> an untyped closure-based programming language with a similar array and sort api to JS

Ah! You're talking about Racket or Scheme!

```

> (sort '(3 1 2) (lambda (a b) (< a b)))

'(1,2,3)

```

I suppose you ought to go and tell the r6rs standardisation team that a HN user vehemently disagrees with their api: https://www.r6rs.org/document/lib-html-5.96/r6rs-lib-Z-H-5.h...

To address your actual pedantry, clearly you have some implicit normative belief about how a book about category theory should be written. That's cool, but this book has clearly chosen another approach, and appears to be clear and well explained enough to give a light introduction to category theory.

The syntax in the article is not scheme, you can clearly see it in my comment you're responding to.

As for your 'light introduction' comment: even ignoring the code, these are not pedantic complaints but basic mathematical and factual errors.

For example, the statement of Birkhoff’s Representation Theorem is wrong. The article says:

> Each distributive lattice is isomorphic to an inclusion order of its join-irreducible elements.

That is simply not the theorem. The theorem says "Theorem. Any finite distributive lattice L is isomorphic to the lattice of lower sets of the partial order of the join-irreducible elements of L.". You can read the definition on Wikipedia [0]

The article is plain wrong. The join-irreducibles themselves form a poset. The theorem is about the lattice of down-sets of that poset, ordered by inclusion. So the article is NOT simplifying, but misstating one of the central results it tries to explain. Call it a 'light introduction' as long as you want. This does not excuse the article from reversing the meaning of the theorem.

It's basically like saying 'E=m*c' is a simplification of 'E=m*c^2'.

[0] https://en.wikipedia.org/wiki/Birkhoff%27s_representation_th...