public double Sum(double y)
{
Accumulator a = new Accumulator(this);
a.Add(y);
return(a._s);
}
/**
* Add a point to the polygon or polyline.
* <p>
* @param lat the latitude of the point (degrees).
* @param lon the latitude of the point (degrees).
* <p>
* <i>lat</i> should be in the range [−90°, 90°].
**********************************************************************/
public void AddPoint(double lat, double lon)
{
lon = GeoMath.AngNormalize(lon);
if (_num == 0)
{
_lat0 = _lat1 = lat;
_lon0 = _lon1 = lon;
}
else
{
GeodesicData g = _earth.Inverse(_lat1, _lon1, lat, lon, _mask);
_perimetersum.Add(g.Distance);
if (!_polyline)
{
_areasum.Add(g.GeodesicScale12);
_crossings += Transit(_lon1, lon);
}
_lat1 = lat; _lon1 = lon;
}
++_num;
}
/**
* Return the results so far.
* <p>
* @param reverse if true then clockwise (instead of counter-clockwise)
* traversal counts as a positive area.
* @param sign if true then return a signed result for the area if
* the polygon is traversed in the "wrong" direction instead of returning
* the area for the rest of the earth.
* @return PolygonResult(<i>num</i>, <i>perimeter</i>, <i>area</i>) where
* <i>num</i> is the number of vertices, <i>perimeter</i> is the perimeter
* of the polygon or the length of the polyline (meters), and <i>area</i>
* is the area of the polygon (meters<sup>2</sup>) or Double.NaN of
* <i>polyline</i> is true in the constructor.
* <p>
* More points can be added to the polygon after this call.
**********************************************************************/
public PolygonResult Compute(bool reverse, bool sign)
{
if (_num < 2)
{
return(new PolygonResult(_num, 0, _polyline ? Double.NaN : 0));
}
if (_polyline)
{
return(new PolygonResult(_num, _perimetersum.Sum(), Double.NaN));
}
GeodesicData g = _earth.Inverse(_lat1, _lon1, _lat0, _lon0, _mask);
Accumulator tempsum = new Accumulator(_areasum);
tempsum.Add(g.GeodesicScale12);
int crossings = _crossings + Transit(_lon1, _lon0);
if ((crossings & 1) != 0)
{
tempsum.Add((tempsum.Sum() < 0 ? 1 : -1) * _area0 / 2);
}
// area is with the clockwise sense. If !reverse convert to
// counter-clockwise convention.
if (!reverse)
{
tempsum.Negate();
}
// If sign put area in (-area0/2, area0/2], else put area in [0, area0)
if (sign)
{
if (tempsum.Sum() > _area0 / 2)
{
tempsum.Add(-_area0);
}
else if (tempsum.Sum() <= -_area0 / 2)
{
tempsum.Add(+_area0);
}
}
else
{
if (tempsum.Sum() >= _area0)
{
tempsum.Add(-_area0);
}
else if (tempsum.Sum() < 0)
{
tempsum.Add(+_area0);
}
}
return
(new PolygonResult(_num, _perimetersum.Sum(g.Distance), 0 + tempsum.Sum()));
}