48 lines
2.3 KiB
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48 lines
2.3 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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<HEAD>
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<TITLE>2.12. Structures</TITLE>
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<BODY>
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<meta name="description" value=" Structures">
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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=tex2html1987 HREF="node40.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html1985 HREF="node15.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html1979 HREF="node38.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html1989 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html1990 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html1988 HREF="node40.html"> Functions</A>
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<B>Up:</B> <A NAME=tex2html1986 HREF="node15.html"> Data Types</A>
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<B> Previous:</B> <A NAME=tex2html1980 HREF="node38.html"> Random-States</A>
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<HR> <P>
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<H1><A NAME=SECTION006120000000000000000>2.12. Structures</A></H1>
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<P>
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Structures are instances of user-defined data types that have
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a fixed number of named components. They are analogous to
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records in Pascal.
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Structures are declared using the <tt>defstruct</tt> construct;
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<tt>defstruct</tt> automatically defines access and constructor functions for
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the new data type.
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<P>
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Different structures may print out in different ways;
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the definition of a structure type may specify a print procedure
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to use for objects of that type (see the
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<tt>:print-function</tt> option to <tt>defstruct</tt>).
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The default notation for structures is
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<P><pre>
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#S(<i>structure-name</i>
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<i>slot-name-1</i> <i>slot-value-1</i>
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<i>slot-name-2</i> <i>slot-value-2</i>
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...)
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</pre><P>
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where <tt>#S</tt> indicates structure syntax, <i>structure-name</i> is
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the name (a symbol) of the structure type, each <i>slot-name</i> is the name
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(also a symbol) of a component, and each corresponding <i>slot-value</i>
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is the representation of the Lisp object in that slot.
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<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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