struct Point {
  double vec[3];


  Point() { vec[0]= vec[1] = vec[2] = 0; }
  Point (double x, double y, double z) { vec[0]=x; vec[1]=y; vec[2]=z;  }
 
  double x() const { return vec[ 0 ]; }
  double y() const { return vec[ 1 ]; }
  double z() const { return vec[ 2 ]; }

  double& x() { return vec[ 0 ]; }
  double& y() { return vec[ 1 ]; }
  double& z() { return vec[ 2 ]; }
  
  bool operator==(const Point& p) const 
  {
    return (x() == p.x()) && (y() == p.y()) && (z() == p.z())  ;
  }

  bool  operator!=(const Point& p) const { return ! (*this == p); }
}; //end of class

struct Construct_coord_iterator {
  typedef const double* result_type;
  const double* operator()(const Point& p) const 
  { return static_cast<const double*>(p.vec); }

  const double* operator()(const Point& p, int)  const
  { return static_cast<const double*>(p.vec+3); }
};
