Difference Between First-Class and Higher-Order Functions

In most programming languages like Python, Java, or JavaScript, two important terms often come to use are First-Class Functions and Higher-Order Functions. These concepts are fundamental to understanding the flexibility and power of programming. Hence, in this tutorial, we will explore the differences between first-class functions and higher-order functions.

First-Class vs. Higher-Order Functions

Before we dive into the tutorial, make sure you have a basic understanding of functions in Python. If you need a refresher, check out some introductory materials on functions in Python.

First-Class Functions

What are First-Class Functions?

In Python, functions are considered first-class citizens. But what does that mean? Simply put, it means that functions in Python are treated as first-class objects, just like any other object such as integers, strings, or lists.

Characteristics

Here are the characteristics of first-class functions:

1. Assigning to a Variable: You can assign a function to a variable, just like you would with any other object.

def msg(txt):
  return f"Hello, {txt}!"

my_msg = msg
print(my_msg("First-Class Function!"))

In this example, my_msg now refers to the same function as msg.

2. Passing as an Argument: Functions can be passed as arguments to other functions.

def calc(func, num):
  return func(num, 2)

result = calc(pow, 5)
print(result)

Here, the pow function is passed as an argument to calc. It returns the square of the input number.

3. Returning from a Function: Functions can also be returned from other functions.

def get_msg():
  def msg(txt):
    return f"Hello, {txt}!"
  return msg

my_msg = get_msg()
print(my_msg("First-Class Function"))

The function get_msg returns another function, creating a closure.

Higher-Order Functions

What are Higher-Order Functions?

While first-class functions focus on the treatment of functions as objects, higher-order functions take things a step further. A higher-order function is a function that either takes one or more functions as arguments or returns a function as a result.

Characteristics

Let’s explore the characteristics of higher-order functions. We are demonstrating here with the help of examples of higher-order functions in Python.

1. Taking a Function as an Argument: A higher-order function can take another function as an argument.

def operate_on_list(nums, operation):
  return [operation(num, 2) for num in nums]

sqrd_nums = operate_on_list([1, 2, 3, 4], pow)
print(sqrd_nums)

The operate_on_list function takes a list of numbers and a function (pow in this case) to apply to each element.

2. Returning a Function: A higher-order function can also return a function as its result.

def get_multiplier(factor):
  def multiplier(number):
    return number * factor
  return multiplier

double = get_multiplier(2)
print(double(2))

The function get_multiplier returns another function (multiplier), creating a closure.

Key Differences

Now that we’ve explored both first-class functions and higher-order functions, let’s highlight the key differences between them.

Focus on Properties:

• First-Class Functions: Emphasizes the properties of functions as objects.
• Higher-Order Functions: Emphasizes functions that take or return other functions.

Purpose:

• First-Class Functions: treats functions as if they are data, allowing storage, passing as arguments, and returning as values in Python
• Higher-Order Functions: Deals with functions that either team up with other functions or give birth to new functions.

Usage:

• First-Class Functions: Commonly appears in scenarios where variables storing functions or functions appear as arguments. It is an exercise to discover the versatility of functions.
• Higher-Order Functions: Frequently used when dealing with operations on functions, providing a way to abstract behavior.

Table of Comparison

Here is a one-to-one comparison between the two types of functions.

This simplified version aims to provide a clear and concise understanding of the key differences between first-class functions and higher-order functions.

Putting it into Practice

Now, let’s illustrate these concepts with a practical example. Imagine you are building a simple calculator program.

def square(num):
    return num ** 2

def cube(num):
    return num ** 3

def operate_on_list(nums, operation):
    return [operation(num) for num in nums]

nums = [3, 7, 11, 17]

sqrd_nums = operate_on_list(nums, square)
cubed_nums = operate_on_list(nums, cube)

print("Original Numbers:", nums)
print("Squared Numbers:", sqrd_nums)
print("Cubed Numbers:", cubed_nums)

In this example, operate_on_list is a higher-order function that takes a list of numbers and an operation function. The operation function can be square or cube, showcasing the concept of passing functions as arguments.

Must Read:
1. Higher Order Functions in Python
2. What are Lambda Functions in Python?
3. How to Use Lambda Function in Python?
4. Python Sort Using Lambda With Examples
5. Python Sort List of Lists With Examples
6. Python Get Last Element in List
7. How Do You Filter a List in Python?

Quick Wrap

Understanding first-class functions and higher-order functions in Python is essential for writing clean, modular, and efficient code. First-class functions enable treating functions as objects, providing flexibility in their use. Higher-order functions, on the other hand, take this flexibility to the next level. They allow other functions to appear as arguments or returned as results.

By grasping these concepts, you are now in a better position to design robust solutions in Python or Java. Experiment with these ideas in your code, and you’ll discover the true power of functions in Python programming.

Lastly, we need your support to continue. If you like our tutorials, share this post on social media like Facebook/Twitter.

Happy Coding,
Team TechBeamers