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  1. #include <string>
  2. #include <iostream>
  3. #include <type_traits>
  4.  
  5. template<typename T>
  6. class Traits
  7. {
  8.     public: enum class Dummy{nothing};
  9.     public: static Dummy const converter = Dummy::nothing;
  10. };
  11.  
  12. struct Printer
  13. {
  14.     template<typename T>
  15.     typename std::enable_if<!std::is_function<decltype(Traits<T>::converter)>::value, void>::type
  16.     operator()(T const& object)
  17.     {
  18.         std::cout << object << std::endl;
  19.     }
  20.     template<typename T>
  21.     typename std::enable_if<std::is_function<decltype(Traits<T>::converter)>::value, void>::type
  22.     operator()(T const& object)
  23.     {
  24.         std::cout << Traits<T>::converter(object) << std::endl;
  25.     }
  26. };
  27.  
  28. template<>
  29. class Traits<std::string>
  30. {
  31.     public:
  32.         static std::size_t converter(std::string const& object)
  33.         {
  34.             return object.size();
  35.         }
  36. };
  37.  
  38. int main()
  39. {
  40.     using namespace std::string_literals;
  41.  
  42.     Printer     p;
  43.  
  44.     p(5);
  45.     p("This is a C-string");
  46.     p("This is a C++String"s);  // This compiles.
  47. }
Success #stdin #stdout 0s 15240KB
comments ()
stdin
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Standard input is empty
stdout
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5
This is a C-string
19
https://ideone.com/u0rvMN
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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