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// Boost.Varaint
// Contains multivisitors that are implemented via variadic templates and std::tuple
//
// See http://www.boost.org for most recent version, including documentation.
//
// Copyright Antony Polukhin, 2013-2014.
//
// 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_VARIANT_DETAIL_MULTIVISITORS_CPP11_BASED_HPP
#define BOOST_VARIANT_DETAIL_MULTIVISITORS_CPP11_BASED_HPP
#if defined(_MSC_VER)
# pragma once
#endif
#include <boost/variant/detail/apply_visitor_unary.hpp>
#include "boost/variant/variant_fwd.hpp" // for BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES
#if defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES) || defined(BOOST_NO_CXX11_HDR_TUPLE)
# error "This file requires <tuple> and variadic templates support"
#endif
#include <tuple>
namespace boost {
namespace detail { namespace variant {
// Implementing some of the C++14 features in C++11
template <std::size_t... I> class index_sequence {};
template <std::size_t N, std::size_t... I>
struct make_index_sequence
: make_index_sequence<N-1, N-1, I...>
{};
template <std::size_t... I>
struct make_index_sequence<0, I...>
: index_sequence<I...>
{};
template <class... Types>
std::tuple<Types&...> forward_as_tuple_simple(Types&... args) BOOST_NOEXCEPT
{
return std::tuple<Types&...>(args...);
}
// Implementing some of the helper tuple methods
template <std::size_t... I, typename Tuple>
std::tuple<typename std::tuple_element<I + 1, Tuple>::type...>
tuple_tail_impl(const Tuple& tpl, index_sequence<I...>)
{
return std::tuple<
typename std::tuple_element<I + 1, Tuple>::type...
> (std::get<I + 1>(tpl)...);
}
template <typename Head, typename... Tail>
std::tuple<Tail...> tuple_tail(const std::tuple<Head, Tail...>& tpl)
{
return tuple_tail_impl(tpl, make_index_sequence<sizeof...(Tail)>());
}
// Forward declaration
template <typename Visitor, typename Visitables, typename... Values>
class one_by_one_visitor_and_value_referer;
template <typename Visitor, typename Visitables, typename... Values>
inline one_by_one_visitor_and_value_referer<Visitor, Visitables, Values... >
make_one_by_one_visitor_and_value_referer(
Visitor& visitor, Visitables visitables, std::tuple<Values&...> values
)
{
return one_by_one_visitor_and_value_referer<Visitor, Visitables, Values... > (
visitor, visitables, values
);
}
template <typename Visitor, typename Visitables, typename... Values>
class one_by_one_visitor_and_value_referer
{
Visitor& visitor_;
std::tuple<Values&...> values_;
Visitables visitables_;
public: // structors
one_by_one_visitor_and_value_referer(
Visitor& visitor, Visitables visitables, std::tuple<Values&...> values
) BOOST_NOEXCEPT
: visitor_(visitor)
, values_(values)
, visitables_(visitables)
{}
public: // visitor interfaces
typedef typename Visitor::result_type result_type;
template <typename Value>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type) operator()(Value& value) const
{
return ::boost::apply_visitor(
make_one_by_one_visitor_and_value_referer(
visitor_,
tuple_tail(visitables_),
std::tuple_cat(values_, std::tuple<Value&>(value))
)
, std::get<0>(visitables_) // getting Head element
);
}
private:
one_by_one_visitor_and_value_referer& operator=(const one_by_one_visitor_and_value_referer&);
};
template <typename Visitor, typename... Values>
class one_by_one_visitor_and_value_referer<Visitor, std::tuple<>, Values...>
{
Visitor& visitor_;
std::tuple<Values&...> values_;
public:
one_by_one_visitor_and_value_referer(
Visitor& visitor, std::tuple<> /*visitables*/, std::tuple<Values&...> values
) BOOST_NOEXCEPT
: visitor_(visitor)
, values_(values)
{}
typedef typename Visitor::result_type result_type;
template <class Tuple, std::size_t... I>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type) do_call(Tuple t, index_sequence<I...>) const {
return visitor_(std::get<I>(t)...);
}
template <typename Value>
BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type) operator()(Value& value) const
{
return do_call(
std::tuple_cat(values_, std::tuple<Value&>(value)),
make_index_sequence<sizeof...(Values) + 1>()
);
}
};
}} // namespace detail::variant
template <class Visitor, class T1, class T2, class T3, class... TN>
inline BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
apply_visitor(const Visitor& visitor, T1& v1, T2& v2, T3& v3, TN&... vn)
{
return ::boost::apply_visitor(
::boost::detail::variant::make_one_by_one_visitor_and_value_referer(
visitor,
::boost::detail::variant::forward_as_tuple_simple(v2, v3, vn...),
std::tuple<>()
),
v1
);
}
template <class Visitor, class T1, class T2, class T3, class... TN>
inline BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
apply_visitor(Visitor& visitor, T1& v1, T2& v2, T3& v3, TN&... vn)
{
return ::boost::apply_visitor(
::boost::detail::variant::make_one_by_one_visitor_and_value_referer(
visitor,
::boost::detail::variant::forward_as_tuple_simple(v2, v3, vn...),
std::tuple<>()
),
v1
);
}
} // namespace boost
#endif // BOOST_VARIANT_DETAIL_MULTIVISITORS_CPP11_BASED_HPP
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