Re: [Boost-users] A doubt in Boost multi index

30 Jul 2010


      Gokulakannan Somasundaram escribió:
...
On Fri, Jul 30, 2010 at 7:49 PM, mailto:joaquin@tid.es> wrote:
Gokulakannan Somasundaram escribió:
Hi,
          In boost multi-index, can i verify whether a particular
        index type is
         ordered/not or not through meta programming?  There are the
        ordered
         indexes, hash indexes, sequence indexes etc. Can i find them out
         through meta programming?
You can if you're given the multi_index_containr type and the position
    of the index:
Thanks a lot. Is it possible to do the same with named tags?
With a little more effort:

  #include 
  #include 
  #include 

  template<typename IndexSpecifier>
  struct is_ordered_index_impl:boost::mpl::false_{};

  template
  struct is_ordered_index_impl<
    boost::multi_index::ordered_unique
...
:boost::mpl::true_{};
template
  struct is_ordered_index_impl<
    boost::multi_index::ordered_non_unique
...
:boost::mpl::true_{};
template
  struct is_ordered_index:
    is_ordered_index_impl<
      typename boost::mpl::at_c<
        typename MultiIndexContainer::index_specifier_type_list,
        N
      >::type
    >
  {};

  #include 
  #include 
  #include 
  #include 

  template<typename Index>
  struct tag_list
  {
    typedef typename Index::tag_list type;
  };

  template
  struct tag_pos:
    boost::mpl::distance<
      typename boost::mpl::begin<IndexList>::type,
      typename boost::mpl::find_if<
        IndexList,
        boost::mpl::containsboost::mpl::_,Tag>
      >::type
    >
  {};

  template
  struct is_ordered_index_with_tag:
    is_ordered_index<
      MultiIndexContainer,
      tag_pos::value
    >
  {};


  /* testing */

  #include 
  #include 
  #include 
  #include 
  #include 

  using namespace boost::multi_index;

  typedef multi_index_container<
    int,
    indexed_by<
      ordered_unique,
      ordered_non_unique,
      hashed_unique,
      hashed_non_unique,
      sequenced
    >
...
multi_t;
BOOST_MPL_ASSERT    ((is_ordered_index));
  BOOST_MPL_ASSERT    ((is_ordered_index));
  BOOST_MPL_ASSERT_NOT((is_ordered_index));
  BOOST_MPL_ASSERT_NOT((is_ordered_index));
  BOOST_MPL_ASSERT_NOT((is_ordered_index));

  BOOST_MPL_ASSERT    ((is_ordered_index_with_tag));
  BOOST_MPL_ASSERT    ((is_ordered_index_with_tag));
  BOOST_MPL_ASSERT_NOT((is_ordered_index_with_tag));
  BOOST_MPL_ASSERT_NOT((is_ordered_index_with_tag));
  BOOST_MPL_ASSERT_NOT((is_ordered_index_with_tag));

  int main(){}

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Re: [Boost-users] A doubt in Boost multi index

joaquin＠tid.es