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  1.  
  2. #include <iostream>
  3. #include <tuple>
  4. #include <sstream>
  5. #include <string>
  6. #include <vector>
  7. #include <memory>
  8.  
  9. //FRAMEWORK - HELPER ETC
  10.  
  11.  
  12. template<int ...>
  13. struct seq {};
  14.  
  15. template<int M, int ...N>
  16. struct genseq  : genseq<M-1,M-1, N...> {};
  17.  
  18. template<int ...N>
  19. struct genseq<0,N...>
  20. {
  21.    typedef seq<N...> type;
  22. };
  23.  
  24. template<typename...args>
  25. struct tuple_maker
  26. {
  27.    template<int ...N>
  28.    std::tuple<args...> make(std::istream & stream, const seq<N...> &)
  29.    {
  30.      return std::make_tuple(args(read_arg<N>(stream))...);
  31.    }
  32.    std::vector<std::string> m_params;
  33.    std::vector<std::unique_ptr<std::stringstream>> m_streams;
  34.    template<int Index>
  35.    std::stringstream & read_arg(std::istream & stream) 
  36.    {
  37.      if ( m_params.empty() )
  38.      {
  39.         std::string line;
  40.         while ( std::getline(stream, line) ) //read all at once!
  41.         {
  42.                 m_params.push_back(line);
  43.         }
  44.      }
  45.      auto pstream = new std::stringstream(m_params.at(Index));
  46.      m_streams.push_back(std::unique_ptr<std::stringstream>(pstream));
  47.      return *pstream;
  48.    }
  49. };
  50.  
  51. //PARSE FUNCTION 
  52. template<typename... args>
  53. std::tuple<args...> parse(std::istream &stream) 
  54. {
  55.   const int N = sizeof...(args);
  56.   return tuple_maker<args...>().make(stream, typename genseq<N>::type() );
  57. }
  58.  
  59. ///TEST CODE
  60.  
  61. template<int N>
  62. struct A 
  63. {
  64.     std::string data;
  65. 	A(std::istream & stream) 
  66. 	{
  67. 		stream >> data;
  68. 	}
  69. 	friend std::ostream& operator << (std::ostream & out, A<N> const & a)
  70. 	{
  71. 		return out << "A" << N << "::data = " << a.data ;
  72. 	}
  73. };
  74. typedef A<1> A1;
  75. typedef A<2> A2;
  76. typedef A<3> A3;
  77.  
  78. int main()
  79. {
  80. 	std::stringstream ss("A1\nA2\nA3\n");
  81. 	auto tuple = parse<A1,A2,A3>(ss);
  82. 	std::cout << std::get<0>(tuple) << std::endl;
  83. 	std::cout << std::get<1>(tuple) << std::endl;
  84. 	std::cout << std::get<2>(tuple) << std::endl;
  85. }
  86.  
Success #stdin #stdout 0s 3072KB
comments (?)
stdin
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Standard input is empty
stdout
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A1::data = A1
A2::data = A2
A3::data = A3
https://ideone.com/0z0DxE
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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