Functional programming and category theory tweets from @JohnDCook
Houston, TX
Joined June 2016
- Tweets4.2K
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Functor Fact retweeted
📄 Spivak (2026) Compositional Dynamics in Learning and Mechanics arxiv.org/abs/2606.28984
Functor Fact retweeted
Lasagna is a monoid. Stack two lasagnas, you get one tall lasagna. This is in contrast to e.g. a pizza. Stacking two pizzas does not make a new pizza, the top pizza merely becomes a topping of the bottom pizza
Follow me for more categorical insights
Functor Fact retweeted
If you've been struggling learning category theory, you might want to check out Paolo Perrone's 'Notes on Category theory: with examples from basic mathematics' available publicly on arXiv.
These notes were produced during a class given to a diverse set of scientists (including chemists and physicists), with knowledge in linear algebra being the only subject assumed to be known!
🔗👇
Functor Fact retweeted
Python made AI accessible.
Rust can make parts of AI understandable.
That’s the bet behind Category Theory for Tiny ML in Rust.
We’re building tiny ML systems from first principles using:
Rust types
typed transformations
composition
training loops
category theory as an engineering tool
Not abstraction cosplay.
Executable structure.
Working draft. Public feedback welcome.
Functor Fact retweeted
Alexander Grothendieck
My name is Alexander Grothendieck
And Alfred Tarski’s "≅" is far too weak
But just you wait
Just you wait
Functor Fact retweeted
"Why I never learned category theory"
Chapter 1, Exercise 1: Show the following diagram commutes
Functor Fact retweeted
"This follows from general theory, the details are in Lurie"
"No they aren't, did you even read it?"
"No, did you?"
"No"
Functor Fact retweeted
(Weak) Homotopy Equivalences
bartoszmilewski.com/2025/06/…
Functor Fact retweeted
"There are two kinds of generalizations. One is cheap and the other is valuable. It is easy to generalize by diluting a little idea with a big terminology. It is much more difficult to prepare a refined and condensed extract from several good ingredients." -- George Pólya
Functor Fact retweeted
For a monoid M, TFAE:
(1) The associativity diagram
M × M × M → M × M
↓ ↓
M × M → M
is a pull-back (of sets).
(2) M is a group.
Functor Fact retweeted
Stonean spaces, projective objects, the Riesz representation theorem, and (possibly) condensed mathematics
terrytao.wordpress.com/2025/…
