Implement operator<< overloading outside class

[kunigami]

Hi, I'm trying to overload the operator << for a class named "Point". The way I'm doing is this: I have three files, Point.cpp, Point.h and main.cpp.

Point.h

#include <iostream>

using namespace std;

class Point {

  double x, y;

 public: 
 
 Point(double x=0.0, double y=0.0): x(x), y(y) {};
    
  friend ostream& operator<< (ostream &o, Point p){
    o << "(" << p.x << " " << p.y << ")";
    return o;
  }
};

main.cpp

#include "Point.h"

int main (){

  Point p(1,2);
 
  cout << p << endl;
  
}

and Point.cpp is currently empty. Then I try to move the operator<< code to Point.cpp, like this:

Point.cpp

#include "Point.h"

friend ostream& Point::operator<< (ostream &o, Point p){
  o << "(" << p.x << " " << p.y << ")";
  return o;
}

And now I get the following error:

Point.cpp:3: error: ‘std::ostream& Point::operator<<(std::ostream&, Point)’ must take exactly one argument

Does anyone know how to handle this?

Thank you!

[jsmith]

Point::operator<< - the scope resolution operator :: says that operator<< is a member of the class, but friends are
not members. Remove the Point::.

[kunigami]

Thank you jsmith!

With your help I managed to solve the problem. I also had to remove the keyword 'friend' when defining the method outside the class. The way I did is like this:

Point.h

#include <iostream>

using namespace std;

class Point {

  double x, y;

 public: 
 
 Point(double x=0.0, double y=0.0): x(x), y(y) {};
    
  friend ostream& operator<< (ostream &o, Point p);
};

Point.cpp

#include "Point.h"

ostream& operator<< (ostream &o, Point p){
  o << "(" << p.x << " " << p.y << ")";
  return o;
}