{-# OPTIONS --safe #-}
module Cubical.Categories.Constructions.BinProduct where
open import Cubical.Foundations.HLevels
open import Cubical.Foundations.Prelude
open import Cubical.Data.Sigma
open import Cubical.Categories.Category.Base
open import Cubical.Categories.Functor.Base
open import Cubical.Categories.Functors.Constant
private
variable
ℓA ℓA' ℓB ℓB' ℓC ℓC' ℓD ℓD' ℓE ℓE' : Level
open Category
_×C_ : (C : Category ℓC ℓC') → (D : Category ℓD ℓD')
→ Category (ℓ-max ℓC ℓD) (ℓ-max ℓC' ℓD')
(C ×C D) .ob = (ob C) × (ob D)
(C ×C D) .Hom[_,_] (c , d) (c' , d') = (C [ c , c' ]) × (D [ d , d' ])
(C ×C D) .id = (id C , id D)
(C ×C D) ._⋆_ _ _ = (_ ⋆⟨ C ⟩ _ , _ ⋆⟨ D ⟩ _)
(C ×C D) .⋆IdL _ = ≡-× (⋆IdL C _) (⋆IdL D _)
(C ×C D) .⋆IdR _ = ≡-× (⋆IdR C _) (⋆IdR D _)
(C ×C D) .⋆Assoc _ _ _ = ≡-× (⋆Assoc C _ _ _) (⋆Assoc D _ _ _)
(C ×C D) .isSetHom = isSet× (isSetHom C) (isSetHom D)
infixr 5 _×C_
open Functor
Fst : (C : Category ℓC ℓC') → (D : Category ℓD ℓD') → Functor (C ×C D) C
F-ob (Fst C D) = fst
F-hom (Fst C D) = fst
F-id (Fst C D) = refl
F-seq (Fst C D) _ _ = refl
Snd : (C : Category ℓC ℓC') → (D : Category ℓD ℓD') → Functor (C ×C D) D
F-ob (Snd C D) = snd
F-hom (Snd C D) = snd
F-id (Snd C D) = refl
F-seq (Snd C D) _ _ = refl
module _ where
private
variable
A : Category ℓA ℓA'
B : Category ℓB ℓB'
C : Category ℓC ℓC'
D : Category ℓD ℓD'
E : Category ℓE ℓE'
open Functor
_,F_ : Functor C D → Functor C E → Functor C (D ×C E)
(G ,F H) .F-ob a = (G ⟅ a ⟆ , H ⟅ a ⟆)
(G ,F H) .F-hom g = (G ⟪ g ⟫ , H ⟪ g ⟫)
(G ,F H) .F-id = ≡-× (G .F-id) (H .F-id)
(G ,F H) .F-seq _ _ = ≡-× (G .F-seq _ _) (H .F-seq _ _)
_×F_ : Functor A C → Functor B D → Functor (A ×C B) (C ×C D)
_×F_ {A = A} {B = B} G H = G ∘F Fst A B ,F H ∘F Snd A B
Δ : ∀ (C : Category ℓC ℓC') → Functor C (C ×C C)
Δ C = Id ,F Id
Sym : {C : Category ℓC ℓC'}{D : Category ℓD ℓD'} → Functor (C ×C D) (D ×C C)
Sym {C = C}{D = D} = Snd C D ,F Fst C D
module _ (C : Category ℓC ℓC')
(D : Category ℓD ℓD') where
open Functor
module _ (E : Category ℓE ℓE') where
×C-assoc : Functor (C ×C (D ×C E)) ((C ×C D) ×C E)
×C-assoc .F-ob (c , (d , e)) = ((c , d), e)
×C-assoc .F-hom (f , (g , h)) = ((f , g), h)
×C-assoc .F-id = refl
×C-assoc .F-seq _ _ = refl
linj : (d : ob D) → Functor C (C ×C D)
linj d = Id ,F Constant C D d
rinj : (c : ob C) → Functor D (C ×C D)
rinj c = Constant D C c ,F Id
open isIso
CatIso× : {x y : C .ob}{z w : D .ob} → CatIso C x y → CatIso D z w → CatIso (C ×C D) (x , z) (y , w)
CatIso× f g .fst = f .fst , g .fst
CatIso× f g .snd .inv = f .snd .inv , g .snd .inv
CatIso× f g .snd .sec i = f .snd .sec i , g .snd .sec i
CatIso× f g .snd .ret i = f .snd .ret i , g .snd .ret i