Mercurial > hg > Members > kono > Proof > ZF-in-agda
view src/zorn.agda @ 477:24b4b854b310
separate zorn lemma
author | Shinji KONO <kono@ie.u-ryukyu.ac.jp> |
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date | Sat, 02 Apr 2022 08:37:17 +0900 |
parents | src/ODC.agda@3fc164626468 |
children | c6346d92f1a1 |
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open import Level open import Ordinals module zorn {n : Level } (O : Ordinals {n}) where open import zf open import logic -- open import partfunc {n} O import OD 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 record Element (A : HOD) : Set (suc n) where field elm : HOD is-elm : A ∋ elm open Element TotalOrderSet : ( A : HOD ) → (_<_ : (x y : HOD) → Set n ) → Set (suc n) TotalOrderSet A _<_ = Trichotomous (λ (x : Element A) y → elm x ≡ elm y ) (λ x y → elm x < elm y ) PartialOrderSet : ( A : HOD ) → (_<_ : (x y : HOD) → Set n ) → Set (suc n) PartialOrderSet A _<_ = (a b : Element A) → (elm a < elm b → (¬ (elm b < elm a) ∧ (¬ (elm a ≡ elm b) ))) ∧ (elm a ≡ elm b → (¬ elm a < elm b) ∧ (¬ elm b < elm a)) me : { A a : HOD } → A ∋ a → Element A me {A} {a} lt = record { elm = a ; is-elm = lt } record SUP ( A B : HOD ) (_<_ : (x y : HOD) → Set n ) : Set (suc n) where field sup : HOD A∋maximal : A ∋ sup x≤sup : {x : HOD} → B ∋ x → (x ≡ sup ) ∨ (x < sup ) record Maximal ( A : HOD ) (_<_ : (x y : HOD) → Set n ) : Set (suc n) where field maximal : HOD A∋maximal : A ∋ maximal ¬maximal<x : {x : HOD} → A ∋ x → ¬ maximal < x open _==_ open _⊆_ record ZChain ( A : HOD ) (y : Ordinal) (_<_ : (x y : HOD) → Set n ) : Set (suc n) where field B : HOD B⊆A : B ⊆ A total : TotalOrderSet B _<_ fb : {x : HOD } → A ∋ x → HOD B∋fb : (x : HOD ) → (ax : A ∋ x) → B ∋ fb ax ¬x≤sup : (sup : HOD) → (as : A ∋ sup ) → & sup o< osuc y → sup < fb as Zorn-lemma : { A : HOD } → { _<_ : (x y : HOD) → Set n } → o∅ o< & A → ( {a b c : HOD} → a < b → b < c → a < c ) → PartialOrderSet A _<_ → ( ( B : HOD) → (B⊆A : B ⊆ A) → TotalOrderSet B _<_ → SUP A B _<_ ) → Maximal A _<_ Zorn-lemma {A} {_<_} 0<A TR PO supP = zorn00 where someA : HOD someA = ODC.minimal O A (λ eq → ¬x<0 ( subst (λ k → o∅ o< k ) (=od∅→≡o∅ eq) 0<A )) isSomeA : A ∋ someA isSomeA = 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 → (m : Ordinal) → odef A m → odef A x ∧ (¬ (* x < * m))} ; odmax = & A ; <odmax = {!!} } where z07 : {y : Ordinal} → ((m : Ordinal) → odef A y ∧ 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 (& someA)) ))) 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} (λ m am → P m am )) Gtx : { x : HOD} → A ∋ x → HOD Gtx {x} ax = record { od = record { def = λ y → odef A y ∧ (x < (* y)) } ; odmax = & A ; <odmax = {!!} } 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 = proj1 (proj2 (PO (me A∋b) (me A∋a)) (sym a=b)) b<a z01 {a} {b} A∋a A∋b (case2 a<b) b<a = proj1 (PO (me A∋b) (me A∋a)) b<a ⟪ a<b , (λ b=a → proj1 (proj2 (PO (me A∋b) (me A∋a)) b=a ) b<a ) ⟫ ZChain→¬SUP : (z : ZChain A (& A) _<_ ) → ¬ (SUP A (ZChain.B z) _<_ ) ZChain→¬SUP z sp = ⊥-elim (z02 (ZChain.fb z (SUP.A∋maximal sp)) (ZChain.B∋fb z _ (SUP.A∋maximal sp)) (ZChain.¬x≤sup z _ (SUP.A∋maximal sp) z03 )) where z03 : & (SUP.sup sp) o< osuc (& A) z03 = ordtrans (c<→o< (SUP.A∋maximal sp)) <-osuc z02 : (x : HOD) → ZChain.B z ∋ x → SUP.sup sp < x → ⊥ z02 x xe s<x = z01 (incl (ZChain.B⊆A z) xe) (SUP.A∋maximal sp) (SUP.x≤sup sp xe) s<x ind : HasMaximal =h= od∅ → (x : Ordinal) → ((y : Ordinal) → y o< x → ZChain A y _<_ ) → ZChain A x _<_ ind nomx x prev with Oprev-p x ... | yes op with ODC.∋-p O A (* x) ... | no ¬Ax = record { B = ZChain.B zc1 ; B⊆A = ZChain.B⊆A zc1 ; total = ZChain.total zc1 ; fb = ZChain.fb zc1 ; B∋fb = ZChain.B∋fb zc1 ; ¬x≤sup = z04 } where -- we have previous ordinal and ¬ A ∋ x, use previous Zchain px = Oprev.oprev op zc1 : ZChain A px _<_ zc1 = prev px (subst (λ k → px o< k) (Oprev.oprev=x op) <-osuc) z04 : (sup : HOD) (as : A ∋ sup) → & sup o< osuc x → sup < ZChain.fb zc1 as z04 sup as s<x with trio< (& sup) x ... | tri≈ ¬a b ¬c = ⊥-elim (¬Ax (subst (λ k → odef A k) (trans b (sym &iso)) as) ) ... | tri< a ¬b ¬c = ZChain.¬x≤sup zc1 _ as ( subst (λ k → & sup o< k ) (sym (Oprev.oprev=x op)) a ) ... | tri> ¬a ¬b c with osuc-≡< s<x ... | case1 eq = ⊥-elim (¬Ax (subst (λ k → odef A k) (trans eq (sym &iso)) as) ) ... | case2 lt = ⊥-elim (¬a lt ) ... | yes ax = z06 where -- we have previous ordinal and A ∋ x px = Oprev.oprev op zc1 : ZChain A px _<_ zc1 = prev px (subst (λ k → px o< k) (Oprev.oprev=x op) <-osuc) z06 : ZChain A x _<_ z06 with is-o∅ (& (Gtx ax)) ... | yes nogt = ⊥-elim (no-maximum nomx 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 = record { B = Bx -- we have larger element, let's create ZChain ; B⊆A = B⊆A ; total = {!!} ; fb = {!!} ; B∋fb = {!!} ; ¬x≤sup = {!!} } where B = ZChain.B zc1 Bx : HOD Bx = record { od = record { def = λ y → (x ≡ y) ∨ odef B y } ; odmax = & A ; <odmax = {!!} } B⊆A : Bx ⊆ A B⊆A = record { incl = λ {y} by → z07 y by } where z07 : (y : HOD) → Bx ∋ y → A ∋ y z07 y (case1 x=y) = subst (λ k → odef A k ) (trans &iso x=y) ax z07 y (case2 by) = incl (ZChain.B⊆A zc1 ) by m = ODC.minimal O (Gtx ax) (λ eq → not (=od∅→≡o∅ eq)) ind nomx x prev | no ¬ox with trio< (& A) x --- limit ordinal case ... | tri< a ¬b ¬c = record { B = ZChain.B zc1 ; B⊆A = ZChain.B⊆A zc1 ; total = ZChain.total zc1 ; fb = ZChain.fb zc1 ; B∋fb = ZChain.B∋fb zc1 ; ¬x≤sup = {!!} } where zc1 : ZChain A (& A) _<_ zc1 = prev (& A) a ... | tri≈ ¬a b ¬c = record { B = B ; B⊆A = {!!} ; total = {!!} ; fb = {!!} ; B∋fb = {!!} ; ¬x≤sup = {!!} } where B : HOD B = record { od = record { def = λ y → (y<x : y o< x ) → odef (ZChain.B (prev y y<x)) y } ; odmax = & A ; <odmax = {!!} } ... | tri> ¬a ¬b c = {!!} zorn00 : Maximal A _<_ zorn00 with is-o∅ ( & HasMaximal ) ... | no not = record { maximal = ODC.minimal O HasMaximal (λ eq → not (=od∅→≡o∅ eq)) ; A∋maximal = zorn01 ; ¬maximal<x = zorn02 } where 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 (& someA) isSomeA ) 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 ( ZChain→¬SUP (z (& A) (≡o∅→=od∅ ¬Maximal)) ( supP B (ZChain.B⊆A (z (& A) (≡o∅→=od∅ ¬Maximal))) (ZChain.total (z (& A) (≡o∅→=od∅ ¬Maximal))) )) where z : (x : Ordinal) → HasMaximal =h= od∅ → ZChain A x _<_ z x nomx = TransFinite (ind nomx) x B = ZChain.B (z (& A) (≡o∅→=od∅ ¬Maximal) )