Logical Negation

Sometimes we need to find the opposite of a condition - that is, when a condition doesn't apply. This is what the negation operator ! is for:

bool isLoggedIn = false;

// Negation using !
if (!isLoggedIn) {
    std::cout << "User is not logged in" << std::endl;
}

Negation reverses the value of an expression:

• !true is false
• !false is true

It's often used to simplify conditions. Instead of:

if (age < 18) {
    std::cout << "Not an adult" << std::endl;
}

We can write:

bool isAdult = (age >= 18);
if (!isAdult) {
    std::cout << "Not an adult" << std::endl;
}

We can also negate more complex expressions using parentheses:

bool hasLicense = true;
bool hasCar = false;

// Negation of a compound expression
if (!(hasLicense && hasCar)) {
    std::cout << "Cannot drive" << std::endl;
}