Use the Spaceship Operator <=> for Three-Way Comparisons

The three-way comparison operator (<=>), commonly called the spaceship operator because it looks like a flying saucer in profile, is new in C++20. You may wonder, what's wrong with the existing six comparison operators? Nothing at all, and we will continue using them. The purpose of the spaceship is to provide a unified comparison operator for objects.

The common two-way comparison operators return one of two states, true or false, according to the result of the comparison. For example: