what will happen, if we forget to return ostream referance in operator<<() function ?

[vimalankvk80]

what will happen, if we forget to return ostream referance ?

class A
{
 
   Private:
          int _a;
          int  _b;
 
  public:
 
    A( int i, int j) : a(i), b(j)
     {}
 
   friend ostream& operator<<(ostream &os, const A &obj)
   {
        os << obj._a << obj._b << endl;
        return os;        //  if i forget to return this referance.....
   }
};
 
int main()
{
 
A aobj = new A(5,10);
 
cout<< aobj;
 
return 0;
}
 

O/P = 5 10 //Answer

OR

can we use like this

friend void operator<<(ostream &os, const A &obj)
   {
        os << obj._a << obj._b << endl;
 
   }
 

will the ouput will be the same.....

[weaknessforcats]

You will return a copy of the ostream. That means your position pointers are lost. Anticipate screwed up displays.

The return of a reference is to avoid this copy so you can code:

cout << a << b << c;

[ProgrammerMatt]

Every action in C++ has a result and a side-effect. The result of cout << 5; is to return the ostream variable (cout). The side-effect is to put 5 into the ostream. Returning the ostream variable permits chaining multiple similar commands together. Without chaining, 3+4+5 is not possible; neither is cout << 3 << 4 << 5; If you return the ostream variable, the compiler takes several steps, first executing cout << 3; When cout is returned, it then has the code cout << 4 << 5; It continues this way until it outputs (or adds, or whatever) all operands. Without returning the ostream variable, you would have to type

cout << 3;
cout << 4;
cout << 5;

to achieve the same result.

[vimalankvk80]

#include <iostream>
 
using namespace std;
 
 
      class A
      {
         private:   
                int a;   
                int b;    
 
        public:
 
 
 
          A( int i, int j) : a(i), b(j)
 
           {
              cout << "intitialize a = " << a << endl;
              cout << "intitialize b = " << b << endl;
 
          }
 
 
 
         friend ostream& operator<<(ostream &os, const A &obj)
 
         {
 
              os << obj.a  << obj.b ;
 
              return os;        //  if i forget to return this referance.....
 
         }
 
      };
 
 
 
      int main()
 
      {
 
 
      A *aobj = new A(5,10);       
 
      cout<< aobj;
 
      cout<<endl;
 
 
 
      return 0;
 
      }
 

code as shown above...

i am getting :

my o/p : 004800f0

but expected is 510

why ? // i used vc6 IDE