[luatex] Accessing pgf nodes from inside Lua(La)Tex

[Keith J. Schultz]

Hi All,

I am writing a package with pgf/TikZ from making Nassi-Schneider diagramms.
I have the code working under XeLaTeX and wanted to refracture it to LuaTeX.
I have to admit that I am not very TeXian. 

My question is if I have the name of a pgf node how do I get at its coordinates 
from
within LuaTeX.

Or, is there a way to call pgf from directly inside LuaTeX.

What I am looking for is to have a LuaTeX call to get the coordinates.
The following code that I have is: 

        \pgfextracty{\YCoordinate}{\pgfpointanchor{\LastNode}{south}}

        where \LastNode is the Name of the pgf node and \YCoordinate is a 
dimension.

So my do I access pgf structures from in LuaTeX?

Any help or pointers would be appreciated.


It would help me, also, if someone could tell me how to access something I have 
defined
with \edef in LuaTeX

eg. 

in the TeX file 
\edef{\aValue}{tttt}

in a loaded .lua file

function get_my_value(NameValue)
        local a = <some in Lua to access the edef>(NameValue)

        return a
end

Thanx in advance

regards
        Keith.