#include <iostream>
#include <cmath>

namespace co{
  // Class for 3D coordinates 
  class Point{
  public:
    double x,y,z;
  };
  
  double distance(const Point &, const Point &);
}
int main()
{
  co::Point point1 = {0.0,0.0,0.0}, point2={1.0,2.0,1.0};
  // move point1 a bit
  point1.x = 1.0;  // public data member accessed directly
  std::cout<<"distance = "<< co::distance(point1, point2) <<"\n";
}
// Euclidian distance between two points 
double co::distance(const co::Point &c1, const co::Point &c2){
    return ( sqrt(pow(c1.x-c2.x,2) + pow(c1.y-c2.y,2) + pow(c1.z-c2.z,2)  ) );
}