%% 
%%  Ein Beispiel der DANTE-Edition
%%  
%%  2. Auflage
%% 
%%  Beispiel 15-02-36 auf Seite 730.
%% 
%%  Copyright (C) 2016 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.
%% 
%% 
%% ==== 
verbatimtex
%% 
\documentclass[]{article}
\usepackage[T1]{fontenc}
\begin{document}
etex
% --- start of displayed preamble in the book ---
input boxes;
% --- end of displayed preamble in the book ---
beginfig(1)
circleit.anfang(btex \texttt{Anfang} etex);
anfang.c = (0,0);  anfang.dx = anfang.dy;
circleit.ende(btex \textsc{Ende} etex);
ende.c = (2cm,0);  ende.dx = ende.dy;
drawboxed(anfang,ende);
drawarrow  anfang.c {dir 45}..ende.c {dir -45}
cutbefore bpath.anfang cutafter bpath.ende;
drawarrow  ende.c {dir -135}..anfang.c {dir 135}
cutbefore bpath.ende cutafter bpath.anfang;
endfig;
end;
\end{document}