Copying or reinterpret_cast

eigen.cpp

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>      
#include <Eigen/Dense>
#include <vector>
#include <algorithm>

typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef K::Point_3 Point_3;

int main()
{


  const Eigen::MatrixXd cubeV= (Eigen::MatrixXd(8,3)<<
  0.0,0.0,0.0,
  0.0,0.0,1.0,
  0.0,1.0,0.0,
  0.0,1.0,1.0,
  1.0,0.0,0.0,
  1.0,0.0,1.0,
  1.0,1.0,0.0,
  1.0,1.0,1.0).finished();

  std::vector<Point_3> points(8);
  for(int i = 0; i < 8; i++){
    points[i] = Point_3(cubeV(i,0), cubeV(i,1), cubeV(i,2));
    std::cout << points[i]<< std::endl;
  }

  return 0;

  {
  
  const Eigen::Matrix<double,8,3,Eigen::RowMajor> cubeV= (Eigen::Matrix<double,8,3,Eigen::RowMajor>(8,3)<<
                                2.0,0.0,0.0,
                                4.0,0.0,1.0,
                                8.0,1.0,0.0,
                                5.0,1.0,1.0,
                                6.0,0.0,0.0,
                                3.0,0.0,1.0,
                                0.0,1.0,0.0,
                                1.0,1.0,1.0).finished();

  Point_3* points = reinterpret_cast<Point_3*>(const_cast<double*>(cubeV.data()));
  for(int i = 0; i < 8; i++){
    std::cout << points[i] << std::endl;
  }

  std::sort(points,points+8, K::Less_xyz_3());
  std::cout << cubeV << std::endl;
  }
  
  return 0;
}