Operators overloading in C++

C++ allows you to specify more than one definition for a operators name in the same scope, which is called operators overloading in c++.

You can redefine or also overload most of the built-in operators available in C++. S that a programmer can use operators with user-defined types as well.

Overloaded operators are functions with special names the keyword operator followed by the symbol for the operator being defined. Like all other function, an overloaded operator has a return type and a parameter list.

Box operator+(const Box&);

declares the addition operator that can be used to add two Box objects and returns final Box object. Most overloaded operators may be defined as ordinary non-member functions or as class member functions. In case we define above function as non-member function of a class then we would have to pass two arguments for each operand as follows:

Box operator+(const Box&, const Box&);

This example is to show the concept of operator overloading using a member function. Here an object is passed as an argument whose properties will be accessed using this object, the object which will call this operator can be accessed using ‘this’ function operator as given below:

#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;
}

The code given is compiled and executed, it produces the following result as:

Volume of Box1 : 210
Volume of Box2 : 1560
Volume of Box3 : 5400

Overloadable/Non-overloadableOperators:

Following are the operators that can be overloaded:

+*/%^
&|~!,=
<><=>=++
<<>>==!=&&||
+=-=/=%=^=&=
|=*=<<=>>=[]()
->->*newnew []deletedelete []

Following are the operators that cannot be overloaded:

 

::.*.?:

 

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