<!DOCTYPE html><htmllang="en"><head><metacharset="utf-8"><metaname="viewport"content="width=device-width, initial-scale=1.0"><metaname="generator"content="rustdoc"><metaname="description"content="Provides routines for interpolating capture group references."><title>regex_automata::util::interpolate - Rust</title><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><linkrel="stylesheet"href="../../../static.files/normalize-76eba96aa4d2e634.css"><linkrel="stylesheet"href="../../../static.files/rustdoc-ac92e1bbe349e143.css"><metaname="rustdoc-vars"data-root-path="../../../"data-static-root-path="../../../static.files/"data-current-crate="regex_automata"data-themes=""data-resource-suffix=""data-rustdoc-version="1.76.0 (07dca489a 2024-02-04)"data-channel="1.76.0"data-search-js="search-2b6ce74ff89ae146.js"data-settings-js="settings-4313503d2e1961c2.js"><scriptsrc="../../../static.files/storage-f2adc0d6ca4d09fb.js"></script><scriptdefersrc="../sidebar-items.js"></script><scriptdefersrc="../../../static.files/main-305769736d49e732.js"></script><noscript><linkrel="stylesheet"href="../../../static.files/noscript-feafe1bb7466e4bd.css"></noscript><linkrel="alternate icon"type="image/png"href="../../../static.files/favicon-16x16-8b506e7a72182f1c.png"><linkrel="alternate icon"type="image/png"href="../../../static.files/favicon-32x32-422f7d1d52889060.png"><linkrel="icon"type="image/svg+xml"href="../../../static.files/favicon-2c020d218678b618.svg"></head><bodyclass="rustdoc mod"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><navclass="mobile-topbar"><buttonclass="sidebar-menu-toggle">☰</button></nav><navclass="sidebar"><divclass="sidebar-crate"><h2><ahref="../../../regex_automata/index.html">regex_automata</a><spanclass="version">0.4.6</span></h2></div><h2class="location"><ahref="#">Module interpolate</a></h2><divclass="sidebar-elems"><section><ulclass="block"><li><ahref="#functions">Functions</a></li></ul></section><h2><ahref="../index.html">In regex_automata::util</a></h2></div></nav><divclass="sidebar-resizer"></div>
<main><divclass="width-limiter"><navclass="sub"><formclass="search-form"><span></span><divid="sidebar-button"tabindex="-1"><ahref="../../../regex_automata/all.html"title="show sidebar"></a></div><inputclass="search-input"name="search"aria-label="Run search in the documentation"autocomplete="off"spellcheck="false"placeholder="Click or press ‘S’ to search, ‘?’ for more options…"type="search"><divid="help-button"tabindex="-1"><ahref="../../../help.html"title="help">?</a></div><divid="settings-menu"tabindex="-1"><ahref="../../../settings.html"title="settings"><imgwidth="22"height="22"alt="Change settings"src="../../../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><sectionid="main-content"class="content"><divclass="main-heading"><h1>Module <ahref="../../index.html">regex_automata</a>::<wbr><ahref="../index.html">util</a>::<wbr><aclass="mod"href="#">interpolate</a><buttonid="copy-path"title="Copy item path to clipboard"><imgsrc="../../../static.files/clipboard-7571035ce49a181d.svg"width="19"height="18"alt="Copy item path"></button></h1><spanclass="out-of-band"><aclass="src"href="../../../src/regex_automata/util/interpolate.rs.html#1-579">source</a> · <buttonid="toggle-all-docs"title="collapse all docs">[<span>−</span>]</button></span></div><detailsclass="toggle top-doc"open><summaryclass="hideme"><span>Expand description</span></summary><divclass="docblock"><p>Provides routines for interpolating capture group references.</p>
<p>That is, if a replacement string contains references like <code>$foo</code> or <code>${foo1}</code>,
then they are replaced with the corresponding capture values for the groups
named <code>foo</code> and <code>foo1</code>, respectively. Similarly, syntax like <code>$1</code> and <code>${1}</code>
is supported as well, with <code>1</code> corresponding to a capture group index and not
a name.</p>
<p>This module provides the free functions <ahref="fn.string.html"title="fn regex_automata::util::interpolate::string"><code>string</code></a> and <ahref="fn.bytes.html"title="fn regex_automata::util::interpolate::bytes"><code>bytes</code></a>, which
interpolate Rust Unicode strings and byte strings, respectively.</p>
<h2id="format"><ahref="#format">Format</a></h2>
<p>These routines support two different kinds of capture references: unbraced and
braced.</p>
<p>For the unbraced format, the format supported is <code>$ref</code> where <code>name</code> can be
any character in the class <code>[0-9A-Za-z_]</code>. <code>ref</code> is always the longest
possible parse. So for example, <code>$1a</code> corresponds to the capture group named
<code>1a</code> and not the capture group at index <code>1</code>. If <code>ref</code> matches <code>^[0-9]+$</code>, then
it is treated as a capture group index itself and not a name.</p>
<p>For the braced format, the format supported is <code>${ref}</code> where <code>ref</code> can be any
sequence of bytes except for <code>}</code>. If no closing brace occurs, then it is not
considered a capture reference. As with the unbraced format, if <code>ref</code> matches
<code>^[0-9]+$</code>, then it is treated as a capture group index and not a name.</p>
<p>The braced format is useful for exerting precise control over the name of the
capture reference. For example, <code>${1}a</code> corresponds to the capture group
reference <code>1</code> followed by the letter <code>a</code>, where as <code>$1a</code> (as mentioned above)
corresponds to the capture group reference <code>1a</code>. The braced format is also
useful for expressing capture group names that use characters not supported by
the unbraced format. For example, <code>${foo[bar].baz}</code> refers to the capture group
named <code>foo[bar].baz</code>.</p>
<p>If a capture group reference is found and it does not refer to a valid capture
group, then it will be replaced with the empty string.</p>
<p>To write a literal <code>$</code>, use <code>$$</code>.</p>
<p>To be clear, and as exhibited via the type signatures in the routines in this
module, it is impossible for a replacement string to be invalid. A replacement
string may not have the intended semantics, but the interpolation procedure
itself can never fail.</p>
</div></details><h2id="functions"class="section-header"><ahref="#functions">Functions</a></h2><ulclass="item-table"><li><divclass="item-name"><aclass="fn"href="fn.bytes.html"title="fn regex_automata::util::interpolate::bytes">bytes</a></div><divclass="desc docblock-short">Accepts a replacement byte string and interpolates capture references with
their corresponding values.</div></li><li><divclass="item-name"><aclass="fn"href="fn.string.html"title="fn regex_automata::util::interpolate::string">string</a></div><divclass="desc docblock-short">Accepts a replacement string and interpolates capture references with their
