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  1. #include <unistd.h>
  2. #include <thread>
  3. #include <chrono>
  4. #include <mutex>
  5. #include <functional>
  6. #include <iostream>
  7. #include <cmath>
  8.  
  9. template <const size_t _UniqueId, typename _Res, typename... _ArgTypes>
  10. struct fun_ptr_helper
  11. {
  12. public:
  13.     typedef std::function<_Res(_ArgTypes...)> function_type;
  14.  
  15.     static void bind(function_type&& f)
  16.     { instance().fn_.swap(f); }
  17.  
  18. 	static void bind(const function_type& f)
  19. 	{ instance().fn_=f; }
  20.  
  21. 	static _Res invoke(_ArgTypes... args)
  22. 	{ return instance().fn_(args...); }
  23.  
  24. 	typedef decltype(&fun_ptr_helper::invoke) pointer_type;
  25. 	static pointer_type ptr()
  26. 	{ return &invoke; }
  27.  
  28. private:
  29. 	static fun_ptr_helper& instance()
  30. 	{
  31. 		static fun_ptr_helper inst_;
  32. 		return inst_;
  33. 	}
  34.  
  35. 	fun_ptr_helper() {}
  36.  
  37. 	function_type fn_;
  38. };
  39.  
  40. template <const size_t _UniqueId, typename _Res, typename... _ArgTypes>
  41. typename fun_ptr_helper<_UniqueId, _Res, _ArgTypes...>::pointer_type
  42. get_fn_ptr(const std::function<_Res(_ArgTypes...)>& f)
  43. {
  44. 	fun_ptr_helper<_UniqueId, _Res, _ArgTypes...>::bind(f);
  45. 	return fun_ptr_helper<_UniqueId, _Res, _ArgTypes...>::ptr();
  46. }
  47.  
  48. template<typename T>
  49. std::function<typename std::enable_if<std::is_function<T>::value, T>::type>
  50. make_function(T *t)
  51. {
  52. 	return {t};
  53. }
  54.  
  55. int main()
  56. {
  57.     std::cout << (void*)get_fn_ptr<0>(make_function(::sin))<<std::endl;
  58.     return 0;
  59. }
Success #stdin #stdout 0s 3340KB
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0x8048b50
https://ideone.com/fNw61k
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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