51 lines
2.9 KiB
HTML
51 lines
2.9 KiB
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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>28.1.11. Changing the Class of an Instance</TITLE>
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<meta name="description" value=" Changing the Class of an Instance">
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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=tex2html5467 HREF="node306.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html5465 HREF="node261.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html5459 HREF="node304.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html5469 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html5470 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html5468 HREF="node306.html"> Modifying the Structure </A>
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<B>Up:</B> <A NAME=tex2html5466 HREF="node261.html"> Programmer Interface Concepts</A>
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<B> Previous:</B> <A NAME=tex2html5460 HREF="node304.html"> Extensions</A>
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<HR> <P>
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<H2><A NAME=SECTION0032111000000000000000>28.1.11. Changing the Class of an Instance</A></H2>
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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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<A NAME=ChangingtheClassofanInstanceSECTION>The</A>
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function <tt>change-class</tt> can be used to change the class of an
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instance from its current class, <IMG ALIGN=BOTTOM ALT="" SRC="_24769_tex2html_wrap43627.gif">, to a
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different class, <IMG ALIGN=BOTTOM ALT="" SRC="_24769_tex2html_wrap43629.gif">; it changes the
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structure of the instance to conform to the definition of the class
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<IMG ALIGN=BOTTOM ALT="" SRC="_24769_tex2html_wrap43629.gif">.
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<P>
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Note that changing the class of an instance may cause slots to be
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added or deleted.
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<P>
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When <tt>change-class</tt> is invoked on an instance, a two-step updating
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process takes place. The first step modifies the structure of
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the instance by adding new local slots and discarding local slots that
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are not specified in the new version of the instance. The second step
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initializes the newly added local slots and performs any other
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user-defined actions. These steps are further described in the
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following two sections.
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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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<HR>
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<UL>
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<LI> <A NAME=tex2html5471 HREF="node306.html#SECTION0032111100000000000000"> Modifying the Structure of an Instance</A>
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<LI> <A NAME=tex2html5472 HREF="node307.html#SECTION0032111200000000000000"> Initializing Newly Added Local Slots</A>
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<LI> <A NAME=tex2html5473 HREF="node308.html#SECTION0032111300000000000000"> Customizing the Change of Class of an Instance</A>
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</UL>
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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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