<!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="Returns true if the given character has significance in a regex."><title>is_meta_character in regex_syntax - 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-5bc39a1768837dd0.css"><metaname="rustdoc-vars"data-root-path="../"data-static-root-path="../static.files/"data-current-crate="regex_syntax"data-themes=""data-resource-suffix=""data-rustdoc-version="1.77.1 (7cf61ebde 2024-03-27)"data-channel="1.77.1"data-search-js="search-dd67cee4cfa65049.js"data-settings-js="settings-4313503d2e1961c2.js"><scriptsrc="../static.files/storage-4c98445ec4002617.js"></script><scriptdefersrc="sidebar-items.js"></script><scriptdefersrc="../static.files/main-48f368f3872407c8.js"></script><noscript><linkrel="stylesheet"href="../static.files/noscript-04d5337699b92874.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 fn"><!--[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"title="show sidebar"></button></nav><navclass="sidebar"><divclass="sidebar-crate"><h2><ahref="../regex_syntax/index.html">regex_syntax</a><spanclass="version">0.8.3</span></h2></div><divclass="sidebar-elems"></div></nav><divclass="sidebar-resizer"></div>
<main><divclass="width-limiter"><navclass="sub"><formclass="search-form"><span></span><divid="sidebar-button"tabindex="-1"><ahref="../regex_syntax/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>Function <ahref="index.html">regex_syntax</a>::<wbr><aclass="fn"href="#">is_meta_character</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_syntax/lib.rs.html#260-266">source</a> · <buttonid="toggle-all-docs"title="collapse all docs">[<span>−</span>]</button></span></div><preclass="rust item-decl"><code>pub fn is_meta_character(c: <aclass="primitive"href="https://doc.rust-lang.org/1.77.1/std/primitive.char.html">char</a>) -><aclass="primitive"href="https://doc.rust-lang.org/1.77.1/std/primitive.bool.html">bool</a></code></pre><detailsclass="toggle top-doc"open><summaryclass="hideme"><span>Expand description</span></summary><divclass="docblock"><p>Returns true if the given character has significance in a regex.</p>
<p>Generally speaking, these are the only characters which <em>must</em> be escaped
in order to match their literal meaning. For example, to match a literal
<code>|</code>, one could write <code>\|</code>. Sometimes escaping isn’t always necessary. For
example, <code>-</code> is treated as a meta character because of its significance
for writing ranges inside of character classes, but the regex <code>-</code> will
match a literal <code>-</code> because <code>-</code> has no special meaning outside of character
classes.</p>
<p>In order to determine whether a character may be escaped at all, the
<ahref="fn.is_escapeable_character.html"title="fn regex_syntax::is_escapeable_character"><code>is_escapeable_character</code></a> routine should be used. The difference between
<code>is_meta_character</code> and <code>is_escapeable_character</code> is that the latter will
return true for some characters that are <em>not</em> meta characters. For
example, <code>%</code> and <code>\%</code> both match a literal <code>%</code> in all contexts. In other
words, <code>is_escapeable_character</code> includes “superfluous” escapes.</p>
<p>Note that the set of characters for which this function returns <code>true</code> or
<code>false</code> is fixed and won’t change in a semver compatible release. (In this
case, “semver compatible release” actually refers to the <code>regex</code> crate
itself, since reducing or expanding the set of meta characters would be a
breaking change for not just <code>regex-syntax</code> but also <code>regex</code> itself.)</p>
