Understanding Memory Management, Part 5: Fighting with Rust

This is a good post! A few comments:

> Function Overloads

Strictly speaking, Rust doesn't support overloaded functions. Function overloading is when you define the same function but with different arguments, and the language selects the correct one based on the argument type. In this case, it's two different implementations of a trait for two different types. That said, it's close enough that this isn't really an issue, more of just a technical note, since this is a series trying to get into details.

> I can't find an explanation in the Rust documentation but I expect the reason is that someone could implement another trait that provides .into_iter() on whatever the x is in for y in x, thus resulting in a compiler error because there would be two candidate implementations.

Yep, I'm not sure that there is an official explanation anywhere else, but this is exactly what I would assume as well. This ensures that the correct implementation is called. This is also one of the reasons why adding a trait implementation isn't considered a breaking change, even if it could create a compiler error, because you can always expand it yourself to explicitly select the correct choice. Of course, these situations are usually treated more carefully then they have to be, because breakage isn't fun, even if it's technically allowed.

> But wait, you say, I'm doing exactly this in the first program, and indeed you are.

It's not the same, as the next paragraphs explain.

> We are able to examine the function and realize it's safe, but because the compiler wants to use local reasoning, it's not able to do so.

This is a super important point!

This is pretty good.

A useful way to think about this:

- All data in Rust has exactly one owner.

- If you need some kind of multiple ownership, you have to make the owner be a reference-counted cell, such as Rc or Arc.

- All data can be accessed by one reader/writer, or N readers, but not both at the same time.

- There is both compile time and run time machinery to strictly enforce this.

Once you get that, you can see what the borrow checker is trying to do for you.

I really like the text. Giving more light to the memory management of rust will help me understand more of the language. I still think some concepts of rust are over verbose but I slowly understand the hype around rust. I myself use C or C++ but I will „borrow“ some of the rust ideas to make my code even more robust

This is brilliantly written n

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A 20 page document on how to use basic variables, function calls and methods. Except for the threading paragraph, which is hard in any language, this is all complexity and refactoring pain that Rust hoists onto every programmer every day, for relatively modest benefits, somewhat improved performance and memory usage vs the garbage collected/ref-counted version of the same code.

Essentially, you wouldn't and shouldn't make that tradeoff for anything other than system programming.