That’s simply the way it is. In Rust a trait must be in scope for you to be able to call its methods. As for why, the possibility of collisions is the reason why. All the formatting traits in std::fmt (Display, Debug, LowerHex, &c.) have the same method signature for fmt. For example; what would …
Rust 1.0 stable std::process::exit() does exactly that – it terminates the program with the specified exit code: use std::process; fn main() { for i in 0..10 { if i == 5 { process::exit(1); } println!(“{}”, i); } } This function causes the program to terminate immediately, without unwinding and running destructors, so it should be …
Rust 1.51 Use const generics: struct Vec<T: Sized, const COUNT: usize> { a: [T; COUNT], } Previous versions RFC 2000 — const generics introduces support for this and progress is tracked in issue #44580. If you look at the design of Rust, you will notice that it started first by tackling the hardest problems (memory-safe, …
In cases like this, it’s very useful to force the compiler to tell you the type of the variable. Let’s trigger a type error by assigning the closure argument to an incompatible type: array_iter.filter(|x| { let _: () = x; x == 2 }); This fails with: error[E0308]: mismatched types –> src/lib.rs:4:41 | 4 | …
Standard library futures Let’s use this as our minimal, reproducible example: async fn example() -> i32 { 42 } Call executor::block_on: use futures::executor; // 0.3.1 fn main() { let v = executor::block_on(example()); println!(“{}”, v); } Tokio Use the tokio::main attribute on any function (not just main!) to convert it from an asynchronous function to a …
Just use Duration and appropriate operator: use chrono::{Duration, Utc}; fn main() { let dt = Utc::now() + Duration::days(137); println!(“today date + 137 days {}”, dt); } Test on playground.
The command line solution may help you to configure your IDE: cargo +nightly test Provided, of course, that you have the nightly channel installed. If not, perhaps install it with rustup install nightly (no need to switch to it, but check you’re still on stable: rustup show).
Rust 1.x (see documentation): use std::io; use std::io::prelude::*; fn main() { let stdin = io::stdin(); for line in stdin.lock().lines() { println!(“{}”, line.unwrap()); } } Rust 0.10–0.12 (see documentation): use std::io; fn main() { for line in io::stdin().lines() { print!(“{}”, line.unwrap()); } } Rust 0.9 (see 0.9 documentation): use std::io; use std::io::buffered::BufferedReader; fn main() { let …
As of Rust 1.21.0, Vec::splice is available and allows inserting at any point, including fully prepending: let mut vec = vec![1, 5]; let slice = &[2, 3, 4]; vec.splice(1..1, slice.iter().cloned()); println!(“{:?}”, vec); // [1, 2, 3, 4, 5] The docs state: Note 4: This is optimal if: The tail (elements in the vector after range) …
This means you’ll be passing in a reference to the object, as opposed to moving the object itself. It’s important to distinguish this because if your function looked like: fn eat(self) { println!(“{} is done eating.”, self.name); } and you tried calling it then using the variable after, you’d get an error object = Foo::new(); …