%% 
%%  A DANTE-Edition example
%% 
%%  Example 16-02-5 on page 229.
%% 
%%  Copyright (C) 2011 Herbert Voss
%% 
%%  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.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
\documentclass[]{article}
\pagestyle{empty}
\setlength\textwidth{129.70511pt}
\setlength\parindent{0pt}

\usepackage{pstricks,pst-node}

\begin{document}
\begin{pspicture}(2,2)\psgrid[subgriddiv=2]
 \cnode(0.25,1.75){0.25cm}{A}\cnode(1.75,0.25){0.25cm}{B}
 \ncline[nodesep=.25]{<->}{A}{B}
 \cnode(1.75,1.75){0.25cm}{C}\cnode(0.25,0.25){0.25cm}{D}
 \ncline[Ynodesep=.25]{<->}{C}{D}
\end{pspicture}
\end{document}