CGAL users discussion list

[Jann Poppinga <>]

Hi all,

I am working with the last example given on 
http://www.cgal.org/Manual/3.4/doc_html/cgal_manual/Straight_skeleton_2/Chapter_main.html 
- growing a polygon. I could compile it neither with a list nor with a 
set as a container, because of the function compute_outer_frame_margin() 
in file CGAL/computer_outer_frame_margin.h. This function is templated 
on a iterator type and takes a pair of them. It then iterates over them 
using (line 60)

for( ForwardPointIterator lCurr = aBegin ; lCurr < aEnd ; ++lCurr )

,i.e. using < instead of the usual !=. Wouldn't it be possible to use != 
here? I had to write this ridiculous adaptor class to use the function - 
and it worked:

template<class Iterator>
class PointIteratorAdaptor {
public:
    typedef typename Iterator::iterator_category iterator_category;
    typedef typename Iterator::value_type value_type;
    typedef typename Iterator::difference_type difference_type;
    //    typedef int differency_type;
    typedef typename Iterator::pointer pointer;
    typedef typename Iterator::reference reference;


    PointIteratorAdaptor( Iterator pIt ) : aIt(pIt ) {};
    const SkeletonKernel::Point_2& operator*() const { return *aIt; }
    bool operator<( const PointIteratorAdaptor& that ) const {
        return aIt!=that.aIt; }
    bool operator==( const PointIteratorAdaptor& that ) const {
        return aIt==that.aIt; }
    PointIteratorAdaptor operator++( ) { ++aIt; return *this; } 

    PointIteratorAdaptor operator--( ) { --aIt; return *this ; } 

private: 

    Iterator aIt; 

}; 



Please note again this function:
    bool operator<( const PointIteratorAdaptor& that ) const {
        return aIt!=that.aIt; }


From looking at the code I could find no reason for using <, so IMHO it 
only limits the usability of the function.

Kind regards,
Jann