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Sprout/sprout/functional/hash/hash_combine.hpp
2015-01-10 19:13:57 +09:00

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1.6 KiB
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/*=============================================================================
Copyright (c) 2011-2015 Bolero MURAKAMI
https://github.com/bolero-MURAKAMI/Sprout
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 SPROUT_FUNCTIONAL_HASH_HASH_COMBINE_HPP
#define SPROUT_FUNCTIONAL_HASH_HASH_COMBINE_HPP
#include <sprout/config.hpp>
#include <sprout/workaround/std/cstddef.hpp>
#include <sprout/functional/hash/hash_fwd.hpp>
#include <sprout/functional/hash/to_hash.hpp>
namespace sprout {
namespace detail {
template<typename T>
inline SPROUT_CONSTEXPR std::size_t
hash_combine_impl(std::size_t seed) {
return seed;
}
template<typename T>
inline SPROUT_CONSTEXPR std::size_t
hash_combine_impl(std::size_t seed, T const& v) {
return seed ^ (sprout::to_hash(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2));
}
template<typename Head, typename... Tail>
inline SPROUT_CONSTEXPR std::size_t
hash_combine_impl(std::size_t seed, Head const& head, Tail const&... tail) {
return sprout::detail::hash_combine_impl(sprout::detail::hash_combine_impl(seed, head), tail...);
}
} // namespace detail
//
// hash_combine
//
template<typename... Args>
inline SPROUT_CONSTEXPR std::size_t
hash_combine(std::size_t seed, Args const&... args) {
return sprout::detail::hash_combine_impl(seed, args...);
}
} // namespace sprout
#endif // #ifndef SPROUT_FUNCTIONAL_HASH_HASH_COMBINE_HPP