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@marcinjangrzybowski marcinjangrzybowski commented Sep 2, 2024

Cubical/Relation/Binary/Setoid.agda

  • Setoid as Pair of hSet and propositional equivalence relation

Cubical/Categories/Instances/Setoids.agda

  • Univalent Category of Setoids
  • Adjoint quadruple of functors from/to SET : Quot ⊣ IdRel ⊣ Forget ⊣ FullRel (crude, basic cohesion?)
  • ¬BaseChange⊣SetoidΠ - Base change functor does not have right adjoint (so SETOID cannot be LCCC, at least not in the literal sense) implementation of Setoids are not an LCCC by Thorsten Altenkirch and Nicolai Kraus (https://nicolaikraus.github.io/docs/setoids.pdf)

* Cubical/Categories/Category/Path.agda
  Helper representation of Path between categories to deal with ineficiency in WeakEquivalence.agda
* Cubical/Relation/Binary/Setoid.agda
  Setoid - Pair of hSet and propositional equivalence relation
* Cubical/Categories/Instances/Setoids.agda
  Univalent Category of Setoids

changes:
* Cubical/Categories/Adjoint.agda
  added composiiton of adjunctions
* Cubical/Categories/Equivalence/WeakEquivalence.agda
  Equivalence equivalent to Path for Univalent Categories
* Cubical/Categories/Instances/Functors.agda
  currying of functors is an isomorphism.
* Cubical/Foundations/Transport.agda
  transport-filler-ua = ua-gluePath

+ some other minor helpers
@marcinjangrzybowski
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Depends on #1120

@marcinjangrzybowski marcinjangrzybowski marked this pull request as draft September 2, 2024 23:35
removed unifnished code
@maxsnew maxsnew self-assigned this Sep 10, 2024
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maxsnew commented Sep 10, 2024

A couple of things before a more detailed review:

  1. I don't think we should commit to the terminology "Setoid" for this, as often a Setoid is defined as coming with a Type-valued relation rather than a Prop-valued relation. I would suggest we just call these "equivalence relations" or even "thin groupoid"
  2. The link https://people.cs.nott.ac.uk/psznk/docs/setoids.pdf doesn't work for me, I get a 404

@marcinjangrzybowski
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  1. Updated the link to working one: https://nicolaikraus.github.io/docs/setoids.pdf
    2.I will change terminology.

fixed dead link
ΣℙCat = ΣPropCat

isSmall : (C : Category ℓ ℓ') Type ℓ
isSmall C = isSet (C .ob)
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I don't think isSmall is a good name; These categories are conventionally called 'strict' categories, and calling them 'small' gives the impression that this is about universe level, which it's not.

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how about isStrict ? I do not have anything more descriptive in mind

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yes, that's also what the 1lab calls it.

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3 participants