CGAL::compare_slopes

Comparison_result	compare_slopes ( Line_2<Kernel> l1, Line_2<Kernel> l2)
		compares the slopes of the lines l1 and l2
Comparison_result	compare_slopes ( Segment_2<Kernel> s1, Segment_2<Kernel> s2)
		compares the slopes of the segments s1 and s2