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

Subject: Re: [Boost-users] A doubt in Boost multi index
From: joaquin_at_[hidden]
Date: 2010-07-30 08:35:41

Gokulakannan Somasundaram escribió:
>
>
> On Fri, Jul 30, 2010 at 7:49 PM, <joaquin_at_[hidden] 
> <mailto:joaquin_at_[hidden]>> 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 <boost/multi_index/ordered_index.hpp>
  #include <boost/mpl/at.hpp>
  #include <boost/mpl/bool.hpp>

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

  template<typename KeyFromValue,typename Compare>
  struct is_ordered_index_impl<
    boost::multi_index::ordered_unique<KeyFromValue,Compare>
  >:boost::mpl::true_{};

  template<typename KeyFromValue,typename Compare>
  struct is_ordered_index_impl<
    boost::multi_index::ordered_non_unique<KeyFromValue,Compare>
  >:boost::mpl::true_{};

  template<typename MultiIndexContainer,int N>
  struct is_ordered_index:
    is_ordered_index_impl<
      typename boost::mpl::at_c<
        typename MultiIndexContainer::index_specifier_type_list,
        N
      >::type
    >
  {};

  #include <boost/mpl/begin_end.hpp>
  #include <boost/mpl/contains.hpp>
  #include <boost/mpl/distance.hpp>
  #include <boost/mpl/find_if.hpp>

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

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

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

  /* testing */

  #include <boost/multi_index_container.hpp>
  #include <boost/multi_index/sequenced_index.hpp>
  #include <boost/multi_index/hashed_index.hpp>
  #include <boost/multi_index/identity.hpp>
  #include <boost/mpl/assert.hpp>

  using namespace boost::multi_index;

  typedef multi_index_container<
    int,
    indexed_by<
      ordered_unique<tag<struct i0>,identity<int> >,
      ordered_non_unique<tag<struct i1>, identity<int> >,
      hashed_unique<tag<struct i2>, identity<int> >,
      hashed_non_unique<tag<struct i3>, identity<int> >,
      sequenced<tag<struct i4> >
    >
  > multi_t;

  BOOST_MPL_ASSERT    ((is_ordered_index<multi_t,0>));
  BOOST_MPL_ASSERT    ((is_ordered_index<multi_t,1>));
  BOOST_MPL_ASSERT_NOT((is_ordered_index<multi_t,2>));
  BOOST_MPL_ASSERT_NOT((is_ordered_index<multi_t,3>));
  BOOST_MPL_ASSERT_NOT((is_ordered_index<multi_t,4>));

  BOOST_MPL_ASSERT    ((is_ordered_index_with_tag<multi_t,i0>));
  BOOST_MPL_ASSERT    ((is_ordered_index_with_tag<multi_t,i1>));
  BOOST_MPL_ASSERT_NOT((is_ordered_index_with_tag<multi_t,i2>));
  BOOST_MPL_ASSERT_NOT((is_ordered_index_with_tag<multi_t,i3>));
  BOOST_MPL_ASSERT_NOT((is_ordered_index_with_tag<multi_t,i4>));

  int main(){}

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo