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Functional Programming

👶  Children (ELI5)

Gather around, my young friends, and let me tell you about an enchanting programming paradigm called Functional Programming! It's a fascinating way to write code that can help you create elegant, organized, and concise programs. In this magical realm, we treat functions like treasures and avoid mutating data. Are you ready to embark on this adventure with me?

🌈 Once Upon a Time: A Tale of Functions

In the land of Functional Programming, there are heroes known as functions. They're like sorcerers who can perform wonders but follow some rules:

  1. They keep their own environment clean by not changing anything outside themselves.
  2. They are pure and always give the same output when given the same input.
  3. They often use the power of other functions to perform their tasks.

Imagine functions as kind wizards who can only use their wands (inputs) to perform magic (calculations) and create enchanted objects (outputs) but cannot change anything else in the world.

👨‍🍳 Cooking up Some Functions!

Think of a kitchen where chefs make delicious meals using their ingredients (inputs), mixing them together (calculations), and serving them on plates (outputs). Imagine each chef having their own tools and ingredients, but never borrowing or changing anything from other chefs. That's how functional programming works!

Let's write a simple recipe using Python code to show how our functional programming chefs cook up masterpieces:

def add_ingredients(ingredient1, ingredient2):
  return ingredient1 + ingredient2

def sprinkle_magic(ingredient):
  return "sprinkled magic on " + ingredient

cake = add_ingredients("flour", "sugar")
enchanted_cake = sprinkle_magic(cake)


Here, we have two lovely functions (chefs), add_ingredients and sprinkle_magic. They perform their tasks and make an enchanted cake for us. Notice how they don't change anything outside their scope, just like the functional programming chefs!

🦉 The Wise Owl's Words: Immutable Data

In Functional Programming, we have a wise old owl named Immutable Data. This enchanting creature teaches us never to change data, but to create new data instead, just like our previous chefs did when creating the enchanted cake.

Let's see an example of wise owl's teaching:

def add_ingredient(ingredients_list, ingredient):
  return ingredients_list + [ingredient]

ingredients = ["flour", "sugar"]
new_ingredients = add_ingredient(ingredients, "butter")


As the wise owl advises, we make a new list called new_ingredients without changing the original list ingredients.

ğŸŽ­ Masters of Disguise: High-Order Functions

In the kingdom of Functional Programming, we have special agents called High-Order Functions. They are masters of disguise who can disguise themselves as other functions or even use other functions to perform their secret missions.

For instance, our special Python agents can undertake a mission called "mapping":

def double_spell(number):
  return number * 2

numbers = [1, 2, 3]
double_numbers = list(map(double_spell, numbers))


Here, the map function is our special agent who disguises as the double_spell function and doubles the numbers.

Another secret mission our agents often go on is called "filtering":

def is_even_spell(number):
  return number % 2 == 0

even_numbers = list(filter(is_even_spell, numbers))


This time, our filter agent disguises as the is_even_spell function and finds even numbers for us.

🧚‍♀️ Fairy Tales and Lambda Elves

In the enchanted forest of Functional Programming, we have magical creatures called Lambda Elves. They are tiny, mysterious beings that create functions on the spot without giving them a proper name.

When our programming wizards need a quick spell without crafting an entire function scroll, they summon Lambda Elves like this:

triple_numbers = list(map(lambda number: number * 3, numbers))


In this example, our wizard quickly summoned a Lambda Elf to triple the numbers using map.

🏰 The Kingdom of Functional Programming: Conclusion

So, my young adventurers, we've explored the magical world of Functional Programming together! We've learned about the heroes (functions), Immutable Data, High-Order Functions, and the mysterious Lambda Elves.

By adhering to these enchanting tales and rules from this kingdom, you can become a powerful sorcerer in the art of Functional Programming! Now, go forth and spread the magic of functional programming! is a collection of articles on a variety of technology and programming articles assembled by James Padolsey. Enjoy! And please share! And if you feel like you can donate here so I can create more free content for you.