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Interesting, I hadn't heard this before. Do you have any resources I could read?

Edit: I do know that languages where strings are immutable use that fact to do lots of optimization (automatically sharing "copied" strings and just cloning reference-counters, for example), but you can accomplish some of this in Rust too with Rc<> or even persistent data structures if you really want to. And of course there are cases where it's more efficient to actually mutate a string, which these languages can't do. But it sounds like you're talking about something else?



There are three strategies that other languages use automatically that you can also apply in Rust by hand: string interning, small string optimization and "Copy-on-write". For the first and second, you can use some existing crate like https://docs.rs/string-interner/0.12.2/string_interner/ and https://github.com/rust-analyzer/smol_str. For the later, you can use Cow<'_, str> https://doc.rust-lang.org/std/borrow/enum.Cow.html. I'm having trouble thinking of a case where Rc<String> would be appropriate.




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