C++ Operators

C++ operators perform calculations, comparisons and logic on values. Most are the same as in C, and C++20 adds the three-way comparison operator <=>.

Arithmetic and Assignment

#include <iostream>

int main() {
    int a = 20, b = 6;
    std::cout << a + b << ' ' << a - b << ' ' << a * b << '\n';
    std::cout << a / b << ' ' << a % b << '\n';      // integer division
    std::cout << static_cast<double>(a) / b << '\n';
    a += 4;
    std::cout << a << '\n';
}

Comparison and Logical Operators

Comparisons produce bool values. Use && (and), || (or) and ! (not) to combine them. C++ also accepts the words and, or and not.

#include <iostream>

int main() {
    int age = 16;
    bool withParent = true;
    std::cout << std::boolalpha;
    std::cout << (age >= 18) << '\n';
    std::cout << (age >= 18 || withParent) << '\n';
}

false
true

Increment and Decrement

++x increments then returns the new value; x++ returns the old value then increments.

#include <iostream>

int main() {
    int x = 5;
    int a = x++;
    int b = ++x;
    std::cout << a << ' ' << b << ' ' << x << '\n';
}

5 7 7

Operator Tips

Use static_cast<double>(x) instead of C-style casts.
Parentheses make precedence obvious.
= assigns and == compares; compiler warnings help catch mistakes.
The C++20 <=> operator compares two values in one step and lets classes get all comparison operators automatically.

Frequently asked questions

Why does 7 / 2 give 3 in C++?

Both operands are integers, so C++ uses integer division and discards the remainder. Use 7.0 / 2 or static_cast<double> to get 3.5.

What is the spaceship operator in C++?

The <=> operator, added in C++20, returns whether one value is less than, equal to or greater than another. Defaulting it in a class generates all comparison operators.

What is static_cast in C++?

static_cast is the safe, explicit way to convert between related types such as int and double. It is easier to search for and stricter than a C-style cast.