As described in the FFI guide, you can add attributes to structs to use the same layout as C: #[repr(C)] struct Object { a: i32, // other members } and you also have the ability to pack the struct: #[repr(C, packed)] struct Object { a: i32, // other members } And for detecting that the … Read more
Of course, you can do it – it’s just len is not a field, it’s a method: fn test_length(arr: &[String]){ if arr.len() >= 10 { // Do stuff } } If you only started learning Rust, you should read through the official book – you will also find why &[str] does not make sense (in … Read more
Your fundamental issue is that let can only be used in a function. So, wrapping the code in main(), and also fixing the style: fn if_statements() { let x = 5; let y = if x == 5 { 10 } else { 15 }; if y == 15 { println!(“y = {}”, y); } … Read more
Rust emits i1 to LLVM for bool and relies on whatever it produces. LLVM uses i8 (one byte) to represent i1 in memory for all the platforms supported by Rust for now. On the other hand, there’s no certainty about the future, since the Rust developers have been refusing to commit to the particular bool … Read more
As of Rust 1.21.0 and as mandated by RFC 1845, creating an Rc<str> or Arc<str> is now possible: use std::rc::Rc; use std::sync::Arc; fn main() { let a: &str = “hello world”; let b: Rc<str> = Rc::from(a); println!(“{}”, b); // or equivalently: let b: Rc<str> = a.into(); println!(“{}”, b); // we can also do this for … Read more
You cannot do it unless the C API allows passing a user-provided callback parameter. If it does not, you can only use static functions. The reason is that closures are not “just” functions. As their name implies, closures “close over” variables from their lexical scope. Each closure has an associated piece of data which holds … Read more
The syntax is like the str.format syntax in Python. This: fn main() { println!( “{0: <10} | {1: <10} | {2: <10} | {3: <10}”, “total”, “blanks”, “comments”, “code” ); println!(“{0: <10} | {1: <10} | {2: <10} | {3: <10}”, 0, 0, 0, 0); println!(“{0: <10} | {1: <10} | {2: <10} | {3: … Read more
char::to_digit(radix) does that. radix denotes the “base”, i.e. 10 for the decimal system, 16 for hex, etc.: let a = “29”; for c in a.chars() { println!(“{:?}”, c.to_digit(10)); } It returns an Option, so you need to unwrap() it, or better: expect(“that’s no number!”). You can read more about proper error handling in the appropriate … Read more
A deserialization error occurs because the struct definition is incompatible with the incoming objects: the color field can also be null, as well as a string, yet giving this field the type String forces your program to always expect a string. This is the default behaviour, which makes sense. Be reminded that String (or other … Read more
You need to import the trait that implements the flush method for Stdout. According to the documentation: Therefore: use std::io::Write; // <— bring the trait into scope fn main() { std::io::stdout().flush().expect(“some error message”); } Playground example