<!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 `Option` enum in crate `std`."><meta name="keywords" content="rust, rustlang, rust-lang, Option"><title>std::option::Option - 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><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></head><body class="rustdoc enum"><!--[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">☰</div><a href='../../std/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a><p class='location'>Enum Option</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#variants">Variants</a><div class="sidebar-links"><a href="#variant.None">None</a><a href="#variant.Some">Some</a></div><a class="sidebar-title" href="#methods">Methods</a><div class="sidebar-links"><a href="#method.is_some">is_some</a><a href="#method.is_none">is_none</a><a href="#method.as_ref">as_ref</a><a href="#method.as_mut">as_mut</a><a href="#method.as_pin_mut">as_pin_mut</a><a href="#method.expect">expect</a><a href="#method.unwrap">unwrap</a><a href="#method.unwrap_or">unwrap_or</a><a href="#method.unwrap_or_else">unwrap_or_else</a><a href="#method.map">map</a><a href="#method.map_or">map_or</a><a href="#method.map_or_else">map_or_else</a><a href="#method.ok_or">ok_or</a><a href="#method.ok_or_else">ok_or_else</a><a href="#method.iter">iter</a><a href="#method.iter_mut">iter_mut</a><a href="#method.and">and</a><a href="#method.and_then">and_then</a><a href="#method.filter">filter</a><a href="#method.or">or</a><a href="#method.or_else">or_else</a><a href="#method.xor">xor</a><a href="#method.get_or_insert">get_or_insert</a><a href="#method.get_or_insert_with">get_or_insert_with</a><a href="#method.take">take</a><a href="#method.cloned">cloned</a><a href="#method.cloned">cloned</a><a href="#method.unwrap_or_default">unwrap_or_default</a><a href="#method.transpose">transpose</a></div><a class="sidebar-title" href="#implementations">Trait Implementations</a><div class="sidebar-links"><a href="#impl-PartialEq%3COption%3CT%3E%3E">PartialEq<Option<T>></a><a href="#impl-FromIterator%3COption%3CA%3E%3E">FromIterator<Option<A>></a><a href="#impl-Ord">Ord</a><a href="#impl-PartialOrd%3COption%3CT%3E%3E">PartialOrd<Option<T>></a><a href="#impl-Debug">Debug</a><a href="#impl-Hash">Hash</a><a href="#impl-Eq">Eq</a><a href="#impl-Clone">Clone</a><a href="#impl-From%3CT%3E">From<T></a><a href="#impl-Copy">Copy</a><a href="#impl-IntoIterator">IntoIterator</a><a href="#impl-Default">Default</a><a href="#impl-Try">Try</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'>std</a>::<wbr><a href='index.html'>option</a></p><script>window.sidebarCurrent = {name: 'Option', ty: 'enum', 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'>Enum <a href='../index.html'>std</a>::<wbr><a href='index.html'>option</a>::<wbr><a class="enum" href=''>Option</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.0.0'>1.0.0</span><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>−</span>]</a></span><a class='srclink' href='../../src/core/option.rs.html#160-167' title='goto source code'>[src]</a></span></h1><div class="docblock type-decl"><pre class='rust enum'>pub enum Option<T> {
None,
Some(T),
}</pre></div><div class='docblock'><p>The <code>Option</code> type. See <a href="index.html">the module level documentation</a> for more.</p>
</div><h2 id='variants' class='variants small-section-header'>
Variants<a href='#variants' class='anchor'></a></h2>
<span id="variant.None" class="variant small-section-header"><a href="#variant.None" class="anchor field"></a><span id='None.v' class='invisible'><code>None</code></span></span><div class='docblock'><p>No value</p>
</div><span id="variant.Some" class="variant small-section-header"><a href="#variant.Some" class="anchor field"></a><span id='Some.v' class='invisible'><code>Some(T)</code></span></span><div class='docblock'><p>Some value <code>T</code></p>
</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<T> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code><a href='#impl' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#173-848' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.is_some' class="method"><span id='is_some.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.is_some' class='fnname'>is_some</a>(&self) -> <a class="primitive" href="../primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#193-198' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns <code>true</code> if the option is a <a href="#variant.Some"><code>Some</code></a> value.</p>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">is_some</span>(), <span class="bool-val">true</span>);
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">is_some</span>(), <span class="bool-val">false</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20Some(2)%3B%0Aassert_eq!(x.is_some()%2C%20true)%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Aassert_eq!(x.is_some()%2C%20false)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.is_none' class="method"><span id='is_none.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.is_none' class='fnname'>is_none</a>(&self) -> <a class="primitive" href="../primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#215-217' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns <code>true</code> if the option is a <a href="#variant.None"><code>None</code></a> value.</p>
<h1 id="examples-1" class="section-header"><a href="#examples-1">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">is_none</span>(), <span class="bool-val">false</span>);
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">is_none</span>(), <span class="bool-val">true</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20Some(2)%3B%0Aassert_eq!(x.is_none()%2C%20false)%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Aassert_eq!(x.is_none()%2C%20true)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.as_ref' class="method"><span id='as_ref.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.as_ref' class='fnname'>as_ref</a>(&self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><<a class="primitive" href="../primitive.reference.html">&</a>T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#245-250' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Converts from <code>Option<T></code> to <code>Option<&T></code>.</p>
<h1 id="examples-2" class="section-header"><a href="#examples-2">Examples</a></h1>
<p>Convert an <code>Option<</code><a href="../../std/string/struct.String.html"><code>String</code></a><code>></code> into an <code>Option<</code><a href="../../std/primitive.usize.html"><code>usize</code></a><code>></code>, preserving the original.
The <a href="enum.Option.html#method.map"><code>map</code></a> method takes the <code>self</code> argument by value, consuming the original,
so this technique uses <code>as_ref</code> to first take an <code>Option</code> to a reference
to the value inside the original.</p>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">text</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">String</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"Hello, world!"</span>.<span class="ident">to_string</span>());
<span class="comment">// First, cast `Option<String>` to `Option<&String>` with `as_ref`,</span>
<span class="comment">// then consume *that* with `map`, leaving `text` on the stack.</span>
<span class="kw">let</span> <span class="ident">text_length</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span> <span class="op">=</span> <span class="ident">text</span>.<span class="ident">as_ref</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">s</span><span class="op">|</span> <span class="ident">s</span>.<span class="ident">len</span>());
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"still can print text: {:?}"</span>, <span class="ident">text</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20text%3A%20Option%3CString%3E%20%3D%20Some(%22Hello%2C%20world!%22.to_string())%3B%0A%2F%2F%20First%2C%20cast%20%60Option%3CString%3E%60%20to%20%60Option%3C%26String%3E%60%20with%20%60as_ref%60%2C%0A%2F%2F%20then%20consume%20*that*%20with%20%60map%60%2C%20leaving%20%60text%60%20on%20the%20stack.%0Alet%20text_length%3A%20Option%3Cusize%3E%20%3D%20text.as_ref().map(%7Cs%7C%20s.len())%3B%0Aprintln!(%22still%20can%20print%20text%3A%20%7B%3A%3F%7D%22%2C%20text)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.as_mut' class="method"><span id='as_mut.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.as_mut' class='fnname'>as_mut</a>(&mut self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><<a class="primitive" href="../primitive.reference.html">&mut </a>T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#266-271' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Converts from <code>Option<T></code> to <code>Option<&mut T></code>.</p>
<h1 id="examples-3" class="section-header"><a href="#examples-3">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="kw">match</span> <span class="ident">x</span>.<span class="ident">as_mut</span>() {
<span class="prelude-val">Some</span>(<span class="ident">v</span>) <span class="op">=></span> <span class="kw-2">*</span><span class="ident">v</span> <span class="op">=</span> <span class="number">42</span>,
<span class="prelude-val">None</span> <span class="op">=></span> {},
}
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">Some</span>(<span class="number">42</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20mut%20x%20%3D%20Some(2)%3B%0Amatch%20x.as_mut()%20%7B%0A%20%20%20%20Some(v)%20%3D%3E%20*v%20%3D%2042%2C%0A%20%20%20%20None%20%3D%3E%20%7B%7D%2C%0A%7D%0Aassert_eq!(x%2C%20Some(42))%3B%0A%7D">Run</a></pre>
</div><h4 id='method.as_pin_mut' class="method"><span id='as_pin_mut.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.as_pin_mut' class='fnname'>as_pin_mut</a>(self: <a class="struct" href="../../std/mem/struct.PinMut.html" title="struct std::mem::PinMut">PinMut</a><'a, <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>>) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><<a class="struct" href="../../std/mem/struct.PinMut.html" title="struct std::mem::PinMut">PinMut</a><'a, T>></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#276-280' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>pin </code><a href="https://github.com/rust-lang/rust/issues/49150">#49150</a>)</div></div><div class='docblock'><p>Converts from <code>Option<T></code> to <code>Option<PinMut<'_, T>></code></p>
</div><h4 id='method.expect' class="method"><span id='expect.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.expect' class='fnname'>expect</a>(self, msg: &<a class="primitive" href="../primitive.str.html">str</a>) -> T</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#309-314' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Unwraps an option, yielding the content of a <a href="#variant.Some"><code>Some</code></a>.</p>
<h1 id="panics" class="section-header"><a href="#panics">Panics</a></h1>
<p>Panics if the value is a <a href="#variant.None"><code>None</code></a> with a custom panic message provided by
<code>msg</code>.</p>
<h1 id="examples-4" class="section-header"><a href="#examples-4">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"value"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">expect</span>(<span class="string">"the world is ending"</span>), <span class="string">"value"</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%20%3D%20Some(%22value%22)%3B%0Aassert_eq!(x.expect(%22the%20world%20is%20ending%22)%2C%20%22value%22)%3B%0A%7D">Run</a></pre>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="ident">x</span>.<span class="ident">expect</span>(<span class="string">"the world is ending"</span>); <span class="comment">// panics with `the world is ending`</span><a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Ax.expect(%22the%20world%20is%20ending%22)%3B%20%2F%2F%20panics%20with%20%60the%20world%20is%20ending%60%0A%7D">Run</a></pre>
</div><h4 id='method.unwrap' class="method"><span id='unwrap.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.unwrap' class='fnname'>unwrap</a>(self) -> T</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#342-347' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Moves the value <code>v</code> out of the <code>Option<T></code> if it is <a href="#variant.Some"><code>Some(v)</code></a>.</p>
<p>In general, because this function may panic, its use is discouraged.
Instead, prefer to use pattern matching and handle the <a href="#variant.None"><code>None</code></a>
case explicitly.</p>
<h1 id="panics-1" class="section-header"><a href="#panics-1">Panics</a></h1>
<p>Panics if the self value equals <a href="#variant.None"><code>None</code></a>.</p>
<h1 id="examples-5" class="section-header"><a href="#examples-5">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"air"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">unwrap</span>(), <span class="string">"air"</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%20%3D%20Some(%22air%22)%3B%0Aassert_eq!(x.unwrap()%2C%20%22air%22)%3B%0A%7D">Run</a></pre>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">unwrap</span>(), <span class="string">"air"</span>); <span class="comment">// fails</span><a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.unwrap()%2C%20%22air%22)%3B%20%2F%2F%20fails%0A%7D">Run</a></pre>
</div><h4 id='method.unwrap_or' class="method"><span id='unwrap_or.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.unwrap_or' class='fnname'>unwrap_or</a>(self, def: T) -> T</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#365-370' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns the contained value or a default.</p>
<p>Arguments passed to <code>unwrap_or</code> are eagerly evaluated; if you are passing
the result of a function call, it is recommended to use <a href="#method.unwrap_or_else"><code>unwrap_or_else</code></a>,
which is lazily evaluated.</p>
<h1 id="examples-6" class="section-header"><a href="#examples-6">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="string">"car"</span>).<span class="ident">unwrap_or</span>(<span class="string">"bike"</span>), <span class="string">"car"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">None</span>.<span class="ident">unwrap_or</span>(<span class="string">"bike"</span>), <span class="string">"bike"</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Aassert_eq!(Some(%22car%22).unwrap_or(%22bike%22)%2C%20%22car%22)%3B%0Aassert_eq!(None.unwrap_or(%22bike%22)%2C%20%22bike%22)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.unwrap_or_else' class="method"><span id='unwrap_or_else.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.unwrap_or_else' class='fnname'>unwrap_or_else</a><F>(self, f: F) -> T <span class="where fmt-newline">where<br> F: <a class="trait" href="../../std/ops/trait.FnOnce.html" title="trait std::ops::FnOnce">FnOnce</a>() -> T, </span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#383-388' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns the contained value or computes it from a closure.</p>
<h1 id="examples-7" class="section-header"><a href="#examples-7">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">k</span> <span class="op">=</span> <span class="number">10</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="number">4</span>).<span class="ident">unwrap_or_else</span>(<span class="op">||</span> <span class="number">2</span> <span class="op">*</span> <span class="ident">k</span>), <span class="number">4</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">None</span>.<span class="ident">unwrap_or_else</span>(<span class="op">||</span> <span class="number">2</span> <span class="op">*</span> <span class="ident">k</span>), <span class="number">20</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20k%20%3D%2010%3B%0Aassert_eq!(Some(4).unwrap_or_else(%7C%7C%202%20*%20k)%2C%204)%3B%0Aassert_eq!(None.unwrap_or_else(%7C%7C%202%20*%20k)%2C%2020)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.map' class="method"><span id='map.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.map' class='fnname'>map</a><U, F>(self, f: F) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><U> <span class="where fmt-newline">where<br> F: <a class="trait" href="../../std/ops/trait.FnOnce.html" title="trait std::ops::FnOnce">FnOnce</a>(T) -> U, </span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#412-417' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Maps an <code>Option<T></code> to <code>Option<U></code> by applying a function to a contained value.</p>
<h1 id="examples-8" class="section-header"><a href="#examples-8">Examples</a></h1>
<p>Convert an <code>Option<</code><a href="../../std/string/struct.String.html"><code>String</code></a><code>></code> into an <code>Option<</code><a href="../../std/primitive.usize.html"><code>usize</code></a><code>></code>, consuming the original:</p>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">maybe_some_string</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">String</span>::<span class="ident">from</span>(<span class="string">"Hello, World!"</span>));
<span class="comment">// `Option::map` takes self *by value*, consuming `maybe_some_string`</span>
<span class="kw">let</span> <span class="ident">maybe_some_len</span> <span class="op">=</span> <span class="ident">maybe_some_string</span>.<span class="ident">map</span>(<span class="op">|</span><span class="ident">s</span><span class="op">|</span> <span class="ident">s</span>.<span class="ident">len</span>());
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">maybe_some_len</span>, <span class="prelude-val">Some</span>(<span class="number">13</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20maybe_some_string%20%3D%20Some(String%3A%3Afrom(%22Hello%2C%20World!%22))%3B%0A%2F%2F%20%60Option%3A%3Amap%60%20takes%20self%20*by%20value*%2C%20consuming%20%60maybe_some_string%60%0Alet%20maybe_some_len%20%3D%20maybe_some_string.map(%7Cs%7C%20s.len())%3B%0A%0Aassert_eq!(maybe_some_len%2C%20Some(13))%3B%0A%7D">Run</a></pre>
</div><h4 id='method.map_or' class="method"><span id='map_or.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.map_or' class='fnname'>map_or</a><U, F>(self, default: U, f: F) -> U <span class="where fmt-newline">where<br> F: <a class="trait" href="../../std/ops/trait.FnOnce.html" title="trait std::ops::FnOnce">FnOnce</a>(T) -> U, </span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#433-438' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Applies a function to the contained value (if any),
or returns the provided default (if not).</p>
<h1 id="examples-9" class="section-header"><a href="#examples-9">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">map_or</span>(<span class="number">42</span>, <span class="op">|</span><span class="ident">v</span><span class="op">|</span> <span class="ident">v</span>.<span class="ident">len</span>()), <span class="number">3</span>);
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">map_or</span>(<span class="number">42</span>, <span class="op">|</span><span class="ident">v</span><span class="op">|</span> <span class="ident">v</span>.<span class="ident">len</span>()), <span class="number">42</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%20%3D%20Some(%22foo%22)%3B%0Aassert_eq!(x.map_or(42%2C%20%7Cv%7C%20v.len())%2C%203)%3B%0A%0Alet%20x%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.map_or(42%2C%20%7Cv%7C%20v.len())%2C%2042)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.map_or_else' class="method"><span id='map_or_else.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.map_or_else' class='fnname'>map_or_else</a><U, D, F>(self, default: D, f: F) -> U <span class="where fmt-newline">where<br> D: <a class="trait" href="../../std/ops/trait.FnOnce.html" title="trait std::ops::FnOnce">FnOnce</a>() -> U,<br> F: <a class="trait" href="../../std/ops/trait.FnOnce.html" title="trait std::ops::FnOnce">FnOnce</a>(T) -> U, </span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#456-461' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Applies a function to the contained value (if any),
or computes a default (if not).</p>
<h1 id="examples-10" class="section-header"><a href="#examples-10">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">k</span> <span class="op">=</span> <span class="number">21</span>;
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">map_or_else</span>(<span class="op">||</span> <span class="number">2</span> <span class="op">*</span> <span class="ident">k</span>, <span class="op">|</span><span class="ident">v</span><span class="op">|</span> <span class="ident">v</span>.<span class="ident">len</span>()), <span class="number">3</span>);
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">map_or_else</span>(<span class="op">||</span> <span class="number">2</span> <span class="op">*</span> <span class="ident">k</span>, <span class="op">|</span><span class="ident">v</span><span class="op">|</span> <span class="ident">v</span>.<span class="ident">len</span>()), <span class="number">42</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20k%20%3D%2021%3B%0A%0Alet%20x%20%3D%20Some(%22foo%22)%3B%0Aassert_eq!(x.map_or_else(%7C%7C%202%20*%20k%2C%20%7Cv%7C%20v.len())%2C%203)%3B%0A%0Alet%20x%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.map_or_else(%7C%7C%202%20*%20k%2C%20%7Cv%7C%20v.len())%2C%2042)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.ok_or' class="method"><span id='ok_or.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.ok_or' class='fnname'>ok_or</a><E>(self, err: E) -> <a class="enum" href="../../std/result/enum.Result.html" title="enum std::result::Result">Result</a><T, E></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#488-493' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Transforms the <code>Option<T></code> into a <a href="../../std/result/enum.Result.html"><code>Result<T, E></code></a>, mapping <a href="#variant.Some"><code>Some(v)</code></a> to
<a href="../../std/result/enum.Result.html#variant.Ok"><code>Ok(v)</code></a> and <a href="#variant.None"><code>None</code></a> to <a href="../../std/result/enum.Result.html#variant.Err"><code>Err(err)</code></a>.</p>
<p>Arguments passed to <code>ok_or</code> are eagerly evaluated; if you are passing the
result of a function call, it is recommended to use <a href="#method.ok_or_else"><code>ok_or_else</code></a>, which is
lazily evaluated.</p>
<h1 id="examples-11" class="section-header"><a href="#examples-11">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">ok_or</span>(<span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="string">"foo"</span>));
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">ok_or</span>(<span class="number">0</span>), <span class="prelude-val">Err</span>(<span class="number">0</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%20%3D%20Some(%22foo%22)%3B%0Aassert_eq!(x.ok_or(0)%2C%20Ok(%22foo%22))%3B%0A%0Alet%20x%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.ok_or(0)%2C%20Err(0))%3B%0A%7D">Run</a></pre>
</div><h4 id='method.ok_or_else' class="method"><span id='ok_or_else.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.ok_or_else' class='fnname'>ok_or_else</a><E, F>(self, err: F) -> <a class="enum" href="../../std/result/enum.Result.html" title="enum std::result::Result">Result</a><T, E> <span class="where fmt-newline">where<br> F: <a class="trait" href="../../std/ops/trait.FnOnce.html" title="trait std::ops::FnOnce">FnOnce</a>() -> E, </span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#515-520' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Transforms the <code>Option<T></code> into a <a href="../../std/result/enum.Result.html"><code>Result<T, E></code></a>, mapping <a href="#variant.Some"><code>Some(v)</code></a> to
<a href="../../std/result/enum.Result.html#variant.Ok"><code>Ok(v)</code></a> and <a href="#variant.None"><code>None</code></a> to <a href="../../std/result/enum.Result.html#variant.Err"><code>Err(err())</code></a>.</p>
<h1 id="examples-12" class="section-header"><a href="#examples-12">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">ok_or_else</span>(<span class="op">||</span> <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="string">"foo"</span>));
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">ok_or_else</span>(<span class="op">||</span> <span class="number">0</span>), <span class="prelude-val">Err</span>(<span class="number">0</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%20%3D%20Some(%22foo%22)%3B%0Aassert_eq!(x.ok_or_else(%7C%7C%200)%2C%20Ok(%22foo%22))%3B%0A%0Alet%20x%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.ok_or_else(%7C%7C%200)%2C%20Err(0))%3B%0A%7D">Run</a></pre>
</div><h4 id='method.iter' class="method"><div class="important-traits"><div class='tooltip'>ⓘ<span class='tooltiptext'>Important traits for <a class="struct" href="../../std/option/struct.Iter.html" title="struct std::option::Iter">Iter</a><'a, A></span></div><div class="content hidden"><h3 class="important">Important traits for <a class="struct" href="../../std/option/struct.Iter.html" title="struct std::option::Iter">Iter</a><'a, A></h3><code class="content"><span class="where fmt-newline">impl<'a, A> <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a> for <a class="struct" href="../../std/option/struct.Iter.html" title="struct std::option::Iter">Iter</a><'a, A></span><span class="where fmt-newline"> type <a href='../../std/iter/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = <a class="primitive" href="../primitive.reference.html">&'a </a>A;</span></code></div></div><span id='iter.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.iter' class='fnname'>iter</a>(&self) -> <a class="struct" href="../../std/option/struct.Iter.html" title="struct std::option::Iter">Iter</a><T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#539-541' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns an iterator over the possibly contained value.</p>
<h1 id="examples-13" class="section-header"><a href="#examples-13">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">4</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">iter</span>().<span class="ident">next</span>(), <span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="number">4</span>));
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">iter</span>().<span class="ident">next</span>(), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%20%3D%20Some(4)%3B%0Aassert_eq!(x.iter().next()%2C%20Some(%264))%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Aassert_eq!(x.iter().next()%2C%20None)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.iter_mut' class="method"><div class="important-traits"><div class='tooltip'>ⓘ<span class='tooltiptext'>Important traits for <a class="struct" href="../../std/option/struct.IterMut.html" title="struct std::option::IterMut">IterMut</a><'a, A></span></div><div class="content hidden"><h3 class="important">Important traits for <a class="struct" href="../../std/option/struct.IterMut.html" title="struct std::option::IterMut">IterMut</a><'a, A></h3><code class="content"><span class="where fmt-newline">impl<'a, A> <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a> for <a class="struct" href="../../std/option/struct.IterMut.html" title="struct std::option::IterMut">IterMut</a><'a, A></span><span class="where fmt-newline"> type <a href='../../std/iter/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = <a class="primitive" href="../primitive.reference.html">&'a mut </a>A;</span></code></div></div><span id='iter_mut.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.iter_mut' class='fnname'>iter_mut</a>(&mut self) -> <a class="struct" href="../../std/option/struct.IterMut.html" title="struct std::option::IterMut">IterMut</a><T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#560-562' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns a mutable iterator over the possibly contained value.</p>
<h1 id="examples-14" class="section-header"><a href="#examples-14">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">4</span>);
<span class="kw">match</span> <span class="ident">x</span>.<span class="ident">iter_mut</span>().<span class="ident">next</span>() {
<span class="prelude-val">Some</span>(<span class="ident">v</span>) <span class="op">=></span> <span class="kw-2">*</span><span class="ident">v</span> <span class="op">=</span> <span class="number">42</span>,
<span class="prelude-val">None</span> <span class="op">=></span> {},
}
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">Some</span>(<span class="number">42</span>));
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">iter_mut</span>().<span class="ident">next</span>(), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20mut%20x%20%3D%20Some(4)%3B%0Amatch%20x.iter_mut().next()%20%7B%0A%20%20%20%20Some(v)%20%3D%3E%20*v%20%3D%2042%2C%0A%20%20%20%20None%20%3D%3E%20%7B%7D%2C%0A%7D%0Aassert_eq!(x%2C%20Some(42))%3B%0A%0Alet%20mut%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Aassert_eq!(x.iter_mut().next()%2C%20None)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.and' class="method"><span id='and.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.and' class='fnname'>and</a><U>(self, optb: <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><U>) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><U></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#593-598' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns <a href="#variant.None"><code>None</code></a> if the option is <a href="#variant.None"><code>None</code></a>, otherwise returns <code>optb</code>.</p>
<h1 id="examples-15" class="section-header"><a href="#examples-15">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="kw">let</span> <span class="ident">y</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">and</span>(<span class="ident">y</span>), <span class="prelude-val">None</span>);
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">and</span>(<span class="ident">y</span>), <span class="prelude-val">None</span>);
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"foo"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">and</span>(<span class="ident">y</span>), <span class="prelude-val">Some</span>(<span class="string">"foo"</span>));
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">let</span> <span class="ident">y</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">and</span>(<span class="ident">y</span>), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%20%3D%20Some(2)%3B%0Alet%20y%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.and(y)%2C%20None)%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Alet%20y%20%3D%20Some(%22foo%22)%3B%0Aassert_eq!(x.and(y)%2C%20None)%3B%0A%0Alet%20x%20%3D%20Some(2)%3B%0Alet%20y%20%3D%20Some(%22foo%22)%3B%0Aassert_eq!(x.and(y)%2C%20Some(%22foo%22))%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Alet%20y%3A%20Option%3C%26str%3E%20%3D%20None%3B%0Aassert_eq!(x.and(y)%2C%20None)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.and_then' class="method"><span id='and_then.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.and_then' class='fnname'>and_then</a><U, F>(self, f: F) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><U> <span class="where fmt-newline">where<br> F: <a class="trait" href="../../std/ops/trait.FnOnce.html" title="trait std::ops::FnOnce">FnOnce</a>(T) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><U>, </span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#620-625' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns <a href="#variant.None"><code>None</code></a> if the option is <a href="#variant.None"><code>None</code></a>, otherwise calls <code>f</code> with the
wrapped value and returns the result.</p>
<p>Some languages call this operation flatmap.</p>
<h1 id="examples-16" class="section-header"><a href="#examples-16">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">fn</span> <span class="ident">sq</span>(<span class="ident">x</span>: <span class="ident">u32</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> { <span class="prelude-val">Some</span>(<span class="ident">x</span> <span class="op">*</span> <span class="ident">x</span>) }
<span class="kw">fn</span> <span class="ident">nope</span>(<span class="kw">_</span>: <span class="ident">u32</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> { <span class="prelude-val">None</span> }
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="number">2</span>).<span class="ident">and_then</span>(<span class="ident">sq</span>).<span class="ident">and_then</span>(<span class="ident">sq</span>), <span class="prelude-val">Some</span>(<span class="number">16</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="number">2</span>).<span class="ident">and_then</span>(<span class="ident">sq</span>).<span class="ident">and_then</span>(<span class="ident">nope</span>), <span class="prelude-val">None</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="number">2</span>).<span class="ident">and_then</span>(<span class="ident">nope</span>).<span class="ident">and_then</span>(<span class="ident">sq</span>), <span class="prelude-val">None</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">None</span>.<span class="ident">and_then</span>(<span class="ident">sq</span>).<span class="ident">and_then</span>(<span class="ident">sq</span>), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Afn%20sq(x%3A%20u32)%20-%3E%20Option%3Cu32%3E%20%7B%20Some(x%20*%20x)%20%7D%0Afn%20nope(_%3A%20u32)%20-%3E%20Option%3Cu32%3E%20%7B%20None%20%7D%0A%0Aassert_eq!(Some(2).and_then(sq).and_then(sq)%2C%20Some(16))%3B%0Aassert_eq!(Some(2).and_then(sq).and_then(nope)%2C%20None)%3B%0Aassert_eq!(Some(2).and_then(nope).and_then(sq)%2C%20None)%3B%0Aassert_eq!(None.and_then(sq).and_then(sq)%2C%20None)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.filter' class="method"><span id='filter.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.filter' class='fnname'>filter</a><P>(self, predicate: P) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T> <span class="where fmt-newline">where<br> P: <a class="trait" href="../../std/ops/trait.FnOnce.html" title="trait std::ops::FnOnce">FnOnce</a>(<a class="primitive" href="../primitive.reference.html">&</a>T) -> <a class="primitive" href="../primitive.bool.html">bool</a>, </span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.27.0'>1.27.0</div><a class='srclink' href='../../src/core/option.rs.html#651-658' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns <code>None</code> if the option is <code>None</code>, otherwise calls <code>predicate</code>
with the wrapped value and returns:</p>
<ul>
<li><code>Some(t)</code> if <code>predicate</code> returns <code>true</code> (where <code>t</code> is the wrapped
value), and</li>
<li><code>None</code> if <code>predicate</code> returns <code>false</code>.</li>
</ul>
<p>This function works similar to <code>Iterator::filter()</code>. You can imagine
the <code>Option<T></code> being an iterator over one or zero elements. <code>filter()</code>
lets you decide which elements to keep.</p>
<h1 id="examples-17" class="section-header"><a href="#examples-17">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">fn</span> <span class="ident">is_even</span>(<span class="ident">n</span>: <span class="kw-2">&</span><span class="ident">i32</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="ident">n</span> <span class="op">%</span> <span class="number">2</span> <span class="op">==</span> <span class="number">0</span>
}
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">None</span>.<span class="ident">filter</span>(<span class="ident">is_even</span>), <span class="prelude-val">None</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="number">3</span>).<span class="ident">filter</span>(<span class="ident">is_even</span>), <span class="prelude-val">None</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="number">4</span>).<span class="ident">filter</span>(<span class="ident">is_even</span>), <span class="prelude-val">Some</span>(<span class="number">4</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Afn%20is_even(n%3A%20%26i32)%20-%3E%20bool%20%7B%0A%20%20%20%20n%20%25%202%20%3D%3D%200%0A%7D%0A%0Aassert_eq!(None.filter(is_even)%2C%20None)%3B%0Aassert_eq!(Some(3).filter(is_even)%2C%20None)%3B%0Aassert_eq!(Some(4).filter(is_even)%2C%20Some(4))%3B%0A%7D">Run</a></pre>
</div><h4 id='method.or' class="method"><span id='or.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.or' class='fnname'>or</a>(self, optb: <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#689-694' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns the option if it contains a value, otherwise returns <code>optb</code>.</p>
<p>Arguments passed to <code>or</code> are eagerly evaluated; if you are passing the
result of a function call, it is recommended to use <a href="#method.or_else"><code>or_else</code></a>, which is
lazily evaluated.</p>
<h1 id="examples-18" class="section-header"><a href="#examples-18">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">or</span>(<span class="ident">y</span>), <span class="prelude-val">Some</span>(<span class="number">2</span>));
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">100</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">or</span>(<span class="ident">y</span>), <span class="prelude-val">Some</span>(<span class="number">100</span>));
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">100</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">or</span>(<span class="ident">y</span>), <span class="prelude-val">Some</span>(<span class="number">2</span>));
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">or</span>(<span class="ident">y</span>), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%20%3D%20Some(2)%3B%0Alet%20y%20%3D%20None%3B%0Aassert_eq!(x.or(y)%2C%20Some(2))%3B%0A%0Alet%20x%20%3D%20None%3B%0Alet%20y%20%3D%20Some(100)%3B%0Aassert_eq!(x.or(y)%2C%20Some(100))%3B%0A%0Alet%20x%20%3D%20Some(2)%3B%0Alet%20y%20%3D%20Some(100)%3B%0Aassert_eq!(x.or(y)%2C%20Some(2))%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Alet%20y%20%3D%20None%3B%0Aassert_eq!(x.or(y)%2C%20None)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.or_else' class="method"><span id='or_else.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.or_else' class='fnname'>or_else</a><F>(self, f: F) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T> <span class="where fmt-newline">where<br> F: <a class="trait" href="../../std/ops/trait.FnOnce.html" title="trait std::ops::FnOnce">FnOnce</a>() -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>, </span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#711-716' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns the option if it contains a value, otherwise calls <code>f</code> and
returns the result.</p>
<h1 id="examples-19" class="section-header"><a href="#examples-19">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">fn</span> <span class="ident">nobody</span>() <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'static</span> <span class="ident">str</span><span class="op">></span> { <span class="prelude-val">None</span> }
<span class="kw">fn</span> <span class="ident">vikings</span>() <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'static</span> <span class="ident">str</span><span class="op">></span> { <span class="prelude-val">Some</span>(<span class="string">"vikings"</span>) }
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="string">"barbarians"</span>).<span class="ident">or_else</span>(<span class="ident">vikings</span>), <span class="prelude-val">Some</span>(<span class="string">"barbarians"</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">None</span>.<span class="ident">or_else</span>(<span class="ident">vikings</span>), <span class="prelude-val">Some</span>(<span class="string">"vikings"</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">None</span>.<span class="ident">or_else</span>(<span class="ident">nobody</span>), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Afn%20nobody()%20-%3E%20Option%3C%26'static%20str%3E%20%7B%20None%20%7D%0Afn%20vikings()%20-%3E%20Option%3C%26'static%20str%3E%20%7B%20Some(%22vikings%22)%20%7D%0A%0Aassert_eq!(Some(%22barbarians%22).or_else(vikings)%2C%20Some(%22barbarians%22))%3B%0Aassert_eq!(None.or_else(vikings)%2C%20Some(%22vikings%22))%3B%0Aassert_eq!(None.or_else(nobody)%2C%20None)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.xor' class="method"><span id='xor.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.xor' class='fnname'>xor</a>(self, optb: <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#746-752' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>option_xor </code><a href="https://github.com/rust-lang/rust/issues/50512">#50512</a>)</div></div><div class='docblock'><p>Returns <a href="#variant.Some"><code>Some</code></a> if exactly one of <code>self</code>, <code>optb</code> is <a href="#variant.Some"><code>Some</code></a>, otherwise returns <code>None</code>.</p>
<h1 id="examples-20" class="section-header"><a href="#examples-20">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="attribute">#![<span class="ident">feature</span>(<span class="ident">option_xor</span>)]</span>
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="kw">let</span> <span class="ident">y</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">xor</span>(<span class="ident">y</span>), <span class="prelude-val">Some</span>(<span class="number">2</span>));
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">xor</span>(<span class="ident">y</span>), <span class="prelude-val">Some</span>(<span class="number">2</span>));
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">xor</span>(<span class="ident">y</span>), <span class="prelude-val">None</span>);
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">let</span> <span class="ident">y</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">xor</span>(<span class="ident">y</span>), <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0A%23!%5Bfeature(option_xor)%5D%0A%0Afn%20main()%20%7B%0Alet%20x%20%3D%20Some(2)%3B%0Alet%20y%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Aassert_eq!(x.xor(y)%2C%20Some(2))%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Alet%20y%20%3D%20Some(2)%3B%0Aassert_eq!(x.xor(y)%2C%20Some(2))%3B%0A%0Alet%20x%20%3D%20Some(2)%3B%0Alet%20y%20%3D%20Some(2)%3B%0Aassert_eq!(x.xor(y)%2C%20None)%3B%0A%0Alet%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Alet%20y%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Aassert_eq!(x.xor(y)%2C%20None)%3B%0A%7D&version=nightly">Run</a></pre>
</div><h4 id='method.get_or_insert' class="method"><div class="important-traits"><div class='tooltip'>ⓘ<span class='tooltiptext'>Important traits for <a class="primitive" href="../primitive.reference.html">&'a mut </a>I</span></div><div class="content hidden"><h3 class="important">Important traits for <a class="primitive" href="../primitive.reference.html">&'a mut </a>I</h3><code class="content"><span class="where fmt-newline">impl<'a, I> <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a> for <a class="primitive" href="../primitive.reference.html">&'a mut </a>I <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></span><span class="where fmt-newline"> type <a href='../../std/iter/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = <I as <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a>>::<a class="type" href="../../std/iter/trait.Iterator.html#associatedtype.Item" title="type std::iter::Iterator::Item">Item</a>;</span><span class="where fmt-newline">impl<'a, R: <a class="trait" href="../../std/io/trait.Read.html" title="trait std::io::Read">Read</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>> <a class="trait" href="../../std/io/trait.Read.html" title="trait std::io::Read">Read</a> for <a class="primitive" href="../primitive.reference.html">&'a mut </a>R</span><span class="where fmt-newline">impl<'a, W: <a class="trait" href="../../std/io/trait.Write.html" title="trait std::io::Write">Write</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>> <a class="trait" href="../../std/io/trait.Write.html" title="trait std::io::Write">Write</a> for <a class="primitive" href="../primitive.reference.html">&'a mut </a>W</span></code></div></div><span id='get_or_insert.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.get_or_insert' class='fnname'>get_or_insert</a>(&mut self, v: T) -> <a class="primitive" href="../primitive.reference.html">&mut </a>T</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.20.0'>1.20.0</div><a class='srclink' href='../../src/core/option.rs.html#779-789' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Inserts <code>v</code> into the option if it is <a href="#variant.None"><code>None</code></a>, then
returns a mutable reference to the contained value.</p>
<h1 id="examples-21" class="section-header"><a href="#examples-21">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">None</span>;
{
<span class="kw">let</span> <span class="ident">y</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">u32</span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">get_or_insert</span>(<span class="number">5</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">y</span>, <span class="kw-2">&</span><span class="number">5</span>);
<span class="kw-2">*</span><span class="ident">y</span> <span class="op">=</span> <span class="number">7</span>;
}
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">Some</span>(<span class="number">7</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20mut%20x%20%3D%20None%3B%0A%0A%7B%0A%20%20%20%20let%20y%3A%20%26mut%20u32%20%3D%20x.get_or_insert(5)%3B%0A%20%20%20%20assert_eq!(y%2C%20%265)%3B%0A%0A%20%20%20%20*y%20%3D%207%3B%0A%7D%0A%0Aassert_eq!(x%2C%20Some(7))%3B%0A%7D">Run</a></pre>
</div><h4 id='method.get_or_insert_with' class="method"><div class="important-traits"><div class='tooltip'>ⓘ<span class='tooltiptext'>Important traits for <a class="primitive" href="../primitive.reference.html">&'a mut </a>I</span></div><div class="content hidden"><h3 class="important">Important traits for <a class="primitive" href="../primitive.reference.html">&'a mut </a>I</h3><code class="content"><span class="where fmt-newline">impl<'a, I> <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a> for <a class="primitive" href="../primitive.reference.html">&'a mut </a>I <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></span><span class="where fmt-newline"> type <a href='../../std/iter/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = <I as <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a>>::<a class="type" href="../../std/iter/trait.Iterator.html#associatedtype.Item" title="type std::iter::Iterator::Item">Item</a>;</span><span class="where fmt-newline">impl<'a, R: <a class="trait" href="../../std/io/trait.Read.html" title="trait std::io::Read">Read</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>> <a class="trait" href="../../std/io/trait.Read.html" title="trait std::io::Read">Read</a> for <a class="primitive" href="../primitive.reference.html">&'a mut </a>R</span><span class="where fmt-newline">impl<'a, W: <a class="trait" href="../../std/io/trait.Write.html" title="trait std::io::Write">Write</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>> <a class="trait" href="../../std/io/trait.Write.html" title="trait std::io::Write">Write</a> for <a class="primitive" href="../primitive.reference.html">&'a mut </a>W</span></code></div></div><span id='get_or_insert_with.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.get_or_insert_with' class='fnname'>get_or_insert_with</a><F>(&mut self, f: F) -> <a class="primitive" href="../primitive.reference.html">&mut </a>T <span class="where fmt-newline">where<br> F: <a class="trait" href="../../std/ops/trait.FnOnce.html" title="trait std::ops::FnOnce">FnOnce</a>() -> T, </span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.20.0'>1.20.0</div><a class='srclink' href='../../src/core/option.rs.html#812-822' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Inserts a value computed from <code>f</code> into the option if it is <a href="#variant.None"><code>None</code></a>, then
returns a mutable reference to the contained value.</p>
<h1 id="examples-22" class="section-header"><a href="#examples-22">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">None</span>;
{
<span class="kw">let</span> <span class="ident">y</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">u32</span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">get_or_insert_with</span>(<span class="op">||</span> <span class="number">5</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">y</span>, <span class="kw-2">&</span><span class="number">5</span>);
<span class="kw-2">*</span><span class="ident">y</span> <span class="op">=</span> <span class="number">7</span>;
}
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">Some</span>(<span class="number">7</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20mut%20x%20%3D%20None%3B%0A%0A%7B%0A%20%20%20%20let%20y%3A%20%26mut%20u32%20%3D%20x.get_or_insert_with(%7C%7C%205)%3B%0A%20%20%20%20assert_eq!(y%2C%20%265)%3B%0A%0A%20%20%20%20*y%20%3D%207%3B%0A%7D%0A%0Aassert_eq!(x%2C%20Some(7))%3B%0A%7D">Run</a></pre>
</div><h4 id='method.take' class="method"><span id='take.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.take' class='fnname'>take</a>(&mut self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#845-847' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Takes the value out of the option, leaving a <a href="#variant.None"><code>None</code></a> in its place.</p>
<h1 id="examples-23" class="section-header"><a href="#examples-23">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
<span class="ident">x</span>.<span class="ident">take</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">None</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="ident">x</span>.<span class="ident">take</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">None</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20mut%20x%20%3D%20Some(2)%3B%0Ax.take()%3B%0Aassert_eq!(x%2C%20None)%3B%0A%0Alet%20mut%20x%3A%20Option%3Cu32%3E%20%3D%20None%3B%0Ax.take()%3B%0Aassert_eq!(x%2C%20None)%3B%0A%7D">Run</a></pre>
</div></div><h3 id='impl-1' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<'a, T> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><<a class="primitive" href="../primitive.reference.html">&'a </a>T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/clone/trait.Clone.html" title="trait std::clone::Clone">Clone</a>, </span></code><a href='#impl-1' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#850-867' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.cloned' class="method"><span id='cloned.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.cloned' class='fnname'>cloned</a>(self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#864-866' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Maps an <code>Option<&T></code> to an <code>Option<T></code> by cloning the contents of the
option.</p>
<h1 id="examples-24" class="section-header"><a href="#examples-24">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="number">12</span>;
<span class="kw">let</span> <span class="ident">opt_x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="ident">x</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">opt_x</span>, <span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="number">12</span>));
<span class="kw">let</span> <span class="ident">cloned</span> <span class="op">=</span> <span class="ident">opt_x</span>.<span class="ident">cloned</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cloned</span>, <span class="prelude-val">Some</span>(<span class="number">12</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%20%3D%2012%3B%0Alet%20opt_x%20%3D%20Some(%26x)%3B%0Aassert_eq!(opt_x%2C%20Some(%2612))%3B%0Alet%20cloned%20%3D%20opt_x.cloned()%3B%0Aassert_eq!(cloned%2C%20Some(12))%3B%0A%7D">Run</a></pre>
</div></div><h3 id='impl-2' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<'a, T> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><<a class="primitive" href="../primitive.reference.html">&'a mut </a>T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/clone/trait.Clone.html" title="trait std::clone::Clone">Clone</a>, </span></code><a href='#impl-2' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#869-886' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.cloned-1' class="method"><span id='cloned.v-1' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.cloned-1' class='fnname'>cloned</a>(self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.26.0'>1.26.0</div><a class='srclink' href='../../src/core/option.rs.html#883-885' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Maps an <code>Option<&mut T></code> to an <code>Option<T></code> by cloning the contents of the
option.</p>
<h1 id="examples-25" class="section-header"><a href="#examples-25">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="number">12</span>;
<span class="kw">let</span> <span class="ident">opt_x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">x</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">opt_x</span>, <span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="number">12</span>));
<span class="kw">let</span> <span class="ident">cloned</span> <span class="op">=</span> <span class="ident">opt_x</span>.<span class="ident">cloned</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cloned</span>, <span class="prelude-val">Some</span>(<span class="number">12</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20mut%20x%20%3D%2012%3B%0Alet%20opt_x%20%3D%20Some(%26mut%20x)%3B%0Aassert_eq!(opt_x%2C%20Some(%26mut%2012))%3B%0Alet%20cloned%20%3D%20opt_x.cloned()%3B%0Aassert_eq!(cloned%2C%20Some(12))%3B%0A%7D">Run</a></pre>
</div></div><h3 id='impl-3' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/default/trait.Default.html" title="trait std::default::Default">Default</a>, </span></code><a href='#impl-3' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#888-925' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.unwrap_or_default' class="method"><span id='unwrap_or_default.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.unwrap_or_default' class='fnname'>unwrap_or_default</a>(self) -> T</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#919-924' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns the contained value or a default</p>
<p>Consumes the <code>self</code> argument then, if <a href="#variant.Some"><code>Some</code></a>, returns the contained
value, otherwise if <a href="#variant.None"><code>None</code></a>, returns the <a href="../default/trait.Default.html#tymethod.default">default value</a> for that
type.</p>
<h1 id="examples-26" class="section-header"><a href="#examples-26">Examples</a></h1>
<p>Convert a string to an integer, turning poorly-formed strings
into 0 (the default value for integers). <a href="../../std/primitive.str.html#method.parse"><code>parse</code></a> converts
a string to any other type that implements <a href="../../std/str/trait.FromStr.html"><code>FromStr</code></a>, returning
<a href="#variant.None"><code>None</code></a> on error.</p>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">good_year_from_input</span> <span class="op">=</span> <span class="string">"1909"</span>;
<span class="kw">let</span> <span class="ident">bad_year_from_input</span> <span class="op">=</span> <span class="string">"190blarg"</span>;
<span class="kw">let</span> <span class="ident">good_year</span> <span class="op">=</span> <span class="ident">good_year_from_input</span>.<span class="ident">parse</span>().<span class="ident">ok</span>().<span class="ident">unwrap_or_default</span>();
<span class="kw">let</span> <span class="ident">bad_year</span> <span class="op">=</span> <span class="ident">bad_year_from_input</span>.<span class="ident">parse</span>().<span class="ident">ok</span>().<span class="ident">unwrap_or_default</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">1909</span>, <span class="ident">good_year</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0</span>, <span class="ident">bad_year</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20good_year_from_input%20%3D%20%221909%22%3B%0Alet%20bad_year_from_input%20%3D%20%22190blarg%22%3B%0Alet%20good_year%20%3D%20good_year_from_input.parse().ok().unwrap_or_default()%3B%0Alet%20bad_year%20%3D%20bad_year_from_input.parse().ok().unwrap_or_default()%3B%0A%0Aassert_eq!(1909%2C%20good_year)%3B%0Aassert_eq!(0%2C%20bad_year)%3B%0A%7D">Run</a></pre>
</div></div><h3 id='impl-4' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T, E> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><<a class="enum" href="../../std/result/enum.Result.html" title="enum std::result::Result">Result</a><T, E>></code><a href='#impl-4' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#927-954' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.transpose' class="method"><span id='transpose.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.transpose' class='fnname'>transpose</a>(self) -> <a class="enum" href="../../std/result/enum.Result.html" title="enum std::result::Result">Result</a><<a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>, E></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#947-953' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>transpose_result </code><a href="https://github.com/rust-lang/rust/issues/47338">#47338</a>)</div></div><div class='docblock'><p>Transposes an <code>Option</code> of a <code>Result</code> into a <code>Result</code> of an <code>Option</code>.</p>
<p><code>None</code> will be mapped to <code>Ok(None)</code>.
<code>Some(Ok(_))</code> and <code>Some(Err(_))</code> will be mapped to <code>Ok(Some(_))</code> and <code>Err(_)</code>.</p>
<h1 id="examples-27" class="section-header"><a href="#examples-27">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="attribute">#![<span class="ident">feature</span>(<span class="ident">transpose_result</span>)]</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>, <span class="ident">Eq</span>, <span class="ident">PartialEq</span>)]</span>
<span class="kw">struct</span> <span class="ident">SomeErr</span>;
<span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Result</span><span class="op"><</span><span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">i32</span><span class="op">></span>, <span class="ident">SomeErr</span><span class="op">></span> <span class="op">=</span> <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">5</span>));
<span class="kw">let</span> <span class="ident">y</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">i32</span>, <span class="ident">SomeErr</span><span class="op">>></span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="prelude-val">Ok</span>(<span class="number">5</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="ident">y</span>.<span class="ident">transpose</span>());<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0A%23!%5Bfeature(transpose_result)%5D%0A%0Afn%20main()%20%7B%0A%23%5Bderive(Debug%2C%20Eq%2C%20PartialEq)%5D%0Astruct%20SomeErr%3B%0A%0Alet%20x%3A%20Result%3COption%3Ci32%3E%2C%20SomeErr%3E%20%3D%20Ok(Some(5))%3B%0Alet%20y%3A%20Option%3CResult%3Ci32%2C%20SomeErr%3E%3E%20%3D%20Some(Ok(5))%3B%0Aassert_eq!(x%2C%20y.transpose())%3B%0A%7D&version=nightly">Run</a></pre>
</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-PartialEq%3COption%3CT%3E%3E' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T> <a class="trait" href="../../std/cmp/trait.PartialEq.html" title="trait std::cmp::PartialEq">PartialEq</a><<a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>> for <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/cmp/trait.PartialEq.html" title="trait std::cmp::PartialEq">PartialEq</a><T>, </span></code><a href='#impl-PartialEq%3COption%3CT%3E%3E' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.eq' class="method"><span id='eq.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/cmp/trait.PartialEq.html#tymethod.eq' class='fnname'>eq</a>(&self, other: &<a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>) -> <a class="primitive" href="../primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>This method tests for <code>self</code> and <code>other</code> values to be equal, and is used by <code>==</code>. <a href="../../std/cmp/trait.PartialEq.html#tymethod.eq">Read more</a></p>
</div><h4 id='method.ne' class="method"><span id='ne.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/cmp/trait.PartialEq.html#method.ne' class='fnname'>ne</a>(&self, other: &<a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>) -> <a class="primitive" href="../primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>This method tests for <code>!=</code>.</p>
</div></div><h3 id='impl-FromIterator%3COption%3CA%3E%3E' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<A, V> <a class="trait" href="../../std/iter/trait.FromIterator.html" title="trait std::iter::FromIterator">FromIterator</a><<a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><A>> for <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><V> <span class="where fmt-newline">where<br> V: <a class="trait" href="../../std/iter/trait.FromIterator.html" title="trait std::iter::FromIterator">FromIterator</a><A>, </span></code><a href='#impl-FromIterator%3COption%3CA%3E%3E' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#1190-1256' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.from_iter' class="method"><span id='from_iter.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/iter/trait.FromIterator.html#tymethod.from_iter' class='fnname'>from_iter</a><I>(iter: I) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><V> <span class="where fmt-newline">where<br> I: <a class="trait" href="../../std/iter/trait.IntoIterator.html" title="trait std::iter::IntoIterator">IntoIterator</a><Item = <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><A>>, </span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#1212-1255' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Takes each element in the <a href="../iter/trait.Iterator.html"><code>Iterator</code></a>: if it is <a href="enum.Option.html#variant.None"><code>None</code></a>, no further
elements are taken, and the <a href="enum.Option.html#variant.None"><code>None</code></a> is returned. Should no <a href="enum.Option.html#variant.None"><code>None</code></a> occur, a
container with the values of each <code>Option</code> is returned.</p>
<p>Here is an example which increments every integer in a vector,
checking for overflow:</p>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">u16</span>;
<span class="kw">let</span> <span class="ident">v</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="number">1</span>, <span class="number">2</span>];
<span class="kw">let</span> <span class="ident">res</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">u16</span><span class="op">>></span> <span class="op">=</span> <span class="ident">v</span>.<span class="ident">iter</span>().<span class="ident">map</span>(<span class="op">|</span><span class="kw-2">&</span><span class="ident">x</span>: <span class="kw-2">&</span><span class="ident">u16</span><span class="op">|</span>
<span class="kw">if</span> <span class="ident">x</span> <span class="op">==</span> <span class="ident">u16</span>::<span class="ident">MAX</span> { <span class="prelude-val">None</span> }
<span class="kw">else</span> { <span class="prelude-val">Some</span>(<span class="ident">x</span> <span class="op">+</span> <span class="number">1</span>) }
).<span class="ident">collect</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">res</span> <span class="op">==</span> <span class="prelude-val">Some</span>(<span class="macro">vec</span><span class="macro">!</span>[<span class="number">2</span>, <span class="number">3</span>]));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Au16%3B%0A%0Alet%20v%20%3D%20vec!%5B1%2C%202%5D%3B%0Alet%20res%3A%20Option%3CVec%3Cu16%3E%3E%20%3D%20v.iter().map(%7C%26x%3A%20%26u16%7C%0A%20%20%20%20if%20x%20%3D%3D%20u16%3A%3AMAX%20%7B%20None%20%7D%0A%20%20%20%20else%20%7B%20Some(x%20%2B%201)%20%7D%0A).collect()%3B%0Aassert!(res%20%3D%3D%20Some(vec!%5B2%2C%203%5D))%3B%0A%7D">Run</a></pre>
</div></div><h3 id='impl-Ord' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T> <a class="trait" href="../../std/cmp/trait.Ord.html" title="trait std::cmp::Ord">Ord</a> for <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/cmp/trait.Ord.html" title="trait std::cmp::Ord">Ord</a>, </span></code><a href='#impl-Ord' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.cmp' class="method"><span id='cmp.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/cmp/trait.Ord.html#tymethod.cmp' class='fnname'>cmp</a>(&self, other: &<a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>) -> <a class="enum" href="../../std/cmp/enum.Ordering.html" title="enum std::cmp::Ordering">Ordering</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>This method returns an <code>Ordering</code> between <code>self</code> and <code>other</code>. <a href="../../std/cmp/trait.Ord.html#tymethod.cmp">Read more</a></p>
</div><h4 id='method.max' class="method"><span id='max.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/cmp/trait.Ord.html#method.max' class='fnname'>max</a>(self, other: Self) -> Self</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.21.0'>1.21.0</div><a class='srclink' href='../../src/core/cmp.rs.html#469-472' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Compares and returns the maximum of two values. <a href="../../std/cmp/trait.Ord.html#method.max">Read more</a></p>
</div><h4 id='method.min' class="method"><span id='min.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/cmp/trait.Ord.html#method.min' class='fnname'>min</a>(self, other: Self) -> Self</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.21.0'>1.21.0</div><a class='srclink' href='../../src/core/cmp.rs.html#485-488' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Compares and returns the minimum of two values. <a href="../../std/cmp/trait.Ord.html#method.min">Read more</a></p>
</div></div><h3 id='impl-PartialOrd%3COption%3CT%3E%3E' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T> <a class="trait" href="../../std/cmp/trait.PartialOrd.html" title="trait std::cmp::PartialOrd">PartialOrd</a><<a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>> for <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/cmp/trait.PartialOrd.html" title="trait std::cmp::PartialOrd">PartialOrd</a><T>, </span></code><a href='#impl-PartialOrd%3COption%3CT%3E%3E' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.partial_cmp' class="method"><span id='partial_cmp.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/cmp/trait.PartialOrd.html#tymethod.partial_cmp' class='fnname'>partial_cmp</a>(&self, other: &<a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><<a class="enum" href="../../std/cmp/enum.Ordering.html" title="enum std::cmp::Ordering">Ordering</a>></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>This method returns an ordering between <code>self</code> and <code>other</code> values if one exists. <a href="../../std/cmp/trait.PartialOrd.html#tymethod.partial_cmp">Read more</a></p>
</div><h4 id='method.lt' class="method"><span id='lt.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/cmp/trait.PartialOrd.html#method.lt' class='fnname'>lt</a>(&self, other: &<a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>) -> <a class="primitive" href="../primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>This method tests less than (for <code>self</code> and <code>other</code>) and is used by the <code><</code> operator. <a href="../../std/cmp/trait.PartialOrd.html#method.lt">Read more</a></p>
</div><h4 id='method.le' class="method"><span id='le.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/cmp/trait.PartialOrd.html#method.le' class='fnname'>le</a>(&self, other: &<a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>) -> <a class="primitive" href="../primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>This method tests less than or equal to (for <code>self</code> and <code>other</code>) and is used by the <code><=</code> operator. <a href="../../std/cmp/trait.PartialOrd.html#method.le">Read more</a></p>
</div><h4 id='method.gt' class="method"><span id='gt.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/cmp/trait.PartialOrd.html#method.gt' class='fnname'>gt</a>(&self, other: &<a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>) -> <a class="primitive" href="../primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>This method tests greater than (for <code>self</code> and <code>other</code>) and is used by the <code>></code> operator. <a href="../../std/cmp/trait.PartialOrd.html#method.gt">Read more</a></p>
</div><h4 id='method.ge' class="method"><span id='ge.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/cmp/trait.PartialOrd.html#method.ge' class='fnname'>ge</a>(&self, other: &<a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T>) -> <a class="primitive" href="../primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>This method tests greater than or equal to (for <code>self</code> and <code>other</code>) and is used by the <code>>=</code> operator. <a href="../../std/cmp/trait.PartialOrd.html#method.ge">Read more</a></p>
</div></div><h3 id='impl-Debug' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T> <a class="trait" href="../../std/fmt/trait.Debug.html" title="trait std::fmt::Debug">Debug</a> for <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/fmt/trait.Debug.html" title="trait std::fmt::Debug">Debug</a>, </span></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/core/option.rs.html#158' 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='../../std/fmt/trait.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&self, f: &mut <a class="struct" href="../../std/fmt/struct.Formatter.html" title="struct std::fmt::Formatter">Formatter</a>) -> <a class="enum" href="../../std/result/enum.Result.html" title="enum std::result::Result">Result</a><<a class="primitive" href="../primitive.unit.html">()</a>, <a class="struct" href="../../std/fmt/struct.Error.html" title="struct std::fmt::Error">Error</a>></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' 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="../../std/fmt/trait.Debug.html#tymethod.fmt">Read more</a></p>
</div></div><h3 id='impl-Hash' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T> <a class="trait" href="../../std/hash/trait.Hash.html" title="trait std::hash::Hash">Hash</a> for <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/hash/trait.Hash.html" title="trait std::hash::Hash">Hash</a>, </span></code><a href='#impl-Hash' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.hash' class="method"><span id='hash.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/hash/trait.Hash.html#tymethod.hash' class='fnname'>hash</a><__HT>(&self, state: <a class="primitive" href="../primitive.reference.html">&mut </a>__HT) <span class="where fmt-newline">where<br> __HT: <a class="trait" href="../../std/hash/trait.Hasher.html" title="trait std::hash::Hasher">Hasher</a>, </span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Feeds this value into the given [<code>Hasher</code>]. <a href="../../std/hash/trait.Hash.html#tymethod.hash">Read more</a></p>
</div><h4 id='method.hash_slice' class="method"><span id='hash_slice.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/hash/trait.Hash.html#method.hash_slice' class='fnname'>hash_slice</a><H>(data: <a class="primitive" href="../primitive.slice.html">&[Self]</a>, state: <a class="primitive" href="../primitive.reference.html">&mut </a>H) <span class="where fmt-newline">where<br> H: <a class="trait" href="../../std/hash/trait.Hasher.html" title="trait std::hash::Hasher">Hasher</a>, </span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.3.0'>1.3.0</div><a class='srclink' href='../../src/core/hash/mod.rs.html#203-209' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Feeds a slice of this type into the given [<code>Hasher</code>]. <a href="../../std/hash/trait.Hash.html#method.hash_slice">Read more</a></p>
</div></div><h3 id='impl-Eq' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T> <a class="trait" href="../../std/cmp/trait.Eq.html" title="trait std::cmp::Eq">Eq</a> for <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/cmp/trait.Eq.html" title="trait std::cmp::Eq">Eq</a>, </span></code><a href='#impl-Eq' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'></div><h3 id='impl-Clone' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T> <a class="trait" href="../../std/clone/trait.Clone.html" title="trait std::clone::Clone">Clone</a> for <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/clone/trait.Clone.html" title="trait std::clone::Clone">Clone</a>, </span></code><a href='#impl-Clone' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.clone' class="method"><span id='clone.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/clone/trait.Clone.html#tymethod.clone' class='fnname'>clone</a>(&self) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns a copy of the value. <a href="../../std/clone/trait.Clone.html#tymethod.clone">Read more</a></p>
</div><h4 id='method.clone_from' class="method"><span id='clone_from.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/clone/trait.Clone.html#method.clone_from' class='fnname'>clone_from</a>(&mut self, source: <a class="primitive" href="../primitive.reference.html">&</a>Self)</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/clone.rs.html#130-132' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Performs copy-assignment from <code>source</code>. <a href="../../std/clone/trait.Clone.html#method.clone_from">Read more</a></p>
</div></div><h3 id='impl-From%3CT%3E' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T> <a class="trait" href="../../std/convert/trait.From.html" title="trait std::convert::From">From</a><T> for <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code><a href='#impl-From%3CT%3E' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.12.0'>1.12.0</div><a class='srclink' href='../../src/core/option.rs.html#1022-1026' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.from' class="method"><span id='from.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/convert/trait.From.html#tymethod.from' class='fnname'>from</a>(val: T) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#1023-1025' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Performs the conversion.</p>
</div></div><h3 id='impl-Copy' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T> <a class="trait" href="../../std/marker/trait.Copy.html" title="trait std::marker::Copy">Copy</a> for <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/marker/trait.Copy.html" title="trait std::marker::Copy">Copy</a>, </span></code><a href='#impl-Copy' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#158' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'></div><h3 id='impl-IntoIterator' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T> <a class="trait" href="../../std/iter/trait.IntoIterator.html" title="trait std::iter::IntoIterator">IntoIterator</a> for <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code><a href='#impl-IntoIterator' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#978-999' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='associatedtype.Item' class="type"><span id='Item.t' class='invisible'><code>type <a href='../../std/iter/trait.IntoIterator.html#associatedtype.Item' class="type">Item</a> = T</code></span></h4>
<div class='docblock'><p>The type of the elements being iterated over.</p>
</div><h4 id='associatedtype.IntoIter' class="type"><span id='IntoIter.t' class='invisible'><code>type <a href='../../std/iter/trait.IntoIterator.html#associatedtype.IntoIter' class="type">IntoIter</a> = <a class="struct" href="../../std/option/struct.IntoIter.html" title="struct std::option::IntoIter">IntoIter</a><T></code></span></h4>
<div class='docblock'><p>Which kind of iterator are we turning this into?</p>
</div><h4 id='method.into_iter' class="method"><div class="important-traits"><div class='tooltip'>ⓘ<span class='tooltiptext'>Important traits for <a class="struct" href="../../std/option/struct.IntoIter.html" title="struct std::option::IntoIter">IntoIter</a><A></span></div><div class="content hidden"><h3 class="important">Important traits for <a class="struct" href="../../std/option/struct.IntoIter.html" title="struct std::option::IntoIter">IntoIter</a><A></h3><code class="content"><span class="where fmt-newline">impl<A> <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a> for <a class="struct" href="../../std/option/struct.IntoIter.html" title="struct std::option::IntoIter">IntoIter</a><A></span><span class="where fmt-newline"> type <a href='../../std/iter/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = A;</span></code></div></div><span id='into_iter.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/iter/trait.IntoIterator.html#tymethod.into_iter' class='fnname'>into_iter</a>(self) -> <a class="struct" href="../../std/option/struct.IntoIter.html" title="struct std::option::IntoIter">IntoIter</a><T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#996-998' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns a consuming iterator over the possibly contained value.</p>
<h1 id="examples-28" class="section-header"><a href="#examples-28">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">"string"</span>);
<span class="kw">let</span> <span class="ident">v</span>: <span class="ident">Vec</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">into_iter</span>().<span class="ident">collect</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">v</span>, [<span class="string">"string"</span>]);
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">None</span>;
<span class="kw">let</span> <span class="ident">v</span>: <span class="ident">Vec</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">into_iter</span>().<span class="ident">collect</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">v</span>.<span class="ident">is_empty</span>());<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%20%3D%20Some(%22string%22)%3B%0Alet%20v%3A%20Vec%3C%26str%3E%20%3D%20x.into_iter().collect()%3B%0Aassert_eq!(v%2C%20%5B%22string%22%5D)%3B%0A%0Alet%20x%20%3D%20None%3B%0Alet%20v%3A%20Vec%3C%26str%3E%20%3D%20x.into_iter().collect()%3B%0Aassert!(v.is_empty())%3B%0A%7D">Run</a></pre>
</div></div><h3 id='impl-IntoIterator-1' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<'a, T> <a class="trait" href="../../std/iter/trait.IntoIterator.html" title="trait std::iter::IntoIterator">IntoIterator</a> for &'a mut <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code><a href='#impl-IntoIterator-1' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.4.0'>1.4.0</div><a class='srclink' href='../../src/core/option.rs.html#1012-1019' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='associatedtype.Item-1' class="type"><span id='Item.t-1' class='invisible'><code>type <a href='../../std/iter/trait.IntoIterator.html#associatedtype.Item' class="type">Item</a> = <a class="primitive" href="../primitive.reference.html">&'a mut </a>T</code></span></h4>
<div class='docblock'><p>The type of the elements being iterated over.</p>
</div><h4 id='associatedtype.IntoIter-1' class="type"><span id='IntoIter.t-1' class='invisible'><code>type <a href='../../std/iter/trait.IntoIterator.html#associatedtype.IntoIter' class="type">IntoIter</a> = <a class="struct" href="../../std/option/struct.IterMut.html" title="struct std::option::IterMut">IterMut</a><'a, T></code></span></h4>
<div class='docblock'><p>Which kind of iterator are we turning this into?</p>
</div><h4 id='method.into_iter-1' class="method"><div class="important-traits"><div class='tooltip'>ⓘ<span class='tooltiptext'>Important traits for <a class="struct" href="../../std/option/struct.IterMut.html" title="struct std::option::IterMut">IterMut</a><'a, A></span></div><div class="content hidden"><h3 class="important">Important traits for <a class="struct" href="../../std/option/struct.IterMut.html" title="struct std::option::IterMut">IterMut</a><'a, A></h3><code class="content"><span class="where fmt-newline">impl<'a, A> <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a> for <a class="struct" href="../../std/option/struct.IterMut.html" title="struct std::option::IterMut">IterMut</a><'a, A></span><span class="where fmt-newline"> type <a href='../../std/iter/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = <a class="primitive" href="../primitive.reference.html">&'a mut </a>A;</span></code></div></div><span id='into_iter.v-1' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/iter/trait.IntoIterator.html#tymethod.into_iter' class='fnname'>into_iter</a>(self) -> <a class="struct" href="../../std/option/struct.IterMut.html" title="struct std::option::IterMut">IterMut</a><'a, T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#1016-1018' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Creates an iterator from a value. <a href="../../std/iter/trait.IntoIterator.html#tymethod.into_iter">Read more</a></p>
</div></div><h3 id='impl-IntoIterator-2' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<'a, T> <a class="trait" href="../../std/iter/trait.IntoIterator.html" title="trait std::iter::IntoIterator">IntoIterator</a> for &'a <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code><a href='#impl-IntoIterator-2' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.4.0'>1.4.0</div><a class='srclink' href='../../src/core/option.rs.html#1002-1009' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='associatedtype.Item-2' class="type"><span id='Item.t-2' class='invisible'><code>type <a href='../../std/iter/trait.IntoIterator.html#associatedtype.Item' class="type">Item</a> = <a class="primitive" href="../primitive.reference.html">&'a </a>T</code></span></h4>
<div class='docblock'><p>The type of the elements being iterated over.</p>
</div><h4 id='associatedtype.IntoIter-2' class="type"><span id='IntoIter.t-2' class='invisible'><code>type <a href='../../std/iter/trait.IntoIterator.html#associatedtype.IntoIter' class="type">IntoIter</a> = <a class="struct" href="../../std/option/struct.Iter.html" title="struct std::option::Iter">Iter</a><'a, T></code></span></h4>
<div class='docblock'><p>Which kind of iterator are we turning this into?</p>
</div><h4 id='method.into_iter-2' class="method"><div class="important-traits"><div class='tooltip'>ⓘ<span class='tooltiptext'>Important traits for <a class="struct" href="../../std/option/struct.Iter.html" title="struct std::option::Iter">Iter</a><'a, A></span></div><div class="content hidden"><h3 class="important">Important traits for <a class="struct" href="../../std/option/struct.Iter.html" title="struct std::option::Iter">Iter</a><'a, A></h3><code class="content"><span class="where fmt-newline">impl<'a, A> <a class="trait" href="../../std/iter/trait.Iterator.html" title="trait std::iter::Iterator">Iterator</a> for <a class="struct" href="../../std/option/struct.Iter.html" title="struct std::option::Iter">Iter</a><'a, A></span><span class="where fmt-newline"> type <a href='../../std/iter/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = <a class="primitive" href="../primitive.reference.html">&'a </a>A;</span></code></div></div><span id='into_iter.v-2' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/iter/trait.IntoIterator.html#tymethod.into_iter' class='fnname'>into_iter</a>(self) -> <a class="struct" href="../../std/option/struct.Iter.html" title="struct std::option::Iter">Iter</a><'a, T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#1006-1008' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Creates an iterator from a value. <a href="../../std/iter/trait.IntoIterator.html#tymethod.into_iter">Read more</a></p>
</div></div><h3 id='impl-Default' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T> <a class="trait" href="../../std/default/trait.Default.html" title="trait std::default::Default">Default</a> for <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code><a href='#impl-Default' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#969-975' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.default' class="method"><span id='default.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/default/trait.Default.html#tymethod.default' class='fnname'>default</a>() -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#974' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns <a href="#variant.None"><code>None</code></a>.</p>
</div></div><h3 id='impl-Try' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl<T> <a class="trait" href="../../std/ops/trait.Try.html" title="trait std::ops::Try">Try</a> for <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code><a href='#impl-Try' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#1267-1282' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='associatedtype.Ok' class="type"><span id='Ok.t' class='invisible'><code>type <a href='../../std/ops/trait.Try.html#associatedtype.Ok' class="type">Ok</a> = T</code></span></h4>
<div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>try_trait </code><a href="https://github.com/rust-lang/rust/issues/42327">#42327</a>)</div></div><div class='docblock'><p>The type of this value when viewed as successful.</p>
</div><h4 id='associatedtype.Error' class="type"><span id='Error.t' class='invisible'><code>type <a href='../../std/ops/trait.Try.html#associatedtype.Error' class="type">Error</a> = <a class="struct" href="../../std/option/struct.NoneError.html" title="struct std::option::NoneError">NoneError</a></code></span></h4>
<div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>try_trait </code><a href="https://github.com/rust-lang/rust/issues/42327">#42327</a>)</div></div><div class='docblock'><p>The type of this value when viewed as failed.</p>
</div><h4 id='method.into_result' class="method"><span id='into_result.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/ops/trait.Try.html#tymethod.into_result' class='fnname'>into_result</a>(self) -> <a class="enum" href="../../std/result/enum.Result.html" title="enum std::result::Result">Result</a><T, <a class="struct" href="../../std/option/struct.NoneError.html" title="struct std::option::NoneError">NoneError</a>></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#1271-1273' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>try_trait </code><a href="https://github.com/rust-lang/rust/issues/42327">#42327</a>)</div></div><div class='docblock'><p>Applies the "?" operator. A return of <code>Ok(t)</code> means that the execution should continue normally, and the result of <code>?</code> is the value <code>t</code>. A return of <code>Err(e)</code> means that execution should branch to the innermost enclosing <code>catch</code>, or return from the function. <a href="../../std/ops/trait.Try.html#tymethod.into_result">Read more</a></p>
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</div><h4 id='method.from_error' class="method"><span id='from_error.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/ops/trait.Try.html#tymethod.from_error' class='fnname'>from_error</a>(<a class="struct" href="../../std/option/struct.NoneError.html" title="struct std::option::NoneError">NoneError</a>) -> <a class="enum" href="../../std/option/enum.Option.html" title="enum std::option::Option">Option</a><T></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/option.rs.html#1279-1281' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>try_trait </code><a href="https://github.com/rust-lang/rust/issues/42327">#42327</a>)</div></div><div class='docblock'><p>Wrap an error value to construct the composite result. For example, <code>Result::Err(x)</code> and <code>Result::from_error(x)</code> are equivalent. <a href="../../std/ops/trait.Try.html#tymethod.from_error">Read more</a></p>
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