It is possible to interactively experiment the effect
of figure parameters. This requires:
1) MetaPost code written as "anglinerigorouscircle.mp".
2) xcmd package (kindly provided by Pedro Sebastião);
	  it may be downloaded from http://lince.cii.fc.ul.pt/
	  in Debian, Red Hat or tar.gz package formats.
3) Perl.
4) gv.
5) run command "xcmd/xmpost anglinerigorouscircle" or 
	       "xcmd/xmpost anymetapostwoextension".
