Coordinate computePoint(const LineSegment& seg, double dist)
 {
   double dx = seg.p1.x - seg.p0.x;
   double dy = seg.p1.y - seg.p0.y;
   double len = seg.getLength();
   Coordinate pt(dist * dx / len, dist * dy / len);
   pm.makePrecise(pt);
   return pt;
 }
   void preciseCoordinateTester(const PrecisionModel& pm,
                 double x1, double y1,
                 double x2, double y2)
   {
         Coordinate p(x1, y1);
 
         pm.makePrecise(p);
 
         Coordinate pPrecise(x2, y2);
         ensure(p.equals2D(pPrecise));
   }