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
Dedication
Packt Upsell
Contributors
Preface
Index

Pipes


pipe function takes a T value and invokes(T) -> R function with it:

import arrow.syntax.function.pipe

fun main(args: Array<String>) {
    val strong: (String) -> String = { body -> "<strong>$body</strong>" }

   "From a pipe".pipe(strong).pipe(::println)
}

A pipe is similar to function composition, but instead of generating new functions, we can chain function invocations to produce new values, reducing nesting calls. Pipes are known in other languages, such as Elm and Ocaml, as the operator |>:

fun main(args: Array<String>) {
   splitter(filterBills(calculatePrice(Quote(20.0, "Foo", "Shoes", 1)))) //Nested

   Quote(20.0, "Foo", "Shoes", 1) pipe ::calculatePrice pipe ::filterBills pipe ::splitter //Pipe
}

Both lines are equivalent, but the first one must be understood backwards and the second one should read from left to right:

import arrow.syntax.function.pipe
import arrow.syntax.function.pipe3
import arrow.syntax.function.reverse

fun main(args...