The most exciting component of this release is the const fn improvements. With loops and if available, you can now do non-trivial computation in const fn for the first time. It reduces the gap between Rust's const fn and C++'s constexpr to a large degree. Ultimately, the miri execution engine that this feature builds upon, supports a much larger set of features that even constexpr supports. It's been a project spanni…
I wonder why && and || are not allowed in const functions?
> All boolean operators except for && and || which are banned since they are short-circuiting.
I guess I'm missing something obvious but why does the short circuiting break const-ness?
I’m learning rust right now and there is a lot to like. Steady updates like this are also very motivating. The ecosystem feels very sane - especially compared to npm. Top notch Wasm support, cross compiling is a breeze. That said, coming from a FP background (mostly Haskell/JS, now TS) Rust is... hard. I do understand the basic rules of the borrow checker, I do conceptually understand lifetimes, but actually using th…
> the borrow checker, I do conceptually understand lifetimes, but actually using them is tricky. I've been using Rust for a little over year, almost daily at work, and for several projects. I have a pretty good intuition about how the borrow checker works and what needs to be done to appease it. That said, I don't think I'm any closer to understanding lifetimes. I know conceptually how they are supposed to work (I ne…
It's worth noting that every reference in Rust has a lifetime, but the compiler is usually smart enough to infer it. What you are talking about is explicit lifetimes.
The most exciting component of this release is the const fn improvements. With loops and if available, you can now do non-trivial computation in const fn for the first time. It reduces the gap between Rust's const fn and C++'s constexpr to a large degree. Ultimately, the miri execution engine that this feature builds upon, supports a much larger set of features that even constexpr supports. It's been a project spanni…
> supports a much larger set of features that even constexpr supports This sounds promising. Can you give examples? I don't know Rust at all, and the reason I like C++ is its metaprogrammability.
I think some clarification is warranted here, because Miri is intended to be used for more than just constant evaluation. In particular, Miri wants to be able to dynamically verify `unsafe` code in order to detect undefined behavior, which means that it will eventually want to support the entire Rust language. However, just because Miri supports any given Rust feature does not necessarily mean that that feature will be made available for constant evaluation; consider features that are non-deterministic (like RNG) or architecture-dependent/nonportable (like floating-point operations), and how const-evaluating such things could potentially cause memory-unsafety to occur when runtime output and const output differ.
The most exciting component of this release is the const fn improvements. With loops and if available, you can now do non-trivial computation in const fn for the first time. It reduces the gap between Rust's const fn and C++'s constexpr to a large degree. Ultimately, the miri execution engine that this feature builds upon, supports a much larger set of features that even constexpr supports. It's been a project spanni…
I wonder why && and || are not allowed in const functions? > All boolean operators except for && and || which are banned since they are short-circuiting. I guess I'm missing something obvious but why does the short circuiting break const-ness?
That was a restriction from before 1.46 stabilized control flow in const functions. Now that we have worked out the details around `if`, we can also stabilize `&&` and `||`.
(I'm a little surprised they weren't stabilized at the same time! Edit: they were! I just didn't look closely enough.)
The most exciting component of this release is the const fn improvements. With loops and if available, you can now do non-trivial computation in const fn for the first time. It reduces the gap between Rust's const fn and C++'s constexpr to a large degree. Ultimately, the miri execution engine that this feature builds upon, supports a much larger set of features that even constexpr supports. It's been a project spanni…
I wonder why && and || are not allowed in const functions? > All boolean operators except for && and || which are banned since they are short-circuiting. I guess I'm missing something obvious but why does the short circuiting break const-ness?
Short circuiting introduces conditional branching. If you call a function on the right hand side of a || or && it might or might not be executed depending on the value of the left hand side.
Until this version of rust, all conditional branches were banned from const functions.
I guess to keep things simple they just banned any feature that might cause branching.
They're moving to a Rust Foundation with corporate sponsorship model. I think Rust will be fine, even Amazon expressed interest in sponsoring development.
Hear hear. System languages don't grow on trees. Rust has had a lot of non-trivial effort put into it and is very usable right now . Somebody is going to see the value just lying around and is going to pick up the financial slack. I see it as vaguely analogous to the current movie theater situation in the US. A lot of companies are seeing the end of their business, but all of those buildings are still sitting around…
What's baffling to me is how scott's comment is [flagged] and [dead].
You trully can't have unconfortable opinions about Rust here. That's blatant censorship.
Replying to you since I don't see a reply button to his comment.
> supports a much larger set of features that even constexpr supports This sounds promising. Can you give examples? I don't know Rust at all, and the reason I like C++ is its metaprogrammability.
Basically, the interpreter interpret's rustc's internal IR, so it can theoretically support the entire language. That's not a good idea for various reasons, though, so its capabilities are effectively on an allowlist, that we expand over time as we're sure we want to enable a given feature.
That seems like a really good design, as opposed to having an AST interpreter like I might do otherwise. But would this indeed support a "much larger set of features" than constexpr as was claimed?
I’m learning rust right now and there is a lot to like. Steady updates like this are also very motivating. The ecosystem feels very sane - especially compared to npm. Top notch Wasm support, cross compiling is a breeze. That said, coming from a FP background (mostly Haskell/JS, now TS) Rust is... hard. I do understand the basic rules of the borrow checker, I do conceptually understand lifetimes, but actually using th…
> The ecosystem feels very sane [] compared to npm
I wonder why && and || are not allowed in const functions? > All boolean operators except for && and || which are banned since they are short-circuiting. I guess I'm missing something obvious but why does the short circuiting break const-ness?
Short circuiting introduces conditional branching. If you call a function on the right hand side of a || or && it might or might not be executed depending on the value of the left hand side. Until this version of rust, all conditional branches were banned from const functions. I guess to keep things simple they just banned any feature that might cause branching.
Ahh that makes a lot of sense, if you're going to have a compiler insert the result of a function having conditional branching seems a bit gnarly I guess?
So, I want to learn Rust. I am a C# / Python programmer, experienced. Are there any particular set of problems that I can solve systematically, so that I can learn all the features of Rust?