181 lines
9.1 KiB
HTML
181 lines
9.1 KiB
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<!DOCTYPE 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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any later version published by the Free Software Foundation; with no
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copy of the license is included in the section entitled "GNU Free
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<title>Match Structures (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="Regular-Expressions.html" rel="up" title="Regular Expressions">
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<link href="Backslash-Escapes.html" rel="next" title="Backslash Escapes">
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<link href="Regexp-Functions.html" rel="prev" title="Regexp Functions">
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</head>
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<body lang="en">
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<div class="subsection-level-extent" id="Match-Structures">
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<div class="nav-panel">
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<p>
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Next: <a href="Backslash-Escapes.html" accesskey="n" rel="next">Backslash Escapes</a>, Previous: <a href="Regexp-Functions.html" accesskey="p" rel="prev">Regexp Functions</a>, Up: <a href="Regular-Expressions.html" accesskey="u" rel="up">Regular Expressions</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="Match-Structures-1"><span>6.13.2 Match Structures<a class="copiable-link" href="#Match-Structures-1"> ¶</a></span></h4>
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<a class="index-entry-id" id="index-match-structures"></a>
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<p>A <em class="dfn">match structure</em> is the object returned by <code class="code">string-match</code> and
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<code class="code">regexp-exec</code>. It describes which portion of a string, if any,
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matched the given regular expression. Match structures include: a
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reference to the string that was checked for matches; the starting and
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ending positions of the regexp match; and, if the regexp included any
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parenthesized subexpressions, the starting and ending positions of each
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submatch.
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</p>
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<p>In each of the regexp match functions described below, the <code class="code">match</code>
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argument must be a match structure returned by a previous call to
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<code class="code">string-match</code> or <code class="code">regexp-exec</code>. Most of these functions
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return some information about the original target string that was
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matched against a regular expression; we will call that string
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<var class="var">target</var> for easy reference.
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</p>
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<dl class="first-deffn">
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<dt class="deffn" id="index-regexp_002dmatch_003f"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">regexp-match?</strong> <var class="def-var-arguments">obj</var><a class="copiable-link" href="#index-regexp_002dmatch_003f"> ¶</a></span></dt>
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<dd><p>Return <code class="code">#t</code> if <var class="var">obj</var> is a match structure returned by a
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previous call to <code class="code">regexp-exec</code>, or <code class="code">#f</code> otherwise.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-match_003asubstring"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">match:substring</strong> <var class="def-var-arguments">match [n]</var><a class="copiable-link" href="#index-match_003asubstring"> ¶</a></span></dt>
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<dd><p>Return the portion of <var class="var">target</var> matched by subexpression number
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<var class="var">n</var>. Submatch 0 (the default) represents the entire regexp match.
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If the regular expression as a whole matched, but the subexpression
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number <var class="var">n</var> did not match, return <code class="code">#f</code>.
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</p></dd></dl>
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<div class="example lisp">
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<pre class="lisp-preformatted">(define s (string-match "[0-9][0-9][0-9][0-9]" "blah2002foo"))
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(match:substring s)
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⇒ "2002"
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;; match starting at offset 6 in the string
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(match:substring
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(string-match "[0-9][0-9][0-9][0-9]" "blah987654" 6))
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⇒ "7654"
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</pre></div>
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<dl class="first-deffn">
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<dt class="deffn" id="index-match_003astart"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">match:start</strong> <var class="def-var-arguments">match [n]</var><a class="copiable-link" href="#index-match_003astart"> ¶</a></span></dt>
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<dd><p>Return the starting position of submatch number <var class="var">n</var>.
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</p></dd></dl>
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<p>In the following example, the result is 4, since the match starts at
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character index 4:
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(define s (string-match "[0-9][0-9][0-9][0-9]" "blah2002foo"))
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(match:start s)
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⇒ 4
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</pre></div>
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<dl class="first-deffn">
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<dt class="deffn" id="index-match_003aend"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">match:end</strong> <var class="def-var-arguments">match [n]</var><a class="copiable-link" href="#index-match_003aend"> ¶</a></span></dt>
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<dd><p>Return the ending position of submatch number <var class="var">n</var>.
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</p></dd></dl>
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<p>In the following example, the result is 8, since the match runs between
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characters 4 and 8 (i.e. the “2002”).
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(define s (string-match "[0-9][0-9][0-9][0-9]" "blah2002foo"))
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(match:end s)
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⇒ 8
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</pre></div>
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<dl class="first-deffn">
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<dt class="deffn" id="index-match_003aprefix"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">match:prefix</strong> <var class="def-var-arguments">match</var><a class="copiable-link" href="#index-match_003aprefix"> ¶</a></span></dt>
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<dd><p>Return the unmatched portion of <var class="var">target</var> preceding the regexp match.
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(define s (string-match "[0-9][0-9][0-9][0-9]" "blah2002foo"))
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(match:prefix s)
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⇒ "blah"
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</pre></div>
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</dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-match_003asuffix"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">match:suffix</strong> <var class="def-var-arguments">match</var><a class="copiable-link" href="#index-match_003asuffix"> ¶</a></span></dt>
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<dd><p>Return the unmatched portion of <var class="var">target</var> following the regexp match.
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</p></dd></dl>
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<div class="example lisp">
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<pre class="lisp-preformatted">(define s (string-match "[0-9][0-9][0-9][0-9]" "blah2002foo"))
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(match:suffix s)
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⇒ "foo"
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</pre></div>
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<dl class="first-deffn">
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<dt class="deffn" id="index-match_003acount"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">match:count</strong> <var class="def-var-arguments">match</var><a class="copiable-link" href="#index-match_003acount"> ¶</a></span></dt>
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<dd><p>Return the number of parenthesized subexpressions from <var class="var">match</var>.
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Note that the entire regular expression match itself counts as a
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subexpression, and failed submatches are included in the count.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-match_003astring"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">match:string</strong> <var class="def-var-arguments">match</var><a class="copiable-link" href="#index-match_003astring"> ¶</a></span></dt>
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<dd><p>Return the original <var class="var">target</var> string.
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</p></dd></dl>
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<div class="example lisp">
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<pre class="lisp-preformatted">(define s (string-match "[0-9][0-9][0-9][0-9]" "blah2002foo"))
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(match:string s)
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⇒ "blah2002foo"
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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="Backslash-Escapes.html">Backslash Escapes</a>, Previous: <a href="Regexp-Functions.html">Regexp Functions</a>, Up: <a href="Regular-Expressions.html">Regular Expressions</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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