93 lines
4 KiB
HTML
93 lines
4 KiB
HTML
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Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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<title>About Expressions (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="Hello-Scheme_0021.html" rel="up" title="Hello Scheme!">
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<link href="About-Closure.html" rel="next" title="About Closure">
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<div class="section-level-extent" id="About-Expressions">
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<p>
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Next: <a href="About-Closure.html" accesskey="n" rel="next">The Concept of Closure</a>, Previous: <a href="About-Procedures.html" accesskey="p" rel="prev">The Representation and Use of Procedures</a>, Up: <a href="Hello-Scheme_0021.html" accesskey="u" rel="up">Hello Scheme!</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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<hr>
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<h3 class="section" id="Expressions-and-Evaluation"><span>3.3 Expressions and Evaluation<a class="copiable-link" href="#Expressions-and-Evaluation"> ¶</a></span></h3>
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<p>So far, we have met expressions that <em class="emph">do</em> things, such as the
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<code class="code">define</code> expressions that create and initialize new variables, and
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we have also talked about expressions that have <em class="emph">values</em>, for
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example the value of the procedure invocation expression:
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(string-append "/home" "/" "andrew")
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</pre></div>
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<p>but we haven’t yet been precise about what causes an expression like
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this procedure invocation to be reduced to its “value”, or how the
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processing of such expressions relates to the execution of a Scheme
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program as a whole.
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</p>
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<p>This section clarifies what we mean by an expression’s value, by
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introducing the idea of <em class="dfn">evaluation</em>. It discusses the side effects
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that evaluation can have, explains how each of the various types of
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Scheme expression is evaluated, and describes the behavior and use of
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the Guile REPL as a mechanism for exploring evaluation. The section
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concludes with a very brief summary of Scheme’s common syntactic
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expressions.
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</p>
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<ul class="mini-toc">
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<li><a href="Evaluating.html" accesskey="1">Evaluating Expressions and Executing Programs</a></li>
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<li><a href="Tail-Calls.html" accesskey="2">Tail calls</a></li>
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<li><a href="The-REPL.html" accesskey="3">Using the Guile REPL</a></li>
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<li><a href="Syntax-Summary.html" accesskey="4">Summary of Common Syntax</a></li>
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</ul>
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</div>
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