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<section id='main' class="content enum">
<h1 class='fqn'><span class='in-band'>Enum <a href='index.html'>regex</a>::<wbr><a class='enum' href=''>Regex</a></span><span class='out-of-band'><span id='render-detail'>
<a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">
[<span class='inner'>&#x2212;</span>]
</a>
</span><a id='src-2793' class='srclink' href='../src/regex/re.rs.html.html#168-178' title='goto source code'>[src]</a></span></h1>
<pre class='rust enum'>pub enum Regex {
// some variants omitted
}</pre><div class='docblock'><p>A compiled regular expression</p>
<p>It is represented as either a sequence of bytecode instructions (dynamic)
or as a specialized Rust function (native). It can be used to search, split
or replace text. All searching is done with an implicit <code>.*?</code> at the
beginning and end of an expression. To force an expression to match the
whole string (or a prefix or a suffix), you must use an anchor like <code>^</code> or
<code>$</code> (or <code>\A</code> and <code>\z</code>).</p>
<p>While this crate will handle Unicode strings (whether in the regular
expression or in the search text), all positions returned are <strong>byte
indices</strong>. Every byte index is guaranteed to be at a Unicode code point
boundary.</p>
<p>The lifetimes <code>&#39;r</code> and <code>&#39;t</code> in this crate correspond to the lifetime of a
compiled regular expression and text to search, respectively.</p>
<p>The only methods that allocate new strings are the string replacement
methods. All other methods (searching and splitting) return borrowed
pointers into the string given.</p>
<h1 id='examples' class='section-header'><a href='#examples'>Examples</a></h1>
<p>Find the location of a US phone number:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>&quot;[0-9]{3}-[0-9]{3}-[0-9]{4}&quot;</span>).<span class='ident'>unwrap</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>re</span>.<span class='ident'>find</span>(<span class='string'>&quot;phone: 111-222-3333&quot;</span>), <span class='prelude-val'>Some</span>((<span class='number'>7</span>, <span class='number'>19</span>)));</pre>
<h1 id='using-the-stdstrstrext-methods-with-regex' class='section-header'><a href='#using-the-stdstrstrext-methods-with-regex'>Using the <code>std::str::StrExt</code> methods with <code>Regex</code></a></h1>
<blockquote>
<p><strong>Note</strong>: This section requires that this crate is currently compiled with
the <code>pattern</code> Cargo feature enabled.</p>
</blockquote>
<p>Since <code>Regex</code> implements <code>Pattern</code>, you can use regexes with methods
defined on <code>std::str::StrExt</code>. For example, <code>is_match</code>, <code>find</code>, <code>find_iter</code>
and <code>split</code> can be replaced with <code>StrExt::contains</code>, <code>StrExt::find</code>,
<code>StrExt::match_indices</code> and <code>StrExt::split</code>.</p>
<p>Here are some examples:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r&quot;\d+&quot;</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>haystack</span> <span class='op'>=</span> <span class='string'>&quot;a111b222c&quot;</span>;
<span class='macro'>assert</span><span class='macro'>!</span>(<span class='ident'>haystack</span>.<span class='ident'>contains</span>(<span class='kw-2'>&amp;</span><span class='ident'>re</span>));
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>haystack</span>.<span class='ident'>find</span>(<span class='kw-2'>&amp;</span><span class='ident'>re</span>), <span class='prelude-val'>Some</span>(<span class='number'>1</span>));
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>haystack</span>.<span class='ident'>match_indices</span>(<span class='kw-2'>&amp;</span><span class='ident'>re</span>).<span class='ident'>collect</span>::<span class='op'>&lt;</span><span class='ident'>Vec</span><span class='op'>&lt;</span>_<span class='op'>&gt;&gt;</span>(),
<span class='macro'>vec</span><span class='macro'>!</span>[(<span class='number'>1</span>, <span class='number'>4</span>), (<span class='number'>5</span>, <span class='number'>8</span>)]);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>haystack</span>.<span class='ident'>split</span>(<span class='kw-2'>&amp;</span><span class='ident'>re</span>).<span class='ident'>collect</span>::<span class='op'>&lt;</span><span class='ident'>Vec</span><span class='op'>&lt;</span>_<span class='op'>&gt;&gt;</span>(), <span class='macro'>vec</span><span class='macro'>!</span>[<span class='string'>&quot;a&quot;</span>, <span class='string'>&quot;b&quot;</span>, <span class='string'>&quot;c&quot;</span>]);</pre>
</div><h2 id='methods'>Methods</h2><h3 class='impl'><code>impl <a class='enum' href='../regex/enum.Regex.html' title='regex::Regex'>Regex</a></code></h3><div class='impl-items'><h4 id='method.new' class='method'><code>fn <a href='#method.new' class='fnname'>new</a>(re: &amp;<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -&gt; <a class='enum' href='https://doc.rust-lang.org/nightly/core/result/enum.Result.html' title='core::result::Result'>Result</a>&lt;<a class='enum' href='../regex/enum.Regex.html' title='regex::Regex'>Regex</a>, <a class='enum' href='../regex/enum.Error.html' title='regex::Error'>Error</a>&gt;</code></h4>
<div class='docblock'><p>Compiles a dynamic regular expression. Once compiled, it can be
used repeatedly to search, split or replace text in a string.</p>
<p>If an invalid expression is given, then an error is returned.</p>
</div><h4 id='method.with_size_limit' class='method'><code>fn <a href='#method.with_size_limit' class='fnname'>with_size_limit</a>(size: <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.usize.html'>usize</a>, re: &amp;<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -&gt; <a class='enum' href='https://doc.rust-lang.org/nightly/core/result/enum.Result.html' title='core::result::Result'>Result</a>&lt;<a class='enum' href='../regex/enum.Regex.html' title='regex::Regex'>Regex</a>, <a class='enum' href='../regex/enum.Error.html' title='regex::Error'>Error</a>&gt;</code></h4>
<div class='docblock'><p>Compiles a dynamic regular expression with the given size limit.</p>
<p>The size limit is applied to the size of the <em>compiled</em> data structure.
If the data structure exceeds the size given, then an error is
returned.</p>
<p>The default size limit used in <code>new</code> is 10MB.</p>
</div><h4 id='method.is_match' class='method'><code>fn <a href='#method.is_match' class='fnname'>is_match</a>(&amp;self, text: &amp;<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -&gt; <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.bool.html'>bool</a></code></h4>
<div class='docblock'><p>Returns true if and only if the regex matches the string given.</p>
<h1 id='example' class='section-header'><a href='#example'>Example</a></h1>
<p>Test if some text contains at least one word with exactly 13
characters:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>text</span> <span class='op'>=</span> <span class='string'>&quot;I categorically deny having triskaidekaphobia.&quot;</span>;
<span class='macro'>assert</span><span class='macro'>!</span>(<span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r&quot;\b\w{13}\b&quot;</span>).<span class='ident'>unwrap</span>().<span class='ident'>is_match</span>(<span class='ident'>text</span>));</pre>
</div><h4 id='method.find' class='method'><code>fn <a href='#method.find' class='fnname'>find</a>(&amp;self, text: &amp;<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -&gt; <a class='enum' href='https://doc.rust-lang.org/nightly/core/option/enum.Option.html' title='core::option::Option'>Option</a>&lt;<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.tuple.html'>(</a><a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.usize.html'>usize</a>, <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.usize.html'>usize</a><a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.tuple.html'>)</a>&gt;</code></h4>
<div class='docblock'><p>Returns the start and end byte range of the leftmost-first match in
<code>text</code>. If no match exists, then <code>None</code> is returned.</p>
<p>Note that this should only be used if you want to discover the position
of the match. Testing the existence of a match is faster if you use
<code>is_match</code>.</p>
<h1 id='example-1' class='section-header'><a href='#example-1'>Example</a></h1>
<p>Find the start and end location of the first word with exactly 13
characters:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>text</span> <span class='op'>=</span> <span class='string'>&quot;I categorically deny having triskaidekaphobia.&quot;</span>;
<span class='kw'>let</span> <span class='ident'>pos</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r&quot;\b\w{13}\b&quot;</span>).<span class='ident'>unwrap</span>().<span class='ident'>find</span>(<span class='ident'>text</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>pos</span>, <span class='prelude-val'>Some</span>((<span class='number'>2</span>, <span class='number'>15</span>)));</pre>
</div><h4 id='method.find_iter' class='method'><code>fn <a href='#method.find_iter' class='fnname'>find_iter</a>&lt;'r, 't&gt;(&amp;'r self, text: &amp;'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -&gt; <a class='struct' href='../regex/struct.FindMatches.html' title='regex::FindMatches'>FindMatches</a>&lt;'r, 't&gt;</code></h4>
<div class='docblock'><p>Returns an iterator for each successive non-overlapping match in
<code>text</code>, returning the start and end byte indices with respect to
<code>text</code>.</p>
<h1 id='example-2' class='section-header'><a href='#example-2'>Example</a></h1>
<p>Find the start and end location of every word with exactly 13
characters:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>text</span> <span class='op'>=</span> <span class='string'>&quot;Retroactively relinquishing remunerations is reprehensible.&quot;</span>;
<span class='kw'>for</span> <span class='ident'>pos</span> <span class='kw'>in</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r&quot;\b\w{13}\b&quot;</span>).<span class='ident'>unwrap</span>().<span class='ident'>find_iter</span>(<span class='ident'>text</span>) {
<span class='macro'>println</span><span class='macro'>!</span>(<span class='string'>&quot;{:?}&quot;</span>, <span class='ident'>pos</span>);
}
<span class='comment'>// Output:</span>
<span class='comment'>// (0, 13)</span>
<span class='comment'>// (14, 27)</span>
<span class='comment'>// (28, 41)</span>
<span class='comment'>// (45, 58)</span></pre>
</div><h4 id='method.captures' class='method'><code>fn <a href='#method.captures' class='fnname'>captures</a>&lt;'t&gt;(&amp;self, text: &amp;'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -&gt; <a class='enum' href='https://doc.rust-lang.org/nightly/core/option/enum.Option.html' title='core::option::Option'>Option</a>&lt;<a class='struct' href='../regex/struct.Captures.html' title='regex::Captures'>Captures</a>&lt;'t&gt;&gt;</code></h4>
<div class='docblock'><p>Returns the capture groups corresponding to the leftmost-first
match in <code>text</code>. Capture group <code>0</code> always corresponds to the entire
match. If no match is found, then <code>None</code> is returned.</p>
<p>You should only use <code>captures</code> if you need access to submatches.
Otherwise, <code>find</code> is faster for discovering the location of the overall
match.</p>
<h1 id='examples-1' class='section-header'><a href='#examples-1'>Examples</a></h1>
<p>Say you have some text with movie names and their release years,
like &quot;&#39;Citizen Kane&#39; (1941)&quot;. It&#39;d be nice if we could search for text
looking like that, while also extracting the movie name and its release
year separately.</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r&quot;&#39;([^&#39;]+)&#39;\s+\((\d{4})\)&quot;</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>text</span> <span class='op'>=</span> <span class='string'>&quot;Not my favorite movie: &#39;Citizen Kane&#39; (1941).&quot;</span>;
<span class='kw'>let</span> <span class='ident'>caps</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>captures</span>(<span class='ident'>text</span>).<span class='ident'>unwrap</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>caps</span>.<span class='ident'>at</span>(<span class='number'>1</span>), <span class='prelude-val'>Some</span>(<span class='string'>&quot;Citizen Kane&quot;</span>));
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>caps</span>.<span class='ident'>at</span>(<span class='number'>2</span>), <span class='prelude-val'>Some</span>(<span class='string'>&quot;1941&quot;</span>));
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>caps</span>.<span class='ident'>at</span>(<span class='number'>0</span>), <span class='prelude-val'>Some</span>(<span class='string'>&quot;&#39;Citizen Kane&#39; (1941)&quot;</span>));
<span class='comment'>// You can also access the groups by index using the Index notation.</span>
<span class='comment'>// Note that this will panic on an invalid index.</span>
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&amp;</span><span class='ident'>caps</span>[<span class='number'>1</span>], <span class='string'>&quot;Citizen Kane&quot;</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&amp;</span><span class='ident'>caps</span>[<span class='number'>2</span>], <span class='string'>&quot;1941&quot;</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&amp;</span><span class='ident'>caps</span>[<span class='number'>0</span>], <span class='string'>&quot;&#39;Citizen Kane&#39; (1941)&quot;</span>);</pre>
<p>Note that the full match is at capture group <code>0</code>. Each subsequent
capture group is indexed by the order of its opening <code>(</code>.</p>
<p>We can make this example a bit clearer by using <em>named</em> capture groups:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r&quot;&#39;(?P&lt;title&gt;[^&#39;]+)&#39;\s+\((?P&lt;year&gt;\d{4})\)&quot;</span>)
.<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>text</span> <span class='op'>=</span> <span class='string'>&quot;Not my favorite movie: &#39;Citizen Kane&#39; (1941).&quot;</span>;
<span class='kw'>let</span> <span class='ident'>caps</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>captures</span>(<span class='ident'>text</span>).<span class='ident'>unwrap</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>caps</span>.<span class='ident'>name</span>(<span class='string'>&quot;title&quot;</span>), <span class='prelude-val'>Some</span>(<span class='string'>&quot;Citizen Kane&quot;</span>));
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>caps</span>.<span class='ident'>name</span>(<span class='string'>&quot;year&quot;</span>), <span class='prelude-val'>Some</span>(<span class='string'>&quot;1941&quot;</span>));
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>caps</span>.<span class='ident'>at</span>(<span class='number'>0</span>), <span class='prelude-val'>Some</span>(<span class='string'>&quot;&#39;Citizen Kane&#39; (1941)&quot;</span>));
<span class='comment'>// You can also access the groups by name using the Index notation.</span>
<span class='comment'>// Note that this will panic on an invalid group name.</span>
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&amp;</span><span class='ident'>caps</span>[<span class='string'>&quot;title&quot;</span>], <span class='string'>&quot;Citizen Kane&quot;</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&amp;</span><span class='ident'>caps</span>[<span class='string'>&quot;year&quot;</span>], <span class='string'>&quot;1941&quot;</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='kw-2'>&amp;</span><span class='ident'>caps</span>[<span class='number'>0</span>], <span class='string'>&quot;&#39;Citizen Kane&#39; (1941)&quot;</span>);
</pre>
<p>Here we name the capture groups, which we can access with the <code>name</code>
method or the <code>Index</code> notation with a <code>&amp;str</code>. Note that the named capture groups
are still accessible with <code>at</code> or the <code>Index</code> notation with a <code>usize</code>.</p>
<p>The <code>0</code>th capture group is always unnamed, so it must always be
accessed with <code>at(0)</code> or <code>[0]</code>.</p>
</div><h4 id='method.captures_iter' class='method'><code>fn <a href='#method.captures_iter' class='fnname'>captures_iter</a>&lt;'r, 't&gt;(&amp;'r self, text: &amp;'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -&gt; <a class='struct' href='../regex/struct.FindCaptures.html' title='regex::FindCaptures'>FindCaptures</a>&lt;'r, 't&gt;</code></h4>
<div class='docblock'><p>Returns an iterator over all the non-overlapping capture groups matched
in <code>text</code>. This is operationally the same as <code>find_iter</code> (except it
yields information about submatches).</p>
<h1 id='example-3' class='section-header'><a href='#example-3'>Example</a></h1>
<p>We can use this to find all movie titles and their release years in
some text, where the movie is formatted like &quot;&#39;Title&#39; (xxxx)&quot;:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r&quot;&#39;(?P&lt;title&gt;[^&#39;]+)&#39;\s+\((?P&lt;year&gt;\d{4})\)&quot;</span>)
.<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>text</span> <span class='op'>=</span> <span class='string'>&quot;&#39;Citizen Kane&#39; (1941), &#39;The Wizard of Oz&#39; (1939), &#39;M&#39; (1931).&quot;</span>;
<span class='kw'>for</span> <span class='ident'>caps</span> <span class='kw'>in</span> <span class='ident'>re</span>.<span class='ident'>captures_iter</span>(<span class='ident'>text</span>) {
<span class='macro'>println</span><span class='macro'>!</span>(<span class='string'>&quot;Movie: {:?}, Released: {:?}&quot;</span>, <span class='ident'>caps</span>.<span class='ident'>name</span>(<span class='string'>&quot;title&quot;</span>), <span class='ident'>caps</span>.<span class='ident'>name</span>(<span class='string'>&quot;year&quot;</span>));
}
<span class='comment'>// Output:</span>
<span class='comment'>// Movie: Citizen Kane, Released: 1941</span>
<span class='comment'>// Movie: The Wizard of Oz, Released: 1939</span>
<span class='comment'>// Movie: M, Released: 1931</span></pre>
</div><h4 id='method.split' class='method'><code>fn <a href='#method.split' class='fnname'>split</a>&lt;'r, 't&gt;(&amp;'r self, text: &amp;'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -&gt; <a class='struct' href='../regex/struct.RegexSplits.html' title='regex::RegexSplits'>RegexSplits</a>&lt;'r, 't&gt;</code></h4>
<div class='docblock'><p>Returns an iterator of substrings of <code>text</code> delimited by a match
of the regular expression.
Namely, each element of the iterator corresponds to text that <em>isn&#39;t</em>
matched by the regular expression.</p>
<p>This method will <em>not</em> copy the text given.</p>
<h1 id='example-4' class='section-header'><a href='#example-4'>Example</a></h1>
<p>To split a string delimited by arbitrary amounts of spaces or tabs:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r&quot;[ \t]+&quot;</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>fields</span>: <span class='ident'>Vec</span><span class='op'>&lt;</span><span class='kw-2'>&amp;</span><span class='ident'>str</span><span class='op'>&gt;</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>split</span>(<span class='string'>&quot;a b \t c\td e&quot;</span>).<span class='ident'>collect</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>fields</span>, <span class='macro'>vec</span><span class='macro'>!</span>(<span class='string'>&quot;a&quot;</span>, <span class='string'>&quot;b&quot;</span>, <span class='string'>&quot;c&quot;</span>, <span class='string'>&quot;d&quot;</span>, <span class='string'>&quot;e&quot;</span>));</pre>
</div><h4 id='method.splitn' class='method'><code>fn <a href='#method.splitn' class='fnname'>splitn</a>&lt;'r, 't&gt;(&amp;'r self, text: &amp;'t <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>, limit: <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.usize.html'>usize</a>) -&gt; <a class='struct' href='../regex/struct.RegexSplitsN.html' title='regex::RegexSplitsN'>RegexSplitsN</a>&lt;'r, 't&gt;</code></h4>
<div class='docblock'><p>Returns an iterator of at most <code>limit</code> substrings of <code>text</code> delimited
by a match of the regular expression. (A <code>limit</code> of <code>0</code> will return no
substrings.)
Namely, each element of the iterator corresponds to text that <em>isn&#39;t</em>
matched by the regular expression.
The remainder of the string that is not split will be the last element
in the iterator.</p>
<p>This method will <em>not</em> copy the text given.</p>
<h1 id='example-5' class='section-header'><a href='#example-5'>Example</a></h1>
<p>Get the first two words in some text:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r&quot;\W+&quot;</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>fields</span>: <span class='ident'>Vec</span><span class='op'>&lt;</span><span class='kw-2'>&amp;</span><span class='ident'>str</span><span class='op'>&gt;</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>splitn</span>(<span class='string'>&quot;Hey! How are you?&quot;</span>, <span class='number'>3</span>).<span class='ident'>collect</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>fields</span>, <span class='macro'>vec</span><span class='macro'>!</span>(<span class='string'>&quot;Hey&quot;</span>, <span class='string'>&quot;How&quot;</span>, <span class='string'>&quot;are you?&quot;</span>));</pre>
</div><h4 id='method.replace' class='method'><code>fn <a href='#method.replace' class='fnname'>replace</a>&lt;R: <a class='trait' href='../regex/trait.Replacer.html' title='regex::Replacer'>Replacer</a>&gt;(&amp;self, text: &amp;<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>, rep: R) -&gt; <a class='struct' href='https://doc.rust-lang.org/nightly/collections/string/struct.String.html' title='collections::string::String'>String</a></code></h4>
<div class='docblock'><p>Replaces the leftmost-first match with the replacement provided.
The replacement can be a regular string (where <code>$N</code> and <code>$name</code> are
expanded to match capture groups) or a function that takes the matches&#39;
<code>Captures</code> and returns the replaced string.</p>
<p>If no match is found, then a copy of the string is returned unchanged.</p>
<h1 id='examples-2' class='section-header'><a href='#examples-2'>Examples</a></h1>
<p>Note that this function is polymorphic with respect to the replacement.
In typical usage, this can just be a normal string:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>&quot;[^01]+&quot;</span>).<span class='ident'>unwrap</span>();
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>re</span>.<span class='ident'>replace</span>(<span class='string'>&quot;1078910&quot;</span>, <span class='string'>&quot;&quot;</span>), <span class='string'>&quot;1010&quot;</span>);</pre>
<p>But anything satisfying the <code>Replacer</code> trait will work. For example,
a closure of type <code>|&amp;Captures| -&gt; String</code> provides direct access to the
captures corresponding to a match. This allows one to access
submatches easily:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r&quot;([^,\s]+),\s+(\S+)&quot;</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>result</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>replace</span>(<span class='string'>&quot;Springsteen, Bruce&quot;</span>, <span class='op'>|</span><span class='ident'>caps</span>: <span class='kw-2'>&amp;</span><span class='ident'>Captures</span><span class='op'>|</span> {
<span class='macro'>format</span><span class='macro'>!</span>(<span class='string'>&quot;{} {}&quot;</span>, <span class='ident'>caps</span>.<span class='ident'>at</span>(<span class='number'>2</span>).<span class='ident'>unwrap_or</span>(<span class='string'>&quot;&quot;</span>), <span class='ident'>caps</span>.<span class='ident'>at</span>(<span class='number'>1</span>).<span class='ident'>unwrap_or</span>(<span class='string'>&quot;&quot;</span>))
});
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>result</span>, <span class='string'>&quot;Bruce Springsteen&quot;</span>);</pre>
<p>But this is a bit cumbersome to use all the time. Instead, a simple
syntax is supported that expands <code>$name</code> into the corresponding capture
group. Here&#39;s the last example, but using this expansion technique
with named capture groups:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r&quot;(?P&lt;last&gt;[^,\s]+),\s+(?P&lt;first&gt;\S+)&quot;</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>result</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>replace</span>(<span class='string'>&quot;Springsteen, Bruce&quot;</span>, <span class='string'>&quot;$first $last&quot;</span>);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>result</span>, <span class='string'>&quot;Bruce Springsteen&quot;</span>);</pre>
<p>Note that using <code>$2</code> instead of <code>$first</code> or <code>$1</code> instead of <code>$last</code>
would produce the same result. To write a literal <code>$</code> use <code>$$</code>.</p>
<p>Finally, sometimes you just want to replace a literal string with no
submatch expansion. This can be done by wrapping a string with
<code>NoExpand</code>:</p>
<pre class='rust rust-example-rendered'>
<span class='kw'>use</span> <span class='ident'>regex</span>::<span class='ident'>NoExpand</span>;
<span class='kw'>let</span> <span class='ident'>re</span> <span class='op'>=</span> <span class='ident'>Regex</span>::<span class='ident'>new</span>(<span class='string'>r&quot;(?P&lt;last&gt;[^,\s]+),\s+(\S+)&quot;</span>).<span class='ident'>unwrap</span>();
<span class='kw'>let</span> <span class='ident'>result</span> <span class='op'>=</span> <span class='ident'>re</span>.<span class='ident'>replace</span>(<span class='string'>&quot;Springsteen, Bruce&quot;</span>, <span class='ident'>NoExpand</span>(<span class='string'>&quot;$2 $last&quot;</span>));
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>result</span>, <span class='string'>&quot;$2 $last&quot;</span>);</pre>
</div><h4 id='method.replace_all' class='method'><code>fn <a href='#method.replace_all' class='fnname'>replace_all</a>&lt;R: <a class='trait' href='../regex/trait.Replacer.html' title='regex::Replacer'>Replacer</a>&gt;(&amp;self, text: &amp;<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>, rep: R) -&gt; <a class='struct' href='https://doc.rust-lang.org/nightly/collections/string/struct.String.html' title='collections::string::String'>String</a></code></h4>
<div class='docblock'><p>Replaces all non-overlapping matches in <code>text</code> with the
replacement provided. This is the same as calling <code>replacen</code> with
<code>limit</code> set to <code>0</code>.</p>
<p>See the documentation for <code>replace</code> for details on how to access
submatches in the replacement string.</p>
</div><h4 id='method.replacen' class='method'><code>fn <a href='#method.replacen' class='fnname'>replacen</a>&lt;R: <a class='trait' href='../regex/trait.Replacer.html' title='regex::Replacer'>Replacer</a>&gt;(&amp;self, text: &amp;<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>, limit: <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.usize.html'>usize</a>, rep: R) -&gt; <a class='struct' href='https://doc.rust-lang.org/nightly/collections/string/struct.String.html' title='collections::string::String'>String</a></code></h4>
<div class='docblock'><p>Replaces at most <code>limit</code> non-overlapping matches in <code>text</code> with the
replacement provided. If <code>limit</code> is 0, then all non-overlapping matches
are replaced.</p>
<p>See the documentation for <code>replace</code> for details on how to access
submatches in the replacement string.</p>
</div><h4 id='method.as_str' class='method'><code>fn <a href='#method.as_str' class='fnname'>as_str</a>(&amp;self) -&gt; &amp;<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a></code></h4>
<div class='docblock'><p>Returns the original string of this regex.</p>
</div><h4 id='method.capture_names' class='method'><code>fn <a href='#method.capture_names' class='fnname'>capture_names</a>(&amp;self) -&gt; <a class='enum' href='../regex/enum.CaptureNames.html' title='regex::CaptureNames'>CaptureNames</a></code></h4>
<div class='docblock'><p>Returns an iterator over the capture names.</p>
</div><h4 id='method.captures_len' class='method'><code>fn <a href='#method.captures_len' class='fnname'>captures_len</a>(&amp;self) -&gt; <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.usize.html'>usize</a></code></h4>
<div class='docblock'><p>Returns the number of captures.</p>
</div></div><h2 id='implementations'>Trait Implementations</h2><h3 class='impl'><code>impl <a class='trait' href='https://doc.rust-lang.org/nightly/core/fmt/trait.Display.html' title='core::fmt::Display'>Display</a> for <a class='enum' href='../regex/enum.Regex.html' title='regex::Regex'>Regex</a></code></h3><div class='impl-items'><h4 id='method.fmt' class='method'><code>fn <a href='https://doc.rust-lang.org/nightly/core/fmt/trait.Display.html#method.fmt' class='fnname'>fmt</a>(&amp;self, f: &amp;mut <a class='struct' href='https://doc.rust-lang.org/nightly/core/fmt/struct.Formatter.html' title='core::fmt::Formatter'>Formatter</a>) -&gt; <a class='type' href='https://doc.rust-lang.org/nightly/core/fmt/type.Result.html' title='core::fmt::Result'>Result</a></code></h4>
</div><h3 class='impl'><code>impl <a class='trait' href='https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html' title='core::fmt::Debug'>Debug</a> for <a class='enum' href='../regex/enum.Regex.html' title='regex::Regex'>Regex</a></code></h3><div class='impl-items'><h4 id='method.fmt-1' class='method'><code>fn <a href='https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html#method.fmt' class='fnname'>fmt</a>(&amp;self, f: &amp;mut <a class='struct' href='https://doc.rust-lang.org/nightly/core/fmt/struct.Formatter.html' title='core::fmt::Formatter'>Formatter</a>) -&gt; <a class='type' href='https://doc.rust-lang.org/nightly/core/fmt/type.Result.html' title='core::fmt::Result'>Result</a></code></h4>
</div><h3 class='impl'><code>impl <a class='trait' href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialEq.html' title='core::cmp::PartialEq'>PartialEq</a> for <a class='enum' href='../regex/enum.Regex.html' title='regex::Regex'>Regex</a></code></h3><div class='docblock'><p>Equality comparison is based on the original string. It is possible that
different regular expressions have the same matching behavior, but are
still compared unequal. For example, <code>\d+</code> and <code>\d\d*</code> match the same set
of strings, but are not considered equal.</p>
</div><div class='impl-items'><h4 id='method.eq' class='method'><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialEq.html#method.eq' class='fnname'>eq</a>(&amp;self, other: &amp;<a class='enum' href='../regex/enum.Regex.html' title='regex::Regex'>Regex</a>) -&gt; <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.bool.html'>bool</a></code></h4>
<h4 id='method.ne' class='method'><span class="since">1.0.0</span><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialEq.html#method.ne' class='fnname'>ne</a>(&amp;self, other: &amp;Rhs) -&gt; <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.bool.html'>bool</a></code></h4>
</div><h3 class='impl'><code>impl <a class='trait' href='https://doc.rust-lang.org/nightly/core/cmp/trait.Eq.html' title='core::cmp::Eq'>Eq</a> for <a class='enum' href='../regex/enum.Regex.html' title='regex::Regex'>Regex</a></code></h3><div class='impl-items'></div><h3 class='impl'><code>impl <a class='trait' href='https://doc.rust-lang.org/nightly/core/str/trait.FromStr.html' title='core::str::FromStr'>FromStr</a> for <a class='enum' href='../regex/enum.Regex.html' title='regex::Regex'>Regex</a></code></h3><div class='impl-items'><h4 id='associatedtype.Err' class='type'><code>type Err = <a class='enum' href='../regex/enum.Error.html' title='regex::Error'>Error</a></code></h4>
<h4 id='method.from_str' class='method'><code>fn <a href='https://doc.rust-lang.org/nightly/core/str/trait.FromStr.html#method.from_str' class='fnname'>from_str</a>(s: &amp;<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -&gt; <a class='enum' href='https://doc.rust-lang.org/nightly/core/result/enum.Result.html' title='core::result::Result'>Result</a>&lt;<a class='enum' href='../regex/enum.Regex.html' title='regex::Regex'>Regex</a>, <a class='enum' href='../regex/enum.Error.html' title='regex::Error'>Error</a>&gt;</code></h4>
</div><h3 id='derived_implementations'>Derived Implementations </h3><h3 class='impl'><code>impl <a class='trait' href='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html' title='core::clone::Clone'>Clone</a> for <a class='enum' href='../regex/enum.Regex.html' title='regex::Regex'>Regex</a></code></h3><div class='impl-items'><h4 id='method.clone' class='method'><code>fn <a href='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#method.clone' class='fnname'>clone</a>(&amp;self) -&gt; <a class='enum' href='../regex/enum.Regex.html' title='regex::Regex'>Regex</a></code></h4>
<h4 id='method.clone_from' class='method'><span class="since">1.0.0</span><code>fn <a href='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#method.clone_from' class='fnname'>clone_from</a>(&amp;mut self, source: &amp;Self)</code></h4>
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