Voronoi edge
data structure is implemented as the enhanced classical <a
 href="http://www.flipcode.com/archives/The_Half-Edge_Data_Structure.shtml">half-edge</a>
data structure. On the image below, the Voronoi edges are drawn as
directed linear (e.g. AE) or curved (e.g. DE) dashed lines of either
green (e.g. AE) or black (e.g DE) color. The green edges are considered
to be secondary, as they are generated by an input segment and its
endpoint (e.g. edge EA, made by segment MN and its endpoint M). All the
oth