Functional Programming For Dummies

John Paul Mueller

• Publisher: For Dummies
• Year: 2019
• ISBN:
  9781119527510
• Edition: 1
• Topic: Computer Science
• Subtopic: Programming
• Index: Computer Science

Yourguide to the functional programming paradigm

Functional programming mainly sees use in math computations, including those used in Artificial Intelligence and gaming. This programming paradigm makes algorithms used for math calculations easier to understand and provides a concise method of coding algorithms by people who aren't developers. Current books on the market have a significant learning curve because they're written for developers, by developers—until now.

Functional Programming for Dummies explores the differences between the pure (as represented by the Haskell language) and impure (as represented by the Python language) approaches to functional programming for readers just like you. The pure approach is best suited to researchers who have no desire to create production code but do need to test algorithms fully and demonstrate their usefulness to peers. The impure approach is best suited to production environments because it's possible to mix coding paradigms in a single application to produce a result more quickly. Functional Programming For Dummies uses this two-pronged approach to give you an all-in-one approach to a coding methodology that can otherwise be hard to grasp.

• Learn pure and impure when it comes to coding
• Dive into the processes that most functional programmers use to derive, analyze and prove the worth of algorithms
• Benefit from examples that are provided in both Python and Haskell
• Glean the expertise of an expert author who has written some of the market-leading programming books to date

If you're ready to massage data to understand how things work in new ways, you've come to the right place!

Part 1

Getting Started with Functional Programming

IN THIS PART …

Discover the functional programming paradigm.

Understand how functional programming differs.

Obtain and install Python.

Obtain and install Haskell.

Chapter 1

Introducing Functional Programming

IN THIS CHAPTER

Exploring functional programming

Programming in the functional way

Finding a language that suits your needs

Locating functional programming resources

This book isn’t about a specific programming language; it’s about a programming paradigm. A paradigm is a framework that expresses a particular set of assumptions, relies on particular ways of thinking through problems, and uses particular methodologies to solve those problems. Consequently, this programming book is different because it doesn’t tell you which language to use; instead, it focuses on the problems you need to solve. The first part of this chapter discusses how the functional programming paradigm accomplishes this task, and the second part points out how functional programming differs from other paradigms you may have used.

The math orientation of functional programming means that you might not create an application using it; you might instead solve straightforward math problems or devise what if scenarios to test. Because functional programming is unique in its approach to solving problems, you might wonder how it actually accomplishes its goals. The third section of this chapter provides a brief overview of how you use the functional programming paradigm to perform various kinds of tasks (including traditional development), and the fourth section tells how some languages follow a pure path to this goal and others follow an impure path. That’s not to say that those following the pure path are any more perfect than those following the impure path; they’re simply different.

Finally, this chapter also discusses a few online resources that you see mentioned in other areas of the book. The functional programming paradigm is popular for solving certain kinds of problems. These resources help you discover the specifics of how people are using functional programming and why they feel that it’s such an important method of working through problems. More important, you’ll discover that many of the people who rely on the functional programming paradigm aren’t actually developers. So, if you aren’t a developer, you may find that you’re already in good company by choosing this paradigm to meet your needs.

Defining Functional Programming

Functional programming has somewhat different goals and approaches than other paradigms use. Goals define what the functional programming paradigm is trying to do in forging the approaches used by languages that support it. However, the goals don’t specify a particular implementation; doing that is within the purview of the individual languages.

The main difference between the functional programming paradigm and other paradigms is that functional programs use math functions rather than statements to express ideas. This difference means that rather than write a precise set of steps to solve a problem, you use math functions, and you don’t worry about how the language performs the task. In some respects, this makes languages that support the functional programming paradigm similar to applications such as MATLAB. Of course, with MATLAB, you get a user interface, which reduces the learning curve. However, you pay for the convenience of the user interface with a loss of power and flexibility, which functional languages do offer. Using this approach to defining a problem relies on the declarative programming style, which you see used with other paradigms and languages, such as Structured Query Language (SQL) for database management.

In contrast to other paradigms, the functional programming paradigm doesn’t maintain state. The use of state enables you to track values between function calls. Other paradigms use state to produce variant results based on environment, such as determining the number of existing objects and doing something different when the number of objects is zero. As a result, calling a functional program function always produces the same result given a particular set of inputs, thereby making functional programs more predictable than those that support state.

Because functional programs don’t maintain state, the data they work with is also immutable, which means that you can’t change it. To change a variable’s value, you must create a new variable. Again, this makes functional programs more predictable than other approaches and could make functional programs easier to run on multiple processors. The following sections provide additional information on how the functional programming paradigm differs.

Understanding its goals

Imperative programming, the kind of programming that most developers have done until now, is akin to an assembly line, where data moves through a series of steps in a specific order to produce a particular result. The process is fixed and rigid, and the person implementing the process must build a new assembly line every time an application requires a new result. Object-oriented programming (OOP) simply modularizes and hides the steps, but the underlying paradigm is the same. Even with modularization, OOP often doesn’t allow rearrangement of the object code in unanticipated ways because of the underlying interdependencies of the code.

Functional programming gets rid of the interdependencies by replacing procedures with pure functions, which requires the use of immutable state. Consequently, the assembly line no longer exists; an application can manipulate data using the same methodologies used in pure math. The seeming restriction of immutable state provides the means to allow anyone who understands the math of a situation to also create an application to perform the math.

Using pure functions creates a flexible environment in which code order depends on the underlying math. That math models a real-world environment, and as our understanding of that environment changes and evolves, the math...