[elephant-devel] Call SLOT-UNBOUND instead of signaling UNBOUND-SLOT

[Ian Eslick]

Indeed!  This was handled on the elephant-unstable development branch  
by fixing some bugs in the update-instance-for-redefined-class behavior.

Darcs elephant-unstable will replace the main elephant branch in a few  
weeks when my schedule allows.  I've been keeping up with the patches  
for the most part - but unstable required significant refactoring to  
support class schemas and schema evolution so the patches often have  
to be applied manually.  The benefit, I believe, will be a much easier  
to use and more stable solution.  It also has a number of new features  
which I've documented in earlier e-mails.

In the process of refactoring I found, and wrote tests for, quite a  
few bugs that I'm amazed were not caught earlier.

Ian


On Apr 3, 2008, at 9:23 AM, kmkaplan+elephant at ded.kim-minh.com wrote:
> Leslie P. Polzer writes:
>
>>  (defclass pineapple () ()
>>    (:metaclass persistent-metaclass))
>>  (let ((fruit (make-instance 'pineapple)))
>>    (defclass pineapple ()
>>      ((tree :initform 1))
>>        (:metaclass persistent-metaclass))
>>    (slot-value fruit 'tree)))
>>
>> Will raise unbound slot hell with current code if you have
>> a lot of instances. Backends signal UNBOUND-SLOT instead
>> of calling SLOT-UNBOUND (which is the more conformant option
>> as I see it from CLHS and the MOP spec).
>>
>> This is also better "do what I mean" behaviour; normally
>> when you provide an initform for a slot you rely on never
>> having to deal with unbound slots (at least I do).
>>
>> Attached is a patch which tests this, changes the backend behaviour
>> and provides a default for SLOT-UNBOUND that uses the initform
>> to fill in the slot value.
>
> This is probably bad: you can't SLOT-MAKUNBOUND anymore.  I have not
> yet read and understood all about CLHS 4.3.6.2 but something along
> UPDATE-INSTANCE-FOR-REDEFINED-CLASS looks like what's needed.
>
> I can't test it here but the test would look like:
>
> (deftest slot-unbound
>    (progn
>      (defclass pineapple () ()
>        (:metaclass persistent-metaclass))
>      (let ((fruit (make-instance 'pineapple)))
>        (defclass pineapple ()
>          ((tree :initform 1))
>            (:metaclass persistent-metaclass))
>        (values (slot-value fruit 'tree)
>                (progn (slot-makunbound fruit 'tree)
>                  (signals-specific-condition (unbound-slot)
>                    (slot-value inst 'slot1))))))
>    1 t)
> _______________________________________________
> elephant-devel site list
> elephant-devel at common-lisp.net
> http://common-lisp.net/mailman/listinfo/elephant-devel