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.