Book Image

Scala Functional Programming Patterns

By : Atul S. Khot
Book Image

Scala Functional Programming Patterns

By: Atul 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 (19 chapters)
Scala Functional Programming Patterns
Credits
About the Author
Aknowledgement
About the Reviewers
www.PacktPub.com
Preface
Index

Functional error handling


Handling errors is one tricky aspect of writing code. Error handling is the essential devil we simply can't do without.

The procedural world relies on returning error codes from functions, suffering from the same problem because of null checks. We could possibly miss checking. Also, the actual business logic gets lost in the tangled error handling code.

A case in point is file handling. Opening files and reading the contents, for example, could result in exceptions. As another example, the file may not exist (perhaps there is a typo in the filename), or it may not have requisite permissions.

Throwing an exception is a much better idea. The calling code cannot ignore it, at the very least it has to catch the exception.

You can, off course, use Java style try/catch blocks in Scala. As the try/catch block is an expression, you can assign its value to a variable:

scala> case class HandsUp(msg: String) extends Exception(msg)
defined class HandsUp

scala> def warnThem...