[pro] macros expanding to defclass + some mop code

[Sam Steingold]

On Mon, Dec 27, 2010 at 2:02 AM, Pascal Costanza <pc at p-cos.net> wrote:
> On 27 Dec 2010, at 04:37, Sam Steingold wrote:
>> I want to write a macro which would expand to a defclass + some code
>> which uses the resulting class object using mop.
>> e.g. (untested),
>> (defmacro deffoo (class slots)
>>  `(progn
>>     (defclass ,class () ,slots)
>>     (defun foo (x)
>>       (list
>>         ,@(mapcar (lambda (ds)
>>                     `(,(car (slot-definition-readers ds)) x))
>>                   (class-direct-slots (find-class class)))))))
>>
>> which should expand
>> (deffoo bar ((a :reader bar-a) (b :reader bar-b)))
>> to something like this:
>> (progn
>>  (defclass bar () ((a :reader bar-a) (b :reader bar-b)))
>>  (defun foo (x) (list (bar-a x) (bar-b x))))
>>
>> Alas, CLASS is not defined at read time when
>>                (class-direct-slots (find-class class))
>> and
>>                (slot-definition-readers ds)
>> want to be evaluated.
>>
>> So, how do I do this?
>
> Since a class may be redefined at runtime, you want to use the MOP at runtime anyway.

no, these classes will not change at run time (they are actually structs);
and even if they will, I will be using deffoo for that.

> If you are really sure that the class doesn't change at runtime,

I am.

> you can alternatively wrap the defclass form into an (eval-when (:compile-toplevel :load-toplevel :execute) ...)

nope. my macro calls MOP functions at macroexpansion time, so this
eval-when will not help me.
I wonder if the deprecated #, will help me.

> You could of course also decide to parse the slot definition forms yourself.
I am too lazy for that :-(

-- 
Sam Steingold <http://sds.podval.org>