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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-5bc39a1768837dd0.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="1.77.0 (aedd173a2 2024-03-17)" data-channel="1.77.0" data-search-js="search-dd67cee4cfa65049.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../static.files/storage-4c98445ec4002617.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-48f368f3872407c8.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-04d5337699b92874.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" title="show sidebar"></button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../regex_syntax/index.html">regex_syntax</a><span class="version">0.8.3</span></h2></div><div class="sidebar-elems"></div></nav><div class="sidebar-resizer"></div>
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<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>−</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/1.77.0/std/primitive.char.html">char</a>) -> <a class="primitive" href="https://doc.rust-lang.org/1.77.0/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>
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<p>This returns true in all cases that <code>is_meta_character</code> returns true, but
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also returns true in some cases where <code>is_meta_character</code> returns false.
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For example, <code>%</code> is not a meta character, but it is escapeable. That is,
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<code>%</code> and <code>\%</code> both match a literal <code>%</code> in all contexts.</p>
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<p>The purpose of this routine is to provide knowledge about what characters
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may be escaped. Namely, most regex engines permit “superfluous” escapes
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where characters without any special significance may be escaped even
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though there is no actual <em>need</em> to do so.</p>
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<p>This will return false for some characters. For example, <code>e</code> is not
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escapeable. Therefore, <code>\e</code> will either result in a parse error (which is
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true today), or it could backwards compatibly evolve into a new construct
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with its own meaning. Indeed, that is the purpose of banning <em>some</em>
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superfluous escapes: it provides a way to evolve the syntax in a compatible
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manner.</p>
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<h2 id="example"><a class="doc-anchor" href="#example">§</a>Example</h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>regex_syntax::is_escapeable_character;
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<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'?'</span>));
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<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'-'</span>));
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<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'&'</span>));
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<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'#'</span>));
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<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'%'</span>));
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<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'/'</span>));
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<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'!'</span>));
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<span class="macro">assert!</span>(is_escapeable_character(<span class="string">'"'</span>));
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<span class="macro">assert!</span>(!is_escapeable_character(<span class="string">'e'</span>));</code></pre></div>
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