Overload the output operator << to work with STL list iterator

Question

I have a Point2D class

Point2D

class Point2D
{
 public:

           int getX() const;
           int getY() const;

           void setX(int);
           void setY(int);

 protected:

             int x;
             int y;

};

I am trying to overload the output operator << to work with Point2D iterator p2d_list.begin() but i am unsure how to do it , this is my attempt

ostream& operator<< (ostream& afile, Point2D* p2)
{

               afile<<left
                    <<setw(1)
                    <<"["
                    <<left
                    <<setw(5)
                    <<p2->getX()
                    <<" ,"
                    <<left
                    <<setw(5)
                    <<p2->getY()
                    <<" ]    "
                    <<left
                    <<setw(6)
                    <<p2->getScalarValue()
                    <<endl;

                return afile;


}

In my main function

int main()
{

   list<Point2D> p2d_list;

   list<Point2D>::iterator p2 = p2d_list.begin();

        while ( p2 != p2d_list.end() )
        {
            cout<<p2; //error here
            p2++;

        }

}

I am getting the following Error

error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'std::_List_iterator<_Mylist>' (or there is no acceptable conversion)

How do i overload the output operator << so that it works with Point2D iterator **p2d_list.begin()

ForEveR · Accepted Answer · 2013-11-19 09:05:13Z

2

You are trying to output iterator, not Point2D. You should dereference iterator first. In your case it should be

cout << &(*p2);

, but I have no idea, why your operator << receives pointer, instead of ref/const-ref. It should be

ostream& operator<< (ostream& afile, const Point2D& p2)

and then output should be

cout << *p2;

answered Nov 19, 2013 at 9:05

ForEveR

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4 Comments

Computernerd Over a year ago

what changes must i make to the overload function?? and how should i cout ??

ForEveR Over a year ago

@Computernerd use ., instead of -> when address to fields of object. It's all.

Computernerd Over a year ago

it doesnt work i am getting the same error: Error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'Point2D' (or there is no acceptable conversion)

ForEveR Over a year ago

Show code. Is your operator << declaration changed as I advice?

Shubham · Accepted Answer · 2013-11-19 09:09:23Z

0

You need to overload the operator for list<Point2D>::iterator type instead of Point2D*

ostream& operator<< (ostream& afile, list<Point2D>::iterator &p2)
{

           afile<<left
                <<setw(1)
                <<"["
                <<left
                <<setw(5)
                <<(*p2)->getX()
                <<" ,"
                <<left
                <<setw(5)
                <<(*p2)->getY()
                <<" ]    "
                <<left
                <<setw(6)
                <<(*p2)->getScalarValue()
                <<endl;

            return afile;


}

answered Nov 19, 2013 at 9:09

Shubham

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