Which isn't the case, because who would add new dependency just to implement his traits for
Either?
anyway @David-OConnor I'm not sure what your use case is exactly for returning either a single element or a vec of them, but you can just wrap the single element in a vec and check if there's just one element or create an enum that better describes your domain
I would not suggest using an
Either here since by convention one "side" is used for errors
Hello!
I have a tiny question about the tokio library.
I'm trying to find a more idiomatic way to do the following:
let msg: Result<WsMsg, WebSocketError> = serde_json::from_str(&msg)
.map_err(|e| ResponseError("The server has replied with an unknown message"));
if msg.is_err() {
return err(msg.unwrap_err());
}
let msg = msg.unwrap();I've tried using the ? operator on the FuturesResult returned by err, but for some reason FuturesResult doesn't implement the Try trait.
i.e. sometimes it is not success and error
Hello Rustaceans! To implement Clone for a Box of a trait instance with a specific lifetime, what's the best practice? Example:
trait SomeTrait: Clone + Sized {
fn some_method(&self) -> &bool;
}
#[derive(Clone)]
struct SomeStruct {
pub val: bool,
}
impl SomeTrait for SomeStruct {
fn some_method(&self) -> &bool {
&self.val
}
}
struct OtherStruct<'a> {
pub some_box: Box<'a + SomeTrait>,
}
fn main() {}This code will produce this:
error[E0038]: the trait `SomeTrait` cannot be made into an object
--> src/main.rs:16:5
|
16 | pub some_box: Box<'a + SomeTrait>,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `SomeTrait` cannot be made into an object
|
= note: the trait cannot require that `Self : Sized`
Maybe an usage example is a
Vec with different implementations of SomeTrait?
If you remove
: Clone + Sized bound, your code will compile as expected, but I'm not sure if you need it too...
one thing you can do is add custom
clone method to your trait
and use that
why do you want to clone dynamic object though?
For example:
trait SomeTrait {}
struct Foo {}
impl SomeTrait for Foo {}
struct Bar {}
impl SomeTrait for Bar {}
struct SomeStruct<'a> {
some_attr: Vec<Box<'a + SomeTrait>>,
}
impl<'a> SomeStruct<'a> {
pub fn some_method(&self) -> Vec<Box<SomeTrait>> {
self.some_attr.clone();
}
}
I'd instead return
&[Box<SomeTrait>] and use it where possible
As I said, one option is to have custom method that would clone anything into such box, and then you can make cloning to work...
And you could probably even separate it out into its own base trait and provide blanket implementation to avoid reimplementing this manually...
Let me try something
So something like this is not pretty, but it works, even with
derive(Clone): https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=4e96609149bce63ae5ad428db14413c3
Thanks for the help!
hi, I am writing blas functions in assembly to use in rust I have this project https://github.com/ozgurakkurt/aquila. When I run
cargo bench sscal is as fast as openblas but when I run RUSTFLAGS="-C target-cpu=native" cargo bench It is 2x slower than openblas. Does anyone know why target-cpu=native is slowing my code?
@ozgurakkurt thats a really general question, but some computers have been shown to perform worse when using AVX512 (https://blog.cloudflare.com/on-the-dangers-of-intels-frequency-scaling/ and https://lemire.me/blog/2018/04/19/by-how-much-does-avx-512-slow-down-your-cpu-a-first-experiment/)
it seems counter-intuitive, but sometimes this is the case
it may be preferable to target just AVX-2 and not AVX-512
this will depend on your workload
also, it might be that the benchmark isnt representative of real-world scenarios
so it might be that it IS faster in certian situations, but just not the benchmark you have
just use that
