Advertisements The following code works: let a = [1, 2, 3].iter(); let b = iter::once(&456); for i in a.chain(b) { println!("{}", i); } Output: 1 2 3 456 But now, I need to change b (depending on some condition) to be either iter() or iter::once , e.g. let a = [1, 2, 3].iter(); let b… Read More Rust: how to combine iter(), iter::once(), and iter::empty()?

Advertisements I’m testing panic catch features in Rust. I have the following program: use std::panic; fn create_greeting(name: &str) -> String { //panic!("Oh no, something went wrong!"); let greeting = format!("Hello, {}!", name); return greeting; } fn main() { let mut msg: String; let result = panic::catch_unwind(|| { let name = "Alice"; msg = create_greeting(name); });… Read More Error "may not be safely transferred across an unwind boundary" when using catch_unwind in Rust

Advertisements I’m new to Rust(about a month), and this is my first time asking a question in this platform. please excusing me for making a few mistakes. Right now, I’m trying to make a save system that copies the whole directory. It looks like this: [File hierarchy] Documents tosave logs write_log (the thing I’m making)… Read More using std::fs::read_dir as an iterator in Rust

Advertisements I’m trying to get some data in the form of a &[u8], from either of two different sources: let result = if let Some(blob_id) = blob_id { let blob = get_blob(blob_id); Some(blob.data()) } else if let Some(file_path) = file_path { std::fs::read(file_path).ok().as_deref() } else { None }; Where: fn get_blob(blob_id: String) -> Blob {} impl… Read More How do I conditionally assign variables in rust?

Advertisements #![cfg(feature = "const_mut_refs")] //currently breaking my main function fn main() { println!("Hello, world!"); } Currently whenever I have this compiler flag on my nightly compiler my main function can’t be found. It gives me the error: "main function not found in crate insert_name_here consider adding a main function to src/main.rs" I don’t know who… Read More When I run a certain compiler flag the Rust compiler can't find my main

Advertisements Hi I am looking over the documentation of asnyc_task and notice that in the example code: use async_task::Runnable; use flume::{Receiver, Sender}; use std::rc::Rc; thread_local! { // A queue that holds scheduled tasks. static QUEUE: (Sender<Runnable>, Receiver<Runnable>) = flume::unbounded(); } // Make a non-Send future. let msg: Rc<str> = "Hello, world!".into(); let future = async… Read More How does this closure satisfy the trait bounds when it appears to drop a parameter

Advertisements I am a Rust learner. I want to make a function that multiplies an euclid::Vector3D<f64,U> by an f64. I have this code: use euclid::Vector3D; fn main() { fn scale_vector<f64,Unit>(vec: Vector3D::<f64, Unit>, scale: f64) -> Vector3D::<f64, Unit> { Vector3D::<f64, Unit>::new(vec.x * scale, vec.y * scale, vec.z * scale) } enum Meters {} let vec =… Read More error[E0369]: cannot multiply `f64` by `f64` in Rust

Advertisements I’m a new user of Rust and I am following the experimental book to learn it. I have read this chapter: https://rust-book.cs.brown.edu/ch04-04-slices.html, where they propose the following code: fn first_word(s: &String) -> usize { let bytes = s.as_bytes(); for (i, &item) in bytes.iter().enumerate() { if item == b’ ‘ { return i; } }… Read More Why do I need to use & in this code example

Advertisements I think I may just be stupid but I can’t figure this out. I have a function that takes a generic integer type T, I create a range using that type T and would like to collect that range into a Vec<T>. The issue is that I get the following error method cannot be… Read More Collect RangeInclusive<T> into Vec<T>

Advertisements I am a Rust beginner and I like the idea of having a construct like match were the exhaustiveness of what I write is checked but I incur in problems with the compiler for doing very simple things which are actually correct, like the following. How should I handle this situation? (Code explains itself… Read More Non exhaustive match (actually exhaustive)