554 lines
21 KiB
Text
554 lines
21 KiB
Text
-- Copyright (c) 2014 Floris van Doorn. All rights reserved.
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-- Released under Apache 2.0 license as described in the file LICENSE.
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-- Author: Floris van Doorn
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-- category
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import logic.eq logic.connectives
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import data.unit data.sigma data.prod
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import algebra.function
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import logic.axioms.funext
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open eq eq.ops
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inductive category [class] (ob : Type) : Type :=
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mk : Π (mor : ob → ob → Type) (comp : Π⦃A B C : ob⦄, mor B C → mor A B → mor A C)
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(id : Π {A : ob}, mor A A),
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(Π ⦃A B C D : ob⦄ {h : mor C D} {g : mor B C} {f : mor A B},
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comp h (comp g f) = comp (comp h g) f) →
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(Π ⦃A B : ob⦄ {f : mor A B}, comp id f = f) →
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(Π ⦃A B : ob⦄ {f : mor A B}, comp f id = f) →
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category ob
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inductive Category : Type :=
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mk : Π (A : Type), category A → Category
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namespace category
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section
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parameters {ob : Type} {Cat : category ob} {A B C D : ob}
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definition mor : ob → ob → Type := rec (λ mor compose id assoc idr idl, mor) Cat
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definition compose : Π {A B C : ob}, mor B C → mor A B → mor A C :=
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rec (λ mor compose id assoc idr idl, compose) Cat
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definition id : Π {A : ob}, mor A A :=
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rec (λ mor compose id assoc idr idl, id) Cat
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definition ID (A : ob) : mor A A := @id A
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precedence `∘` : 60
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infixr `∘` := compose
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infixl `=>`:25 := mor
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theorem assoc : Π {A B C D : ob} {h : mor C D} {g : mor B C} {f : mor A B},
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h ∘ (g ∘ f) = (h ∘ g) ∘ f :=
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rec (λ mor comp id assoc idr idl, assoc) Cat
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theorem id_left : Π {A B : ob} {f : mor A B}, id ∘ f = f :=
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rec (λ mor comp id assoc idl idr, idl) Cat
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theorem id_right : Π {A B : ob} {f : mor A B}, f ∘ id = f :=
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rec (λ mor comp id assoc idl idr, idr) Cat
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theorem id_compose {A : ob} : (ID A) ∘ id = id :=
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id_left
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theorem left_id_unique (i : mor A A) (H : Π{B} {f : mor B A}, i ∘ f = f) : i = id :=
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calc
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i = i ∘ id : symm id_right
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... = id : H
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theorem right_id_unique (i : mor A A) (H : Π{B} {f : mor A B}, f ∘ i = f) : i = id :=
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calc
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i = id ∘ i : eq.symm id_left
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... = id : H
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inductive is_section {A B : ob} (f : mor A B) : Type :=
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mk : ∀{g}, g ∘ f = id → is_section f
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inductive is_retraction {A B : ob} (f : mor A B) : Type :=
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mk : ∀{g}, f ∘ g = id → is_retraction f
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inductive is_iso {A B : ob} (f : mor A B) : Type :=
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mk : ∀{g}, g ∘ f = id → f ∘ g = id → is_iso f
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definition retraction_of {A B : ob} (f : mor A B) {H : is_section f} : mor B A :=
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is_section.rec (λg h, g) H
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definition section_of {A B : ob} (f : mor A B) {H : is_retraction f} : mor B A :=
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is_retraction.rec (λg h, g) H
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definition inverse {A B : ob} (f : mor A B) {H : is_iso f} : mor B A :=
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is_iso.rec (λg h1 h2, g) H
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postfix `⁻¹` := inverse
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theorem id_is_iso [instance] : is_iso (ID A) :=
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is_iso.mk id_compose id_compose
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theorem inverse_compose {A B : ob} {f : mor A B} {H : is_iso f} : f⁻¹ ∘ f = id :=
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is_iso.rec (λg h1 h2, h1) H
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theorem compose_inverse {A B : ob} {f : mor A B} {H : is_iso f} : f ∘ f⁻¹ = id :=
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is_iso.rec (λg h1 h2, h2) H
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theorem iso_imp_retraction [instance] {A B : ob} (f : mor A B) {H : is_iso f} : is_section f :=
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is_section.mk inverse_compose
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theorem iso_imp_section [instance] {A B : ob} (f : mor A B) {H : is_iso f} : is_retraction f :=
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is_retraction.mk compose_inverse
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theorem retraction_compose {A B : ob} {f : mor A B} {H : is_section f} :
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retraction_of f ∘ f = id :=
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is_section.rec (λg h, h) H
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theorem compose_section {A B : ob} {f : mor A B} {H : is_retraction f} :
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f ∘ section_of f = id :=
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is_retraction.rec (λg h, h) H
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theorem left_inverse_eq_right_inverse {A B : ob} {f : mor A B} {g g' : mor B A}
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(Hl : g ∘ f = id) (Hr : f ∘ g' = id) : g = g' :=
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calc
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g = g ∘ id : symm id_right
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... = g ∘ f ∘ g' : {symm Hr}
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... = (g ∘ f) ∘ g' : assoc
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... = id ∘ g' : {Hl}
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... = g' : id_left
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theorem section_eq_retraction {A B : ob} {f : mor A B}
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(Hl : is_section f) (Hr : is_retraction f) : retraction_of f = section_of f :=
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left_inverse_eq_right_inverse retraction_compose compose_section
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theorem section_retraction_imp_iso {A B : ob} {f : mor A B}
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(Hl : is_section f) (Hr : is_retraction f) : is_iso f :=
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is_iso.mk (subst (section_eq_retraction Hl Hr) retraction_compose) compose_section
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theorem inverse_unique {A B : ob} {f : mor A B} (H H' : is_iso f)
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: @inverse _ _ f H = @inverse _ _ f H' :=
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left_inverse_eq_right_inverse inverse_compose compose_inverse
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theorem retraction_of_id {A : ob} : retraction_of (ID A) = id :=
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left_inverse_eq_right_inverse retraction_compose id_compose
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theorem section_of_id {A : ob} : section_of (ID A) = id :=
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symm (left_inverse_eq_right_inverse id_compose compose_section)
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theorem iso_of_id {A : ob} : ID A⁻¹ = id :=
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left_inverse_eq_right_inverse inverse_compose id_compose
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theorem composition_is_section [instance] {f : mor A B} {g : mor B C}
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(Hf : is_section f) (Hg : is_section g) : is_section (g ∘ f) :=
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is_section.mk
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(calc
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(retraction_of f ∘ retraction_of g) ∘ g ∘ f
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= retraction_of f ∘ retraction_of g ∘ g ∘ f : symm assoc
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... = retraction_of f ∘ (retraction_of g ∘ g) ∘ f : {assoc}
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... = retraction_of f ∘ id ∘ f : {retraction_compose}
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... = retraction_of f ∘ f : {id_left}
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... = id : retraction_compose)
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theorem composition_is_retraction [instance] {f : mor A B} {g : mor B C}
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(Hf : is_retraction f) (Hg : is_retraction g) : is_retraction (g ∘ f) :=
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is_retraction.mk
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(calc
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(g ∘ f) ∘ section_of f ∘ section_of g = g ∘ f ∘ section_of f ∘ section_of g : symm assoc
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... = g ∘ (f ∘ section_of f) ∘ section_of g : {assoc}
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... = g ∘ id ∘ section_of g : {compose_section}
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... = g ∘ section_of g : {id_left}
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... = id : compose_section)
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theorem composition_is_inverse [instance] {f : mor A B} {g : mor B C}
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(Hf : is_iso f) (Hg : is_iso g) : is_iso (g ∘ f) :=
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section_retraction_imp_iso _ _
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definition mono {A B : ob} (f : mor A B) : Prop :=
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∀⦃C⦄ {g h : mor C A}, f ∘ g = f ∘ h → g = h
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definition epi {A B : ob} (f : mor A B) : Prop :=
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∀⦃C⦄ {g h : mor B C}, g ∘ f = h ∘ f → g = h
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theorem section_is_mono {f : mor A B} (H : is_section f) : mono f :=
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λ C g h H,
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calc
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g = id ∘ g : symm id_left
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... = (retraction_of f ∘ f) ∘ g : {symm retraction_compose}
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... = retraction_of f ∘ f ∘ g : symm assoc
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... = retraction_of f ∘ f ∘ h : {H}
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... = (retraction_of f ∘ f) ∘ h : assoc
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... = id ∘ h : {retraction_compose}
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... = h : id_left
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theorem retraction_is_epi {f : mor A B} (H : is_retraction f) : epi f :=
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λ C g h H,
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calc
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g = g ∘ id : symm id_right
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... = g ∘ f ∘ section_of f : {symm compose_section}
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... = (g ∘ f) ∘ section_of f : assoc
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... = (h ∘ f) ∘ section_of f : {H}
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... = h ∘ f ∘ section_of f : symm assoc
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... = h ∘ id : {compose_section}
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... = h : id_right
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end
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section
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definition objects [coercion] (C : Category) : Type
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:= Category.rec (fun c s, c) C
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definition category_instance [instance] (C : Category) : category (objects C)
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:= Category.rec (fun c s, s) C
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end
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end category
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open category
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inductive functor {obC obD : Type} (C : category obC) (D : category obD) : Type :=
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mk : Π (obF : obC → obD) (morF : Π⦃A B : obC⦄, mor A B → mor (obF A) (obF B)),
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(Π ⦃A : obC⦄, morF (ID A) = ID (obF A)) →
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(Π ⦃A B C : obC⦄ {f : mor A B} {g : mor B C}, morF (g ∘ f) = morF g ∘ morF f) →
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functor C D
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inductive Functor (C D : Category) : Type :=
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mk : functor (category_instance C) (category_instance D) → Functor C D
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infixl `⇒`:25 := functor
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namespace functor
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section basic_functor
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parameters {obC obD : Type} {C : category obC} {D : category obD}
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definition object [coercion] (F : C ⇒ D) : obC → obD := rec (λ obF morF Hid Hcomp, obF) F
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definition morphism [coercion] (F : C ⇒ D) : Π{A B : obC}, mor A B → mor (F A) (F B) :=
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rec (λ obF morF Hid Hcomp, morF) F
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theorem respect_id (F : C ⇒ D) : Π {A : obC}, F (ID A) = ID (F A) :=
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rec (λ obF morF Hid Hcomp, Hid) F
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theorem respect_comp (F : C ⇒ D) : Π {a b c : obC} {f : mor a b} {g : mor b c},
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F (g ∘ f) = F g ∘ F f :=
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rec (λ obF morF Hid Hcomp, Hcomp) F
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end basic_functor
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section category_functor
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protected definition compose {obC obD obE : Type} {C : category obC} {D : category obD} {E : category obE}
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(G : D ⇒ E) (F : C ⇒ D) : C ⇒ E :=
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functor.mk
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(λx, G (F x))
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(λ a b f, G (F f))
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(λ a, calc
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G (F (ID a)) = G id : {respect_id F}
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... = id : respect_id G)
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(λ a b c f g, calc
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G (F (g ∘ f)) = G (F g ∘ F f) : {respect_comp F}
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... = G (F g) ∘ G (F f) : respect_comp G)
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precedence `∘∘` : 60
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infixr `∘∘` := compose
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protected theorem assoc {obA obB obC obD : Type} {A : category obA} {B : category obB}
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{C : category obC} {D : category obD} {H : C ⇒ D} {G : B ⇒ C} {F : A ⇒ B} :
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H ∘∘ (G ∘∘ F) = (H ∘∘ G) ∘∘ F :=
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rfl
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-- later check whether we want implicit or explicit arguments here. For the moment, define both
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protected definition id {ob : Type} {C : category ob} : functor C C :=
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mk (λa, a) (λ a b f, f) (λ a, rfl) (λ a b c f g, rfl)
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protected definition ID {ob : Type} (C : category ob) : functor C C := id
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protected definition Id {C : Category} : Functor C C := Functor.mk id
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protected definition iD (C : Category) : Functor C C := Functor.mk id
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protected theorem id_left {obC obB : Type} {B : category obB} {C : category obC} {F : B ⇒ C}
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: id ∘∘ F = F :=
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rec (λ obF morF idF compF, rfl) F
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protected theorem id_right {obC obB : Type} {B : category obB} {C : category obC} {F : B ⇒ C}
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: F ∘∘ id = F :=
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rec (λ obF morF idF compF, rfl) F
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end category_functor
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section Functor
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-- parameters {C D E : Category} (G : Functor D E) (F : Functor C D)
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definition Functor_functor {C D : Category} (F : Functor C D) : functor (category_instance C) (category_instance D) :=
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Functor.rec (λ x, x) F
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protected definition Compose {C D E : Category} (G : Functor D E) (F : Functor C D) : Functor C E :=
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Functor.mk (compose (Functor_functor G) (Functor_functor F))
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-- namespace Functor
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precedence `∘∘` : 60
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infixr `∘∘` := Compose
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-- end Functor
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protected definition Assoc {A B C D : Category} {H : Functor C D} {G : Functor B C} {F : Functor A B}
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: H ∘∘ (G ∘∘ F) = (H ∘∘ G) ∘∘ F :=
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rfl
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protected theorem Id_left {B : Category} {C : Category} {F : Functor B C}
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: Id ∘∘ F = F :=
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Functor.rec (λ f, subst id_left rfl) F
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protected theorem Id_right {B : Category} {C : Category} {F : Functor B C}
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: F ∘∘ Id = F :=
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Functor.rec (λ f, subst id_right rfl) F
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end Functor
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end functor
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open functor
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inductive natural_transformation {obC obD : Type} {C : category obC} {D : category obD}
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(F G : functor C D) : Type :=
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mk : Π (η : Π(a : obC), mor (object F a) (object G a)), (Π{a b : obC} (f : mor a b), morphism G f ∘ η a = η b ∘ morphism F f)
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→ natural_transformation F G
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-- inductive Natural_transformation {C D : Category} (F G : Functor C D) : Type :=
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-- mk : natural_transformation (Functor_functor F) (Functor_functor G) → Natural_transformation F G
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infixl `==>`:25 := natural_transformation
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namespace natural_transformation
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section
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parameters {obC obD : Type} {C : category obC} {D : category obD} {F G : C ⇒ D}
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definition natural_map [coercion] (η : F ==> G) :
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Π(a : obC), mor (object F a) (object G a) :=
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rec (λ x y, x) η
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definition naturality (η : F ==> G) :
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Π{a b : obC} (f : mor a b), morphism G f ∘ η a = η b ∘ morphism F f :=
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rec (λ x y, y) η
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end
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section
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parameters {obC obD : Type} {C : category obC} {D : category obD} {F G H : C ⇒ D}
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protected definition compose (η : G ==> H) (θ : F ==> G) : F ==> H :=
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natural_transformation.mk
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(λ a, η a ∘ θ a)
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(λ a b f,
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calc
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morphism H f ∘ (η a ∘ θ a) = (morphism H f ∘ η a) ∘ θ a : assoc
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... = (η b ∘ morphism G f) ∘ θ a : {naturality η f}
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... = η b ∘ (morphism G f ∘ θ a) : symm assoc
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... = η b ∘ (θ b ∘ morphism F f) : {naturality θ f}
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... = (η b ∘ θ b) ∘ morphism F f : assoc)
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end
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precedence `∘n` : 60
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infixr `∘n` := compose
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section
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protected theorem assoc {obC obD : Type} {C : category obC} {D : category obD} {F₄ F₃ F₂ F₁ : C ⇒ D} {η₃ : F₃ ==> F₄} {η₂ : F₂ ==> F₃} {η₁ : F₁ ==> F₂} : η₃ ∘n (η₂ ∘n η₁) = (η₃ ∘n η₂) ∘n η₁ :=
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congr_arg2_dep mk (funext (take x, assoc)) proof_irrel
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--TODO: check whether some of the below identities are superfluous
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protected definition id {obC obD : Type} {C : category obC} {D : category obD} {F : C ⇒ D}
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: natural_transformation F F :=
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mk (λa, id) (λa b f, id_right ⬝ symm id_left)
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protected definition ID {obC obD : Type} {C : category obC} {D : category obD} (F : C ⇒ D)
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: natural_transformation F F := id
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-- protected definition Id {C D : Category} {F : Functor C D} : Natural_transformation F F :=
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-- Natural_transformation.mk id
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-- protected definition iD {C D : Category} (F : Functor C D) : Natural_transformation F F :=
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-- Natural_transformation.mk id
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protected theorem id_left {obC obD : Type} {C : category obC} {D : category obD} {F G : C ⇒ D}
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{η : F ==> G} : natural_transformation.compose id η = η :=
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rec (λf H, congr_arg2_dep mk (funext (take x, id_left)) proof_irrel) η
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protected theorem id_right {obC obD : Type} {C : category obC} {D : category obD} {F G : C ⇒ D}
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{η : F ==> G} : natural_transformation.compose η id = η :=
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rec (λf H, congr_arg2_dep mk (funext (take x, id_right)) proof_irrel) η
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end
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end natural_transformation
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-- examples of categories / basic constructions (TODO: move to separate file)
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open functor
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namespace category
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section
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open unit
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definition one [instance] : category unit :=
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category.mk (λa b, unit) (λ a b c f g, star) (λ a, star) (λ a b c d f g h, unit.equal _ _)
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(λ a b f, unit.equal _ _) (λ a b f, unit.equal _ _)
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end
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section
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parameter {ob : Type}
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definition opposite (C : category ob) : category ob :=
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category.mk (λa b, mor b a) (λ a b c f g, g ∘ f) (λ a, id) (λ a b c d f g h, symm assoc)
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(λ a b f, id_right) (λ a b f, id_left)
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precedence `∘op` : 60
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infixr `∘op` := @compose _ (opposite _) _ _ _
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parameters {C : category ob} {a b c : ob}
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theorem compose_op {f : @mor ob C a b} {g : mor b c} : f ∘op g = g ∘ f :=
|
||
rfl
|
||
|
||
theorem op_op {C : category ob} : opposite (opposite C) = C :=
|
||
category.rec (λ mor comp id assoc idl idr, refl (mk _ _ _ _ _ _)) C
|
||
end
|
||
|
||
definition Opposite (C : Category) : Category :=
|
||
Category.mk (objects C) (opposite (category_instance C))
|
||
|
||
|
||
section
|
||
definition type_category : category Type :=
|
||
mk (λA B, A → B) (λ a b c, function.compose) (λ a, function.id)
|
||
(λ a b c d h g f, symm (function.compose_assoc h g f))
|
||
(λ a b f, function.compose_id_left f) (λ a b f, function.compose_id_right f)
|
||
end
|
||
|
||
section cat_Cat
|
||
|
||
definition Cat : category Category :=
|
||
mk (λ a b, Functor a b) (λ a b c g f, functor.Compose g f) (λ a, functor.Id)
|
||
(λ a b c d h g f, functor.Assoc) (λ a b f, functor.Id_left)
|
||
(λ a b f, functor.Id_right)
|
||
|
||
end cat_Cat
|
||
|
||
section functor_category
|
||
parameters {obC obD : Type} (C : category obC) (D : category obD)
|
||
definition functor_category : category (functor C D) :=
|
||
mk (λa b, natural_transformation a b)
|
||
(λ a b c g f, natural_transformation.compose g f)
|
||
(λ a, natural_transformation.id)
|
||
(λ a b c d h g f, natural_transformation.assoc)
|
||
(λ a b f, natural_transformation.id_left)
|
||
(λ a b f, natural_transformation.id_right)
|
||
end functor_category
|
||
|
||
|
||
section slice
|
||
open sigma
|
||
|
||
definition slice {ob : Type} (C : category ob) (c : ob) : category (Σ(b : ob), mor b c) :=
|
||
mk (λa b, Σ(g : mor (dpr1 a) (dpr1 b)), dpr2 b ∘ g = dpr2 a)
|
||
(λ a b c g f, dpair (dpr1 g ∘ dpr1 f)
|
||
(show dpr2 c ∘ (dpr1 g ∘ dpr1 f) = dpr2 a,
|
||
proof
|
||
calc
|
||
dpr2 c ∘ (dpr1 g ∘ dpr1 f) = (dpr2 c ∘ dpr1 g) ∘ dpr1 f : assoc
|
||
... = dpr2 b ∘ dpr1 f : {dpr2 g}
|
||
... = dpr2 a : {dpr2 f}
|
||
qed))
|
||
(λ a, dpair id id_right)
|
||
(λ a b c d h g f, dpair_eq assoc proof_irrel)
|
||
(λ a b f, sigma.equal id_left proof_irrel)
|
||
(λ a b f, sigma.equal id_right proof_irrel)
|
||
-- We give proof_irrel instead of rfl, to give the unifier an easier time
|
||
end slice
|
||
|
||
section coslice
|
||
open sigma
|
||
|
||
definition coslice {ob : Type} (C : category ob) (c : ob) : category (Σ(b : ob), mor c b) :=
|
||
mk (λa b, Σ(g : mor (dpr1 a) (dpr1 b)), g ∘ dpr2 a = dpr2 b)
|
||
(λ a b c g f, dpair (dpr1 g ∘ dpr1 f)
|
||
(show (dpr1 g ∘ dpr1 f) ∘ dpr2 a = dpr2 c,
|
||
proof
|
||
calc
|
||
(dpr1 g ∘ dpr1 f) ∘ dpr2 a = dpr1 g ∘ (dpr1 f ∘ dpr2 a): symm assoc
|
||
... = dpr1 g ∘ dpr2 b : {dpr2 f}
|
||
... = dpr2 c : {dpr2 g}
|
||
qed))
|
||
(λ a, dpair id id_left)
|
||
(λ a b c d h g f, dpair_eq assoc proof_irrel)
|
||
(λ a b f, sigma.equal id_left proof_irrel)
|
||
(λ a b f, sigma.equal id_right proof_irrel)
|
||
|
||
-- theorem slice_coslice_opp {ob : Type} (C : category ob) (c : ob) :
|
||
-- coslice C c = opposite (slice (opposite C) c) :=
|
||
-- sorry
|
||
end coslice
|
||
|
||
section product
|
||
open prod
|
||
definition product {obC obD : Type} (C : category obC) (D : category obD)
|
||
: category (obC × obD) :=
|
||
mk (λa b, mor (pr1 a) (pr1 b) × mor (pr2 a) (pr2 b))
|
||
(λ a b c g f, (pr1 g ∘ pr1 f , pr2 g ∘ pr2 f) )
|
||
(λ a, (id,id))
|
||
(λ a b c d h g f, pair_eq assoc assoc )
|
||
(λ a b f, prod.equal id_left id_left )
|
||
(λ a b f, prod.equal id_right id_right)
|
||
|
||
end product
|
||
|
||
section arrow
|
||
open sigma eq.ops
|
||
-- theorem concat_commutative_squares {ob : Type} {C : category ob} {a1 a2 a3 b1 b2 b3 : ob}
|
||
-- {f1 : a1 => b1} {f2 : a2 => b2} {f3 : a3 => b3} {g2 : a2 => a3} {g1 : a1 => a2}
|
||
-- {h2 : b2 => b3} {h1 : b1 => b2} (H1 : f2 ∘ g1 = h1 ∘ f1) (H2 : f3 ∘ g2 = h2 ∘ f2)
|
||
-- : f3 ∘ (g2 ∘ g1) = (h2 ∘ h1) ∘ f1 :=
|
||
-- calc
|
||
-- f3 ∘ (g2 ∘ g1) = (f3 ∘ g2) ∘ g1 : assoc
|
||
-- ... = (h2 ∘ f2) ∘ g1 : {H2}
|
||
-- ... = h2 ∘ (f2 ∘ g1) : symm assoc
|
||
-- ... = h2 ∘ (h1 ∘ f1) : {H1}
|
||
-- ... = (h2 ∘ h1) ∘ f1 : assoc
|
||
|
||
-- definition arrow {ob : Type} (C : category ob) : category (Σ(a b : ob), mor a b) :=
|
||
-- mk (λa b, Σ(g : mor (dpr1 a) (dpr1 b)) (h : mor (dpr2' a) (dpr2' b)),
|
||
-- dpr3 b ∘ g = h ∘ dpr3 a)
|
||
-- (λ a b c g f, dpair (dpr1 g ∘ dpr1 f) (dpair (dpr2' g ∘ dpr2' f) (concat_commutative_squares (dpr3 f) (dpr3 g))))
|
||
-- (λ a, dpair id (dpair id (id_right ⬝ (symm id_left))))
|
||
-- (λ a b c d h g f, dtrip_eq2 assoc assoc proof_irrel)
|
||
-- (λ a b f, trip.equal2 id_left id_left proof_irrel)
|
||
-- (λ a b f, trip.equal2 id_right id_right proof_irrel)
|
||
|
||
definition arrow_obs (ob : Type) (C : category ob) :=
|
||
Σ(a b : ob), mor a b
|
||
|
||
definition src {ob : Type} {C : category ob} (a : arrow_obs ob C) : ob :=
|
||
dpr1 a
|
||
|
||
definition dst {ob : Type} {C : category ob} (a : arrow_obs ob C) : ob :=
|
||
dpr2' a
|
||
|
||
definition to_mor {ob : Type} {C : category ob} (a : arrow_obs ob C) : mor (src a) (dst a) :=
|
||
dpr3 a
|
||
|
||
definition arrow_mor (ob : Type) (C : category ob) (a b : arrow_obs ob C) : Type :=
|
||
Σ (g : mor (src a) (src b)) (h : mor (dst a) (dst b)), to_mor b ∘ g = h ∘ to_mor a
|
||
|
||
definition mor_src {ob : Type} {C : category ob} {a b : arrow_obs ob C} (m : arrow_mor ob C a b) : mor (src a) (src b) :=
|
||
dpr1 m
|
||
|
||
definition mor_dst {ob : Type} {C : category ob} {a b : arrow_obs ob C} (m : arrow_mor ob C a b) : mor (dst a) (dst b) :=
|
||
dpr2' m
|
||
|
||
definition commute {ob : Type} {C : category ob} {a b : arrow_obs ob C} (m : arrow_mor ob C a b) :
|
||
to_mor b ∘ (mor_src m) = (mor_dst m) ∘ to_mor a :=
|
||
dpr3 m
|
||
|
||
definition arrow (ob : Type) (C : category ob) : category (arrow_obs ob C) :=
|
||
mk (λa b, arrow_mor ob C a b)
|
||
(λ a b c g f, dpair (mor_src g ∘ mor_src f) (dpair (mor_dst g ∘ mor_dst f)
|
||
(show to_mor c ∘ (mor_src g ∘ mor_src f) = (mor_dst g ∘ mor_dst f) ∘ to_mor a,
|
||
proof
|
||
calc
|
||
to_mor c ∘ (mor_src g ∘ mor_src f) = (to_mor c ∘ mor_src g) ∘ mor_src f : assoc
|
||
... = (mor_dst g ∘ to_mor b) ∘ mor_src f : {commute g}
|
||
... = mor_dst g ∘ (to_mor b ∘ mor_src f) : symm assoc
|
||
... = mor_dst g ∘ (mor_dst f ∘ to_mor a) : {commute f}
|
||
... = (mor_dst g ∘ mor_dst f) ∘ to_mor a : assoc
|
||
qed)
|
||
))
|
||
(λ a, dpair id (dpair id (id_right ⬝ (symm id_left))))
|
||
(λ a b c d h g f, dtrip_eq_ndep assoc assoc proof_irrel)
|
||
(λ a b f, trip.equal_ndep id_left id_left proof_irrel)
|
||
(λ a b f, trip.equal_ndep id_right id_right proof_irrel)
|
||
|
||
end arrow
|
||
|
||
-- definition foo
|
||
-- : category (sorry) :=
|
||
-- mk (λa b, sorry)
|
||
-- (λ a b c g f, sorry)
|
||
-- (λ a, sorry)
|
||
-- (λ a b c d h g f, sorry)
|
||
-- (λ a b f, sorry)
|
||
-- (λ a b f, sorry)
|
||
|
||
end category
|