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Comment by klysm | Hacker News Reader

I think a lot of concepts from category theory can be applied to every day programming in a lot of languages. Understanding how things compose helps you write better APIs.

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I don't mean any offense to you personally, but this kind of comment is why I hate internet discussions. You just said the opposite of what I said without adding anything new.

But it’s indeed true that

> Understanding how things compose helps you write better APIs.

Which has nothing substantial to do with category theory.

Nah, here's a recentish overview:

https://golem.ph.utexas.edu/category/2020/01/profunctor_opti...

Composition is an old idea that predates Category Theory by a long shot.

Correct.

But the real understanding of composability in all its complexity and generality has only come with (the more recent developments in) category theory.

Nope. It is just a different model for the same thing. You might find it enlightens your understanding of composition but it doesn't make it more "real" than any other model.

What other model shares the same expressiveness and universality of category theory?

Type theory and Set theory. For example.

Type theory, maybe; set theory, no.

Historically, this mindset hasn't been productive, eg. complex analysts skeptical of GAGA faltered in the 90's and 00's. HoTT is still in its infancy.

I can explain the ideas behind composition in 5 minutes using good old (Haskell) types. No Category Theory needed or wanted.

Aren’t a lot of Haskell types identical to category theory concepts? Monad?

The awesome thing about category theory is that so many things are _examples of_ category theoretic concepts. I’m sure the types you would use would be too. Then you can jump over to a different language and see the same structure.

It gives you a universal vocabulary for how things compose and interact. That’s the powerful part.

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