% (c) 2004 Andrzej Wasowski, IT Univeristy
%
% A fractal star drawn recursively, very much like in:
% M. Weiss.  Data Structures & Problem Solving Using Java.
% Addison-Wesley 1998, p. 188
%
% The program is written in an obscure language of METAPOST (a
% language for programming vector graphics for Latex documents, very
% similar in principle to METAFONT, which is the language used by TeX
% to describe fonts).
%
% To see the result call METAPOST:
%
%     mpost star.mp
%
% this will produce a file named "star.0" which is a viewable
% postscript. Either print it, or view in gv:
%
%     gv star.0
%
% This postscript can be directly included into a TeX document.
%
% METAPOST (mpost, sometimes called mp) is usually available on
% machines with LaTeX installations, in particular on ssh.itu.dk


% left, right should be given in centimeters (or any other measure)
% 
def drawFractal( expr xCenter, yCenter, boundingDim ) =
  begingroup
    save side, left, top, right, bottom;
    numeric side, left, top, right, bottom;
    side := boundingDim / 2;
    if side < .5mm:  % change values to achieve finer granularity
    else:

      % compute corners
      left  := xCenter - side / 2;
      top   := yCenter - side / 2;
      right := xCenter + side / 2;
      bottom:= yCenter + side / 2;

      % recursively draw four quadrants

      drawFractal (left,  top,    boundingDim / 2);
      drawFractal (left,  bottom, boundingDim / 2);
      drawFractal (right, top,    boundingDim / 2);
      drawFractal (right, bottom, boundingDim / 2);

      % draw Central square, overlapping quadrants

      fill (left,top)--(right,top)--(right,bottom)--(left,bottom)--cycle withcolor black;
    fi
  endgroup;
enddef;


beginfig(0)
  drawFractal(11cm,18cm,10cm);
endfig;
end