Table of Contents for

Nim in Action

About this Book

Nim in Action is a practical way to learn how to develop software using the open source Nim programming language. This book includes many examples, both large and small, to show and teach you how software is written in Nim.

Nim is unique. It’s multi-paradigm, and unlike most other languages, it doesn’t emphasize object-oriented programming. Because of this, I encourage you to consciously absorb the styles used in this book instead of applying your own. Nim in Action will teach you a set of best practices and idioms that you’ll also find useful in other programming languages.

By learning Nim, you’ll discover a language that straddles the lines between efficiency, expressiveness, and elegance. Nim will make you productive and your end users happy.

Who should read this book

This is by no means a beginner’s book. It assumes that you know at least one other programming language and have experience writing software in it. For example, I expect you to be aware of basic programming language features such as functions, variables, and types. The fundamentals of programming aren’t explained in this book.

This book will teach you how to develop practical software in the Nim programming language. It covers features that are present in all programming languages, such as concurrency, parallelism, user-defined types, the standard library, and more. In addition, it covers Nim features that you may not be familiar with, such as asynchronous input/output, metaprogramming, and the foreign function interface.

How the book is organized

The book is divided into three parts and includes a total of nine chapters.

Part 1 introduces the language and its basic features:

• Chapter 1 explains what Nim is, compares it to other programming languages, and discusses its strengths and weaknesses.
• Chapter 2 teaches the basics, such as the syntax and fundamental features of the language. This includes a demonstration of procedure definitions and exception handling.

Part 2 includes a wide range of examples to show how Nim is used in practice:

• Chapter 3 is where you’ll develop your first nontrivial Nim application. The primary purpose of this application is communication: it allows messages to be sent through a network. You’ll learn, among other things, how to create command-line interfaces, parse JSON, and transfer data over a network in Nim.
• Chapter 4 gives an overview of the standard library, particularly the parts of it that aren’t covered in other chapters but are useful.
• Chapter 5 discusses package management in Nim and teaches you how to create your own packages and make them available to others.
• Chapter 6 explains what parallelism is and how it can be applied to different programming tasks. You’ll see a parsing example, demonstrating different ways to parse data in Nim and how parsing can be parallelized.
• Chapter 7 is where you’ll develop your second nontrivial Nim application: a web application based on Twitter. You’ll learn how to store data in a SQL database and generate HTML.

Part 3 introduces some advanced Nim features:

• Chapter 8 looks at the foreign function interface and shows how it can be used to make use of C and JavaScript libraries. You’ll develop a simple application that draws the letter N on the screen, first using a C library and then using JavaScript’s Canvas API.
• Chapter 9 explains what metaprogramming is, discussing features such as generics, templates, and macros. At the end of this chapter, you’ll use macros to create a domain-specific language.

You may wish to skip the first two chapters if you already know the basics of Nim. I recommend reading the book from beginning to end, and I especially encourage you to follow along with the examples. Each chapter teaches you something new about Nim, even if it primarily focuses on a standalone example. If you get stuck, feel free to get in touch with me or the Nim community. Appendix A contains information on how to get help, so use it to your advantage.

Code conventions and downloads

The source code examples in this book are fairly close to the samples that you’ll find online, but for the sake of brevity, many of the comments were removed. The online samples include a lot of comments to make them as easy to understand as possible, so you’re encouraged to take a look at them to learn more.

The source code is available for download from the publisher’s website at https://manning.com/books/nim-in-action and from GitHub at https://github.com/dom96/nim-in-action-code. Nim is still evolving, so be sure to watch the repository for changes. I’ll do my best to keep it up to date with the latest Nim version.

This book contains many examples of source code, both in numbered listings and inline with normal text. In both cases, source code is formatted in a mono-spaced typeface like this, to distinguish it from ordinary text. Sometimes code is also in bold to highlight code that has changed from previous steps in the chapter, such as when a new feature is added to existing code.

In many cases, the original source code has been reformatted for print; we’ve added line breaks and reworked the indentation to accommodate the available page space in the book. In rare cases, even this was not enough, and listings include line-continuation markers (). Additionally, comments in the source code have often been removed from the listings when the code is described in the text.

Book forum

The purchase of Nim in Action includes free access to a private web forum run by Manning Publications, where you can make comments about the book, ask technical questions, and receive help from the author and from other users. To access the forum, go to https://forums.manning.com/forums/nim-in-action. You can also learn more about Manning’s forums and the rules of conduct at https://forums.manning.com/forums/about.

Manning’s commitment to our readers is to provide a venue where a meaningful dialogue between individual readers and between readers and the author can take place. It is not a commitment to any specific amount of participation on the part of the author, whose contribution to the forum remains voluntary (and unpaid). We suggest you try asking him some challenging questions lest his interest stray! The forum and the archives of previous discussions will be accessible from the publisher’s website as long as the book is in print.