Logical Operators Part 1

Part of the Fundamentals section of Coddy's Swift journey — lesson 21 of 86.

Logical operators let you combine multiple Boolean values or conditions into a single result. The first logical operator we'll explore is the NOT operator (!), which flips a Boolean value to its opposite.

let isRaining = true
let isNotRaining = !isRaining  // false

print(!true)   // false
print(!false)  // true

The NOT operator is useful when you want to check for the opposite of a condition. If you have a variable tracking whether a user is logged in, you can easily check if they're logged out by negating it.

let isLoggedIn = false
let needsToLogin = !isLoggedIn  // true

You can also apply the NOT operator directly to comparison expressions by wrapping them in parentheses:

let age = 15
let isNotAdult = !(age >= 18)  // true

The NOT operator is simple but powerful — it gives you flexibility in how you express conditions in your code.

Challenge

Easy

Write a function isNotEligible that takes an age and returns whether the person is not eligible to vote.

A person is eligible to vote if they are 18 or older. Use the NOT operator to determine if they are not eligible.

Parameters:

age (Int): The person's age

Returns: true if the person is not eligible to vote (under 18), false if they are eligible (Bool)

Cheat sheet

The NOT operator (!) flips a Boolean value to its opposite:

let isRaining = true
let isNotRaining = !isRaining  // false

print(!true)   // false
print(!false)  // true

You can use the NOT operator to check for the opposite of a condition:

let isLoggedIn = false
let needsToLogin = !isLoggedIn  // true

The NOT operator can be applied directly to comparison expressions by wrapping them in parentheses:

let age = 15
let isNotAdult = !(age >= 18)  // true

Try it yourself

func isNotEligible(age: Int) -> Bool {
    // Write code here
}

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 Part 1

Arithmetic Operators Modulo Operator Compound Assignment Recap - Simple Math Comparison Operators

7Basic IO

Print Function String Interpolation ReadLine Input Type Conversion Recap - Till 120 Recap - True or False

10Functions

Declare A Function Parameters And Arguments Return Values Argument Labels Recap - Sigma Function Recap - Validation Function Default Values

13Iterating Over Sequences

Iterating Over Elements The Enumerated Method Iterating Over Strings P1 Iterating Over Strings P2

16Final Challenges

Flat Asterisk Pyramid Pattern Finder What To Buy

2Variables

Let vs Var Type Annotations Numbers String Boolean Naming Conventions Recap - Initialize Variables

5Operators Part 2

Logical Operators Part 1Logical Operators Part 2 Recap - Simple Logic Logical Operators Part 3 Ternary Operator

8Bill Split Calculator

Welcome Message Getting Input

Calculating Tip And Total

Splitting The Bill

Formatted Output

11FizzBuzz with a Twist

Game Overview The FizzBuzz Function

Looping The Numbers

Adding The Twist

14Arrays Advanced

Array Slicing Part 1 Array Slicing Part 2 Sequence Operators The Contains Method