optional.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_OPTIONAL_HPP)
#define MQTT_OPTIONAL_HPP
 
#if defined(MQTT_STD_OPTIONAL)
 
#include <optional>
 
#else  // defined(MQTT_STD_OPTIONAL)
 
#include <boost/optional.hpp>
 
#endif // defined(MQTT_STD_VARIANT)
 
#include <mqtt/namespace.hpp>
 
namespace MQTT_NS {
 
#if defined(MQTT_STD_OPTIONAL)
 
using std::optional;
using std::nullopt_t;
using in_place_t = std::in_place_t;
static constexpr auto in_place_init = in_place_t{};
static constexpr auto nullopt = std::nullopt;
 
#else  // defined(MQTT_STD_OPTIONAL)
 
using boost::optional;
using nullopt_t = boost::none_t;
using boost::in_place_init;
static const auto nullopt = boost::none;
 
#endif // defined(MQTT_STD_OPTIONAL)
 
} // namespace MQTT_NS
 
#endif // MQTT_OPTIONAL_HPP