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  1. #include <cstdint>
  2. #include <iostream>
  3.  
  4. #define DEFINE_HAS_SIGNATURE(traitsName, funcName, signature)               \
  5.     template <typename U>                                                   \
  6.     class traitsName                                                        \
  7.     {                                                                       \
  8.     private:                                                                \
  9.         template<typename T, T> struct helper;                              \
  10.         template<typename T>                                                \
  11.         static std::uint8_t check(helper<signature, &funcName>*);           \
  12.         template<typename T> static std::uint16_t check(...);               \
  13.     public:                                                                 \
  14.         static                                                              \
  15.         constexpr bool value = sizeof(check<U>(0)) == sizeof(std::uint8_t); \
  16.     }
  17.  
  18. DEFINE_HAS_SIGNATURE(has_ham_const, T::ham, void (T::*)() const);
  19.  
  20.  
  21. struct foo {
  22.     void ham() {}
  23.     void ham() const {}
  24. };
  25.  
  26. struct bar {
  27.     void ham() {}
  28. };
  29.  
  30. static_assert(has_ham_const<foo>::value, "unexpected");
  31. static_assert(!has_ham_const<bar>::value, "unexpected");
  32.  
  33. int main()
  34. {
  35. 	std::cout << has_ham_const<foo>::value << std::endl; // 1
  36. 	std::cout << has_ham_const<bar>::value << std::endl; // 0
  37. }
Success #stdin #stdout 0s 3412KB
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https://ideone.com/nD6EJD
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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