88 lines
3.9 KiB
HTML
88 lines
3.9 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>Accessors (Guile Reference Manual)</title>
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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="Methods-and-Generic-Functions.html" rel="up" title="Methods and Generic Functions">
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<link href="Extending-Primitives.html" rel="next" title="Extending Primitives">
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</head>
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<body lang="en">
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<div class="subsection-level-extent" id="Accessors">
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<div class="nav-panel">
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<p>
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Next: <a href="Extending-Primitives.html" accesskey="n" rel="next">Extending Primitives</a>, Up: <a href="Methods-and-Generic-Functions.html" accesskey="u" rel="up">Methods and Generic Functions</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="subsection" id="Accessors-1"><span>8.6.1 Accessors<a class="copiable-link" href="#Accessors-1"> ¶</a></span></h4>
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<p>An accessor is a generic function that can also be used with the
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generalized <code class="code">set!</code> syntax (see <a class="pxref" href="Procedures-with-Setters.html">Procedures with Setters</a>). Guile
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will handle a call like
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</p>
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<div class="example">
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<pre class="example-preformatted">(set! (<code class="code">accessor</code> <code class="code">args</code>...) <code class="code">value</code>)
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</pre></div>
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<p>by calling the most specialized method of <code class="code">accessor</code> that matches
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the classes of <code class="code">args</code> and <code class="code">value</code>. <code class="code">define-accessor</code> is
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used to bind an identifier to an accessor.
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</p>
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<dl class="first-deffn">
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<dt class="deffn" id="index-define_002daccessor"><span class="category-def">syntax: </span><span><strong class="def-name">define-accessor</strong> <var class="def-var-arguments">symbol</var><a class="copiable-link" href="#index-define_002daccessor"> ¶</a></span></dt>
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<dd><p>Create an accessor with name <var class="var">symbol</var> and bind it to the variable
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<var class="var">symbol</var>. If <var class="var">symbol</var> was previously bound to a Scheme
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procedure (or procedure-with-setter), the old procedure (and setter) is
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incorporated into the new accessor as its default procedure (and
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setter). Any other previous value, including an existing generic
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function or accessor, is discarded and replaced by a new, empty
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accessor.
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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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