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Facts about Adjoints#439

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ncfavier merged 28 commits intomainfrom
adjoint-facts
Dec 19, 2024
Merged

Facts about Adjoints#439
ncfavier merged 28 commits intomainfrom
adjoint-facts

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@TOTBWF
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@TOTBWF TOTBWF commented Nov 5, 2024

Description

The following PR proves a bunch of random facts about adjoints. The most notable results are:

  • A characterization of when a left/right adjoint is full or faithful
  • A characterization of when a right adjoint is conservative
  • All of Borceux 3.6

This requires a bit of machinery to set up: in particular, we need a bit of theory about strong monos. In light of this,
I've factored out a lot of the proofs about strong epis into general results about orthogonal maps. I've also done a
naming/API standardization pass on StrongEpi, and renamed it to Strong.Epi to make Strong.Mono a bit more
well organized.

There are also a bunch of misc. reasoning combinator additions, including Cat.Natural.Reasoning.

Checklist

Before submitting a merge request, please check the items below:

  • I've read the contributing guidelines.
  • The imports of new modules have been sorted with support/sort-imports.hs (or nix run --experimental-features nix-command -f . sort-imports).
  • All new code blocks have "agda" as their language.

If your change affects many files without adding substantial content, and
you don't want your name to appear on those pages (for example, treewide
refactorings or reformattings), start the commit message and PR title with chore:.

@TOTBWF TOTBWF requested review from ncfavier and plt-amy November 5, 2024 18:38
@Lavenza
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Lavenza commented Nov 5, 2024

@TOTBWF TOTBWF requested a review from plt-amy November 12, 2024 15:46
@TOTBWF
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TOTBWF commented Nov 25, 2024

The best order to review this in is probably:

  • *.Morphism and *.Reasoning
  • Cat.Morphism.StrongEpi rename
  • Cat.Adjoint.Properties
  • Cat.Adjojnt.Epireflective
  • Cat.Adjoint.Conservative

@TOTBWF TOTBWF requested a review from plt-amy December 3, 2024 21:42
@ncfavier ncfavier enabled auto-merge (squash) December 19, 2024 17:29
@ncfavier ncfavier merged commit 7b6bb74 into main Dec 19, 2024
@ncfavier ncfavier deleted the adjoint-facts branch December 19, 2024 17:29
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4 participants