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1.9 KiB
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37 lines
1.9 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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<HEAD>
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<TITLE>6.1. Logical Values</TITLE>
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<BODY>
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<meta name="description" value=" Logical Values">
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<meta name="keywords" value="clm">
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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=tex2html2386 HREF="node71.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html2384 HREF="node69.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html2378 HREF="node69.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html2388 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html2389 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html2387 HREF="node71.html"> Data Type Predicates</A>
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<B>Up:</B> <A NAME=tex2html2385 HREF="node69.html"> Predicates</A>
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<B> Previous:</B> <A NAME=tex2html2379 HREF="node69.html"> Predicates</A>
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<HR> <P>
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<H1><A NAME=SECTION001010000000000000000>6.1. Logical Values</A></H1>
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<P>
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The names <tt>nil</tt> and <tt>t</tt> are constants in Common Lisp. Although they
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are symbols like any other symbols, and appear to be treated
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as variables when evaluated, it is not permitted to modify their
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values. See <tt>defconstant</tt>.
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<P>
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<BR><b>[Constant]</b><BR>
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<tt>nil</tt><P>The value of <tt>nil</tt> is always <tt>nil</tt>. This object represents the logical
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<i>false</i> value and also the empty list. It can also be written <tt>()</tt>.
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<P>
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<BR><b>[Constant]</b><BR>
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<tt>t</tt><P>The value of <tt>t</tt> is always <tt>t</tt>.
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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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