optional.hpp

// Copyright 2015 MongoDB Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 
#pragma once
 
#include <bsoncxx/config/prelude.hpp>
 
#if defined(BSONCXX_POLY_USE_MNMLSTC)
 
#include <core/optional.hpp>
 
namespace bsoncxx {
inline namespace v_noabi {
namespace stdx {
 
using ::core::make_optional;
using ::core::nullopt;
using ::core::nullopt_t;
using ::core::optional;
 
}  // namespace stdx
}  // namespace v_noabi
}  // namespace bsoncxx
 
#elif defined(BSONCXX_POLY_USE_BOOST)
 
#include <boost/none.hpp>
#include <boost/optional/optional.hpp>
#include <boost/optional/optional_io.hpp>
 
namespace bsoncxx {
inline namespace v_noabi {
namespace stdx {
 
using ::boost::optional;
using nullopt_t = ::boost::none_t;
 
// TODO(MSVC): This would be better expressed as constexpr, but VS2015U1 can't do it.
const nullopt_t nullopt{::boost::none};
using ::boost::make_optional;
 
}  // namespace stdx
}  // namespace v_noabi
}  // namespace bsoncxx
 
#elif defined(BSONCXX_POLY_USE_STD_EXPERIMENTAL)
 
#include <experimental/optional>
 
namespace bsoncxx {
inline namespace v_noabi {
namespace stdx {
 
using ::std::experimental::make_optional;
using ::std::experimental::nullopt;
using ::std::experimental::nullopt_t;
using ::std::experimental::optional;
 
}  // namespace stdx
}  // namespace v_noabi
}  // namespace bsoncxx
 
#elif defined(BSONCXX_POLY_USE_STD)
 
#include <optional>
 
namespace bsoncxx {
inline namespace v_noabi {
namespace stdx {
 
using ::std::make_optional;
using ::std::nullopt;
using ::std::nullopt_t;
using ::std::optional;
 
}  // namespace stdx
}  // namespace v_noabi
}  // namespace bsoncxx
 
#else
#error "Cannot find a valid polyfill for optional"
#endif
 
#include <bsoncxx/config/postlude.hpp>