namespace boost {
  namespace pipeline {
    class execution;
  }
}

namespace boost {
  namespace pipeline {
    template<typename Container> unspecified from(const Container &);
    template<typename Iterator> 
      unspecified from(const Iterator &, const Iterator &);
    template<typename QueueBack, typename R> 
      unspecified from(const std::function< R(QueueBack)> &);
    template<typename QueueBack, typename R> unspecified from(R(*)(QueueBack));
    template<typename T, typename Callable> unspecified from(const Callable &);
    template<typename T> unspecified from(queue< T > &);
    template<typename Function, 
             typename std::enable_if< !std::is_function< Function >::value, int >::type = 0> 
      unspecified make(const Function &);
    template<typename Function, 
             typename std::enable_if< !std::is_function< Function >::value, int >::type = 0> 
      unspecified make(Function &);
    template<typename Function, 
             typename std::enable_if< std::is_function< Function >::value, int >::type = 0> 
      unspecified make(const Function &);
    template<typename Callable, 
             typename std::enable_if<!std::is_function< Callable >::value, int >::type = 0> 
      unspecified to(const Callable &);
    template<typename Function, 
             typename std::enable_if< std::is_function< Function >::value, int >::type = 0> 
      unspecified to(const Function &);
  }
}

namespace boost {
  namespace pipeline {
    template<typename T> class queue_back;
    template<typename T> class queue_front;

    typedef sync_queue< T > queue;
  }
}

namespace boost {
  namespace pipeline {
    typedef executors::basic_thread_pool thread_pool;
  }
}

namespace boost {
  namespace pipeline {
    template<typename Input, typename Output> class segment;

    template<typename Output> class segment<terminated, Output>;
    template<typename Input> class segment<Input, terminated>;
    template<> class segment<terminated, terminated>;

    typedef void terminated;
    typedef segment< terminated, terminated > plan;
  }
}