// Copyright (C) 2007 Dean Michael Berris <dmberris@friendster.com>
// 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)

#if !defined(BOOST_SELECT_2007_11_20)
#define BOOST_SELECT_2007_11_20

#ifndef SELECT_TUPLE_MAX_SIZE
#define SELECT_TUPLE_MAX_SIZE 10
#endif

#include <boost/mpl/at.hpp>
#include <boost/mpl/int.hpp>
#include <boost/mpl/vector/vector10.hpp>
#include <boost/tuple/tuple.hpp>
#include <boost/preprocessor/repetition.hpp>

namespace boost {

    namespace impl {
        template <typename T1, typename T2, unsigned int const N>
        struct choose : mpl::at_c< mpl::vector2<T1, T2>, N >
        { };

        // dispatcher
        template <typename T1, typename T2, unsigned int N>
        inline typename choose<T1, T2, N>::type
            choose_element(std::pair<T1, T2> const & pair) {
                return choose_element_dispatch(pair, mpl::int_<N>());
        };

        template <typename T1, typename T2>
        inline T1
            choose_element_dispatch(std::pair<T1, T2> const & pair, mpl::int_<0>) {
                return pair.first;
        };

        template <typename T1, typename T2>
        inline T2
            choose_element_dispatch(std::pair<T1, T2> const & pair, mpl::int_<1>) {
                return pair.second;
        };

    };

    template <unsigned int const N>
    struct select {

        template <typename T1, typename T2>
			typename impl::choose<T1, T2, N>::type
			operator() (std::pair<T1, T2> const & pair) const {
				return impl::choose_element<T1, T2, N>(pair);
			};

#define SELECT_size(z, n, unused) \
		template <BOOST_PP_ENUM_PARAMS(n, typename T)>	\
		typename tuples::element<N, tuple<BOOST_PP_ENUM_PARAMS(n,T)> >::type \
		operator() (tuple<BOOST_PP_ENUM_PARAMS(n,T)> const & tuple_) const { return tuples::get<N>(tuple_); };

		BOOST_PP_REPEAT_FROM_TO(3, SELECT_TUPLE_MAX_SIZE, SELECT_size, ~);

#undef SELECT_size

    };

}; // namespace boost
        
#endif