%% 
%%  A DANTE-Edition example
%% 
%%  Example 16-02-8 on page 230.
%% 
%%  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{153.70511pt}
\setlength\parindent{0pt}

\usepackage{pstricks,pst-node}

\begin{document}
\psset{radius=0.3cm}\Cnode(.25,0){A}
\Cnode(2.5,0){B}\ncbar[angle=90]{->}{A}{B}
\ncbar[angle=-90,arm=.2cm]{->}{B}{A}\par\vspace{1cm}
\Cnode(.25,0){A}\Cnode(2.5,0){B}
\psset{linearc=.2cm}\ncdiag[angle=90]{->}{A}{B}%
\ncdiag[angle=-90,armA=.2cm,armB=.75cm]{->}{B}{A}
\end{document}