Book Image

Professional Scala

By : Mads Hartmann, Ruslan Shevchenko
Book Image

Professional Scala

By: Mads Hartmann, Ruslan Shevchenko

Overview of this book

This book teaches you how to build and contribute to Scala programs, recognizing common patterns and techniques used with the language. You’ll learn how to write concise, functional code with Scala. After an introduction to core concepts, syntax, and writing example applications with scalac, you’ll learn about the Scala Collections API and how the language handles type safety via static types out-of-the-box. You’ll then learn about advanced functional programming patterns, and how you can write your own Domain Specific Languages (DSLs). By the end of the book, you’ll be equipped with the skills you need to successfully build smart, efficient applications in Scala that can be compiled to the JVM.
Table of Contents (12 chapters)

Advanced Types

If you have come from Java, most of these things may not be surprising. As such, let's look at some other features of Scala's type system.

Abstract Type Members

Abstract type members are type members of an object or class that are left abstract. They can provide some abstraction without the verbosity of type parameters. If a type is intended to be used existentially in most cases, we can cut some verbosity by using a type member instead of a parameter.

class Operator {
  type ToolOfChoice

class Susan extends Operator {
  type ToolOfChoice = Hammer

class Operator[ToolOfChoice]
class Susan extends Operator[ToolOfChoice]

You can refer to an abstract type variable using the hash operator:

scala> val tool: Susan#ToolOfChoice = new Hammer
tool: Hammer = Hammer@d8756ac

Structural Types

Scala supports structural types: type requirements that are expressed by an interface structure instead of a concrete type. Structural typing provides a feature similar to what dynamic languages...