Attractor::Attractor(Tuple &pos, Tuple &vel, double k) {
  this->x = pos.getX();
  this->y = pos.getY();
  this->vx = vel.getVX();
  this->vy = vel.getVY();
  this->k = k;
}
Attractor::Attractor(double x, double y, Tuple &vel, double k) {
  this->x = x;
  this->y = y;
  this->vx = vel.getVX();
  this->vy = vel.getVY();
  this->k = k;
}