on Sat Jan 07 2012, Ronald Garcia <rxg-AT-cs.cmu.edu> wrote:
Hi,
In MultiArray I would like use iterator_facade to create an iterator that can satisfy random_access_traversal, input_iterator_tag, and output_iterator_tag. I see that in the file boost/iterator/detail/facade_iterator_category.hpp, at line 138 there is a class in the boost::detail namespace declared
template <class Category, class Traversal> struct iterator_category_with_traversal
So it looks like passing: boost::detail::iterator_category_with_traversal<boost::detail::input_output_iterator_tag,boost::random_traversal_tag>
as the CategoryOrTraversal would be what I want. However, two components above are in the detail namespace, so I am not sure if they are meant to be used by other libraries. Is this a safe operation?
Using things in detail namespaces is never really "safe" unless you own the surrounding namespace.
Side Notes: In my searches, I found a few buggy bits in the docs and code comments:
- In boost/iterator/detail/facade_iterator_category.hpp, line 76, there's a comment: // If writability has been disabled per the above metafunction, the // result will not be convertible to output_iterator_tag.
This comment corresponds to behavior that was removed in changeset: https://svn.boost.org/trac/boost/changeset/21683
Now the result will never be convertible to output_iterator_tag.
- In the documentation for iterator_facade, there's a bit of a booboo where the function is first written: iterator-category(CategoryOrTraversal, value_type, reference)
Then defined as:
iterator-category(C,R,V)
So I think the argument order is flipped.
Please open Trac tickets for any of these that don't already have them. Thanks! -- Dave Abrahams BoostPro Computing http://www.boostpro.com