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


One way for two coroutines to communicate (or for a coroutine to the external world as with async) is throughDeferred<T>:

import kotlinx.coroutines.experimental.delay
import kotlinx.coroutines.experimental.launch
import kotlinx.coroutines.experimental.runBlocking

fun main(args: Array<String>) = runBlocking {
    val result = CompletableDeferred<String>()

   val world = launch {
      result.complete("World (from another coroutine)")

   val hello =launch {
      println("Hello ${result.await()}")


Deferreds are fine for single values, but sometimes we want to send a sequence or a stream. In that case, we can use ChannelChannel which is similar to BlockingQueue, but with suspending operations instead of blocking ones, also Channel can be close:

import kotlinx.coroutines.experimental.channels.*

fun main(args: Array<String>) = runBlocking<Unit> {
   val channel = Channel<String>()