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  1. #include <iostream>
  2.  
  3. //A functor to store the input functions and call them
  4. template <typename LEFT, typename RIGHT>
  5. struct combine_functions {
  6. private:
  7.   LEFT left;
  8.   RIGHT right;
  9. public:
  10.   combine_functions(const LEFT &left, const RIGHT &right)
  11.    : left(left), right(right) {}
  12.  
  13.   template <typename ...ARGS>
  14.   auto operator()(ARGS&... args) const
  15.   -> decltype(left(args...), static_cast<void>(right(args...)))
  16.   {
  17.     left(args...);
  18.     right(args...);
  19.   }
  20.  
  21. };
  22.  
  23. //I should probably have an enable if that checks the arguments 
  24. //are function pointers or functors
  25. template <typename LEFT, typename RIGHT>
  26. combine_functions<
  27.   std::decay_t<LEFT>,
  28.   std::decay_t<RIGHT>
  29. >
  30. concat(
  31.   const LEFT &left,
  32.   const RIGHT &right
  33. ) {
  34.   return {left, right};
  35. }
  36.  
  37. int main()
  38. {
  39.     concat([](const auto& t) {std::cout << t;},
  40.            [](const auto& t) {std::cerr << t;})
  41.            ("Hello world");
  42. }
Success #stdin #stdout #stderr 0s 16064KB
comments (?)
stdin 
Standard input is empty
stdout 
Hello world
stderr 
Hello world
https://ideone.com/2zAQSt
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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