108 lines
5.4 KiB
HTML
108 lines
5.4 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>Syntax Summary (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="About-Expressions.html" rel="up" title="About Expressions">
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<div class="subsection-level-extent" id="Syntax-Summary">
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<p>
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Previous: <a href="The-REPL.html" accesskey="p" rel="prev">Using the Guile REPL</a>, Up: <a href="About-Expressions.html" accesskey="u" rel="up">Expressions and Evaluation</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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<h4 class="subsection" id="Summary-of-Common-Syntax"><span>3.3.4 Summary of Common Syntax<a class="copiable-link" href="#Summary-of-Common-Syntax"> ¶</a></span></h4>
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<p>This subsection lists the most commonly used Scheme syntactic
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expressions, simply so that you will recognize common special syntax
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when you see it. For a full description of each of these syntaxes,
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follow the appropriate reference.
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</p>
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<p><code class="code">lambda</code> (see <a class="pxref" href="Lambda.html">Lambda: Basic Procedure Creation</a>) is used to construct procedure objects.
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</p>
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<p><code class="code">define</code> (see <a class="pxref" href="Top-Level.html">Top Level Variable Definitions</a>) is used to create a new variable and
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set its initial value.
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</p>
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<p><code class="code">set!</code> (see <a class="pxref" href="Top-Level.html">Top Level Variable Definitions</a>) is used to modify an existing variable’s
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value.
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</p>
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<p><code class="code">let</code>, <code class="code">let*</code> and <code class="code">letrec</code> (see <a class="pxref" href="Local-Bindings.html">Local Variable Bindings</a>)
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create an inner lexical environment for the evaluation of a sequence of
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expressions, in which a specified set of local variables is bound to the
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values of a corresponding set of expressions. For an introduction to
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environments, see See <a class="xref" href="About-Closure.html">The Concept of Closure</a>.
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</p>
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<p><code class="code">begin</code> (see <a class="pxref" href="begin.html">Sequencing and Splicing</a>) executes a sequence of expressions in order
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and returns the value of the last expression. Note that this is not the
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same as a procedure which returns its last argument, because the
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evaluation of a procedure invocation expression does not guarantee to
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evaluate the arguments in order.
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</p>
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<p><code class="code">if</code> and <code class="code">cond</code> (see <a class="pxref" href="Conditionals.html">Simple Conditional Evaluation</a>) provide conditional
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evaluation of argument expressions depending on whether one or more
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conditions evaluate to “true” or “false”.
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</p>
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<p><code class="code">case</code> (see <a class="pxref" href="Conditionals.html">Simple Conditional Evaluation</a>) provides conditional evaluation of
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argument expressions depending on whether a variable has one of a
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specified group of values.
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</p>
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<p><code class="code">and</code> (see <a class="pxref" href="and-or.html">Conditional Evaluation of a Sequence of Expressions</a>) executes a sequence of expressions in order
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until either there are no expressions left, or one of them evaluates to
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“false”.
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</p>
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<p><code class="code">or</code> (see <a class="pxref" href="and-or.html">Conditional Evaluation of a Sequence of Expressions</a>) executes a sequence of expressions in order
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until either there are no expressions left, or one of them evaluates to
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“true”.
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</p>
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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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Previous: <a href="The-REPL.html">Using the Guile REPL</a>, Up: <a href="About-Expressions.html">Expressions and Evaluation</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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</body>
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