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From: giant@lindy.Stanford.EDU (Buc Richards)
Newsgroups: comp.lang.lisp
Subject: Creating an array of structures
Keywords: Defstruct, Make-array
Message-ID: <5244@lindy.Stanford.EDU>
Date: 17 Oct 89 22:45:29 GMT
Sender: giant@lindy.Stanford.EDU (Buc Richards)
Reply-To: giant@lindy.Stanford.EDU (Buc Richards)
Organization: Stanford University
Lines: 37


When I make an array of structures, any changes to any of the elements
change all the elements.  What am I dong wrong?

Here is a simple case I ran on a NeXT and a MacII under Allegro Common
Lisp with the same results.

<cl> (defstruct cardtype
        card code)

CARDTYPE
<cl> (Setf tc (Make-array 25 :Element-type 'cardtype
        :Initial-element (make-cardtype)))

#(#s(CARDTYPE :CARD NIL :CODE NIL) #s(CARDTYPE :CARD NIL :CODE NIL) #s(CARDTYPE
:CARD NIL :CODE NIL) #s(CARDTYPE :CARD NIL :CODE NIL) #s(CARDTYPE :CARD NIL :CO
DE NIL) #s(CARDTYPE :CARD NIL :CODE NIL) #s(CARDTYPE :CARD NIL :CODE NIL) #s(CA
RD TYPE :CARD NIL :CODE NIL) #s(CARDTYPE :CARD NIL :CODE NIL) #s(CARDTYPE :CARD
 NIL :CODE NIL) ...)
<cl> (Setf (cardtype-code (Aref tc 1)) 360)

360
<cl> tc

#(#s(CARDTYPE :CARD NIL :CODE 360) #s(CARDTYPE :CARD NIL :CODE 360) #s(CARDTYPE
:CARD NIL :CODE 360) #s(CARDTYPE :CARD NIL :CODE 360) #s(CARDTYPE :CARD NIL :CO
DE 360) #s(CARDTYPE :CARD NIL :CODE 360) #s(CARDTYPE :CARD NIL :CODE 360) #s(CA
RD TYPE :CARD NIL :CODE 360) #s(CARDTYPE :CARD NIL :CODE 360) #s(CARDTYPE :CARD
NIL :CODE 360) ...)


----------------

Every element has the :code changed to 360.  Thanks for any assistance.

        Rob Richards                              @ @
        Stanford University                        -