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  1. #include <iostream>
  2. #include <stdint.h>
  3. #include <array>
  4.  
  5. namespace details
  6. {
  7. constexpr uint8_t bit( unsigned byte, unsigned n ) {
  8.   return (byte>>n)&1;
  9. }
  10. constexpr uint8_t even_bits(uint8_t byte) {
  11.   return bit(byte, 0) | (bit(byte, 2)<<1) | (bit(byte, 4)<<2) | (bit(byte, 6)<<3);
  12. }
  13. constexpr uint8_t odd_bits(uint8_t byte) {
  14.   return even_bits(byte/2);
  15. }
  16. template<unsigned...>struct indexes{using type=indexes;};
  17. template<unsigned Max,unsigned...Is>struct make_indexes:make_indexes<Max-1,Max-1,Is...>{};
  18. template<unsigned...Is>struct make_indexes<0,Is...>:indexes<Is...>{};
  19. template<unsigned Max>using make_indexes_t=typename make_indexes<Max>::type;
  20.  
  21. template<unsigned...Is>
  22. constexpr std::array< uint8_t, 256 > even_bit_table( indexes<Is...> ) {
  23.   return {
  24.     even_bits(Is)...
  25.   };
  26. }
  27. template<unsigned...Is>
  28. constexpr std::array< uint8_t, 256 > odd_bit_table( indexes<Is...> ) {
  29.   return {
  30.     odd_bits(Is)...
  31.   };
  32. }
  33. constexpr std::array< uint8_t, 256 > even_bit_table() {
  34.   return even_bit_table( make_indexes_t<256>{} );
  35. }
  36. constexpr std::array< uint8_t, 256 > odd_bit_table() {
  37.   return odd_bit_table( make_indexes_t<256>{} );
  38. }
  39.  
  40. static constexpr auto etable = even_bit_table();
  41. static constexpr auto otable = odd_bit_table();
  42. }
  43.  
  44. uint8_t constexpr even_bits( uint16_t in ) {
  45.   return details::etable[(uint8_t)in] | ((details::etable[(uint8_t)(in>>8)])<<4);
  46. }
  47. uint8_t constexpr odd_bits( uint16_t in ) {
  48.   return details::otable[(uint8_t)in] | ((details::otable[(uint8_t)(in>>8)])<<4);
  49. }
  50. template<class A>
  51. void print_array( A&& a ) {
  52. 	std::size_t cnt = 0;
  53. 	std::cout << "[  ";
  54. 	for (auto&& e:a) {
  55. 		if (cnt!=0)
  56. 			std::cout << ", ";
  57.  		std::cout << (int)e;
  58. 		++cnt;
  59. 		if (!(cnt%8))
  60. 			std::cout << "\n  ";
  61. 	}
  62. 	std::cout << "]\n";
  63. }
  64. void dump( uint16_t x )
  65. {
  66. 	std::cout << (int)odd_bits(x) << "\n";
  67. 	std::cout << (int)odd_bits(x<<1) << "\n";
  68. 	std::cout << (int)odd_bits(x<<2) << "\n";
  69. 	std::cout << (int)odd_bits(x<<3) << "\n";
  70. 	std::cout << (int)odd_bits(x<<4) << "\n";
  71. 	std::cout << (int)odd_bits(x<<5) << "\n";
  72. 	std::cout << (int)odd_bits(x<<6) << "\n";
  73. 	std::cout << (int)odd_bits(x<<7) << "\n";
  74. }
  75. int main() {
  76. //	print_array(otable);
  77. //	print_array(etable);
  78. 	dump(1);
  79. 	dump(1<<8);
  80. 	// your code goes here
  81. 	return 0;
  82. }
Success #stdin #stdout 0.01s 3344KB
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https://ideone.com/1WjtdA
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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