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Scala Functional Programming Patterns

Scala Functional Programming Patterns

By : S. Khot
3.5 (2)
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Scala Functional Programming Patterns

Scala Functional Programming Patterns

3.5 (2)
By: S. Khot

Overview of this book

Scala is used to construct elegant class hierarchies for maximum code reuse and extensibility and to implement their behavior using higher-order functions. Its functional programming (FP) features are a boon to help you design “easy to reason about” systems to control the growing software complexities. Knowing how and where to apply the many Scala techniques is challenging. Looking at Scala best practices in the context of what you already know helps you grasp these concepts quickly, and helps you see where and why to use them. This book begins with the rationale behind patterns to help you understand where and why each pattern is applied. You will discover what tail recursion brings to your table and will get an understanding of how to create solutions without mutations. We then explain the concept of memorization and infinite sequences for on-demand computation. Further, the book takes you through Scala’s stackable traits and dependency injection, a popular technique to produce loosely-coupled software systems. You will also explore how to currying favors to your code and how to simplify it by de-construction via pattern matching. We also show you how to do pipeline transformations using higher order functions such as the pipes and filters pattern. Then we guide you through the increasing importance of concurrent programming and the pitfalls of traditional code concurrency. Lastly, the book takes a paradigm shift to show you the different techniques that functional programming brings to your plate. This book is an invaluable source to help you understand and perform functional programming and solve common programming problems using Scala’s programming patterns.
Table of Contents (13 chapters)
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12
Index

Abstractions

What do we mean by abstractions? Why are they important? To understand this, we will compare two approaches. First, the "go to the wall and pull at one of the wooden panels fitted into the rectangular hole" approach versus the "open the door, please" approach.

A door is an abstraction. We really don't care whether it is made of wood or some other material, or what type of a lock it has, or any other details. The details are important, but not always. If we worry about the details always, we would quickly get bogged down, and all the communication would effectively come to a halt.

A table is an abstraction, so is a chair, and so is a house. I hope you get the drift. We want to be selectively ignorant of the details at times, and selective ignorance is abstraction.

Now, you may ask why does it matter to us programmers? The reason is that it gets things done in a compact manner.

For example, let's look at the following Scala code, which is used to count the frequency of characters in a string:

scala> "hello world".toList.filter(_.isLetter).groupBy(x => x).map { y =>
     |   y._1 -> y._2.size
     | }
res1: scala.collection.immutable.Map[Char,Int] = Map(e -> 1, l -> 3, h -> 1, r -> 1, w -> 1, o -> 2, d -> 1)

Isn't it compact?

On the Urban Dictionary website, http://www.urbandictionary.com/define.php?term=cutie, the term "cutie" is defined as compact beauty—the kind you just want to put in your pocket and keep beside you forever.

I was bowled over when I first saw it all. It is concise, short, packs a punch, and is elegant. The Type Less Do More philosophy. Gets a lot done with less...

Note

To run the code snippet, fire up the Scala REPL. This looks a lot like a command console, a prompt waiting for you to key in Scala code. In a command terminal, typing just Scala fires up the REPL:

~> scala

It will give the following output:

Welcome to Scala version 2.11.7 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_25).

You can type in expressions to have them evaluated and type help for more information. Let's try the following simple one line commands:

scala> 1 + 1
res2: Int = 2
scala> "hello".length
res4: Int = 5

For me, Scala brought the thrill back to programming... You can do a great deal by writing a few lines of code—less is more...

Scala gives you many tools, so the code is abstract and reusable...

CONTINUE READING
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