CGAL users discussion list

[Roger House <>]

I have not been able to get this expression to compile with MSVC++

   iterator_distance(P.edges_begin(), I)

where both operands are of type Polygon_2::Edge_const_iterator.  The comment
in the code below shows the compiler error message.  The attached file
contains the entire error message with all its gory details.

It seems that two iterators of the same type which point to the same object
should be acceptable to iterator_distance, but perhaps I fail to understand
something.  

Any help will be appreciated.

Roger House
Software Developer

// idistbug.cpp  --  Problem with the CGAL iterator_distance function

#include "CGAL\Cartesian.h"
#include "CGAL\Polygon_2.h"
#include <CGAL\Polygon_set_2.h>
#include <CGAL\circulator.h>
#include <iostream>
#include <cassert>

using namespace std;

typedef CGAL::Cartesian<double>       K;
typedef K::Point_2                    Point;
typedef CGAL::Polygon_2<K>            Polygon_2;


int main()
{
   cout << "Begin test of iterator_distance"  << endl;

   Point pointsP[] = {Point(0, 0), Point(1, 0), Point(1, 1), Point(0, 1)};
   Polygon_2 P(pointsP, pointsP+4);

   Polygon_2::Edge_const_iterator I = P.edges_begin();

   ++I;

   // The call of iterator_distance in the following statement does not 
compile:
   // c:\hped\builds\sr\dev33x\rlocal\debug\build\include\stlport\stl\
   // _iterator_base.h(372) : error C2678: binary '-' : no operator found
   // which takes a left-hand operand of type
   // 'const CGAL::Polygon_2_edge_iterator<Traits_,Container_>'
   // (or there is no acceptable conversion)

   cout << "  iterator_distance = " << 
iterator_distance(P.edges_begin(), I) << endl;

   cout << "Press any nonwhitespace key and Enter to terminate"  << endl;

   string c;
   cin >> c;
}

// end idistbug.cpp


c:\hped\builds\sr\dev33x\rlocal\debug\build\include\stlport\stl\
    _iterator_base.h(372) : error C2678: binary '-' : no operator found 
    which takes a left-hand operand of type 
    'const CGAL::Polygon_2_edge_iterator<Traits_,Container_>' 
    (or there is no acceptable conversion)
        with
        [
            Traits_=K,
            
Container_=stlp_std::vector<CGAL::Point_2<CGAL::Cartesian<double>>>
        ]
        
c:\users\roghouse\332\build\projects\cgal_eesof\include\cgal\polygon_2\polygon_2_edge_iterator.h(137):
 could be 'CGAL::Polygon_2_edge_iterator<Traits_,Container_> 
CGAL::Polygon_2_edge_iterator<Traits_,Container_>::operator -(__w64 int)'
        with
        [
            Traits_=K,
            
Container_=stlp_std::vector<CGAL::Point_2<CGAL::Cartesian<double>>>
        ]
        
c:\users\roghouse\332\build\projects\cgal_eesof\include\cgal\polygon_2\polygon_2_edge_iterator.h(143):
 or '__w64 int CGAL::Polygon_2_edge_iterator<Traits_,Container_>::operator 
-(const CGAL::Polygon_2_edge_iterator<Traits_,Container_> &)'
        with
        [
            Traits_=K,
            
Container_=stlp_std::vector<CGAL::Point_2<CGAL::Cartesian<double>>>
        ]
        
c:\users\roghouse\332\build\projects\cgal_eesof\include\cgal\functions_on_enums.h(41):
 or 'CGAL::Sign CGAL::operator -(CGAL::Sign)' [found using argument-dependent 
lookup]
        while trying to match the argument list '(const 
CGAL::Polygon_2_edge_iterator<Traits_,Container_>, const 
CGAL::Polygon_2_edge_iterator<Traits_,Container_>)'
        with
        [
            Traits_=K,
            
Container_=stlp_std::vector<CGAL::Point_2<CGAL::Cartesian<double>>>
        ]
        
c:\hped\builds\sr\dev33x\rlocal\debug\build\include\stlport\stl\_iterator_base.h(378)
 : see reference to function template instantiation '__w64 int 
stlp_std::__distance<_InputIterator>(const _RandomAccessIterator &,const 
_RandomAccessIterator &,const stlp_std::random_access_iterator_tag &)' being 
compiled
        with
        [
            
_InputIterator=CGAL::Polygon_2_edge_iterator<K,stlp_std::vector<CGAL::Point_2<CGAL::Cartesian<double>>>>,
            
_RandomAccessIterator=CGAL::Polygon_2_edge_iterator<K,stlp_std::vector<CGAL::Point_2<CGAL::Cartesian<double>>>>
        ]
        
c:\users\roghouse\332\build\projects\cgal_eesof\include\cgal\circulator.h(473)
 : see reference to function template instantiation '__w64 int 
stlp_std::distance<I>(_InputIterator,_InputIterator)' being compiled
        with
        [
            
I=CGAL::Polygon_2_edge_iterator<K,stlp_std::vector<CGAL::Point_2<CGAL::Cartesian<double>>>>,
            
_InputIterator=CGAL::Polygon_2_edge_iterator<K,stlp_std::vector<CGAL::Point_2<CGAL::Cartesian<double>>>>
        ]
        
c:\users\roghouse\332\build\projects\cgal_eesof\include\cgal\circulator.h(484)
 : see reference to function template instantiation '__w64 int 
CGAL::I_iterator_distance<IC>(const I &,const I &,CGAL::Iterator_tag)' being 
compiled
        with
        [
            
IC=CGAL::Polygon_2_edge_iterator<K,stlp_std::vector<CGAL::Point_2<CGAL::Cartesian<double>>>>,
            
I=CGAL::Polygon_2_edge_iterator<K,stlp_std::vector<CGAL::Point_2<CGAL::Cartesian<double>>>>
        ]
        c:\users\roghouse\332\build\projects\eecad\cgaltest\idistbug.cpp(26) 
: see reference to function template instantiation '__w64 int 
CGAL::iterator_distance<CGAL::Polygon_2_edge_iterator<Traits_,Container_>>(const
 IC &,const IC &)' being compiled
        with
        [
            Traits_=K,
            
Container_=stlp_std::vector<CGAL::Point_2<CGAL::Cartesian<double>>>,
            
IC=CGAL::Polygon_2_edge_iterator<K,stlp_std::vector<CGAL::Point_2<CGAL::Cartesian<double>>>>
        ]