86 lines
3.4 KiB
HTML
86 lines
3.4 KiB
HTML
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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<title>Eval Variable (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="Evaluating.html" rel="up" title="Evaluating">
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<link href="Eval-Procedure.html" rel="next" title="Eval Procedure">
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<div class="subsubsection-level-extent" id="Eval-Variable">
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<p>
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Next: <a href="Eval-Procedure.html" accesskey="n" rel="next">Evaluating a Procedure Invocation Expression</a>, Previous: <a href="Eval-Literal.html" accesskey="p" rel="prev">Evaluating Literal Data</a>, Up: <a href="Evaluating.html" accesskey="u" rel="up">Evaluating Expressions and Executing Programs</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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<h4 class="subsubsection" id="Evaluating-a-Variable-Reference"><span>3.3.1.2 Evaluating a Variable Reference<a class="copiable-link" href="#Evaluating-a-Variable-Reference"> ¶</a></span></h4>
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<p>When an expression that consists simply of a variable name is evaluated,
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the value of the expression is the value of the named variable. The
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evaluation of a variable reference expression has no side effects.
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</p>
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<p>So, after
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(define key "Paul Evans")
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</pre></div>
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<p>the value of the expression <code class="code">key</code> is the string value <code class="code">"Paul
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Evans"</code>. If <var class="var">key</var> is then modified by
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(set! key 3.74)
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</pre></div>
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<p>the value of the expression <code class="code">key</code> is the numeric value 3.74.
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</p>
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<p>If there is no variable with the specified name, evaluation of the
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variable reference expression signals an error.
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</p>
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