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Professional Scala

By : Hartmann, Shevchenko

4.2 (13)

Professional Scala

4.2 (13)

By: Hartmann, Shevchenko

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.

Preface

Preface

Who This Book Is For

What This Book Covers

Conventions

Installation and Setup

Installing IntelliJ IDE

Installing Scala plugin (make heading)

Reader Feedback

Customer Support

Free Chapter

1. Setting up the Development Environment

1. Setting up the Development Environment

Simple Program

Structure of a Scala Project

Base Syntax

Unit Testing

Summary

2. Basic Language Features

2. Basic Language Features

Objects, Classes, and Traits

OO in Our Chatbot

Function Calls

Summary

3. Functions

3. Functions

Functions

Exploring Pattern Matching

Partial Functions in Practice

Summary

4. Scala Collections

4. Scala Collections

Working with Lists

Abstracting on Sequences

Other Collections

Summary

5. Scala Type System

5. Scala Type System

Type Basics and Polymorphism

Variance

Advanced Types

Summary

6. Implicits

6. Implicits

Implicit Parameters and Implicit Conversions

Ad Hoc Polymorphism and Type Classes

Summary

7. Functional Idioms

7. Functional Idioms

Introduction to Functional Programming Concepts

Functional Design Patterns

Popular Libraries

Summary

8. Domain Specific Languages

8. Domain Specific Languages

DSLs and Types of DSLs

ScalaTest – A Popular DSL

Language Features for Writing DSLs

Writing a Small DSL

Beyond This Book

Summary

Index

Index

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Functions

In this section, we will introduce the fundamentals of functional programming, such as function values and high-order functions.

Function Values

What is a function? We are familiar with methods, which must be defined in a scope (class or objects):

  def f1(x:Int, y:Int): Int =  x + y

In Scala, we can also define a function value:

   val f2: (Int,Int) => Int = (x,y) => (x+y).

Here, we define the function value, with a type of (Int,Int) => Int. Of course, as with all type declarations, the type can be omitted if it can be deduced from the context. So, an alternative syntax for this can be:

   val f2 = (x:Int,y:Int) => (x+y).

Both f1(1,2) and f2(1,2) will force evaluation. The difference between f1 and f2 is that the second is a value, which can be stored in a variable or passed to another function.

Functions which accept other functions as parameters are named high-order functions, for example:

def twice(f: Int => Int): Int => Int = x => f(f(x))

This function...

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