From: james anderson
Subject: a question on method combinations
Date: Tue, 28 May 2002 20:10:46 +0000
Message-ID: <3CF3E3FE.B56AE7A8@setf.de>

i am considering how to define a method combination which threads a
datum through the method groups. something like:

(define-method-combination tripartite-fold ()
                           ((around (:around))
                            (before (:before))
                            (primary ())
                            (after (:after)))
                           (:arguments controller datum argument)
  controller datum
  (print (let ((main-form (if (or before after (rest primary))
                     `(progn ,@(when before
                               `((setf ,argument
                                    (call-method ,(first before) ,(rest before)))))
                             ,@(when primary
                               `((setf ,argument
                                    (call-method ,(first primary) ,(rest primary)))))
                             ,@(when after
                               `((setf ,argument
                                    (call-method ,(first after) ,(rest after))))))
                     `(call-method ,(first primary) ()))))
    (if around `(call-method ,(first around)
                              (,(rest around)
                               (make-method ,main-form)))
        main-form))))

this appears reasonable, but runs contrary to the allowed use of the
"arguments" forms.

what alternatives are available in the context of
define-method-combination to modify the actual arguments to the
respective methods?

...