[GRASS5] dig_plus file - How does it work?

[John Gillette]

You are going to have to look in the code.  Start with 
<grass source>/src/include/vect/dig_structs.h
which gives the definitions of all the structures used to store topology
information.  

Then start looking through some vector programs to see how topology
is used.  I have enclosed a simple program I worked on with another user 
to give an area adjacency list.  It shows how to use the structures
to get area information.  I started this program
by looking at v.rm.dangles.

I never looked at the file structure because I didn't care.  I assume
that the contents of all the structures are written to the dig_plus file.

Note that this is 5.03 (or 5.3) information.  For 5.7 the vector
format has changed, although I would guess that a lot of information
is at least similar.

I hope that helps.  I wish it was documented as it is fundamental to
how vectors work.

John
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