rust

问题 I'm getting an error when trying to use a closure that does exactly the same as the print function below (in ln.9) The error is the usual borrowed value does not live long enough . I've tried to replicate this in the playground but I can't. I'm certain that this is mainly because I don't really understand what's going on here so any help would be really appreciated. What I can't understand is what is the difference between calling the print function and calling the check closure. They have

问题 I have a bunch of long immutable strings, which I would like to store in a HashSet . I need a bunch of mappings with these strings as keys. I would like to use references to these strings as keys in these mappings to avoid copying strings. This is how I managed to eventually get to this status. The only concern is this extra copy I need to make at line 5. let mut strings: HashSet<String> = HashSet::new(); // 1 let mut map: HashMap<&String, u8> = HashMap::new(); // 2 // 3 let s = "very long

问题 I have a bunch of long immutable strings, which I would like to store in a HashSet . I need a bunch of mappings with these strings as keys. I would like to use references to these strings as keys in these mappings to avoid copying strings. This is how I managed to eventually get to this status. The only concern is this extra copy I need to make at line 5. let mut strings: HashSet<String> = HashSet::new(); // 1 let mut map: HashMap<&String, u8> = HashMap::new(); // 2 // 3 let s = "very long

问题 I'm trying to speed up a data pipeline using Rust. The pipeline contains bits of Python code that I don't want to modify, so I'm trying to run them as-is from Rust using rust-cpython and multiple threads. However, the performance is not what I expected, it's actually the same as running the python code bits sequentially in a single thread. Reading the documentation, I understand when invoking the following, you actually get a pointer to a single Python interpreter that can only be created

问题 I'm trying to speed up a data pipeline using Rust. The pipeline contains bits of Python code that I don't want to modify, so I'm trying to run them as-is from Rust using rust-cpython and multiple threads. However, the performance is not what I expected, it's actually the same as running the python code bits sequentially in a single thread. Reading the documentation, I understand when invoking the following, you actually get a pointer to a single Python interpreter that can only be created

问题 I am trying to add pagination using Diesel. The compiler is able to check bounds on a generic type if I use a function but isn't if I try to do the same as an implementation of a trait. This is a simple working example: use diesel::query_dsl::methods::{LimitDsl, OffsetDsl}; pub fn for_page<T>(query: T) where T: OffsetDsl, T::Output: LimitDsl, { query.offset(10).limit(10); } OffsetDsl and LimitDsl are Diesel's traits which provides the methods offset and limit . When I try to extract this

问题 I am trying to add pagination using Diesel. The compiler is able to check bounds on a generic type if I use a function but isn't if I try to do the same as an implementation of a trait. This is a simple working example: use diesel::query_dsl::methods::{LimitDsl, OffsetDsl}; pub fn for_page<T>(query: T) where T: OffsetDsl, T::Output: LimitDsl, { query.offset(10).limit(10); } OffsetDsl and LimitDsl are Diesel's traits which provides the methods offset and limit . When I try to extract this

问题 I am trying to write a separate function to render text using piston2d. Taking the hello_world.rs example, I am trying to extend that to allow me to render text from within a function. Here is the code that I wrote: extern crate piston_window; extern crate find_folder; use piston_window::*; fn main() { let mut window: PistonWindow = WindowSettings::new( "piston: try to render text", [200, 200] ) .exit_on_esc(true) .build() .unwrap(); let assets = find_folder::Search::ParentsThenKids(3, 3)

问题 I'd implementing a simple linked list. This is the (working) code I had so far: pub struct LinkedList<T> { start: Option<Box<Link<T>>>, } impl<T> LinkedList<T> { pub fn new() -> LinkedList<T> { return LinkedList { start: None }; } } struct Link<T> { value: Box<T>, next: Option<Box<Link<T>>>, } impl<T> Link<T> { fn new_end(value: T) -> Link<T> { return Link::new(value, None); } fn new(value: T, next: Option<Box<Link<T>>>) -> Link<T> { return Link { value: Box::new(value), next, }; } } Next on

问题 In many languages, a common constructor idiom is to initialize values of an object using syntax like this pseudocode: constructor Foo(args...) { for arg { object.arg = arg } } Rust at first seems to be no exception. Many impl for a struct include a constructor named new to zip an ordered series of arguments onto the fields of the struct: struct Circle { x: i32, y: i32, radius: i32, } impl Circle { fn new(x: i32, y: i32, radius: i32) -> Circle { Circle { x: x, y: y, radius: radius } } } Doing