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  1. #include <iostream>
  2. #include <unordered_set>
  3.  
  4. struct MyStruct
  5. {
  6.     int x, y;
  7.     double mutable z;
  8.  
  9.     MyStruct(int x, int y)
  10.         : x{ x }, y{ y }, z{ 0.0 }
  11.     {
  12.     }
  13. };
  14.  
  15. struct MyStructHash
  16. {
  17.     inline size_t operator()(MyStruct const &s) const
  18.     {
  19.         size_t ret = s.x;
  20.         ret *= 2654435761U;
  21.         return ret ^ s.y;
  22.     }
  23. };
  24.  
  25. struct MyStructEqual
  26. {
  27.     inline bool operator()(MyStruct const &s1, MyStruct const &s2) const
  28.     {
  29.         return s1.x == s2.x && s1.y == s2.y;
  30.     }
  31. };
  32.  
  33. int main()
  34. {
  35.     std::unordered_set<MyStruct, MyStructHash, MyStructEqual> set;
  36.     auto pair = set.emplace(100, 200);
  37.  
  38.     if (pair.second)
  39.         pair.first->z = 300.0;
  40.  
  41.     std::cout << set.begin()->z;
  42. }
  43.  
Success #stdin #stdout 0s 15240KB
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Standard input is empty
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300
https://ideone.com/sz9jO0
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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