Re: How to describe something in Lisp?

[Ted Zlatanov]

On Thu, 5 Feb 2009 08:22:27 +0100 Johan Andersson <johan.rejeep@gmail.com> 
wrote: 

JA> For the mode I was asking about, regular p-lists are fine. But I'm planning
JA> to do another mode. In this mode I will have a general class and one
JA> subclass for each programming language, where each subclass defines what
JA> should be done in that particular language. After your description I think
JA> defclass will work best since there's inheritance involved.

You might like this, which I think is really nice because it's
self-describing and very clean.  I didn't write it :)

Ted

;;; from J.V. Toups
(defun toups-bang (sym)
  (intern (format "%s!" sym)))
(defun toups-s-cat (sym1 sym2)
  (intern (format "%s-%s" sym1 sym2)))
(defun toups-ques (sym)
  (intern (format "%s?" sym)))

(defmacro defstruquine (name &rest slots)
  (let* ((n-fields (length slots))
   (i 1)
   (out `(progn
     (defun ,(toups-bang name) ,slots
       (list ',(toups-bang name) ,@slots)) 
     (defun ,(toups-ques name) (item)
       (eq (car item) ',(toups-bang name))))))
 (loop for slot in slots do
    (setf out 
    (append out
      (list `(defun ,(toups-s-cat name slot) (item) (elt item ,i)))))
    (setf i (+ i 1)))
 (append out (list nil))))

;; Which can be used thusly:

;; (defstruquine person first-name last-name age)

;; (let ((p (person! "Edward" "Olmos" 61)))
;;   (person-first-name p) ;; is "Edward"
;;   (person-age p) ;; is 62
;;   p) ;; returns (person! "Edward" "Olmos" 61)