1// Copyright (C) 2022 Andrzej Krzemienski.
2//
3// Use, modification, and distribution is subject to the Boost Software
4// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
5// http://www.boost.org/LICENSE_1_0.txt)
6//
7// See http://www.boost.org/libs/optional for documentation.
8//
9// You are welcome to contact the author at:
10// akrzemi1@gmail.com
11
12#ifndef BOOST_OPTIONAL_DETAIL_OPTIONAL_HASH_AJK_20MAY2022_HPP
13#define BOOST_OPTIONAL_DETAIL_OPTIONAL_HASH_AJK_20MAY2022_HPP
14
15#include <boost/optional/optional_fwd.hpp>
16#include <boost/config.hpp>
17
18#if !defined(BOOST_OPTIONAL_CONFIG_DO_NOT_SPECIALIZE_STD_HASH) && !defined(BOOST_NO_CXX11_HDR_FUNCTIONAL)
19
20#include <functional>
21
22namespace std
23{
24 template <typename T>
25 struct hash<boost::optional<T> >
26 {
27 typedef std::size_t result_type;
28 typedef boost::optional<T> argument_type;
29
30 BOOST_CONSTEXPR result_type operator()(const argument_type& arg) const {
31 return arg ? std::hash<T>()(*arg) : result_type();
32 }
33 };
34
35 template <typename T>
36 struct hash<boost::optional<T&> >
37 {
38 typedef std::size_t result_type;
39 typedef boost::optional<T&> argument_type;
40
41 BOOST_CONSTEXPR result_type operator()(const argument_type& arg) const {
42 return arg ? std::hash<T>()(*arg) : result_type();
43 }
44 };
45}
46
47#endif // !defined(BOOST_OPTIONAL_CONFIG_DO_NOT_SPECIALIZE_STD_HASH) && !defined(BOOST_NO_CXX11_HDR_FUNCTIONAL)
48
49#endif // header guard
50