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  1. #include <iostream>
  2. #include <algorithm>
  3. using namespace std;
  4.  
  5. template< typename Base, typename... T >
  6. struct Comparer
  7. {
  8. 	template< T Base::* ... ptr >
  9. 	struct Members 
  10. 	{
  11. 		static bool compare( Base const& lhs, Base const& rhs )
  12. 		{
  13. 			bool arr[]{ ( lhs.*ptr == rhs.*ptr )... };
  14. 			return all_of( begin(arr), end(arr), [](bool b){return b;} );
  15. 		}
  16. 	};
  17. };
  18.  
  19. template< typename T > struct get_type;
  20. template< typename Type, typename Class > 
  21. struct get_type<Type Class::*>
  22. {
  23. 	using type = Type;
  24. 	using class_type = Class;
  25. };
  26.  
  27. template<typename...> struct type_list;
  28.  
  29. template<typename ... Args>
  30. type_list<Args...> get_types( Args... );
  31.  
  32. template<typename> struct create_comparer;
  33. template< typename First, typename ... Tail >
  34. struct create_comparer<type_list<First, Tail...>> :  
  35. 	Comparer<typename get_type<First>::class_type, 
  36.              typename get_type<First>::type,
  37.              typename get_type<Tail>::type...> {};
  38.  
  39. #define CREATE_COMPARER(...) create_comparer<decltype(get_types(__VA_ARGS__))>::Members<__VA_ARGS__>
  40.  
  41. struct A
  42. {
  43. 	int a;
  44. 	char b;
  45. };
  46.  
  47. int main() 
  48. {
  49. 	A a{4, '7'}, b=a, c{5, '7'};
  50. 	cout << CREATE_COMPARER(&A::a, &A::b)::compare(a, b);
  51. 	cout << CREATE_COMPARER(&A::a, &A::b)::compare(a, c);
  52. }
Success #stdin #stdout 0s 3296KB
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https://ideone.com/F1QGCJ
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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