INTRODUCTION

Save me from another "hello, world" book. Don't make me have to skim or skip through a half dozen chapters before I can get to something that's going to be useful to me. Or you, in this case. I can't tell you the number of programming books I've purchased over the decades, hoping to actually learn the language, only to end up just not using the book because it wasn't presented in a way that made a lot of sense to me. Instead of a dry explanation of how the language is constructed so you can try to put it all together in meaningful ways yourself, the purpose of this book is to jump straight into writing hopefully interesting or useful programs. Once we have the program, we can take a look at how it's constructed. You'll be learning by doing-or learning by example, if you prefer. I hope you'll find this a more useful and practical way of learning Rust.

Rust is an interesting language, as it turns out. Like so many other languages, it claims a C-like syntax, which is roughly correct but misses out on many important elements. Where Rust really shines is where C has introduced bad behavior in programming practices. This is more apparent as more have been using C as a language. Where C provides you with the gun and the bullets to shoot yourself in the foot, Rust provides you with necessary protections to keep you from injuring yourself or, from the perspective of the application, keeps the application from crashing. Rust is focused on protecting the memory space of the program, in part to provide a better ability for concurrent programming. After all, Rust is considered to be a systems programming language, meaning it is intended for applications that are lower level than those that a user directly interacts with.

In addition to protections provided to the programmer, Rust has a reasonably active community that can be used not only for support but also to get additional functionality for your programs. There are a lot of third-party libraries. These libraries can make your life easier by introducing you to functionality without you needing to write it yourself.

The idea behind this book is to introduce you to Rust in context, rather than via snippets that, by themselves, don't work. You need all the surround to fully understand what is happening in the program. You'll find this out when you are looking at example code sometimes. This is true with the Rust documentation: it's like you need to fully understand the language to understand the examples you are looking at. This book doesn't take that approach. It assumes that you don't know the language, so every line in every program is explained in as much detail as is necessary to pull it all apart, since Rust can be a dense language in some ways. This means single lines can pack a lot of meaning and functionality.

The one thing this book does not assume, though, is that you are coming to programming completely fresh. You will see examples for the programs written in Rust also presented in other programming languages. This may be helpful if you come from another language like C or Python, for instance, but want to learn Rust. Seeing the approach in a language you know before translating it into Rust may be beneficial. If you don't know those other languages, you can skip through those examples and jump to the explanation of how to write a program for the problem under discussion in Rust. You can still compare the other languages to Rust as you are going through so you can better understand Rust and how it is different from other languages.

OBTAINING RUST

Rust is a collection of programs that you will use. While a big part of it is the compiler, that's not the only program that will get installed. First, of course, is the compiler, rustc. This program will compile any Rust source code file, but more than that, it will compile complete executables. With some compiler programs, you have to compile source code files individually and then perform a step called linking, where you link all the source code files together along with any needed libraries to create the executable. If there is a reference to another source code file you have written as a module, the Rust compiler will compile all the modules and generate an executable without any additional intervention.

In practice, though, you probably won't use the Rust compiler directly. Instead, you'll use the cargo program. You'll want to get used to using cargo because it not only compiles your source code but also will manage any external dependencies. You will probably have libraries that are not part of the standard library. With languages like C and Python, you'd typically need to go get the library yourself and get it installed. You'd need to make sure it was installed in the right place, and then, in the case of C, you'd probably need to call the compiler in a way that made it clear you wanted to link in the external library so all the external references could get resolved and put into the resulting executable.

Rust is also a newer program, which means there are changes being made to it. You'll generally want to keep up-to-date on the newest Rust compiler. Your third-party libraries may be keeping up with the latest Rust changes, and if you aren't up-to-date, your program won't compile. You'll want the rustup utility to help manage your Rust installation.

If you are working on a Linux distribution, you may be inclined to use whatever package manager you have to install Rust. There's a better-than-good chance that your distribution has the Rust language in it. The problem is, once you install using the package manager, you may be held back by the package manager. The latest Rust software may not be available to you. It's easier to just install Rust without the Linux package manager. With operating systems like macOS and Windows, you don't even have a built-in package manager, so installing that way wouldn't be an option anyway.

The best approach is to go to the Rust website (www.rust-lang.org). For Unix-like operating systems, including Linux and macOS, there is a command-line string you will probably use to install. Because there is a chance this approach may change, it's best to just go to the website to get the right way. As of the writing of this book, the command used to install Rust on those operating systems follows. If you are on Windows, you can download an installer from the Rust website:

Once you have the Rust toolchain installed, you can keep it updated by using the command rustup update. This will always get the latest version of the Rust toolchain and make sure it is installed. You will also need to use a good source code editor. There are several available that will support Rust extensions, including Visual Studio Code, Atom, and Sublime. You should make sure you have installed the Rust extensions, which will help you with syntax highlighting and other features.

GETTING THE SOURCE CODE

As you work your way through this book, you will see primarily complete programs that are explained in context. You can certainly retype the programs from the book, and most are not that long. There is some value in retyping because it helps to ingrain the code and approach to programming used by Rust. However, it can be tedious to stare at a program and try to retype it. You may want to just start with the source code. It's all available on GitHub. GitHub is a source code repository site using the git source code management software. It was originally written to be used with the Linux kernel, as previous source code management software was not considered to be feature-rich enough. While there is other software available, git is most widely used today because public repositories like GitHub use git. To get the source code for this book, you can use the following command:

If you have a git client that you prefer to the command line, you can certainly use it. The command line is going to be the most common approach to grabbing source code from a git server.

NOTE The files are also available at www.wiley.com/go/beginningrust.

WHAT YOU WILL LEARN

The approach in this book is to write complete programs that are useful in some way, even if they are very simple starting points to more interesting programs. The idea is not to try to deconstruct enormous programs, so each chapter will tackle important ideas, but the programs presented may be limited. You will get important building blocks but maybe not large, complex programs. Each chapter will present some essential ideas in Rust and, sometimes, programming in general. Many chapters build on ideas from previous chapters. You can certainly read individual chapters since, in most cases, the program is still explained in detail, not always assuming you have read previous chapters.

The book doesn't exclusively cover the Rust programming language. Programming is about far more than language syntax. There is much more to programming than just how a language is constructed. This is especially true if you ever want to write software on a team-working with an open source project or being employed as a programmer. You need to be aware of how larger programs are constructed and ways to write software in a...