Cone_spanners_2/theta_io.cpp

#include <cstdlib>
#include <iostream>
#include <fstream>
#include <iterator>
#include <string>
#include <vector>
#include <CGAL/Exact_predicates_exact_constructions_kernel_with_root_of.h>
#include <CGAL/Construct_theta_graph_2.h>
#include <CGAL/gnuplot_output_2.h>
 
// select the kernel type
typedef CGAL::Exact_predicates_exact_constructions_kernel_with_root_of   Kernel;
typedef Kernel::Point_2                   Point_2;
typedef Kernel::Direction_2               Direction_2;
/* Note: due to a bug in the boost library, using a directed graph
 * will cause a compilation error with g++ and clang++ when using c++11 standard.
 * See https://lists.boost.org/Archives/boost/2016/05/229458.php.
 */
// define the graph type
typedef boost::adjacency_list<boost::listS,
                              boost::vecS,
                              boost::undirectedS,
                              Point_2
                             > Graph;
 
int main(int argc, char ** argv)
{
  unsigned int k=4; // By default, no. of cones==4
  std::string filename="data/n9.cin"; // file used by default
 
  if (argc > 1 &&
      (!strcmp(argv[1],"-h") || !strcmp(argv[1],"--help") || !strcmp(argv[1],"-?")))
  {
    std::cout << "Usage: " << argv[0] << " <no. of cones> <input filename> [<direction-x> <direction-y>]" << std::endl;
    return 1;
  }
 
  if (argc > 1)
  {
    k = atoi(argv[1]);
    if (k<2) {
      std::cout << "The number of cones should be larger than 1!" << std::endl;
      return 1;
    }
  }
 
  if (argc > 2)
  { filename=std::string(argv[2]); }
 
  // open the file containing the vertex list
  std::ifstream inf(filename);
  if (!inf) {
    std::cout << "Cannot open file " << filename << "!" << std::endl;
    return 1;
  }
 
  Direction_2 initial_direction;
  if (argc == 1 || argc == 3)
    initial_direction = Direction_2(1, 0);  // default initial_direction
  else if (argc == 5)
    initial_direction = Direction_2(atof(argv[3]), atof(argv[4]));
  else {
    std::cout << "Usage: " << argv[0] << " <no. of cones> <input filename> [<direction-x> <direction-y>]" << std::endl;
    return 1;
  }
 
  // iterators for reading the vertex list file
  std::istream_iterator<Point_2> input_begin( inf );
  std::istream_iterator<Point_2> input_end;
 
  // initialize the functor
  CGAL::Construct_theta_graph_2<Kernel, Graph> theta(k, initial_direction);
  // create an adjacency_list object
  Graph g;
  // construct the theta graph on the vertex list
  theta(input_begin, input_end, g);
 
  // obtain the number of vertices in the constructed graph
  boost::graph_traits<Graph>::vertices_size_type n = boost::num_vertices(g);
  // generate gnuplot files for plotting this graph
  std::string file_prefix = "t" + std::to_string(k) + "n" + std::to_string(n);
  CGAL::gnuplot_output_2(g, file_prefix);
 
  return 0;
}