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  1. #include <tuple>
  2. #include <cstring>
  3. #include <functional>
  4. #include <type_traits>
  5.  
  6. size_t hash_combiner(size_t left, size_t right) //replacable
  7. { return left^right;}
  8.  
  9. template<int index, class...types>
  10. struct hash_impl {
  11.     size_t operator()(size_t a, const std::tuple<types...>& t) const {
  12.         typedef typename std::tuple_element<index, std::tuple<types...>>::type nexttype;
  13.         hash_impl<index-1, types...> next;
  14.         size_t b = std::hash<nexttype>()(std::get<index>(t));
  15.         return next(hash_combiner(a, b), t); 
  16.     }
  17. };
  18. template<class...types>
  19. struct hash_impl<0, types...> {
  20.     size_t operator()(size_t a, const std::tuple<types...>& t) const {
  21.         typedef typename std::tuple_element<0, std::tuple<types...>>::type nexttype;
  22.         size_t b = std::hash<nexttype>()(std::get<0>(t));
  23.         return hash_combiner(a, b); 
  24.     }
  25. };
  26.  
  27. namespace std {
  28.     template<class...types>
  29.     struct hash<std::tuple<types...>> {
  30.         size_t operator()(const std::tuple<types...>& t) {
  31.             const size_t begin = std::tuple_size<std::tuple<types...>>::value-1;
  32.             return hash_impl<begin, types...>()(1, t); //1 should be some largervalue
  33.         }
  34.     };
  35. }
  36.  
  37. #include <iostream>
  38.  
  39. int main() {
  40.     typedef std::tuple<int, char, float> T;
  41.     T t(14, 'A', 3.14);
  42.     std::cout << std::hash<T>()(t);
  43.     return 0;
  44. }
Success #stdin #stdout 0s 2828KB
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https://ideone.com/fkFWl
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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