%% 
%%  The LaTeX Graphics Companion, 2ed (first printing May 2007)
%% 
%%  Example 6-2-74 on page 365.
%% 
%%  Copyright (C) 2007 Michel Goossens, Frank Mittelbach, Denis Roegel, Sebastian Rahtz, Herbert Vo\ss 
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 

\documentclass{ttctexa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{99.83385pt}
\StartShownPreambleCommands
\usepackage{pstricks,pst-node} \SpecialCoor \raggedright
\StopShownPreambleCommands
\begin{document}
When defining nodes, such as \ \cnode{3pt}{A}, whose precise
coordinates are unknown (because they appear in the middle of a
paragraph or are the result of some internal calculation), we may
wish to know their values.  With \LaTeX{} those values cannot be
obtained directly.  There are, however, possibilities when we are
using PSTricks.
  \begin{pspicture}(1,1)
    \psgrid[subgriddiv=0,griddots=10,gridlabels=7pt]
    \Cnode(0.5,0.5){B}
    \makeatletter
    \psline[arrowscale=2,linestyle=dashed]{->}(B)(!%
      tx@NodeDict begin
        /N@B load GetCenter % center of node B
        /yB ED /xB ED
        /N@A load GetCenter % center of node A
        /yA ED /xA ED
        xA xB sub 0.6 mul xB add \pst@number\psxunit div
        yA yB sub 0.6 mul yB add \pst@number\psyunit div
      end)
    \makeatother
  \end{pspicture}
\end{document}