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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. template<class FUNC>
  5. class IndexFunctor
  6. {
  7. public:
  8.     typedef FUNC FUNC_T;
  9.  
  10. 	explicit IndexFunctor(const FUNC_T& func) : func(func), index(0) {}
  11.  
  12. private:
  13.     FUNC_T func;
  14. 	int index;
  15.  
  16.     public:
  17. 	template<typename... Args> 
  18. 	auto operator ()(Args&&... args) 
  19. 	-> decltype(func(std::forward<Args>(args)..., index++)) //get return type
  20. 	{
  21. 		return func(std::forward<Args>(args)..., index++);
  22. 	}
  23.  
  24. 	const FUNC_T& GetFunctor() const
  25. 	{
  26. 		return func;
  27. 	}
  28.  
  29. 	int GetIndex() const
  30. 	{
  31. 		return index;
  32. 	}
  33.  
  34. 	void SetIndex(int index)
  35. 	{
  36. 		this->index = index;
  37. 	}
  38.  
  39. };
  40.  
  41. template<class FUNC>
  42. IndexFunctor<FUNC> with_index(const FUNC& func)
  43. {
  44. 	return IndexFunctor<FUNC>(func);
  45. }
  46.  
  47. int main()
  48. {
  49.     auto f = with_index([](int a, int index){ return a * index; });
  50.     int a = f(5);
  51.     cout << a << endl;
  52. }
  53.  
Success #stdin #stdout 0s 3340KB
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https://ideone.com/23Ntoz
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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