Re: [boost] [iterator] Silent-but-deadly bug in iterator_facade category

Subject: Re: [boost] [iterator] Silent-but-deadly bug in iterator_facade category
From: Gabriel Redner (gredner_at_[hidden])
Date: 2013-05-06 17:42:11

Hi Paul,

Thanks for your reply.

>  For it to be a
> `std::random_access_iterator_tag` it must a reference. That is,
> `iterator_traits<X>::reference` must be an actual reference.

Can you point me at a reference (pun not intended) for this
requirement?  The sites I've looked at don't mention this [1-3].  Is
it a requirement for, say, bidirectional iterators too?  Your message
makes it sound like this is specific to random access iterators.

If the iterator's reference must be a real reference type, then why
does iterator_facade not check this at compile time?

And in any case, isn't this a flaw?  my_iterator can be advanced etc.
in constant time - why should the STL be forced to use a
possibly-suboptimal overload of some algorithm on account of the
reference type?

Confused,
-Gabe

[1] http://www.cplusplus.com/reference/iterator/RandomAccessIterator/
[2] http://en.cppreference.com/w/cpp/concept/RandomAccessIterator
[3] http://www.sgi.com/tech/stl/RandomAccessIterator.html