 y icsy lt = ¬A∋x→A≡od∅ Gtx ⟪ icsy , lt ⟫ nogt zc22 : IChainSet A ax ∋ * oy zc22 = ⟪ subst (λ k → odef A k) (sym &iso) (proj1 icsy) , subst₂ (λ j k → IChained A j k ) &iso (sym &iso) (proj2 icsy) ⟫ zc21 : oy o< x zc21 with trio< oy x ... | tri< a ¬b ¬c = a ... | tri≈ ¬a b ¬c = ⊥-elim (¬IChained-refl A PO (subst₂ (λ j k → IChained A j k ) &iso b (proj2 icsy)) ) ... | tri> ¬a ¬b c = ⊥-elim ( zc20 (* oy) zc22 (subst (λ k → x o< k) (sym &iso) c )) zc91 : (y : Ordinal) (cy : odef B1 y) → IChainSup> A (ic→A∋y A (subst (OD.def (od A)) (sym &iso) ax) cy) zc91 y cy with is-o∅ (& (Nx y (proj1 cy) )) ... | yes no-next = ⊥-elim zc16 where zc18 : ¬ IChainSup> A (subst (odef A) (sym &iso) (proj1 (subst (λ k → odef (IChainSet A (d→∋ A ax)) k) (sym &iso) cy))) zc18 ics = ¬A∋x→A≡od∅ (Nx y (proj1 cy) ) ⟪ subst (λ k → odef A k ) (sym &iso) (IChainSup>.A∋y ics) , subst₂ (λ j k → j < k ) *iso (cong (*) (sym &iso))( IChainSup>.y>x ics) ⟫ no-next zc17 : IsFC A {x} (d→∋ A ax) (& (* y)) zc17 = record { icy = subst (λ k → odef (IChainSet A (d→∋ A ax)) k) (sym &iso) cy ; c-finite = zc18 } zc16 : ⊥ zc16 = ¬A∋x→A≡od∅ HG ⟪ subst (λ k → odef A k ) (sym &iso) (proj1 cy ) , zc17 ⟫ inifite ... | no not = record { y = & zc13 ; A∋y = proj1 zc12 ; y>x = proj2 zc12 } where zc13 = ODC.minimal O (Nx y (proj1 cy)) (λ eq → not (=od∅→≡o∅ eq )) zc12 : odef A (& zc13 ) ∧ ( * y < * ( & zc13 )) zc12 = ODC.x∋minimal O (Nx y (proj1 cy)) (λ eq → not (=od∅→≡o∅ eq )) all-climb-case : { A : HOD } → (0<A : o∅ o< & A) → IsPartialOrderSet A → (( x : Ordinal ) → (ax : odef A (& (* x))) → OSup> A ax ) → (x : HOD) ( ax : A ∋ x ) → InfiniteChain A (& A) (d→∋ A ax) all-climb-case {A} 0<A PO climb x ax = record { c-infinite = ac00 ; chain<x = ac01 } where B = IChainSet A ax ac01 : (y : Ordinal) → odef (IChainSet A (d→∋ A ax)) y → y o< & A ac01 y ⟪ ay , _ ⟫ = subst (λ k → k o< & A ) &iso (c<→o< (subst (λ k → odef A k ) (sym &iso) ay) ) ac00 : (y : Ordinal) (cy : odef (IChainSet A (d→∋ A ax)) y) → IChainSup> A (ic→A∋y A (d→∋ A ax) cy) ac00 y cy = record { y = z ; A∋y = az ; y>x = y<z} where ay : odef A (& (* y)) ay = subst (λ k → odef A k) (sym &iso) (proj1 cy) z : Ordinal z = OSup>.y ( climb y ay) az : odef A z az = subst (λ k → odef A k) &iso ( incl (IChainSet⊆A {A} ay ) (subst (λ k → odef (IChainSet A ay) k ) (sym &iso) (OSup>.icy ( climb y ay)))) icy : odef (IChainSet A ay ) z icy = OSup>.icy ( climb y ay ) y<z : * y < * z y<z = ic→< {A} PO y (subst (λ k → odef A k) &iso ay) (IChained.iy (proj2 icy)) (subst (λ k → ic-connect k (IChained.iy (proj2 icy))) &iso (IChained.ic (proj2 icy))) -- <-TransFinite : ( A : HOD ) → IsTotalOrderSet A -- → ( (x : Ordinal) → ((y : Ordinal) → y o< x → ZChain A y) → ZChain A x ) → (x : Ordinal ) → ZChain A x -- <-TransFinite A TA ind x = TransFinite {ZChain A} ind x -- -- inductive maxmum tree from x -- tree structure -- ≤-monotonic-f : (A : HOD) → ( Ordinal → Ordinal ) → Set (Level.suc n) ≤-monotonic-f A f = (x : Ordinal ) → odef A x → ( * x ≤ * (f x) ) ∧ odef A (f x ) record Indirect< (A : HOD) {x y : Ordinal } (xa : odef A x) (ya : odef A y) (z : Ordinal) : Set n where field az : odef A z x<z : * x < * z z<y : * z < * y record Prev< (A : HOD) {x : Ordinal } (xa : odef A x) ( f : Ordinal → Ordinal ) : Set n where field y : Ordinal ay : odef A y x=fy : x ≡ f y record SUP ( A B : HOD ) : Set (Level.suc n) where field sup : HOD A∋maximal : A ∋ sup x<sup : {x : HOD} → B ∋ x → (x ≡ sup ) ∨ (x < sup ) -- B is Total, use positive SupCond : ( A B : HOD) → (B⊆A : B ⊆ A) → IsTotalOrderSet B → Set (Level.suc n) SupCond A B _ _ = SUP A B record ZChain ( A : HOD ) {x : Ordinal} (ax : A ∋ * x) ( f : Ordinal → Ordinal ) (mf : ≤-monotonic-f A f ) (sup : (C : Ordinal ) → (* C ⊆ A) → IsTotalOrderSet (* C) → Ordinal) (z : Ordinal) : Set (Level.suc n) where field chain : HOD chain⊆A : chain ⊆ A f-total : IsTotalOrderSet chain f-next : {a : Ordinal } → odef chain a → odef chain (f a) is-max : {a b : Ordinal } → (ca : odef chain a ) → odef A b → a o< z → ( Prev< A (incl chain⊆A (subst (λ k → odef chain k ) (sym &iso) ca)) f ∨ (sup (& chain) (subst (λ k → k ⊆ A) (sym *iso) chain⊆A) (subst (λ k → IsTotalOrderSet k) (sym *iso) f-total) ≡ b )) → * a < * b → odef chain b Zorn-lemma : { A : HOD } → o∅ o< & A → IsPartialOrderSet A → ( ( B : HOD) → (B⊆A : B ⊆ A) → IsTotalOrderSet B → SUP A B ) -- SUP condition → Maximal A Zorn-lemma {A} 0<A PO supP = zorn00 where supO : (C : Ordinal ) → (* C) ⊆ A → IsTotalOrderSet (* C) → Ordinal supO C C⊆A TC = & ( SUP.sup ( supP (* C) C⊆A TC )) z01 : {a b : HOD} → A ∋ a → A ∋ b → (a ≡ b ) ∨ (a < b ) → b < a → ⊥ z01 {a} {b} A∋a A∋b (case1 a=b) b<a = IsStrictPartialOrder.irrefl PO {me A∋b} {me A∋a} (sym a=b) b<a z01 {a} {b} A∋a A∋b (case2 a<b) b<a = IsStrictPartialOrder.irrefl PO {me A∋b} {me A∋b} refl (IsStrictPartialOrder.trans PO {me A∋b} {me A∋a} {me A∋b} b<a a<b) s : HOD s = ODC.minimal O A (λ eq → ¬x<0 ( subst (λ k → o∅ o< k ) (=od∅→≡o∅ eq) 0<A )) sa : A ∋ * ( & s ) sa = subst (λ k → odef A (& k) ) (sym *iso) ( ODC.x∋minimal O A (λ eq → ¬x<0 ( subst (λ k → o∅ o< k ) (=od∅→≡o∅ eq) 0<A )) ) HasMaximal : HOD HasMaximal = record { od = record { def = λ x → odef A x ∧ ( (m : Ordinal) → odef A m → ¬ (* x < * m)) } ; odmax = & A ; <odmax = z07 } where z07 : {y : Ordinal} → odef A y ∧ ((m : Ordinal) → odef A m → ¬ (* y < * m)) → y o< & A z07 {y} p = subst (λ k → k o< & A) &iso ( c<→o< (subst (λ k → odef A k ) (sym &iso ) (proj1 p ))) no-maximum : HasMaximal =h= od∅ → (x : Ordinal) → ((m : Ordinal) → odef A m → odef A x ∧ (¬ (* x < * m) )) → ⊥ no-maximum nomx x P = ¬x<0 (eq→ nomx {x} {!!} ) Gtx : { x : HOD} → A ∋ x → HOD Gtx {x} ax = record { od = record { def = λ y → odef A y ∧ (x < (* y)) } ; odmax = & A ; <odmax = {!!} } cf : ¬ Maximal A → Ordinal → Ordinal cf nmx x with ODC.∋-p O A (* x) ... | no _ = o∅ ... | yes ax with is-o∅ (& ( Gtx ax )) ... | yes nogt = ⊥-elim (no-maximum (≡o∅→=od∅ {!!} ) x x-is-maximal ) where -- no larger element, so it is maximal x-is-maximal : (m : Ordinal) → odef A m → odef A x ∧ (¬ (* x < * m)) x-is-maximal m am = ⟪ subst (λ k → odef A k) &iso ax , ¬x<m ⟫ where ¬x<m : ¬ (* x < * m) ¬x<m x<m = ∅< {Gtx ax} {* m} ⟪ subst (λ k → odef A k) (sym &iso) am , subst (λ k → * x < k ) (cong (*) (sym &iso)) x<m ⟫ (≡o∅→=od∅ nogt) ... | no not = & (ODC.minimal O (Gtx ax) (λ eq → not (=od∅→≡o∅ eq))) cf-is-<-monotonic : (nmx : ¬ Maximal A ) → (x : Ordinal) → odef A x → ( * x < * (cf nmx x) ) ∧ odef A (cf nmx x ) cf-is-<-monotonic nmx x ax = ⟪ {!!} , {!!} ⟫ cf-is-≤-monotonic : (nmx : ¬ Maximal A ) → ≤-monotonic-f A ( cf nmx ) cf-is-≤-monotonic nmx x ax = ⟪ case2 (proj1 ( cf-is-<-monotonic nmx x ax )) , proj2 ( cf-is-<-monotonic nmx x ax ) ⟫ zsup : ( f : Ordinal → Ordinal ) → (mf : ≤-monotonic-f A f) → (zc : ZChain A sa f mf supO (& A)) → SUP A (ZChain.chain zc) zsup f mf zc = supP (ZChain.chain zc) (ZChain.chain⊆A zc) ( ZChain.f-total zc ) -- zsup zc f mf = & ( SUP.sup (supP (ZChain.chain zc) (ZChain.chain⊆A zc) ( ZChain.f-total zc f mf ) ) ) A∋zsup : (nmx : ¬ Maximal A ) (zc : ZChain A sa (cf nmx) (cf-is-≤-monotonic nmx) supO (& A)) → A ∋ * ( & ( SUP.sup (zsup (cf nmx) (cf-is-≤-monotonic nmx) zc ) )) A∋zsup nmx zc = subst (λ k → odef A (& k )) (sym *iso) ( SUP.A∋maximal (zsup (cf nmx) (cf-is-≤-monotonic nmx) zc ) ) z03 : ( f : Ordinal → Ordinal ) → (mf : ≤-monotonic-f A f ) (zc : ZChain A sa f mf supO (& A)) → f (& ( SUP.sup (zsup f mf zc ))) ≡ & (SUP.sup (zsup f mf zc )) z03 = {!!} z04 : (nmx : ¬ Maximal A ) → (zc : ZChain A sa (cf nmx) (cf-is-≤-monotonic nmx) supO (& A)) → ⊥ z04 nmx zc = z01 {* (cf nmx c)} {* c} {!!} (A∋zsup nmx zc ) (case1 ( cong (*)( z03 (cf nmx) (cf-is-≤-monotonic nmx ) zc ))) (proj1 (cf-is-<-monotonic nmx c ((subst λ k → odef A k ) &iso (A∋zsup nmx zc )))) where c = & (SUP.sup (zsup (cf nmx) (cf-is-≤-monotonic nmx) zc )) -- ZChain is not compatible with the SUP condition ind : ( f : Ordinal → Ordinal ) → (mf : ≤-monotonic-f A f ) → (x : Ordinal) → ((y : Ordinal) → y o< x → ZChain A sa f mf supO y ) → ZChain A sa f mf supO x ind f mf x prev with Oprev-p x ... | yes op with ODC.∋-p O A (* x) ... | no ¬Ax = zc1 where -- we have previous ordinal and ¬ A ∋ x, use previous Zchain px = Oprev.oprev op zc0 : ZChain A sa f mf supO (Oprev.oprev op) zc0 = prev px (subst (λ k → px o< k) (Oprev.oprev=x op) <-osuc) zc1 : ZChain A sa f mf supO x zc1 = record { chain = ZChain.chain zc0 ; chain⊆A = ZChain.chain⊆A zc0 ; f-total = ZChain.f-total zc0 ; f-next = ZChain.f-next zc0 ; is-max = {!!} } ... | yes ax = zc4 where -- we have previous ordinal and A ∋ x px = Oprev.oprev op zc0 : ZChain A sa f mf supO (Oprev.oprev op) zc0 = prev px (subst (λ k → px o< k) (Oprev.oprev=x op) <-osuc) -- x is in the previous chain, use the same -- x has some y which y < x ∧ f y ≡ x -- x has no y which y < x zc4 : ZChain A sa f mf supO x zc4 = record { chain = {!!} ; chain⊆A = {!!} ; f-total = {!!} ; f-next = {!!} ; is-max = {!!} } ind f mf x prev | no ¬ox with trio< (& A) x --- limit ordinal case ... | tri< a ¬b ¬c = record { chain = ZChain.chain zc0 ; chain⊆A = ZChain.chain⊆A zc0 ; f-total = ZChain.f-total zc0 ; f-next = ZChain.f-next zc0 ; is-max = {!!} } where zc0 = prev (& A) a ... | tri≈ ¬a b ¬c = {!!} ... | tri> ¬a ¬b c = {!!} zorn00 : Maximal A zorn00 with is-o∅ ( & HasMaximal ) -- we have no Level (suc n) LEM ... | no not = record { maximal = ODC.minimal O HasMaximal (λ eq → not (=od∅→≡o∅ eq)) ; A∋maximal = zorn01 ; ¬maximal<x = zorn02 } where -- yes we have the maximal zorn03 : odef HasMaximal ( & ( ODC.minimal O HasMaximal (λ eq → not (=od∅→≡o∅ eq)) ) ) zorn03 = ODC.x∋minimal O HasMaximal (λ eq → not (=od∅→≡o∅ eq)) zorn01 : A ∋ ODC.minimal O HasMaximal (λ eq → not (=od∅→≡o∅ eq)) zorn01 = proj1 zorn03 zorn02 : {x : HOD} → A ∋ x → ¬ (ODC.minimal O HasMaximal (λ eq → not (=od∅→≡o∅ eq)) < x) zorn02 {x} ax m<x = proj2 zorn03 (& x) ax (subst₂ (λ j k → j < k) (sym *iso) (sym *iso) m<x ) ... | yes ¬Maximal = ⊥-elim ( z04 nmx (zorn03 (cf nmx) (cf-is-≤-monotonic nmx))) where -- if we have no maximal, make ZChain, which contradict SUP condition nmx : ¬ Maximal A nmx mx = ∅< {HasMaximal} zc5 ( ≡o∅→=od∅ ¬Maximal ) where zc5 : odef A (& (Maximal.maximal mx)) ∧ (( y : Ordinal ) → odef A y → ¬ (* (& (Maximal.maximal mx)) < * y)) zc5 = ⟪ Maximal.A∋maximal mx , (λ y ay mx<y → Maximal.¬maximal<x mx (subst (λ k → odef A k ) (sym &iso) ay) (subst (λ k → k < * y) *iso mx<y) ) ⟫ zorn03 : ( f : Ordinal → Ordinal ) → (mf : ≤-monotonic-f A f ) → ZChain A sa f mf supO (& A) zorn03 f mf = TransFinite (ind f mf) (& A) -- usage (see filter.agda ) -- -- _⊆'_ : ( A B : HOD ) → Set n -- _⊆'_ A B = (x : Ordinal ) → odef A x → odef B x -- MaximumSubset : {L P : HOD} -- → o∅ o< & L → o∅ o< & P → P ⊆ L -- → IsPartialOrderSet P _⊆'_ -- → ( (B : HOD) → B ⊆ P → IsTotalOrderSet B _⊆'_ → SUP P B _⊆'_ ) -- → Maximal P (_⊆'_) -- MaximumSubset {L} {P} 0<L 0<P P⊆L PO SP = Zorn-lemma {P} {_⊆'_} 0<P PO SP