text: /*
   * Copyright (C) 2016 NAVER Corp. All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *  * Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *  * Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
   * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
   * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #pragma once
  
  #include <functional>
  #include <memory>
  #include <vector>
  
  namespace std {
  
  template<typename>
  class FunctionTraits;
  
  template<typename>
  class FunctionResult;
  
  template<typename R, typename C, typename... P>
  class FunctionTraits<R (C::*)(P...)> {
  public:
      typedef R ResultType;
  };
  
  template<typename T>
  class FunctionResult {
  public:
      FunctionResult() : m_value(0) { }
  
      template<typename C, typename F, typename... P> inline bool call(C* thisObject, F function, P&&... arguments)
      {
          T value = (thisObject->*function)(arguments...);
          return (value) ? !!(m_value = value) : false;
      }
  
      T result() const { return m_value; }
  
  private:
      T m_value;
  };
  
  template<>
  class FunctionResult<void> {
  public:
      template<typename C, typename F, typename... P> inline bool call(C* thisObject, F function, P&&... arguments)
      {
          (thisObject->*function)(arguments...);
          return false;
      }
  
      void result() const { }
  };
  
  template<typename C, typename F, typename... P> inline typename FunctionTraits<F>::ResultType propagate(std::vector<C>& items, F function, P&&... arguments)
  {
      FunctionResult<FunctionTraits<F>::ResultType> result;
      for (auto& item : items)
          if (result.call(item, function, arguments...))
              break;
      return result.result();
  }
  
  template<typename C, typename F, typename... P> inline typename FunctionTraits<F>::ResultType propagate(std::vector<std::shared_ptr<C>>& items, F function, P&&... arguments)
  {
      FunctionResult<FunctionTraits<F>::ResultType> result;
      for (auto& item : items)
          if (result.call(item.get(), function, arguments...))
              break;
      return result.result();
  }
  
  template<typename C, typename F, typename... P> inline typename FunctionTraits<F>::ResultType propagate(std::vector<std::unique_ptr<C>>& items, F function, P&&... arguments)
  {
      FunctionResult<FunctionTraits<F>::ResultType> result;
      for (auto& item : items)
          if (result.call(item.get(), function, arguments...))
              break;
      return result.result();
  }
  
  }
  