backports-optional.hpp File Reference

C++17 std::optional backport implemented using boost::optional. More...

#include "backports.hpp"
#include <boost/none.hpp>
#include <boost/optional.hpp>
#include <boost/utility/typed_in_place_factory.hpp>

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Classes
class	ndn::bad_optional_access
struct	ndn::in_place_t
class	ndn::nullopt_t
class	ndn::optional< T >
class	ndn::optional< T >

Namespaces
	ndn
	Copyright (c) 2013-2017 Regents of the University of California.

Functions
template<typename T >
constexpr optional< typename std::decay< T >::type >	ndn::make_optional (T &&value)
template<typename T , typename... Args>
constexpr optional< T >	ndn::make_optional (Args &&...args)
template<typename T >
constexpr bool	ndn::operator!= (const optional< T > &lhs, const optional< T > &rhs)
template<typename T >
constexpr bool	ndn::operator< (const optional< T > &lhs, const optional< T > &rhs)
template<typename T >
constexpr bool	ndn::operator<= (const optional< T > &lhs, const optional< T > &rhs)
template<typename T >
constexpr bool	ndn::operator== (const optional< T > &lhs, const optional< T > &rhs)
template<typename T >
constexpr bool	ndn::operator> (const optional< T > &lhs, const optional< T > &rhs)
template<typename T >
constexpr bool	ndn::operator>= (const optional< T > &lhs, const optional< T > &rhs)

Variables
constexpr in_place_t	ndn::in_place {}
constexpr nullopt_t	ndn::nullopt {0}

Detailed Description

C++17 std::optional backport implemented using boost::optional.

See also

http://open-std.org/JTC1/SC22/WG21/docs/papers/2016/n4594.pdf section 20.6

http://en.cppreference.com/w/cpp/utility/optional

Differences from C++17 include:

• No constructor and operator= taking a T&&, because boost::optional lacks a move constructor as of Boost 1.54
• No constructor, operator=, emplace, and make_optional with std::initializer_list
• In-place constructor and emplace require copyable arguments, because boost::in_place requires such
• Move constructor may or may not exist (it's implicitly defined when available), because boost::optional lacks a move constructor as of Boost 1.54
• Non-const operator-> and operator* are not constexpr
• value() is not constexpr
• swap is declared without noexcept specification
• No comparison operators with const T& or nullopt_t
• No specialized std::hash support

Definition in file backports-optional.hpp.