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Lisp

👶  Children (ELI5)

Welcome to the hypnotic world of Lisp, my little fellow explorers! Just like a mystical wizard using powerful spells, Lisp is a programming language that can help us create magic with computers! Are you ready to unveil the secrets of this mysterious language? Let's begin our enchanted journey together!

A Trip Down Memory Lane 💭

Once upon a time, in the days of dragons and castles, there was a brilliant computer scientist named John McCarthy. He created Lisp in 1958, and it has dazzled programmers ever since. Lisp is one of the oldest programming languages still used today, passed down through generations like ancient scrolls.

Remember Aladdin's magical lamp? Well, Lisp has its own magic too! It can manipulate symbols and lists like no other language. This unique power makes Lisp extremely powerful and versatile, just like a clever magician!

The Enchanting World of Syntax 🌌

In the land of Lisp, everything is wrapped up in mesmerizing parentheses, like a secret code. These parentheses are not just for show; they have an essential purpose. They help us create beautiful lists that are the building blocks of Lisp programs. Let me show you:

(+ 3 5)

This simple line of code mesmerizes us with its elegance. Like a whispering chant, it's telling the computer to add the numbers 3 and 5 together. The answer? 8! See how the parentheses surround the plus sign and the numbers? That's the magical touch of Lisp!

To experience more magic, let's try another spell:

(* (+ 2 3) (- 7 1))

Aha! Now we've combined addition and subtraction with a touch of multiplication! The answer to this enchanting code is 30. Can you see how the parentheses help us understand the order of operations? Parentheses are the secret sauce that gives Lisp its charm!

The Art of Spellmaking: Functions ğŸŽ¨

In Lisp, we can use our creativity to craft our own spells! We call these spells "functions." A function can have a name followed by magical inputs, called "arguments." The special incantation (defun) is used to create a function. Here's an example:

(defun double (x)
  (* x 2))

Behold, we've created a double spell! This spell will double any number we give it. Let's use our double spell on the number 5:

(double 5)

Our spell worked! The result is 10!

We can also create enchanted functions that have multiple arguments, like this:

(defun add-numbers (x y)
  (+ x y))

This lovely spell adds two numbers together. Let's try it with the numbers 7 and 9:

(add-numbers 7 9)

Our magic has triumphed again! The result is 16!

Mystical Creatures: Recursion 🐲

Lisp has a favorite mythical creature called "recursion." Recursion is when a magical function calls upon itself to solve a problem, like a dragon breathing fire to light a new torch! Let's see an example of this magical beast in action:

(defun factorial (n)
  (if (= n 0)
      1
      (* n (factorial (- n 1)))))

This spell calculates the "factorial" of a number, which means multiplying it by every number smaller than itself down to 1. It does this by calling itself recursively. Let's see what happens when we ask for the factorial of 5:

(factorial 5)

Our spell weaves its recursive magic and produces the answer 120! Isn't recursion amazing?

Mysterious Incantations: Conditionals 🌙

Lisp has a box of secret incantations called "conditionals" that help our spells adapt to different situations. The most magical of these is the if statement. It helps our spells choose between two different paths based on a condition. Let's see an example:

(defun is-even (n)
  (if (= (mod n 2) 0)
      "It's even! ✨"
      "It's odd! 🌙"))

This enigmatic spell checks if a number is even or odd. If it's even, our spell will return "It's even! " and if it's odd, we'll hear "It's odd! ". Let's try our spell with the number 4:

(is-even 4)

The magic unveils the truth: "It's even! "

💖 Embrace the Magic of Lisp 💖

There you have it, my little fellow explorers! You've glimpsed into the mystical and magical world of Lisp programming. Remember, the power of Lisp lies in its enchanting syntax, captivating functions, mythical recursion, and mysterious conditionals.

Now that you've stepped into the realm of Lisp, you have the power to create your own magical spells and incantations. So go ahead, let your imagination run wild and embrace the magic of Lisp!

Grok.foo 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.