Exploring Functional Programming Languages vs Object-Oriented Programming Languages | by Isreal | Jul, 2023



Note: This article is quite lengthy but it’s worth your time to deeply understand the differences between these concepts in programming. Enjoy reading and coding alongside.

The choice between functional programming languages and object-oriented programming languages is a topic of debate among software developers. Both paradigms offer distinct approaches to programming, emphasizing different principles and design philosophies. In this article, we will delve into the characteristics, benefits, and use cases of functional programming languages and object-oriented programming languages. We will also explore code snippets to demonstrate the key concepts and features of each paradigm.

  1. Understanding Functional Programming Languages.
  2. Exploring Object-Oriented Programming Languages.
  3. Code Snippets: Functional Programming Concepts.
  4. Code Snippets: Object-Oriented Programming Concepts.
  5. Choosing the Right Paradigm for the Task.
  6. Conclusion.
  7. Reference

Key Characteristics and Principles:

Immutability: In functional programming, immutability refers to the practice of creating data structures that cannot be modified after they are created. This prevents accidental changes to data and promotes a safer and more predictable programming style.

Here’s an example of this:

Pure Functions and Avoidance of Side Effects: Pure functions are functions that always produce the same output for the same input and do not cause any side effects, such as modifying external state or variables. They rely only on their inputs and return a new value without modifying the existing data.

Here’s a code snippet:

First-Class and Higher-Order Functions: In functional programming, functions are treated as first-class citizens, meaning they can be assigned to variables, passed as arguments to other functions, and returned as values from other functions. Higher-order functions are functions that can accept other functions as arguments or return functions as results.

Check out this code snippet:

// First-class function example
const greet = function(name)
console.log(`Hello, $name!`);

greet("Alice"); // Output: Hello, Alice!

// Higher-order function example
function multiplier(factor)
return function(number)
return number * factor;

const double = multiplier(2);
console.log(double(5)); // Output: 10

These characteristics and principles in functional programming promote code clarity, reusability, and make it easier to reason about the behavior of the code. By embracing immutability, pure functions, and higher-order functions, developers can write more reliable and maintainable code.

Benefits and Advantages:

Enhanced Modularity and Reusability: Functional programming promotes modular code design by emphasizing the separation of concerns and the use of pure functions. This allows developers to break down complex problems into smaller, reusable functions that can be composed together to solve larger tasks.

// Example of modular and reusable functions
function add(a, b)
return a + b;

function multiply(a, b)
return a * b;

function calculateTotal(price, quantity)
const subTotal = multiply(price, quantity);
const tax = multiply(subTotal, 0.1);
const total = add(subTotal, tax);
return total;

const totalPrice = calculateTotal(10, 5);
console.log(totalPrice); // Output: 55

Easy Parallelization and Concurrency: Functional programming promotes writing code that is less dependent on shared state, making it easier to parallelize and execute code concurrently. With functional programming, you can write code that is naturally more thread-safe and avoids common concurrency issues.

// Example of modular and reusable functions
function add(a, b)
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Functional Programming in PHP: Higher-order Functions

If you examine several frameworks and large-scale applications, you’ll certainly see a higher-order function at some point. Many languages support the idea of higher-order functions, including JavaScript, Java, .NET, Python and even PHP, to name a few.

But what is a higher-order function and why would we want to use one? What advantages does it give us and can we use it to simplify our code? In this article, we’ll talk about higher-order functions in PHP specifically, but will show how they’ve been used in other languages for comparison.

First-class Functions

Before we can get into what a higher-order function is, we must first understand that we have to have a language that can support a feature called first-class functions (aka first-order functions). This means that the language treats functions as first-class citizens. In other words, the language treats functions like it does variables. You can store a function in a variable, pass it to other functions as a variable, return them from functions like variables and even store them in data structures like arrays or object properties like you can with variables. Most modern languages these days have this feature by default. All you really need to know is that a function can be passed around and used much like variables are.

For our purposes, we’ll be focusing mostly on passing functions as arguments and returning functions as results, and briefly touching on the concept of non-local variables and closures. (You can read more about these concepts in sections 1.1, 1.4 and 1.3 of the Wikipedia article that was linked to in the previous paragraph.)

What Are Higher-order Functions?

There are two main characteristics that identify a higher-order function. A higher-order function can implement just one or both of the following ideas: a function that takes one or more functions as an input or returns a function as an output. In PHP there’s a keyword that’s a clear giveaway that a function is higher-order: the keyword callable. While this keyword doesn’t have to be present, the keyword makes it easy to identify them. If you see a function or method that has a callable parameter, it means that it takes a function as input. Another easy sign is if you see a function return a function using its return statement. The return statement might be just the name of the function, or could even be an anonymous/in-line function. Below are some examples of each type.

function echoHelloWorld() 
  echo "Hello World!";

function higherOrderFunction(callable $func) 


Here are some simple examples of higher-order functions that return a function:

function trimMessage1() 
  return 'trim';

function trimMessage2() 
    return function($text) 
        return trim($text);

$trim1 = trimMessage1(); 

echo $trim1('  hello world  ');

$trim2 = trimMessage1(); 

echo $trim2('  hello world  ');

As you can imagine,

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