public PlaLineInt translate_by(PlaVectorInt p_vector){
  if (p_vector.equals(PlaVectorInt.ZERO))   return this;
  PlaPointInt new_a=point_a.translate_by(p_vector);
  PlaPointInt new_b=point_b.translate_by(p_vector);
  return new PlaLineInt(new_a,new_b);
}

public PlaLineInt translate_by ( PlaVectorInt p_vector ) { if ( p_vector . equals ( PlaVectorInt . ZERO ) ) return this ; PlaPointInt new_a = point_a . translate_by ( p_vector ) ; PlaPointInt new_b = point_b . translate_by ( p_vector ) ; return new PlaLineInt ( new_a , new_b ) ; }
translates the line by p_vector
