| π |
[READ FIRST] Rules & Resources for the Category Theory subforum β textbooks, nLab links, Haskell bridges
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12 |
4,821 |
by CubicalCat
Feb 14, 2026 11:47 PM
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| π |
[STICKY] CGPA Glossary: Category Theory Edition β Objects, Morphisms, Functors, nya~ explained for new cat girls
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29 |
7,093 |
by KleisliKitten
Mar 15, 2026 02:33 AM
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| π₯ |
"A monad is just a monoid in the category of endofunctors" β what does this ACTUALLY mean? is the t-shirt correct??
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147 |
9,334 |
by FunctorFelyne
Mar 27, 2026 03:59 AM
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| π¬ |
The Yoneda Lemma: can someone give an intuitive explanation without lying too much? πΏ
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38 |
1,204 |
by ToposTail
Mar 27, 2026 01:14 AM
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| π¬ |
Adjunctions are EVERYWHERE and it's making me cry (a list: free/forgetful, curry/uncurry, Ξ£/Ξ types, ...)
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54 |
2,871 |
by MewMorphism
Mar 26, 2026 10:52 PM
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| π¬ |
Natural transformations as "morphisms of functors" β vertical vs horizontal composition, whiskering, the interchange law
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22 |
983 |
by CubicalCat
Mar 25, 2026 07:41 PM
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| π |
Is Hask actually a category? The fast-and-loose reasoning thread (bottoms, seq, unsafePerformIO...)
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91 |
4,450 |
by PurrfectPullback
Mar 24, 2026 09:05 PM
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| π¬ |
Toposes and the subobject classifier Ξ© β why does this generalize Set so elegantly? (w/ a cat girl diagram attempt)
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33 |
1,566 |
by SheafSiamese
Mar 23, 2026 04:18 AM
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| π¬ |
Kleisli categories and computational effects β Moggi's insight explained from scratch, no prior CT needed
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15 |
612 |
by MewMorphism
Mar 26, 2026 11:00 PM
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| π₯ |
β-Categories: quasicategories vs Segal spaces vs complete Segal spaces β why are there so many models and which one should I use??
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112 |
5,880 |
by ToposTail
Mar 27, 2026 02:37 AM
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| π¬ |
Limits, colimits, and universal properties β product types are products! sum types are coproducts! pullbacks??
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44 |
2,103 |
by KleisliKitten
Mar 21, 2026 06:55 PM
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| π¬ |
The CurryβHowardβLambek correspondence: propositions=types=objects, proofs=programs=morphisms. Mind officially blown.
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67 |
3,299 |
by MewMorphism
Mar 22, 2026 08:12 PM
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| π¬ |
Kan Extensions: "all concepts are Kan extensions" β coend calculus, comma categories, and why this matters for type theory
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19 |
877 |
by ToposTail
Mar 20, 2026 12:40 AM
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[SOLVED] Monoidal categories and tensor products β I finally understand braided monoidal cats and I made ASCII art to celebrate
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26 |
1,450 |
by CubicalCat
Mar 18, 2026 05:03 PM
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| π¬ |
EilenbergβMoore algebras vs Kleisli category: two ways to decompose a monad, which one is more fun? (poll inside)
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35 |
1,712 |
by PurrfectPullback
Mar 16, 2026 10:22 PM
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| π¬ |
Enriched category theory for dummies (me) β hom-sets β hom-objects, V-categories, Ab-enriched = preadditive categories
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17 |
690 |
by SheafSiamese
Mar 14, 2026 03:15 AM
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| π₯ |
Grothendieck toposes, sheaves, and why a topos is like a "generalized space" β guest post by SheafSiamese π
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88 |
4,007 |
by ToposTail
Mar 25, 2026 11:58 PM
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| π¬ |
Freeβforgetful adjunctions: free monoids, free groups, free vector spaces β the universal property machine go brr
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41 |
1,934 |
by FunctorFelyne
Mar 19, 2026 08:33 PM
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| π¬ |
Cubical Type Theory and its categorical semantics β cubical sets, connections, compositions in CubicalCat's favourite topic
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8 |
344 |
by CubicalCat
Mar 27, 2026 12:55 AM
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| π¬ |
Duality principle: opposite categories, contravariant functors, and why every theorem gives you a free theorem
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21 |
908 |
by MewMorphism
Mar 11, 2026 04:44 AM
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