E.g., see the nice work on the PAM library (https://arxiv.org/abs/1612.05665). Ideas from this work were used to build lots of cool things (immutable graph data structures, segment trees, databases) that are very fast, and all immutable.
But this is just bog standard FP community lies.
What are you even talking about, "dude"? I don't think you have the background or knowledge you seem to think you have to argue about this space. It's OK, as you blithely pointed out in your earlier post, there is a place called medium where you'll find likeminded folks that will eat up your drivel.
>what are you even talking about
I am talking about your own posts, perpetuating more moronic FP lies
>background
Nobody needs background to see that needlessly copying data for no reason is more expensive than not doing that.
Unfortunately for FP programmers, the moronic levels of doing this is actually worse than it sounds, as needlessly copying data is basically completely antithetical to how every modern CPU wants to optimally work.
It isn’t “me” declaring that runtime immutability is moronic. It is your CPU telling you that.
https://ceur-ws.org/Vol-1291/ewili14_15.pdf
Given the age of your account my guess is that you're still young with too strong opinions and too little experience. That's ok, we all start there. But I can tell you from experience, that you'll need to outgrow that mindset in order to grow intellectually.
The difference between mutability and immutability is not as clear cut as you think, and might just be the difference between a `& mut` and a `&`.