Mercurial > hg > Members > kono > Proof > category
annotate equalizer.agda @ 253:24e83b8b81be
fix
author | Shinji KONO <kono@ie.u-ryukyu.ac.jp> |
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date | Wed, 11 Sep 2013 20:26:48 +0900 |
parents | e0835b8dd51b |
children | 45b81fcb8a64 |
rev | line source |
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205 | 1 --- |
2 -- | |
3 -- Equalizer | |
4 -- | |
208 | 5 -- e f |
205 | 6 -- c --------> a ----------> b |
208 | 7 -- ^ . ----------> |
205 | 8 -- | . g |
230 | 9 -- |k . |
10 -- | . h | |
11 -- d | |
205 | 12 -- |
13 -- Shinji KONO <kono@ie.u-ryukyu.ac.jp> | |
14 ---- | |
15 | |
230 | 16 open import Category -- https://github.com/konn/category-agda |
205 | 17 open import Level |
18 module equalizer { c₁ c₂ ℓ : Level} { A : Category c₁ c₂ ℓ } where | |
19 | |
20 open import HomReasoning | |
21 open import cat-utility | |
22 | |
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23 record Equalizer { c₁ c₂ ℓ : Level} ( A : Category c₁ c₂ ℓ ) {c a b : Obj A} (e : Hom A c a) (f g : Hom A a b) : Set (ℓ ⊔ (c₁ ⊔ c₂)) where |
205 | 24 field |
221 | 25 fe=ge : A [ A [ f o e ] ≈ A [ g o e ] ] |
209 | 26 k : {d : Obj A} (h : Hom A d a) → A [ A [ f o h ] ≈ A [ g o h ] ] → Hom A d c |
215 | 27 ek=h : {d : Obj A} → ∀ {h : Hom A d a} → {eq : A [ A [ f o h ] ≈ A [ g o h ] ] } → A [ A [ e o k {d} h eq ] ≈ h ] |
230 | 28 uniqueness : {d : Obj A} → ∀ {h : Hom A d a} → {eq : A [ A [ f o h ] ≈ A [ g o h ] ] } → {k' : Hom A d c } → |
214 | 29 A [ A [ e o k' ] ≈ h ] → A [ k {d} h eq ≈ k' ] |
209 | 30 equalizer : Hom A c a |
31 equalizer = e | |
206 | 32 |
253 | 33 |
230 | 34 -- |
251 | 35 -- Burroni's Flat Equational Definition of Equalizer |
230 | 36 -- |
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37 record Burroni { c₁ c₂ ℓ : Level} ( A : Category c₁ c₂ ℓ ) {c a b : Obj A} (f g : Hom A a b) (e : Hom A c a) : Set (ℓ ⊔ (c₁ ⊔ c₂)) where |
206 | 38 field |
245 | 39 α : {a b c : Obj A } → (f : Hom A a b) → (g : Hom A a b ) → (e : Hom A c a ) → Hom A c a |
214 | 40 γ : {a b c d : Obj A } → (f : Hom A a b) → (g : Hom A a b ) → (h : Hom A d a ) → Hom A d c |
245 | 41 δ : {a b c : Obj A } → (e : Hom A c a ) → (f : Hom A a b) → Hom A a c |
242 | 42 cong-α : {a b c : Obj A } → { e : Hom A c a } |
245 | 43 → {f g g' : Hom A a b } → A [ g ≈ g' ] → A [ α f g e ≈ α f g' e ] |
242 | 44 cong-γ : {a _ c d : Obj A } → {f g : Hom A a b} {h h' : Hom A d a } → A [ h ≈ h' ] |
243 | 45 → A [ γ {a} {b} {c} {d} f g h ≈ γ f g h' ] |
245 | 46 cong-δ : {a b c : Obj A } → {e : Hom A c a} → {f f' : Hom A a b} → A [ f ≈ f' ] → A [ δ e f ≈ δ e f' ] |
47 b1 : A [ A [ f o α {a} {b} {c} f g e ] ≈ A [ g o α {a} {b} {c} f g e ] ] | |
48 b2 : {d : Obj A } → {h : Hom A d a } → A [ A [ ( α {a} {b} {c} f g e ) o (γ {a} {b} {c} f g h) ] ≈ A [ h o α (A [ f o h ]) (A [ g o h ]) (id1 A d) ] ] | |
49 b3 : {a b d : Obj A} → (f : Hom A a b ) → {h : Hom A d a } → A [ A [ α {a} {b} {d} f f h o δ {a} {b} {d} h f ] ≈ id1 A a ] | |
207
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50 -- b4 : {c d : Obj A } {k : Hom A c a} → A [ β f g ( A [ α f g o k ] ) ≈ k ] |
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51 b4 : {d : Obj A } {k : Hom A d c} → |
245 | 52 A [ A [ γ {a} {b} {c} {d} f g ( A [ α {a} {b} {c} f g e o k ] ) o ( δ {d} {b} {d} (id1 A d) (A [ f o A [ α {a} {b} {c} f g e o k ] ] ) )] ≈ k ] |
207
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53 -- A [ α f g o β f g h ] ≈ h |
238
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54 β : { d a b : Obj A} → (f : Hom A a b) → (g : Hom A a b ) → (h : Hom A d a ) → Hom A d c |
245 | 55 β {d} {a} {b} f g h = A [ γ {a} {b} {c} f g h o δ {d} {b} {d} (id1 A d) (A [ f o h ]) ] |
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56 |
209 | 57 open Equalizer |
225 | 58 open Burroni |
209 | 59 |
225 | 60 -- |
61 -- Some obvious conditions for k (fe = ge) → ( fh = gh ) | |
62 -- | |
219 | 63 |
224 | 64 f1=g1 : { a b c : Obj A } {f g : Hom A a b } → (eq : A [ f ≈ g ] ) → (h : Hom A c a) → A [ A [ f o h ] ≈ A [ g o h ] ] |
65 f1=g1 eq h = let open ≈-Reasoning (A) in (resp refl-hom eq ) | |
66 | |
226 | 67 f1=f1 : { a b : Obj A } (f : Hom A a b ) → A [ A [ f o (id1 A a) ] ≈ A [ f o (id1 A a) ] ] |
230 | 68 f1=f1 f = let open ≈-Reasoning (A) in refl-hom |
226 | 69 |
224 | 70 f1=gh : { a b c d : Obj A } {f g : Hom A a b } → { e : Hom A c a } → { h : Hom A d c } → |
71 (eq : A [ A [ f o e ] ≈ A [ g o e ] ] ) → A [ A [ f o A [ e o h ] ] ≈ A [ g o A [ e o h ] ] ] | |
230 | 72 f1=gh {a} {b} {c} {d} {f} {g} {e} {h} eq = let open ≈-Reasoning (A) in |
224 | 73 begin |
74 f o ( e o h ) | |
75 ≈⟨ assoc ⟩ | |
230 | 76 (f o e ) o h |
224 | 77 ≈⟨ car eq ⟩ |
230 | 78 (g o e ) o h |
224 | 79 ≈↑⟨ assoc ⟩ |
80 g o ( e o h ) | |
81 ∎ | |
219 | 82 |
251 | 83 -------------------------------- |
225 | 84 -- |
85 -- | |
249 | 86 -- An isomorphic arrow c' to c makes another equalizer |
225 | 87 -- |
230 | 88 -- e eqa f g f |
222 | 89 -- c ----------> a ------->b |
230 | 90 -- |^ |
91 -- || | |
222 | 92 -- h || h-1 |
230 | 93 -- v| |
94 -- c' | |
222 | 95 |
234 | 96 equalizer+iso : {a b c c' : Obj A } {f g : Hom A a b } {e : Hom A c a } |
97 (h-1 : Hom A c' c ) → (h : Hom A c c' ) → | |
98 A [ A [ h o h-1 ] ≈ id1 A c' ] → A [ A [ h-1 o h ] ≈ id1 A c ] → | |
99 ( fe=ge' : A [ A [ f o A [ e o h-1 ] ] ≈ A [ g o A [ e o h-1 ] ] ] ) | |
100 ( eqa : Equalizer A e f g ) | |
101 → Equalizer A (A [ e o h-1 ] ) f g | |
102 equalizer+iso {a} {b} {c} {c'} {f} {g} {e} h-1 h hh-1=1 h-1h=1 fe=ge' eqa = record { | |
222 | 103 fe=ge = fe=ge1 ; |
104 k = λ j eq → A [ h o k eqa j eq ] ; | |
230 | 105 ek=h = ek=h1 ; |
222 | 106 uniqueness = uniqueness1 |
107 } where | |
234 | 108 fe=ge1 : A [ A [ f o A [ e o h-1 ] ] ≈ A [ g o A [ e o h-1 ] ] ] |
109 fe=ge1 = fe=ge' | |
222 | 110 ek=h1 : {d : Obj A} {j : Hom A d a} {eq : A [ A [ f o j ] ≈ A [ g o j ] ]} → |
234 | 111 A [ A [ A [ e o h-1 ] o A [ h o k eqa j eq ] ] ≈ j ] |
222 | 112 ek=h1 {d} {j} {eq} = let open ≈-Reasoning (A) in |
113 begin | |
234 | 114 ( e o h-1 ) o ( h o k eqa j eq ) |
115 ≈↑⟨ assoc ⟩ | |
116 e o ( h-1 o ( h o k eqa j eq ) ) | |
117 ≈⟨ cdr assoc ⟩ | |
118 e o (( h-1 o h) o k eqa j eq ) | |
119 ≈⟨ cdr (car h-1h=1 ) ⟩ | |
253 | 120 e o (id c o k eqa j eq ) |
234 | 121 ≈⟨ cdr idL ⟩ |
122 e o k eqa j eq | |
222 | 123 ≈⟨ ek=h eqa ⟩ |
124 j | |
125 ∎ | |
126 uniqueness1 : {d : Obj A} {h' : Hom A d a} {eq : A [ A [ f o h' ] ≈ A [ g o h' ] ]} {j : Hom A d c'} → | |
234 | 127 A [ A [ A [ e o h-1 ] o j ] ≈ h' ] → |
222 | 128 A [ A [ h o k eqa h' eq ] ≈ j ] |
129 uniqueness1 {d} {h'} {eq} {j} ej=h = let open ≈-Reasoning (A) in | |
130 begin | |
131 h o k eqa h' eq | |
234 | 132 ≈⟨ cdr (uniqueness eqa ( begin |
133 e o ( h-1 o j ) | |
134 ≈⟨ assoc ⟩ | |
135 (e o h-1 ) o j | |
136 ≈⟨ ej=h ⟩ | |
137 h' | |
138 ∎ )) ⟩ | |
139 h o ( h-1 o j ) | |
140 ≈⟨ assoc ⟩ | |
141 (h o h-1 ) o j | |
142 ≈⟨ car hh-1=1 ⟩ | |
253 | 143 id c' o j |
234 | 144 ≈⟨ idL ⟩ |
222 | 145 j |
146 ∎ | |
147 | |
251 | 148 -------------------------------- |
225 | 149 -- |
150 -- If we have two equalizers on c and c', there are isomorphic pair h, h' | |
151 -- | |
152 -- h : c → c' h' : c' → c | |
233
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153 -- e' = h o e |
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154 -- e = h' o e' |
225 | 155 |
233
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156 c-iso-l : { c c' a b : Obj A } {f g : Hom A a b } → {e : Hom A c a } { e' : Hom A c' a } |
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157 ( eqa : Equalizer A e f g) → ( eqa' : Equalizer A e' f g ) |
234 | 158 → ( keqa : Equalizer A (k eqa' e (fe=ge eqa)) (A [ f o e' ]) (A [ g o e' ]) ) |
241 | 159 → Hom A c c' -- should be e' = c-sio-l o e |
234 | 160 c-iso-l {c} {c'} eqa eqa' keqa = equalizer keqa |
226 | 161 |
233
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162 c-iso-r : { c c' a b : Obj A } {f g : Hom A a b } {e : Hom A c a } {e' : Hom A c' a} → ( eqa : Equalizer A e f g) → ( eqa' : Equalizer A e' f g ) |
234 | 163 → ( keqa : Equalizer A (k eqa' e (fe=ge eqa)) (A [ f o e' ]) (A [ g o e' ]) ) |
241 | 164 → Hom A c' c -- e = c-sio-r o e' |
230 | 165 c-iso-r {c} {c'} eqa eqa' keqa = k keqa (id1 A c') ( f1=g1 (fe=ge eqa') (id1 A c') ) |
223 | 166 |
234 | 167 -- e' f |
230 | 168 -- c'----------> a ------->b f e j = g e j |
169 -- ^ g | |
170 -- |k h | |
229
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171 -- | h = e(eqaj) o k jhek = jh (uniqueness) |
230 | 172 -- | |
173 -- c j o (k (eqa ef ef) j ) = id c h = e(eqaj) | |
174 -- | |
175 -- h j e f = h j e g → h = 'j e f | |
229
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176 -- h = j e f -> j = j' |
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177 -- |
228 | 178 |
251 | 179 e←e' : { c c' a b : Obj A } {f g : Hom A a b } → {e : Hom A c a } {e' : Hom A c' a} ( eqa : Equalizer A e f g) → ( eqa' : Equalizer A e' f g ) |
250 | 180 → ( keqa : Equalizer A (k eqa' e (fe=ge eqa)) (A [ f o e' ]) (A [ g o e' ]) ) |
181 → A [ A [ e' o c-iso-l eqa eqa' keqa ] ≈ e ] | |
251 | 182 e←e' {c} {c'} {a} {b} {f} {g} {e} {e'} eqa eqa' keqa = let open ≈-Reasoning (A) in begin |
250 | 183 e' o c-iso-l eqa eqa' keqa |
184 ≈⟨⟩ | |
185 e' o k eqa' e (fe=ge eqa) | |
186 ≈⟨⟩ | |
187 equalizer eqa' o k eqa' e (fe=ge eqa) | |
188 ≈⟨ ek=h eqa' ⟩ | |
189 e | |
190 ∎ | |
191 | |
251 | 192 e'←e : { c c' a b : Obj A } {f g : Hom A a b } → {e : Hom A c a } {e' : Hom A c' a} ( eqa : Equalizer A e f g) → ( eqa' : Equalizer A e' f g ) |
250 | 193 → ( keqa : Equalizer A (k eqa' e (fe=ge eqa)) (A [ f o e' ]) (A [ g o e' ]) ) |
194 → A [ A [ e o c-iso-r eqa eqa' keqa ] ≈ e' ] | |
251 | 195 e'←e {c} {c'} {a} {b} {f} {g} {e} {e'} eqa eqa' keqa = let open ≈-Reasoning (A) in begin |
250 | 196 e o c-iso-r eqa eqa' keqa |
197 ≈⟨⟩ | |
253 | 198 e o k keqa (id c') ( f1=g1 (fe=ge eqa') (id c') ) |
250 | 199 ≈↑⟨ car (ek=h eqa' ) ⟩ |
253 | 200 ( equalizer eqa' o k eqa' e (fe=ge eqa) ) o k keqa (id c') ( f1=g1 (fe=ge eqa') (id c') ) |
250 | 201 ≈⟨⟩ |
253 | 202 ( e' o k eqa' e (fe=ge eqa) ) o k keqa (id c') ( f1=g1 (fe=ge eqa') (id c') ) |
250 | 203 ≈↑⟨ assoc ⟩ |
253 | 204 e' o (( k eqa' e (fe=ge eqa) ) o k keqa (id c') ( f1=g1 (fe=ge eqa') (id c') ) ) |
250 | 205 ≈⟨⟩ |
253 | 206 e' o (equalizer keqa o k keqa (id c') ( f1=g1 (fe=ge eqa') (id c') ) ) |
250 | 207 ≈⟨ cdr ( ek=h keqa ) ⟩ |
253 | 208 e' o id c' |
250 | 209 ≈⟨ idR ⟩ |
210 e' | |
211 ∎ | |
212 | |
253 | 213 -- e←e' e'←e e = e |
214 -- e'←e e←e e' = e' is enough for isomorphism but we can prove l o r = id also. | |
252 | 215 |
234 | 216 c-iso→ : { c c' a b : Obj A } {f g : Hom A a b } → {e : Hom A c a } {e' : Hom A c' a} ( eqa : Equalizer A e f g) → ( eqa' : Equalizer A e' f g ) |
217 → ( keqa : Equalizer A (k eqa' e (fe=ge eqa)) (A [ f o e' ]) (A [ g o e' ]) ) | |
229
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218 → A [ A [ c-iso-l eqa eqa' keqa o c-iso-r eqa eqa' keqa ] ≈ id1 A c' ] |
234 | 219 c-iso→ {c} {c'} {a} {b} {f} {g} eqa eqa' keqa = let open ≈-Reasoning (A) in begin |
229
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220 c-iso-l eqa eqa' keqa o c-iso-r eqa eqa' keqa |
234 | 221 ≈⟨⟩ |
253 | 222 equalizer keqa o k keqa (id c') ( f1=g1 (fe=ge eqa') (id c') ) |
234 | 223 ≈⟨ ek=h keqa ⟩ |
253 | 224 id c' |
229
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225 ∎ |
226 | 226 |
234 | 227 c-iso← : { c c' a b : Obj A } {f g : Hom A a b } → {e : Hom A c a } {e' : Hom A c' a} ( eqa : Equalizer A e f g) → ( eqa' : Equalizer A e' f g ) |
228 → ( keqa : Equalizer A (k eqa' e (fe=ge eqa )) (A [ f o e' ]) (A [ g o e' ]) ) | |
229 → ( keqa' : Equalizer A (k keqa (id1 A c') ( f1=g1 (fe=ge eqa') (id1 A c') )) (A [ f o e ]) (A [ g o e ]) ) | |
230 → A [ A [ c-iso-r eqa eqa' keqa o c-iso-l eqa eqa' keqa ] ≈ id1 A c ] | |
250 | 231 c-iso← {c} {c'} {a} {b} {f} {g} {e} {e'} eqa eqa' keqa keqa' = let open ≈-Reasoning (A) in begin |
234 | 232 c-iso-r eqa eqa' keqa o c-iso-l eqa eqa' keqa |
233 ≈⟨⟩ | |
253 | 234 k keqa (id c') ( f1=g1 (fe=ge eqa') (id c') ) o k eqa' e (fe=ge eqa ) |
234 | 235 ≈⟨⟩ |
236 equalizer keqa' o k eqa' e (fe=ge eqa ) | |
237 ≈⟨ cdr ( begin | |
238 k eqa' e (fe=ge eqa ) | |
239 ≈⟨ uniqueness eqa' ( begin | |
253 | 240 e' o k keqa' (id c) (f1=g1 (fe=ge eqa) (id c)) |
251 | 241 ≈↑⟨ car (e'←e eqa eqa' keqa ) ⟩ |
253 | 242 ( e o equalizer keqa' ) o k keqa' (id c) (f1=g1 (fe=ge eqa) (id c)) |
234 | 243 ≈↑⟨ assoc ⟩ |
253 | 244 e o ( equalizer keqa' o k keqa' (id c) (f1=g1 (fe=ge eqa) (id c))) |
234 | 245 ≈⟨ cdr ( ek=h keqa' ) ⟩ |
253 | 246 e o id c |
234 | 247 ≈⟨ idR ⟩ |
248 e | |
249 ∎ )⟩ | |
253 | 250 k keqa' (id c) ( f1=g1 (fe=ge eqa) (id c) ) |
234 | 251 ∎ )⟩ |
253 | 252 equalizer keqa' o k keqa' (id c) ( f1=g1 (fe=ge eqa) (id c) ) ≈⟨ ek=h keqa' ⟩ |
253 id c | |
234 | 254 ∎ |
255 | |
256 | |
230 | 257 |
251 | 258 -------------------------------- |
225 | 259 ---- |
260 -- | |
261 -- An equalizer satisfies Burroni equations | |
262 -- | |
263 ---- | |
264 | |
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265 lemma-equ1 : {a b c : Obj A} (f g : Hom A a b) → (e : Hom A c a ) → |
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266 ( eqa : {a b c : Obj A} → (f g : Hom A a b) → {e : Hom A c a } → Equalizer A e f g ) |
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267 → Burroni A {c} {a} {b} f g e |
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268 lemma-equ1 {a} {b} {c} f g e eqa = record { |
245 | 269 α = λ {a} {b} {c} f g e → equalizer (eqa {a} {b} {c} f g {e} ) ; -- Hom A c a |
242 | 270 γ = λ {a} {b} {c} {d} f g h → k (eqa f g ) {d} ( A [ h o (equalizer ( eqa (A [ f o h ] ) (A [ g o h ] ))) ] ) |
271 (lemma-equ4 {a} {b} {c} {d} f g h ) ; -- Hom A c d | |
249 | 272 δ = λ {a} {b} {c} e f → k (eqa {a} {b} {c} f f {e} ) (id1 A a) (f1=f1 f); -- Hom A a c |
246
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273 cong-α = λ {a b c e f g g'} eq → cong-α1 {a} {b} {c} {e} {f} {g} {g'} eq ; |
247 | 274 cong-γ = λ {a} {_} {c} {d} {f} {g} {h} {h'} eq → cong-γ1 {a} {c} {d} {f} {g} {h} {h'} eq ; |
245 | 275 cong-δ = λ {a b c e f f'} f=f' → cong-δ1 {a} {b} {c} {e} {f} {f'} f=f' ; |
238
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276 b1 = fe=ge (eqa {a} {b} {c} f g {e}) ; |
226 | 277 b2 = lemma-b2 ; |
278 b3 = lemma-b3 ; | |
230 | 279 b4 = lemma-b4 |
211 | 280 } where |
216 | 281 -- |
282 -- e eqa f g f | |
283 -- c ----------> a ------->b | |
230 | 284 -- ^ g |
285 -- | | |
216 | 286 -- |k₁ = e eqa (f o (e (eqa f g))) (g o (e (eqa f g)))) |
230 | 287 -- | |
216 | 288 -- d |
230 | 289 -- |
290 -- | |
216 | 291 -- e o id1 ≈ e → k e ≈ id |
292 | |
249 | 293 lemma-b3 : {a b d : Obj A} (f : Hom A a b ) { h : Hom A d a } → A [ A [ equalizer (eqa f f ) o k (eqa f f) (id1 A a) (f1=f1 f) ] ≈ id1 A a ] |
240 | 294 lemma-b3 {a} {b} {d} f {h} = let open ≈-Reasoning (A) in |
230 | 295 begin |
253 | 296 equalizer (eqa f f) o k (eqa f f) (id a) (f1=f1 f) |
215 | 297 ≈⟨ ek=h (eqa f f ) ⟩ |
253 | 298 id a |
211 | 299 ∎ |
230 | 300 lemma-equ4 : {a b c d : Obj A} → (f : Hom A a b) → (g : Hom A a b ) → (h : Hom A d a ) → |
233
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301 A [ A [ f o A [ h o equalizer (eqa (A [ f o h ]) (A [ g o h ])) ] ] ≈ A [ g o A [ h o equalizer (eqa (A [ f o h ]) (A [ g o h ])) ] ] ] |
214 | 302 lemma-equ4 {a} {b} {c} {d} f g h = let open ≈-Reasoning (A) in |
212 | 303 begin |
233
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304 f o ( h o equalizer (eqa (f o h) ( g o h ))) |
212 | 305 ≈⟨ assoc ⟩ |
233
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306 (f o h) o equalizer (eqa (f o h) ( g o h )) |
221 | 307 ≈⟨ fe=ge (eqa (A [ f o h ]) (A [ g o h ])) ⟩ |
233
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308 (g o h) o equalizer (eqa (f o h) ( g o h )) |
212 | 309 ≈↑⟨ assoc ⟩ |
233
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310 g o ( h o equalizer (eqa (f o h) ( g o h ))) |
212 | 311 ∎ |
245 | 312 cong-α1 : {a b c : Obj A } → { e : Hom A c a } |
313 → {f g g' : Hom A a b } → A [ g ≈ g' ] → A [ equalizer (eqa {a} {b} {c} f g {e} )≈ equalizer (eqa {a} {b} {c} f g' {e} ) ] | |
314 cong-α1 {a} {b} {c} {e} {f} {g} {g'} eq = let open ≈-Reasoning (A) in refl-hom | |
247 | 315 cong-γ1 : {a c d : Obj A } → {f g : Hom A a b} {h h' : Hom A d a } → A [ h ≈ h' ] → { e : Hom A c a} → |
246
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316 A [ k (eqa f g {e} ) {d} ( A [ h o (equalizer ( eqa (A [ f o h ] ) (A [ g o h ] ) {id1 A d} )) ] ) (lemma-equ4 {a} {b} {c} {d} f g h ) |
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317 ≈ k (eqa f g {e} ) {d} ( A [ h' o (equalizer ( eqa (A [ f o h' ] ) (A [ g o h' ] ) {id1 A d} )) ] ) (lemma-equ4 {a} {b} {c} {d} f g h' ) ] |
247 | 318 cong-γ1 {a} {c} {d} {f} {g} {h} {h'} h=h' {e} = let open ≈-Reasoning (A) in begin |
245 | 319 k (eqa f g ) {d} ( A [ h o (equalizer ( eqa (A [ f o h ] ) (A [ g o h ] ))) ] ) (lemma-equ4 {a} {b} {c} {d} f g h ) |
320 ≈⟨ uniqueness (eqa f g) ( begin | |
248 | 321 e o k (eqa f g ) {d} ( A [ h' o (equalizer ( eqa (A [ f o h' ] ) (A [ g o h' ] ))) ] ) (lemma-equ4 {a} {b} {c} {d} f g h' ) |
322 ≈⟨ ek=h (eqa f g ) ⟩ | |
323 h' o (equalizer ( eqa (A [ f o h' ] ) (A [ g o h' ] ))) | |
324 ≈↑⟨ car h=h' ⟩ | |
325 h o (equalizer ( eqa (A [ f o h' ] ) (A [ g o h' ] ))) | |
245 | 326 ∎ )⟩ |
327 k (eqa f g ) {d} ( A [ h' o (equalizer ( eqa (A [ f o h' ] ) (A [ g o h' ] ))) ] ) (lemma-equ4 {a} {b} {c} {d} f g h' ) | |
328 ∎ | |
249 | 329 cong-δ1 : {a b c : Obj A} {e : Hom A c a } {f f' : Hom A a b} → A [ f ≈ f' ] → A [ k (eqa {a} {b} {c} f f {e} ) (id1 A a) (f1=f1 f) ≈ |
330 k (eqa {a} {b} {c} f' f' {e} ) (id1 A a) (f1=f1 f') ] | |
247 | 331 cong-δ1 {a} {b} {c} {e} {f} {f'} f=f' = let open ≈-Reasoning (A) in |
332 begin | |
253 | 333 k (eqa {a} {b} {c} f f {e} ) (id a) (f1=f1 f) |
247 | 334 ≈⟨ uniqueness (eqa f f) ( begin |
253 | 335 e o k (eqa {a} {b} {c} f' f' {e} ) (id a) (f1=f1 f') |
247 | 336 ≈⟨ ek=h (eqa {a} {b} {c} f' f' {e} ) ⟩ |
253 | 337 id a |
247 | 338 ∎ )⟩ |
253 | 339 k (eqa {a} {b} {c} f' f' {e} ) (id a) (f1=f1 f') |
247 | 340 ∎ |
341 | |
230 | 342 lemma-b2 : {d : Obj A} {h : Hom A d a} → A [ |
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343 A [ equalizer (eqa f g) o k (eqa f g) (A [ h o equalizer (eqa (A [ f o h ]) (A [ g o h ])) ]) (lemma-equ4 {a} {b} {c} f g h) ] |
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344 ≈ A [ h o equalizer (eqa (A [ f o h ]) (A [ g o h ])) ] ] |
226 | 345 lemma-b2 {d} {h} = let open ≈-Reasoning (A) in |
212 | 346 begin |
233
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347 equalizer (eqa f g) o k (eqa f g) (h o equalizer (eqa (f o h) (g o h))) (lemma-equ4 {a} {b} {c} f g h) |
215 | 348 ≈⟨ ek=h (eqa f g) ⟩ |
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349 h o equalizer (eqa (f o h ) ( g o h )) |
212 | 350 ∎ |
230 | 351 |
352 lemma-b4 : {d : Obj A} {j : Hom A d c} → A [ | |
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353 A [ k (eqa f g) (A [ A [ equalizer (eqa f g) o j ] o |
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354 equalizer (eqa (A [ f o A [ equalizer (eqa f g {e}) o j ] ]) (A [ g o A [ equalizer (eqa f g {e} ) o j ] ])) ]) |
233
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355 (lemma-equ4 {a} {b} {c} f g (A [ equalizer (eqa f g) o j ])) o |
249 | 356 k (eqa (A [ f o A [ equalizer (eqa f g) o j ] ]) (A [ f o A [ equalizer (eqa f g) o j ] ])) (id1 A d) (f1=f1 (A [ f o A [ equalizer (eqa f g) o j ] ])) ] |
222 | 357 ≈ j ] |
230 | 358 lemma-b4 {d} {j} = let open ≈-Reasoning (A) in |
215 | 359 begin |
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360 ( k (eqa f g) (( ( equalizer (eqa f g) o j ) o equalizer (eqa (( f o ( equalizer (eqa f g {e}) o j ) )) (( g o ( equalizer (eqa f g {e}) o j ) ))) )) |
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361 (lemma-equ4 {a} {b} {c} f g (( equalizer (eqa f g) o j ))) o |
249 | 362 k (eqa (( f o ( equalizer (eqa f g) o j ) )) (( f o ( equalizer (eqa f g) o j ) ))) (id1 A d) (f1=f1 (( f o ( equalizer (eqa f g) o j ) ))) ) |
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363 ≈⟨ car ((uniqueness (eqa f g) ( begin |
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364 equalizer (eqa f g) o j |
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365 ≈↑⟨ idR ⟩ |
253 | 366 (equalizer (eqa f g) o j ) o id d |
367 ≈⟨⟩ -- here we decide e (fej) (gej)' is id d | |
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368 ((equalizer (eqa f g) o j) o equalizer (eqa (f o equalizer (eqa f g {e}) o j) (g o equalizer (eqa f g {e}) o j))) |
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369 ∎ ))) ⟩ |
249 | 370 j o k (eqa (( f o ( equalizer (eqa f g) o j ) )) (( f o ( equalizer (eqa f g) o j ) ))) (id1 A d) (f1=f1 (( f o ( equalizer (eqa f g) o j ) ))) |
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371 ≈⟨ cdr ((uniqueness (eqa (( f o ( equalizer (eqa f g) o j ) )) (( f o ( equalizer (eqa f g) o j ) ))) ( begin |
253 | 372 equalizer (eqa (f o equalizer (eqa f g {e} ) o j) (f o equalizer (eqa f g {e}) o j)) o id d |
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373 ≈⟨ idR ⟩ |
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374 equalizer (eqa (f o equalizer (eqa f g {e}) o j) (f o equalizer (eqa f g {e}) o j)) |
253 | 375 ≈⟨⟩ -- here we decide e (fej) (fej)' is id d |
376 id d | |
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377 ∎ ))) ⟩ |
253 | 378 j o id d |
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379 ≈⟨ idR ⟩ |
222 | 380 j |
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381 ∎ |
211 | 382 |
251 | 383 -------------------------------- |
384 -- | |
385 -- Bourroni equations gives an Equalizer | |
386 -- | |
211 | 387 |
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388 lemma-equ2 : {a b c : Obj A} (f g : Hom A a b) (e : Hom A c a ) |
245 | 389 → ( bur : Burroni A {c} {a} {b} f g e ) → Equalizer A {c} {a} {b} (α bur f g e) f g |
238
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390 lemma-equ2 {a} {b} {c} f g e bur = record { |
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391 fe=ge = fe=ge1 ; |
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392 k = k1 ; |
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393 ek=h = λ {d} {h} {eq} → ek=h1 {d} {h} {eq} ; |
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394 uniqueness = λ {d} {h} {eq} {k'} ek=h → uniqueness1 {d} {h} {eq} {k'} ek=h |
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395 } where |
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396 k1 : {d : Obj A} (h : Hom A d a) → A [ A [ f o h ] ≈ A [ g o h ] ] → Hom A d c |
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397 k1 {d} h fh=gh = β bur {d} {a} {b} f g h |
245 | 398 fe=ge1 : A [ A [ f o (α bur f g e) ] ≈ A [ g o (α bur f g e) ] ] |
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399 fe=ge1 = b1 bur |
245 | 400 ek=h1 : {d : Obj A} → ∀ {h : Hom A d a} → {eq : A [ A [ f o h ] ≈ A [ g o h ] ] } → A [ A [ (α bur f g e) o k1 {d} h eq ] ≈ h ] |
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401 ek=h1 {d} {h} {eq} = let open ≈-Reasoning (A) in |
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402 begin |
245 | 403 α bur f g e o k1 h eq |
239 | 404 ≈⟨⟩ |
253 | 405 α bur f g e o ( γ bur {a} {b} {c} f g h o δ bur {d} {b} {d} (id d) (f o h) ) |
239 | 406 ≈⟨ assoc ⟩ |
253 | 407 ( α bur f g e o γ bur {a} {b} {c} f g h ) o δ bur {d} {b} {d} (id d) (f o h) |
239 | 408 ≈⟨ car (b2 bur) ⟩ |
253 | 409 ( h o ( α bur ( f o h ) ( g o h ) (id d))) o δ bur {d} {b} {d} (id d) (f o h) |
239 | 410 ≈↑⟨ assoc ⟩ |
253 | 411 h o ((( α bur ( f o h ) ( g o h ) (id d) )) o δ bur {d} {b} {d} (id d) (f o h) ) |
240 | 412 ≈↑⟨ cdr ( car ( cong-α bur eq)) ⟩ |
253 | 413 h o ((( α bur ( f o h ) ( f o h ) (id d)))o δ bur {d} {b} {d} (id d) (f o h) ) |
414 ≈⟨ cdr (b3 bur {d} {b} {d} (f o h) {id d} ) ⟩ | |
415 h o id d | |
240 | 416 ≈⟨ idR ⟩ |
238
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417 h |
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418 ∎ |
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419 uniqueness1 : {d : Obj A} → ∀ {h : Hom A d a} → {eq : A [ A [ f o h ] ≈ A [ g o h ] ] } → {k' : Hom A d c } → |
245 | 420 A [ A [ (α bur f g e) o k' ] ≈ h ] → A [ k1 {d} h eq ≈ k' ] |
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421 uniqueness1 {d} {h} {eq} {k'} ek=h = let open ≈-Reasoning (A) in |
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422 begin |
240 | 423 k1 {d} h eq |
239 | 424 ≈⟨⟩ |
253 | 425 γ bur {a} {b} {c} f g h o δ bur {d} {b} {d} (id d) (f o h) |
240 | 426 ≈↑⟨ car (cong-γ bur {a} {b} {c} {d} ek=h ) ⟩ |
253 | 427 γ bur f g (A [ α bur f g e o k' ]) o δ bur {d} {b} {d} (id d) (f o h) |
245 | 428 ≈↑⟨ cdr (cong-δ bur (resp ek=h refl-hom )) ⟩ |
253 | 429 γ bur f g (A [ α bur f g e o k' ]) o δ bur {d} {b} {d} (id d) ( f o ( α bur f g e o k') ) |
240 | 430 ≈⟨ b4 bur ⟩ |
238
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431 k' |
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432 ∎ |
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433 |
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434 |
225 | 435 -- end |
212 | 436 |
437 | |
438 | |
215 | 439 |
440 |