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by ragnese 2127 days ago
> Related: I heard someone else say that while Clojure and Erlang embrace immutability for concurrency, Rust shows that you can "just mutate". It's still safe for concurrency (due to its type system).

Yes! I will repeat a sentiment I articulated on Reddit about that. Even after having used Rust on a handful of small-to-medium sized projects since 2016, I never realized that I could loosen/abandon my immutability fetish that I had been trained to love over the years of working with C++ and Java. C++ needs it for concurrency, and Java needs it for concurrency and because every method can mutate its inputs without telling you. Rust doesn't have either of those problems. Having immutable-by-definition objects in Rust isn't really that useful (unless, of course, the thing is naturally, semantically, immutable anyway, like a Date IMO). It was an eye-opening epiphany and I'm excited for my next Rust session to see how my "new worldview" pans out. :)
1 comments
chubot 2126 days ago
Yes I'll be interested to see how it turns out. Any blog posts / writing on the procedural viewpoint will be appreciated.

Does Rust have something like C++'s const methods? Where you can have a method that mutates a member, but doesn't logically mutate from the caller's perspective?

It seems like you could be prevented from having races on individual variables, but still have races at a higher level.

Like on database cells. I guess no language will help you with that, and that's why Hickey wrote Datomic -- to remove mutability from the database.

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ragnese 2126 days ago
> Does Rust have something like C++'s const methods? Where you can have a method that mutates a member, but doesn't logically mutate from the caller's perspective?

Yes! "Interior mutatbility" is the term to search for. In Rust, you'd wrap the field in a RefCell<T>. Many connection-pool implementations use interior mutability to manage the connections transparently to the caller.

Interior mutability is basically what, e.g. OCaml, does by default. In Rust, it's opt-in.

Yeah, DB ops are always a sticking point for figuring out how to write my APIs.

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