Displaying result of addition of vectors

[Auroch]

Hello everybody!
I'm trying to display the result of addition of vectors. But Builder shows the error after compilation (line 29). What should I change for in my code in order to find the problem?
Thanks in advance.

#include <iostream.h>
#include <iomanip.h>
#include <conio.h>

class CVector2D {
  public:
	CVector2D(double x0 = 0, double y0 = 0)
	:x(x0), y(y0)
{
}

double x, y;

CVector2D const operator +(CVector2D const& vector2)const {
return CVector2D(x + vector2.x, y + vector2.y);
}

};

using namespace std;

int main()
{

CVector2D a(3.0, 5.8);
CVector2D b(7.3, 8.8);

CVector2D c = a + b + CVector2D(3, 9);
cout << "Sum is equal " << c << endl;

getch();
return 0;
}

Error (line 29):

[C++ Error] 5.cpp(27): E2094 'operator<<' not implemented in type 'ostream' for arguments of type 'CVector2D'

[dawtsf1187]

I think your problem is that std::cout doesn't recognize your CVector2D class. So you use the << operator for "Sum is equal", which it recognizes as a string, but then << c confuses it. If you added the x and y components of your vector in the class, you could do:

cout << "Sum is equal " << c.x << " " << c.y << endl;

[Auroch]

It's required to display the sum of vectors.
If I attend <stdio.h> and use printf("Sum is equal ", c);
The Output

Sum is equal 

without value.

[AbstractionAnon]

ostream doesn't know how to output a CVector2D object. You need to overload the << operator in your class.

  friend ostream & operator << (ostream & os, const CVector2D & cv)
  {  os << cv.x << ',' << cv.y;  // Or however you want to format it
      return os;
  }

[Auroch]

Hey AbstractionAnon, first off thank you for your insight, your explanation makes it more clear to me.
Thanks again!