Re: no-applicable-method

[Gregor.pa@Xerox.COM]

    Date: 03 May 88 13:15 PDT
    From: Dick Gabriel <RPG@SAIL.Stanford.EDU>

    These sound as if the problem is that there is no applicable method.

    My question is, where is the necessity of method lookup generic function
    invocation in the semantics of NO-APPLICABLE-METHOD? 

Well, this may be so, but I still have a problem with Jim's proposal
which is that no-applicable-method doesn't really take the appropriate
arguments for this case.  Without knowing what method the
call-next-method was called from (or at least which generic function),
it won't be possible to do anything really interesting in the no
applicable method case.

In addition, it won't be possible for users to further specialize this
case of no-applicable-method.  The only possible specializations are
function and (eql #'call-next-method).  With no-next-method, the user
can do something like:

;;;
;;; My method is a class of method that just returns nil from
;;; call-next-method if there is no next method.
;;;
(defclass my-method (standard-method)
    ())

(defmethod no-applicable-method ((gf standard-generic-function)
                                 (m my-method)
                                 &rest ignore)
  nil)

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