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  1. #include <iostream>
  2. #include <tuple>
  3. #include <functional>
  4.  
  5. namespace helper
  6. {
  7.     template <std::size_t... Ts>
  8.     struct index {};
  9.  
  10.     template <std::size_t N, std::size_t... Ts>
  11.     struct gen_seq : gen_seq<N - 1, N - 1, Ts...> {};
  12.  
  13.     template <std::size_t... Ts>
  14.     struct gen_seq<0, Ts...> : index<Ts...> {};
  15. }
  16.  
  17. template <typename... Ts>
  18. class Action_impl
  19. {
  20.     private:
  21.         std::function<void (Ts...)> f;
  22.         std::tuple<Ts...> args;
  23.     public:
  24.         template <typename F>
  25.         Action_impl(F&& func, Ts&&... args)
  26.             : f(std::forward<F>(func)),
  27.               args(std::make_tuple(std::forward<Ts>(args)...))
  28.         {}
  29.  
  30.         template <typename... Args, std::size_t... Is>
  31.         void func(std::tuple<Args...>& tup, helper::index<Is...>)
  32.         {
  33.             f(std::get<Is>(tup)...);
  34.         }
  35.  
  36.         template <typename... Args>
  37.         void func(std::tuple<Args...>& tup)
  38.         {
  39.             func(tup, helper::gen_seq<sizeof...(Args)>{});
  40.         }
  41.  
  42.         void act()
  43.         {
  44.             func(args);
  45.         }
  46. };
  47.  
  48. template <typename F, typename... Args>
  49. Action_impl<Args...> make_action(F&& f, Args&&... args)
  50. {
  51.     return Action_impl<Args...>(std::forward<F>(f), std::forward<Args>(args)...);
  52. }
  53.  
  54. int main()
  55. {
  56.     auto add = make_action([] (int a, int b) { std::cout << a+b; }, 2, 3);
  57.  
  58.     add.act();
  59. }
Success #stdin #stdout 0s 3028KB
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https://ideone.com/Nj6rGb
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
secret

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