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98 lines
5.5 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>2.2.1. Standard Characters</TITLE>
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<BODY>
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<meta name="description" value=" Standard Characters">
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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=tex2html1784 HREF="node23.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html1782 HREF="node21.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html1776 HREF="node21.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html1786 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html1787 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html1785 HREF="node23.html"> Line Divisions</A>
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<B>Up:</B> <A NAME=tex2html1783 HREF="node21.html"> Characters</A>
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<B> Previous:</B> <A NAME=tex2html1777 HREF="node21.html"> Characters</A>
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<HR> <P>
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<H2><A NAME=SECTION00621000000000000000>2.2.1. Standard Characters</A></H2>
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<P>
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Common Lisp defines a standard character set (subtype <tt>standard-char</tt>)
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for two purposes.
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Common Lisp programs that are <i>written</i> in the standard character set
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can be read by any Common Lisp implementation; and Common Lisp programs
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that <i>use</i> only standard characters as data objects are most likely
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to be portable. The Common Lisp character set consists of a space character
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<tt>#\Space</tt>, a newline character <tt>#\Newline</tt>, and the
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following ninety-four
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non-blank printing characters or their equivalents:
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<P><pre>
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! " # $ % & ' ( ) * + , - . / 0 1 2 3 4 5 6 7 8 9 : ; < = > ?
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@ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z [ \ ] ^ _
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` a b c d e f g h i j k l m n o p q r s t u v w x y z { | } ~
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</pre><P>
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The Common Lisp standard character set is apparently equivalent to
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the ninety-five standard ASCII printing characters plus a newline character.
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Nevertheless, Common Lisp is designed to be relatively independent of
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the ASCII character encoding. For example, the collating sequence
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is not specified except to say that digits must be properly ordered,
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the uppercase letters must be properly ordered, and
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the lowercase letters must be properly ordered
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(see <tt>char<</tt> for a precise specification).
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Other character encodings, particularly EBCDIC, should be easily accommodated
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(with a suitable mapping of printing characters).
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<P>
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Of the ninety-four non-blank printing characters, the following are
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used in only limited ways in the syntax of Common Lisp programs:
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<P><pre>
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[ ] { } ? ! ^ _ ~ $ %
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</pre>
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<img align=bottom alt="old_change_begin" src="gif/old_change_begin.gif"><br>
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All of these characters except <tt>!</tt> and <tt>_</tt> are used within
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<tt>format</tt> strings as formatting directives.
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Except for this,
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<tt>[</tt>, <tt>]</tt>, <tt>{</tt>, <tt>}</tt>,
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<tt>?</tt>, and <tt>!</tt> are not used in Common Lisp and are reserved to the user
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for syntactic extensions; <tt>^</tt> and <tt>_</tt>
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are not yet used in Common Lisp
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but are part of the syntax of reserved tokens
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and are reserved to implementors;
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<tt>~</tt> is not yet used in Common Lisp and is reserved to implementors;
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and <tt>$</tt> and <tt>%</tt> are normally regarded as alphabetic characters
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but are not used in the names of any standard Common Lisp functions,
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variables, or other entities.
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<br><img align=bottom alt="old_change_end" src="gif/old_change_end.gif">
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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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X3J13 voted in June 1989 (PRETTY-PRINT-INTERFACE) <A NAME=928> </A>
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to add a <tt>format</tt> directive <tt>~_</tt> (see chapter <A HREF="node253.html#PPRINT">27</A>).
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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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The following characters are called <i>semi-standard</i>:
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<P><pre>
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#\Backspace #\Tab #\Linefeed #\Page #\Return #\Rubout
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</pre><P>
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Not all implementations of Common Lisp need to support them; but those
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implementations that
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use the standard ASCII character set should support them, treating them as
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corresponding respectively to the ASCII characters BS (octal code 010),
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HT (011), LF (012), FF (014), CR (015), and DEL
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(177). These characters are not
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members of the subtype <tt>standard-char</tt> unless synonymous with
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one of the standard characters specified above.
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For example, in a given implementation it might
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be sensible for the implementor to define
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<tt>#\Linefeed</tt> or <tt>#\Return</tt> to be synonymous with <tt>#\Newline</tt>,
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or <tt>#\Tab</tt> to be synonymous with <tt>#\Space</tt>.
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<P>
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<BR> <HR><A NAME=tex2html1784 HREF="node23.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html1782 HREF="node21.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html1776 HREF="node21.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html1786 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html1787 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html1785 HREF="node23.html"> Line Divisions</A>
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<B>Up:</B> <A NAME=tex2html1783 HREF="node21.html"> Characters</A>
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<B> Previous:</B> <A NAME=tex2html1777 HREF="node21.html"> Characters</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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