Professional Scala

Combine object-oriented and functional programming to build high-performance applications

Mads Hartmann, Ruslan Shevchenko

• Publisher: Packt Publishing
• Year: 2018
• Print ISBN: 9781789533835
• eBook ISBN: 9781789534702
• Edition: 1
• Topic: Computer Science
• Subtopic: Programming in Java
• Index: Computer Science

If your application source code is overly verbose, it can be a nightmare to maintain. Write concise and expressive, type-safe code in an environment that lets you build for the JVM, browser, and more.

Key Features

• Expert guidance that shows you to efficiently use both object-oriented and functional programming techniques
• Understand functional programming libraries, such as Cats and Scalaz, and use them to augment your Scala development
• Perfectly balances theory and hands-on exercises, assessments, and activities

Book Description

This book teaches you how to build and contribute to Scala programs, recognizing common patterns and techniques used with the language. You'll learn how to write concise, functional code with Scala. After an introduction to core concepts, syntax, and writing example applications with scalac, you'll learn about the Scala Collections API and how the language handles type safety via static types out-of-the-box. You'll then learn about advanced functional programming patterns, and how you can write your own Domain Specific Languages (DSLs). By the end of the book, you'll be equipped with the skills you need to successfully build smart, efficient applications in Scala that can be compiled to the JVM.

What you will learn

• Understand the key language syntax and core concepts for application development
• Master the type system to create scalable type-safe applications while cutting down your time spent debugging
• Understand how you can work with advanced data structures via built-in features such as the Collections library
• Use classes, objects, and traits to transform a trivial chatbot program into a useful assistant
• Understand what are pure functions, immutability, and higher-order functions
• Recognize and implement popular functional programming design patterns

Who this book is for

This is an ideal book for developers who are looking to learn Scala, and is particularly well suited for Java developers looking to migrate across to Scala for application development on the JVM.

Professional Scala

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Table of Contents

Professional Scala

Why Subscribe?

PacktPub.com

Contributors

About the Authors

Preface

Who This Book Is For

What This Book Covers

What You Need for This Book

Conventions

Installation and Setup

Installing IntelliJ IDE

Installing Scala plugin (make heading)

Reader Feedback

Customer Support

Downloading the Example Code

Errata

Piracy

Questions

1. Setting up the Development Environment

Simple Program

Definitions: Packages, Imports, and Objects

Object Definition

The main Method

Inside main

Structure of a Scala Project

Basic sbt Commands

Activity: Performing Basic Operations with sbt: Build, Run, Package

IDE

Activity: Loading and Running a Sample Project in the IDE

REPL

Obtaining the Time Request from Our Chatbot Program

Base Syntax

Base Syntax for Definitions

Base Syntax for Expressions

Unit Testing

Adding a Test to Our Project

Inside Tests

Running Tests for Chatbot

Summary

2. Basic Language Features

Objects, Classes, and Traits

Object

Classes

Equality and Case Classes

Pattern Matching

Traits

Self-Types

Special Classes

OO in Our Chatbot

Decoupling Logic and Environment

Sealed Traits and Algebraic Datatypes

Function Calls

Syntax Goodies

Named Parameters

Default Parameters

Currying Forms (Multiple Argument Lists)

Special Magic Methods

Implementing + in CartesianPoint

Parameter-Passing Mode

By Value

By Name

By Need

Creating a Runnable Construction

Printing the log Argument to the Console and File

Summary

3. Functions

Functions

Function Values

Function from an OO Point of View

Conversions

Defining and Measuring the Time of a Unit Function

Syntax Sugar in a Function Definition

Partial Functions

Exploring Pattern Matching

Binding a Sequence of Variables in the Pattern Matcher

Partial Functions in Practice

Representing ChatbotMode as a Partial Function

Implementing RemindStore as a Set of Partial Functions

Using Lifting for Conversations between Total and Partial Functions

Summary

4. Scala Collections

Working with Lists

Constructing Lists

Operations on Lists

Pattern Matching on Lists

First-Order Methods on List

Appending and Concatenation

Taking the Length of a List

Reversing a List

Prefixes and Suffixes

Element Selection

Display

Activity: Creating a New Mode for Chatbot Using Lists

Abstracting on Sequences

The Traversable Trait

Iterators

Streams

Activity: Implementing Fibonacci Series Using Streams and Iterators

Other Collections

Sets

Tuples

Maps

Mutable and Immutable Collections

Activity: Implementing the Tower of Hanoi Problem

Summary

5. Scala Type System

Type Basics and Polymorphism

A Unified Type System

Parametric Polymorphism

Type Inference

Parameterized Types

Bounds

Existential Types

Activity: Generalizing the Implementation of the Binary Tree

Variance

Covariance

Contravariance

Invariance

Activity: Implementing Covariance and the Database for Tools

Advanced Types

Abstract Type Members

Structural Types

Option

Higher Kind Types

Type Erasure

Activity: Finding an Element Based on a Given Predicate

Summary

6. Implicits

Implicit Parameters and Implicit Conversions

Implicit Parameters

Implicit Conversions

Implicit Resolution

Activity: Creation of Extension Methods

Ad Hoc Polymorphism and Type Classes

Types of Polymorphism

Type Classes

Context Bounds and Implicitly

Type Classes in the Standard Library

Activity: Implementing Type Classes to Support Conversion

Summary

7. Functional Idioms

Introduction to Functional Programming Concepts

Pure Functions

Immutability

Implementing the standard library

Higher-Order Functions

Functional Design Patterns

Monoids

Using Monoids to Write Polymorphic Functions

Functor

Monads

Popular Libraries

Validating Data Using Cats

Prerequisites for Using Cats

Introduction to Cats

Validating Data

Validating Using Validated

Communicating with Databases Using Doobie

Prerequisites for Doobie

Doobie

ConnectionIO

Transactor

Selecting Rows

Querying Using Parameters

Deleting, Inserting, and Updating Rows

A Complete Example

Activity: Adding Priority to the Todo List

Summary

8. Domain Specific Languages

DSLs and Types of DSLs

External DSLs

Internal DSLs

ScalaTest – A Popular DSL

Adding ScalaTest to Your Project

Overview of ScalaTest Styles

Activity: Implementing ScalaTest Styles

Language Features for Writing DSLs

Flexible Syntax for Method Invocation

By-Name Parameters

Extension Methods and Value Classes

Writing a Small DSL

Modeling Test Cases

DSL for TestCase

Activity: Creating a DSL to Specify Assertions

Beyond This Book

Various Scala Libraries

Akka

Apache Spark

Shapeless

Uncovered Language Features

Macros

Def Macros

Implicit Macros

Quasiquotes

Reflection

Resources to Keep You Updated

Scala Improvement Process

Scala Times

Summary

Index

Professional Scala

Copyright © 2018 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

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Table of contents

• Professional Scala