Re: Problem with Boost iterators

Carl Barron <>
3 Nov 2006 01:14:29 -0500
In article <>,
<> wrote:

Hi all,

I am running into the compilation error (gcc 4.0.2 Suse Linux) while
trying to compile the following simple program:

#include <boost/iterator/iterator_facade.hpp>

struct Pixel { int _abc;};

class PixelIterator :
  public boost::iterator_facade< PixelIterator, Pixel,
boost::random_access_traversal_tag >
  friend class boost::iterator_core_access;
  explicit PixelIterator() : _prPixel() {}
  explicit PixelIterator(Pixel * iprPixel) : _prPixel(iprPixel) {}
  void increment(){++_prPixel;}
  void decrement(){--_prPixel;}
  bool equal(const PixelIterator& iOther) const{ return _prPixel ==
iOther._prPixel; }
  Pixel& dereference() const{return *_prPixel;}
  void advance(int iDist){_prPixel += iDist;}
  uint distance_to(const PixelIterator& iOther) const{return
iOther._prPixel - _prPixel;}
  Pixel * _prPixel;

int main()
  Pixel p[10];
  PixelIterator it(p);
  it[1]._abc = 1;

The error message is
 'class boost::detail::operator_brackets_proxy<PixelIterator>' has
no member named '_abc

The Boost website is currently unavailable to look-up the documentation
but I am pretty match sure that the semantic of operator[] (int dist)
is *(it +dist). And indeed if I replace the last line in main with
(*(it+1))._abc = 1;

the error goes away.

Any help is greatly appreciated.

   The docs do state that if the proxy solution is not needed as in
your case your class can define operator [] and it will be used instead
of the operator[] supplied by iterator_facade. So if you add
   Pixel & operator [] (int n) {return *(_prPixel+n);} to Pixelterator
it will work since nothing is really destroyed here...

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