Chris@102: //  Boost.Varaint
Chris@102: //  Contains multivisitors that are implemented via variadic templates and std::tuple
Chris@102: //
Chris@102: //  See http://www.boost.org for most recent version, including documentation.
Chris@102: //
Chris@102: //  Copyright Antony Polukhin, 2013-2014.
Chris@102: //
Chris@102: //  Distributed under the Boost
Chris@102: //  Software License, Version 1.0. (See accompanying file
Chris@102: //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt).
Chris@102: 
Chris@102: #ifndef BOOST_VARIANT_DETAIL_MULTIVISITORS_CPP11_BASED_HPP
Chris@102: #define BOOST_VARIANT_DETAIL_MULTIVISITORS_CPP11_BASED_HPP
Chris@102: 
Chris@102: #if defined(_MSC_VER)
Chris@102: # pragma once
Chris@102: #endif
Chris@102: 
Chris@102: #include <boost/variant/detail/apply_visitor_unary.hpp>
Chris@102: #include "boost/variant/variant_fwd.hpp" // for BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES
Chris@102: 
Chris@102: #if defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES) || defined(BOOST_NO_CXX11_HDR_TUPLE)
Chris@102: #   error "This file requires <tuple> and variadic templates support"
Chris@102: #endif
Chris@102: 
Chris@102: #include <tuple>
Chris@102: 
Chris@102: namespace boost { 
Chris@102: 
Chris@102: namespace detail { namespace variant {
Chris@102: 
Chris@102:     // Implementing some of the C++14 features in C++11
Chris@102:     template <std::size_t... I> class index_sequence {};
Chris@102: 
Chris@102:     template <std::size_t N, std::size_t... I> 
Chris@102:     struct make_index_sequence 
Chris@102:         : make_index_sequence<N-1, N-1, I...> 
Chris@102:     {};
Chris@102:     template <std::size_t... I> 
Chris@102:     struct make_index_sequence<0, I...> 
Chris@102:         : index_sequence<I...> 
Chris@102:     {};
Chris@102: 
Chris@102:     template <class... Types>
Chris@102:     std::tuple<Types&...> forward_as_tuple_simple(Types&... args) BOOST_NOEXCEPT
Chris@102:     {
Chris@102:         return std::tuple<Types&...>(args...);
Chris@102:     }
Chris@102: 
Chris@102:     // Implementing some of the helper tuple methods
Chris@102:     template <std::size_t... I, typename Tuple>
Chris@102:     std::tuple<typename std::tuple_element<I + 1, Tuple>::type...> 
Chris@102:         tuple_tail_impl(const Tuple& tpl, index_sequence<I...>)
Chris@102:     {
Chris@102:         return std::tuple<
Chris@102:             typename std::tuple_element<I + 1, Tuple>::type...
Chris@102:         > (std::get<I + 1>(tpl)...);
Chris@102:     }
Chris@102: 
Chris@102:     template <typename Head, typename... Tail>
Chris@102:     std::tuple<Tail...> tuple_tail(const std::tuple<Head, Tail...>& tpl)
Chris@102:     {
Chris@102:         return tuple_tail_impl(tpl, make_index_sequence<sizeof...(Tail)>());
Chris@102:     }
Chris@102: 
Chris@102: 
Chris@102: 
Chris@102:     // Forward declaration
Chris@102:     template <typename Visitor, typename Visitables, typename... Values>
Chris@102:     class one_by_one_visitor_and_value_referer;
Chris@102: 
Chris@102:     template <typename Visitor, typename Visitables, typename... Values>
Chris@102:     inline one_by_one_visitor_and_value_referer<Visitor, Visitables, Values... >
Chris@102:         make_one_by_one_visitor_and_value_referer(
Chris@102:             Visitor& visitor, Visitables visitables, std::tuple<Values&...> values
Chris@102:         )
Chris@102:     {
Chris@102:         return one_by_one_visitor_and_value_referer<Visitor, Visitables, Values... > (
Chris@102:             visitor, visitables, values
Chris@102:         );
Chris@102:     }
Chris@102: 
Chris@102:     template <typename Visitor, typename Visitables, typename... Values>
Chris@102:     class one_by_one_visitor_and_value_referer
Chris@102:     {
Chris@102:         Visitor&                        visitor_;
Chris@102:         std::tuple<Values&...>          values_;
Chris@102:         Visitables                      visitables_;
Chris@102: 
Chris@102:     public: // structors
Chris@102:         one_by_one_visitor_and_value_referer(
Chris@102:                     Visitor& visitor, Visitables visitables, std::tuple<Values&...> values
Chris@102:                 ) BOOST_NOEXCEPT
Chris@102:             : visitor_(visitor)
Chris@102:             , values_(values)
Chris@102:             , visitables_(visitables)
Chris@102:         {}
Chris@102: 
Chris@102:     public: // visitor interfaces
Chris@102:         typedef typename Visitor::result_type result_type;
Chris@102: 
Chris@102:         template <typename Value>
Chris@102:         BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type) operator()(Value& value) const
Chris@102:         {
Chris@102:             return ::boost::apply_visitor(
Chris@102:                 make_one_by_one_visitor_and_value_referer(
Chris@102:                     visitor_,
Chris@102:                     tuple_tail(visitables_),
Chris@102:                     std::tuple_cat(values_, std::tuple<Value&>(value))
Chris@102:                 )
Chris@102:                 , std::get<0>(visitables_) // getting Head element
Chris@102:             );
Chris@102:         }
Chris@102: 
Chris@102:     private:
Chris@102:         one_by_one_visitor_and_value_referer& operator=(const one_by_one_visitor_and_value_referer&);
Chris@102:     };
Chris@102: 
Chris@102:     template <typename Visitor, typename... Values>
Chris@102:     class one_by_one_visitor_and_value_referer<Visitor, std::tuple<>, Values...>
Chris@102:     {
Chris@102:         Visitor&                        visitor_;
Chris@102:         std::tuple<Values&...>          values_;
Chris@102: 
Chris@102:     public:
Chris@102:         one_by_one_visitor_and_value_referer(
Chris@102:                     Visitor& visitor, std::tuple<> /*visitables*/, std::tuple<Values&...> values
Chris@102:                 ) BOOST_NOEXCEPT
Chris@102:             : visitor_(visitor)
Chris@102:             , values_(values)
Chris@102:         {}
Chris@102: 
Chris@102:         typedef typename Visitor::result_type result_type;
Chris@102: 
Chris@102:         template <class Tuple, std::size_t... I>
Chris@102:         BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type) do_call(Tuple t, index_sequence<I...>) const {
Chris@102:             return visitor_(std::get<I>(t)...);
Chris@102:         }
Chris@102: 
Chris@102:         template <typename Value>
Chris@102:         BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type) operator()(Value& value) const
Chris@102:         {
Chris@102:             return do_call(
Chris@102:                 std::tuple_cat(values_, std::tuple<Value&>(value)),
Chris@102:                 make_index_sequence<sizeof...(Values) + 1>()
Chris@102:             );
Chris@102:         }
Chris@102:     };
Chris@102: 
Chris@102: }} // namespace detail::variant
Chris@102: 
Chris@102:     template <class Visitor, class T1, class T2, class T3, class... TN>
Chris@102:     inline BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
Chris@102:         apply_visitor(const Visitor& visitor, T1& v1, T2& v2, T3& v3, TN&... vn)
Chris@102:     {
Chris@102:         return ::boost::apply_visitor(
Chris@102:             ::boost::detail::variant::make_one_by_one_visitor_and_value_referer(
Chris@102:                 visitor,
Chris@102:                 ::boost::detail::variant::forward_as_tuple_simple(v2, v3, vn...),
Chris@102:                 std::tuple<>()
Chris@102:             ),
Chris@102:             v1
Chris@102:         );
Chris@102:     }
Chris@102:     
Chris@102:     template <class Visitor, class T1, class T2, class T3, class... TN>
Chris@102:     inline BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
Chris@102:         apply_visitor(Visitor& visitor, T1& v1, T2& v2, T3& v3, TN&... vn)
Chris@102:     {
Chris@102:         return ::boost::apply_visitor(
Chris@102:             ::boost::detail::variant::make_one_by_one_visitor_and_value_referer(
Chris@102:                 visitor,
Chris@102:                 ::boost::detail::variant::forward_as_tuple_simple(v2, v3, vn...),
Chris@102:                 std::tuple<>()
Chris@102:             ),
Chris@102:             v1
Chris@102:         );
Chris@102:     }
Chris@102: 
Chris@102: } // namespace boost
Chris@102: 
Chris@102: #endif // BOOST_VARIANT_DETAIL_MULTIVISITORS_CPP11_BASED_HPP
Chris@102: