ext-ds VS bst

I started this project many years ago when I was coming up with ideas for immutable data structures for the PHP data structures extension: https://github.com/php-ds/ext-ds. I wanted to support access by position in a sorted set, which led to the idea of using binary search trees for both lists and sets. However, I did not expect the scope of this project to increase as much as it did.

The more I read about binary search trees, the more I thought about them, and so down the rabbit hole I went.

You're being downvoted by people who evidently aren't aware there are alternatives.

The Github repo hasn't had a new release since 2019, with just one guy being the primary maintainer

This is actually a 3rd party extension, that's why it isn't in core.

If you like this article then you might also be interested in: https://github.com/c-blake/bst interesting

It's ANSI C with a bespoke macro generics system not Go, does not cover as many balancing rules, and is not written up as nicely. It does do something only weakly represented in your Go impls, AFAICT - "binary symmetry" - the reflection about left-right intrinsic to most ideas in this area. (Mehlhorn has a book that does this, but that is the only other source I know.) It also has API considerations like seek-edit separation and how to handle in-tree duplicate key FIFO/LIFO/etc (as opposed to values which are also collections).

Also, Re: B-trees among several comments - edit heavy B-trees with large nodes (driven by IO bandwidth-delay products) need some "mini-scalable" structure for their nodes since shifting (on average) half the entries can cost. That mini-scale could be another B-tree or it could be a binary search tree, perhaps adjusted to have 2-byte sized pointers into the little arena that is a node if 64Knode is enough. I once heard Sybase (now Microsoft SQL Server?) used skip lists. Anyway, this may be a remaining use case for binary trees even in the presence of a B-tree.

While I agree the common pattern is to use void*/dynamic dispatch, this is not necessary. E.g., https://github.com/glouw/ctl/ or https://github.com/c-blake/bst show a couple ways to have generic code statically specialized in regular old C.