fork(2) download
copy 
  1. #include <iostream>
  2. #include <type_traits>
  3. #include <tuple>
  4.  
  5. namespace std {
  6.  
  7. template<typename T>
  8. struct remove_cvref {
  9.   using type = std::remove_cv_t<std::remove_reference_t<T>>;
  10. };
  11.  
  12. template<typename T>
  13. using remove_cvref_t = typename remove_cvref<T>::type;
  14.  
  15. }
  16.  
  17. template<typename T, template<typename...> typename U>
  18. struct is_derived_from_template {
  19.   template<typename... Ts>
  20.   static constexpr std::true_type f(U<Ts...>);
  21.   static constexpr std::false_type f(...);
  22.   static constexpr bool value{
  23.       decltype(f(std::declval<std::remove_cvref_t<T>>()))::value};
  24. };
  25.  
  26. template<typename... Ts>
  27. struct S : std::tuple<Ts...> {
  28.   S() = default;
  29. };
  30.  
  31. int main() {
  32.  
  33.   S<> s0;
  34.   S<int, double> s1;
  35.   S<std::tuple<>> s2;
  36.  
  37.  
  38.   std::cout << is_derived_from_template<decltype(s0), std::tuple>::value << "\n";
  39.   std::cout << is_derived_from_template<decltype(s1), std::tuple>::value << "\n";
  40.   std::cout << is_derived_from_template<decltype(s2), std::tuple>::value << "\n";
  41.  
  42.   return 0;
  43. }
Success #stdin #stdout 0s 4396KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
1
1
0
https://ideone.com/UVq3Pz
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!