#include <boost/mpl/pair.hpp>
using namespace boost::mpl;
  template
  < typename Enum
  >
struct enum_size
{
        static
      unsigned const
    size=0
      //specializations should return
      //the actual value for given Enum.
      ;
};  
  template
  < typename... Pairs
  >
struct enums_offsets_pairs
;  
  template
  <
  >
struct enums_offsets_pairs<>
{
        static 
      unsigned const
    offset=0;
};  
  template
  < typename Tag
  , typename Enum
  , typename... Pairs
  >
struct enums_offsets_pairs
  < pair<Tag,Enum>
  , Pairs...
  >
: enums_offsets_pairs
  < Pairs...
  >  
{
        typedef
      enums_offsets_pairs
      < Pairs...
      >  
    super_t;    
        static 
      unsigned const
    offset=enum_size<Enum>::size+super_t::offset;
};  
  template
  < typename... Pairs
  >
struct enums_offsets
;
  template
  < typename... Tags
  , typename... Enums
  >
struct enums_offsets
  < pair<Tags,Enums>...
  >
: enums_offsets_pairs
  < pair<Tags,Enums>...
  >
{
};

enum E1{e11,e12,e13};
enum E2{e21,e22,e23};

struct T1;
struct T2;

template<>struct enum_size<E1>
{  static unsigned const size=1;
};
template<>struct enum_size<E2>
{  static unsigned const size=2;
};
    typedef
  enums_offsets
  < pair<T1,E1>
  , pair<T2,E2>
  >
eos;

#include <iostream>
int main()
{
    std::cout<<eos::offset<<"\n";
    return 0;
}