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  1. #include <type_traits>
  2.  
  3. using namespace std;
  4.  
  5. int foo(int i) {
  6. 	return i;
  7. }
  8.  
  9.  
  10. struct A
  11. {
  12.     int foo(int i) { return i; } 
  13.  
  14.     auto bar(int x) -> std::result_of<decltype(&A::foo)(A, int)>::type
  15.     {  // see: http://n...content-available-to-author-only...o.edu/2014/ref/cppreference/en/cpp/types/result_of.html
  16.     	return x;
  17.     }
  18.  
  19.     template<typename Func, typename... Args>
  20.     auto call(Func func, Args&&... args) const
  21.      ->  typename std::result_of< decltype(func)(A*, Args...)>::type
  22.  {   this->*func(args...);
  23.  
  24.  }
  25. };
  26.  
  27.  
  28.  
  29.  
  30. int main() {
  31.   	static_assert(std::is_same<decltype(foo(123)), int>::value, "");
  32.  
  33.  
  34. 	A a;
  35. 	static_assert(std::is_same<decltype(a.foo(123)), decltype(a.bar(123))>::value, "");
  36. 	static_assert(std::is_same<decltype(a.foo(123)), decltype(a.bar(123))>::value, "");
  37.  
  38.  
  39.     auto func = &A::foo;
  40. 	static_assert(std::is_same<decltype(a.foo(123)), decltype(a.call(func, 123))>::value, "");
  41. 	static_assert(std::is_same<decltype(a.foo(123)), 
  42. 	                           std::result_of<decltype(&A::foo)(A, int)>::type
  43. 	                           >::value, "");
  44.  
  45.  
  46.  
  47. 	return 0;
  48. }
Success #stdin #stdout 0s 3292KB
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https://ideone.com/QvlKAC
result_of and decltype to get the type of a member function
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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