Rust 1.45 • Hacker News Board

Re: Rust 1.45

#41

Post by steveklabnik » Thu, Jul 16, 2020, 3:36 PM UTC

harikb wrote: post #34

p4bl0 wrote: post #14

By any chance if anyone is in the Paris area and is interested to teach Rust at university next year during the first semester. Please get in touch :).

Is this undergrad? Genuinely curious, how will you get someone to understand what ownership helps avoid without them having experienced the pain on the other side? I guess with younger and younger kids learning programming these, may be there can handle more? I am not sure if my son would understand all of the intricacies in his first semester.

> Genuinely curious, how will you get someone to understand what ownership helps avoid without them having experienced the pain on the other side?

This is an eternal debate about Rust. I don't think it's required though. Can you appreciate functions without understanding assembly and calling conventions? I believe the answer is yes :)

Re: Rust 1.45

#42

Post by fullstop » Thu, Jul 16, 2020, 3:37 PM UTC

pitaj wrote: post #37

fullstop wrote: post #36

I keep seeing more and more news about Rust, and figure that perhaps it is time that I learn something new. 99% of my development work these days is C with the target being Linux/ARM with a small-ish memory model. Think 64 or 128MB of DDR. Does this fit within Rust's world? I've noticed that stripped binary sizes for a simple "Hello, World!" example are significantly larger with Rust. Is this just the way things are…

A significant portion of the size is formatting and panic unwinding code. Some of this can be reduced by using `panic=abort` but it is a known issue. Worth noting that a lot of the code size is a constant addition that won't really scale with your program code.

Thanks, I'll take a look at this!

Re: Rust 1.45

#43

Post by yodelshady » Thu, Jul 16, 2020, 3:37 PM UTC

angrygoat wrote: post #8

This rather niche fixing of unsafe behaviour is excellent: https://blog.rust-lang.org/2020/07/16/Rust-1.45.0.html#fixin... I spent a few years as a scientific programmer and this is exactly the sort of thing that just bites you on the behind in C/C++/Fortran: the undefined behaviour can actually manifest as noise in your output, or just really hard to track down, intermittent problems. A big win to get rid of it.

Out of interest, with (my instance of!) 1.44, "let i = 257.0; i as u8" casts to 1. "let i = usize::MAX as f64 + 1.0; i as usize" does likewise. If you assign i as an integer DIRECTLY, however, it saturates.

To be honest... struggling to see why you'd do the former, outside of situations where you're happy with saturation, though I haven't thought about it a lot. Agreed that a consistent behaviour is a big help - I can work with "Rust does x in this scenario".

Re: Rust 1.45

#44

Post by p4bl0 » Thu, Jul 16, 2020, 3:38 PM UTC

harikb wrote: post #34

p4bl0 wrote: post #14

By any chance if anyone is in the Paris area and is interested to teach Rust at university next year during the first semester. Please get in touch :).

Is this undergrad? Genuinely curious, how will you get someone to understand what ownership helps avoid without them having experienced the pain on the other side? I guess with younger and younger kids learning programming these, may be there can handle more? I am not sure if my son would understand all of the intricacies in his first semester.

Yes it is a course aimed at undergrad students, in their second year at university.

Of course they won't be able to grasp everything that Rust has to offer, but that is true of any language. I think Rust will expose them to many theoretical and practical CS concepts that they will be glad to have at least heard of during their studies.

In our degree, the first year students learn to program with Python, Racket (or OCaml depending on which teacher they get), C, Prolog, Bash, … Each of these language have way more to offer than what they can grasp. But each of them offers a different approach to programming and help the students to actually learn to program (rather than learning to write Java code, for example).

The course in question is actually called "Advanced programming". I want to experiment with a Rust course in second year as a kind of followup to both the functional programming course (the Racket/OCaml one) and the imperative programming course (the C one) that they have during the first year. If it really doesn't work, we'll change for something else or simply swap back to it being "Advanced C programming" for instance. But first, let's try to make the Rust experiment work. I really think it can benefits our students!

Re: Rust 1.45

#45

Post by mas3god » Thu, Jul 16, 2020, 3:41 PM UTC

person_of_color wrote: post #13

Any algo-trading backtest frameworks in Rust?

All you need for algotrading is to query an api. Rust would be a poor choice for that anyways, like using a semi truck to carry your bike around.

Re: Rust 1.45

#46

Post by pas » Thu, Jul 16, 2020, 3:42 PM UTC

snalty wrote: post #39

I'm building an embedded project that currently runs a python script for automatic brightness. It takes a brightness value from a sensor over I2C, applies a function to get an appropriate LCD brightness value and then sends that to the display driver over a serial port. Would this be an appropriate project to write in Rust to learn the basics of this language?

Yes. We used Rust to drive a few things via GPIO and USB-RS232 a few years ago on a Raspberry Pi, it was a pretty pleasant experience.

Maybe take a look at this I2C lib: https://github.com/rust-embedded/rust-i2cdev

Re: Rust 1.45

#47

Post by chowells » Thu, Jul 16, 2020, 3:46 PM UTC

pwdisswordfish2 wrote: post #23

davrosthedalek wrote: post #12

Earlier quoted context omitted.

I'm not sure I understand this. Does it not produce a run time error? Why not? This looks very dangerous, because it essentially does the "nearest to right" thing. Say, you cast 256 to a u8, it's then saturated to 255. That's almost right, and a result might be wrong only by 0.5%. Much harder to detect than if it is set to 0.

> I'm not sure I understand this. Does it not produce a run time error? Why not? It’s not supposed to. Type casting with ‘as’ is supposed to be lightweight and always succeed; there is no room in the type system to return an error. In case lossless casting is not possible, some value still has to be returned. Until now, this was outright UB — meaning the compiler is not even obligated to keep it consistent from one b…

> meaning the compiler is not even obligated to keep it consistent from one build to another.

Way worse than that. The compiler wasn't obligated to act like anything at all. It would be totally legal to compile it so that the first time the value was accessed you got 0, the next time you got 1 - within the same program execution, with no mutation of the value. That is the sort of thing that is observed behavior of UB in the worst cases, and why it's so terrible to just pretend that UB is innocuous.

Re: Rust 1.45

#48

Post by bestouff » Thu, Jul 16, 2020, 3:46 PM UTC

fullstop wrote: post #36

I keep seeing more and more news about Rust, and figure that perhaps it is time that I learn something new. 99% of my development work these days is C with the target being Linux/ARM with a small-ish memory model. Think 64 or 128MB of DDR. Does this fit within Rust's world? I've noticed that stripped binary sizes for a simple "Hello, World!" example are significantly larger with Rust. Is this just the way things are…

Yes there's a fixed cost because of the std library, panics unwinding code (i.e. clean recovery instead of aborting when something goes wrong), and the tendency to statically compile everything in adds some more, but in embedded context (a.k.a. "no_std") you can observe C and Rust code are very comparable.

Especially in your case you'll find Rust to be a joy to use: you'll have way more confidence in your code being able to run for months without segfaults or memory leaks. And if you have a good understanding of the C memory model using Rust will be a breeze.

Re: Rust 1.45

#49

Post by mjw1007 » Thu, Jul 16, 2020, 3:47 PM UTC

snalty wrote: post #39

I'm building an embedded project that currently runs a python script for automatic brightness. It takes a brightness value from a sensor over I2C, applies a function to get an appropriate LCD brightness value and then sends that to the display driver over a serial port. Would this be an appropriate project to write in Rust to learn the basics of this language?

Yes. Some of my first Rust projects were that sort of embedded thing.

Re: Rust 1.45

#50

Post by bestouff » Thu, Jul 16, 2020, 3:51 PM UTC

p4bl0 wrote: post #14

By any chance if anyone is in the Paris area and is interested to teach Rust at university next year during the first semester. Please get in touch :).

Do you pay the daily transit from Grenoble area ?