Introduction to the C++20 spaceship operator

C++20 introduced the three-way comparison operator, also known as the “spaceship operator” due to its appearance: <=>. The purpose is to streamline the process of comparing objects.

The Basics

Below is a simple example that uses this new spaceship operator:

#include <compare>

int main() {
  int a = 1;
  int b = 2;
  
  auto result = a <=> b;
  
  if (result < 0) {
    std::cout << "a is less than b" << std::endl;
  } else if (result == 0) {
    std::cout << "a is equal to b" << std::endl;
  } else { //…