Relational, Equality, and Three-Way Comparison (Spaceship Operator <=>)0%

Relational, Equality, and Three-Way Comparison (Spaceship Operator <=>)

Beginner13 min read•Updated: 2026-10-22

🚀 Relational, Equality, and Three-Way Comparison (Spaceship Operator <=>)

Introduction

Comparisons are fundamental to conditional branching. C++ includes traditional boolean comparison operators and introduced the revolutionary Three-Way Comparison Operator <=> (the "Spaceship Operator") in C++20.

⚖️ Standard Relational Operators

All standard relational operators yield a boolean value (true or false):

== : Equal to
!= : Not equal to
< : Less than
<= : Less than or equal to
> : Greater than
>= : Greater than or equal to

1#include <iostream>
2 
3int main() {
4    int userScore = 85;
5    int passingScore = 50;
6 
7    std::cout << std::boolalpha; // Formats boolean output as 'true'/'false'
8    std::cout << "Has passed: " << (userScore >= passingScore) << "\n";
9    std::cout << "Perfect score: " << (userScore == 100) << "\n";
10    return 0;
11}

🛸 The Modern C++20 Spaceship Operator (`<=>`)

Prior to C++20, if you authored a custom struct or class, you had to manually implement six separate comparison operators (==, !=, <, <=, >, >=). With C++20's Three-Way Comparison (<=>), a single operator provides complete ordering:

1#include <iostream>
2#include <compare>
3 
4int main() {
5    int a = 10;
6    int b = 20;
7 
8    auto result = (a <=> b);
9 
10    if (result < 0) {
11        std::cout << "a is less than b\n";
12    } else if (result == 0) {
13        std::cout << "a is equal to b\n";
14    } else {
15        std::cout << "a is greater than b\n";
16    }
17 
18    return 0;
19}

Return Types of `<=>`:

std::strong_ordering: Values that are substitutable (e.g. integers: if a == b, f(a) == f(b)).
std::partial_ordering: Values with non-comparable states (e.g. floating-point NaN).

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Arithmetic, Assignment, and Compound Operators	Logical Operators and Short-Circuiting

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Logical Operators and Short-Circuiting

Relational, Equality, and Three-Way Comparison (Spaceship Operator <=>)

Beginner13 min read•Updated: 2026-10-22

Study Materials

🚀 Relational, Equality, and Three-Way Comparison (Spaceship Operator <=>)

Introduction

⚖️ Standard Relational Operators

All standard relational operators yield a boolean value (true or false):

== : Equal to
!= : Not equal to
< : Less than
<= : Less than or equal to
> : Greater than
>= : Greater than or equal to

1#include <iostream>
2 
3int main() {
4    int userScore = 85;
5    int passingScore = 50;
6 
7    std::cout << std::boolalpha; // Formats boolean output as 'true'/'false'
8    std::cout << "Has passed: " << (userScore >= passingScore) << "\n";
9    std::cout << "Perfect score: " << (userScore == 100) << "\n";
10    return 0;
11}

🛸 The Modern C++20 Spaceship Operator (`<=>`)

1#include <iostream>
2#include <compare>
3 
4int main() {
5    int a = 10;
6    int b = 20;
7 
8    auto result = (a <=> b);
9 
10    if (result < 0) {
11        std::cout << "a is less than b\n";
12    } else if (result == 0) {
13        std::cout << "a is equal to b\n";
14    } else {
15        std::cout << "a is greater than b\n";
16    }
17 
18    return 0;
19}

Return Types of `<=>`:

std::strong_ordering: Values that are substitutable (e.g. integers: if a == b, f(a) == f(b)).
std::partial_ordering: Values with non-comparable states (e.g. floating-point NaN).

Next Lesson

Logical Operators and Short-Circuiting

Continue learning with hands-on practice, examples, and exercises in the upcoming topic.

Related Lessons

Previous Lesson	Next Lesson
Arithmetic, Assignment, and Compound Operators	Logical Operators and Short-Circuiting

Practice Quiz

Test your understanding of this lesson with 1 questions. Each question has one correct answer.

Previous Next

🚀 Relational, Equality, and Three-Way Comparison (Spaceship Operator <=>)

Introduction

⚖️ Standard Relational Operators

🛸 The Modern C++20 Spaceship Operator (<=>)

Return Types of <=>:

Logical Operators and Short-Circuiting

Related Lessons

Practice Quiz

Loading Page Content...

🚀 Relational, Equality, and Three-Way Comparison (Spaceship Operator <=>)

Introduction

⚖️ Standard Relational Operators

🛸 The Modern C++20 Spaceship Operator (<=>)

Return Types of <=>:

Logical Operators and Short-Circuiting

Related Lessons

Practice Quiz

🛸 The Modern C++20 Spaceship Operator (`<=>`)

Return Types of `<=>`:

🛸 The Modern C++20 Spaceship Operator (`<=>`)

Return Types of `<=>`: