RE: Is there an example of a function that will

["pierce" <pierce@at-mail-server.vitro.com>]

Luke,

>I am looking for a recursive version of class-direct-subclasses that will
>return all the classes in a list.

There is not a version built into MCL since the CLOS implementation doesn't
need it.

Try the following:

(defmacro deftransitive-closure (r1 r2)
        `(defmethod ,r1 ((thing t)) (standard-transitive-closure-internal ',r2
thing nil)))

(defmethod standard-transitive-closure-internal ((r2 symbol) (thing t)
(ancestors-so-far list))
  (let (parents ancestors)
    (setf parents (funcall r2 thing))
        (setf ancestors parents)
     (loop 
       for p in (set-difference parents ancestors-so-far)
       as local-ancestors = (standard-transitive-closure-internal r2 p
`(,@ancestors-so-far ,p))  do
       (setf ancestors (union ancestors local-ancestors)))
     ancestors))

(deftransitive-closure class-effective-subclasses class-direct-subclasses) 

#| 

;;; Example

(defclass c1 () ())

(defclass c2 (c1) ())

(defclass c3 (c2) ())

(class-effective-subclasses (find-class 'c1))
|#

-Jonathan