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

Basic Kotlin syntax

Kotlin syntax will look familiar to developers with experience of other languages based on C style syntax, such as C, Java, Scala, Groovy, and TypeScript.

General features

Various Kotlin features are common among other JVM Languages. If you have experience of Java, you'll feel at home with Kotlin.


Packages are sets of files (usually defined in the same directory) that define logic units, for example, controllers, and repositories.

To set a file in a particular package, use the package keyword in the first line:

package com.packt.functionalkotlin

Ideally, a file inside the package com.packt.functionalkotlin should be in the directory com/packt/functionalkotlin. It makes files easier to find but isn't mandatory in Kotlin.

String concatenation and interpolation

String concatenation in Kotlin uses the plus (+) operator:

val temperature = 12

println("Current temperature: " + temperature + " Celsius degrees")

String interpolation is an easy way to do complex concatenations: