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Professional Scala

Professional Scala

By : Hartmann, Shevchenko
4.2 (13)
Buy this Book
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Professional Scala

Professional Scala

4.2 (13)
By: Hartmann, Shevchenko
Buy this Book

Overview of this book

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.
Table of Contents (10 chapters)
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Preface
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Preface
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Who This Book Is For
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What This Book Covers
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Conventions
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Installation and Setup
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Installing IntelliJ IDE
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Installing Scala plugin (make heading)
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Reader Feedback
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Customer Support
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1
1. Setting up the Development Environment
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1. Setting up the Development Environment
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Simple Program
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Structure of a Scala Project
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Base Syntax
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Unit Testing
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Summary
2
2. Basic Language Features
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2. Basic Language Features
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Objects, Classes, and Traits
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OO in Our Chatbot
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Function Calls
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Summary
3
3. Functions
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3. Functions
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Functions
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Exploring Pattern Matching
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Partial Functions in Practice
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Summary
4
4. Scala Collections
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4. Scala Collections
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Working with Lists
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Abstracting on Sequences
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Other Collections
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Summary
5
5. Scala Type System
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5. Scala Type System
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Type Basics and Polymorphism
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Variance
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Advanced Types
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Summary
6
6. Implicits
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6. Implicits
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Implicit Parameters and Implicit Conversions
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Ad Hoc Polymorphism and Type Classes
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Summary
7
7. Functional Idioms
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7. Functional Idioms
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Introduction to Functional Programming Concepts
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Functional Design Patterns
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Popular Libraries
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Summary
8
8. Domain Specific Languages
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8. Domain Specific Languages
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DSLs and Types of DSLs
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ScalaTest – A Popular DSL
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Language Features for Writing DSLs
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Writing a Small DSL
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Beyond This Book
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Summary
9
Index
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Index

Variance

Variance provides a way to constrain parameterized types. It defines a subtyping relationship between parameterized types based on the subtyping relationship of their component types.

Imagine that you have the following class hierarchy:

class Tool
class HandTool extends Tool
class PowerTool extends Tool
class Hammer extends HandTool
class Screwdriver extends HandTool
class Driller extends PowerTool
If we define a generic box:
trait Box[T] {
  def get: T
}

How can Box of Tools relate to one another? Scala provides three ways:

  • Covariant: Box[Hammer] <: Box[Tool] if Hammer <: Tool

  • Contravariant: Box[Tool] <: Box[Hammer] if Tool <: Hammer

  • Invariant: There's no subtyping relationship between Box[Tool] and Box[Hammer] independently of the subtyping relationship of Tool and Hammer

Covariance

Let's assume that we want to define a function called isSuitable, which takes a Box[HandTool] and tests if the box is suitable to accommodate the tool it attempts to box: 

def...
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Professional Scala
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