92 lines
4.4 KiB
HTML
92 lines
4.4 KiB
HTML
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<!DOCTYPE html>
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<html>
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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>Feature Manipulation (Guile Reference Manual)</title>
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<meta name="description" content="Feature Manipulation (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="Common-Feature-Symbols.html" rel="next" title="Common Feature Symbols">
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</head>
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<body lang="en">
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<div class="subsubsection-level-extent" id="Feature-Manipulation">
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<div class="nav-panel">
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<p>
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Next: <a href="Common-Feature-Symbols.html" accesskey="n" rel="next">Common Feature Symbols</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="Feature-Manipulation-1"><span>6.23.2.1 Feature Manipulation<a class="copiable-link" href="#Feature-Manipulation-1"> ¶</a></span></h4>
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<p>To check whether a particular feature is available, use the
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<code class="code">provided?</code> procedure:
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</p>
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<dl class="first-deffn">
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<dt class="deffn" id="index-provided_003f"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">provided?</strong> <var class="def-var-arguments">feature</var><a class="copiable-link" href="#index-provided_003f"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-feature_003f"><span class="category-def">Deprecated Scheme Procedure: </span><span><strong class="def-name">feature?</strong> <var class="def-var-arguments">feature</var><a class="copiable-link" href="#index-feature_003f"> ¶</a></span></dt>
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<dd><p>Return <code class="code">#t</code> if the specified <var class="var">feature</var> is available, otherwise
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<code class="code">#f</code>.
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</p></dd></dl>
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<p>To advertise a feature from your own Scheme code, you can use the
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<code class="code">provide</code> procedure:
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</p>
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<dl class="first-deffn">
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<dt class="deffn" id="index-provide"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">provide</strong> <var class="def-var-arguments">feature</var><a class="copiable-link" href="#index-provide"> ¶</a></span></dt>
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<dd><p>Add <var class="var">feature</var> to the list of available features in this Guile
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process.
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</p></dd></dl>
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<p>For C code, the equivalent function takes its feature name as a
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<code class="code">char *</code> argument for convenience:
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</p>
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<dl class="first-deftypefn">
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<dt class="deftypefn" id="index-scm_005fadd_005ffeature"><span class="category-def">C Function: </span><span><code class="def-type">void</code> <strong class="def-name">scm_add_feature</strong> <code class="def-code-arguments">(const char *str)</code><a class="copiable-link" href="#index-scm_005fadd_005ffeature"> ¶</a></span></dt>
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<dd><p>Add a symbol with name <var class="var">str</var> to the list of available features in
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this Guile process.
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</p></dd></dl>
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</div>
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</body>
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</html>
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