boost/variant
2
0
Fork 0
mirror of https://github.com/boostorg/variant.git synced 2026-01-19 04:42:16 +00:00
Code Issues Projects Releases Wiki Activity

Add std::hash specialization for variant (refs #49)

Browse Source
This commit is contained in:
Antony Polukhin
2019-04-01 23:45:21 +03:00
parent c80759d265
commit 31dcc43faf
4 changed files with 76 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
doc/reference/variant_fwd.xml
View File

@@ -140,6 +140,13 @@
</description>
</macro>
<macro name="BOOST_VARIANT_DO_NOT_SPECIALIZE_STD_HASH">
<purpose>
<simpara>Define this macro if you do not with to have a <code><classname>std::hash</classname></code> specialization for
<code><classname>boost::variant</classname></code>.</simpara>
</purpose>
</macro>
<macro name="BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT">
<purpose>
<simpara>Indicates

46
include/boost/variant/detail/std_hash.hpp Normal file
View File

@@ -0,0 +1,46 @@
//-----------------------------------------------------------------------------
// boost variant/detail/std_hash.hpp header file
// See http://www.boost.org for updates, documentation, and revision history.
//-----------------------------------------------------------------------------
//
// Copyright (c) 2018-2019 Antony Polukhin
//
// 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)
#ifndef BOOST_VARIANT_DETAIL_STD_HASH_HPP
#define BOOST_VARIANT_DETAIL_STD_HASH_HPP
#include <boost/config.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
# pragma once
#endif
#include <boost/variant/variant_fwd.hpp>
#include <boost/variant/detail/hash_variant.hpp>
///////////////////////////////////////////////////////////////////////////////
// macro BOOST_VARIANT_DO_NOT_SPECIALIZE_STD_HASH
//
// Define this macro if you do not with to have a std::hash specialization for
// boost::variant.
#if !defined(BOOST_VARIANT_DO_NOT_SPECIALIZE_STD_HASH) && !defined(BOOST_NO_CXX11_HDR_FUNCTIONAL)
#include <functional> // for std::hash
namespace std {
template < BOOST_VARIANT_ENUM_PARAMS(typename T) >
struct hash<boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) > > {
std::size_t operator()(const boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) >& val) const {
return ::boost::hash_value(val);
}
};
}
#endif // #if !defined(BOOST_VARIANT_DO_NOT_SPECIALIZE_STD_HASH) && !defined(BOOST_NO_CXX11_HDR_FUNCTIONAL)
#endif // BOOST_VARIANT_DETAIL_STD_HASH_HPP

1
include/boost/variant/variant.hpp
View File

@@ -32,6 +32,7 @@
#include <boost/variant/detail/over_sequence.hpp>
#include <boost/variant/detail/visitation_impl.hpp>
#include <boost/variant/detail/hash_variant.hpp>
#include <boost/variant/detail/std_hash.hpp>
#include <boost/variant/detail/move.hpp>

28
test/hash_variant_test.cpp
View File

@@ -1,16 +1,32 @@
// Copyright (c) 2011-2018
// Antony Polukhin
// Copyright (c) 2011-2019 Antony Polukhin
//
// 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)
#include "boost/core/lightweight_test.hpp"
#include "boost/config.hpp"
#include "boost/variant.hpp"
#include "boost/functional/hash/hash.hpp"
void run()
{
#if !defined(BOOST_NO_CXX11_HDR_UNORDERED_SET) && !defined(BOOST_VARIANT_DO_NOT_SPECIALIZE_STD_HASH)
#include <unordered_set>
void test_std_hash() {
std::unordered_set<boost::variant<int, bool> > us;
us.insert(1);
us.insert(true);
BOOST_TEST(us.size() == 2);
}
#else
void test_std_hash() {}
#endif
void run() {
typedef boost::variant<bool, int, unsigned int, char> variant_type;
boost::hash<variant_type> hasher;
@@ -30,9 +46,9 @@ void run()
BOOST_TEST(hasher(char_variant2) == hasher(char_variant2));
}
int main()
{
int main() {
run();
test_std_hash();
return boost::report_errors();
}