[kaba0]

Maybe don’t comment on things you don’t know much about?

Lazy data structures can be very efficient (slower than mutable one in single-threaded execution, but much faster for concurrent usage) and they definitely don’t copy everything every time.

[tkrskxyz]

Let's remember that we are having this conversation in the context of this article.

I know something about lazy data structures from my IOI days and I'm pretty sure I know about game development (altough admittedly forgot about this stuff while reading this post as it is not mentioned in the article itself, others comments provided nice resources).

While they are extremely efficient you still have an overhead. It is obviously minimal but it can matter with -+10000 updates (game logic, actors only, with some overhead by itself) per frame - not per second. O(log n) is not dissmisible (in some hardcore cases I would say that even O(log log n) can have slight impact and If you can have steady 60fps rather than 59fps you want that).

Game development also doesn't really align with functional programming (as described in the article). I mean the main thing to care about is speed since it allows us to do more fancy stuff. Then again, I'm not an engine developer so who knows, maybe it's actually better and some big engines do use it at core (If anyone knows I'm interested). But in most cases it's a lot harder to do (since games do SO much different stuff that It's really hard to seperate parallelizable from sequential tasks anyway and it simply doesn't make sense in most productions).