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  1. #include <iostream>
  2. #include <string>
  3. using namespace std;
  4.  
  5. struct T{
  6.     int a;
  7.     void b(){}
  8.     int c(int)
  9.     {
  10.         return 1;
  11.     }
  12. };
  13.  
  14. template<typename CT, CT> struct member_helper;
  15.  
  16. template<typename FT, FT(T::*mem)>
  17. struct member_helper<FT(T::*), mem> {
  18.     static string worker()
  19.     {
  20.         return "for members";
  21.     }
  22. };
  23.  
  24. template<typename Return, typename... Args, Return(T::*fun)(Args...)>
  25. struct member_helper<Return(T::*)(Args...), fun> {
  26.     static string worker()
  27.     {
  28.         return "for member functions returning non void";
  29.     }
  30. };
  31.  
  32. template<typename... Args, void(T::*fun)(Args...)>
  33. struct member_helper<void(T::*)(Args...), fun> {
  34.     static string worker()
  35.     {
  36.         return "for member functions returning void";
  37.     }
  38. };
  39.  
  40. int main() {
  41.     cout << member_helper<decltype(&T::a), &T::a>::worker() << endl;    //prints for members, ok
  42.     cout << member_helper<decltype(&T::b), &T::b>::worker() << endl;    //cannot distinguish between all of the three
  43.     cout << member_helper<decltype(&T::c), &T::c>::worker() << endl;    //cannot distinguish between member function returning non void and member
  44. }
  45.  
Success #stdin #stdout 0s 2960KB
comments (?)
stdin 
Standard input is empty
stdout 
for members
for member functions returning void
for member functions returning non void
https://ideone.com/CbclS
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
public

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