The 'not' Operator

Part of the Fundamentals section of Coddy's Lua journey — lesson 22 of 90.

<strong>not</strong> operator, which works differently from and and or. Instead of combining two conditions, the not operator inverts a single boolean value, flipping true to false and false to true.

Here's how the not operator works:

gameOver = false
gameRunning = not gameOver  -- gameRunning is true

playerAlive = true
playerDead = not playerAlive  -- playerDead is false

The not operator is particularly useful when you need to check the opposite of a condition. For example, instead of checking if a game is over, you might want to check if it's not over to continue playing.

isComplete = false
canContinue = not isComplete  -- canContinue is true

print(canContinue)  -- Output: true

Challenge

Easy

Check if a game is currently running by using the not operator to invert a game over status. Create a variable called gameOver and assign it the value false. Use the not operator to create a new variable called gameRunning that represents the opposite of the game over status. Print the result.

Cheat sheet

The not operator inverts a single boolean value, flipping true to false and false to true:

gameOver = false
gameRunning = not gameOver  -- gameRunning is true

playerAlive = true
playerDead = not playerAlive  -- playerDead is false

The not operator is useful for checking the opposite of a condition:

isComplete = false
canContinue = not isComplete  -- canContinue is true

Try it yourself

-- TODO: Write your code here

-- Print the result
print(gameRunning)

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Fundamentals

1Introduction

The Language Hello World!Comments

4Operators 2 Relational & Logic

Equality Operators Relational Operators The 'and' Operator The 'or' OperatorThe 'not' OperatorShort-Circuit Evaluation Truthy and Falsy Values Recap - Simple Logic

7Basic Conditional Logic

The if-then Statement The if-then-else Statement The elseif Statement Recap - Treasure Chest

10Tables Part 1: List-Style

What is a Table?Creating a Table Accessing Elements by Index Modifying Elements by Index The Length Operator '#'table.insert()table.remove()Recap - Manage Party Members

13Project: Simple Potion Shop

Project Setup Adding a Potion

Displaying the Inventory

Calculating Total Stock Value

Finding a Specific Potion

Selling a Potion

3Operators 1 Arithmetic & Conc

Arithmetic Operators Modulo Operator Exponentiation Operator String Concatenation Operator Precedence Recap - Simple Calculations

6Project: Character Stats Disp

Welcome Message Declare Character Stats

Display Basic Stats

Add a Boolean Flag

Final Summary

9Functions Basics

Declaring a Function Calling a Function Functions with Parameters Functions with Multiple Params The 'return' Statement Recap - Area Calculator

12Loops Basics

The while Loop The repeat-until Loop The Numeric for Loop for Loop with a Step The 'break' Statement Recap - Countdown

15Final Challenges

Recap - Player Turn Recap - Simple Database Recap - Sum of Even Numbers