#include <math.h>
#include <iostream.h>
class Coordinate {
public:
	Coordinate(); // default constructor
	Coordinate(int xValue, int yValue, int displayValue);
	Coordinate(int xValue, int yValue);
	void setX(int xValue);
	void setY(int yValue);
	void setDisplay(int dValue);
	int getX() const;
	int getY() const;
	int getDisplay() const;
	friend float distance(Coordinate p1, Coordinate p2);
	friend ostream & operator << (ostream & oStream, const Coordinate & aPoint);
	
private:
	
	int x;
	int y;
	int display;
};
istream & operator >> (istream & iStream, Coordinate & aPoint);

#include "Coordinate.h"
#include <math.h>
#include <iostream.h>

float distance(Coordinate p1, Coordinate p2)  {
	int deltaX = p1.x - p2.x;
	int deltaY = p1.y - p2.y;
	return sqrt(deltaX*deltaX + deltaY*deltaY); // sqrt in math.h
}
ostream & operator << (ostream & oStream, const Coordinate & aPoint) {
   oStream << aPoint.x << " " << aPoint.y << " " << aPoint.display;
   return oStream;
}
istream & operator >> (istream & iStream, Coordinate  & aPoint) {
	int x,y,display;
   iStream >> x >> y >> display;
   aPoint.setX(x);
   aPoint.setY(y);
   aPoint.setDisplay(display);
   return iStream;
}

• Why is ">>" not a friend?
• Could it be made into a friend function?
• Would there be an advantage to doing so?
• Rewrite "<<" so it is not a friend function
• Rewrite distance so it is not a friend
• what is wrong with the following program

#include "Coordinate.h"
void main() {
   Coordinate point1;
   cout << point1.x;
}

• change this program so it works correctly (can you think of two ways to so this?)
• Why does >> return a reference to an "istream"
• what does the modifier "const" after getX mean?
• Is the function "distance" allowed to modify the values of its arguments? of its parameters?
• Would this function still work correctly if it was changed to use the following prototype:
  friend float distance(const Coordinate & p1, const Coordinate & p2);
  why or why not? what other changes woudl be needed?
• change the prototypes so that the following statement would set X, Y and Display to 1
  setDisplay(setX(setY(1)));
•