Arithmetic and Comparison Operators
Overload +, -, *, /, ==, < and friends following best practices.
Arithmetic and Comparison Operators is a free C++ Academy lesson on CoddyKit. This is lesson 1 of 4. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the C++ Academy learning path, and your progress syncs across the web and the CoddyKit app. The C++ Academy course includes 4 lessons in total.
Why Overload Operators?
Operator overloading lets your types behave like built-in types — v1 + v2 reads better than v1.add(v2). Use it for value types like vectors, complex numbers, money.
Defining operator+
You can overload + as a member or a free function. Free functions are more symmetric.
struct Vec2 {
double x, y;
Vec2 operator+(const Vec2& other) const {
return {x + other.x, y + other.y};
}
};Free Function Form
A free function gives both operands the same status — useful when conversion may apply to either side.
Vec2 operator+(const Vec2& a, const Vec2& b) {
return {a.x + b.x, a.y + b.y};
}Compound Assignment Operators
Implement += first; then build + on top of it. This is the canonical idiom.
Vec2& operator+=(const Vec2& other) {
x += other.x;
y += other.y;
return *this;
}
Vec2 operator+(Vec2 lhs, const Vec2& rhs) {
lhs += rhs;
return lhs;
}Unary Operators
Some operators are unary: -x, +x, !x, ~x, ++x, --x.
Vec2 operator-() const { return {-x, -y}; }Prefix vs Postfix Increment
Prefix takes no parameter; postfix takes a dummy int to disambiguate.
Counter& operator++(); // prefix
Counter operator++(int); // postfixComparison Operators
Comparison operators return bool. Free functions work best for consistency.
bool operator==(const Vec2& a, const Vec2& b) {
return a.x == b.x && a.y == b.y;
}
bool operator!=(const Vec2& a, const Vec2& b) { return !(a == b); }Less Than for Ordering
If your type needs to be sorted or used as a map key, define operator<. Other relational operators follow from it.
Symmetric Mixed-Type Operators
To support 3 + vec as well as vec + 3, define both — or use a free function that converts.
Avoid Surprises
Overloaded operators should behave intuitively. Do not redefine + to mean subtraction. Stick to the conventional algebra of the operator.
Operators You Cannot Overload
Some operators are off-limits:
?:— ternary.— member access (but->is overloadable)::— scope resolutionsizeof,alignof,typeid
Quick Check
What is the canonical implementation pattern for operator+ on a user type?
Recap
Operator overloading makes user types feel native. Implement compound assignment first, then plain arithmetic. Comparison operators are best as free functions. Stick to conventional semantics — surprise is a bug.
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Frequently Asked Questions
Is the “Arithmetic and Comparison Operators” lesson free?
Yes — any 3 lessons of the C++ Academy learning path, including “Arithmetic and Comparison Operators”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The C++ Academy course includes 4 lessons in total.
What will I learn in “Arithmetic and Comparison Operators”?
Overload +, -, *, /, ==, < and friends following best practices. You practise C++ Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start C++ Academy?
No prior experience is required. C++ Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 1 of 4.
How long does the “Arithmetic and Comparison Operators” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this C++ Academy lesson?
Yes. Every C++ Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Arithmetic and Comparison Operators
- Stream Insertion and Extraction Operators
- Subscript and Function Call Operators
- Three-Way Comparison Operator C++20