Foreword

I Introduction to Scala	13
1 Hands-on Scala	15
2 Setting Up	25
3 Basic Scala	39
4 Scala Collections	59
5 Notable Scala Features	81

II Local Development	105
6 Implementing Algorithms in Scala	107
7 Files and Subprocesses	127
8 JSON and Binary Data Serialization	147
9 Self-Contained Scala Scripts	163
10 Static Build Pipelines	179

III Web Services	201
11 Scraping Websites	203
12 Working with HTTP APIs	219
13 Fork-Join Parallelism with Futures	237
14 Simple Web and API Servers	259
15 Querying SQL Databases	285

IV Program Design	305
16 Message-based Parallelism with Actors	307
17 Multi-Process Applications	327
18 Building a Real-time File Synchronizer	345
19 Parsing Structured Text	363
20 Implementing a Programming Language	385

Conclusion

409

Part I Introduction to Scala

1 Hands-on Scala	15
1.1 Why Scala?	16
1.2 Why This Book?	17
1.3 How This Book Is Organized	18
1.4 Code Snippet and Examples	20
1.5 Online Materials	22

2 Setting Up	25
2.1 Windows Setup (Optional)	26
2.2 Installing Java	26
2.3 Installing Ammonite	27
2.4 Installing Mill	31
2.5 IDE Support	33

3 Basic Scala	39
3.1 Values	40
3.2 Loops, Conditionals, Comprehensions	47
3.3 Methods and Functions	51
3.4 Classes and Traits	54

4 Scala Collections	59
4.1 Operations	60
4.2 Immutable Collections	66
4.3 Mutable Collections	72
4.4 Common Interfaces	76

5 Notable Scala Features	81
5.1 Case Classes and Sealed Traits	82
5.2 Pattern Matching	84
5.3 By-Name Parameters	90
5.4 Implicit Parameters	92
5.5 Typeclass Inference	95

Part II Local Development

6 Implementing Algorithms in Scala	107
6.1 Merge Sort	108
6.2 Prefix Tries	112
6.3 Breadth First Search	118
6.4 Shortest Paths	121

7 Files and Subprocesses	127
7.1 Paths	128
7.2 Filesystem Operations	130
7.3 Folder Syncing	134
7.4 Simple Subprocess Invocations	138
7.5 Interactive and Streaming Subprocesses	142

8 JSON and Binary Data Serialization	147
8.1 Manipulating JSON	148
8.2 JSON Serialization of Scala Data Types	151
8.3 Writing your own Generic Serialization Methods	155
8.4 Binary Serialization	158

9 Self-Contained Scala Scripts	163
9.1 Reading Files Off Disk	164
9.2 Rendering HTML with Scalatags	165
9.3 Rendering Markdown with Commonmark-Java	167
9.4 Links and Bootstrap	171
9.5 Optionally Deploying the Static Site	175

10 Static Build Pipelines	179
10.1 Mill Build Pipelines	180
10.2 Mill Modules	184
10.3 Revisiting our Static Site Script	188
10.4 Conversion to a Mill Build Pipeline	189
10.5 Extending our Static Site Pipeline	193

Part III Web Services

11 Scraping Websites	203
11.1 Scraping Wikipedia	204
11.2 MDN Web Documentation	208
11.3 Scraping MDN	210
11.4 Putting it Together	214

12 Working with HTTP APIs	219
12.1 The Task: Github Issue Migrator	220
12.2 Creating Issues and Comments	222
12.3 Fetching Issues and Comments	224
12.4 Migrating Issues and Comments	229

13 Fork-Join Parallelism with Futures	237
13.1 Parallel Computation using Futures	238
13.2 N-Ways Parallelism	241
13.3 Parallel Web Crawling	244
13.4 Asynchronous Futures	249
13.5 Asynchronous Web Crawling	253

14 Simple Web and API Servers	259
14.1 A Minimal Webserver	260
14.2 Serving HTML	264
14.3 Forms and Dynamic Data	266
14.4 Dynamic Page Updates via API Requests	273
14.5 Real-time Updates with Websockets	277

15 Querying SQL Databases	285
15.1 Setting up Quill and PostgreSQL	286
15.2 Mapping Tables to Case Classes	288
15.3 Querying and Updating Data	291
15.4 Transactions	296
15.5 A Database-Backed Chat Website	298

Part IV Program Design

16 Message-based Parallelism with Actors	307
16.1 Castor Actors	308
16.2 Actor-based Background Uploads	309
16.3 Concurrent Logging Pipelines	315
16.4 Debugging Actors	322

17 Multi-Process Applications	327
17.1 Two-Process Build Setup	328
17.2 Remote Procedure Calls	331
17.3 The Agent Process	333
17.4 The Sync Process	335
17.5 Pipelined Syncing	338

18 Building a Real-time File Synchronizer	345
18.1 Watching for Changes	346
18.2 Real-time Syncing with Actors	347
18.3 Testing the Syncer	354
18.4 Pipelined Real-time Syncing	356
18.5 Testing the Pipelined Syncer	359

19 Parsing Structured Text	363
19.1 Simple Parsers	364
19.2 Parsing Structured Values	369
19.3 Implementing a Calculator	373
19.4 Parser Debugging and Error Reporting	378

20 Implementing a Programming Language	385
20.1 Interpreting Jsonnet	386
20.2 Jsonnet Language Features	386
20.3 Parsing Jsonnet	388
20.4 Evaluating the Syntax Tree	397
20.5 Serializing to JSON	403

Hands-on Scala Programming

Author	Li Haoyi
Published	1 June 2020
Website	www.handsonscala.com
ISBN	978-981-14-5693-0

First Edition, published June 1 2020

No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by means electronic, mechanical, photocopying, or otherwise, without prior written permission of the Author.

ISBN 978-981-14-5693-0

Written and Published by Li Haoyi

Book Website: https://www.handsonscala.com/

Chapter Discussion: https://www.handsonscala.com/discuss

Live Chat: https://www.handsonscala.com/chat

Online materials: https://github.com/handsonscala/handsonscala

For inquiries on distribution, translations, or bulk sales, please contact the author directly at haoyi.sg@gmail.com.

The information in this book is distributed on an “As Is” basis, without warranty. While every precaution has been taken in the preparation of this work, the Author shall not have any liability to any person or entity with respect to any loss or damage caused or alleged to be caused directly or indirectly by the information contained in it.

Reviewers

Thanks to all the reviewers who helped review portions of this book and provide the feedback that helped refine this book and make it what it is today.

In alphabetical order:

Alex Allain, Alwyn Tan, Bryan Jadot, Chan Ying Hao, Choo Yang, Dean Wampler, Dimitar Simeonov, Eric Marion, Grace Tang, Guido Van Rossum, Jez Ng, Karan Malik, Liang Yuan Ruo, Mao Ting, Martin MacKerel, Martin Odersky, Michael Wu, Olafur Pall Geirsson, Ong Ming Yang, Pathikrit Bhowmick

Table of Contents

Foreword

I Introduction to Scala

II Local Development