Here’s a Minimal, Reproducible Example that exhibits the same problem that you experienced. I created a C library exporting a simple addition function. I also created a Cargo project to use this function. dynlink/ ├── executable │ ├── build.rs │ ├── Cargo.lock │ ├── Cargo.toml │ └── src │ └── main.rs └── library ├── … Read more
The other answers are outdated. As of Rust 1.27, you can use HashMap::retain to keep only the elements you are interested in. You specify the elements to keep using a closure. x.retain(|_, v| *v != 0);
This can be done with the action attribute. If your field is a bool then by default the action selected is ArgAction::SetTrue. This is quite nice since you don’t need to set a value when you call the argument. It sets the value by default to true if used and false if not used when … Read more
You can also implement hex encoding and decoding yourself, in case you want to avoid the dependency on the hex crate: use std::{fmt::Write, num::ParseIntError}; pub fn decode_hex(s: &str) -> Result<Vec<u8>, ParseIntError> { (0..s.len()) .step_by(2) .map(|i| u8::from_str_radix(&s[i..i + 2], 16)) .collect() } pub fn encode_hex(bytes: &[u8]) -> String { let mut s = String::with_capacity(bytes.len() * 2); … Read more
Since Rust 1.19 (cargo 0.20.0), thanks to https://github.com/rust-lang/cargo/pull/3929, you can now define a compile-time environment variable (env!(…)) for rustc and rustdoc via: println!(“cargo:rustc-env=KEY=value”); So OP’s program can be written as: // build.rs use std::process::Command; fn main() { // note: add error checking yourself. let output = Command::new(“git”).args(&[“rev-parse”, “HEAD”]).output().unwrap(); let git_hash = String::from_utf8(output.stdout).unwrap(); println!(“cargo:rustc-env=GIT_HASH={}”, git_hash); } … Read more
None of the standard library collections maintain insertion order. You can instead use IndexMap from the indexmap crate, which preserves insertion order as long as you don’t call remove. use indexmap::indexmap; let map = indexmap! { “Z” => 1, “T” => 2, “R” => 3, “P” => 4, “K” => 5, “W” => 6, }; … Read more
Anything starting with & in Rust is a reference to a value, rather than a value itself. A &[u8] is a reference to a value which needs to exist elsewhere. Because you create the value it’s a reference to within the function, when the function returns, the value the reference points to no longer exists. … Read more
This doesn’t work because we can’t move s from &mut X. Then don’t do that… take the struct by value and return a new one: enum X { X1(String), X2(String), } fn increment_x(x: X) -> X { match x { X::X1(s) => X::X2(s), X::X2(s) => X::X1(s), } } Ultimately, the compiler is protecting you because … Read more
Because it was initially supported and never removed: It’s more like we never forbade shadowing, since it just fell out of the implementation of the compiler. As I recall, Graydon floated the idea of forbidding shadowing, but I stuck up for the feature, nobody else really cared, and so it stayed. – pcwalton See also: … Read more
Check the Path::file_stem method. You can find an example there. It works at least from Rust 1.6.