There is no need to include user classes headers (<CGAL/Point_2.h>, <CGAL/Segment_2.h>, and so on) one by one when <CGAL/user_classes.h> is included.
There is no need to include user classes headers (<CGAL/Point_2.h>, <CGAL/Segment_2.h>, and so on) one by one when <CGAL/user_classes.h> is included.