What is 3 way Comparator

a <=> b Compares the 2 variables(a,b) around it, and returns a value based on a and b
See example below

#include <compare>
#include <iostream>
    
int main()
{
    int a = 2, b = 1;
    auto res = a <=> b;      //Since a is greater than b. res>1
    /*              res
        a > b       >1
        a < b   <1
        a == b      0
    */
    if (res > 0)
        std::cout << "a greater than b";
    else
        std::cout << "a not greater than b";
}
# ./a.out
a greater than b