Overload the comparison operators: ==, and < code example

Example 1: c++ overloaded equality check operator

#include <iostream>
#include <string>
 
class Car
{
private:
    std::string m_make;
    std::string m_model;
 
public:
    Car(const std::string& make, const std::string& model)
        : m_make{ make }, m_model{ model }
    {
    }
 
    friend bool operator== (const Car &c1, const Car &c2);
    friend bool operator!= (const Car &c1, const Car &c2);
};
 
bool operator== (const Car &c1, const Car &c2)
{
    return (c1.m_make== c2.m_make &&
            c1.m_model== c2.m_model);
}
 
bool operator!= (const Car &c1, const Car &c2)
{
    return !(c1== c2);
}
 
int main()
{
    Car corolla{ "Toyota", "Corolla" };
    Car camry{ "Toyota", "Camry" };
 
    if (corolla == camry)
        std::cout << "a Corolla and Camry are the same.\n";
 
    if (corolla != camry)
        std::cout << "a Corolla and Camry are not the same.\n";
 
    return 0;
}

Example 2: c++ operator overloading not equal

lass Fred {
public:
  // ...
};
if 
  // Without operator overloading:
  Fred add(const Fred& x, const Fred& y);
  Fred mul(const Fred& x, const Fred& y);
  Fred f(const Fred& a, const Fred& b, const Fred& c)
  {
    return add(add(mul(a,b), mul(b,c)), mul(c,a));    // Yuk...
  }
else
  // With operator overloading:
  Fred operator+ (const Fred& x, const Fred& y);
  Fred operator* (const Fred& x, const Fred& y);
  Fred f(const Fred& a, const Fred& b, const Fred& c)
  {
    return a*b + b*c + c*a;
  }
#endif