234 lines
11 KiB
HTML
234 lines
11 KiB
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>PEG Syntax Reference (Guile Reference Manual)</title>
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<meta name="description" content="PEG Syntax Reference (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="PEG-Parsing.html" rel="up" title="PEG Parsing">
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</head>
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<body lang="en">
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<div class="subsection-level-extent" id="PEG-Syntax-Reference">
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<div class="nav-panel">
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<p>
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Next: <a href="PEG-API-Reference.html" accesskey="n" rel="next">PEG API Reference</a>, Up: <a href="PEG-Parsing.html" accesskey="u" rel="up">PEG Parsing</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="PEG-Syntax-Reference-1"><span>6.15.1 PEG Syntax Reference<a class="copiable-link" href="#PEG-Syntax-Reference-1"> ¶</a></span></h4>
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<h4 class="subsubheading" id="Normal-PEG-Syntax_003a"><span>Normal PEG Syntax:<a class="copiable-link" href="#Normal-PEG-Syntax_003a"> ¶</a></span></h4>
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<dl class="first-deftp">
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<dt class="deftp" id="index-sequence"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">sequence</strong> <var class="def-var-arguments">a b</var><a class="copiable-link" href="#index-sequence"> ¶</a></span></dt>
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<dd><p>Parses <var class="var">a</var>. If this succeeds, continues to parse <var class="var">b</var> from the
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end of the text parsed as <var class="var">a</var>. Succeeds if both <var class="var">a</var> and
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<var class="var">b</var> succeed.
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</p>
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<p><code class="code">"a b"</code>
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</p>
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<p><code class="code">(and a b)</code>
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</p></dd></dl>
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<dl class="first-deftp">
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<dt class="deftp" id="index-ordered-choice"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">ordered choice</strong> <var class="def-var-arguments">a b</var><a class="copiable-link" href="#index-ordered-choice"> ¶</a></span></dt>
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<dd><p>Parses <var class="var">a</var>. If this fails, backtracks and parses <var class="var">b</var>.
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Succeeds if either <var class="var">a</var> or <var class="var">b</var> succeeds.
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</p>
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<p><code class="code">"a/b"</code>
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</p>
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<p><code class="code">(or a b)</code>
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</p></dd></dl>
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<dl class="first-deftp">
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<dt class="deftp" id="index-zero-or-more"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">zero or more</strong> <var class="def-var-arguments">a</var><a class="copiable-link" href="#index-zero-or-more"> ¶</a></span></dt>
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<dd><p>Parses <var class="var">a</var> as many times in a row as it can, starting each <var class="var">a</var>
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at the end of the text parsed by the previous <var class="var">a</var>. Always
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succeeds.
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</p>
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<p><code class="code">"a*"</code>
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</p>
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<p><code class="code">(* a)</code>
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</p></dd></dl>
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<dl class="first-deftp">
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<dt class="deftp" id="index-one-or-more"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">one or more</strong> <var class="def-var-arguments">a</var><a class="copiable-link" href="#index-one-or-more"> ¶</a></span></dt>
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<dd><p>Parses <var class="var">a</var> as many times in a row as it can, starting each <var class="var">a</var>
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at the end of the text parsed by the previous <var class="var">a</var>. Succeeds if at
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least one <var class="var">a</var> was parsed.
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</p>
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<p><code class="code">"a+"</code>
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</p>
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<p><code class="code">(+ a)</code>
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</p></dd></dl>
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<dl class="first-deftp">
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<dt class="deftp" id="index-optional"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">optional</strong> <var class="def-var-arguments">a</var><a class="copiable-link" href="#index-optional"> ¶</a></span></dt>
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<dd><p>Tries to parse <var class="var">a</var>. Succeeds if <var class="var">a</var> succeeds.
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</p>
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<p><code class="code">"a?"</code>
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</p>
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<p><code class="code">(? a)</code>
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</p></dd></dl>
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<dl class="first-deftp">
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<dt class="deftp" id="index-followed-by"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">followed by</strong> <var class="def-var-arguments">a</var><a class="copiable-link" href="#index-followed-by"> ¶</a></span></dt>
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<dd><p>Makes sure it is possible to parse <var class="var">a</var>, but does not actually parse
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it. Succeeds if <var class="var">a</var> would succeed.
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</p>
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<p><code class="code">"&a"</code>
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</p>
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<p><code class="code">(followed-by a)</code>
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</p></dd></dl>
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<dl class="first-deftp">
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<dt class="deftp" id="index-not-followed-by"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">not followed by</strong> <var class="def-var-arguments">a</var><a class="copiable-link" href="#index-not-followed-by"> ¶</a></span></dt>
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<dd><p>Makes sure it is impossible to parse <var class="var">a</var>, but does not actually
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parse it. Succeeds if <var class="var">a</var> would fail.
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</p>
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<p><code class="code">"!a"</code>
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</p>
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<p><code class="code">(not-followed-by a)</code>
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</p></dd></dl>
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<dl class="first-deftp">
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<dt class="deftp" id="index-string-literal"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">string literal</strong> <var class="def-var-arguments">“abc”</var><a class="copiable-link" href="#index-string-literal"> ¶</a></span></dt>
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<dd><p>Parses the string <var class="var">"abc"</var>. Succeeds if that parsing succeeds.
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</p>
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<p><code class="code">"'abc'"</code>
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</p>
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<p><code class="code">"abc"</code>
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</p></dd></dl>
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<dl class="first-deftp">
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<dt class="deftp" id="index-any-character"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">any character</strong><a class="copiable-link" href="#index-any-character"> ¶</a></span></dt>
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<dd><p>Parses any single character. Succeeds unless there is no more text to
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be parsed.
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</p>
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<p><code class="code">"."</code>
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</p>
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<p><code class="code">peg-any</code>
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</p></dd></dl>
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<dl class="first-deftp">
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<dt class="deftp" id="index-character-class"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">character class</strong> <var class="def-var-arguments">a b</var><a class="copiable-link" href="#index-character-class"> ¶</a></span></dt>
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<dd><p>Alternative syntax for “Ordered Choice <var class="var">a</var> <var class="var">b</var>” if <var class="var">a</var> and
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<var class="var">b</var> are characters.
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</p>
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<p><code class="code">"[ab]"</code>
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</p>
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<p><code class="code">(or "a" "b")</code>
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</p></dd></dl>
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<dl class="first-deftp">
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<dt class="deftp" id="index-range-of-characters"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">range of characters</strong> <var class="def-var-arguments">a z</var><a class="copiable-link" href="#index-range-of-characters"> ¶</a></span></dt>
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<dd><p>Parses any character falling between <var class="var">a</var> and <var class="var">z</var>.
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</p>
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<p><code class="code">"[a-z]"</code>
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</p>
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<p><code class="code">(range #\a #\z)</code>
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</p></dd></dl>
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<p>Example:
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</p>
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<div class="example">
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<pre class="example-preformatted">"(a !b / c &d*) 'e'+"
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</pre></div>
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<p>Would be:
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(and
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(or
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(and a (not-followed-by b))
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(and c (followed-by (* d))))
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(+ "e"))
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</pre></div>
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<h4 class="subsubheading" id="Extended-Syntax"><span>Extended Syntax<a class="copiable-link" href="#Extended-Syntax"> ¶</a></span></h4>
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<p>There is some extra syntax for S-expressions.
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</p>
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<dl class="first-deftp">
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<dt class="deftp" id="index-ignore"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">ignore</strong> <var class="def-var-arguments">a</var><a class="copiable-link" href="#index-ignore"> ¶</a></span></dt>
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<dd><p>Ignore the text matching <var class="var">a</var>
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</p></dd></dl>
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<dl class="first-deftp">
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<dt class="deftp" id="index-capture"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">capture</strong> <var class="def-var-arguments">a</var><a class="copiable-link" href="#index-capture"> ¶</a></span></dt>
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<dd><p>Capture the text matching <var class="var">a</var>.
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</p></dd></dl>
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<dl class="first-deftp">
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<dt class="deftp" id="index-peg"><span class="category-def">PEG Pattern: </span><span><strong class="def-name">peg</strong> <var class="def-var-arguments">a</var><a class="copiable-link" href="#index-peg"> ¶</a></span></dt>
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<dd><p>Embed the PEG pattern <var class="var">a</var> using string syntax.
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</p></dd></dl>
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<p>Example:
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</p>
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<div class="example">
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<pre class="example-preformatted">"!a / 'b'"
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</pre></div>
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<p>Is equivalent to
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(or (peg "!a") "b")
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</pre></div>
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<p>and
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(or (not-followed-by a) "b")
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</pre></div>
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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="PEG-API-Reference.html">PEG API Reference</a>, Up: <a href="PEG-Parsing.html">PEG Parsing</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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</body>
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</html>
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