532 lines
21 KiB
Text
532 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 (hom : ob → ob → Type) (comp : Π⦃a b c : ob⦄, hom b c → hom a b → hom a c)
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(id : Π {a : ob}, hom a a),
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(Π ⦃a b c d : ob⦄ {h : hom c d} {g : hom b c} {f : hom 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 : hom a b}, comp id f = f) →
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(Π ⦃a b : ob⦄ {f : hom a b}, comp f id = f) →
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category ob
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inductive Category : Type := mk : Π (ob : Type), category ob → Category
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namespace category
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section
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parameters {ob : Type} {C : category ob}
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variables {a b c d : ob}
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definition hom : ob → ob → Type := rec (λ hom compose id assoc idr idl, hom) C
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definition compose : Π {a b c : ob}, hom b c → hom a b → hom a c :=
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rec (λ hom compose id assoc idr idl, compose) C
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definition id : Π {a : ob}, hom a a := rec (λ hom compose id assoc idr idl, id) C
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definition ID : Π (a : ob), hom a a := @id
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precedence `∘` : 60
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infixr `∘` := compose
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infixl `=>`:25 := hom
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variables {h : hom c d} {g : hom b c} {f : hom a b} {i : hom a a}
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theorem assoc : Π ⦃a b c d : ob⦄ (h : hom c d) (g : hom b c) (f : hom a b),
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h ∘ (g ∘ f) = (h ∘ g) ∘ f :=
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rec (λ hom comp id assoc idr idl, assoc) C
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theorem id_left : Π ⦃a b : ob⦄ (f : hom a b), id ∘ f = f :=
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rec (λ hom comp id assoc idl idr, idl) C
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theorem id_right : Π ⦃a b : ob⦄ (f : hom a b), f ∘ id = f :=
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rec (λ hom comp id assoc idl idr, idr) C
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theorem id_compose (a : ob) : (ID a) ∘ id = id := !id_left
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theorem left_id_unique (H : Π{b} {f : hom 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 (H : Π{b} {f : hom 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 [class] (f : hom a b) : Type := mk : ∀{g}, g ∘ f = id → is_section f
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inductive is_retraction [class] (f : hom a b) : Type := mk : ∀{g}, f ∘ g = id → is_retraction f
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inductive is_iso [class] (f : hom a b) : Type := mk : ∀{g}, g ∘ f = id → f ∘ g = id → is_iso f
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definition retraction_of (f : hom a b) {H : is_section f} : hom b a :=
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is_section.rec (λg h, g) H
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definition section_of (f : hom a b) {H : is_retraction f} : hom b a :=
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is_retraction.rec (λg h, g) H
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definition inverse (f : hom a b) {H : is_iso f} : hom 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 (f : hom 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 (f : hom 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] (f : hom 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] (f : hom 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 (f : hom a b) {H : is_section f} : retraction_of f ∘ f = id :=
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is_section.rec (λg h, h) H
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theorem compose_section (f : hom a b) {H : is_retraction f} : 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 {f : hom a b} {g g' : hom 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 {Hl : is_section f} {Hr : is_retraction f} :
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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 {Hl : is_section f} {Hr : is_retraction f} : is_iso f :=
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is_iso.mk (subst section_eq_retraction !retraction_compose) !compose_section
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theorem inverse_unique (H H' : is_iso f) : @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 : 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 : 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 : 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] {Hf : is_section f} {Hg : is_section g}
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: 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] (Hf : is_retraction f) (Hg : is_retraction g)
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: 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] (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 (f : hom a b) : Prop := ∀⦃c⦄ {g h : hom c a}, f ∘ g = f ∘ h → g = h
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definition epi (f : hom a b) : Prop := ∀⦃c⦄ {g h : hom b c}, g ∘ f = h ∘ f → g = h
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theorem section_is_mono (f : hom 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 : hom 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) (homF : Π⦃a b : obC⦄, hom a b → hom (obF a) (obF b)),
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(Π ⦃a : obC⦄, homF (ID a) = ID (obF a)) →
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(Π ⦃a b c : obC⦄ {g : hom b c} {f : hom a b}, homF (g ∘ f) = homF g ∘ homF 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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variables {obC obD obE : Type} {C : category obC} {D : category obD} {E : category obE}
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definition object [coercion] (F : C ⇒ D) : obC → obD := rec (λ obF homF Hid Hcomp, obF) F
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definition morphism [coercion] (F : C ⇒ D) : Π{a b : obC}, hom a b → hom (F a) (F b) :=
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rec (λ obF homF Hid Hcomp, homF) F
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theorem respect_id (F : C ⇒ D) : Π (a : obC), F (ID a) = id :=
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rec (λ obF homF Hid Hcomp, Hid) F
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variable G : D ⇒ E
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check respect_id G
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theorem respect_comp (F : C ⇒ D) : Π ⦃a b c : obC⦄ (g : hom b c) (f : hom a b),
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F (g ∘ f) = F g ∘ F f :=
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rec (λ obF homF Hid Hcomp, Hcomp) F
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protected definition compose (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 a}
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... = id : respect_id G (F a))
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(λ a b c g f, calc
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G (F (g ∘ f)) = G (F g ∘ F f) : {respect_comp F g f}
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... = G (F g) ∘ G (F f) : respect_comp G (F g) (F f))
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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 (F : C ⇒ D) : id ∘∘ F = F := rec (λ obF homF idF compF, rfl) F
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protected theorem id_right (F : C ⇒ D) : F ∘∘ id = F := rec (λ obF homF idF compF, rfl) F
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end basic_functor
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section Functor
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variables {C₁ C₂ C₃ C₄: Category} --(G : Functor D E) (F : Functor C D)
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definition Functor_functor (F : Functor C₁ C₂) :
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functor (category_instance C₁) (category_instance C₂) :=
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Functor.rec (λ x, x) F
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protected definition Compose (G : Functor C₂ C₃) (F : Functor C₁ C₂) : Functor C₁ C₃ :=
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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 (H : Functor C₃ C₄) (G : Functor C₂ C₃) (F : Functor C₁ C₂)
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: H ∘∘ (G ∘∘ F) = (H ∘∘ G) ∘∘ F :=
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rfl
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protected theorem Id_left (F : Functor C₁ C₂) : Id ∘∘ F = F :=
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Functor.rec (λ f, subst !id_left rfl) F
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protected theorem Id_right {F : Functor C₁ C₂} : 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), hom (object F a) (object G a)), (Π{a b : obC} (f : hom 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), hom (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 : hom 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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variables {obC obD : Type} {C : category obC} {D : category obD} {F₁ F₂ F₃ F₄ : C ⇒ D}
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protected theorem assoc (η₃ : F₃ ==> F₄) (η₂ : F₂ ==> F₃) (η₁ : F₁ ==> F₂) :
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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 (η : F₁ ==> F₂) : 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 (η : F₁ ==> F₂) : 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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open unit
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definition big_one_test (A : Type) : category A :=
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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, hom 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 : @hom ob C a b} {g : hom b c} : f ∘op g = g ∘ f :=
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rfl
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theorem op_op {C : category ob} : opposite (opposite C) = C :=
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category.rec (λ hom comp id assoc idl idr, refl (mk _ _ _ _ _ _)) C
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end
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definition Opposite (C : Category) : Category :=
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Category.mk (objects C) (opposite (category_instance C))
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section
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definition type_category : category Type :=
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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_C
|
||
|
||
definition C : 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_C
|
||
|
||
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), hom b c) :=
|
||
mk (λa b, Σ(g : hom (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), hom c b) :=
|
||
mk (λa b, Σ(g : hom (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, hom (pr1 a) (pr1 b) × hom (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), hom a b) :=
|
||
-- mk (λa b, Σ(g : hom (dpr1 a) (dpr1 b)) (h : hom (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)
|
||
|
||
variables {ob : Type} {C : category ob}
|
||
protected definition arrow_obs (ob : Type) (C : category ob) := Σ(a b : ob), hom a b
|
||
variables {a b : arrow_obs ob C}
|
||
protected definition src (a : arrow_obs ob C) : ob := dpr1 a
|
||
protected definition dst (a : arrow_obs ob C) : ob := dpr2' a
|
||
protected definition to_hom (a : arrow_obs ob C) : hom (src a) (dst a) := dpr3 a
|
||
|
||
protected definition arrow_hom (a b : arrow_obs ob C) : Type :=
|
||
Σ (g : hom (src a) (src b)) (h : hom (dst a) (dst b)), to_hom b ∘ g = h ∘ to_hom a
|
||
|
||
protected definition hom_src (m : arrow_hom a b) : hom (src a) (src b) := dpr1 m
|
||
protected definition hom_dst (m : arrow_hom a b) : hom (dst a) (dst b) := dpr2' m
|
||
protected definition commute (m : arrow_hom a b) : to_hom b ∘ (hom_src m) = (hom_dst m) ∘ to_hom a
|
||
:= dpr3 m
|
||
|
||
definition arrow (ob : Type) (C : category ob) : category (arrow_obs ob C) :=
|
||
mk (λa b, arrow_hom a b)
|
||
(λ a b c g f, dpair (hom_src g ∘ hom_src f) (dpair (hom_dst g ∘ hom_dst f)
|
||
(show to_hom c ∘ (hom_src g ∘ hom_src f) = (hom_dst g ∘ hom_dst f) ∘ to_hom a,
|
||
proof
|
||
calc
|
||
to_hom c ∘ (hom_src g ∘ hom_src f) = (to_hom c ∘ hom_src g) ∘ hom_src f : !assoc
|
||
... = (hom_dst g ∘ to_hom b) ∘ hom_src f : {commute g}
|
||
... = hom_dst g ∘ (to_hom b ∘ hom_src f) : symm !assoc
|
||
... = hom_dst g ∘ (hom_dst f ∘ to_hom a) : {commute f}
|
||
... = (hom_dst g ∘ hom_dst f) ∘ to_hom 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
|