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  1. #include <type_traits>
  2.  
  3. template <typename T>
  4. class smart_ptr
  5. {
  6. public:
  7.     // ... removed other member functions for simplicity
  8.     T* get() const { return ptr; }
  9.  
  10. private:
  11.     template <typename... Args>
  12.     struct opparen_constret
  13.     {
  14.         typedef decltype(std::declval<T const>()(std::declval<Args>()...)) type;
  15.     };
  16.  
  17.     template <typename... Args>
  18.     struct opparen_ret
  19.     {
  20.         typedef decltype(std::declval<T>()(std::declval<Args>()...)) type;
  21.     };
  22.  
  23. public:
  24.     template <typename... Args>
  25.     typename opparen_constret<Args...>::type operator ()(Args... args) const
  26.     {
  27.         return (*get())(args...);
  28.     }
  29.  
  30.     template <typename... Args>
  31.     typename opparen_ret<Args...>::type operator ()(Args... args)
  32.     {
  33.         return (*get())(args...);
  34.     }
  35.  
  36. private:
  37.     T* ptr;
  38. };
  39.  
  40. struct Test {};
  41.  
  42. int main()
  43. {
  44.     smart_ptr<Test> p;
  45.     return 0;
  46. }
Success #stdin #stdout 0s 2880KB
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https://ideone.com/uiW9rI
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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