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  1. #include <iostream>
  2. #include <type_traits>
  3.  
  4. template<typename TypeHead, typename... TypeTail>
  5. struct TypesList
  6. {
  7. 	typedef TypeHead head;
  8. 	typedef TypesList<TypeTail...> tail;
  9.  
  10. 	enum { Length = 1 + tail::Length };
  11. 	static const bool isLast = false;
  12.  
  13. 	template<typename QueryType>
  14. 	struct Contains
  15. 	{
  16. 		static const bool value = std::is_same<QueryType, TypeHead>::value || 
  17. 			tail::template Contains<QueryType>::value;
  18. 	};
  19. };
  20.  
  21. template<typename TypeHead>
  22. struct TypesList<TypeHead>
  23. {
  24. 	typedef TypeHead head;
  25.  
  26. 	enum { Length = 1 };
  27. 	static const bool isLast = true;
  28.  
  29. 	template<typename QueryType>
  30. 	struct Contains
  31. 	{
  32. 		static const bool value = std::is_same<QueryType, TypeHead>::value;
  33. 	};
  34. };
  35.  
  36. template<typename T>
  37. void foo(const T &arg) {
  38. 	typedef TypesList<int, float, char> AllowedTypes;
  39.  
  40. 	static_assert(AllowedTypes::Contains<T>::value, "Not allowed type: ");
  41.  
  42. 	// do some stuff here
  43. }
  44.  
  45. struct Yoba {};
  46.  
  47. int main()
  48. {
  49. 	auto num = 5;
  50. 	foo(num);
  51.  
  52. 	Yoba yoba;
  53. 	foo(yoba);
  54.  
  55. 	return 0;
  56. }
  57.  
Compilation error #stdin compilation error #stdout 0s 0KB
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stdin
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Standard input is empty
compilation info 
prog.cpp: In instantiation of ‘void foo(const T&) [with T = Yoba]’:
prog.cpp:53:10:   required from here
prog.cpp:40:2: error: static assertion failed: Not allowed type: 
  static_assert(AllowedTypes::Contains<T>::value, "Not allowed type: ");
  ^
stdout
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Standard output is empty
https://ideone.com/7vRWlH
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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