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<section id='main' class="content struct">
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<h1 class='fqn'><span class='in-band'>Struct <a href='index.html'>regex</a>::<wbr><a class='struct' href=''>RegexSet</a></span><span class='out-of-band'><span id='render-detail'>
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[<span class='inner'>−</span>]
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</span><a id='src-4254' class='srclink' href='../src/regex/set.rs.html#113' title='goto source code'>[src]</a></span></h1>
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<pre class='rust struct'>pub struct RegexSet(_);</pre><div class='docblock'><p>Match multiple (possibly overlapping) regular expressions in a single scan.</p>
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<p>A regex set corresponds to the union of two or more regular expressions.
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That is, a regex set will match text where at least one of its
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constituent regular expressions matches. A regex set as its formulated here
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provides a touch more power: it will also report <em>which</em> regular
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expressions in the set match. Indeed, this is the key difference between
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regex sets and a single <code>Regex</code> with many alternates, since only one
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alternate can match at a time.</p>
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<p>For example, consider regular expressions to match email addresses and
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domains: <code>[a-z]+@[a-z]+\.(com|org|net)</code> and <code>[a-z]+\.(com|org|net)</code>. If a
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regex set is constructed from those regexes, then searching the text
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<code>foo@example.com</code> will report both regexes as matching. Of course, one
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could accomplish this by compiling each regex on its own and doing two
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searches over the text. The key advantage of using a regex set is that it
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will report the matching regexes using a <em>single pass through the text</em>.
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If one has hundreds or thousands of regexes to match repeatedly (like a URL
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router for a complex web application or a user agent matcher), then a regex
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set can realize huge performance gains.</p>
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<h1 id='example' class='section-header'><a href='#example'>Example</a></h1>
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<p>This shows how the above two regexes (for matching email addresses and
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domains) might work:</p>
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<pre class='rust rust-example-rendered'>
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<span class='kw'>let</span> <span class='ident'>set</span> <span class='op'>=</span> <span class='ident'>RegexSet</span>::<span class='ident'>new</span>(<span class='kw-2'>&</span>[
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<span class='string'>r"[a-z]+@[a-z]+\.(com|org|net)"</span>,
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<span class='string'>r"[a-z]+\.(com|org|net)"</span>,
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]).<span class='ident'>unwrap</span>();
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<span class='comment'>// Ask whether any regexes in the set match.</span>
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<span class='macro'>assert</span><span class='macro'>!</span>(<span class='ident'>set</span>.<span class='ident'>is_match</span>(<span class='string'>"foo@example.com"</span>));
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<span class='comment'>// Identify which regexes in the set match.</span>
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<span class='kw'>let</span> <span class='ident'>matches</span>: <span class='ident'>Vec</span><span class='op'><</span>_<span class='op'>></span> <span class='op'>=</span> <span class='ident'>set</span>.<span class='ident'>matches</span>(<span class='string'>"foo@example.com"</span>).<span class='ident'>into_iter</span>().<span class='ident'>collect</span>();
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<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='macro'>vec</span><span class='macro'>!</span>[<span class='number'>0</span>, <span class='number'>1</span>], <span class='ident'>matches</span>);
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<span class='comment'>// Try again, but with text that only matches one of the regexes.</span>
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<span class='kw'>let</span> <span class='ident'>matches</span>: <span class='ident'>Vec</span><span class='op'><</span>_<span class='op'>></span> <span class='op'>=</span> <span class='ident'>set</span>.<span class='ident'>matches</span>(<span class='string'>"example.com"</span>).<span class='ident'>into_iter</span>().<span class='ident'>collect</span>();
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<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='macro'>vec</span><span class='macro'>!</span>[<span class='number'>1</span>], <span class='ident'>matches</span>);
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<span class='comment'>// Try again, but with text that doesn't match any regex in the set.</span>
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<span class='kw'>let</span> <span class='ident'>matches</span>: <span class='ident'>Vec</span><span class='op'><</span>_<span class='op'>></span> <span class='op'>=</span> <span class='ident'>set</span>.<span class='ident'>matches</span>(<span class='string'>"example"</span>).<span class='ident'>into_iter</span>().<span class='ident'>collect</span>();
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<span class='macro'>assert</span><span class='macro'>!</span>(<span class='ident'>matches</span>.<span class='ident'>is_empty</span>());</pre>
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<p>Note that it would be possible to adapt the above example to using <code>Regex</code>
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with an expression like:</p>
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<pre class='rust rust-example-rendered'>
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(?<span class='ident'>P</span><span class='op'><</span><span class='ident'>email</span><span class='op'>></span>[<span class='ident'>a</span><span class='op'>-</span><span class='ident'>z</span>]<span class='op'>+</span><span class='kw-2'>@</span>(?<span class='ident'>P</span><span class='op'><</span><span class='ident'>email_domain</span><span class='op'>></span>[<span class='ident'>a</span><span class='op'>-</span><span class='ident'>z</span>]<span class='op'>+</span>[.](<span class='ident'>com</span><span class='op'>|</span><span class='ident'>org</span><span class='op'>|</span><span class='ident'>net</span>)))<span class='op'>|</span>(?<span class='ident'>P</span><span class='op'><</span><span class='ident'>domain</span><span class='op'>></span>[<span class='ident'>a</span><span class='op'>-</span><span class='ident'>z</span>]<span class='op'>+</span>[.](<span class='ident'>com</span><span class='op'>|</span><span class='ident'>org</span><span class='op'>|</span><span class='ident'>net</span>))</pre>
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<p>After a match, one could then inspect the capture groups to figure out
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which alternates matched. The problem is that it is hard to make this
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approach scale when there are many regexes since the overlap between each
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alternate isn't always obvious to reason about.</p>
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<h1 id='limitations' class='section-header'><a href='#limitations'>Limitations</a></h1>
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<p>Regex sets are limited to answering the following two questions:</p>
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<ol>
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<li>Does any regex in the set match?</li>
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<li>If so, which regexes in the set match?</li>
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</ol>
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<p>As with the main <code>Regex</code> type, it is cheaper to ask (1) instead of (2)
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since the matching engines can stop after the first match is found.</p>
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<p>Other features like finding the location of successive matches or their
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sub-captures aren't supported. If you need this functionality, the
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recommended approach is to compile each regex in the set independently and
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selectively match them based on which regexes in the set matched.</p>
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<h1 id='performance' class='section-header'><a href='#performance'>Performance</a></h1>
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<p>A <code>RegexSet</code> has the same performance characteristics as <code>Regex</code>. Namely,
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search takes <code>O(mn)</code> time, where <code>m</code> is proportional to the size of the
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regex set and <code>n</code> is proportional to the length of the search text.</p>
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</div><h2 id='methods'>Methods</h2><h3 class='impl'><code>impl <a class='struct' href='../regex/struct.RegexSet.html' title='regex::RegexSet'>RegexSet</a></code></h3><div class='impl-items'><h4 id='method.new' class='method'><code>fn <a href='#method.new' class='fnname'>new</a><I, S>(exprs: I) -> <a class='enum' href='https://doc.rust-lang.org/nightly/core/result/enum.Result.html' title='core::result::Result'>Result</a><<a class='struct' href='../regex/struct.RegexSet.html' title='regex::RegexSet'>RegexSet</a>, <a class='enum' href='../regex/enum.Error.html' title='regex::Error'>Error</a>> <span class='where'>where S: <a class='trait' href='https://doc.rust-lang.org/nightly/core/convert/trait.AsRef.html' title='core::convert::AsRef'>AsRef</a><<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>>, I: <a class='trait' href='https://doc.rust-lang.org/nightly/core/iter/trait.IntoIterator.html' title='core::iter::IntoIterator'>IntoIterator</a><Item=S></span></code></h4>
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<div class='docblock'><p>Create a new regex set with the given regular expressions.</p>
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<p>This takes an iterator of <code>S</code>, where <code>S</code> is something that can produce
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a <code>&str</code>. If any of the strings in the iterator are not valid regular
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expressions, then an error is returned.</p>
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<h1 id='example-1' class='section-header'><a href='#example-1'>Example</a></h1>
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<p>Create a new regex set from an iterator of strings:</p>
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<pre class='rust rust-example-rendered'>
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<span class='kw'>let</span> <span class='ident'>set</span> <span class='op'>=</span> <span class='ident'>RegexSet</span>::<span class='ident'>new</span>(<span class='kw-2'>&</span>[<span class='string'>r"\w+"</span>, <span class='string'>r"\d+"</span>]).<span class='ident'>unwrap</span>();
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<span class='macro'>assert</span><span class='macro'>!</span>(<span class='ident'>set</span>.<span class='ident'>is_match</span>(<span class='string'>"foo"</span>));</pre>
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</div><h4 id='method.is_match' class='method'><code>fn <a href='#method.is_match' class='fnname'>is_match</a>(&self, text: &<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -> <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.bool.html'>bool</a></code></h4>
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<div class='docblock'><p>Returns true if and only if one of the regexes in this set matches
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the text given.</p>
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<p>This method should be preferred if you only need to test whether any
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of the regexes in the set should match, but don't care about <em>which</em>
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regexes matched. This is because the underlying matching engine will
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quit immediately after seeing the first match instead of continuing to
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find all matches.</p>
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<p>Note that as with searches using <code>Regex</code>, the expression is unanchored
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by default. That is, if the regex does not start with <code>^</code> or <code>\A</code>, or
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end with <code>$</code> or <code>\z</code>, then it is permitted to match anywhere in the
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text.</p>
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<h1 id='example-2' class='section-header'><a href='#example-2'>Example</a></h1>
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<p>Tests whether a set matches some text:</p>
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<pre class='rust rust-example-rendered'>
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<span class='kw'>let</span> <span class='ident'>set</span> <span class='op'>=</span> <span class='ident'>RegexSet</span>::<span class='ident'>new</span>(<span class='kw-2'>&</span>[<span class='string'>r"\w+"</span>, <span class='string'>r"\d+"</span>]).<span class='ident'>unwrap</span>();
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<span class='macro'>assert</span><span class='macro'>!</span>(<span class='ident'>set</span>.<span class='ident'>is_match</span>(<span class='string'>"foo"</span>));
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<span class='macro'>assert</span><span class='macro'>!</span>(<span class='op'>!</span><span class='ident'>set</span>.<span class='ident'>is_match</span>(<span class='string'>"☃"</span>));</pre>
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</div><h4 id='method.matches' class='method'><code>fn <a href='#method.matches' class='fnname'>matches</a>(&self, text: &<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.str.html'>str</a>) -> <a class='struct' href='../regex/struct.SetMatches.html' title='regex::SetMatches'>SetMatches</a></code></h4>
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<div class='docblock'><p>Returns the set of regular expressions that match in the given text.</p>
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<p>The set returned contains the index of each regular expression that
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matches in the given text. The index is in correspondence with the
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order of regular expressions given to <code>RegexSet</code>'s constructor.</p>
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<p>The set can also be used to iterate over the matched indices.</p>
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<p>Note that as with searches using <code>Regex</code>, the expression is unanchored
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by default. That is, if the regex does not start with <code>^</code> or <code>\A</code>, or
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end with <code>$</code> or <code>\z</code>, then it is permitted to match anywhere in the
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text.</p>
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<h1 id='example-3' class='section-header'><a href='#example-3'>Example</a></h1>
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<p>Tests which regular expressions match the given text:</p>
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<pre class='rust rust-example-rendered'>
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<span class='kw'>let</span> <span class='ident'>set</span> <span class='op'>=</span> <span class='ident'>RegexSet</span>::<span class='ident'>new</span>(<span class='kw-2'>&</span>[
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<span class='string'>r"\w+"</span>,
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<span class='string'>r"\d+"</span>,
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<span class='string'>r"\pL+"</span>,
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<span class='string'>r"foo"</span>,
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<span class='string'>r"bar"</span>,
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<span class='string'>r"barfoo"</span>,
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<span class='string'>r"foobar"</span>,
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]).<span class='ident'>unwrap</span>();
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<span class='kw'>let</span> <span class='ident'>matches</span>: <span class='ident'>Vec</span><span class='op'><</span>_<span class='op'>></span> <span class='op'>=</span> <span class='ident'>set</span>.<span class='ident'>matches</span>(<span class='string'>"foobar"</span>).<span class='ident'>into_iter</span>().<span class='ident'>collect</span>();
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<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>matches</span>, <span class='macro'>vec</span><span class='macro'>!</span>[<span class='number'>0</span>, <span class='number'>2</span>, <span class='number'>3</span>, <span class='number'>4</span>, <span class='number'>6</span>]);
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<span class='comment'>// You can also test whether a particular regex matched:</span>
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<span class='kw'>let</span> <span class='ident'>matches</span> <span class='op'>=</span> <span class='ident'>set</span>.<span class='ident'>matches</span>(<span class='string'>"foobar"</span>);
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<span class='macro'>assert</span><span class='macro'>!</span>(<span class='op'>!</span><span class='ident'>matches</span>.<span class='ident'>matched</span>(<span class='number'>5</span>));
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<span class='macro'>assert</span><span class='macro'>!</span>(<span class='ident'>matches</span>.<span class='ident'>matched</span>(<span class='number'>6</span>));</pre>
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</div><h4 id='method.len' class='method'><code>fn <a href='#method.len' class='fnname'>len</a>(&self) -> <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.usize.html'>usize</a></code></h4>
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<div class='docblock'><p>Returns the total number of regular expressions in this set.</p>
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</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.Debug.html' title='core::fmt::Debug'>Debug</a> for <a class='struct' href='../regex/struct.RegexSet.html' title='regex::RegexSet'>RegexSet</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.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&self, f: &mut <a class='struct' href='https://doc.rust-lang.org/nightly/core/fmt/struct.Formatter.html' title='core::fmt::Formatter'>Formatter</a>) -> <a class='type' href='https://doc.rust-lang.org/nightly/core/fmt/type.Result.html' title='core::fmt::Result'>Result</a></code></h4>
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</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='struct' href='../regex/struct.RegexSet.html' title='regex::RegexSet'>RegexSet</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#tymethod.clone' class='fnname'>clone</a>(&self) -> <a class='struct' href='../regex/struct.RegexSet.html' title='regex::RegexSet'>RegexSet</a></code></h4>
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<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>(&mut self, source: &Self)</code></h4>
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