What is Functional Programming?

You can find many types of programming, and one type will bring its own unique benefits and principles to the table.

So, if you’re curious about the functional programming concept, join us on this exciting journey of discovery. Let’s unravel the mysteries!

What Is Functional Programming?

Functional programming (FP) is an approach to software development. It focuses on the concept of creating and utilizing pure functions.

In FP, functions work as first-class citizens. It means you can assign them to variables, then pass them to other functions. Finally, they will return as values.

When working with functional programming, you’ll come across two terms: pure functions and impure functions.

Pure Functional Programming

In pure functional programming, functions are pure, meaning they do not have any side effects. They only depend on their input arguments to give a result.

Besides, pure functions consistently return the same result if you input the same arguments. The number of times you execute them doesn’t matter.

Impure Functional Programming

On the other hand, in impure functional programming, functions may come with side effects. Hence, you will encounter complexity and potential issues.

Furthermore, impure functions may not consistently produce the same result when you pass the same arguments.

Functional programming focuses on pure functions

Core Functional Programming Concepts

To make functional programming clearer, let’s explore the seven main concepts behind it.

Pure Functions

Pure functions are essential in functional programming because they serve as the fundamental building blocks. As aforementioned, they always offer the same output for the same input without any side effects.

However, the whole process doesn’t eliminate all side effects. Some of them, such as printing to the screen or calling APIs, are necessary for programs.

So, the goal is to reduce side effects so that the program’s behavior becomes easier to forecast and test.

First-Class Functions

One significant benefit of first-class functions is their unrestricted usage. You can treat them just like other variables.

Plus, the flexibility paves the way for various powerful programming techniques, such as closures, currying, and higher-order functions.

They build upon the foundation of first-class functions to enrich the capabilities of functional programming.

Higher-Order Functions

Higher-order functions are a powerful feature that enhances code modularity greatly. They can also accept other functions or return them.

By leveraging higher-order functions, you can achieve function polymorphism. This concept allows you to use a single code multiple times for different purposes.

Besides, high-order functions in functional programming help you make new ones (function composition). You may also create reusable functions that capture common behavior (function abstraction).

The polymorphism in programming changes a lot of things in your working progress.

You can use one code several times


Immutability promotes the use of data that you can’t change once assigning it.

Instead of adjusting the existing data, it focuses on creating new data structures with adjusted values. Thus, your data remains unchanged throughout the program, giving you a more predictable code.

By favoring immutability, functional programming reduces the chances of unintended side effects. That’s why it becomes easier to reason about the program’s behavior.


In contrast to using loops, functional programming typically uses recursive calls to solve problems. That’s where recursion functions come into play.

As the name implies, a recursive function breaks down complicated problems into smaller and more manageable ones. This iterative approach allows functional programming to handle repetitive tasks effectively.

So, the center of recursion is simplicity. It expresses the problem-solving process directly. Thus, you can use it to develop concise solutions for complex problems.

Function Composition

Function composition emphasizes the combination of small functions to construct more complex functionality. This method promotes reusability and modularity that help developers build sophisticated solutions.

In functional programming, you can connect functions by using the output of a function as the input for another.

Then, you will get a pipeline of transformation, where data flows through a system of functions. In this process, each function performs a specific task.

Referential Transparency

Referential transparency enables replacing an expression with its corresponding value without affecting the program’s result.

This approach simplifies the reasoning process in programs because each subprogram now becomes independent. It will benefit refactoring, where you can modify your code while keeping other parts unchanged.

Coding will be simpler

There are various functional programming languages. The most popular ones include the following:

  • Haskell: As a general-purpose programming language, Haskell focuses on pure functions. So, they won’t change variables or access external states.
  • Erlang: We primarily use Erland to develop scalable real-time systems in areas like computer telephony and eCommerce.
  • Clojure: This programming language blends dynamic and functional features. It offers a well-organized structure and interactive development.
  • Common Lisp: Common Lisp is a member of the Lisp programming language family. You may love it due to its powerful macro system.

Functional vs. Object-oriented Programming

Functional programming and object-oriented programming (OOP) have several key differences in their programming models as follows:

Programming Model

OOP follows an imperative model, where functions specify step-by-step instructions to solve a problem.

Meanwhile, functional programming adapts to a declarative model. It relies on the underlying concepts to execute the necessary steps for the desired outcome.

As you can see, OOP focuses on the process. On the other hand, functional programming emphasizes the result.


OOP employs mutable data. Hence, objects may change after creation. This concept is opposite to functional programming, where objects remain the same once generated.


Functional programming offers a fresh and powerful approach to coding. Focusing on pure functions and immutability brings clarity to your code.

So do you find functional programming interesting after reading this guide? If yes, start your adventure today and unlock a world of limitless possibilities. For any further information, do not hesitate to contact us.

Thank you for reading!