Hi all,

I'm solving the "splitting a polygon with a linestring" problem, and I'm
trying to repurpose the geometry graph structure to give me the result. My
current approach is to:

1) node the intersection of the linestring and polygon boundary
2) iterate the resulting edges
3) mark the both the directed edges resulting from the linestring as in the
result
4) polygonize the graph

This has problems, though, since the machinery that exists doesn't like to
use DEs where both the forward and reverse DE on an edge are in the result.
So I modified the algorithm at (3) to copy the reverse DE into another DE,
mark the original Sym as not in the result, and add the copy to the graph.
This, however, gets canceled out when the DE is determined to have the same
points as the existing DE's Sym, and the DE copy is never added to the
graph's edge map.

So, before I plow forward, I thought I'd take a pause to see if someone
might have a bit more insight into this. Apparently, it's been a problem for
others, and perhaps there is some thinking on it I could benefit from. Does
generating two forward DE edges, with the internal area on the right, in
order to generate shells, make sense? Is the problem just that JTS doesn't
support having two DEs with the same coordinates and are mirrors?

thanks!
-rory
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