%% 
%%  A DANTE-Edition example
%% 
%% 
%%  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{201.70511pt}
\setlength\parindent{0pt}

\usepackage{pstricks-add}

\begin{document}
\psset{unit=2cm}
\begin{pspicture}(-2.5,-1.5)(2.5,2.5)
  \psaxes{->}(0,0)(-2.5,-1.5)(2.5,2.5)
  \psplot[linewidth=1.5pt,algebraic]{-2.5}{+2.5}{(2*x+4)/(2+x^2)}
  \psline[linestyle=dashed](-1.5,-1.5)(2.5,2.5)
  \def\function{ xVal dup add 4 add xVal dup mul 2 add div }%
  \pstVerb{ /xVal -1 def }% start value
  \multido{\nA=0+1}{10}{%
    \psline[linestyle=dotted](! xVal 0 )(! xVal xVal)
    \psline[linecolor=red](! xVal xVal )(! xVal \function )
    \psline[linecolor=red](! xVal \function )(! \function\space dup)
    \pstVerb{ /xVal \function\space def}
  }
\end{pspicture}
\end{document}