[cl-serializer-devel] (no subject)

[Andrew Philpot]

Date:    Thu, 13 Aug 2009 13:43:14 +0200
From:    Pascal Costanza <pc at p-cos.net>
To:      Andrew Philpot <philpot at ISI.EDU>
Subject: Re: CLOSER-MOP:SLOT-DEFINITION-ALLOCATION


On 12 Aug 2009, at 23:26, Andrew Philpot wrote:

> [also redirected to cl-serializer-devel]

[I didn't see that in the headers, so I don't know how to respond to 
cl-serializer-devel.]

> CL-SERIALIZER calls CLOSER-MOP:SLOT-DEFINITION-ALLOCATION on a class
> object that might be a STANDARD-CLASS and might not (e.g. a
> STRUCTURE-CLASS).  In SBCL, both of these are defined, but in Allegro
> 8.1, the only method on this generic function is on STANDARD-CLASS.
> Does it make sense to (1) extend the GF for the Allegro case in
> CLOSER-MOP to return NIL or some other sensible value (2) embed an
> appropriate check in the CL-SERIALIZER client code or (3) do you have
> another suggestion?

Thanks a lot for asking.

The CLOS MOP specification specifies methods for these accessor 
functions only for the CLOS metaobject classes, but explicitly not for 
structure classes (or other entities). Since Common Lisp 
implementations are allowed to do whatever they want for structure 
classes, I cannot ensure that whatever I want to define for structure 
classes in Closer to MOP will actually be portable (now and in the 
future). So I prefer not to touch structure classes.

I think the best option for you is to provide your own layer on top of 
the CLOS MOP that abstracts away from these differences. So define 
something like:

(defgeneric cl-serializer:slot-definition-allocation (...)
   (:method (... closer-mop:standard-slot-definition ...)
    (closer-mop:slot-definition-allocation ...))
   (:method (... structure-slot ...) ...))


I hope this helps,
Pascal

- -- 
Pascal Costanza, mailto:pc at p-cos.net, http://p-cos.net
Vrije Universiteit Brussel
Software Languages Lab
Pleinlaan 2, B-1050 Brussel, Belgium