Why Julia?

Julia was originally released in 2012 by Alan Edelman, Stefan Karpinski, Jeff Bezanson, and Viral Shah. It is a free and open source programming language.

Choosing a programming language is always subjective. For me, the following characteristics of Julia are decisive:

• Julia is developed as a high-performance programming language.

• Julia uses multiple dispatch, which allows the programmer to choose from different programming patterns adapted to the application.

• Julia is a dynamically typed language that can easily be used interactively.

• Julia has a nice high-level syntax that is easy to learn.

• Julia is an optionally typed programming language whose (user-defined) data types make the code clearer and more robust.

• Julia has an extended standard library and numerous third-party packages are available.

Julia is a unique programming language because it solves the so-called “two languages problem.” No other programming language is needed to write high-performance code. This does not mean it happens automatically. It is the responsibility of the programmer to optimize the code that forms a bottleneck, but this can done in Julia itself.

Who Is This Book For?

This book is for anyone who wants to learn to program. No formal prior knowledge is required.

New concepts are introduced gradually and more advanced topics are described in later chapters.

Think Julia can be used for a one-semester course at the high school or college level.

Conventions Used in This Book

The following typographical conventions are used in this book:

Italic

Indicates new terms, URLs, email addresses, filenames, and file extensions.

Constant width

Used for program listings, as well as within paragraphs to refer to program elements such as variable or function names, databases, data types, environment variables, statements, and keywords.

Constant width bold

Shows commands or other text that should be typed literally by the user.

Constant width italic

Shows text that should be replaced with user-supplied values or by values determined by context.

Using Code Examples

All code used in this book is available from a Git repository on GitHub. If you are not familiar with Git, it is a version control system that allows you to keep track of the files that make up a project. A collection of files under Git’s control is called a “repository.” GitHub is a hosting service that provides storage for Git repositories and a convenient web interface.

A convenience package is provided that can be directly added to Julia. Just type add https://github.com/BenLauwens/ThinkJulia.jl in the REPL in Pkg mode, see “Turtles”.

The easiest way to run Julia code is by going to https://juliabox.com and starting a free session. Both the REPL and a notebook interface are available. If you want to have Julia locally installed on your computer, you can download JuliaPro for free from Julia Computing. It consists of a recent Julia version, the Juno interactive development environment based on Atom, and a number of preinstalled Julia packages. If you are more adventurous, you can download Julia from https://julialang.org, install the editor you like (e.g., Atom or Visual Studio Code), and activate the plug-ins for Julia integration. To a local install, you can also add the IJulia package and run a Jupyter notebook on your computer.

This book is here to help you get your job done. In general, you may use example code in your programs and documentation. You do not need to contact us for permission unless you’re reproducing a significant portion of the code. For example, writing a program that uses several chunks of code from this book does not require permission. Selling or distributing a CD-ROM of examples from O’Reilly books does require permission. Answering a question by citing this book and quoting example code does not require permission. Incorporating a significant amount of example code from this book into your product’s documentation does require permission.

We appreciate, but do not require, attribution. An attribution usually includes the title, author, publisher, and ISBN. For example: “Think Julia by Ben Lauwens and Allen B. Downey (O’Reilly). Copyright 2019 Allen B. Downey, Ben Lauwens, 978-1-492-04503-8.”

If you feel your use of code examples falls outside fair use or the permission given above, feel free to contact us at [email protected].

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Acknowledgments

I really want to thank Allen for writing Think Python and allowing me to port his book to Julia. Your enthusiasm is contagious!

I would also like to thank the technical reviewers for this book, who made many helpful suggestions: Tim Besard, Bart Janssens, and David P. Sanders.

Thanks to Melissa Potter from O’Reilly Media, who made this a better book. You forced me to do things right and make this book as original as possible.

Thanks to Matt Hacker from O’Reilly Media, who helped me out with the Atlas toolchain and some syntax highlighting issues.

Thanks to all the students who worked with an early version of this book and all the contributors (listed below) who sent in corrections and suggestions.