[Fwd: Re: [cells-devel] CVS: Missing file variables.lisp ?!]

[Ken Tilton]

Attila Lendvai wrote:

>> After someone asked on c.l.l I spent a day on making a defparameter a
>> Cell. The test worked but then I think I tried it live and it failed and
>> I decided I better get back to work on Algebra (but apparently never
>> took it out of my LPR).
>
>
> while making a clet in computed-class i've also played with the idea
> of a cell in a defparameter, but i couldn't come up with anything
> without symbol-macrolet. i think that can't be done transparently with
> standard common lisp constructs.

I just added variables.lisp to CVS just so folks can find it, and at the 
same time modified cells.lpr /not/ to show it.

 From there, the macro:

(defmacro def-c-variable (v-name cell &key ephemeral owning unchanged-if)
  (declare (ignore unchanged-if))
  (let ((c 'whathef)) ;;(gensym)))
    `(progn
       (eval-when (:compile-toplevel :load-toplevel)
         (define-symbol-macro ,v-name (c-variable-accessor ',v-name))
         (setf (md-slot-cell-type 'null ',v-name) (when ,ephemeral 
:ephemeral))
         (when ,owning
           (setf (md-slot-owning 'null ',v-name) t)))
       (eval-when (:load-toplevel)
         (let ((,c ,cell))
           (md-install-cell nil ',v-name ,c)
           (awaken-cell ,c)))
       ',v-name)))

So this:
    (def-c-variable *kenny* (c-in nil))

Expands to this:
(progn
  (eval-when (:compile-toplevel :load-toplevel)
    (define-symbol-macro *kenny* (c-variable-accessor '*kenny*))
    (setf (md-slot-cell-type 'null '*kenny*) (when nil :ephemeral))
    (when nil (setf (md-slot-owning 'null '*kenny*) t)))
  (eval-when (:load-toplevel)
    (let ((whathef (c-in nil)))
      (md-install-cell nil '*kenny* whathef) (awaken-cell whathef))) 
'*kenny*)

Obviously still experimental. :)

ken



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