| [/ |
| Boost.Optional |
| |
| Copyright (c) 2003-2007 Fernando Luis Cacciola Carballal |
| Copyright (c) 2015 Andrzej Krzemienski |
| |
| 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) |
| ] |
| |
| [section Header <boost/none.hpp>] |
| |
| [section Synopsis] |
| ``` |
| namespace boost { |
| |
| class none_t {/* see below */}; |
| |
| inline constexpr none_t none (/* see below */); |
| |
| } // namespace boost |
| ``` |
| |
| Class `none_t` is meant to serve as a tag for selecting appropriate overloads of from `optional`'s interface. It is an empty, trivially copyable class with disabled default constructor. |
| |
| Constant `none` is used to indicate an optional object that does not contain a value in initialization, assignment and relational operations of `optional`. |
| |
| [endsect] |
| |
| [endsect] |
