/**
* Calculates the centers of two points and
* applies the function to the two points,
*
* @param Geometry $point_a The first point.
* @param Geometry $point_b The second point.
* @param closure $f Function to apply.
* @return float Result of application of $f.
*/
private static function apply($point_a, $point_b, $f)
{
$center_a = $point_a->centroid();
$center_b = $point_b->centroid();
$coor_a = new Coordinate($center_a->y(), $center_a->x());
$coor_b = new Coordinate($center_b->y(), $center_b->x());
return $f($coor_a, $coor_b);
}
