Book Image

Scala Programming Projects

By : Mikael Valot, Nicolas Jorand
Book Image

Scala Programming Projects

By: Mikael Valot, Nicolas Jorand

Overview of this book

Scala Programming Projects is a comprehensive project-based introduction for those who are new to Scala. Complete with step-by-step instructions and easy-to-follow tutorials that demonstrate best practices when building applications, this Scala book will have you building real-world projects in no time. Starting with the fundamentals of software development, you’ll begin with simple projects, such as developing a financial independence calculator, and then advance to more complex projects, such as a building a shopping application and a Bitcoin transaction analyzer. You’ll explore a variety of Scala features, including its OOP and FP capabilities, and learn how to write concise, reactive, and concurrent applications in a type-safe manner. You’ll also understand how to use libraries such as Akka and Play. Furthermore, you’ll be able to integrate your Scala apps with Kafka, Spark, and Zeppelin, along with deploying applications on a cloud platform. By the end of the book, you’ll have a firm foundation in Java programming that’ll enable you to solve a variety of real-world problems, and you’ll have built impressive projects to add to your professional portfolio.
Table of Contents (18 chapters)
Title Page
Copyright and Credits
Packt Upsell
Contributors
Preface
Index

Ensuring referential transparency


 We say that an expression is referentially transparent when it can be replaced by its value without changing the program's behavior, in any context. When an expression is a function call, it means that we can always substitute this function call with the return value of the function. A function that guarantees this in any context is called a pure function.

A pure function is like a mathematical function—the return value depends only on the arguments passed to the function. You do not have to consider anything else about the context in which it is called.

Defining pure functions

In the following code,  the pureSquare function is pure:

def pureSquare(x: Int): Int = x * x
val pureExpr = pureSquare(4) + pureSquare(3)
// pureExpr: Int = 25

val pureExpr2 = 16 + 9
// pureExpr2: Int = 25

The functions called pureSquare(4) and pureSquare(3) are referentially transparent—when we replace them with the return value of the function, the program's behavior does not change...