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  1. #include <iostream>
  2. #include <tuple>
  3.  
  4. namespace
  5. {
  6. 	template<typename T>
  7. 	using identity = T;
  8.  
  9. 	template<typename T, typename... V>
  10. 	struct RAII_Set_impl
  11. 	{
  12. 		T &t;
  13. 		std::tuple<identity<V T::*>...> mop;
  14. 		std::tuple<V...> ds;
  15. 		RAII_Set_impl(T &t_, std::tuple<V T::*, V, V>... sets)
  16. 		: t(t_)
  17. 		, mop(std::get<0>(sets)...)
  18. 		, ds(std::get<2>(sets)...)
  19. 		{
  20. 			set(std::get<1>(sets)...);
  21. 		}
  22. 		~RAII_Set_impl()
  23. 		{
  24. 			unset(typename gens<sizeof...(V)>::type());
  25. 		}
  26. 		template<typename... U>
  27. 		void set(U... u)
  28. 		{
  29. 			do_set<0, U...>(u...);
  30. 		}
  31. 		template<std::size_t i, typename First, typename... Rest>
  32. 		void do_set(First first, Rest... rest)
  33. 		{
  34. 			t.*std::get<i>(mop) = first;
  35. 			do_set<i+1, Rest...>(rest...);
  36. 		}
  37. 		template<std::size_t i, typename Last>
  38. 		void do_set(Last last)
  39. 		{
  40. 			t.*std::get<i>(mop) = last;
  41. 		}
  42. 		template<std::size_t i>
  43. 		void do_set()
  44. 		{
  45. 		}
  46. 		template<std::size_t...> struct seq{};
  47. 		template<std::size_t N, std::size_t... S>
  48. 		struct gens : gens<N-1, N-1, S...> {};
  49. 		template<std::size_t... S>
  50. 		struct gens<0, S...>
  51. 		{
  52. 			using type = seq<S...>;
  53. 		};
  54. 		template<std::size_t... S>
  55. 		void unset(seq<S...>)
  56. 		{
  57. 			set(std::get<S>(ds)...);
  58. 		}
  59. 	};
  60. 	template<typename T, typename... V>
  61. 	auto RAII_Set(T &t, std::tuple<V T::*, V, V>... sets)
  62. 	-> RAII_Set_impl<T, V...>
  63. 	{
  64. 		return RAII_Set_impl<T, V...>(t, sets...);
  65. 	}
  66. }
  67.  
  68. struct Test
  69. {
  70. 	int x, y;
  71. 	double z;
  72. 	~Test()
  73. 	{
  74. 		std::cout << "x = " << x << std::endl
  75. 		          << "y = " << y << std::endl
  76. 		          << "z = " << z << std::endl;
  77. 	}
  78. } t;
  79.  
  80. int main()
  81. {
  82. 	auto raii_set_t = RAII_Set(t,
  83. 		std::make_tuple(&Test::x, 1, 2),
  84. 		std::make_tuple(&Test::y, 3, 4),
  85. 		std::make_tuple(&Test::z, 5.5, 6.6)
  86. 	);
  87. 	std::cout << "x = " << t.x << std::endl
  88. 	          << "y = " << t.y << std::endl
  89. 	          << "z = " << t.z << std::endl;
  90. 	std::cout << std::endl;
  91. }
  92.  
Success #stdin #stdout 0s 3296KB
comments (?)
stdin 
Standard input is empty
stdout 
x = 1
y = 3
z = 5.5

x = 2
y = 4
z = 6.6
https://ideone.com/vEq9cd
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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