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.

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Table of Contents (22 chapters)
Title Page
Title Page
Copyright and Credits
Copyright and Credits
Dedication
Dedication
Packt Upsell
Packt Upsell
Contributors
Contributors
Preface
Preface
Free Chapter
1
Kotlin – Data Types, Objects, and Classes
Kotlin – Data Types, Objects, and Classes
Classes
Inheritance
Abstract classes
Interfaces
Objects
Generics
Type alias
Nullable types
Kotlin's type system
Other types
Summary
2
Getting Started with Functional Programming
Getting Started with Functional Programming
What is functional programming?
Basics concepts
Functional collections
Implementing a functional list
Summary
3
Immutability - It's Important
Immutability - It's Important
What is immutability?
Immutable collections
The advantages of immutability
The disadvantages of immutability
Summary
4
Functions, Function Types, and Side Effects
Functions, Function Types, and Side Effects
Functions in Kotlin
Function types in functional programming
Lambda
High order functions
Pure functions and side effects
Summary
5
More on Functions
More on Functions
Single-expression functions
Parameters
Extension functions
Infix functions
Operator overloading
Type-safe builders
Inline functions
Recursion and corecursion
Summary
6
Delegates in Kotlin
Delegates in Kotlin
Introduction to delegation
Delegates in Kotlin
Property delegation (standard delegates)
Delegated map
Custom delegation
Local delegates
Class delegation
Summary
7
Asynchronous Programming with Coroutines
Asynchronous Programming with Coroutines
Introduction to coroutines
Using coroutines in real life
Channels
Managing mutable state
Summary
8
Collections and Data Operations in Kotlin
Collections and Data Operations in Kotlin
An introduction to collections
List and MutableList
Set and MutableSet
Map and MutableMap
Data operations in a collection
Grouping collections
Summary
9
Functional Programming and Reactive Programming
Functional Programming and Reactive Programming
Combining FP with OOP
Functional reactive programming
Getting started with RxKotlin
Observables
The Observable.create method
The Observable.from methods
Iterator<T>.toObservable
Subscriber – the Observer interface
Subscribing and disposing
Summary
10
Functors, Applicatives, and Monads
Functors, Applicatives, and Monads
Functors   
Monads
Applicatives
Summary
11
Working with Streams in Kotlin
Working with Streams in Kotlin
Introduction to Streams
Collections versus Streams
Working with Streams
Primitive streams
Stream factory methods
Collector and Stream.collect – collecting Streams
Summary
12
Getting Started with Arrow
Getting Started with Arrow
Function composition
Partial application
Reverse
Pipes
Currying
Logical complement
Memoization
Partial functions
Identity and constant
Optics
Summary
13
Arrow Types
Arrow Types
Option
Arrow's type hierarchy
Either
Monad transformers
Try
State
Summary
14
Kotlin's Quick Start
Kotlin's Quick Start
Writing and running Kotlin
Basic Kotlin syntax
Going further
Other Books You May Enjoy
Other Books You May Enjoy
Leave a review - let other readers know what you think
Index
Index

Function composition

One big part of functional programming as a concept is to use functions in the same way that we use any other type—as values, parameters, returns, and so on. One thing that we can do with other types is to take them as construction blocks to build other types; the same concept can be applied to functions.

Function composition is a technique to build functions using existing functions; similar to Unix pipes or channel pipelines, the result value of a function is used as a parameter for the next one.

In Arrow, function composition comes as a set of the infix extension functions:

Function

Description

compose

Takes the result of invoking the right-hand function as the parameter for the left-hand function.

forwardCompose

Takes the result of invoking the left-hand function as the parameter for the right-hand function.

andThen

Is an alias for forwardCompose.

 

Let's compose some functions:

import arrow.syntax.function.andThen
import arrow.syntax.function.compose
import arrow.syntax.function...
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