Venkat Subramaniam - Programming DSLs in Kotlin

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Were living in a rather unusual time, through a global pandemic combined with many regional issues. In hindsight, writing this book has given me a much needed reprieve, however temporary. The time spent on this book and interacting with Jackie, my editor, and the reviewers has been the high point of these months.

I would like to start by thanking Andy Hunt and Dave Rankin of the Pragmatic Bookshelf for giving me this opportunity. Dave was incredibly supportive and helpful in the formation of this book. His constructive feedback through every step was very useful.

Part of my motivation to write books is the opportunity to interact with Jackie, who, over time, has turned into a good friend. I admire her ability to put in such tireless efforts while dealing with many uncertainties of the current times. Thank you for spending time talking about the book and for motivating me when things appeared rather bleak.

This book has evolved so much based on the extensive feedback by an amazing set of technical reviewers. They offered so many suggestions, corrected me where the details were not accurate, and motivated me to rework parts that needed significant improvements. My sincere thanks to Tom Adam, Vasile Boris, Hadi Hariri, James Harmon, Rebecca Parsons, Eugene Petrenko, Ian Roughley, William Rudenmalm, Ilya Ryzhenkov, Giordano Scalzo, Ken Sipe, and Bruce Tate.

One benefit of releasing the book in beta is the opportunity to improve it using the feedback from early readers. I thank Graeme Collis and Curtis Riggs for helping me to fix errors.

I thank my wife Kavitha for her support and letting me hide in the basement hours on end as I worked on this book.

Fluent, concise, expressive code, and low ceremony are some the traits of good domain-specific languages (DSLs). Creating a DSL is twice the joywe can write elegant code, which in turn can help our domain experts work with ease and convenience.

In this book youll learn how to design and implement your own DSLs using Kotlin. Ive kept it really short so we can cut to the chase and get to implementing DSLs. Multiple examples will guide you through the essentials. Make sure to key in and execute each one of them to gain practice. Thank you for joining me on this journey.

This book assumes you are familiar with Kotlin and have some reasonable understanding of DSLs. Its intended to quickly guide you through the steps necessary to build DSLs using Kotlin for JVM or Android applications.

If youre a programmer interested in using Kotlin to build DSLs, you picked the right book. Youll also find this book useful if youre a lead developer, architect, or a technical manager who is involved in the development of applications that make use of DSLs.

You may also use this book to train your developers to become proficient with using Kotlin for programming DSLs.

Weve intentionally kept this book short to help you to quickly pick up key tips and tricks to create DSLs using Kotlin.

This book will not serve as an introduction to Kotlin nor to DSLs, as it assumes some knowledge of both. For an introduction to Kotlin refer to .

After a quick introduction of the steps to create DSLs with Kotlin, well dive straight into each of the steps. Well first focus on making the syntax fluent by exploiting the flexibilities of Kotlin. Then well look at ways to bring domain-specific vocabulary into your DSLs. Following that well devise ways to bring multiple contexts into the execution environments. Well then walk through the steps to make DSLs robust and resilient. Finally, well wrap with a few more examples of designing DSLs.

Each step of the way, well look at a number of code examples for you to practice along with. Take the time to key in each example, compile it, and execute it. Pause to make changes, break it, put it back together, try some variations, and then walk along to the next tip or trick to design your DSLs.