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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="API documentation for the Rust `Scope` struct in crate `crossbeam`."><meta name="keywords" content="rust, rustlang, rust-lang, Scope"><title>crossbeam::Scope - Rust</title><link rel="stylesheet" type="text/css" href="../normalize.css"><link rel="stylesheet" type="text/css" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../dark.css"><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script src="../storage.js"></script></head><body class="rustdoc struct"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">&#9776;</div><p class='location'>Struct Scope</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#methods">Methods</a><div class="sidebar-links"><a href="#method.defer">defer</a><a href="#method.spawn">spawn</a><a href="#method.builder">builder</a></div><a class="sidebar-title" href="#implementations">Trait Implementations</a><div class="sidebar-links"><a href="#impl-Debug">Debug</a><a href="#impl-Drop">Drop</a></div><a class="sidebar-title" href="#synthetic-implementations">Auto Trait Implementations</a><div class="sidebar-links"><a href="#impl-Send">!Send</a><a href="#impl-Sync">!Sync</a></div></div><p class='location'><a href='index.html'>crossbeam</a></p><script>window.sidebarCurrent = {name: 'Scope', ty: 'struct', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../settings.html"><img src="../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='in-band'>Struct <a href='index.html'>crossbeam</a>::<wbr><a class="struct" href=''>Scope</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 class='srclink' href='../src/crossbeam/scoped.rs.html#13-15' title='goto source code'>[src]</a></span></h1><div class="docblock type-decl"><pre class='rust struct'>pub struct Scope&lt;'a&gt; { /* fields omitted */ }</pre></div>
                    <h2 id='methods' class='small-section-header'>
                      Methods<a href='#methods' class='anchor'></a>
                    </h2>
                <h3 id='impl' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;'a&gt; <a class="struct" href="../crossbeam/struct.Scope.html" title="struct crossbeam::Scope">Scope</a>&lt;'a&gt;</code><a href='#impl' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/crossbeam/scoped.rs.html#80-244' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.defer' class="method"><span id='defer.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.defer' class='fnname'>defer</a>&lt;F&gt;(&amp;self, f: F) <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>() + 'a,&nbsp;</span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/crossbeam/scoped.rs.html#107-113' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Schedule code to be executed when exiting the scope.</p>
<p>This is akin to having a destructor on the stack, except that it is
<em>guaranteed</em> to be run.</p>
</div><h4 id='method.spawn' class="method"><span id='spawn.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.spawn' class='fnname'>spawn</a>&lt;F, T&gt;(&amp;self, f: F) -&gt; <a class="struct" href="../crossbeam/struct.ScopedJoinHandle.html" title="struct crossbeam::ScopedJoinHandle">ScopedJoinHandle</a>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>() -&gt; T + <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> + 'a,<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> + 'a,&nbsp;</span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/crossbeam/scoped.rs.html#230-234' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Create a scoped thread.</p>
<p><code>spawn</code> is similar to the <a href="http://doc.rust-lang.org/std/thread/fn.spawn.html"><code>spawn</code></a> function in Rust's standard library. The
difference is that this thread is scoped, meaning that it's guaranteed to terminate
before the current stack frame goes away, allowing you to reference the parent stack frame
directly. This is ensured by having the parent thread join on the child thread before the
scope exits.</p>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<p>A basic scoped thread:</p>

<pre class="rust rust-example-rendered">
<span class="ident">crossbeam</span>::<span class="ident">scope</span>(<span class="op">|</span><span class="ident">scope</span><span class="op">|</span> {
    <span class="ident">scope</span>.<span class="ident">spawn</span>(<span class="op">||</span> {
        <span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;Hello from a scoped thread!&quot;</span>);
    });
});</pre>
<p>When writing concurrent Rust programs, you'll sometimes see a pattern like this, using
<a href="http://doc.rust-lang.org/std/thread/fn.spawn.html"><code>std::thread::spawn</code></a>:</p>

<div class='information'><div class='tooltip ignore'>ⓘ<span class='tooltiptext'>This example is not tested</span></div></div><pre class="rust rust-example-rendered ignore">
<span class="kw">let</span> <span class="ident">array</span> <span class="op">=</span> [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>];
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guards</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[];

<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="kw-2">&amp;</span><span class="ident">array</span> {
    <span class="kw">let</span> <span class="ident">guard</span> <span class="op">=</span> <span class="ident">std</span>::<span class="ident">thread</span>::<span class="ident">spawn</span>(<span class="kw">move</span> <span class="op">||</span> {
        <span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;element: {}&quot;</span>, <span class="ident">i</span>);
    });

    <span class="ident">guards</span>.<span class="ident">push</span>(<span class="ident">guard</span>);
}

<span class="kw">for</span> <span class="ident">guard</span> <span class="kw">in</span> <span class="ident">guards</span> {
    <span class="ident">guard</span>.<span class="ident">join</span>().<span class="ident">unwrap</span>();
}</pre>
<p>The basic pattern is:</p>
<ol>
<li>Iterate over some collection.</li>
<li>Spin up a thread to operate on each part of the collection.</li>
<li>Join all the threads.</li>
</ol>
<p>However, this code actually gives an error:</p>
<pre><code class="language-text">error: `array` does not live long enough
for i in &amp;array {
          ^~~~~
in expansion of for loop expansion
note: expansion site
note: reference must be valid for the static lifetime...
note: ...but borrowed value is only valid for the block suffix following statement 0 at ...
    let array = [1, 2, 3];
    let mut guards = vec![];

    for i in &amp;array {
        let guard = std::thread::spawn(move || {
            println!(&quot;element: {}&quot;, i);
...
error: aborting due to previous error
</code></pre>
<p>Because <a href="http://doc.rust-lang.org/std/thread/fn.spawn.html"><code>std::thread::spawn</code></a> doesn't know about this scope, it requires a
<code>'static</code> lifetime. One way of giving it a proper lifetime is to use an <a href="http://doc.rust-lang.org/stable/std/sync/struct.Arc.html"><code>Arc</code></a>:</p>

<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">Arc</span>;

<span class="kw">let</span> <span class="ident">array</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>([<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>]);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guards</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[];

<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">array</span>.<span class="ident">len</span>() {
    <span class="kw">let</span> <span class="ident">a</span> <span class="op">=</span> <span class="ident">array</span>.<span class="ident">clone</span>();

    <span class="kw">let</span> <span class="ident">guard</span> <span class="op">=</span> <span class="ident">std</span>::<span class="ident">thread</span>::<span class="ident">spawn</span>(<span class="kw">move</span> <span class="op">||</span> {
        <span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;element: {}&quot;</span>, <span class="ident">a</span>[<span class="ident">i</span>]);
    });

    <span class="ident">guards</span>.<span class="ident">push</span>(<span class="ident">guard</span>);
}

<span class="kw">for</span> <span class="ident">guard</span> <span class="kw">in</span> <span class="ident">guards</span> {
    <span class="ident">guard</span>.<span class="ident">join</span>().<span class="ident">unwrap</span>();
}</pre>
<p>But this introduces unnecessary allocation, as <code>Arc&lt;T&gt;</code> puts its data on the heap, and we
also end up dealing with reference counts. We know that we're joining the threads before
our function returns, so just taking a reference <em>should</em> be safe. Rust can't know that,
though.</p>
<p>Enter scoped threads. Here's our original example, using <code>spawn</code> from crossbeam rather
than from <code>std::thread</code>:</p>

<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">array</span> <span class="op">=</span> [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>];

<span class="ident">crossbeam</span>::<span class="ident">scope</span>(<span class="op">|</span><span class="ident">scope</span><span class="op">|</span> {
    <span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="kw-2">&amp;</span><span class="ident">array</span> {
        <span class="ident">scope</span>.<span class="ident">spawn</span>(<span class="kw">move</span> <span class="op">||</span> {
            <span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;element: {}&quot;</span>, <span class="ident">i</span>);
        });
    }
});</pre>
<p>Much more straightforward.</p>
</div><h4 id='method.builder' class="method"><span id='builder.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.builder' class='fnname'>builder</a>&lt;'s&gt;(&amp;'s self) -&gt; ScopedThreadBuilder&lt;'s, 'a&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/crossbeam/scoped.rs.html#238-243' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Generates the base configuration for spawning a scoped thread, from which configuration
methods can be chained.</p>
</div></div>
                <h2 id='implementations' class='small-section-header'>
                  Trait Implementations<a href='#implementations' class='anchor'></a>
                </h2>
                <div id='implementations-list'><h3 id='impl-Debug' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;'a&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html" title="trait core::fmt::Debug">Debug</a> for <a class="struct" href="../crossbeam/struct.Scope.html" title="struct crossbeam::Scope">Scope</a>&lt;'a&gt;</code><a href='#impl-Debug' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/crossbeam/scoped.rs.html#68-72' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.fmt' class="method"><span id='fmt.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html#tymethod.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="struct core::fmt::Formatter">Formatter</a>) -&gt; <a class="type" href="https://doc.rust-lang.org/nightly/core/fmt/type.Result.html" title="type core::fmt::Result">Result</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/crossbeam/scoped.rs.html#69-71' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Formats the value using the given formatter. <a href="https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html#tymethod.fmt">Read more</a></p>
</div></div><h3 id='impl-Drop' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;'a&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/drop/trait.Drop.html" title="trait core::ops::drop::Drop">Drop</a> for <a class="struct" href="../crossbeam/struct.Scope.html" title="struct crossbeam::Scope">Scope</a>&lt;'a&gt;</code><a href='#impl-Drop' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/crossbeam/scoped.rs.html#310-314' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.drop' class="method"><span id='drop.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/ops/drop/trait.Drop.html#tymethod.drop' class='fnname'>drop</a>(&amp;mut self)</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../src/crossbeam/scoped.rs.html#311-313' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Executes the destructor for this type. <a href="https://doc.rust-lang.org/nightly/core/ops/drop/trait.Drop.html#tymethod.drop">Read more</a></p>
</div></div></div>
                <h2 id='synthetic-implementations' class='small-section-header'>
                  Auto Trait Implementations<a href='#synthetic-implementations' class='anchor'></a>
                </h2>
                <div id='synthetic-implementations-list'>
            <h3 id='impl-Send' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;'a&gt; !<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> for <a class="struct" href="../crossbeam/struct.Scope.html" title="struct crossbeam::Scope">Scope</a>&lt;'a&gt;</code><a href='#impl-Send' class='anchor'></a></span></td><td><span class='out-of-band'></span></td></tr></tbody></table></h3><div class='impl-items'></div><h3 id='impl-Sync' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;'a&gt; !<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sync.html" title="trait core::marker::Sync">Sync</a> for <a class="struct" href="../crossbeam/struct.Scope.html" title="struct crossbeam::Scope">Scope</a>&lt;'a&gt;</code><a href='#impl-Sync' class='anchor'></a></span></td><td><span class='out-of-band'></span></td></tr></tbody></table></h3><div class='impl-items'></div></div></section><section id="search" class="content hidden"></section><section class="footer"></section><aside id="help" class="hidden"><div><h1 class="hidden">Help</h1><div class="shortcuts"><h2>Keyboard Shortcuts</h2><dl><dt><kbd>?</kbd></dt><dd>Show this help dialog</dd><dt><kbd>S</kbd></dt><dd>Focus the search field</dd><dt><kbd>↑</kbd></dt><dd>Move up in search results</dd><dt><kbd>↓</kbd></dt><dd>Move down in search results</dd><dt><kbd>↹</kbd></dt><dd>Switch tab</dd><dt><kbd>&#9166;</kbd></dt><dd>Go to active search result</dd><dt><kbd>+</kbd></dt><dd>Expand all sections</dd><dt><kbd>-</kbd></dt><dd>Collapse all sections</dd></dl></div><div class="infos"><h2>Search Tricks</h2><p>Prefix searches with a type followed by a colon (e.g. <code>fn:</code>) to restrict the search to a given type.</p><p>Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>.</p><p>Search functions by type signature (e.g. <code>vec -> usize</code> or <code>* -> vec</code>)</p><p>Search multiple things at once by splitting your query with comma (e.g. <code>str,u8</code> or <code>String,struct:Vec,test</code>)</p></div></div></aside><script>window.rootPath = "../";window.currentCrate = "crossbeam";</script><script src="../aliases.js"></script><script src="../main.js"></script><script defer src="../search-index.js"></script></body></html>