111 lines
5.9 KiB
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111 lines
5.9 KiB
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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>The SCM Type (Guile Reference Manual)</title>
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<meta name="description" content="The SCM Type (Guile Reference Manual)">
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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="API-Reference.html" rel="up" title="API Reference">
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</head>
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<body lang="en">
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<div class="section-level-extent" id="The-SCM-Type">
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<div class="nav-panel">
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<p>
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Next: <a href="Initialization.html" accesskey="n" rel="next">Initializing Guile</a>, Previous: <a href="Deprecation.html" accesskey="p" rel="prev">Deprecation</a>, Up: <a href="API-Reference.html" accesskey="u" rel="up">API Reference</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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<h3 class="section" id="The-SCM-Type-1"><span>6.3 The SCM Type<a class="copiable-link" href="#The-SCM-Type-1"> ¶</a></span></h3>
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<p>Guile represents all Scheme values with the single C type <code class="code">SCM</code>.
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For an introduction to this topic, See <a class="xref" href="Dynamic-Types.html">Dynamic Types</a>.
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</p>
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<dl class="first-deftp">
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<dt class="deftp" id="index-SCM"><span class="category-def">C Type: </span><span><strong class="def-name">SCM</strong><a class="copiable-link" href="#index-SCM"> ¶</a></span></dt>
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<dd><p><code class="code">SCM</code> is the user level abstract C type that is used to represent
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all of Guile’s Scheme objects, no matter what the Scheme object type is.
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No C operation except assignment is guaranteed to work with variables of
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type <code class="code">SCM</code>, so you should only use macros and functions to work
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with <code class="code">SCM</code> values. Values are converted between C data types and
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the <code class="code">SCM</code> type with utility functions and macros.
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</p></dd></dl>
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<a class="index-entry-id" id="index-SCM-data-type"></a>
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<dl class="first-deftp">
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<dt class="deftp" id="index-scm_005ft_005fbits"><span class="category-def">C Type: </span><span><strong class="def-name">scm_t_bits</strong><a class="copiable-link" href="#index-scm_005ft_005fbits"> ¶</a></span></dt>
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<dd><p><code class="code">scm_t_bits</code> is an unsigned integral data type that is guaranteed
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to be large enough to hold all information that is required to
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represent any Scheme object. While this data type is mostly used to
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implement Guile’s internals, the use of this type is also necessary to
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write certain kinds of extensions to Guile.
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</p></dd></dl>
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<dl class="first-deftp">
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<dt class="deftp" id="index-scm_005ft_005fsigned_005fbits"><span class="category-def">C Type: </span><span><strong class="def-name">scm_t_signed_bits</strong><a class="copiable-link" href="#index-scm_005ft_005fsigned_005fbits"> ¶</a></span></dt>
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<dd><p>This is a signed integral type of the same size as <code class="code">scm_t_bits</code>.
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</p></dd></dl>
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<dl class="first-deftypefn">
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<dt class="deftypefn" id="index-SCM_005fUNPACK"><span class="category-def">C Macro: </span><span><code class="def-type">scm_t_bits</code> <strong class="def-name">SCM_UNPACK</strong> <code class="def-code-arguments">(SCM <var class="var">x</var>)</code><a class="copiable-link" href="#index-SCM_005fUNPACK"> ¶</a></span></dt>
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<dd><p>Transforms the <code class="code">SCM</code> value <var class="var">x</var> into its representation as an
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integral type. Only after applying <code class="code">SCM_UNPACK</code> it is possible to
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access the bits and contents of the <code class="code">SCM</code> value.
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</p></dd></dl>
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<dl class="first-deftypefn">
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<dt class="deftypefn" id="index-SCM_005fPACK"><span class="category-def">C Macro: </span><span><code class="def-type">SCM</code> <strong class="def-name">SCM_PACK</strong> <code class="def-code-arguments">(scm_t_bits <var class="var">x</var>)</code><a class="copiable-link" href="#index-SCM_005fPACK"> ¶</a></span></dt>
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<dd><p>Takes a valid integral representation of a Scheme object and transforms
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it into its representation as a <code class="code">SCM</code> value.
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</p></dd></dl>
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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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Next: <a href="Initialization.html">Initializing Guile</a>, Previous: <a href="Deprecation.html">Deprecation</a>, Up: <a href="API-Reference.html">API Reference</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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