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  1. #if __cplusplus < 201103L
  2. #	error "C++ version too old"
  3. #endif
  4.  
  5. #ifdef __AVR
  6. namespace std {
  7. 	using size_t = unsigned int;
  8. 	template <typename T, size_t N>
  9. 	class array {
  10. 		public:
  11. 			T data [N];
  12. 			static constexpr size_t size () { return N; }
  13. 			constexpr const T& operator [] (size_t I) const { return data [I]; }
  14. 			T& operator [] (size_t I) { return data [I]; }
  15. 	};
  16. }
  17. #else
  18. 	#include <utility>
  19. 	#include <array>
  20. 	#include <cstddef>
  21. #endif
  22.  
  23. #if (__cplusplus < 201402L) || defined(__AVR)
  24. 	template <std::size_t... I>
  25. 	struct index_sequence {};
  26.  
  27. 	template<class S1, class S2> struct concat;
  28.  
  29. 	template<std::size_t... I1, std::size_t... I2>
  30. 	struct concat<index_sequence<I1...>, index_sequence<I2...>> {
  31. 		using Type = index_sequence<I1..., (sizeof...(I1)+I2)...>;
  32. 	};
  33.  
  34. 	template<std::size_t N>
  35. 	struct gen_seq {
  36. 		using Type = typename concat<typename gen_seq<N/2>::Type, typename gen_seq<N - N/2>::Type>::Type;
  37. 	};
  38.  
  39. 	template<> struct gen_seq<0> { using Type = index_sequence<>; };
  40. 	template<> struct gen_seq<1> { using Type = index_sequence<0>; };
  41.  
  42. 	template <std::size_t N>
  43. 	using make_index_sequence = typename gen_seq<N>::Type;
  44. #else
  45. 	using std::make_index_sequence;
  46. 	using std::index_sequence;
  47. #endif
  48.  
  49.  
  50. template <typename F, std::size_t... I>
  51. constexpr auto generate (F&& f, index_sequence<I...>) -> std::array<decltype(static_cast<F&&> (f) (0)), sizeof...(I)> {
  52. 	return {{ static_cast<F&&> (f) (I) ... }};
  53. }
  54.  
  55. template <std::size_t S, typename F>
  56. constexpr auto generate (F&& f) -> std::array<decltype(static_cast<F&&> (f) (0)), S> {
  57. 	return generate (static_cast<F&&> (f), make_index_sequence<S> {});
  58. }
  59.  
  60. constexpr int myLutCalc (std::size_t index) {
  61. 	return index * 2;
  62. }
  63.  
  64. constexpr auto myLUT = generate<10> (myLutCalc);
  65.  
  66. int main() {
  67. 	for (std::size_t i = 0; i < myLUT.size (); ++i) {
  68. 		volatile int x = myLUT [i];
  69. 	}
  70. 	return 0;
  71. }
Success #stdin #stdout 0s 15232KB
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https://ideone.com/woWjAl
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
secret

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