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  1. #include <iostream>
  2. #include <string>
  3. #include <tuple>
  4. #include <typeinfo>
  5.  
  6. template<std::size_t> struct int_{};
  7.  
  8. struct nil {};
  9.  
  10. template<typename T, class Tuple>
  11. struct concat_tuple_type;
  12.  
  13. template< typename T
  14.         , typename T1, typename T2, typename T3
  15.         , typename T4, typename T5 >
  16. struct concat_tuple_type< T, std::tuple<T1, T2, T3, T4, T5> >
  17. {
  18.     typedef std::tuple<T, T1, T2, T3, T4, T5>               result_type;
  19. };
  20.  
  21. template< typename T, class Tuple>
  22. typename concat_tuple_type<const T*,Tuple>::result_type concat_tuple(const T& obj, const Tuple& tuple)
  23. {
  24. 	typedef typename concat_tuple_type<const T*, Tuple>::result_type
  25. 	                                                        result_type;
  26. 	result_type result( obj, tuple);
  27. }
  28.  
  29. ////////////////////////////////////////////////////////////////////////////////
  30.  
  31. template<class Tuple>
  32. struct expression
  33. {
  34. 	Tuple expr;
  35.  
  36. 	expression(const Tuple& x)                            : expr(x) {}
  37. };
  38.  
  39. template<>
  40. struct expression<nil>
  41. {
  42. };
  43.  
  44. template<typename T, typename Tuple>
  45. expression< typename concat_tuple_type<const T*, Tuple>::result_type > operator<<(const expression<Tuple>& x, const T& obj)
  46. {
  47. 	typedef expression<typename concat_tuple_type<const T*, Tuple>::result_type>
  48. 	                                                        result_type;
  49. 	return result_type( concat_tuple(&obj, x.expr) );
  50. }
  51.  
  52. template<typename T>
  53. expression< std::tuple<const T*> > operator<<(const expression<nil>&, const T& obj)
  54. {
  55. 	return std::tuple<const T*>(&obj);
  56. }
  57.  
  58. ////////////////////////////////////////////////////////////////////////////////
  59.  
  60. template<typename Tuple, std::size_t I>
  61. void print_expression(std::ostream& os, const expression<Tuple>& x, int_<I>)
  62. {
  63. 	print_expression(os, x, int_<I-1>());
  64. 	os << ", " /*<< I << ": "*/ << *std::get<I>(x.expr);
  65. }
  66.  
  67. template<typename Tuple>
  68. void print_expression(std::ostream& os, const expression<Tuple>& x, int_<0>)
  69. {
  70. 	os /*<< "0: "*/ << *std::get<0>(x.expr);
  71. }
  72.  
  73. template<class Tuple>
  74. std::ostream& operator<<(std::ostream& os, const expression<Tuple>& x)
  75. {
  76. 	os << '(';
  77. 	print_expression( os, x, int_<std::tuple_size<Tuple>::value-1>() );
  78. 	os << ')';
  79. 	return os;
  80. }
  81.  
  82. ////////////////////////////////////////////////////////////////////////////////
  83.  
  84. int main()
  85. {
  86.     expression<nil> lhs;
  87.  
  88.     auto x = lhs << 42;
  89. 	//std::cout << typeid(x).name() << x << '\n';
  90.     //x << 42;
  91. 	operator<< <int>(x, 42);
  92.  
  93.     return 0;
  94. }
  95.  
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin
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Standard input is empty
compilation info 
prog.cpp: In function 'int main()':
prog.cpp:91:24: error: no matching function for call to 'operator<<(expression<std::tuple<const int*> >&, int)'
stdout
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Standard output is empty
https://ideone.com/k42JFg
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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