Functional Programming Simplified: (Scala Edition)

About this book

If youve had trouble trying to learn Functional Programming (FP) youre not alone. In this best-selling highly-rated book Alvin Alexander author of the Scala Cookbook for OReilly the Scala Book for the official Scala website and former teacher of Java and Object-Oriented Programming (OOP) classes writes about his own problems in trying to understand FP how he finally conquered it and how he teaches others. In this classic book one of the highest-selling FP books of all time he teaches FP in a simple style without worrying about abstract concepts like functors monads and category theory. Instead he explains FP through a series of small pragmatic lessons and examples. The Motivation Behind Functional Programming For instance the first thing he learned is that experienced FP developers (FPers) are driven by two goals: to use only immutable values and write only pure functions. But then later he learned the REAL truth: FPers have these goals because their true desire or mental model is that they want all of their code to look and work just like algebra. While that sounds simple it turns out that these goals require them to use some advanced Scala features which they often use all at the same time. As a result their code can look completely foreign to novice FP developers. As Mr. Alexander writes When you first see their code its easy to ask Why would you write code like this? But then Mr. Alexander answers that Why? question by explaining the benefits of writing pure functional code. Five Rules for Functional Programming Once you understand those benefits your motivation for learning FP he shares five rules for programming in the book: All fields must be immutable (val fields). All functions must be pure functions. Null values are not allowed. Whenever you use an if you must also use an else. You wont create OOP classes that encapsulate data and behavior; instead youll design data structures using Scala case classes and write pure functions that operate on those data structures. In the book youll see how those five simple rules naturally lead you to write pure functional code that reads like algebra. He also shares one more Golden Rule for learning: Always ask Why? Lessons Lessons in the book include: How and why to write only pure functions Why pure function signatures are much more important than OOP method signatures Why recursion is a natural tool for functional programming and how to write recursive algorithms Because the Scala for expression is so important to FP dozens of pages explain the details of how it works In the end youll see that monads arent that difficult because theyre a natural extension of the Five Rules The book finishes with lessons on FP data modeling and two main approaches for organizing your pure functions As Mr. Alexander writes In this book I take the time to explain all of the concepts that are used to write FP code in Scala. As I learned from my own experience once you understand the Five Rules and the small concepts you can understand Scala/FP. Bonus: More Free Content Online Please note that because of the limits on how large a printed book can be the paperback version does not include all of the chapters that are in the Kindle eBook. The following lessons are not in the paperback version: Grandmas Cookies (a story about pure functions) The ScalaCheck lessons The Type Classes lessons The appendices Because those lessons didnt fit in the print version they have been made freely available online.