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)

Language Features for Writing DSLs

In this section, we'll look at the Scala features that make it easy to write small DSLs:

  • Flexible syntax for method invocation

  • By-name parameters

  • Extension methods and Value classes

We'll use all of these features in the next section when we create our own DSL in Scala.

Flexible Syntax for Method Invocation

Scala has a flexible syntax for method invocations that makes it possible to, in some cases, omit the dot ( .) and parentheses ( ()) when invoking methods.

The rules are as follows:

  • For methods that are of arity- 0, meaning they don't take any parameters, the parentheses can be omitted and you can use the postfix notation.

  • For methods with an arity of 1 or more, meaning they take one or more parameters, it's possible to write the method using infix notation.

Here's an example of using infix notation when invoking filter:

List.range(0, 10).filter(_ > 5)
List.range(0, 10) filter (_ > 5)

And here's an example of omitting the parentheses when invoking...