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


A function can have zero or more parameters. Our function, basicFunction, takes two parameters, as shown in the following code:

fun basicFunction(name: String, size: Int) {


Each parameter is defined as parameterName: ParameterType, in our example, name: String and size: Int. Nothing new here.


It gets interesting when parameters have two types that we have already covered—vararg and lambdas:

fun aVarargFun(vararg names: String) {

fun main(args: Array<String>) {
   aVarargFun("Angela", "Brenda", "Caroline")

A function with a parameter marked with the modifier, vararg can be called with zero or more values:

fun multipleVarargs(vararg names: String, vararg sizes: Int) {
// Compilation error, "Multiple vararg-parameters are prohibited"

A function can't have multiple vararg parameters, not even with different types.


We already discussed how, if a function's last parameter is a lambda, it can't be passed outside the parenthesis...