text: // SJSU-Dev2: Adding system_header
  #pragma GCC system_header
  
  ///\file
  
  /******************************************************************************
  The MIT License(MIT)
  
  Embedded Template Library.
  https://github.com/ETLCPP/etl
  http://www.etlcpp.com
  
  Copyright(c) 2015 jwellbelove
  
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files(the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions :
  
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
  
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
  ******************************************************************************/
  
  #ifndef __ETL_CALLBACK__
  #define __ETL_CALLBACK__
  
  namespace etl
  {
    //***************************************************************************
    /// A callback class designed to be multiply inherited by other client classes.
    /// The class is parametrised with a callback parameter type and a unique id.
    /// The unique id allows multiple callbacks with the same parameter type.
    ///\tparam TParameter The callback parameter type.
    ///\tparam ID The unique id for this callback.
    //***************************************************************************
    template <typename TParameter, const int ID>
    class callback
    {
    private:
  
      // Creates a parameter type unique to this ID.
      template <typename T, const int I>
      struct parameter
      {
          parameter(T value)
              : value(value)
          {
          }
  
          typedef T value_type;
  
          T value;
  
      private:
  
          parameter();
      };
  
      // Specialisation for void.
      template <const int I>
      struct parameter<void, I>
      {
          typedef void value_type;
      };
  
    public:
  
      typedef parameter<TParameter, ID> type;
  
      virtual void etl_callback(type p = type()) = 0;
    };
  }
  
  #endif