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From: pc@flash.bellcore.com
Newsgroups: comp.lang.lisp
Subject: updating random slots in (say) defstruct
Message-ID: <18837@bellcore.bellcore.com>
Date: 12 Jan 90 22:54:28 GMT
Sender: news@bellcore.bellcore.com
Reply-To: pc@flash.bellcore.com
Organization: Bellcore - Wierd Ideas Factory
Lines: 32

Given something like:

(defstruct test
	(one)
	(two)
	(three))

one can do something like

(setq access-function 'test-one)

(setq instance (make-test :one 1 :two 2 :three 3))

(funcall access-function instance) => 1

There appears to be no Common LISP way to similarly update a random
slot.  The best one can do seems to be:

(defun update-slot (object slot value)
  (case slot
    (one (setf (test-one object) value)
    ....
  ))

Must i explicitly define my structure as say a list, to be able to
replace an arbitrary component?  Symbolics documentation on LOCFs is a
little sketchy, but perhaps i can use them?

Ideas?


Peter Clitherow