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  1. #include <iostream>
  2. #include <unordered_set>
  3.  
  4. struct test
  5. {
  6.     std::size_t hashCode() const
  7.     {
  8.         return 0;//insert your has routine
  9.     }
  10. };
  11. //helper class
  12. struct hashable
  13. {
  14.     hashable():value(0){}
  15.     template<typename T>
  16.     hashable(const T& t):value(t.hashCode())
  17.     {}
  18.     template<typename T>
  19.     std::size_t operator()(const T& t) const
  20.     {
  21.         return t.hashCode();
  22.     }
  23.  
  24.     std::size_t value;
  25. };
  26.  
  27.  
  28. //hash specialization of hashable
  29. namespace std {
  30.     template<>
  31.     struct hash<hashable>
  32.     {
  33.         typedef hashable argument_type;
  34.         typedef std::size_t result_type;
  35.         result_type operator()(const argument_type& b) const {
  36.             return b.value;
  37.         }
  38.     };
  39. }
  40. //helper alias so you dont have to specify the hash each time.
  41. template<typename T, typename hash = hashable>
  42. using unordered_set = std::unordered_set<T,hash>;
  43.  
  44. int main(int argc, char** argv)
  45. {
  46.     unordered_set<test> s;
  47.     test t;
  48.     std::cout<<std::hash<hashable>{}(t)<<std::endl;
  49.     return 0;
  50. }
  51.  
Success #stdin #stdout 0s 3468KB
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https://ideone.com/jhdh77
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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