1[/
2    Boost.Optional
3
4    Copyright (c) 2003-2007 Fernando Luis Cacciola Carballal
5    Copyright (c) 2015 Andrzej Krzemienski
6
7    Distributed under the Boost Software License, Version 1.0.
8    (See accompanying file LICENSE_1_0.txt or copy at
9    http://www.boost.org/LICENSE_1_0.txt)
10]
11
12[section Header <boost/none.hpp>]
13
14[section Synopsis]
15```
16namespace boost {
17
18class none_t {/* see below */};
19
20inline constexpr none_t none (/* see below */);
21
22} // namespace boost
23```
24
25Class `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.
26
27Constant `none` is used to indicate an optional object that does not contain a value in initialization, assignment and relational operations of `optional`.
28
29[endsect]
30
31[endsect]
32