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  1. #include <vector>
  2.  
  3. template <typename T, typename U>
  4. struct is_same
  5. {
  6.     enum { value = 0 };
  7. };
  8.  
  9. template <typename T>
  10. struct is_same<T, T>
  11. {
  12.     enum { value = 1 };
  13. };
  14.  
  15. template <bool, typename>
  16. struct enable_if
  17. {};
  18.  
  19. template <typename T>
  20. struct enable_if<true, T>
  21. {
  22.     typedef T type;
  23. };
  24.  
  25. template <typename T>
  26. struct ReadOnlyIterator
  27. {
  28.     ReadOnlyIterator() {}
  29.  
  30.     template <typename Container>
  31.     ReadOnlyIterator(const Container &v, typename enable_if<is_same<T, typename Container::value_type>::value, void>::type * = 0) {}
  32.  
  33.     template <typename Container>
  34.     typename enable_if<is_same<T, typename Container::value_type>::value, ReadOnlyIterator<T>&>::type operator= (const Container &v) { return *this; }
  35. };
  36.  
  37. int main()
  38. {
  39.     ReadOnlyIterator<int> i;
  40.     std::vector<int> v;
  41.     std::vector<short> w;
  42.     i = v;
  43.     //i = w; //uncomment for error
  44.     ReadOnlyIterator<int> i2 = v;
  45.     //ReadOnlyIterator<int> j = w; //uncomment for error
  46. }
Success #stdin #stdout 0s 2848KB
comments (?)
stdin 
Standard input is empty
stdout 
Standard output is empty
https://ideone.com/k3upiR
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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