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  1. #include <array>
  2. #include <iostream>
  3. #include <cstddef>
  4. #include <cstdint>
  5.  
  6. //	This template will be instantiated repeatedly with VItems list
  7. //	populated with new items.
  8. template<typename TItem,  TItem... VItems> class
  9. t_PackImpl
  10. {
  11. 	//	This template will be selected for second and all other blocks.
  12. 	public: template<TItem... VInnerItems> using
  13. 	t_Pack = t_PackImpl
  14. 	<
  15. 		TItem
  16. 	//	add all previous items
  17. 	,	VItems...
  18. 	//	add item holding amount of items in new block
  19. 	,	TItem{static_cast<TItem>(sizeof...(VInnerItems))}
  20. 	//	add new block items
  21. 	,	VInnerItems...
  22. 	>;
  23.  
  24. 	//	This method will be called on the last instantiated
  25. 	//	template with VItems containing all the items.
  26. 	//	Returns array containing all the items with extra 0 item at the end.
  27. 	public: static constexpr auto
  28. 	to_array(void) -> ::std::array<TItem, sizeof...(VItems) + ::std::size_t{1}>
  29. 	{
  30. 		return {VItems..., TItem{}};
  31. 	}
  32. };
  33.  
  34. //	This template will be instantiated just once.
  35. //	Starts t_PackImpl instantiation chain.
  36. template<typename TItem> class
  37. t_BeginPack
  38. {
  39. 	//	This template will be selected for first block.
  40. 	public: template<TItem... VInnerItems> using
  41. 	t_Pack = t_PackImpl
  42. 	<
  43. 		TItem
  44. 	//	add item holding amount of items in new block
  45. 	,	TItem{static_cast<TItem>(sizeof...(VInnerItems))}
  46. 	//	add new block items
  47. 	,	VInnerItems...
  48. 	>;
  49. };
  50.  
  51. int main()
  52. {
  53. 	{
  54. 		constexpr auto items
  55. 		{
  56. 			t_BeginPack<::std::uint8_t>::t_Pack<42>::to_array()
  57. 		};
  58. 		for(auto const & item: items)
  59. 		{
  60. 			::std::cout << static_cast<::std::uint32_t>(item) << ::std::endl;
  61. 		}
  62. 	}
  63. 	::std::cout << "----------------" << ::std::endl;
  64. 	{
  65. 		constexpr auto items
  66. 		{
  67. 			t_BeginPack<::std::uint8_t>::t_Pack<0, 1, 2>::to_array()
  68. 		};
  69. 		for(auto const & item: items)
  70. 		{
  71. 			::std::cout << static_cast<::std::uint32_t>(item) << ::std::endl;
  72. 		}
  73. 	}
  74. 	::std::cout << "----------------" << ::std::endl;
  75. 	{
  76. 		constexpr auto items
  77. 		{
  78. 			t_BeginPack<::std::uint8_t>::
  79. 				t_Pack<0, 1, 2>::
  80. 				t_Pack<0, 1>::
  81. 				t_Pack<0, 1, 2, 3, 4, 5>::to_array()
  82. 		};
  83. 		for(auto const & item: items)
  84. 		{
  85. 			::std::cout << static_cast<::std::uint32_t>(item) << ::std::endl;
  86. 		}
  87. 	}
  88. 	return(0);
  89. }
  90.  
Success #stdin #stdout 0s 16056KB
comments (?)
stdin
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Standard input is empty
stdout
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1
42
0
----------------
3
0
1
2
0
----------------
3
0
1
2
2
0
1
6
0
1
2
3
4
5
0
https://ideone.com/lYzea1
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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