% Copyright 2007 TeX Users Group.
% You may freely use, modify and/or distribute this file.
% Stuff to create the dragon curve using LaTeX circle font

\nopagenumbers

\def\topglue{\nointerlineskip\vglue-\topskip\vglue} % for top of page

% \font\qc=lcircle1	% narrow line font
\font\qc=lcirclew 	% wide line font

% Can use following character codes for different size circles:
% 0-3, 4-7, 8-11, 12-15, 16-19, 20-23, 24-27, 28-31, 32-35, 36-39
% (except ATM 2.0 has a problem displaying character code 0).

\catcode`\ =9 \endlinechar=-1 % ignore all spaces (temporarily)
\newcount\dir \newdimen\y \newdimen\w
\newif\ifvisible \let\B=\visibletrue \let\W=\visiblefalse
\newbox\NE \newbox\NW \newbox\SE \newbox\SW \newbox\NS \newbox\EW
% \setbox\SW=\hbox{\qc a} \setbox\NW=\hbox{\qc b}
\setbox\SW=\hbox{\qc \char4} \setbox\NW=\hbox{\qc \char5}
% \setbox\NE=\hbox{\qc c} \setbox\SE=\hbox{\qc d}
\setbox\NE=\hbox{\qc \char6} \setbox\SE=\hbox{\qc \char7}
\w=\wd\SW \dimen0=\fontdimen8\qc
\setbox\EW=\hbox{\kern-\dp\SW \vrule height\dimen0 width\wd\SW} \wd\EW=\w
\setbox\NS=\hbox{\vrule height\ht\SW depth\dp\SW width\dimen0}  \wd\NS=\w
\def\L{\ifcase\dir \dy+\NW \or\dx-\SW \or\dy-\SE \or\dx+\NE\dd-4\fi \dd+1}
\def\S{\ifcase\dir \dx+\EW \or \dy+\EW \or \dx-\EW \or \dy-\NS \fi}
\def\R{\ifcase\dir \dy-\SW\dd+4 \or\dx+\SE \or\dy+\NE \or\dx-\NW\fi \dd-1}
\def\T{\ifcase\dir\kern-\w\dd+2\or\ey-\dd+2\or\kern\w\dd-2\or\ey+\dd-2\fi}
\edef\dd#1#2{\global\advance\dir#1#2\space}
\def\dx#1#2{\ifvisible\raise\y\copy#2 \if#1-\kern-2\w\fi\else\kern#1\w\fi}
\def\dy#1#2{\ifvisible\raise\y\copy#2 \kern-\w \fi \global\advance\y#1\w}
\def\ey#1{\global\advance\y#1\y}
\def\path#1{\hbox{\B \dir=0 \y=0pt #1}}
\catcode`\ =10 \endlinechar=`\^^M % resume normal spacing conventions

\newcount\n  % the current order in the \dragon and \nogard macros
\def\dragon{\ifnum\n>0{\advance\n-1 \dragon\L\nogard}\fi}
\def\nogard{\ifnum\n>0{\advance\n-1 \dragon\R\nogard}\fi}

% will need to adjust topglue and hskip if n is changed

\topglue 0.75in

\hskip 1.5in
% \path{\dir=3 \n=9 \dragon}
\path{\dir=3 \n=10 \dragon}

\end