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  1. #include <cstddef>
  2. #include <functional>
  3. #include <utility>
  4. #include <type_traits>
  5.  
  6. template <typename C, std::size_t N>
  7. struct NaryDispatch
  8. {
  9.     template <typename T, std::size_t K, typename ...Args>
  10.     struct function_maker
  11.     {
  12.         using type = typename function_maker<T, K - 1, T, Args...>::type;
  13.     };
  14.  
  15.     template <typename T, typename ...Args>
  16.     struct function_maker<T, 0, Args...>
  17.     {
  18.         using type = std::function<void(Args...)>;
  19.     };
  20.  
  21.     using f_type = typename function_maker<C &, N>::type;
  22.  
  23.     template <typename F>
  24.     NaryDispatch(F && f) : fn_(std::forward<F>(f)) {}
  25.  
  26.     template <typename ...Args,
  27.               typename = typename std::enable_if<sizeof...(Args) == N>::type>
  28.     void run(Args &&... args)
  29.     {
  30.         fn_(std::forward<Args>(args)...);
  31.     }
  32.  
  33.     f_type fn_;
  34. };
  35.  
  36.  
  37. #include <iostream>
  38.  
  39. void print(const char * msg, int a, int b, int c)
  40. {
  41.    std::cout << msg << ": [" << a << ", " << b << ", " << c << "]\n";
  42. }
  43.  
  44. int main()
  45. {
  46.     int x = 1, y = 2, z = 3;
  47.  
  48.     print("Before", x, y, z);
  49.  
  50.     NaryDispatch<int, 3> d([](int & a, int & b, int & c){ print("During", a++, b++, c++); });
  51.     d.run(x, y, z);
  52.  
  53.     print("After", x, y, z);
  54. }
  55.  
Success #stdin #stdout 0s 3472KB
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stdin
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Standard input is empty
stdout
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Before: [1, 2, 3]
During: [1, 2, 3]
After: [2, 3, 4]
https://ideone.com/JJLDUM
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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