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  1. #include <type_traits>
  2.  
  3. template<class T>
  4. class is_container{
  5.   typedef char (&two)[2];
  6.  
  7.   template<class U> // non-const
  8.   static auto test(typename U::iterator*, int)
  9.       -> decltype(std::declval<U>().begin(), char());
  10.  
  11.   template<class U> // const
  12.   static auto test(typename U::const_iterator*, long)
  13.       -> decltype(std::declval<U const>().begin(), char());
  14.  
  15.   template<class>
  16.   static two  test(...);
  17.  
  18. public:
  19.   static bool const value = sizeof(test<T>(0,0)) == 1;
  20. };
  21.  
  22. #include <iostream>
  23. #include <vector>
  24. #include <list>
  25. #include <set>
  26. #include <map>
  27.  
  28. int main()
  29. {
  30.     std::cout << is_container<std::vector<std::string> >::value << ' ';
  31.     std::cout << is_container<std::list<std::string> >::value << ' ';
  32.     std::cout << is_container<std::set<std::string> >::value << ' ';
  33.     std::cout << is_container<std::map<std::string, std::string> >::value << '\n';
  34. }
Success #stdin #stdout 0s 2828KB
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https://ideone.com/k4UkX
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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