Book Image

Functional Kotlin

Book Image

Functional Kotlin

Overview of this book

Functional programming makes your application faster, improves performance, and increases your productivity. Kotlin supports many of the popular and advanced functional features of functional languages. This book will cover the A-Z of functional programming in Kotlin. This book bridges the language gap for Kotlin developers by showing you how to create and consume functional constructs in Kotlin. We also bridge the domain gap by showing how functional constructs can be applied in business scenarios. We’ll take you through lambdas, pattern matching, immutability, and help you develop a deep understanding of the concepts and practices of functional programming. If you want learn to address problems using Recursion, Koltin has support for it as well. You’ll also learn how to use the funKtionale library to perform currying and lazy programming and more. Finally, you’ll learn functional design patterns and techniques that will make you a better programmer.By the end of the book, you will be more confident in your functional programming skills and will be able to apply them while programming in Kotlin.
Table of Contents (22 chapters)
Title Page
Copyright and Credits
Packt Upsell


Optics are abstractions to update immutable data structures elegantly. One form of optics is Lens (or lenses, depending on the library implementation). A Lens is a functional reference that can focus (hence the name) into a structure and read, write, or modify its target:

typealias GB = Int

data class Memory(val size: GB)
data class MotherBoard(val brand: String, val memory: Memory)
data class Laptop(val price: Double, val motherBoard: MotherBoard)

fun main(args: Array<String>) {
   val laptopX8 = Laptop(500.0, MotherBoard("X", Memory(8)))

   val laptopX16 = laptopX8.copy(
         price = 780.0,
         motherBoard = laptopX8.motherBoard.copy(
               memory = laptopX8.motherBoard.memory.copy(
                     size = laptopX8.motherBoard.memory.size * 2

   println("laptopX16 = $laptopX16")

To create a new Laptop value from an existing one, we need to use several nested copy methods and references. In this example, it isn't as...