Boost.Geometry polygon point assignment - c++

Question

i am trying to use boost geometry and having trouble assigning points to a polygon.
Lets assume i create an static vector of points
boost::geometry::model::d2::point_xy<double> >* a;
And then i create a polygon:
boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > polygon;
Assuming i have already defined the values of the points of a.
How can i assign the points from a to P?

Answer 1

The boost::geometry::assign_points() algorithm can be used to assign a range of points to a polygon.
If a is a range of points and P is a polygon, then one would use:
boost::geometry::assign_points(P, a);
Here is a complete example demonstrating the usage of assign_points:
#include <iostream>
#include <vector>
#include <boost/assign/std/vector.hpp>
#include <boost/geometry.hpp>
#include <boost/geometry/algorithms/area.hpp>
#include <boost/geometry/algorithms/assign.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/io/dsv/write.hpp>
int main()
{
using namespace boost::assign;
typedef boost::geometry::model::d2::point_xy<double> point_xy;
// Create points to represent a 5x5 closed polygon.
std::vector<point_xy> points;
points +=
point_xy(0,0),
point_xy(0,5),
point_xy(5,5),
point_xy(5,0),
point_xy(0,0)
;
// Create a polygon object and assign the points to it.
boost::geometry::model::polygon<point_xy> polygon;
boost::geometry::assign_points(polygon, points);
std::cout << "Polygon " << boost::geometry::dsv(polygon) <<
" has an area of " << boost::geometry::area(polygon) << std::endl;
}
Which produces the following output:
Polygon (((0, 0), (0, 5), (5, 5), (5, 0), (0, 0))) has an area of 25