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  1. #include <map>
  2. #include <iostream>
  3.  
  4. struct pair_wrapper
  5. {
  6.     int &first;
  7.     float& second;
  8.  
  9.     pair_wrapper* operator->() { return this; }
  10. };
  11.  
  12. struct thing {
  13.   float f[1];
  14.   typedef std::pair<int,float> key_data;
  15.  
  16.   struct iterator {
  17.     int pos;
  18.     float *f;
  19.     pair_wrapper operator*() { return pair_wrapper{pos,f[pos]}; }
  20.     pair_wrapper operator->() { return pair_wrapper{pos,f[pos]}; }
  21.   };
  22.  
  23.   iterator begin() { return {0, f}; }
  24. };
  25.  
  26. template<typename T> void test(T iter) {
  27.   (*iter).second = 1.0; std::cout << (*iter).second;
  28.  
  29.   iter->second = 2.0; std::cout << iter->second;
  30. }
  31.  
  32. int main() {
  33.   std::map<int,float> fmap; fmap[0] = 0.0;
  34.   test(fmap.begin());
  35.   std::cout << fmap[0];
  36.  
  37.   thing f;
  38.   test(f.begin());
  39.   std::cout << f.f[0];
  40. }
  41.  
Success #stdin #stdout 0s 15240KB
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https://ideone.com/qj1wFs
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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