On Thu, May 27, 2010 at 9:28 PM, David Abrahams <dave@boostpro.com> wrote:
At Thu, 27 May 2010 20:30:18 -0400, Lorenzo Caminiti wrote:
On Thu, May 27, 2010 at 4:59 PM, Jeffrey Lee Hellrung, Jr. <jhellrung@ucla.edu> wrote:
And now that I've written this, I see this exact example is already elaborated on at the boost website:
http://www.boost.org/community/generic_programming.html#tag_dispatching
Great! The code from the Boost links above is _exactly_ what I was looking for.
Actually that example is missing one crucial detail: inheritance of tags matching the refinement hierarchy. The first few lines *should* read:
struct input_iterator_tag { }; struct bidirectional_iterator_tag : input_iterator_tag { }; struct random_access_iterator_tag : bidirectional_iterator_tag { };
or, if you want to reflect the standard accurately,
struct input_iterator_tag { }; struct forward_iterator_tag : input_iterator_tag { }; struct bidirectional_iterator_tag : forward_iterator_tag { }; struct random_access_iterator_tag : bidirectional_iterator_tag { };
That detail is what allows us to avoid writing a separate version of advance_dispatch for forward iterators.
I see. I have modified the Boost example to follow what STL does as you indicated above. All seems to be working well. Thanks a lot. -- Lorenzo