Rust is for Professionals • Hacker News Board

Re: Rust is for Professionals

#81

Post by estebank » Tue, Apr 13, 2021, 4:33 PM UTC

sanxiyn wrote: post #72

ajross wrote: post #62

Earlier quoted context omitted.

You're describing the desired behavior of the compiler, but not what it actually implements. In fact there are an infinite number of correct Rust programs which will never access memory incorrectly but which will still be rejected by the compiler, for the simple reason that Rust's authors, talented though they may be, have made no progress at all at solving the Halting Problem. What Rust actually accepts is a subset…

No, the rule I stated is what is actually implemented. Like all type checking technology, the rule is about static behavior, not dynamic behavior. So halting problem is irrelevant. Rust accepts all programs that follow the rule in static behavior. It's not a subset, and it's not a best effort to prove. It's the complete statement. "Access" means source code construct to read or write. Rust doesn't care whether the co…

I believe the "subset of correct code" refers to things like the current non-support for things like

    let (left, right) = (&mut foo[..split], &mut foo[split..]);

where you have to rely on things like foo.split_at_mut(split), which are implemented as unsafe under the cover.

I see these are limitations but not show-stoppers in any way.

Re: Rust is for Professionals

#82

Post by ajross » Tue, Apr 13, 2021, 4:33 PM UTC

sanxiyn wrote: post #72

ajross wrote: post #62

Earlier quoted context omitted.

You're describing the desired behavior of the compiler, but not what it actually implements. In fact there are an infinite number of correct Rust programs which will never access memory incorrectly but which will still be rejected by the compiler, for the simple reason that Rust's authors, talented though they may be, have made no progress at all at solving the Halting Problem. What Rust actually accepts is a subset…

No, the rule I stated is what is actually implemented. Like all type checking technology, the rule is about static behavior, not dynamic behavior. So halting problem is irrelevant. Rust accepts all programs that follow the rule in static behavior. It's not a subset, and it's not a best effort to prove. It's the complete statement. "Access" means source code construct to read or write. Rust doesn't care whether the co…

Link to the relevant spec then? Admittedly my intuition is a year stale at the moment, but I went looking hard for this at one point and found nothing other than source code.

Re: Rust is for Professionals

#83

Post by iudqnolq » Tue, Apr 13, 2021, 4:34 PM UTC

ahelwer wrote: post #12

Here I am on day three of an attempt to modify a rust program with logic that would have taken about twenty minutes to implement in C# or Java. It has to do with operations on strings (use a regex to find a string in some text, escape all the regex-reserved characters in that string, then use the string as a regex to find other occurrences of itself in the text) so I get that I'm really thrown into the borrow-checker…

I'm in a similar position. I highly recommend posting snippets of what you're trying to do in the Rust discord. The people are super nice and very helpful.

Honestly the friendliness of the community is a big part of why I'm learning Rust. I found it so much harder to get free help from volunteers with c code issues. Not that I deserve it or anything, but it's really nice and I try to contribute back by writing PRs to improve the docs once I understand something.

Re: Rust is for Professionals

#84

Post by burntsushi » Tue, Apr 13, 2021, 4:35 PM UTC

ahelwer wrote: post #43

devit wrote: post #37

Earlier quoted context omitted.

That seems rather trivial, and I'm not sure how you could possibly have any issues with the borrow checker. Just do the first regex search, then escape into a String with regex::escape, then build a regex from the String and search with it. Of course what you are doing is probably wrong since you should use a string matching crate rather than escaping characters and using a regex matching crate.

Since it's so trivial, I would be quite happy for you to implement the feature for me! https://github.com/tree-sitter/tree-sitter/issues/982 Just lol at the idea that you won't run into borrow checker issues when dealing with strings though.

Solving that issue isn't trivial. I just read it and I wouldn't know where to begin, probably because I don't understand the requirements.

I think what's being called "trivial" is doing a bit of regex searching. It's probably accurate to call that trivial for an experienced Rust programmer, but if you're just beginning, I don't think it's helpful to call anything trivial. I still remember my first exposure to Rust. It was different. It took a bit to grok. But once it clicked, things were much better.

As the maintainer of the regex crate, I invite you or anyone to ask for help using regexes. The regex repo has Discussions opened up, so it's appropriate to ask for help, even if they are beginner questions: https://github.com/rust-lang/regex/discussions

As usual though, try to provide as many details as you can. Giving the source code you have but can't get to work is a great start, for example.

Re: Rust is for Professionals

#85

Post by ahelwer » Tue, Apr 13, 2021, 4:35 PM UTC

estebank wrote: post #65

ahelwer wrote: post #39

Earlier quoted context omitted.

I mean yeah, that's why I went and read a bunch of the book. But I still run into lots of issues. Like what the hell is a borrow cow and when would I want to use it? And how do I fix the "temporary value dropped when borrowed" error in a series of maps on options?

If you don't mind sharing snippets for the diagnostics you couldn't figure out, I would love to see them in case we can mechanically suggest the appropriate code, but in general a well placed .clone(), .cloned() or .collect() will be what you want. Likely what's happening is you're iterating over a sequence (you can think of options as a sequence of only one iteration as well), but that iterator is over borrows of th…

Sure! So I'm trying to implement this feature: https://github.com/tree-sitter/tree-sitter/issues/982#issuec...

And here's my branch (you can see the latest commits to see the file I'm modifying): https://github.com/ahelwer/tree-sitter/tree/testfile-separat...

I haven't had a chance to go through and add clones everywhere, and will be away at a PT appointment for the next hour or so, but would appreciate any pointers you can give.

Re: Rust is for Professionals

#86

Post by iudqnolq » Tue, Apr 13, 2021, 4:35 PM UTC

ajross wrote: post #82

sanxiyn wrote: post #72

Earlier quoted context omitted.

No, the rule I stated is what is actually implemented. Like all type checking technology, the rule is about static behavior, not dynamic behavior. So halting problem is irrelevant. Rust accepts all programs that follow the rule in static behavior. It's not a subset, and it's not a best effort to prove. It's the complete statement. "Access" means source code construct to read or write. Rust doesn't care whether the co…

Link to the relevant spec then? Admittedly my intuition is a year stale at the moment, but I went looking hard for this at one point and found nothing other than source code.

There's no spec yet, but there are working groups working on it.

Re: Rust is for Professionals

#87

Post by StavrosK » Tue, Apr 13, 2021, 4:37 PM UTC

fzzzy wrote: post #55

kzhukov wrote: post #41

Earlier quoted context omitted.

> safety-critical applications Nope, Rust is also not suitable for these tasks since it doesn't have a certified toolchain (e.g. ISO26262 for automotive or DO-178 for aerospace). > embedded Current LLVM-based compiler lacks support for some platforms (e.g. Xtensa for some ESP32 MCUs).

It took me two hours to compile the esp32 fork of rustc on a 2015 macbook pro. Not ideal, but it works just fine.

That's very interesting! Do you have any pointers on how to do that?

Re: Rust is for Professionals

#88

Post by organian » Tue, Apr 13, 2021, 4:37 PM UTC

ahelwer wrote: post #43

devit wrote: post #37

Earlier quoted context omitted.

That seems rather trivial, and I'm not sure how you could possibly have any issues with the borrow checker. Just do the first regex search, then escape into a String with regex::escape, then build a regex from the String and search with it. Of course what you are doing is probably wrong since you should use a string matching crate rather than escaping characters and using a regex matching crate.

Since it's so trivial, I would be quite happy for you to implement the feature for me! https://github.com/tree-sitter/tree-sitter/issues/982 Just lol at the idea that you won't run into borrow checker issues when dealing with strings though.

I'm not the person you replied to, but here's some Playground code I just wrote that might be helpful for you, based on the issue you linked:

https://play.rust-lang.org/?version=stable&mode=debug&editio...

Re: Rust is for Professionals

#89

Post by sylvain_kerkour » Tue, Apr 13, 2021, 4:38 PM UTC

novok wrote: post #71

sylvain_kerkour wrote: post #63

Earlier quoted context omitted.

As an indie developer, switching from Go to Rust for web APIs was extremely satisfying. At first there was a productivity loss, but after a few months the productivity was better than Go thanks to Rust's functional features which make it extremely pleasant to write business logic, and the type system catching bugs during development instead of production. You can read more about the experience here: https://kerkour.c…

How much of a productivity boost would you’ve gotten from java or kotlin which provides a lot of those features with all the complexity and build times?

I did a bit of Java and Kotlin for Android development, but never for web APIs so I can't really tell, but one thing I'm sure is that Rust's build system and dependency manager (Cargo) is far more pleasant to use than the experience I had with Java.

Other great things are the ease of packaging with Docker, the low resources usage which helps to keep Heroku's bills small, and the excellent IDE support.

Re: Rust is for Professionals

#90

Post by devit » Tue, Apr 13, 2021, 4:38 PM UTC

ahelwer wrote: post #39

sanxiyn wrote: post #26

Earlier quoted context omitted.

You can't learn Rust by StackOverflow, that just doesn't work. It is well known, I repeat this everytime I see it happening, and they never listen. It's deeply frustrating.

I mean yeah, that's why I went and read a bunch of the book. But I still run into lots of issues. Like what the hell is a borrow cow and when would I want to use it? And how do I fix the "temporary value dropped when borrowed" error in a series of maps on options?

1. You mean Cow? It's an enum of either String or &'a str, typically used with 'static so you can either store an heap-allocated string or a static string without copying it to the heap

2. Given you mention "maps of option", probably you are doing something like opt.map(|x| &x.field) or equivalent which is obviously invalid (since you are returning a reference to a subobject of a function argument). Instead, you need to do opt.as_ref().map(|x| &x.field) (or as_mut() if it's mutable).