% $Id: ob,v 1.2 2004/09/19 21:47:11 karl Exp $
% Public domain.
vardef C.ob(expr n) =
 save p; picture p;
 p=nullpicture;
 addto p doublepath makepath pencircle shifted(.5,.5)
  withpen pencircle scaled.0889;
 p scaled(.375*fontsize n)
enddef;
