42 lines
1.0 KiB
C++
42 lines
1.0 KiB
C++
#ifndef STD_HASH_HPP
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#define STD_HASH_HPP
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#include <functional>
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// this is largely inspired by boost's hash combine as can be found in
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// "The C++ Standard Library" 2nd Edition. Nicolai M. Josuttis. 2012.
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template <typename T> void hash_combine(std::size_t &seed, const T &val)
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{
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seed ^= std::hash<T>()(val) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
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}
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template <typename T> void hash_val(std::size_t &seed, const T &val) { hash_combine(seed, val); }
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template <typename T, typename... Types>
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void hash_val(std::size_t &seed, const T &val, const Types &...args)
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{
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hash_combine(seed, val);
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hash_val(seed, args...);
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}
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template <typename... Types> std::size_t hash_val(const Types &...args)
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{
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std::size_t seed = 0;
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hash_val(seed, args...);
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return seed;
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}
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namespace std
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{
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template <typename T1, typename T2> struct hash<std::pair<T1, T2>>
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{
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size_t operator()(const std::pair<T1, T2> &pair) const
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{
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return hash_val(pair.first, pair.second);
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}
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};
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} // namespace std
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#endif // STD_HASH_HPP
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