text: #include <sys/types.h>
  #include <sys/stat.h>
  
  #include <gudhi/Simplex_tree.h>
  #include <gudhi/Euclidean_witness_complex.h>
  #include <gudhi/pick_n_random_points.h>
  #include <gudhi/choose_n_farthest_points.h>
  #include <gudhi/Points_off_io.h>
  
  #include <CGAL/Epick_d.h>
  
  #include <iostream>
  #include <fstream>
  #include <ctime>
  #include <string>
  #include <vector>
  
  using K = CGAL::Epick_d<CGAL::Dynamic_dimension_tag>;
  using Point_d = K::Point_d;
  using Witness_complex = Gudhi::witness_complex::Euclidean_witness_complex<K>;
  using Point_vector = std::vector< Point_d >;
  
  int main(int argc, char * const argv[]) {
    if (argc != 5) {
      std::cerr << "Usage: " << argv[0]
          << " path_to_point_file number_of_landmarks max_squared_alpha limit_dimension\n";
      return 0;
    }
  
    std::string file_name = argv[1];
    int nbL = atoi(argv[2]), lim_dim = atoi(argv[4]);
    double alpha2 = atof(argv[3]);
    clock_t start, end;
    Gudhi::Simplex_tree<> simplex_tree;
  
    // Read the point file
    Point_vector point_vector, landmarks;
    Gudhi::Points_off_reader<Point_d> off_reader(file_name);
    if (!off_reader.is_valid()) {
        std::cerr << "Witness complex - Unable to read file " << file_name << "\n";
        exit(-1);  // ----- >>
      }
    point_vector = Point_vector(off_reader.get_point_cloud());
  
    std::cout << "Successfully read " << point_vector.size() << " points.\n";
    std::cout << "Ambient dimension is " << point_vector[0].dimension() << ".\n";
  
    // Choose landmarks (decomment one of the following two lines)
    // Gudhi::subsampling::pick_n_random_points(point_vector, nbL, std::back_inserter(landmarks));
    Gudhi::subsampling::choose_n_farthest_points(K(), point_vector, nbL, Gudhi::subsampling::random_starting_point, std::back_inserter(landmarks));
  
    // Compute witness complex
    start = clock();
    Witness_complex witness_complex(landmarks,
                                    point_vector);
  
    witness_complex.create_complex(simplex_tree, alpha2, lim_dim);
    end = clock();
    std::cout << "Witness complex took "
        << static_cast<double>(end - start) / CLOCKS_PER_SEC << " s. \n";
    std::cout << "Number of simplices is: " << simplex_tree.num_simplices() << "\n";
  }
  