c++ equality operator overload 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

// money.h -- define the prototype
class Money
{
   public:
      Money & operator += (const Money &rhs);
}

// money.cpp -- define the implementation
Money& Money :: operator += (const Money &rhs)
{
   // Yadda Yadda
  
   return *this;
}

Example 3: c++ overload operator

#include <iostream>
using namespace std;

class Box {
   public:
      double getVolume(void) {
         return length * breadth * height;
      }
      void setLength( double len ) {
         length = len;
      }
      void setBreadth( double bre ) {
         breadth = bre;
      }
      void setHeight( double hei ) {
         height = hei;
      }
      
      // Overload + operator to add two Box objects.
      Box operator+(const Box& b) {
         Box box;
         box.length = this->length + b.length;
         box.breadth = this->breadth + b.breadth;
         box.height = this->height + b.height;
         return box;
      }
      
   private:
      double length;      // Length of a box
      double breadth;     // Breadth of a box
      double height;      // Height of a box
};

// Main function for the program
int main() {
   Box Box1;                // Declare Box1 of type Box
   Box Box2;                // Declare Box2 of type Box
   Box Box3;                // Declare Box3 of type Box
   double volume = 0.0;     // Store the volume of a box here
 
   // box 1 specification
   Box1.setLength(6.0); 
   Box1.setBreadth(7.0); 
   Box1.setHeight(5.0);
 
   // box 2 specification
   Box2.setLength(12.0); 
   Box2.setBreadth(13.0); 
   Box2.setHeight(10.0);
 
   // volume of box 1
   volume = Box1.getVolume();
   cout << "Volume of Box1 : " << volume <<endl;
 
   // volume of box 2
   volume = Box2.getVolume();
   cout << "Volume of Box2 : " << volume <<endl;

   // Add two object as follows:
   Box3 = Box1 + Box2;

   // volume of box 3
   volume = Box3.getVolume();
   cout << "Volume of Box3 : " << volume <<endl;

   return 0;
}

Example 4: equals operator c++ overlaod

MyClass& MyClass::operator=(const MyClass &rhs) {

    // Only do assignment if RHS is a different object from this.
    if (this != &rhs) {
      ... // Deallocate, allocate new space, copy values...
    }

    return *this;
  }

Example 5: 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