"Must I do have to type `edit arduino.m`, and change the permission of `delete`?"
Yes. delete() is not appropriate for an arduino object, so if you want to be able to delete it you will need to change the implementation code for arduino.m
When you "clear" an object, you remove the variable and possibly trigger releasing the object if MATLAB detects that the reference count is now 0. There is no possibility of ending up with a variable that represents a deleted arduino object.
When you "delete" an object, the variable that held the object still exists afterwards, so the variable needs to be changed internally to "deleted arduino object", because the user is permitted to reference a variable that refers to an object that has been deleted.
a = arduino();
delete(a) %supposing it was permitted
disp(a) %Valid MATLAB. It would have to say deleted arduino object or something like that
b = arduino();
clear b
disp(b) %NOT valid MATLAB. b was cleared, the variable itself does not exist
