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<h1 class='fqn'><span class='in-band'>Enum <a href='index.html'>enum_primitive</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='https://doc.rust-lang.org/nightly/src/core/option.rs.html#159-166' title='goto source code'>[src]</a></span></h1>
<pre class='rust enum'>pub enum Option<T> {
None,
Some(T),
}</pre><div class='docblock'><p>The <code>Option</code> type. See <a href="index.html">the module level documentation</a> for more.</p>
</div><h2 class='variants'>Variants</h2>
<span id='variant.None' class='variant'><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'><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'>Methods</h2><h3 class='impl'><span class='in-band'><code>impl<T> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#172-736' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.is_some' class="method"><span id='is_some.v' class='invisible'><code>fn <a href='#method.is_some' class='fnname'>is_some</a>(&self) -> <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></h4>
<div class='docblock'><p>Returns <code>true</code> if the option is a <code>Some</code> 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>);</pre>
</div><h4 id='method.is_none' class="method"><span id='is_none.v' class='invisible'><code>fn <a href='#method.is_none' class='fnname'>is_none</a>(&self) -> <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></h4>
<div class='docblock'><p>Returns <code>true</code> if the option is a <code>None</code> 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>);</pre>
</div><h4 id='method.as_ref' class="method"><span id='as_ref.v' class='invisible'><code>fn <a href='#method.as_ref' class='fnname'>as_ref</a>(&self) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><&T></code></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">num_as_str</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">"10"</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 `num_as_str` on the stack.</span>
<span class="kw">let</span> <span class="ident">num_as_int</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">num_as_str</span>.<span class="ident">as_ref</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">n</span><span class="op">|</span> <span class="ident">n</span>.<span class="ident">len</span>());
<span class="macro">println</span><span class="macro">!</span>(<span class="string">"still can print num_as_str: {:?}"</span>, <span class="ident">num_as_str</span>);</pre>
</div><h4 id='method.as_mut' class="method"><span id='as_mut.v' class='invisible'><code>fn <a href='#method.as_mut' class='fnname'>as_mut</a>(&mut self) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><&mut T></code></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>));</pre>
</div><h4 id='method.expect' class="method"><span id='expect.v' class='invisible'><code>fn <a href='#method.expect' class='fnname'>expect</a>(self, msg: &<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>) -> T</code></span></h4>
<div class='docblock'><p>Unwraps an option, yielding the content of a <code>Some</code>.</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>);</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></pre>
</div><h4 id='method.unwrap' class="method"><span id='unwrap.v' class='invisible'><code>fn <a href='#method.unwrap' class='fnname'>unwrap</a>(self) -> T</code></span></h4>
<div class='docblock'><p>Moves the value <code>v</code> out of the <code>Option<T></code> if it is <code>Some(v)</code>.</p>
<p>In general, because this function may panic, its use is discouraged.
Instead, prefer to use pattern matching and handle the <code>None</code>
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>);</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></pre>
</div><h4 id='method.unwrap_or' class="method"><span id='unwrap_or.v' class='invisible'><code>fn <a href='#method.unwrap_or' class='fnname'>unwrap_or</a>(self, def: T) -> T</code></span></h4>
<div class='docblock'><p>Returns the contained value or a default.</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>);</pre>
</div><h4 id='method.unwrap_or_else' class="method"><span id='unwrap_or_else.v' class='invisible'><code>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="https://doc.rust-lang.org/nightly/core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>() -> T, </span></code></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>);</pre>
</div><h4 id='method.map' class="method"><span id='map.v' class='invisible'><code>fn <a href='#method.map' class='fnname'>map</a><U, F>(self, f: F) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><U> <span class="where fmt-newline">where<br> F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>(T) -> U, </span></code></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>));</pre>
</div><h4 id='method.map_or' class="method"><span id='map_or.v' class='invisible'><code>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="https://doc.rust-lang.org/nightly/core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>(T) -> U, </span></code></span></h4>
<div class='docblock'><p>Applies a function to the contained value (if any),
or returns a <code>default</code> (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>);</pre>
</div><h4 id='method.map_or_else' class="method"><span id='map_or_else.v' class='invisible'><code>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="https://doc.rust-lang.org/nightly/core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>() -> U,<br> F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>(T) -> U, </span></code></span></h4>
<div class='docblock'><p>Applies a function to the contained value (if any),
or computes a <code>default</code> (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>);</pre>
</div><h4 id='method.ok_or' class="method"><span id='ok_or.v' class='invisible'><code>fn <a href='#method.ok_or' class='fnname'>ok_or</a><E>(self, err: E) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T, E></code></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 <code>Some(v)</code> to
<a href="../../std/result/enum.Result.html#variant.Ok"><code>Ok(v)</code></a> and <code>None</code> to <a href="../../std/result/enum.Result.html#variant.Err"><code>Err(err)</code></a>.</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>));</pre>
</div><h4 id='method.ok_or_else' class="method"><span id='ok_or_else.v' class='invisible'><code>fn <a href='#method.ok_or_else' class='fnname'>ok_or_else</a><E, F>(self, err: F) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T, E> <span class="where fmt-newline">where<br> F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>() -> E, </span></code></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 <code>Some(v)</code> to
<a href="../../std/result/enum.Result.html#variant.Ok"><code>Ok(v)</code></a> and <code>None</code> 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>));</pre>
</div><h4 id='method.iter' class="method"><span id='iter.v' class='invisible'><code>fn <a href='#method.iter' class='fnname'>iter</a>(&self) -> <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a><T></code></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>);</pre>
</div><h4 id='method.iter_mut' class="method"><span id='iter_mut.v' class='invisible'><code>fn <a href='#method.iter_mut' class='fnname'>iter_mut</a>(&mut self) -> <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a><T></code></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>);</pre>
</div><h4 id='method.and' class="method"><span id='and.v' class='invisible'><code>fn <a href='#method.and' class='fnname'>and</a><U>(self, optb: <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><U>) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><U></code></span></h4>
<div class='docblock'><p>Returns <code>None</code> if the option is <code>None</code>, 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>);</pre>
</div><h4 id='method.and_then' class="method"><span id='and_then.v' class='invisible'><code>fn <a href='#method.and_then' class='fnname'>and_then</a><U, F>(self, f: F) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><U> <span class="where fmt-newline">where<br> F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>(T) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><U>, </span></code></span></h4>
<div class='docblock'><p>Returns <code>None</code> if the option is <code>None</code>, 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="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>);</pre>
</div><h4 id='method.or' class="method"><span id='or.v' class='invisible'><code>fn <a href='#method.or' class='fnname'>or</a>(self, optb: <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T>) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T></code></span></h4>
<div class='docblock'><p>Returns the option if it contains a value, otherwise returns <code>optb</code>.</p>
<h1 id="examples-17" class="section-header"><a href="#examples-17">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>);</pre>
</div><h4 id='method.or_else' class="method"><span id='or_else.v' class='invisible'><code>fn <a href='#method.or_else' class='fnname'>or_else</a><F>(self, f: F) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T> <span class="where fmt-newline">where<br> F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>() -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T>, </span></code></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-18" class="section-header"><a href="#examples-18">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>);</pre>
</div><h4 id='method.get_or_insert' class="method"><span id='get_or_insert.v' class='invisible'><code>fn <a href='#method.get_or_insert' class='fnname'>get_or_insert</a>(&mut self, v: T) -> &mut T</code></span></h4>
<div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>option_entry</code>)</div></div><div class='docblock'><p>Inserts <code>v</code> into the option if it is <code>None</code>, then
returns a mutable reference to the contained value.</p>
<h1 id="examples-19" class="section-header"><a href="#examples-19">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="attribute">#<span class="op">!</span>[<span class="ident">feature</span>(<span class="ident">option_entry</span>)]</span>
<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>));</pre>
</div><h4 id='method.get_or_insert_with' class="method"><span id='get_or_insert_with.v' class='invisible'><code>fn <a href='#method.get_or_insert_with' class='fnname'>get_or_insert_with</a><F>(&mut self, f: F) -> &mut T <span class="where fmt-newline">where<br> F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/trait.FnOnce.html" title="trait core::ops::FnOnce">FnOnce</a>() -> T, </span></code></span></h4>
<div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>option_entry</code>)</div></div><div class='docblock'><p>Inserts a value computed from <code>f</code> into the option if it is <code>None</code>, then
returns a mutable reference to the contained value.</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="op">!</span>[<span class="ident">feature</span>(<span class="ident">option_entry</span>)]</span>
<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>));</pre>
</div><h4 id='method.take' class="method"><span id='take.v' class='invisible'><code>fn <a href='#method.take' class='fnname'>take</a>(&mut self) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T></code></span></h4>
<div class='docblock'><p>Takes the value out of the option, leaving a <code>None</code> in its place.</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">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>);</pre>
</div></div><h3 class='impl'><span class='in-band'><code>impl<'a, T> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><&'a T> <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html" title="trait core::clone::Clone">Clone</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#738-755' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.cloned' class="method"><span id='cloned.v' class='invisible'><code>fn <a href='#method.cloned' class='fnname'>cloned</a>(self) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T></code></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-22" class="section-header"><a href="#examples-22">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>));</pre>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/default/trait.Default.html" title="trait core::default::Default">Default</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#757-788' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.unwrap_or_default' class="method"><span id='unwrap_or_default.v' class='invisible'><code>fn <a href='#method.unwrap_or_default' class='fnname'>unwrap_or_default</a>(self) -> T</code></span></h4>
<div class='docblock'><p>Returns the contained value or a default</p>
<p>Consumes the <code>self</code> argument then, if <code>Some</code>, returns the contained
value, otherwise if <code>None</code>, returns the default value for that
type.</p>
<h1 id="examples-23" class="section-header"><a href="#examples-23">Examples</a></h1>
<p>Convert a string to an integer, turning poorly-formed strings
into 0 (the default value for integers). <code>parse</code> converts
a string to any other type that implements <code>FromStr</code>, returning
<code>None</code> 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>);</pre>
</div></div><h2 id='implementations'>Trait Implementations</h2><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html" title="trait core::iter::traits::IntoIterator">IntoIterator</a> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#810-831' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='associatedtype.Item' class="type"><span id='Item.t' class='invisible'><code>type <a href='https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#associatedtype.Item' class="type">Item</a> = T</code></span></h4>
<h4 id='associatedtype.IntoIter' class="type"><span id='IntoIter.t' class='invisible'><code>type <a href='https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#associatedtype.IntoIter' class="type">IntoIter</a> = <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IntoIter.html" title="struct core::option::IntoIter">IntoIter</a><T></code></span></h4>
<h4 id='method.into_iter' class="method"><span id='into_iter.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#tymethod.into_iter' class='fnname'>into_iter</a>(self) -> <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IntoIter.html" title="struct core::option::IntoIter">IntoIter</a><T></code></span></h4>
<div class='docblock'><p>Returns a consuming iterator over the possibly contained value.</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="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>());</pre>
</div></div><h3 class='impl'><span class='in-band'><code>impl<'a, T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html" title="trait core::iter::traits::IntoIterator">IntoIterator</a> for &'a <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T></code></span><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='https://doc.rust-lang.org/nightly/src/core/option.rs.html#834-841' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='associatedtype.Item-1' class="type"><span id='Item.t-1' class='invisible'><code>type <a href='https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#associatedtype.Item' class="type">Item</a> = &'a T</code></span></h4>
<h4 id='associatedtype.IntoIter-1' class="type"><span id='IntoIter.t-1' class='invisible'><code>type <a href='https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#associatedtype.IntoIter' class="type">IntoIter</a> = <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a><'a, T></code></span></h4>
<h4 id='method.into_iter-1' class="method"><span id='into_iter.v-1' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#tymethod.into_iter' class='fnname'>into_iter</a>(self) -> <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a><'a, T></code></span></h4>
</div><h3 class='impl'><span class='in-band'><code>impl<'a, T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html" title="trait core::iter::traits::IntoIterator">IntoIterator</a> for &'a mut <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T></code></span><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='https://doc.rust-lang.org/nightly/src/core/option.rs.html#844-851' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='associatedtype.Item-2' class="type"><span id='Item.t-2' class='invisible'><code>type <a href='https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#associatedtype.Item' class="type">Item</a> = &'a mut T</code></span></h4>
<h4 id='associatedtype.IntoIter-2' class="type"><span id='IntoIter.t-2' class='invisible'><code>type <a href='https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#associatedtype.IntoIter' class="type">IntoIter</a> = <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a><'a, T></code></span></h4>
<h4 id='method.into_iter-2' class="method"><span id='into_iter.v-2' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#tymethod.into_iter' class='fnname'>into_iter</a>(self) -> <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a><'a, T></code></span></h4>
</div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.Ord.html" title="trait core::cmp::Ord">Ord</a> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.Ord.html" title="trait core::cmp::Ord">Ord</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.cmp' class="method"><span id='cmp.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.Ord.html#tymethod.cmp' class='fnname'>cmp</a>(&self, __arg_0: &<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T>) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/cmp/enum.Ordering.html" title="enum core::cmp::Ordering">Ordering</a></code></span></h4>
</div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialEq.html" title="trait core::cmp::PartialEq">PartialEq</a><<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T>> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialEq.html" title="trait core::cmp::PartialEq">PartialEq</a><T>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.eq' class="method"><span id='eq.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialEq.html#tymethod.eq' class='fnname'>eq</a>(&self, __arg_0: &<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T>) -> <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></h4>
<h4 id='method.ne' class="method"><span id='ne.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialEq.html#method.ne' class='fnname'>ne</a>(&self, __arg_0: &<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T>) -> <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></h4>
</div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Copy.html" title="trait core::marker::Copy">Copy</a> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Copy.html" title="trait core::marker::Copy">Copy</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'></div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html" title="trait core::clone::Clone">Clone</a> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html" title="trait core::clone::Clone">Clone</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.clone' class="method"><span id='clone.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#tymethod.clone' class='fnname'>clone</a>(&self) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T></code></span></h4>
</div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html" title="trait core::cmp::PartialOrd">PartialOrd</a><<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T>> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html" title="trait core::cmp::PartialOrd">PartialOrd</a><T>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.partial_cmp' class="method"><span id='partial_cmp.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#tymethod.partial_cmp' class='fnname'>partial_cmp</a>(&self, __arg_0: &<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T>) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><<a class="enum" href="https://doc.rust-lang.org/nightly/core/cmp/enum.Ordering.html" title="enum core::cmp::Ordering">Ordering</a>></code></span></h4>
<h4 id='method.lt' class="method"><span id='lt.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#method.lt' class='fnname'>lt</a>(&self, __arg_0: &<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T>) -> <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></h4>
<h4 id='method.le' class="method"><span id='le.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#method.le' class='fnname'>le</a>(&self, __arg_0: &<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T>) -> <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></h4>
<h4 id='method.gt' class="method"><span id='gt.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#method.gt' class='fnname'>gt</a>(&self, __arg_0: &<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T>) -> <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></h4>
<h4 id='method.ge' class="method"><span id='ge.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#method.ge' class='fnname'>ge</a>(&self, __arg_0: &<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T>) -> <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></h4>
</div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html" title="trait core::fmt::Debug">Debug</a> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html" title="trait core::fmt::Debug">Debug</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.fmt' class="method"><span id='fmt.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&self, __arg_0: &mut <a class="struct" href="https://doc.rust-lang.org/nightly/core/fmt/struct.Formatter.html" title="struct core::fmt::Formatter">Formatter</a>) -> <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.tuple.html">()</a>, <a class="struct" href="https://doc.rust-lang.org/nightly/core/fmt/struct.Error.html" title="struct core::fmt::Error">Error</a>></code></span></h4>
</div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.From.html" title="trait core::convert::From">From</a><T> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T></code></span><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='https://doc.rust-lang.org/nightly/src/core/option.rs.html#854-858' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.from' class="method"><span id='from.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/convert/trait.From.html#tymethod.from' class='fnname'>from</a>(val: T) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T></code></span></h4>
</div><h3 class='impl'><span class='in-band'><code>impl<A, V> <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/traits/trait.FromIterator.html" title="trait core::iter::traits::FromIterator">FromIterator</a><<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><A>> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><V> <span class="where fmt-newline">where<br> V: <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/traits/trait.FromIterator.html" title="trait core::iter::traits::FromIterator">FromIterator</a><A>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#1022-1075' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.from_iter' class="method"><span id='from_iter.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/iter/traits/trait.FromIterator.html#tymethod.from_iter' class='fnname'>from_iter</a><I>(iter: I) -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><V> <span class="where fmt-newline">where<br> I: <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html" title="trait core::iter::traits::IntoIterator">IntoIterator</a><Item = <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><A>>, </span></code></span></h4>
<div class='docblock'><p>Takes each element in the <code>Iterator</code>: if it is <code>None</code>, no further
elements are taken, and the <code>None</code> is returned. Should no <code>None</code> 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>]));</pre>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.Eq.html" title="trait core::cmp::Eq">Eq</a> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.Eq.html" title="trait core::cmp::Eq">Eq</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'></div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/default/trait.Default.html" title="trait core::default::Default">Default</a> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#803-807' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.default' class="method"><span id='default.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/default/trait.Default.html#tymethod.default' class='fnname'>default</a>() -> <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T></code></span></h4>
<div class='docblock'><p>Returns None.</p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/hash/trait.Hash.html" title="trait core::hash::Hash">Hash</a> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/hash/trait.Hash.html" title="trait core::hash::Hash">Hash</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#157' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.hash' class="method"><span id='hash.v' class='invisible'><code>fn <a href='https://doc.rust-lang.org/nightly/core/hash/trait.Hash.html#tymethod.hash' class='fnname'>hash</a><__HT>(&self, __arg_0: &mut __HT) <span class="where fmt-newline">where<br> __HT: <a class="trait" href="https://doc.rust-lang.org/nightly/core/hash/trait.Hasher.html" title="trait core::hash::Hasher">Hasher</a>, </span></code></span></h4>
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