[boost] Σχετ: [TypeSort] Automatic type sorting

Subject: [boost] Σχετ: [TypeSort] Automatic type sorting
From: costis glynos (cosglyn_at_[hidden])
Date: 2015-03-20 13:30:04

That's actually very useful! However a less complicated interface would definitely be more appreciated! Maybe some wrapper functions or macros would do the trick. 

     Στις 5:16 μ.μ. Παρασκευή, 20 Μαρτίου 2015, ο/η Mathias Gaunard <mathias.gaunard_at_[hidden]> έγραψε:
   

 On 20/03/2015 17:49, costis glynos wrote:
>>
>> You also need to use Boost.Fusion to make it into a tuple at the end,
>> since this is what you want.
>>
>> Here is an example:
>>
>> #include <boost/mpl/sort.hpp>
>> #include <boost/mpl/vector.hpp>
>> #include <boost/mpl/sizeof.hpp>
>> #include <boost/fusion/include/as_vector.hpp>
>> #include <boost/fusion/adapted/mpl.hpp>
>> #include <iostream>
>>
>> int main()
>> {
>>Â  Â  namespace mpl = boost::mpl;
>>Â  Â  namespace fusion = boost::fusion;
>>
>>Â  Â  typedef mpl::vector<short, int, short> types;
>>Â  Â  typedef mpl::sort<types, mpl::less< mpl::sizeof_<mpl::_1>
>>Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  , mpl::sizeof_<mpl::_2>
>>Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  >
>>Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  >::type sorted_types;
>>Â  Â  typedef fusion::result_of::as_vector<sorted_types>::type tuple;
>>
>>Â  Â  tuple t;
>>Â  Â  std::cout << sizeof(t) << std::endl; // 8 instead of 12
>> }
>>
>> This appears to work.

 > That's fantastic! Thank you for your recommendation.

You probably need to be able to access the final tuple with the original 
indices though, which is a bit more involved.

#include <boost/mpl/sort.hpp>
#include <boost/mpl/vector.hpp>
#include <boost/mpl/range_c.hpp>
#include <boost/mpl/transform.hpp>
#include <boost/mpl/front.hpp>
#include <boost/mpl/back.hpp>
#include <boost/mpl/zip_view.hpp>
#include <boost/mpl/copy.hpp>
#include <boost/mpl/sizeof.hpp>
#include <boost/mpl/at.hpp>
#include <boost/fusion/include/as_vector.hpp>
#include <boost/fusion/include/at.hpp>
#include <boost/fusion/adapted/mpl.hpp>
#include <iostream>

int main()
{
  namespace mpl = boost::mpl;
  namespace fusion = boost::fusion;

  typedef mpl::vector<short, int, short> types;
  typedef mpl::copy<
    mpl::zip_view<
      mpl::vector< types
                  , mpl::range_c<long, 0L, mpl::size<types>::value>
                  >
    >
  , mpl::back_inserter< mpl::vector0<> >
  >::type indexes_types;
  typedef mpl::sort<
    indexes_types
  , mpl::less< mpl::sizeof_< mpl::front<mpl::_1> >
              , mpl::sizeof_< mpl::front<mpl::_2> >
              >
  >::type indexes_types_sorted;
  typedef mpl::transform<
    indexes_types_sorted
  , mpl::front<mpl::_1>
  >::type sorted_types;
  typedef mpl::transform<
    indexes_types_sorted
  , mpl::back<mpl::_1>
  >::type sorted_indexes;
  typedef fusion::result_of::as_vector<sorted_types>::type tuple;

  tuple t;
  std::cout << sizeof( fusion::at_c<mpl::at_c<sorted_indexes, 
0>::type::value>(t) ) << std::endl;
  std::cout << sizeof( fusion::at_c<mpl::at_c<sorted_indexes, 
1>::type::value>(t) ) << std::endl;
  std::cout << sizeof( fusion::at_c<mpl::at_c<sorted_indexes, 
2>::type::value>(t) ) << std::endl;
}

This could make an interesting addition to Boost.Fusion.

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