Since CGAL 4.3, Arr_polyline_traits_2 has the ability to reverse the direction of X_monotone_curves. Does this mean I can break up a Polyline into X_montone_curves to generate a General_Polygon_2?
In the book CGAL Arragements and their applications. I've read that you needed to use Segments, not Polylines. Is this still the case? Is the book is out of date?
While the book provides information that does not exist in the manual, it is already a bit out of date, at least with respect to polylines, and will get even more so when CGAL 4.7 comes out.
With CGAL 4.6 you can create a general polygon the boundary of which comprises x-monotone polylines. This is possible due to the flexibility you mention, that is, a polyline can be directed from left to right or vise versa
With CGAL 4.7, the next coming release, you will be able create a general polygon the boundary of which comprises x-monotone polycurve, which are piecewise curves that are not necessarily linear, such as conic arcs, circular arcs, Bezier curves, line segments, or even other polycurves.