define-attribute

(defmacro define-attribute (name &rest args)
  "Sets the creating function for an attribute."
  (flet ((symbol-as-keyword (symbol)
       (let ((name-as-string (string-upcase (string symbol))))
         (or (find-symbol name-as-string "KEYWORD")
         (intern name-as-string "KEYWORD"))))
     (arg-with-default-p (item)
       (and (listp item)
        (= (length item) 2)
        (symbolp (first item)))))
    `(defun ,name ,(loop for arg in args
            if (symbolp arg)
            collect arg into required-params
            else if (arg-with-default-p arg)
            collect arg into optional-params
            finally (return
                  (concatenate
                   'list
                   required-params
                   (when optional-params (append '(&key) optional-params))
                   '(&rest moves))))
       (loop for move in moves
      append (mapcar #'(lambda (p)
                 (append p
                     (list ,(symbol-as-keyword name)
                       ,@(if (eql args nil)
                         (list t)
                         (list (append '(list) (loop for arg in args
                                      if (arg-with-default-p arg)
                                      nconc (list (symbol-as-keyword (first arg)) (first arg))
                                      else nconc (list (symbol-as-keyword arg) arg)))))))) move)))))