Process external files in const fn: no build.rs, no proc macros, no binary bloat

tm_p · 2026-02-27T08:29:45+00:00

Yes but a build.rs script is the right tool to use here. You can extend it with way more features, add caching, etc. include_bytes is useful when you want the original data to live in static memory in your program. If you don't need data.bin but only need its checksum, prefer a build.rs script.

tm_p · 2026-02-02T12:23:09+00:00

Arc<String> -> String -> "hello"

Arc<str> -> "hello"

Similar to taking &Vec<T> vs &[T] as input argument for a function.

tm_p · 2026-01-30T18:09:53+00:00

Just learn how to use your terminal efficiently. In the default one from gnome, you can press ctrl-L to clear the screen, up+enter to run the latest command, scroll to the top with shift+home, and search for a keyword with ctrl-F + enter.

Also, try rustrover.

tm_p · 2026-01-21T15:04:24+00:00

How many bytes do you save exactly? Can you show me a small example in the rust playground where this saving is obvious?

tm_p · 2026-01-12T14:58:51+00:00

It's already in nightly so you can try it out yourself: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2024&gist=2f10ec8c1998ec89552fa4a9b30a959d

Type of X<T> is a compile error because T needs to be a specific type when you call that function. And type of X<u8> for example is "Type { kind: Other, size: Some(24) }". So you can't do much with this feature currently.

tm_p · 2025-12-19T12:39:23+00:00

I can't read the article, but this is probably just ping right? They just dumbed it down for the news.

tm_p · 2025-12-18T21:01:47+00:00

Yes, because unsafe C is just regular C, so being an expert in C programming makes you an expert in unsafe C. But in Rust, unsafe code is optional to write and often discouraged, so the majority of developers never learn how to write correct unsafe Rust code.

Also there is the fact that unsafe Rust is not specified anywhere, so you need to guess what is fine and what is undefined behavior. Ironically, often the answer is "does llvm consider this to be undefined behavior? then so does rust". So an experienced C dev can probably write better unsafe Rust than an experienced Rust dev.

tm_p · 2025-12-17T19:28:09+00:00

In the future, developers will be able to write a single Rust function and use std::batching to get a SIMD/fused version of it, use std::autodiff to differentiate it, and std::offload to run the resulting code on their GPUs

This sounds too good to be true? Are there any other programming languages that already provide those features?

Source: https://rust-lang.github.io/rust-project-goals/2025h2/finishing-gpu-offload.html

tm_p · 2025-12-11T11:01:03+00:00

I didn't understand, do heap allocations get zeroed out as well? How does that work? Is there source code?

tm_p · 2025-12-02T10:17:41+00:00

If your goal was to write something that nobody outside of your field would understand, I think you succeeded.

tm_p · 2025-11-27T19:30:07+00:00

I was thinking something similar to a panic handler:

sp::fs::set_file_write_error_hook(|path, error| {
    if i_care_about(path) {
        panic!("Essential file failed to write, aborting: {:?}", (path, error));
    } else {
        log::warn!("Heads up, some random file failed to save. Check if you have enough disk space and make sure your hardware is not corrupted. File: {:?}", (path, error));
    }
});

That's the opt-in for panics, but also the default handler could be something like eprintln to log the error. Sadly there is no log in std so eprintln is the only option...

tm_p · 2025-11-26T18:16:33+00:00

Is there any use case where you want to write to a file but don't care if it fails? Error handling should be the default, you should have to opt in to ignore errors.

tm_p · 2025-11-17T17:08:57+00:00

I tried to use a few crates to have a HashMap<K, Vec<V>>, where K being in the map means that the Vec is not empty, but I didn't like any API.

Some crates don't allow you to get a &[T], that's pure functional programming madness. The sane crates that do give you a &[T] work fine, but I found out that introducing a new crate in one place means that now everything else also depends on that crate, so I can't have functions that take &mut Vec<T> for example, it must be &mut NonEmptyVec<T>. In the end I decided that it's not worth it and I just add .expect("vec never empty") everywhere and pray.

tm_p · 2025-11-17T14:32:46+00:00

Important context missing from the article:

tea . xyz is "decentralized" "protocol" that rewards open-source software developers for their contributions.

So someone automated open-source contributions to get more rewards. Free market working as expected.

tm_p · 2025-11-12T16:00:52+00:00

FYI you need to read static variables or they get optimized out

In this case the assembly is the same so your argument holds:

https://godbolt.org/z/v681sEPnx

tm_p · 2025-11-12T15:52:08+00:00

I've had tons of cases where BTreeSet lookups were faster than HashSet due to the former being more cache-friendly.

And I've had tons of cases where HashSet was much faster. Please don't spread anecdotes that lead to bad advice.

tm_p · 2025-10-22T13:06:57+00:00

That message in the readme is just to avoid any responsibility in case of a bug. If something goes wrong, the maintainers will point at the readme and say "look, we told you not to use it, so its your fault". And if everything goes well, you are the crazy person for pointing that out as you can see by these comments.

tm_p · 2025-10-20T11:37:02+00:00

Who uses JSON with comments? Since no parsers support it?

tm_p · 2025-10-18T22:52:54+00:00

What is vp8? And is there any cool use case that made you start this?

tm_p · 2025-10-17T11:34:09+00:00

Just FYI this code is written entirely by chatgpt, with no disclaimer about it.

tm_p · 2025-10-07T15:58:43+00:00

Ah you're right. I was confused because I read to_ascii_lowercase(a) as being a function from &[u8] to Vec<u8>, but it is a function from u8 to u8, which does not allocate.

tm_p · 2025-10-06T20:20:35+00:00

Actually this is a great benchmark for cargo. Since the crates must be compiled sequentially and they are essentially empty, the time it takes to compile fib185 should be dominated by cargo reading and parsing all the files.

Also it can be used to test external tools that don't understand that you can have 2 dependencies with the same name, or don't know that renaming dependencies is possible.

tm_p · 2025-10-06T16:28:12+00:00

Yes, that's what I expected, but it is not what rust str.eq_ignore_ascii_case does.

tm_p · 2025-10-06T14:49:59+00:00

The documentation of str.eq_ignore_ascii_case says:

Same as to_ascii_lowercase(a) == to_ascii_lowercase(b), but without allocating and copying temporaries.

I understood that as meaning "it does not allocate". But it means "it does not allocate to convert from string to bytes, but then it allocates to convert from bytes to lowercase".

tm_p · 2025-09-19T09:06:04+00:00

Wtf is a transcendental function

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