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Polygon data type

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Hello all,

I know that this is the postgres forum and not the libpqxx forum (I've been there but no answer yet).

I want to retrieve the points of a polygon that are stored in the postgres db. The contents of the db are:

 polygonid |vertices
-----------+---------------------------------------------------------------------
         
2 |((1,0),(1.5,-1),(2,-1),(2,1),(1,1),(0,0),(0,2),(3,2),(3,-2),(1,-2))
         
4 | ((3,3),(4,4),(5,5))

The vertices column is of type Polygon.

I'm using libpqxx library for C++.

Suppose I want to retrieve and access the points in the vertices column, I would execute these statements in C++:

    result R = W.exec ("select * from polygon_tbl");
   
for (result::const_iterator r = R.begin();
         r
!= R.end();
         
++r)
   
{
       
int x = 0;
       cout
<< "Polygon ID: " << r[0].to(x) << endl;

       
//Suppose i would like to print the first point of every polygon,
       
//how would i access it?
       cout
<< "First vertex: " << r[1][0] << endl;    ???

       
//Or suppose i would like to print the first x coordinate of
       
//every polygon, how would i access it?
       cout
<< "First x coordinate: " << r[1][0][0] << endl; //???? (am just guessing here..)

   
}

Sorry I'm very new to libpqxx. I've pretty much understood how the libpqxx works but I'm stuck with the Polygon types. We actually just need a simple storage for our polygons in Postgres but I'm not sure how to access them using libpqxx. I know I can parse it as a string using r[1].c_str(), but is this the proper way to do it (parsing the text)? Or is there a container that I should use to store the vertices and access them using the container ? 

best regards,
mark

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