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Comment by n_u | Hacker News Reader

This is my second attempt learning Rust and I have found that LLMs are a game-changer. They are really good at proposing ways to deal with borrow-checker problems that are very difficult to diagnose as a Rust beginner.

In particular, an error on one line may force you to change a large part of your code. As a beginner this can be intimidating ("do I really need to change everything that uses this struct to use a borrow instead of ownership? will that cause errors elsewhere?") and I found that induced analysis paralysis in me. Talking to an LLM about my options gave me the confidence to do a big change.

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n_u's point about LLMs as mentors for Rust's borrow checker matches my experience. The error messages are famously helpful, but sometimes you need someone to explain the why.

I've noticed the same pattern learning other things. Having an on-demand tutor that can see your exact code changes the learning curve. You still have to do the work, but you get unstuck faster.

Storngly agreed. Or ask it to explain the implications of using different ownership models. I love to ask it for options, to what if scenarios out. It's been incredibly helpful for learning rust.

>In particular, an error on one line may force you to change a large part of your code.

There's a simple trick to avoid that, use `.clone()` more and use fewer references.

In C++ you would be probably copying around even more data unnecessarily before optimization. In Rust everything is move by default. A few clones here and there can obviate the need to think about lifetimes everywhere and put you roughly on par with normal C++.

You can still optimize later when you solved the problem.

Clone doesn't work when you need to propagate data mutations, which is what you need most of the time.

Another option is to just use cells and treat the execution model similarly to JavaScript where mutation is limited specific scopes.

I am old but C is similarly improved by LLM. Build system, boilerplate, syscalls, potential memory leaks. It will be OK when the Linux graybeards die because new people can come up to speed much more quickly

The thing is LLM-assisted C is still memory unsafe and almost certainly has undefined behaviour; the LLM might catch some low hanging fruit memory problems but you can never be confident that it's caught them all. So it doesn't really leave you any better off in the ways that matter.

I don’t code C much, is my passion side language. LLM improves my ability to be productive and quickly. Is not a silver bullet, but is an assist

Almost as well as a human doing it!

Better than a human maybe. But still not good enough to rely on.

I don't see why it shouldn't be even more automated than that, with LLM ideas tested automatically by differential testing of components against the previous implementation.

EDIT: typo fixed, thx

Defining tests that test for the right things requires an understanding of the problem space, just as writing the code yourself in the first place does. It's a catch-22. Using LLMs in that context would be pointless (unless you're writing short-lived one-off garbage on purpose).

I.e. the parent is speaking in the context of learning, not in the context of producing something that appears to work.

I'm not sure that's true. Bombarding code with huge numbers of randomly generated tests can be highly effective, especially if the tests are curated by examining coverage (and perhaps mutation kills) in the original code.

Right, that method is pretty good at finding unintentional behavior changes in a refactor. It is not very well suited for showing that the program is correct which is probably what your parent meant.

That doesn't seem like the same problem at all. The problem here was reimplementing the program in another language, not doing that while at the same time identifying bugs in it.

Conversion of one program to another while preserving behavior is a problem much dumber programs (like compilers) solve all the time.

I'm assuming you meant to type

> I don't see why it *shouldn't be even more automated

In my particular case, I'm learning so having an LLM write the whole thing for me defeats the point. The LLM is a very patient (and sometimes unreliable) mentor.

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