variant.hpp

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// Copyright Takatoshi Kondo 2018
//
// 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(MQTT_VARIANT_HPP)
#define MQTT_VARIANT_HPP
 
#include <mqtt/config.hpp>
#include <mqtt/namespace.hpp>
 
#if defined(MQTT_STD_VARIANT)
 
#include <variant>
 
namespace MQTT_NS {
 
using std::variant;
 
template<typename T, typename U>
decltype(auto) variant_get(U && arg)
{
    return std::get<T>(std::forward<U>(arg));
}
 
template<typename T>
decltype(auto) variant_idx(T const& arg)
{
    return arg.index();
}
 
using std::visit;
 
} // namespace MQTT_NS
 
#else  // defined(MQTT_STD_VARIANT)
 
#include <boost/variant.hpp>
#include <boost/variant/get.hpp>
#include <boost/variant/apply_visitor.hpp>
 
namespace MQTT_NS {
 
using boost::variant;
 
template<typename T, typename U>
decltype(auto) variant_get(U && arg)
{
    return boost::get<T>(std::forward<U>(arg));
}
 
template<typename T>
decltype(auto) variant_idx(T const& arg)
{
    return arg.which();
}
 
template <typename Visitor, typename... Variants>
constexpr decltype(auto) visit(Visitor&& vis, Variants&&... vars)
{
    return boost::apply_visitor(std::forward<Visitor>(vis), std::forward<Variants>(vars)...);
}
 
} // namespace MQTT_NS
 
#endif // defined(MQTT_STD_VARIANT)
 
#endif // MQTT_VARIANT_HPP