tuple_helpers.hpp

C++的一个好库。。。现在很流行

    typename A, typename B, typename C, typename D, typename E, typename F,
    typename G, typename H, typename I, typename J, typename K
>
struct concat_tuple<tuple<A, B, C, D, E, F, G, H, I, J, K>, nil_t> {

    typedef tuple<A, B, C, D, E, F, G, H, I, J, K> type;
};

#if PHOENIX_LIMIT > 12
///////////////////////////////////////////////////////////////////////////////
//
//  concat tuple <12 member> class
//
///////////////////////////////////////////////////////////////////////////////
template <
    typename A, typename B, typename C, typename D, typename E, typename F,
    typename G, typename H, typename I, typename J, typename K, typename L,
    typename AppendT
>
struct concat_tuple<tuple<A, B, C, D, E, F, G, H, I, J, K, L>, AppendT> {

    typedef tuple<A, B, C, D, E, F, G, H, I, J, K, L, AppendT> type;
};

template <
    typename A, typename B, typename C, typename D, typename E, typename F,
    typename G, typename H, typename I, typename J, typename K, typename L
>
struct concat_tuple<tuple<A, B, C, D, E, F, G, H, I, J, K, L>, nil_t> {

    typedef tuple<A, B, C, D, E, F, G, H, I, J, K, L> type;
};

///////////////////////////////////////////////////////////////////////////////
//
//  concat tuple <13 member> class
//
///////////////////////////////////////////////////////////////////////////////
template <
    typename A, typename B, typename C, typename D, typename E, typename F,
    typename G, typename H, typename I, typename J, typename K, typename L,
    typename M,
    typename AppendT
>
struct concat_tuple<tuple<A, B, C, D, E, F, G, H, I, J, K, L, M>, AppendT> {

    typedef tuple<A, B, C, D, E, F, G, H, I, J, K, L, M, AppendT> type;
};

template <
    typename A, typename B, typename C, typename D, typename E, typename F,
    typename G, typename H, typename I, typename J, typename K, typename L,
    typename M
>
struct concat_tuple<tuple<A, B, C, D, E, F, G, H, I, J, K, L, M>, nil_t> {

    typedef tuple<A, B, C, D, E, F, G, H, I, J, K, L, M> type;
};

///////////////////////////////////////////////////////////////////////////////
//
//  concat tuple <14 member> class
//
///////////////////////////////////////////////////////////////////////////////
template <
    typename A, typename B, typename C, typename D, typename E, typename F,
    typename G, typename H, typename I, typename J, typename K, typename L,
    typename M, typename N,
    typename AppendT
>
struct concat_tuple<tuple<A, B, C, D, E, F, G, H, I, J, K, L, M, N>, AppendT> {

    typedef tuple<A, B, C, D, E, F, G, H, I, J, K, L, M, N, AppendT> type;
};

template <
    typename A, typename B, typename C, typename D, typename E, typename F,
    typename G, typename H, typename I, typename J, typename K, typename L,
    typename M, typename N
>
struct concat_tuple<tuple<A, B, C, D, E, F, G, H, I, J, K, L, M, N>, nil_t> {

    typedef tuple<A, B, C, D, E, F, G, H, I, J, K, L, M, N> type;
};

#endif
#endif
#endif
#endif

///////////////////////////////////////////////////////////////////////////////
//
//  concat_tuples type computer
//
//      This template class returns the type of a tuple built from the
//      concatenation of two given tuples.
//
///////////////////////////////////////////////////////////////////////////////
template <typename TupleT1, typename TupleT2, int N, typename AppendT>
struct concat_tuple_element {

    typedef
        typename concat_tuple_element<
                typename concat_tuple<TupleT1, AppendT>::type, TupleT2, N+1,
                typename tuple_element<N+1, TupleT2>::type
            >::type
        type;
};

template <typename TupleT1, typename TupleT2, int N>
struct concat_tuple_element<TupleT1, TupleT2, N, nil_t> {

    typedef TupleT1 type;
};

template <typename TupleT1, typename TupleT2>
struct concat_tuples {

    typedef
        typename concat_tuple_element<
                TupleT1, TupleT2, 0,
                typename tuple_element<0, TupleT2>::type
            >::type
        type;
};

///////////////////////////////////////////////////////////////////////////////
//
//  convert_actors template function
//
//      The convert_actors template functions constructs a new tuple object
//      composed of the elements returned by the actors contained in the
//      input tuple. (i.e. the given tuple type 'actor_tuple' contains a set
//      of actors to evaluate and the resulting tuple contains the results of
//      evaluating the actors.)
//
///////////////////////////////////////////////////////////////////////////////
template <typename ActorT, typename TupleT>
struct actor_result; // forward declaration

namespace impl
{
    template <unsigned N>
    struct convert_actors_ {};
}

template <typename TupleResultT, typename ActorTupleT>
TupleResultT
convert_actors(ActorTupleT const& actor_tuple)
{
    BOOST_STATIC_ASSERT(ActorTupleT::length <= TupleResultT::length);
    BOOST_STATIC_CONSTANT(int, length = TupleResultT::length);
    return impl::convert_actors_<length>
        ::template apply<TupleResultT, ActorTupleT>::do_(actor_tuple);
}

namespace impl
{
    template <int N, typename TupleResultT, typename ActorTupleT>
    struct convert_actor
    {
        typedef typename tuple_element<N, TupleResultT>::type type;

        template <bool C>
        struct is_default_t {};
        typedef is_default_t<true>  is_default;
        typedef is_default_t<false> is_not_default;

        static type
        actor_element(ActorTupleT const& /*actor_tuple*/, is_default)
        {
            return type(); // default construct
        }

        static type
        actor_element(ActorTupleT const& actor_tuple, is_not_default)
        {
            BOOST_STATIC_ASSERT(ActorTupleT::length <= TupleResultT::length);
            return actor_tuple[tuple_index<N>()](); // apply the actor
        }

        static type
        do_(ActorTupleT const& actor_tuple)
        {
            return actor_element(
                actor_tuple, is_default_t<(N >= ActorTupleT::length)>());
        }
    };

    ///////////////////////////////////////
    template <>
    struct convert_actors_<1>
    {
        template <typename TupleResultT, typename ActorTupleT>
        struct apply
        {
            static TupleResultT
            do_(ActorTupleT const& actor_tuple)
            {
                typedef impl::convert_actor<0, TupleResultT, ActorTupleT> converter0;

                return TupleResultT(
                    converter0::do_(actor_tuple)
                );
            }
        };
    };

    ///////////////////////////////////////
    template <>
    struct convert_actors_<2>
    {
        template <typename TupleResultT, typename ActorTupleT>
        struct apply
        {
            static TupleResultT
            do_(ActorTupleT const& actor_tuple)
            {
                typedef impl::convert_actor<0, TupleResultT, ActorTupleT> converter0;
                typedef impl::convert_actor<1, TupleResultT, ActorTupleT> converter1;

                using namespace tuple_index_names;
                return TupleResultT(
                        converter0::do_(actor_tuple)
                    ,   converter1::do_(actor_tuple)
                );
            }
        };
    };

    ///////////////////////////////////////
    template <>
    struct convert_actors_<3>
    {
        template <typename TupleResultT, typename ActorTupleT>
        struct apply
        {
            static TupleResultT
            do_(ActorTupleT const& actor_tuple)
            {
                typedef impl::convert_actor<0, TupleResultT, ActorTupleT> converter0;
                typedef impl::convert_actor<1, TupleResultT, ActorTupleT> converter1;
                typedef impl::convert_actor<2, TupleResultT, ActorTupleT> converter2;

                using namespace tuple_index_names;
                return TupleResultT(
                        converter0::do_(actor_tuple)
                    ,   converter1::do_(actor_tuple)
                    ,   converter2::do_(actor_tuple)
                );
            }
        };
    };

    #if PHOENIX_LIMIT > 3

    /////////////////////////////////////
    template <>
    struct convert_actors_<4>
    {
        template <typename TupleResultT, typename ActorTupleT>
        struct apply
        {
            static TupleResultT
            do_(ActorTupleT const& actor_tuple)
            {
                typedef impl::convert_actor<0, TupleResultT, ActorTupleT> converter0;
                typedef impl::convert_actor<1, TupleResultT, ActorTupleT> converter1;
                typedef impl::convert_actor<2, TupleResultT, ActorTupleT> converter2;
                typedef impl::convert_actor<3, TupleResultT, ActorTupleT> converter3;

                using namespace tuple_index_names;
                return TupleResultT(
                        converter0::do_(actor_tuple)
                    ,   converter1::do_(actor_tuple)
                    ,   converter2::do_(actor_tuple)
                    ,   converter3::do_(actor_tuple)
                );
            }
        };
    };

    /////////////////////////////////////
    template <>
    struct convert_actors_<5>
    {
        template <typename TupleResultT, typename ActorTupleT>
        struct apply
        {
            static TupleResultT
            do_(ActorTupleT const& actor_tuple)
            {
                typedef impl::convert_actor<0, TupleResultT, ActorTupleT> converter0;
                typedef impl::convert_actor<1, TupleResultT, ActorTupleT> converter1;
                typedef impl::convert_actor<2, TupleResultT, ActorTupleT> converter2;
                typedef impl::convert_actor<3, TupleResultT, ActorTupleT> converter3;
                typedef impl::convert_actor<4, TupleResultT, ActorTupleT> converter4;

                using namespace tuple_index_names;
                return TupleResultT(
                        converter0::do_(actor_tuple)
                    ,   converter1::do_(actor_tuple)
                    ,   converter2::do_(actor_tuple)
                    ,   converter3::do_(actor_tuple)
                    ,   converter4::do_(actor_tuple)
                );
            }
        };
    };

    /////////////////////////////////////
    template <>
    struct convert_actors_<6>
    {
        template <typename TupleResultT, typename ActorTupleT>
        struct apply
        {
            static TupleResultT
            do_(ActorTupleT const& actor_tuple)
            {
                typedef impl::convert_actor<0, TupleResultT, ActorTupleT> converter0;
                typedef impl::convert_actor<1, TupleResultT, ActorTupleT> converter1;
                typedef impl::convert_actor<2, TupleResultT, ActorTupleT> converter2;
                typedef impl::convert_actor<3, TupleResultT, ActorTupleT> converter3;
                typedef impl::convert_actor<4, TupleResultT, ActorTupleT> converter4;
                typedef impl::convert_actor<5, TupleResultT, ActorTupleT> converter5;

                using namespace tuple_index_names;
                return TupleResultT(
                        converter0::do_(actor_tuple)
                    ,   converter1::do_(actor_tuple)
                    ,   converter2::do_(actor_tuple)
                    ,   converter3::do_(actor_tuple)
                    ,   converter4::do_(actor_tuple)
                    ,   converter5::do_(actor_tuple)
                );
            }
        };
    };

    #if PHOENIX_LIMIT > 6

    /////////////////////////////////////
    template <>
    struct convert_actors_<7>
    {
        template <typename TupleResultT, typename ActorTupleT>
        struct apply
        {
            static TupleResultT
            do_(ActorTupleT const& actor_tuple)
            {
                typedef impl::convert_actor<0, TupleResultT, ActorTupleT> converter0;
                typedef impl::convert_actor<1, TupleResultT, ActorTupleT> converter1;
                typedef impl::convert_actor<2, TupleResultT, ActorTupleT> converter2;
                typedef impl::convert_actor<3, TupleResultT, ActorTupleT> converter3;
                typedef impl::convert_actor<4, TupleResultT, ActorTupleT> converter4;
                typedef impl::convert_actor<5, TupleResultT, ActorTupleT> converter5;
                typedef impl::convert_actor<6, TupleResultT, ActorTupleT> converter6;