[pstricks] How can I get the x and y coordinates of a node?

[Henrik Bengtsson]

Dear PSTricks coders, is it possible to get the x and y coordinates
of a node? I would like to get this to be able to calculate new
coordinates that are relative to a certain node coordinates.
 
For example, I would like to calculate the midpoint between two nodes A
and B:
 
\usepackage{pst-all} \usepackage{calc}
 
\newlength{\newx} \newlength{\newy} \psset{xunit=10mm,yunit=10mm}
\begin{pspicture}(0,0)(5,5)
  \rput(2,4){\circlenode{A}{A}}
  \rput(4,4){\circlenode{B}{B}}
  \ncline{A}{B}
 
  \setlength{\newx}{(\getxcoord{A} + \getxcoord{B}) / 2}
  \setlength{\newy}{(\getycoord{A} + \getycoord{B}) / 2}
 
  % Midpoint between A and B
  \pnode(\newx,\newy){AB}
 
  % Line to a node 2 yunits below the midpoint
  \psaddtolength{\newy}{-2}
  \rput(\newx,\newy){\circlenode{C}{C}}})
  \ncline{AB}{C} \end{pspicture}
 
Is there a "\getxcoord" and a "\getycoord" or something similar?

FYI: My knowledge of "low-level" TeX is very ad hoc.


Thanks
 
Henrik Bengtsson
Lund University, Sweden