CGAL static_cast失败

Question

对于我的论文，我使用的是一年前另一位学生编写的一些CGAL代码。 但是，我无法构建它。

给出错误的函数如下：

std::set<Curve_handle> originatingCurves(PL_Arrangement arrangement, VertexHandleSet vertices)
{
  std::set<Curve_handle> curves;
  for (Vertex_handle vertex : vertices)
  {
    auto heStart = vertex->incident_halfedges();
    auto heCurrent = vertex->incident_halfedges();
    do
    {
      Halfedge_handle handle = static_cast<Halfedge_handle>(heCurrent);
      //Unless the halfedge represents a piece of overlap between curves, it has only one originating curve
      for (auto curve = arrangement.originating_curves_begin(handle); curve != arrangement.originating_curves_end(handle); curve++)
      {
        curves.emplace(static_cast<Curve_handle>(curve));
      }
      heCurrent++;
    } while (heCurrent != heStart);
  }
  return curves;
}

与线curves.emplace(static_cast<Curve_handle>(curve)); 出现以下错误：

Severity    Code    Description Project File    Line    Suppression State
Error   C2672   'std::_Tree<std::_Tset_traits<_Kty,_Pr,_Alloc,false>>::emplace': no matching overloaded function found  CurvedNonograms c:\users\demeessias\documents\1. studie\0.masterthesis\curvednonograms-code\curvednonograms\curvednonograms\curve_manipulation.cpp  222 
Error   C2440   'static_cast': cannot convert from 'CGAL::Arrangement_on_surface_with_history_2<GeomTraits_,CGAL::Arr_bounded_planar_topology_traits_2<GeomTraits_,Dcel>>::Originating_curve_iterator' to 'Curve_handle'    CurvedNonograms c:\users\demeessias\documents\1. studie\0.masterthesis\curvednonograms-code\curvednonograms\curvednonograms\curve_manipulation.cpp  222 

用户定义的类型（例如Curve_handle在以下头文件中定义：

#pragma once

#include <CGAL/Cartesian.h>
#include <CGAL/CORE_algebraic_number_traits.h>
#include <CGAL/Arr_Bezier_curve_traits_2.h>
#include <CGAL/Arrangement_2.h>
#include <CGAL/Arrangement_with_history_2.h>
#include <CGAL/Arr_extended_dcel.h>
#include <CGAL/Iso_rectangle_2.h>
#include <CGAL/Arr_walk_along_line_point_location.h>
#include <CGAL/Arr_observer.h>
//#include <CGAL/basic.h>

#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
#include <CGAL/Arr_segment_traits_2.h>
#include <CGAL/Arr_polyline_traits_2.h>

struct FaceData
{
  FaceData () 
  {
    colored = false;
    solved = false;
  };
  bool colored = false;
  bool solved = false;
};

////   Bezier curve traits  ////

typedef CGAL::CORE_algebraic_number_traits Nt_traits;
typedef Nt_traits::Rational NT;
typedef Nt_traits::Rational Rational;
typedef Nt_traits::Algebraic Algebraic;
//Simple_cartesian = for easier debugging, no ref counting, values directly in objects
typedef CGAL::Cartesian<Rational> Kernel;
typedef CGAL::Cartesian<Algebraic> Alg_kernel;
//typedef Kernel::Point_2 Rat_Point;
typedef CGAL::Arr_Bezier_curve_traits_2<Kernel, Alg_kernel, Nt_traits> Traits;

typedef Traits::Curve_2 Bezier;
typedef Traits::Point_2 Point;
typedef Kernel::Iso_rectangle_2 BoundingBox;

typedef CGAL::Arr_face_extended_dcel<Traits, FaceData> Dcel;
typedef CGAL::Arrangement_with_history_2<Traits, Dcel> Arrangement;  //Not really used anymore, because of crashes/problems/bugs



////  Polyline traits  ////

// Instantiate the traits class using a user-defined kernel
// and Segment_traits_2.
typedef CGAL::Exact_predicates_exact_constructions_kernel PL_Kernel;
typedef CGAL::Arr_segment_traits_2<PL_Kernel>             Segment_traits;
typedef CGAL::Arr_polyline_traits_2<Segment_traits>       PL_traits;
// Identical instantiation can be achieved using the default Kernel:
// typedef CGAL::Arr_polyline_traits_2<>                    Geom_traits_2;
typedef PL_traits::Point_2                            PL_Point;
typedef PL_traits::Segment_2                          Segment;
typedef PL_traits::Curve_2                            Polyline;

typedef CGAL::Arr_extended_dcel<PL_traits, bool/*not used*/, double, FaceData> PL_Dcel;
typedef CGAL::Arrangement_with_history_2<PL_traits, PL_Dcel> PL_Arrangement;  //This is now the only type of arrangement that we actually use
//Handles
typedef PL_Arrangement::Vertex_const_handle         Vertex_handle;
typedef PL_Arrangement::Halfedge_const_handle       Halfedge_handle;
typedef PL_Arrangement::Curve_const_handle          Curve_handle;

//Point location
typedef CGAL::Arr_walk_along_line_point_location<PL_Arrangement> PointLocationAlg;
typedef CGAL::Arr_point_location_result<PL_Arrangement>::Type PointLocationResult;


//Less function to use for (vertex/halfedge/face) handle sets
template <class Handle> struct HandleLess
{
  bool operator()(Handle a, Handle b)
  {
    return (a.ptr() - b.ptr() < 0);
  }
};
typedef std::set<Vertex_handle, HandleLess<Vertex_handle>> VertexHandleSet;


//Arrangement observer that keeps the face colours correct
class FaceColorObserver : public CGAL::Arr_observer<PL_Arrangement>
{
private:
  bool coloredBeforeMerge;
public:
  FaceColorObserver(PL_Arrangement& arrangement) :
    CGAL::Arr_observer<PL_Arrangement>(arrangement)
  {}

  virtual void after_split_face(Face_handle oldFace, Face_handle newFace, bool)
  {
    newFace->data().colored = oldFace->data().colored;
  }

  virtual void before_merge_face(Face_handle face1, Face_handle face2, Halfedge_handle)
  {
    //The assumption is that only same-color faces get merged
    CGAL_precondition(face1->data().colored ==  face2->data().colored);
    coloredBeforeMerge = face1->data().colored;// && face2->data().colored;
  }
  virtual void after_merge_face(Face_handle newFace)
  {
    newFace->data().colored = coloredBeforeMerge;
  }
};

//Arrangement of line segments
typedef CGAL::Arrangement_2<Segment_traits> Seg_Arrangement;

我以前与代码库有关的问题与我使用的CGAL版本比原始学生要高，所以我怀疑这也可能是这里的问题，但我不知道该如何替换代码行。

Answer 1

CGAL::Arrangement_on_surface_with_history_2::Originating_curve_iterator 继承自 I_Dereference_iterator 。

Curve_handle是： PL_Arrangement::Curve_const_handle 。 而且，由于不从任何继承CGAL::Arrangement_on_surface_with_history_2::Originating_curve_iterator或I_Dereference_iterator你不能static_cast之间的2 static_cast只能继承层次结构中用于向下/向上转换。

Answer 2

Arrangement :: Originating_curve_iterator（也定义为Arrangement :: Originating_curve_handle）具有用户定义的到Arrangement :: Curve_handle的转换和另一个到Arrangement :: Curve_const_handle的转换，因此该语句没有问题

curves.emplace(static_cast<Curve_handle>(curve));

但是，在

for (auto curve = arrangement.originating_curves_begin(handle); 
     curve != arrangement.originating_curves_end(handle); curve++)

编译器假定curve是一个非常量迭代器，因此只需将“ auto”替换为“ Curve_handle”（定义为PL_Arrangement :: Curve_const_handle）。