#ifndef BOOST_PP_IS_ITERATING
    ///////////////////////////////////////////////////////////////////////////////
    /// \file args.hpp
    /// Contains definition of \c term\<\>, \c list1\<\>, \c list2\<\>, ...
    /// class templates.
    //
    //  Copyright 2008 Eric Niebler. 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 BOOST_PROTO_ARGS_HPP_EAN_04_01_2005
    #define BOOST_PROTO_ARGS_HPP_EAN_04_01_2005

    #include <boost/config.hpp>
    #include <boost/detail/workaround.hpp>
    #include <boost/preprocessor/cat.hpp>
    #include <boost/preprocessor/arithmetic/dec.hpp>
    #include <boost/preprocessor/iteration/iterate.hpp>
    #include <boost/preprocessor/repetition/enum_params.hpp>
    #include <boost/preprocessor/repetition/repeat.hpp>
    #include <boost/preprocessor/repetition/repeat_from_to.hpp>
    #include <boost/type_traits/is_function.hpp>
    #include <boost/type_traits/is_abstract.hpp>
    #include <boost/mpl/if.hpp>
    #include <boost/mpl/or.hpp>
    #include <boost/mpl/void.hpp>
    #include <boost/proto/proto_fwd.hpp>

    namespace boost { namespace proto
    {
        namespace detail
        {
            // All classes derived from std::ios_base have these public nested types,
            // and are non-copyable. This is an imperfect test, but it's the best we
            // we can do.
            template<typename T>
            yes_type check_is_iostream(
                typename T::failure *
              , typename T::Init *
              , typename T::fmtflags *
              , typename T::iostate *
              , typename T::openmode *
              , typename T::seekdir *
            );

            template<typename T>
            no_type check_is_iostream(...);

            template<typename T>
            struct is_iostream
            {
                static bool const value = sizeof(yes_type) == sizeof(check_is_iostream<T>(0,0,0,0,0,0));
                typedef mpl::bool_<value> type;
            };

            /// INTERNAL ONLY
            // This should be a customization point. And it serves the same purpose
            // as the is_noncopyable trait in Boost.Foreach. 
            template<typename T>
            struct ref_only
              : mpl::or_<
                    is_function<T>
                  , is_abstract<T>
                  , is_iostream<T>
                >
            {};

            /// INTERNAL ONLY
            template<typename Expr>
            struct expr_traits
            {
                typedef Expr value_type;
                typedef Expr &reference;
                typedef Expr const &const_reference;
            };

            /// INTERNAL ONLY
            template<typename Expr>
            struct expr_traits<Expr &>
            {
                typedef Expr value_type;
                typedef Expr &reference;
                typedef Expr &const_reference;
            };

            /// INTERNAL ONLY
            template<typename Expr>
            struct expr_traits<Expr const &>
            {
                typedef Expr value_type;
                typedef Expr const &reference;
                typedef Expr const &const_reference;
            };

            /// INTERNAL ONLY
            template<typename T>
            struct term_traits
            {
                typedef T value_type;
                typedef T &reference;
                typedef T const &const_reference;
            };

            /// INTERNAL ONLY
            template<typename T>
            struct term_traits<T &>
            {
                typedef typename mpl::if_c<ref_only<T>::value, T &, T>::type value_type;
                typedef T &reference;
                typedef T &const_reference;
            };

            /// INTERNAL ONLY
            template<typename T>
            struct term_traits<T const &>
            {
                typedef T value_type;
                typedef T const &reference;
                typedef T const &const_reference;
            };

            /// INTERNAL ONLY
            template<typename T, std::size_t N>
            struct term_traits<T (&)[N]>
            {
                typedef T value_type[N];
                typedef T (&reference)[N];
                typedef T (&const_reference)[N];
            };

            /// INTERNAL ONLY
            template<typename T, std::size_t N>
            struct term_traits<T const (&)[N]>
            {
                typedef T value_type[N];
                typedef T const (&reference)[N];
                typedef T const (&const_reference)[N];
            };

            /// INTERNAL ONLY
            template<typename T, std::size_t N>
            struct term_traits<T[N]>
            {
                typedef T value_type[N];
                typedef T (&reference)[N];
                typedef T const (&const_reference)[N];
            };

            /// INTERNAL ONLY
            template<typename T, std::size_t N>
            struct term_traits<T const[N]>
            {
                typedef T value_type[N];
                typedef T const (&reference)[N];
                typedef T const (&const_reference)[N];
            };
        }

        ////////////////////////////////////////////////////////////////////////////////////////////
        #define BOOST_PROTO_DEFINE_CHILD_N(Z, N, DATA)                                              \
            typedef BOOST_PP_CAT(Arg, N) BOOST_PP_CAT(child, N);                                    \
            /**< INTERNAL ONLY */

        #define BOOST_PROTO_DEFINE_VOID_N(z, n, data)                                               \
            typedef mpl::void_ BOOST_PP_CAT(child, n);                                              \
            /**< INTERNAL ONLY */

        namespace argsns_
        {
            /// \brief A type sequence, for use as the 2nd parameter to the \c expr\<\> class template.
            ///
            /// A type sequence, for use as the 2nd parameter to the \c expr\<\> class template.
            /// The types in the sequence correspond to the children of a node in an expression tree.
            template< typename Arg0 >
            struct term
            {
                BOOST_STATIC_CONSTANT(long, arity = 0);
                typedef Arg0 child0;

                #if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1500))
                BOOST_PP_REPEAT_FROM_TO(1, BOOST_PROTO_MAX_ARITY, BOOST_PROTO_DEFINE_VOID_N, ~)
                #endif

                /// INTERNAL ONLY
                ///
                typedef Arg0 back_;
            };

            #define BOOST_PP_ITERATION_PARAMS_1 (3, (1, BOOST_PROTO_MAX_ARITY, <boost/proto/args.hpp>))
            #include BOOST_PP_ITERATE()

            #undef BOOST_PROTO_DEFINE_CHILD_N
        }
        ////////////////////////////////////////////////////////////////////////////////////////////
    }}
    #endif

#else

    #define N BOOST_PP_ITERATION()

        /// \brief A type sequence, for use as the 2nd parameter to the \c expr\<\> class template.
        ///
        /// A type sequence, for use as the 2nd parameter to the \c expr\<\> class template.
        /// The types in the sequence correspond to the children of a node in an expression tree.
        template< BOOST_PP_ENUM_PARAMS(N, typename Arg) >
        struct BOOST_PP_CAT(list, N)
        {
            BOOST_STATIC_CONSTANT(long, arity = N);
            BOOST_PP_REPEAT(N, BOOST_PROTO_DEFINE_CHILD_N, ~)

            #if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1500))
            BOOST_PP_REPEAT_FROM_TO(N, BOOST_PROTO_MAX_ARITY, BOOST_PROTO_DEFINE_VOID_N, ~)
            #endif

            /// INTERNAL ONLY
            ///
            typedef BOOST_PP_CAT(Arg, BOOST_PP_DEC(N)) back_;
        };

    #undef N

#endif