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  1. #include <functional>
  2. #include <memory>
  3. #include <iostream>
  4. #include <queue>
  5.  
  6.     template<class Sig>
  7.     struct recursive;
  8.     template<class R, class... As>
  9.     struct recursive< R(As...) > {
  10.       using base_type = std::function<R(recursive, As...)>;
  11.     private:
  12.       std::shared_ptr< base_type > base;
  13.     public:
  14.  
  15.       template<typename...Ts>
  16.       auto operator()(Ts&&... ts) const
  17.       -> typename std::result_of< base_type( recursive, Ts... ) >::type
  18.       {
  19.         return (*base)(*this, std::forward<Ts>(ts)...);
  20.       }
  21.  
  22.       recursive(recursive const&)=default;
  23.       recursive(recursive&&)=default;
  24.       recursive& operator=(recursive const&)=default;
  25.       recursive& operator=(recursive &&)=default;
  26.       recursive() = default;
  27.       template<typename L, typename=typename std::result_of< L(recursive, As...) >::type>
  28.       explicit recursive( L&& f ):
  29.         base( std::make_shared<base_type>(std::forward<L>(f)))
  30.       {}
  31.       explicit operator bool() const { return base && *base; }
  32.     };
  33.  
  34. typedef std::queue<std::function<void (void)>> my_queue;
  35.  
  36. std::function<void (int)> get_recursive_function(my_queue& queue) {
  37. 	my_queue* pqueue = &queue;
  38.     // Closure to allow self-reference
  39.     auto f = [pqueue](recursive<void(int)> self, int recurse) {
  40.         std::cout << recurse << std::endl;
  41.         if (recurse == 0)
  42.         	return;
  43.     	pqueue->push( [self,recurse](){ self(recurse-1); } );
  44.     };
  45.     return recursive<void(int)>( f );
  46. }
  47.  
  48. int main(int, char **) {
  49. 	my_queue queue;
  50.     queue.push([&](){ get_recursive_function(queue)(10); } );
  51.  
  52.     while (!queue.empty()) {
  53.         queue.front()();
  54.         queue.pop();
  55.     }
  56. }
  57.  
Success #stdin #stdout 0s 3436KB
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https://ideone.com/up98cm
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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