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  1. #include <cstdio>	// for printf.
  2. #include <type_traits>	// for is_reference, remove_reference.
  3. #include <typeinfo>		// for typeid.
  4.  
  5. template<typename T>
  6. struct mutable_value
  7. {
  8. 	mutable_value(T val = 0) : val(val) { this->p_val = &this->val; }
  9. 	auto get_value() const -> T & { return *this->p_val; }
  10. private:
  11. 	T val;
  12. 	T *p_val;
  13. };
  14.  
  15. template<typename T>
  16. struct mutable_value_for_ref
  17. {
  18. 	typedef typename std::remove_reference<T>::type ref_dropped_t;
  19.  
  20. 	mutable_value_for_ref(T ref) : p_val{ &ref }
  21. 	{
  22. 	}
  23.  
  24. 	auto get_value() const -> ref_dropped_t &{ return *this->p_val; }
  25. private:
  26. 	ref_dropped_t *p_val;
  27. };
  28.  
  29. template<typename T>
  30. struct unko_meta
  31. {
  32. 	typedef
  33. 	typename std::conditional
  34. 	<
  35. 		std::is_reference<T>::value,
  36. 		mutable_value_for_ref<T>,
  37. 		mutable_value<T>
  38. 	>::type type;
  39. };
  40.  
  41. template<typename T>
  42. struct yakitori
  43. {
  44. 	yakitori(T t) : x(t) { }
  45.  
  46. 	auto get() const -> T & { return this->x.get_value(); }
  47.  
  48. 	typename unko_meta<T>::type x;
  49. };
  50.  
  51.  
  52. auto main() -> int
  53. {
  54. 		int i1 = 100;
  55. 		yakitori<int> const v1{ i1 };
  56. 		std::printf("--%s\n", typeid(v1.x).name());
  57. 		v1.get()++;
  58. 		std::printf("org:%d ,  yakitori:%d\n", i1, v1.get());
  59.  
  60. 		int i2 = 200;
  61. 		int const &r2 = i2;
  62. 		yakitori<int const> const v2{ r2 };
  63. 		std::printf("--%s\n", typeid(v2.x).name());
  64. 		i2++;
  65. 		std::printf("org:%d ,  yakitori:%d\n", i2, v2.get());
  66.  
  67. 		int i3 = 300;
  68. 		yakitori<int &> const v3{ i3 };
  69. 		std::printf("--%s\n", typeid(v3.x).name());
  70. 		v3.get()++;
  71. 		std::printf("org:%d ,  yakitori:%d\n", i3, v3.get());
  72.  
  73. 		int i4 = 400;
  74. 		int const &r4 = i4;
  75. 		yakitori<int const &> const v4{ r4 };
  76. 		std::printf("--%s\n", typeid(v4.x).name());
  77. 		i4++;
  78. 		std::printf("org:%d ,  yakitori:%d\n", i4, v4.get());
  79. }
  80.  
Success #stdin #stdout 0s 3340KB
comments (?)
stdin
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Standard input is empty
stdout
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--13mutable_valueIiE
org:100 ,  yakitori:101
--13mutable_valueIKiE
org:201 ,  yakitori:200
--21mutable_value_for_refIRiE
org:301 ,  yakitori:301
--21mutable_value_for_refIRKiE
org:401 ,  yakitori:401
https://ideone.com/uITHCw
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
secret

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