2026-05-16 (3UE*2): Exercise Polymorphic Types
==============================================

* Based on the demo in :doc:`2026-05-11`, rearrange the ``PMWPin``
  side of ``Logic`` in a way that:

  * ``PWMPin`` constitutes an *interface*
  * The original ``PWMPin`` *concrete implementation* is renamed to
    ``LinuxSysfsPWMPin``
  * ``LinuxSysfsPWMPin`` *implements* the ``PWMPin`` interface
  * ``Logic`` *uses* the interface, ``PWMPin``

* Modify ``main.cpp`` in a way that the "real" hardware
  implementations ``LinuxSysfsPWMPin`` and ``LinuxHWMONSensor`` are
  not instantiated. 

  Rather, instantiate ``MockSensor`` and ``StdoutPWMPin``, and pass
  these to ``Logic``. When everything is well, you should see whatever
  you wrote in your ``StdoutPWMPin`` implementation.

.. plantuml::

   @startuml

   interface Sensor {
     + double get_temperature()
   }

   interface PWMPin {
     + void set_duty_cycle(uint64_t)
     + void set_period(uint64_t)
   }

   class LinuxSysfsPWMPin {}
   PWMPin <|.. LinuxSysfsPWMPin

   class StdoutPWMPin {}
   PWMPin <|.. StdoutPWMPin

   note bottom of StdoutPWMPin: writes new period/duty_cycle to std::cout

   class Logic
   {
     + void loop()
   }

   Logic -l-> Sensor
   Logic -r-> PWMPin

   @enduml