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  1. #include<map>
  2.  
  3. class Class1
  4. {
  5. public:
  6.     Class1(int id) : id(id) {}
  7.  
  8. private:
  9.     int id;
  10.     friend struct Class1Compare;
  11.     friend struct std::less<Class1>;
  12. };
  13.  
  14. struct Class1Compare
  15. {
  16.    bool operator() (const Class1& lhs, const Class1& rhs) const
  17.    {
  18.        return lhs.id < rhs.id;
  19.    }
  20. };
  21.  
  22. namespace std
  23. {
  24.     template<> struct less<Class1>
  25.     {
  26.        bool operator() (const Class1& lhs, const Class1& rhs) const
  27.        {
  28.            return lhs.id < rhs.id;
  29.        }
  30.     };
  31. }
  32.  
  33. int main() {
  34.     std::map<Class1, int, Class1Compare> c2int;
  35.     std::map<Class1, int> c2int_2;
  36. 	return 0;
  37. }
Success #stdin #stdout 0s 15232KB
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https://ideone.com/VCfU0m
language:
C++ (gcc 8.3)
created:
5 years ago
visibility:
secret

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