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From: hoey@ai.etl.army.mil (Dan Hoey)
Newsgroups: comp.lang.lisp
Subject: Re: Are "destructive" functions really destructive?
Message-ID: <372@ai.etl.army.mil>
Date: 29 Nov 89 20:50:30 GMT
References: <20991@mimsy.umd.edu> <1989Nov29.173139.26165@Neon.Stanford.EDU> <1989Nov29.114923.1843@hellgate.utah.edu>
Reply-To: hoey@ai.etl.army.mil (Dan Hoey)
Organization: Naval Research Lab, Washington, DC
Lines: 22

In article <1989Nov29.114923.1843@hellgate.utah.edu> moore%cdr.utah.edu@cs.utah.edu (Tim Moore) writes:
...
>If delete's behavior really bothers you, you can construct a deletef
>macro like:
>
>(defmacro deletef (item place)
>  `(setf ,place (delete ,item ,place)))
>
>Obviously this isn't completely equivalent to delete; caveat emptor

Perhaps something more like

(defmacro deletef (item place &rest delete-options &aux (itemv (gensym)))
  (multiple-value-bind (vars vals store store-form access-form)
      (get-setf-method place)
    `(let* ((,itemv ,item)
            ,.(mapcar #'list vars vals)
            (,(car store) (delete ,itemv ,access-form ,@delete-options)))
       ,store-form
       ,(car store))))

Dan