Agree, I can't recall using anything more complicated than lists/arrays or hash tables (key/value stores) in practice, in many years of (mostly web application) programming. And even those I'm not coding from scratch, I'm using classes or functions that my programming language gives me. For anything more complicated than that, I'm using a database, which of course is using many data structures under the covers but I don't directly touch those.
I used to use them all the time. However, now? I would be hard pressed to not use one of the many built in vector/list/dict/hash items in many languages now. I would have to be truly doing something very low level or for speed to use one.
As a counterpoint, I’ve been working on collaborative text editing. I ended up implementing a custom b-tree because we needed a few features that I couldn’t find in any off the shelf library:
- My values represent runs of characters in the document.
- Inserts in the tree may split a run.
- Runs have a size - 0 if the run is marked as deleted or the number of characters otherwise. The size changes as we process edits
- Every inserted character has an ID. I need to be able to look up any run by its ID, and then edit it. (Including querying the run’s current position in the tree and editing the run’s size).
It’s an interesting data structure problem, and it took a few weeks to have a good solution (and a few weeks more later rewriting it in safe rust & improving performance in the process).
I love this stuff. I think it’s pretty rare to find a reason to code your own collection types these days, but it certainly comes up from time to time!
> I love this stuff. I think it’s pretty rare to find a reason to code your own collection types these days, but it certainly comes up from time to time!
Absolutely! That is one of the places you want to use that style of programming. As the base classes and built in structs do not really cover it yet.
Also as a counterpoint sometimes the built in ones have some very interesting degenerate cases. I had one in an old library that basically doubled its memory footprint every time you exceeded its buffer. That was a point to change it to be a fixed allocation or something else. If i had no idea of the fundamentals I would have been totally in the weeds and no idea why it was doing it.
