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

Implementing a functional list

With everything that we've learned in the first two chapters, we can implement a pure functional list:

sealed class FunList<out T> {
   object Nil : FunList<Nothing>()

   data class Cons<out T>(val head: T, val tail: FunList<T>) : FunList<T>()

The FunList class is a sealed class; just two possible subclasses exist—Nil, an empty list (in other books you can see this defined as Null or Empty) and Cons (a construct, name inherited from Lisp, that holds two values).

The T type is marked out; this is for variance, which we'll cover variance in future chapters.

Nil is an object (we don't need different instances of Nil) extending FunList<Nothing> (remember that Nothing is the bottom of Kotlin's type hierarchy).

The Cons value contains two values—head, a single T, and tail, a FunList<T>; therefore, it can be a Nil value or another Cons.

Let's create a list instance as follows:

import com.packtpub.functionalkotlin.chapter02.FunList...