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HTML
221 lines
10 KiB
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<html>
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<!-- Created by GNU Texinfo 7.1, https://www.gnu.org/software/texinfo/ -->
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<!-- This manual documents Guile version 3.0.10.
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Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
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Inc.
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with no
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Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
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copy of the license is included in the section entitled "GNU Free
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Documentation License." -->
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<title>Common Feature Symbols (Guile Reference Manual)</title>
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<meta name="description" content="Common Feature Symbols (Guile Reference Manual)">
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<meta name="keywords" content="Common Feature Symbols (Guile Reference Manual)">
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<link href="index.html" rel="start" title="Top">
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<link href="Concept-Index.html" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Feature-Tracking.html" rel="up" title="Feature Tracking">
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<link href="Feature-Manipulation.html" rel="prev" title="Feature Manipulation">
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</head>
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<body lang="en">
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<div class="subsubsection-level-extent" id="Common-Feature-Symbols">
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<div class="nav-panel">
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<p>
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Previous: <a href="Feature-Manipulation.html" accesskey="p" rel="prev">Feature Manipulation</a>, Up: <a href="Feature-Tracking.html" accesskey="u" rel="up">Feature Tracking</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<h4 class="subsubsection" id="Common-Feature-Symbols-1"><span>6.23.2.2 Common Feature Symbols<a class="copiable-link" href="#Common-Feature-Symbols-1"> ¶</a></span></h4>
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<p>In general, a particular feature may be available for one of two
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reasons. Either because the Guile library was configured and compiled
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with that feature enabled — i.e. the feature is built into the library
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on your system. Or because some C or Scheme code that was dynamically
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loaded by Guile has added that feature to the list.
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</p>
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<p>In the first category, here are the features that the current version of
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Guile may define (depending on how it is built), and what they mean.
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</p>
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<dl class="table">
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<dt><code class="code">array</code></dt>
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<dd><p>Indicates support for arrays (see <a class="pxref" href="Arrays.html">Arrays</a>).
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</p>
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</dd>
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<dt><code class="code">array-for-each</code></dt>
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<dd><p>Indicates availability of <code class="code">array-for-each</code> and other array mapping
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procedures (see <a class="pxref" href="Arrays.html">Arrays</a>).
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</p>
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</dd>
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<dt><code class="code">char-ready?</code></dt>
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<dd><p>Indicates that the <code class="code">char-ready?</code> function is available
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(see <a class="pxref" href="Venerable-Port-Interfaces.html">Venerable Port Interfaces</a>).
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</p>
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</dd>
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<dt><code class="code">complex</code></dt>
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<dd><p>Indicates support for complex numbers.
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</p>
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</dd>
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<dt><code class="code">current-time</code></dt>
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<dd><p>Indicates availability of time-related functions: <code class="code">times</code>,
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<code class="code">get-internal-run-time</code> and so on (see <a class="pxref" href="Time.html">Time</a>).
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</p>
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</dd>
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<dt><code class="code">debug-extensions</code></dt>
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<dd><p>Indicates that the debugging evaluator is available, together with the
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options for controlling it.
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</p>
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</dd>
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<dt><code class="code">delay</code></dt>
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<dd><p>Indicates support for promises (see <a class="pxref" href="Delayed-Evaluation.html">Delayed Evaluation</a>).
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</p>
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</dd>
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<dt><code class="code">EIDs</code></dt>
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<dd><p>Indicates that the <code class="code">geteuid</code> and <code class="code">getegid</code> really return
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effective user and group IDs (see <a class="pxref" href="Processes.html">Processes</a>).
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</p>
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</dd>
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<dt><code class="code">inexact</code></dt>
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<dd><p>Indicates support for inexact numbers.
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</p>
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</dd>
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<dt><code class="code">i/o-extensions</code></dt>
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<dd><p>Indicates availability of the following extended I/O procedures:
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<code class="code">ftell</code>, <code class="code">redirect-port</code>, <code class="code">dup->fdes</code>, <code class="code">dup2</code>,
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<code class="code">fileno</code>, <code class="code">isatty?</code>, <code class="code">fdopen</code>,
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<code class="code">primitive-move->fdes</code> and <code class="code">fdes->ports</code> (see <a class="pxref" href="Ports-and-File-Descriptors.html">Ports and File Descriptors</a>).
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</p>
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</dd>
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<dt><code class="code">net-db</code></dt>
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<dd><p>Indicates availability of network database functions:
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<code class="code">scm_gethost</code>, <code class="code">scm_getnet</code>, <code class="code">scm_getproto</code>,
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<code class="code">scm_getserv</code>, <code class="code">scm_sethost</code>, <code class="code">scm_setnet</code>, <code class="code">scm_setproto</code>,
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<code class="code">scm_setserv</code>, and their ‘byXXX’ variants (see <a class="pxref" href="Network-Databases.html">Network Databases</a>).
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</p>
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</dd>
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<dt><code class="code">posix</code></dt>
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<dd><p>Indicates support for POSIX functions: <code class="code">pipe</code>, <code class="code">getgroups</code>,
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<code class="code">kill</code>, <code class="code">execl</code> and so on (see <a class="pxref" href="POSIX.html"><abbr class="acronym">POSIX</abbr> System Calls and Networking</a>).
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</p>
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</dd>
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<dt><code class="code">fork</code></dt>
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<dd><p>Indicates support for the POSIX <code class="code">fork</code> function (see <a class="pxref" href="Processes.html"><code class="code">primitive-fork</code></a>).
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</p>
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</dd>
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<dt><code class="code">popen</code></dt>
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<dd><p>Indicates support for <code class="code">open-pipe</code> in the <code class="code">(ice-9 popen)</code>
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module (see <a class="pxref" href="Pipes.html">Pipes</a>).
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</p>
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</dd>
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<dt><code class="code">random</code></dt>
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<dd><p>Indicates availability of random number generation functions:
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<code class="code">random</code>, <code class="code">copy-random-state</code>, <code class="code">random-uniform</code> and so on
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(see <a class="pxref" href="Random.html">Random Number Generation</a>).
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</p>
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</dd>
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<dt><code class="code">reckless</code></dt>
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<dd><p>Indicates that Guile was built with important checks omitted — you
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should never see this!
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</p>
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</dd>
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<dt><code class="code">regex</code></dt>
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<dd><p>Indicates support for POSIX regular expressions using
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<code class="code">make-regexp</code>, <code class="code">regexp-exec</code> and friends (see <a class="pxref" href="Regexp-Functions.html">Regexp Functions</a>).
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</p>
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</dd>
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<dt><code class="code">socket</code></dt>
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<dd><p>Indicates availability of socket-related functions: <code class="code">socket</code>,
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<code class="code">bind</code>, <code class="code">connect</code> and so on (see <a class="pxref" href="Network-Sockets-and-Communication.html">Network Sockets and Communication</a>).
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</p>
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</dd>
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<dt><code class="code">sort</code></dt>
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<dd><p>Indicates availability of sorting and merging functions
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(see <a class="pxref" href="Sorting.html">Sorting</a>).
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</p>
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</dd>
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<dt><code class="code">system</code></dt>
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<dd><p>Indicates that the <code class="code">system</code> function is available
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(see <a class="pxref" href="Processes.html">Processes</a>).
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</p>
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</dd>
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<dt><code class="code">threads</code></dt>
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<dd><p>Indicates support for multithreading (see <a class="pxref" href="Threads.html">Threads</a>).
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</p>
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</dd>
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<dt><code class="code">values</code></dt>
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<dd><p>Indicates support for multiple return values using <code class="code">values</code> and
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<code class="code">call-with-values</code> (see <a class="pxref" href="Multiple-Values.html">Returning and Accepting Multiple Values</a>).
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</p></dd>
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</dl>
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<p>Available features in the second category depend, by definition, on what
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additional code your Guile process has loaded in. The following table
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lists features that you might encounter for this reason.
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</p>
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<dl class="table">
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<dt><code class="code">defmacro</code></dt>
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<dd><p>Indicates that the <code class="code">defmacro</code> macro is available (see <a class="pxref" href="Macros.html">Macros</a>).
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</p>
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</dd>
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<dt><code class="code">describe</code></dt>
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<dd><p>Indicates that the <code class="code">(oop goops describe)</code> module has been loaded,
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which provides a procedure for describing the contents of GOOPS
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instances.
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</p>
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</dd>
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<dt><code class="code">readline</code></dt>
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<dd><p>Indicates that Guile has loaded in Readline support, for command line
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editing (see <a class="pxref" href="Readline-Support.html">Readline Support</a>).
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</p>
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</dd>
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<dt><code class="code">record</code></dt>
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<dd><p>Indicates support for record definition using <code class="code">make-record-type</code>
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and friends (see <a class="pxref" href="Records.html">Records</a>).
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</p></dd>
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</dl>
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<p>Although these tables may seem exhaustive, it is probably unwise in
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practice to rely on them, as the correspondences between feature symbols
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and available procedures/behavior are not strictly defined. If you are
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writing code that needs to check for the existence of some procedure, it
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is probably safer to do so directly using the <code class="code">defined?</code> procedure
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than to test for the corresponding feature using <code class="code">provided?</code>.
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</p>
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</div>
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<hr>
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<div class="nav-panel">
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<p>
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Previous: <a href="Feature-Manipulation.html">Feature Manipulation</a>, Up: <a href="Feature-Tracking.html">Feature Tracking</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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