// A namespace programmed in a similar way as struct Point.

#include <cmath>
#include <iostream>

using namespace std;

namespace PointNamespace {
  struct Point{
    double x, y;
  };

  double getx (Point);
  double gety (Point);
  void move(Point&, double, double);
  double distance_to(Point, Point);
};   

double PointNamespace::getx (Point p){
  return p.x;
}

double PointNamespace::gety (Point p){
  return p.y;
}

void PointNamespace::move(Point &p, double dx, double dy){
    p.x += dx; p.y += dy;
}

double PointNamespace::distance_to(Point p, Point other){
    return sqrt((p.x - other.x) * (p.x - other.x) + (p.y - other.y) * (p.y - other.y));
}

int main(){

  PointNamespace::Point
        p = {0,0}, 
        q = {3,4},
        r = {5,6};

  move(p,2,3);  // It is not necessary to qualify move with its namespace because
  move(q,4,5);  // move is looked up in the namaspace of its argument (stroustrup page 177).

  double d = distance_to(q,r);
  cout << d << endl;                                            // 3.60555

  cout << "Point p: " << getx(p) << ", " << gety(p) << endl;    // 2, 3
  cout << "Point q: " << getx(q) << ", " << gety(q) << endl;    // 7, 9
}