在CGAL4.6中编译CGAL4.2中成功编译的代码错误

Question

我有以下代码被成功编译并使用CGAL4.2执行。

cgal_intersection.h

typedef struct {double x; double y;} coordinate; 

int cgal(); 

extern "C" int find_intersections_of_curves(
    coordinate *curve_1, long curve_1_size, 
    coordinate *curve_2, long curve_2_size, 
    coordinate *intersections, int max_num_of_intersections); 

cgal_intersection.cpp

#include <CGAL/Cartesian.h> 
#include <CGAL/Arr_segment_traits_2.h> 
#include <CGAL/Arr_polyline_traits_2.h> 
#include <CGAL/Sweep_line_2_algorithms.h> 
#include <vector> 
#include <list> 

#include "cgal_intersection.h" 

typedef CGAL::Cartesian<double>     Kernel; 
typedef CGAL::Arr_segment_traits_2<Kernel>    Segment_traits; 
typedef CGAL::Arr_polyline_traits_2<Segment_traits>  Traits; 
typedef Traits::Point_2         Point; 
typedef Traits::Curve_2         Polyline; 

extern "C" int find_intersections_of_curves(
    coordinate *curve_1, long curve_1_size, 
    coordinate *curve_2, long curve_2_size, 
    coordinate *intersections, int max_num_of_intersections) 
{ 

    std::vector<Point> points_1(curve_1_size); 
    for (long i_1 = 0; i_1 < curve_1_size; i_1++) 
     points_1[i_1] = Point(curve_1[i_1].x, curve_1[i_1].y); 
    Polyline polyline_1(points_1.begin(), points_1.end()); 

    std::vector<Point> points_2(curve_2_size); 
    for (long i_2 = 0; i_2 < curve_2_size; i_2++) 
     points_2[i_2] = Point(curve_2[i_2].x, curve_2[i_2].y); 
    Polyline polyline_2(points_2.begin(), points_2.end()); 

    Polyline polylines[] = {polyline_1, polyline_2}; 
    std::list<Point> intersection_points; 
    CGAL::compute_intersection_points(polylines, polylines + 2, 
             std::back_inserter(intersection_points)); 

    int num_of_intersections = intersection_points.size(); 
    Point intersection_point; 
    for (int j = 0; j < num_of_intersections; j++){ 
     if (j == max_num_of_intersections) 
      break; 
     intersection_point = intersection_points.front(); 
     intersections[j].x = intersection_point.x(); 
     intersections[j].y = intersection_point.y(); 
     intersection_points.pop_front(); 
    } 

    return num_of_intersections; 
} 

但使用CGAL4.6的时候，我得到类似下面的编译错误：

Scanning dependencies of target cgal_intersection 
[100%] Building CXX object CMakeFiles/cgal_intersection.dir/cgal_intersection.cpp.o 
In file included from /home/chan/mose/mose/cgal_intersection/cgal_intersection.cpp:5:0: 
/usr/include/CGAL/Sweep_line_2_algorithms.h: In instantiation of ‘OutputIterator CGAL::compute_intersection_points(CurveInputIterator, CurveInputIterator, OutputIterator, bool) [with CurveInputIterator = CGAL::polyline::Polyline_2<CGAL::Arr_segment_2<CGAL::Cartesian<double> >, CGAL::Point_2<CGAL::Cartesian<double> > >*; OutputIterator = std::back_insert_iterator<std::list<CGAL::Point_2<CGAL::Cartesian<double> > > >]’: 
/home/chan/mose/mose/cgal_intersection/cgal_intersection.cpp:36:78: required from here 
/usr/include/CGAL/Sweep_line_2_algorithms.h:134:48: error: no type named ‘Traits’ in ‘struct CGAL::Default_arr_traits<CGAL::polyline::Polyline_2<CGAL::Arr_segment_2<CGAL::Cartesian<double> >, CGAL::Point_2<CGAL::Cartesian<double> > > >’ 
    typename Default_arr_traits<Curve>::Traits traits; 
               ^
/usr/include/CGAL/Sweep_line_2_algorithms.h:134:48: error: no type named ‘Traits’ in ‘struct CGAL::Default_arr_traits<CGAL::polyline::Polyline_2<CGAL::Arr_segment_2<CGAL::Cartesian<double> >, CGAL::Point_2<CGAL::Cartesian<double> > > >’ 
make[2]: *** [CMakeFiles/cgal_intersection.dir/cgal_intersection.cpp.o] Error 1 
make[1]: *** [CMakeFiles/cgal_intersection.dir/all] Error 2 
make: *** [all] Error 2 

我看着头文件，但我不明白它为什么在CGAL4.2中有效，但在CGAL4.6中失败。我会很感激任何帮助。

Answer 1

我在两次修改后成功编译了代码。

1. 原来的Arr_polyline_traits_2的API从CGAL4.2至CGAL4.4显著改变。例如，使用CGAL4.6.1时，应使用Construct_curve_2构造多段线，如示例代码Arrangement_on_surface_2/polylines.cpp中所述。

2. compute_intersection_points有两种重载定义。在这里，应该明确指出正在使用哪个特征，即应该使用在以下描述的API：http://doc.cgal.org/latest/Sweep_line_2/group__PkgIntersectionOfCurves2.html#ga69bf75d5c190cf566c1f6eba93a20a29。

掺入上述修饰后，工程的代码是这样的：

// Computing intersection points among curves using the sweep line. 
#include <CGAL/Cartesian.h> 
#include <CGAL/Arr_segment_traits_2.h> 
#include <CGAL/Arr_polyline_traits_2.h> 
#include <CGAL/Sweep_line_2_algorithms.h> 
#include <vector> 
#include <list> 

#include "cgal_intersection.h" 

typedef CGAL::Cartesian<double>       Kernel; 
typedef CGAL::Arr_segment_traits_2<Kernel>    Segment_traits; 
typedef CGAL::Arr_polyline_traits_2<Segment_traits>  Polyline_traits; 
typedef Polyline_traits::Point_2      Point; 
typedef Polyline_traits::Curve_2      Polyline; 

extern "C" int find_intersections_of_curves(
    coordinate *curve_1, long curve_1_size, 
    coordinate *curve_2, long curve_2_size, 
    coordinate *intersections, int max_num_of_intersections) 
{ 
    Polyline_traits polyline_traits; 
    Polyline_traits::Construct_curve_2 construct_polyline = 
     polyline_traits.construct_curve_2_object(); 

    int num_of_curves = 2; 
    coordinate *curves[] = {curve_1, curve_2}; 
    long size_of_curve[] = {curve_1_size, curve_2_size}; 
    std::vector<Polyline> polylines; 

    for(int n = 0; n < num_of_curves; n++){ 
     std::vector<Point> points; 
     Point p_0 = Point(curves[n][0].x, curves[n][0].y); 
     points.push_back(p_0); 
     for(long i = 1; i < size_of_curve[n]; i++){ 
      Point p_i = Point(curves[n][i].x, curves[n][i].y); 
      if(p_i != points.back()){ 
       points.push_back(p_i); 
      } 
     } 
     polylines.push_back(construct_polyline(points.begin(), points.end())); 
    } 

    std::list<Point> intersection_points; 
    CGAL::compute_intersection_points(polylines.begin(), polylines.end(), 
             std::back_inserter(intersection_points), 
             false, polyline_traits); 

    int num_of_intersections = intersection_points.size(); 
    Point intersection_point; 
    for (int j = 0; j < num_of_intersections; j++){ 
     if (j == max_num_of_intersections) 
      break; 
     intersection_point = intersection_points.front(); 
     intersections[j].x = intersection_point.x(); 
     intersections[j].y = intersection_point.y(); 
     intersection_points.pop_front(); 
    } 

    return num_of_intersections; 
}