At Mon, 31 May 2010 12:09:56 -0700, Lubomir Bourdev wrote:
On 5/31/10 5:33 AM, "David Abrahams" <dave@boostpro.com> wrote:
At Sun, 30 May 2010 16:27:29 -1000, Christian Henning wrote:
One of the folks over at MSDN thinks that bit_aligned_pixel_iterator isn't implemented correctly with the interator_facade. He/She also thinks that iterator isn't fully standard compliant since it doesn't give a real reference but a proxy object instead when deferencing. I'm not sure if that's correct. Anyone knows if that's true or not.
It is indeed correct that ForwardIterator (and thus RandomAccessIterator) forbids the use of proxy references. That restriction is supposed to be dropped in C++0x.
That is unfortunate because in many places in GIL we require a proxy reference - such as dereferencing a planar pixel, for example. I don't see a way to avoid having proxy references... And we do want GIL iterators to be random access iterators.
Well fortunately, *most* standard libraries have done *some* work to accomodate such iterators in their algorithms. This might be a good reason to duplicate some of the STL's algorithms in boost::algorithm. -- Dave Abrahams BoostPro Computing http://www.boostpro.com