rec {
   version="2.18";
   name="asymptote-2.18";
   hash="0i7jm12lzj983gvpa95a85wxb4v4ksk3cxb0cq359x2kka0b6g5m";
   url="http://downloads.sourceforge.net/project/asymptote/${version}/asymptote-${version}.src.tgz";
   advertisedUrl="http://downloads.sourceforge.net/project/asymptote/2.18/asymptote-2.18.src.tgz";
}