64 lines
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64 lines
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<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN">
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<!Converted with LaTeX2HTML 0.6.5 (Tue Nov 15 1994) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds >
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<TITLE>28.1.10.2. Initializing Newly Added Local Slots</TITLE>
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<BODY>
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<meta name="description" value=" Initializing Newly Added Local Slots">
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<meta name="keywords" value="clm">
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<meta name="resource-type" value="document">
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<meta name="distribution" value="global">
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<P>
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<b>Common Lisp the Language, 2nd Edition</b>
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<BR> <HR><A NAME=tex2html5433 HREF="node303.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html5431 HREF="node300.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html5425 HREF="node301.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html5435 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html5436 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html5434 HREF="node303.html"> Customizing Class Redefinition</A>
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<B>Up:</B> <A NAME=tex2html5432 HREF="node300.html"> Redefining Classes</A>
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<B> Previous:</B> <A NAME=tex2html5426 HREF="node301.html"> Modifying the Structure </A>
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<HR> <P>
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<H3><A NAME=SECTION0032110200000000000000>28.1.10.2. Initializing Newly Added Local Slots</A></H3>
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<P>
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<img align=bottom alt="change_begin" src="gif/change_begin.gif"><br>
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The second step initializes the newly added local slots and performs
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any other user-defined actions. This step is implemented by the generic
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function <tt>update-instance-for-redefined-class</tt>, which is called after
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completion of the first step of modifying the structure of the
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instance.
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<P>
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The generic function <tt>update-instance-for-redefined-class</tt> takes
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four required arguments: the instance being updated after it has
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undergone the first step, a list of the names of local slots that were
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added, a list of the names of local slots that were discarded, and a
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property list containing the slot names and values of slots that were
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discarded and had values. Included among the discarded slots are
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slots that were local in the old class and that are shared in the new
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class.
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<P>
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The generic function <tt>update-instance-for-redefined-class</tt> also
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takes any number of initialization arguments. When it is called by
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the system to update an instance whose class has been redefined, no
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initialization arguments are provided.
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<P>
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There is a system-supplied primary method for the generic function
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<tt>update-instance-for-redefined-class</tt> whose parameter specializer for
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its instance argument is the class <tt>standard-object</tt>. First this
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method checks the validity of initialization arguments and signals an
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error if an initialization argument is supplied that is not declared
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valid (see
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section <A HREF="node294.html#DeclaringtheValidityofInitializationArgumentsSECTION">28.1.9.2</A>.)
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Then it calls the generic function
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<tt>shared-initialize</tt> with the following arguments: the instance,
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the list of names of the newly added slots, and the initialization
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arguments it received.
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<br><img align=bottom alt="change_end" src="gif/change_end.gif">
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<P>
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<BR> <HR><A NAME=tex2html5433 HREF="node303.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html5431 HREF="node300.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html5425 HREF="node301.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html5435 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html5436 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html5434 HREF="node303.html"> Customizing Class Redefinition</A>
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<B>Up:</B> <A NAME=tex2html5432 HREF="node300.html"> Redefining Classes</A>
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<B> Previous:</B> <A NAME=tex2html5426 HREF="node301.html"> Modifying the Structure </A>
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<HR> <P>
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<HR>
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<P><ADDRESS>
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AI.Repository@cs.cmu.edu
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</ADDRESS>
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</BODY>
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