Scala from Scratch: Understanding
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Scala from Scratch: Understanding

About the Book

Scala from Scratch: Understanding is the second in a series of two books that teach you the Scala programming language. Readers that have read Scala from Scratch: Exploration or have learned some Scala through other means will get a deeper understanding of the language features and underlying functional programming concepts that have been explored in the first book. You will also learn about important advanced language features that play a crucial role in many real-life Scala projects. While doing so, you'll get to know best practices that have been established over the years. By the end of the book, you will have a grasp of the language, its idioms, and common tools and techniques, allowing you to be a productive member in commercial or open-source Scala projects.

In this book you will learn more about algebraic data types and about pattern matching, and you will get insights into functional ways of error handling. You will learn about essential ideas of functional programming like currying and partial functional application. You will also explore advanced aspects of the Scala type system like covariance and contravariance, and how to employ the type class pattern when abstracting over concrete types. You will learn about the design of Scala's collections API and how to work with Scala collections effectively. You will get a good grasp of property-based testing, an alternative to example-based testing, and you will dive deeper into sbt, the standard build tool in the Scala ecosystem. You will also learn how to interact with the outside world in a purely functional way, and about different approaches at concurrent programming in Scala.

Some of the content in this book is based on The Neophyte's Guide to Scala. However, it has been heavily revised, and amended with a lot of new content. In some ways, you can think of it as a second, extended edition of that book — structured and written so that it builds on what readers have learned in Scala from Scratch: Exploration.

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About the Author

Daniel Westheide
Daniel Westheide

Daniel Westheide is a software engineer living in Berlin, Germany. He is a senior consultant at INNOQ and co-organizer of ScalaBridge Berlin, the Berlin chapter of the ScalaBridge organization. He cares about empathy and inclusivity, and about the ethical, social, and ecological consequences of his work.

On his website, he discusses functional programming, architecture, as well as anything related to the software development process. He is not only interested in programming languages, but also a human language enthusiast. Moreover, he is passionate about specialty coffee, social science fiction, and tabletop roleplaying games.


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Get the ebook and donate a free community copy. This can then be claimed by a member of a marginalised community who can currently not afford purchasing a copy of this book or someone who cannot pay for this book for other reasons.

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  • English

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About the Contributors

Ann-Marie Rechter
Ann-Marie Rechter

Freelance Illustrator and Designer

Ann-Marie is responsible for the cover illustration. She is a freelance illustrator and designer from Hamburg, Germany.

She regularly posts some of her artwork as illumarie_art on Instagram.

Table of Contents

  • Credits
  • Preface
  • 1. Algebraic data types
    • 1.1 Sum types
    • 1.2 Product types
    • 1.3 Combining sum types and product types
    • 1.4 Revisiting the guessing game
    • 1.5 A definition of algebraic data types
    • 1.6 Summary
  • 2. The price of subtyping
    • 2.1 Upper type bounds
    • 2.2 Covariance
    • 2.3 Contravariance
    • 2.4 Demystifying covariant and contravariant positions
    • 2.5 Invariance
    • 2.6 Lower type bounds
    • 2.7 Summary
  • 3. Pattern matching in depth
    • 3.1 Patterns everywhere
    • 3.2 Pattern matching anonymous functions
    • 3.3 Extractors
    • 3.4 Summary
  • 4. Functional error handling
    • 4.1 Just give it a Try
    • 4.2 Either this or that
    • 4.3 Summary
  • 5. Embracing functions
    • 5.1 Higher-order functions
    • 5.2 Partially applied functions
    • 5.3 Currying
    • 5.4 Summary
  • 6. Type classes
    • 6.1 A gentle approach to type classes
    • 6.2 Implicit resolution
    • 6.3 Type class usability
    • 6.4 Higher-kinded types
    • 6.5 Type classes in the standard library
    • 6.6 Summary
  • 7. The Scala collections library
    • 7.1 A travel guide
    • 7.2 Common collection tasks
    • 7.3 A tale of two dichotomies
    • 7.4 Choosing a collection type
    • 7.5 Summary
  • 8. Concurrency and asynchronous programming
    • 8.1 Welcome to the Future
    • 8.2 Futures in the real world
    • 8.3 The trouble with Future
    • 8.4 Summary
  • 9. Property-based testing
    • 9.1 From examples to properties
    • 9.2 Property-based testing as a design tool
    • 9.3 The good property
    • 9.4 Summary
  • 10. Epilogue
    • 10.1 Summary
    • 10.2 Where to go from here
    • 10.3 And what about Scala 3?
  • Appendix: An sbt primer
    • The minimal viable project
    • Setting expressions
    • Build definitions
    • Setting dependencies
    • Task expressions
    • An introduction to scopes
    • Library dependencies
    • Custom setting and task keys
    • sbt plugins
    • Summary
  • Notes

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