94 lines
3.4 KiB
Text
94 lines
3.4 KiB
Text
/-
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Copyright (c) 2015 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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Authors: Floris van Doorn, Jakob von Raumer
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Category of hsets
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-/
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import ..category types.equiv
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--open eq is_trunc sigma equiv iso is_equiv
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open eq category equiv iso is_equiv is_trunc function sigma
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namespace category
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definition precategory_hset [reducible] : precategory hset :=
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precategory.mk (λx y : hset, x → y)
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(λx y z g f a, g (f a))
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(λx a, a)
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(λx y z w h g f, eq_of_homotopy (λa, idp))
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(λx y f, eq_of_homotopy (λa, idp))
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(λx y f, eq_of_homotopy (λa, idp))
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definition Precategory_hset [reducible] : Precategory :=
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Precategory.mk hset precategory_hset
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namespace set
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local attribute is_equiv_subtype_eq [instance]
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definition iso_of_equiv {A B : Precategory_hset} (f : A ≃ B) : A ≅ B :=
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iso.MK (to_fun f)
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(equiv.to_inv f)
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(eq_of_homotopy (left_inv (to_fun f)))
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(eq_of_homotopy (right_inv (to_fun f)))
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definition equiv_of_iso {A B : Precategory_hset} (f : A ≅ B) : A ≃ B :=
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equiv.MK (to_hom f)
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(iso.to_inv f)
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(ap10 (right_inverse (to_hom f)))
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(ap10 (left_inverse (to_hom f)))
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definition is_equiv_iso_of_equiv (A B : Precategory_hset) : is_equiv (@iso_of_equiv A B) :=
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adjointify _ (λf, equiv_of_iso f)
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(λf, proof iso_eq idp qed)
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(λf, equiv_eq idp)
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local attribute is_equiv_iso_of_equiv [instance]
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open sigma.ops
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definition subtype_eq_inv {A : Type} {B : A → Type} [H : Πa, is_hprop (B a)] (u v : Σa, B a)
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: u = v → u.1 = v.1 :=
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(subtype_eq u v)⁻¹ᶠ
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local attribute subtype_eq_inv [reducible]
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definition is_equiv_subtype_eq_inv {A : Type} {B : A → Type} [H : Πa, is_hprop (B a)] (u v : Σa, B a)
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: is_equiv (subtype_eq_inv u v) :=
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_
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definition iso_of_eq_eq_compose (A B : hset) : @iso_of_eq _ _ A B =
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@iso_of_equiv A B ∘ @equiv_of_eq A B ∘ subtype_eq_inv _ _ ∘
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@ap _ _ (to_fun (trunctype.sigma_char 0)) A B :=
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eq_of_homotopy (λp, eq.rec_on p idp)
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definition equiv_equiv_iso (A B : Precategory_hset) : (A ≃ B) ≃ (A ≅ B) :=
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equiv.MK (λf, iso_of_equiv f)
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(λf, equiv.MK (to_hom f)
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(iso.to_inv f)
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(ap10 (right_inverse (to_hom f)))
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(ap10 (left_inverse (to_hom f))))
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(λf, iso_eq idp)
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(λf, equiv_eq idp)
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definition equiv_eq_iso (A B : Precategory_hset) : (A ≃ B) = (A ≅ B) :=
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ua !equiv_equiv_iso
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definition is_univalent_hset (A B : Precategory_hset) : is_equiv (iso_of_eq : A = B → A ≅ B) :=
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have H : is_equiv (@iso_of_equiv A B ∘ @equiv_of_eq A B ∘ subtype_eq_inv _ _ ∘
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@ap _ _ (to_fun (trunctype.sigma_char 0)) A B), from
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@is_equiv_compose _ _ _ _ _
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(@is_equiv_compose _ _ _ _ _
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(@is_equiv_compose _ _ _ _ _
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_
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(@is_equiv_subtype_eq_inv _ _ _ _ _))
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!univalence)
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!is_equiv_iso_of_equiv,
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(iso_of_eq_eq_compose A B)⁻¹ ▸ H
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end set
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definition category_hset [instance] : category hset :=
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category.mk precategory_hset set.is_univalent_hset
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definition Category_hset [reducible] : Category :=
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Category.mk hset category_hset
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abbreviation set := Category_hset
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end category
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