.. applied:: void heart_beat()

  This function will be called automatically every :macro:`__HEART_BEAT_INTERVAL__` seconds. The driver will call the function directly in the object, even if the function is being shadowed.

  The start and stop of heart beat is controlled by :efun:`set_heart_beat`. Be careful not to have objects with heart beat running all the time, as it uses a lot of driver resources. If there is an error in the heart beat routine, the heart beat will be turned off for this object and :master:`heart_beat_error` is called. If the call to the master function returns a non-zero value, the heart beat will be turned back on again.

  The function :efun:`this_player` will return this object, but only if it is living. Otherwise, :efun:`this_player` will return 0.

  .. note:: error messages will be given to the current user which will be the object itself or nobody.

  .. usage::

    This tiny object has a heart_beat that messages its owner every time it is called::

      object owner;
      void create() {
        ...
        owner=this_player();
        set_heart_beat(1);
      }
      void heart_beat() {
        tell_object(owner, "Your heart goes: BUM BUM\n");
      }

    We have to use :efun:`tell_object` because write goes to the current user and this can only be the object itself or nobody.

  :history 3.3.687 changed: made the interval time configurable at driver compile time (used to be 2 seconds fixed).

  .. seealso:: :efun:`set_heart_beat`, :efun:`call_out`, :efun:`enable_commands`, :master:`heart_beat_error`