variant/detail/std_hash.hpp

0001 //-----------------------------------------------------------------------------
0002 // boost variant/detail/std_hash.hpp header file
0003 // See http://www.boost.org for updates, documentation, and revision history.
0004 //-----------------------------------------------------------------------------
0005 //
0006 // Copyright (c) 2018-2023 Antony Polukhin
0007 //
0008 // Distributed under the Boost Software License, Version 1.0. (See
0009 // accompanying file LICENSE_1_0.txt or copy at
0010 // http://www.boost.org/LICENSE_1_0.txt)
0011
0012
0013 #ifndef BOOST_VARIANT_DETAIL_STD_HASH_HPP
0014 #define BOOST_VARIANT_DETAIL_STD_HASH_HPP
0015
0016 #include <boost/config.hpp>
0017 #ifdef BOOST_HAS_PRAGMA_ONCE
0018 # pragma once
0019 #endif
0020
0021 #include <boost/variant/variant_fwd.hpp>
0022 #include <boost/variant/detail/hash_variant.hpp>
0023
0024 ///////////////////////////////////////////////////////////////////////////////
0025 // macro BOOST_VARIANT_DO_NOT_SPECIALIZE_STD_HASH
0026 //
0027 // Define this macro if you do not wish to have a std::hash specialization for
0028 // boost::variant.
0029
0030 #if !defined(BOOST_VARIANT_DO_NOT_SPECIALIZE_STD_HASH) && !defined(BOOST_NO_CXX11_HDR_FUNCTIONAL)
0031
0032 #include <functional> // for std::hash
0033
0034 namespace std {
0035     template < BOOST_VARIANT_ENUM_PARAMS(typename T) >
0036     struct hash<boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) > > {
0037         std::size_t operator()(const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& val) const {
0038             return ::boost::hash_value(val);
0039         }
0040     };
0041 }
0042
0043 #endif // #if !defined(BOOST_VARIANT_DO_NOT_SPECIALIZE_STD_HASH) && !defined(BOOST_NO_CXX11_HDR_FUNCTIONAL)
0044
0045 #endif // BOOST_VARIANT_DETAIL_STD_HASH_HPP
0046