// Copyright David Abrahams 2002.

 // 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 BASES_DWA2002321_HPP

 # define BASES_DWA2002321_HPP

 # include <boost/python/detail/prefix.hpp>

 # include <boost/type_traits/object_traits.hpp>

 # include <boost/python/detail/type_list.hpp>

 # include <boost/mpl/if.hpp>

 # include <boost/mpl/bool.hpp>

 # include <boost/preprocessor/enum_params_with_a_default.hpp>

 # include <boost/preprocessor/enum_params.hpp>

 namespace boost { namespace python { 

 # define BOOST_PYTHON_BASE_PARAMS BOOST_PP_ENUM_PARAMS_Z(1, BOOST_PYTHON_MAX_BASES, Base)

   // A type list for specifying bases

   template < BOOST_PP_ENUM_PARAMS_WITH_A_DEFAULT(BOOST_PYTHON_MAX_BASES, typename Base, mpl::void_) >

   struct bases : detail::type_list< BOOST_PYTHON_BASE_PARAMS >::type

   {};

   namespace detail

   {

 # ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION

     template <class T> struct specifies_bases

         : mpl::false_

     {

     };

     template < BOOST_PP_ENUM_PARAMS_Z(1, BOOST_PYTHON_MAX_BASES, class Base) >

     struct specifies_bases< bases< BOOST_PYTHON_BASE_PARAMS > >

         : mpl::true_

     {

     };

 # else

     template < BOOST_PP_ENUM_PARAMS(BOOST_PYTHON_MAX_BASES, class Base) >

     static char is_bases_helper(bases< BOOST_PYTHON_BASE_PARAMS > const&);

     static char (& is_bases_helper(...) )[256];

     template <class T>

     struct specifies_bases

     {

      private:

         static typename add_reference<T>::type make();

         BOOST_STATIC_CONSTANT(bool, non_ref = !is_reference<T>::value);

      public:

         BOOST_STATIC_CONSTANT(bool, value = non_ref & (sizeof(is_bases_helper(make())) == 1));

         typedef mpl::bool_<value> type;

     };

 # endif

     template <class T, class Prev = bases<> >

     struct select_bases

         : mpl::if_<

                 specifies_bases<T>

                 , T

                 , Prev

           >

     {

     };

   }

 # undef BOOST_PYTHON_BASE_PARAMS

 }} // namespace boost::python

 #endif // BASES_DWA2002321_HPP