Book Image

Mastering Rust - Second Edition

By : Rahul Sharma, Vesa Kaihlavirta
Book Image

Mastering Rust - Second Edition

By: Rahul Sharma, Vesa Kaihlavirta

Overview of this book

Rust is an empowering language that provides a rare combination of safety, speed, and zero-cost abstractions. Mastering Rust – Second Edition is filled with clear and simple explanations of the language features along with real-world examples, showing you how you can build robust, scalable, and reliable programs. This second edition of the book improves upon the previous one and touches on all aspects that make Rust a great language. We have included the features from latest Rust 2018 edition such as the new module system, the smarter compiler, helpful error messages, and the stable procedural macros. You’ll learn how Rust can be used for systems programming, network programming, and even on the web. You’ll also learn techniques such as writing memory-safe code, building idiomatic Rust libraries, writing efficient asynchronous networking code, and advanced macros. The book contains a mix of theory and hands-on tasks so you acquire the skills as well as the knowledge, and it also provides exercises to hammer the concepts in. After reading this book, you will be able to implement Rust for your enterprise projects, write better tests and documentation, design for performance, and write idiomatic Rust code.
Table of Contents (19 chapters)

Repetitions in macros

Apart from token tree types, we also need a way to repeatedly generate certain parts of our code. One of the practical examples from the standard library is the vec![] macro, which relies on repetition to give an illusion of variadic arguments, and allows you to create Vecs in any of the following manners:

vec![1, 2, 3];
vec![9, 8, 7, 6, 5, 4];

Let's see how vec! does this. Here's vec's macro_rules! definition from the standard library:

macro_rules! vec {
($elem:expr; $n:expr) => (
$crate::vec::from_elem($elem, $n)
);
($($x:expr),*) => (
<[_]>::into_vec(box [$($x),*])
);
($($x:expr,)*) => (vec![$($x),*])
}

By ignoring the details to the right of => and focusing on the last two matching rules on the left-hand side, we can see something new in these rules:

($($x:expr),*)
($($x:expr,)*)

These are repeating...