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Re: No setf-method known for funcall


From: Pascal Bourguignon
Subject: Re: No setf-method known for funcall
Date: Thu, 18 Aug 2005 16:24:34 +0200
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/22.0.50 (gnu/linux)

address@hidden writes:

> I'd like to setf a "place" which is retrieved indirectly with a funcall
> call:
>
>
> (defstruct my
>   a b)
>
> (setq myinstance (make-my))
>
> (setf (my-a myinstance) 33)             ; this works
>
> (setq my-get-func 'my-a)
> (setf (funcall my-get-func myinstance) 33)
>     ; this doesn't work
>     ; "No setf-method known for funcall"

Write a defsetf-er for funcall!


(require 'cl)

(defmacro with-gensyms (syms &rest body)
  `(let ,(mapcar (lambda (s) `(,s ',(gensym (symbol-name s)))) syms) ,@body))

(define-setf-method funcall (fun &rest args)
  "setf-method for (funcall fun args...)"
  (let* ((vfun (eval fun))
         (vexp (get-setf-method `(,vfun ,@args))))
    (message "\n%S\n" vexp)
    (when (null vexp)
      (error "There is no defsetf for %s in %S" 
             vfun (cons fun args)))
    vexp))

(progn
  (setf x (cons :a :b))
  (setf f (function cdr))
  (setf (funcall f x) 1)
  (insert (format "--> %S\n" x))
  (dolist (f (list (function car) (function cdr)))
    (setf (funcall f x) 2))
  (insert (format "--> %S\n" x)))

--> (:a . 1)
--> (2 . 2)

-- 
"By filing this bug report you have challenged the honor of my
family. Prepare to die!"


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