Book Image

Mastering Functional Programming

By : Anatolii Kmetiuk
Book Image

Mastering Functional Programming

By: Anatolii Kmetiuk

Overview of this book

Functional programming is a paradigm specifically designed to deal with the complexity of software development in large projects. It helps developers to keep track of the interdependencies in the code base and changes in its state in runtime. Mastering Functional Programming provides detailed coverage of how to apply the right abstractions to reduce code complexity, so that it is easy to read and understand. Complete with explanations of essential concepts, practical examples, and self-assessment questions, the book begins by covering the basics such as what lambdas are and how to write declarative code with the help of functions. It then moves on to concepts such as pure functions and type classes, the problems they aim to solve, and how to use them in real-world scenarios. You’ll also explore some of the more advanced patterns in the world of functional programming such as monad transformers and Tagless Final. In the concluding chapters, you’ll be introduced to the actor model, which you can implement in modern functional languages, and delve into parallel programming. By the end of the book, you will be able to apply the concepts of functional programming and object-oriented programming (OOP)in order to build robust applications.
Table of Contents (17 chapters)

Pure functions

In the previous sections, we have shown you how mutations and side effects can make the code harder to read and write. In this section, we will introduce the notion of pure functions, that is, the functions that do not produce side effects. It is central to pure functional programming. The functional paradigm dictates that you should express your program with the help of functions that do not produce any side effects. How would you model a situation where you need to throw an exception with the help of a pure function? Take the familiar Soda Machine example.

This is the slightly shortened version of the Soda Machine example we encountered in our previous discussions on side effects:

var cans = 0
def insertCoin(): SodaCan =
if (cans > 0) { cans -= 1; new SodaCan }
else throw new RuntimeException("Out of soda cans!")
println(insertCoin())

We can avoid...