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  1. #include <iostream>
  2. #include <tuple>
  3. #include <type_traits>
  4.  
  5. template <typename ...Ts>
  6. void f(const Ts& ...args) {
  7.     int dummy[] = {0, ((std::cout << args << " "), 0)...};
  8.     static_cast<void>(dummy); // Avoid warning
  9. }
  10.  
  11.  
  12. namespace detail
  13. {
  14.  
  15.     template <typename T>
  16.     decltype(auto) call_a_b(std::integral_constant<std::size_t, 0u>, const T& arg) {return arg.a();}
  17.  
  18.     template <typename T>
  19.     decltype(auto) call_a_b(std::integral_constant<std::size_t, 1u>, const T& arg) {return arg.b();}
  20.  
  21.     template <std::size_t... Is, typename Tuple>
  22.     void call_f_a_b(std::index_sequence<Is...>, const Tuple& tuple)
  23.     {
  24.         f(call_a_b(std::integral_constant<std::size_t, Is % 2>{}, std::get<Is / 2>(tuple))...);
  25.     }
  26.  
  27. }
  28.  
  29. template <typename...Ts>
  30. void g(const Ts&... args)
  31. {
  32.     return detail::call_f_a_b(std::make_index_sequence<2 * sizeof...(Ts)>{}, std::tie(args...));
  33.     // call f(arg0.a(), arg0.b(), arg1.a(), arg1.b(), ...)
  34. }
  35.  
  36. struct S {
  37.     int a() const { return 42; }
  38.     float b() const { return 4.2f; }
  39. };
  40.  
  41. int main()
  42. {
  43.     g(S());
  44. }
  45.  
  46.  
Success #stdin #stdout 0s 3140KB
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Standard input is empty
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42 4.2
https://ideone.com/VV0nno
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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