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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Returns true if the given character can be escaped in a regex."><title>is_escapeable_character in regex_syntax - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><link rel="stylesheet" href="../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../static.files/rustdoc-ac92e1bbe349e143.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="regex_syntax" data-themes="" data-resource-suffix="" data-rustdoc-version="1.76.0 (07dca489a 2024-02-04)" data-channel="1.76.0" data-search-js="search-2b6ce74ff89ae146.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../static.files/storage-f2adc0d6ca4d09fb.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-305769736d49e732.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-feafe1bb7466e4bd.css"></noscript><link rel="alternate icon" type="image/png" href="../static.files/favicon-16x16-8b506e7a72182f1c.png"><link rel="alternate icon" type="image/png" href="../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc fn"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">&#9776;</button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../regex_syntax/index.html">regex_syntax</a><span class="version">0.8.2</span></h2></div><div class="sidebar-elems"></div></nav><div class="sidebar-resizer"></div>
<main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><div id="sidebar-button" tabindex="-1"><a href="../regex_syntax/all.html" title="show sidebar"></a></div><input class="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"><div id="help-button" tabindex="-1"><a href="../help.html" title="help">?</a></div><div id="settings-menu" tabindex="-1"><a href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1>Function <a href="index.html">regex_syntax</a>::<wbr><a class="fn" href="#">is_escapeable_character</a><button id="copy-path" title="Copy item path to clipboard"><img src="../static.files/clipboard-7571035ce49a181d.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="src" href="../src/regex_syntax/lib.rs.html#303-331">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>&#x2212;</span>]</button></span></div><pre class="rust item-decl"><code>pub fn is_escapeable_character(c: <a class="primitive" href="https://doc.rust-lang.org/1.76.0/std/primitive.char.html">char</a>) -&gt; <a class="primitive" href="https://doc.rust-lang.org/1.76.0/std/primitive.bool.html">bool</a></code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Returns true if the given character can be escaped in a regex.</p>
<p>This returns true in all cases that <code>is_meta_character</code> returns true, but
also returns true in some cases where <code>is_meta_character</code> returns false.
For example, <code>%</code> is not a meta character, but it is escapeable. That is,
<code>%</code> and <code>\%</code> both match a literal <code>%</code> in all contexts.</p>
<p>The purpose of this routine is to provide knowledge about what characters
may be escaped. Namely, most regex engines permit “superfluous” escapes
where characters without any special significance may be escaped even
though there is no actual <em>need</em> to do so.</p>
<p>This will return false for some characters. For example, <code>e</code> is not
escapeable. Therefore, <code>\e</code> will either result in a parse error (which is
true today), or it could backwards compatibly evolve into a new construct
with its own meaning. Indeed, that is the purpose of banning <em>some</em>
superfluous escapes: it provides a way to evolve the syntax in a compatible
manner.</p>
<h2 id="example"><a href="#example">Example</a></h2>
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>regex_syntax::is_escapeable_character;
<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'?'</span>));
<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'-'</span>));
<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'&amp;'</span>));
<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'#'</span>));
<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'%'</span>));
<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'/'</span>));
<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'!'</span>));
<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'"'</span>));
<span class="macro">assert!</span>(!is_escapeable_character(<span class="string">'e'</span>));</code></pre></div>
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