text: // Copyright 2005 Alexander Nasonov.
  // Distributed under the Boost Software License, Version 1.0. (See
  // accompanying file LICENSE_1_0.txt or copy at
  // http://www.boost.org/LICENSE_1_0.txt)
  
  #ifndef FILE_boost_type_traits_integral_promotion_hpp_INCLUDED
  #define FILE_boost_type_traits_integral_promotion_hpp_INCLUDED
  
  #include <boost/config.hpp>
  #include <boost/type_traits/integral_constant.hpp>
  #include <boost/type_traits/is_const.hpp>
  #include <boost/type_traits/is_enum.hpp>
  #include <boost/type_traits/is_volatile.hpp>
  #include <boost/type_traits/remove_cv.hpp>
  
  namespace boost {
  
  namespace type_traits { namespace detail {
  
  // 4.5/2
  template <class T> struct need_promotion : public boost::is_enum<T> {};
  
  // 4.5/1
  template<> struct need_promotion<char              > : public true_type {};
  template<> struct need_promotion<signed char       > : public true_type {};
  template<> struct need_promotion<unsigned char     > : public true_type {};
  template<> struct need_promotion<signed short int  > : public true_type {};
  template<> struct need_promotion<unsigned short int> : public true_type {};
  
  
  // Specializations for non-standard types.
  // Type is promoted if it's smaller then int.
  
  #define BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE(T) \
      template<> struct need_promotion<T>          \
          : public integral_constant<bool, (sizeof(T) < sizeof(int))> {};
  
  // Same set of integral types as in boost/type_traits/is_integral.hpp.
  // Please, keep in sync.
  #if (defined(BOOST_INTEL_CXX_VERSION) && defined(_MSC_VER) && (BOOST_INTEL_CXX_VERSION <= 600)) \
      || (defined(__BORLANDC__) && (__BORLANDC__ == 0x600) && (_MSC_VER < 1300))
  // TODO: common macro for this #if. Or better yet, PP SEQ of non-standard types.
  BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE(__int8          )
  BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE(unsigned __int8 )
  BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE(__int16         )
  BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE(unsigned __int16)
  BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE(__int32         )
  BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE(unsigned __int32)
  #ifdef __BORLANDC__
  BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE(unsigned __int64)
  BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE(         __int64)
  #endif
  #endif
  
  #if defined(BOOST_HAS_LONG_LONG)
  BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE(boost::ulong_long_type)
  BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE(boost::long_long_type )
  #elif defined(BOOST_HAS_MS_INT64)
  BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE(unsigned __int64)
  BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE(         __int64)
  #endif
  
  #undef BOOST_TT_AUX_PROMOTE_NONSTANDARD_TYPE
  
  
  #ifndef BOOST_NO_INTRINSIC_WCHAR_T
  // 4.5/2
  template<> struct need_promotion<wchar_t> : public true_type {};
  #endif
  
  // 4.5/3 (integral bit-field) is not supported.
  
  // 4.5/4
  template<> struct need_promotion<bool> : public true_type {};
  
  
  // Get promoted type by index and cv qualifiers.
  
  template<int Index, int IsConst, int IsVolatile> struct promote_from_index;
  
  #define BOOST_TT_AUX_PROMOTE_FROM_INDEX(N,T)                                   \
      template<> struct promote_from_index<N,0,0> { typedef T type; };           \
      template<> struct promote_from_index<N,0,1> { typedef T volatile type; };  \
      template<> struct promote_from_index<N,1,0> { typedef T const type; };     \
      template<> struct promote_from_index<N,1,1> { typedef T const volatile type; };
  
  
  BOOST_TT_AUX_PROMOTE_FROM_INDEX(1, int          )
  BOOST_TT_AUX_PROMOTE_FROM_INDEX(2, unsigned int )
  BOOST_TT_AUX_PROMOTE_FROM_INDEX(3, long         )
  BOOST_TT_AUX_PROMOTE_FROM_INDEX(4, unsigned long)
  
  
  // WARNING: integral promotions to non-standard types
  // long long and __int64 are not defined by the standard.
  // Additional specialisations and overloads shouldn't
  // introduce ambiguity, though.
  
  #if defined(BOOST_HAS_LONG_LONG)
  BOOST_TT_AUX_PROMOTE_FROM_INDEX(5, boost::long_long_type )
  BOOST_TT_AUX_PROMOTE_FROM_INDEX(6, boost::ulong_long_type)
  #elif defined(BOOST_HAS_MS_INT64)
  BOOST_TT_AUX_PROMOTE_FROM_INDEX(7, __int64         )
  BOOST_TT_AUX_PROMOTE_FROM_INDEX(8, unsigned __int64)
  #endif
  
  #undef BOOST_TT_AUX_PROMOTE_FROM_INDEX
  
  
  // Define BOOST_TT_AUX_PROMOTED_INDEX_TESTER:
  #if !defined(BOOST_MSVC)
  
  template<int N>
  struct sized_type_for_promotion
  {
      typedef char (&type)[N];
  };
  
  #define BOOST_TT_AUX_PROMOTED_INDEX_TESTER(I,T) \
      sized_type_for_promotion<I>::type promoted_index_tester(T);
  
  #else
  
  #define BOOST_TT_AUX_PROMOTED_INDEX_TESTER(I,T) \
      char (&promoted_index_tester(T))[I];
  
  #endif
  
  BOOST_TT_AUX_PROMOTED_INDEX_TESTER(1, int          )
  BOOST_TT_AUX_PROMOTED_INDEX_TESTER(2, unsigned int )
  BOOST_TT_AUX_PROMOTED_INDEX_TESTER(3, long         )
  BOOST_TT_AUX_PROMOTED_INDEX_TESTER(4, unsigned long)
  
  #if defined(BOOST_HAS_LONG_LONG)
  BOOST_TT_AUX_PROMOTED_INDEX_TESTER(5, boost::long_long_type )
  BOOST_TT_AUX_PROMOTED_INDEX_TESTER(6, boost::ulong_long_type)
  #elif defined(BOOST_HAS_MS_INT64)
  BOOST_TT_AUX_PROMOTED_INDEX_TESTER(7, __int64         )
  BOOST_TT_AUX_PROMOTED_INDEX_TESTER(8, unsigned __int64)
  #endif
  
  #undef BOOST_TT_AUX_PROMOTED_INDEX_TESTER
  
  
  // Get an index of promoted type for type T.
  // Precondition: need_promotion<T>
  template<class T>
  struct promoted_index
  {
      static T testee; // undefined
      BOOST_STATIC_CONSTANT(int, value = sizeof(promoted_index_tester(+testee)) );
      // Unary plus promotes testee                    LOOK HERE ---> ^
  };
  
  template<class T>
  struct integral_promotion_impl
  {
      typedef BOOST_DEDUCED_TYPENAME promote_from_index<
          (boost::type_traits::detail::promoted_index<T>::value)
        , (boost::is_const<T>::value)
        , (boost::is_volatile<T>::value)
        >::type type;
  };
  
  template<class T, bool b> struct integral_promotion { typedef T type; };
  template<class T> struct integral_promotion<T, true> : public integral_promotion_impl<T>{};
  
  } }
  
  template <class T> struct integral_promotion
  {
  private:
     typedef boost::type_traits::detail::need_promotion<typename remove_cv<T>::type> tag_type;
  public:
     typedef typename boost::type_traits::detail::integral_promotion<T, tag_type::value>::type type;
  };
  
  #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES)
  
     template <class T> using integral_promotion_t = typename integral_promotion<T>::type;
  
  #endif
  
  }
  
  #endif // #ifndef FILE_boost_type_traits_integral_promotion_hpp_INCLUDED
  
  