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  1. <!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 `enum_primitive`."><meta name="keywords" content="rust, rustlang, rust-lang, Option"><title>enum_primitive::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></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">&#9776;</div><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-Try">Try</a><a href="#impl-Debug">Debug</a><a href="#impl-Default">Default</a><a href="#impl-IntoIterator">IntoIterator</a><a href="#impl-Copy">Copy</a><a href="#impl-From%3CT%3E">From&lt;T&gt;</a><a href="#impl-Clone">Clone</a><a href="#impl-PartialOrd%3COption%3CT%3E%3E">PartialOrd&lt;Option&lt;T&gt;&gt;</a><a href="#impl-Ord">Ord</a><a href="#impl-FromIterator%3COption%3CA%3E%3E">FromIterator&lt;Option&lt;A&gt;&gt;</a><a href="#impl-Eq">Eq</a><a href="#impl-PartialEq%3COption%3CT%3E%3E">PartialEq&lt;Option&lt;T&gt;&gt;</a><a href="#impl-Hash">Hash</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'>enum_primitive</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'>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'>&#x2212;</span>]</a></span><a class='srclink' href='https://doc.rust-lang.org/nightly/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&lt;T&gt; {
    2. 

  2.     None,
    3. 

  3.     Some(T),
    4. 

  4. }</pre></div><div class='docblock'><p>The <code>Option</code> type. See <a href="index.html">the module level documentation</a> for more.</p>
    5. 

  5. </div><h2 id='variants' class='variants small-section-header'>
    6. 

  6.                    Variants<a href='#variants' class='anchor'></a></h2>
    7. 

  7. <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>
    8. 

  8. </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>
    9. 

  9. </div>
    10. 

  10.                     <h2 id='methods' class='small-section-header'>
    11. 

  11.                       Methods<a href='#methods' class='anchor'></a>
    12. 

  12.                     </h2>
    13. 

  13.                 <h3 id='impl' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</code><a href='#impl' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>(&amp;self) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    14. 

  14. <h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
    15. 

  15. <pre class="rust rust-example-rendered">
    16. 

  16. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
    17. 

  17. <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>);
    18. 

  18. 

  19. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    20. 

  20. <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>
    21. 

  21. </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>(&amp;self) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    22. 

  22. <h1 id="examples-1" class="section-header"><a href="#examples-1">Examples</a></h1>
    23. 

  23. <pre class="rust rust-example-rendered">
    24. 

  24. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">2</span>);
    25. 

  25. <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>);
    26. 

  26. 

  27. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    28. 

  28. <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>
    29. 

  29. </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>(&amp;self) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;</a>T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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&lt;T&gt;</code> to <code>Option&lt;&amp;T&gt;</code>.</p>
    30. 

  30. <h1 id="examples-2" class="section-header"><a href="#examples-2">Examples</a></h1>
    31. 

  31. <p>Convert an <code>Option&lt;</code><a href="../../std/string/struct.String.html"><code>String</code></a><code>&gt;</code> into an <code>Option&lt;</code><a href="../../std/primitive.usize.html"><code>usize</code></a><code>&gt;</code>, preserving the original.
    32. 

  32. The <a href="enum.Option.html#method.map"><code>map</code></a> method takes the <code>self</code> argument by value, consuming the original,
    33. 

  33. so this technique uses <code>as_ref</code> to first take an <code>Option</code> to a reference
    34. 

  34. to the value inside the original.</p>
    35. 

  35. 

  36. <pre class="rust rust-example-rendered">
    37. 

  37. <span class="kw">let</span> <span class="ident">text</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">String</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">&quot;Hello, world!&quot;</span>.<span class="ident">to_string</span>());
    38. 

  38. <span class="comment">// First, cast `Option&lt;String&gt;` to `Option&lt;&amp;String&gt;` with `as_ref`,</span>
    39. 

  39. <span class="comment">// then consume *that* with `map`, leaving `text` on the stack.</span>
    40. 

  40. <span class="kw">let</span> <span class="ident">text_length</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">usize</span><span class="op">&gt;</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>());
    41. 

  41. <span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;still can print text: {:?}&quot;</span>, <span class="ident">text</span>);</pre>
    42. 

  42. </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>(&amp;mut self) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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&lt;T&gt;</code> to <code>Option&lt;&amp;mut T&gt;</code>.</p>
    43. 

  43. <h1 id="examples-3" class="section-header"><a href="#examples-3">Examples</a></h1>
    44. 

  44. <pre class="rust rust-example-rendered">
    45. 

  45. <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>);
    46. 

  46. <span class="kw">match</span> <span class="ident">x</span>.<span class="ident">as_mut</span>() {
    47. 

  47.     <span class="prelude-val">Some</span>(<span class="ident">v</span>) <span class="op">=&gt;</span> <span class="kw-2">*</span><span class="ident">v</span> <span class="op">=</span> <span class="number">42</span>,
    48. 

  48.     <span class="prelude-val">None</span> <span class="op">=&gt;</span> {},
    49. 

  49. }
    50. 

  50. <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>
    51. 

  51. </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="https://doc.rust-lang.org/nightly/core/mem/struct.PinMut.html" title="struct core::mem::PinMut">PinMut</a>&lt;'a, <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;&gt;) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;<a class="struct" href="https://doc.rust-lang.org/nightly/core/mem/struct.PinMut.html" title="struct core::mem::PinMut">PinMut</a>&lt;'a, T&gt;&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>)</div></div><div class='docblock'><p>Converts from <code>Option&lt;T&gt;</code> to <code>Option&lt;PinMut&lt;'_, T&gt;&gt;</code></p>
    52. 

  52. </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: &amp;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.str.html">str</a>) -&gt; T</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    53. 

  53. <h1 id="panics" class="section-header"><a href="#panics">Panics</a></h1>
    54. 

  54. <p>Panics if the value is a <a href="#variant.None"><code>None</code></a> with a custom panic message provided by
    55. 

  55. <code>msg</code>.</p>
    56. 

  56. <h1 id="examples-4" class="section-header"><a href="#examples-4">Examples</a></h1>
    57. 

  57. <pre class="rust rust-example-rendered">
    58. 

  58. <span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">&quot;value&quot;</span>);
    59. 

  59. <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">expect</span>(<span class="string">&quot;the world is ending&quot;</span>), <span class="string">&quot;value&quot;</span>);</pre>
    60. 

  60. 

  61. <pre class="rust rust-example-rendered">
    62. 

  62. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="ident">str</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    63. 

  63. <span class="ident">x</span>.<span class="ident">expect</span>(<span class="string">&quot;the world is ending&quot;</span>); <span class="comment">// panics with `the world is ending`</span></pre>
    64. 

  64. </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) -&gt; T</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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&lt;T&gt;</code> if it is <a href="#variant.Some"><code>Some(v)</code></a>.</p>
    65. 

  65. <p>In general, because this function may panic, its use is discouraged.
    66. 

  66. Instead, prefer to use pattern matching and handle the <a href="#variant.None"><code>None</code></a>
    67. 

  67. case explicitly.</p>
    68. 

  68. <h1 id="panics-1" class="section-header"><a href="#panics-1">Panics</a></h1>
    69. 

  69. <p>Panics if the self value equals <a href="#variant.None"><code>None</code></a>.</p>
    70. 

  70. <h1 id="examples-5" class="section-header"><a href="#examples-5">Examples</a></h1>
    71. 

  71. <pre class="rust rust-example-rendered">
    72. 

  72. <span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">&quot;air&quot;</span>);
    73. 

  73. <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">unwrap</span>(), <span class="string">&quot;air&quot;</span>);</pre>
    74. 

  74. 

  75. <pre class="rust rust-example-rendered">
    76. 

  76. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="ident">str</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    77. 

  77. <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>.<span class="ident">unwrap</span>(), <span class="string">&quot;air&quot;</span>); <span class="comment">// fails</span></pre>
    78. 

  78. </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) -&gt; T</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    79. 

  79. <p>Arguments passed to <code>unwrap_or</code> are eagerly evaluated; if you are passing
    80. 

  80. the result of a function call, it is recommended to use <a href="#method.unwrap_or_else"><code>unwrap_or_else</code></a>,
    81. 

  81. which is lazily evaluated.</p>
    82. 

  82. <h1 id="examples-6" class="section-header"><a href="#examples-6">Examples</a></h1>
    83. 

  83. <pre class="rust rust-example-rendered">
    84. 

  84. <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="string">&quot;car&quot;</span>).<span class="ident">unwrap_or</span>(<span class="string">&quot;bike&quot;</span>), <span class="string">&quot;car&quot;</span>);
    85. 

  85. <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">&quot;bike&quot;</span>), <span class="string">&quot;bike&quot;</span>);</pre>
    86. 

  86. </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>&lt;F&gt;(self, f: F) -&gt; T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>() -&gt; T,&nbsp;</span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    87. 

  87. <h1 id="examples-7" class="section-header"><a href="#examples-7">Examples</a></h1>
    88. 

  88. <pre class="rust rust-example-rendered">
    89. 

  89. <span class="kw">let</span> <span class="ident">k</span> <span class="op">=</span> <span class="number">10</span>;
    90. 

  90. <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>);
    91. 

  91. <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>
    92. 

  92. </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>&lt;U, F&gt;(self, f: F) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;U&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(T) -&gt; U,&nbsp;</span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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&lt;T&gt;</code> to <code>Option&lt;U&gt;</code> by applying a function to a contained value.</p>
    93. 

  93. <h1 id="examples-8" class="section-header"><a href="#examples-8">Examples</a></h1>
    94. 

  94. <p>Convert an <code>Option&lt;</code><a href="../../std/string/struct.String.html"><code>String</code></a><code>&gt;</code> into an <code>Option&lt;</code><a href="../../std/primitive.usize.html"><code>usize</code></a><code>&gt;</code>, consuming the original:</p>
    95. 

  95. 

  96. <pre class="rust rust-example-rendered">
    97. 

  97. <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">&quot;Hello, World!&quot;</span>));
    98. 

  98. <span class="comment">// `Option::map` takes self *by value*, consuming `maybe_some_string`</span>
    99. 

  99. <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>());
    100. 

  100. 

  101. <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>
    102. 

  102. </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>&lt;U, F&gt;(self, default: U, f: F) -&gt; U <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(T) -&gt; U,&nbsp;</span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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),
    103. 

  103. or returns the provided default (if not).</p>
    104. 

  104. <h1 id="examples-9" class="section-header"><a href="#examples-9">Examples</a></h1>
    105. 

  105. <pre class="rust rust-example-rendered">
    106. 

  106. <span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">&quot;foo&quot;</span>);
    107. 

  107. <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>);
    108. 

  108. 

  109. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="ident">str</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    110. 

  110. <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>
    111. 

  111. </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>&lt;U, D, F&gt;(self, default: D, f: F) -&gt; U <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;D: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>() -&gt; U,<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(T) -&gt; U,&nbsp;</span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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),
    112. 

  112. or computes a default (if not).</p>
    113. 

  113. <h1 id="examples-10" class="section-header"><a href="#examples-10">Examples</a></h1>
    114. 

  114. <pre class="rust rust-example-rendered">
    115. 

  115. <span class="kw">let</span> <span class="ident">k</span> <span class="op">=</span> <span class="number">21</span>;
    116. 

  116. 

  117. <span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">&quot;foo&quot;</span>);
    118. 

  118. <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>);
    119. 

  119. 

  120. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="ident">str</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    121. 

  121. <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>
    122. 

  122. </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>&lt;E&gt;(self, err: E) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;T, E&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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&lt;T&gt;</code> into a <a href="../../std/result/enum.Result.html"><code>Result&lt;T, E&gt;</code></a>, mapping <a href="#variant.Some"><code>Some(v)</code></a> to
    123. 

  123. <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>
    124. 

  124. <p>Arguments passed to <code>ok_or</code> are eagerly evaluated; if you are passing the
    125. 

  125. result of a function call, it is recommended to use <a href="#method.ok_or_else"><code>ok_or_else</code></a>, which is
    126. 

  126. lazily evaluated.</p>
    127. 

  127. <h1 id="examples-11" class="section-header"><a href="#examples-11">Examples</a></h1>
    128. 

  128. <pre class="rust rust-example-rendered">
    129. 

  129. <span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">&quot;foo&quot;</span>);
    130. 

  130. <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">&quot;foo&quot;</span>));
    131. 

  131. 

  132. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="ident">str</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    133. 

  133. <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>
    134. 

  134. </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>&lt;E, F&gt;(self, err: F) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;T, E&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>() -&gt; E,&nbsp;</span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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&lt;T&gt;</code> into a <a href="../../std/result/enum.Result.html"><code>Result&lt;T, E&gt;</code></a>, mapping <a href="#variant.Some"><code>Some(v)</code></a> to
    135. 

  135. <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>
    136. 

  136. <h1 id="examples-12" class="section-header"><a href="#examples-12">Examples</a></h1>
    137. 

  137. <pre class="rust rust-example-rendered">
    138. 

  138. <span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">&quot;foo&quot;</span>);
    139. 

  139. <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">&quot;foo&quot;</span>));
    140. 

  140. 

  141. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="ident">str</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    142. 

  142. <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>
    143. 

  143. </div><h4 id='method.iter' class="method"><div class="important-traits"><div class='tooltip'>ⓘ<span class='tooltiptext'>Important traits for <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a>&lt;'a, A&gt;</span></div><div class="content hidden"><h3 class="important">Important traits for <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a>&lt;'a, A&gt;</h3><code class="content"><span class="where fmt-newline">impl&lt;'a, A&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html" title="trait core::iter::iterator::Iterator">Iterator</a> for <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a>&lt;'a, A&gt;</span><span class="where fmt-newline">    type <a href='https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'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>(&amp;self) -&gt; <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a>&lt;T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    144. 

  144. <h1 id="examples-13" class="section-header"><a href="#examples-13">Examples</a></h1>
    145. 

  145. <pre class="rust rust-example-rendered">
    146. 

  146. <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>);
    147. 

  147. <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">&amp;</span><span class="number">4</span>));
    148. 

  148. 

  149. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    150. 

  150. <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>
    151. 

  151. </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="https://doc.rust-lang.org/nightly/core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a>&lt;'a, A&gt;</span></div><div class="content hidden"><h3 class="important">Important traits for <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a>&lt;'a, A&gt;</h3><code class="content"><span class="where fmt-newline">impl&lt;'a, A&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html" title="trait core::iter::iterator::Iterator">Iterator</a> for <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a>&lt;'a, A&gt;</span><span class="where fmt-newline">    type <a href='https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'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>(&amp;mut self) -&gt; <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a>&lt;T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    152. 

  152. <h1 id="examples-14" class="section-header"><a href="#examples-14">Examples</a></h1>
    153. 

  153. <pre class="rust rust-example-rendered">
    154. 

  154. <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>);
    155. 

  155. <span class="kw">match</span> <span class="ident">x</span>.<span class="ident">iter_mut</span>().<span class="ident">next</span>() {
    156. 

  156.     <span class="prelude-val">Some</span>(<span class="ident">v</span>) <span class="op">=&gt;</span> <span class="kw-2">*</span><span class="ident">v</span> <span class="op">=</span> <span class="number">42</span>,
    157. 

  157.     <span class="prelude-val">None</span> <span class="op">=&gt;</span> {},
    158. 

  158. }
    159. 

  159. <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>));
    160. 

  160. 

  161. <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">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    162. 

  162. <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>
    163. 

  163. </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>&lt;U&gt;(self, optb: <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;U&gt;) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;U&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    164. 

  164. <h1 id="examples-15" class="section-header"><a href="#examples-15">Examples</a></h1>
    165. 

  165. <pre class="rust rust-example-rendered">
    166. 

  166. <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>);
    167. 

  167. <span class="kw">let</span> <span class="ident">y</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="ident">str</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    168. 

  168. <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>);
    169. 

  169. 

  170. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    171. 

  171. <span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">&quot;foo&quot;</span>);
    172. 

  172. <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>);
    173. 

  173. 

  174. <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>);
    175. 

  175. <span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">&quot;foo&quot;</span>);
    176. 

  176. <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">&quot;foo&quot;</span>));
    177. 

  177. 

  178. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    179. 

  179. <span class="kw">let</span> <span class="ident">y</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="ident">str</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    180. 

  180. <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>
    181. 

  181. </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>&lt;U, F&gt;(self, f: F) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;U&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(T) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;U&gt;,&nbsp;</span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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
    182. 

  182. wrapped value and returns the result.</p>
    183. 

  183. <p>Some languages call this operation flatmap.</p>
    184. 

  184. <h1 id="examples-16" class="section-header"><a href="#examples-16">Examples</a></h1>
    185. 

  185. <pre class="rust rust-example-rendered">
    186. 

  186. <span class="kw">fn</span> <span class="ident">sq</span>(<span class="ident">x</span>: <span class="ident">u32</span>) <span class="op">-&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> { <span class="prelude-val">Some</span>(<span class="ident">x</span> <span class="op">*</span> <span class="ident">x</span>) }
    187. 

  187. <span class="kw">fn</span> <span class="ident">nope</span>(<span class="kw">_</span>: <span class="ident">u32</span>) <span class="op">-&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> { <span class="prelude-val">None</span> }
    188. 

  188. 

  189. <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>));
    190. 

  190. <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>);
    191. 

  191. <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>);
    192. 

  192. <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>
    193. 

  193. </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>&lt;P&gt;(self, predicate: P) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;P: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;</a>T) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a>,&nbsp;</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='https://doc.rust-lang.org/nightly/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>
    194. 

  194. with the wrapped value and returns:</p>
    195. 

  195. <ul>
    196. 

  196. <li><code>Some(t)</code> if <code>predicate</code> returns <code>true</code> (where <code>t</code> is the wrapped
    197. 

  197. value), and</li>
    198. 

  198. <li><code>None</code> if <code>predicate</code> returns <code>false</code>.</li>
    199. 

  199. </ul>
    200. 

  200. <p>This function works similar to <code>Iterator::filter()</code>. You can imagine
    201. 

  201. the <code>Option&lt;T&gt;</code> being an iterator over one or zero elements. <code>filter()</code>
    202. 

  202. lets you decide which elements to keep.</p>
    203. 

  203. <h1 id="examples-17" class="section-header"><a href="#examples-17">Examples</a></h1>
    204. 

  204. <pre class="rust rust-example-rendered">
    205. 

  205. <span class="kw">fn</span> <span class="ident">is_even</span>(<span class="ident">n</span>: <span class="kw-2">&amp;</span><span class="ident">i32</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
    206. 

  206.     <span class="ident">n</span> <span class="op">%</span> <span class="number">2</span> <span class="op">==</span> <span class="number">0</span>
    207. 

  207. }
    208. 

  208. 

  209. <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>);
    210. 

  210. <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>);
    211. 

  211. <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>));</pre>
    212. 

  212. </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="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    213. 

  213. <p>Arguments passed to <code>or</code> are eagerly evaluated; if you are passing the
    214. 

  214. result of a function call, it is recommended to use <a href="#method.or_else"><code>or_else</code></a>, which is
    215. 

  215. lazily evaluated.</p>
    216. 

  216. <h1 id="examples-18" class="section-header"><a href="#examples-18">Examples</a></h1>
    217. 

  217. <pre class="rust rust-example-rendered">
    218. 

  218. <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>);
    219. 

  219. <span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    220. 

  220. <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>));
    221. 

  221. 

  222. <span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    223. 

  223. <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>);
    224. 

  224. <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>));
    225. 

  225. 

  226. <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>);
    227. 

  227. <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>);
    228. 

  228. <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>));
    229. 

  229. 

  230. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    231. 

  231. <span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    232. 

  232. <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>
    233. 

  233. </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>&lt;F&gt;(self, f: F) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>() -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;,&nbsp;</span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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
    234. 

  234. returns the result.</p>
    235. 

  235. <h1 id="examples-19" class="section-header"><a href="#examples-19">Examples</a></h1>
    236. 

  236. <pre class="rust rust-example-rendered">
    237. 

  237. <span class="kw">fn</span> <span class="ident">nobody</span>() <span class="op">-&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="lifetime">&#39;static</span> <span class="ident">str</span><span class="op">&gt;</span> { <span class="prelude-val">None</span> }
    238. 

  238. <span class="kw">fn</span> <span class="ident">vikings</span>() <span class="op">-&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="lifetime">&#39;static</span> <span class="ident">str</span><span class="op">&gt;</span> { <span class="prelude-val">Some</span>(<span class="string">&quot;vikings&quot;</span>) }
    239. 

  239. 

  240. <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="prelude-val">Some</span>(<span class="string">&quot;barbarians&quot;</span>).<span class="ident">or_else</span>(<span class="ident">vikings</span>), <span class="prelude-val">Some</span>(<span class="string">&quot;barbarians&quot;</span>));
    241. 

  241. <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">&quot;vikings&quot;</span>));
    242. 

  242. <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>
    243. 

  243. </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="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>)</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>
    244. 

  244. <h1 id="examples-20" class="section-header"><a href="#examples-20">Examples</a></h1>
    245. 

  245. <pre class="rust rust-example-rendered">
    246. 

  246. <span class="attribute">#![<span class="ident">feature</span>(<span class="ident">option_xor</span>)]</span>
    247. 

  247. 

  248. <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>);
    249. 

  249. <span class="kw">let</span> <span class="ident">y</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    250. 

  250. <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>));
    251. 

  251. 

  252. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    253. 

  253. <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>);
    254. 

  254. <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>));
    255. 

  255. 

  256. <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>);
    257. 

  257. <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>);
    258. 

  258. <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>);
    259. 

  259. 

  260. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    261. 

  261. <span class="kw">let</span> <span class="ident">y</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    262. 

  262. <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>);</pre>
    263. 

  263. </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="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a mut </a>R</span></div><div class="content hidden"><h3 class="important">Important traits for <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a mut </a>R</h3><code class="content"><span class="where fmt-newline">impl&lt;'a, R&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/std/io/trait.Read.html" title="trait std::io::Read">Read</a> for <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a mut </a>R <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;R: <a class="trait" href="https://doc.rust-lang.org/nightly/std/io/trait.Read.html" title="trait std::io::Read">Read</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,&nbsp;</span></span><span class="where fmt-newline">impl&lt;'a, W&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/std/io/trait.Write.html" title="trait std::io::Write">Write</a> for <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a mut </a>W <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;W: <a class="trait" href="https://doc.rust-lang.org/nightly/std/io/trait.Write.html" title="trait std::io::Write">Write</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,&nbsp;</span></span><span class="where fmt-newline">impl&lt;'a, I&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html" title="trait core::iter::iterator::Iterator">Iterator</a> for <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a mut </a>I <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;I: <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html" title="trait core::iter::iterator::Iterator">Iterator</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,&nbsp;</span></span><span class="where fmt-newline">    type <a href='https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = &lt;I as <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html" title="trait core::iter::iterator::Iterator">Iterator</a>&gt;::<a class="type" href="https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html#associatedtype.Item" title="type core::iter::iterator::Iterator::Item">Item</a>;</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>(&amp;mut self, v: T) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;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='https://doc.rust-lang.org/nightly/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
    264. 

  264. returns a mutable reference to the contained value.</p>
    265. 

  265. <h1 id="examples-21" class="section-header"><a href="#examples-21">Examples</a></h1>
    266. 

  266. <pre class="rust rust-example-rendered">
    267. 

  267. <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>;
    268. 

  268. 

  269. {
    270. 

  270.     <span class="kw">let</span> <span class="ident">y</span>: <span class="kw-2">&amp;</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>);
    271. 

  271.     <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">y</span>, <span class="kw-2">&amp;</span><span class="number">5</span>);
    272. 

  272. 

  273.     <span class="kw-2">*</span><span class="ident">y</span> <span class="op">=</span> <span class="number">7</span>;
    274. 

  274. }
    275. 

  275. 

  276. <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>
    277. 

  277. </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="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a mut </a>R</span></div><div class="content hidden"><h3 class="important">Important traits for <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a mut </a>R</h3><code class="content"><span class="where fmt-newline">impl&lt;'a, R&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/std/io/trait.Read.html" title="trait std::io::Read">Read</a> for <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a mut </a>R <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;R: <a class="trait" href="https://doc.rust-lang.org/nightly/std/io/trait.Read.html" title="trait std::io::Read">Read</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,&nbsp;</span></span><span class="where fmt-newline">impl&lt;'a, W&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/std/io/trait.Write.html" title="trait std::io::Write">Write</a> for <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a mut </a>W <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;W: <a class="trait" href="https://doc.rust-lang.org/nightly/std/io/trait.Write.html" title="trait std::io::Write">Write</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,&nbsp;</span></span><span class="where fmt-newline">impl&lt;'a, I&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html" title="trait core::iter::iterator::Iterator">Iterator</a> for <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a mut </a>I <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;I: <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html" title="trait core::iter::iterator::Iterator">Iterator</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,&nbsp;</span></span><span class="where fmt-newline">    type <a href='https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = &lt;I as <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html" title="trait core::iter::iterator::Iterator">Iterator</a>&gt;::<a class="type" href="https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html#associatedtype.Item" title="type core::iter::iterator::Iterator::Item">Item</a>;</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>&lt;F&gt;(&amp;mut self, f: F) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>() -&gt; T,&nbsp;</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='https://doc.rust-lang.org/nightly/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
    278. 

  278. returns a mutable reference to the contained value.</p>
    279. 

  279. <h1 id="examples-22" class="section-header"><a href="#examples-22">Examples</a></h1>
    280. 

  280. <pre class="rust rust-example-rendered">
    281. 

  281. <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>;
    282. 

  282. 

  283. {
    284. 

  284.     <span class="kw">let</span> <span class="ident">y</span>: <span class="kw-2">&amp;</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>);
    285. 

  285.     <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">y</span>, <span class="kw-2">&amp;</span><span class="number">5</span>);
    286. 

  286. 

  287.     <span class="kw-2">*</span><span class="ident">y</span> <span class="op">=</span> <span class="number">7</span>;
    288. 

  288. }
    289. 

  289. 

  290. <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>
    291. 

  291. </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>(&amp;mut self) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    292. 

  292. <h1 id="examples-23" class="section-header"><a href="#examples-23">Examples</a></h1>
    293. 

  293. <pre class="rust rust-example-rendered">
    294. 

  294. <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>);
    295. 

  295. <span class="ident">x</span>.<span class="ident">take</span>();
    296. 

  296. <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">None</span>);
    297. 

  297. 

  298. <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">&lt;</span><span class="ident">u32</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    299. 

  299. <span class="ident">x</span>.<span class="ident">take</span>();
    300. 

  300. <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="prelude-val">None</span>);</pre>
    301. 

  301. </div></div><h3 id='impl-1' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;'a, T&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a </a>T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html" title="trait core::clone::Clone">Clone</a>,&nbsp;</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='https://doc.rust-lang.org/nightly/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) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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&lt;&amp;T&gt;</code> to an <code>Option&lt;T&gt;</code> by cloning the contents of the
    302. 

  302. option.</p>
    303. 

  303. <h1 id="examples-24" class="section-header"><a href="#examples-24">Examples</a></h1>
    304. 

  304. <pre class="rust rust-example-rendered">
    305. 

  305. <span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="number">12</span>;
    306. 

  306. <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">&amp;</span><span class="ident">x</span>);
    307. 

  307. <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">&amp;</span><span class="number">12</span>));
    308. 

  308. <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>();
    309. 

  309. <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>
    310. 

  310. </div></div><h3 id='impl-2' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;'a, T&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a mut </a>T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html" title="trait core::clone::Clone">Clone</a>,&nbsp;</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='https://doc.rust-lang.org/nightly/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) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</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='https://doc.rust-lang.org/nightly/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&lt;&amp;mut T&gt;</code> to an <code>Option&lt;T&gt;</code> by cloning the contents of the
    311. 

  311. option.</p>
    312. 

  312. <h1 id="examples-25" class="section-header"><a href="#examples-25">Examples</a></h1>
    313. 

  313. <pre class="rust rust-example-rendered">
    314. 

  314. <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>;
    315. 

  315. <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">&amp;</span><span class="kw-2">mut</span> <span class="ident">x</span>);
    316. 

  316. <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">&amp;</span><span class="kw-2">mut</span> <span class="number">12</span>));
    317. 

  317. <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>();
    318. 

  318. <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>
    319. 

  319. </div></div><h3 id='impl-3' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/default/trait.Default.html" title="trait core::default::Default">Default</a>,&nbsp;</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='https://doc.rust-lang.org/nightly/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) -&gt; T</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    320. 

  320. <p>Consumes the <code>self</code> argument then, if <a href="#variant.Some"><code>Some</code></a>, returns the contained
    321. 

  321. 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
    322. 

  322. type.</p>
    323. 

  323. <h1 id="examples-26" class="section-header"><a href="#examples-26">Examples</a></h1>
    324. 

  324. <p>Convert a string to an integer, turning poorly-formed strings
    325. 

  325. into 0 (the default value for integers). <a href="../../std/primitive.str.html#method.parse"><code>parse</code></a> converts
    326. 

  326. a string to any other type that implements <a href="../../std/str/trait.FromStr.html"><code>FromStr</code></a>, returning
    327. 

  327. <a href="#variant.None"><code>None</code></a> on error.</p>
    328. 

  328. 

  329. <pre class="rust rust-example-rendered">
    330. 

  330. <span class="kw">let</span> <span class="ident">good_year_from_input</span> <span class="op">=</span> <span class="string">&quot;1909&quot;</span>;
    331. 

  331. <span class="kw">let</span> <span class="ident">bad_year_from_input</span> <span class="op">=</span> <span class="string">&quot;190blarg&quot;</span>;
    332. 

  332. <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>();
    333. 

  333. <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>();
    334. 

  334. 

  335. <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">1909</span>, <span class="ident">good_year</span>);
    336. 

  336. <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0</span>, <span class="ident">bad_year</span>);</pre>
    337. 

  337. </div></div><h3 id='impl-4' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T, E&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;<a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;T, E&gt;&gt;</code><a href='#impl-4' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;, E&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>)</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>
    338. 

  338. <p><code>None</code> will be mapped to <code>Ok(None)</code>.
    339. 

  339. <code>Some(Ok(_))</code> and <code>Some(Err(_))</code> will be mapped to <code>Ok(Some(_))</code> and <code>Err(_)</code>.</p>
    340. 

  340. <h1 id="examples-27" class="section-header"><a href="#examples-27">Examples</a></h1>
    341. 

  341. <pre class="rust rust-example-rendered">
    342. 

  342. <span class="attribute">#![<span class="ident">feature</span>(<span class="ident">transpose_result</span>)]</span>
    343. 

  343. 

  344. <span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>, <span class="ident">Eq</span>, <span class="ident">PartialEq</span>)]</span>
    345. 

  345. <span class="kw">struct</span> <span class="ident">SomeErr</span>;
    346. 

  346. 

  347. <span class="kw">let</span> <span class="ident">x</span>: <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">i32</span><span class="op">&gt;</span>, <span class="ident">SomeErr</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">5</span>));
    348. 

  348. <span class="kw">let</span> <span class="ident">y</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">i32</span>, <span class="ident">SomeErr</span><span class="op">&gt;&gt;</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="prelude-val">Ok</span>(<span class="number">5</span>));
    349. 

  349. <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>());</pre>
    350. 

  350. </div></div>
    351. 

  351.                 <h2 id='implementations' class='small-section-header'>
    352. 

  352.                   Trait Implementations<a href='#implementations' class='anchor'></a>
    353. 

  353.                 </h2>
    354. 

  354.                 <div id='implementations-list'><h3 id='impl-Try' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/try/trait.Try.html" title="trait core::ops::try::Try">Try</a> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</code><a href='#impl-Try' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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='https://doc.rust-lang.org/nightly/core/ops/try/trait.Try.html#associatedtype.Ok' class="type">Ok</a> = T</code></span></h4>
    355. 

  355. <div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API.  (<code>try_trait</code>)</div></div><div class='docblock'><p>The type of this value when viewed as successful.</p>
    356. 

  356. </div><h4 id='associatedtype.Error' class="type"><span id='Error.t' class='invisible'><code>type <a href='https://doc.rust-lang.org/nightly/core/ops/try/trait.Try.html#associatedtype.Error' class="type">Error</a> = <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.NoneError.html" title="struct core::option::NoneError">NoneError</a></code></span></h4>
    357. 

  357. <div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API.  (<code>try_trait</code>)</div></div><div class='docblock'><p>The type of this value when viewed as failed.</p>
    358. 

  358. </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='https://doc.rust-lang.org/nightly/core/ops/try/trait.Try.html#tymethod.into_result' class='fnname'>into_result</a>(self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;T, <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.NoneError.html" title="struct core::option::NoneError">NoneError</a>&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>)</div></div><div class='docblock'><p>Applies the &quot;?&quot; 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="https://doc.rust-lang.org/nightly/core/ops/try/trait.Try.html#tymethod.into_result">Read more</a></p>
    359. 

  359. </div><h4 id='method.from_ok' class="method"><span id='from_ok.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/ops/try/trait.Try.html#tymethod.from_ok' class='fnname'>from_ok</a>(v: T) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/option.rs.html#1275-1277' 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>)</div></div><div class='docblock'><p>Wrap an OK value to construct the composite result. For example, <code>Result::Ok(x)</code> and <code>Result::from_ok(x)</code> are equivalent. <a href="https://doc.rust-lang.org/nightly/core/ops/try/trait.Try.html#tymethod.from_ok">Read more</a></p>
    360. 

  360. </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='https://doc.rust-lang.org/nightly/core/ops/try/trait.Try.html#tymethod.from_error' class='fnname'>from_error</a>(<a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.NoneError.html" title="struct core::option::NoneError">NoneError</a>) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>)</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="https://doc.rust-lang.org/nightly/core/ops/try/trait.Try.html#tymethod.from_error">Read more</a></p>
    361. 

  361. </div></div><h3 id='impl-Debug' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html" title="trait core::fmt::Debug">Debug</a> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html" title="trait core::fmt::Debug">Debug</a>,&nbsp;</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='https://doc.rust-lang.org/nightly/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='https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&amp;self, f: &amp;mut <a class="struct" href="https://doc.rust-lang.org/nightly/core/fmt/struct.Formatter.html" title="struct core::fmt::Formatter">Formatter</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, <a class="struct" href="https://doc.rust-lang.org/nightly/core/fmt/struct.Error.html" title="struct core::fmt::Error">Error</a>&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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="https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html#tymethod.fmt">Read more</a></p>
    362. 

  362. </div></div><h3 id='impl-Default' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <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>&lt;T&gt;</code><a href='#impl-Default' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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='https://doc.rust-lang.org/nightly/core/default/trait.Default.html#tymethod.default' class='fnname'>default</a>() -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    363. 

  363. </div></div><h3 id='impl-IntoIterator' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <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>&lt;T&gt;</code><a href='#impl-IntoIterator' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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='https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#associatedtype.Item' class="type">Item</a> = T</code></span></h4>
    364. 

  364. <div class='docblock'><p>The type of the elements being iterated over.</p>
    365. 

  365. </div><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>&lt;T&gt;</code></span></h4>
    366. 

  366. <div class='docblock'><p>Which kind of iterator are we turning this into?</p>
    367. 

  367. </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="https://doc.rust-lang.org/nightly/core/option/struct.IntoIter.html" title="struct core::option::IntoIter">IntoIter</a>&lt;A&gt;</span></div><div class="content hidden"><h3 class="important">Important traits for <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IntoIter.html" title="struct core::option::IntoIter">IntoIter</a>&lt;A&gt;</h3><code class="content"><span class="where fmt-newline">impl&lt;A&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html" title="trait core::iter::iterator::Iterator">Iterator</a> for <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IntoIter.html" title="struct core::option::IntoIter">IntoIter</a>&lt;A&gt;</span><span class="where fmt-newline">    type <a href='https://doc.rust-lang.org/nightly/core/iter/iterator/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='https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#tymethod.into_iter' class='fnname'>into_iter</a>(self) -&gt; <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IntoIter.html" title="struct core::option::IntoIter">IntoIter</a>&lt;T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    368. 

  368. <h1 id="examples-28" class="section-header"><a href="#examples-28">Examples</a></h1>
    369. 

  369. <pre class="rust rust-example-rendered">
    370. 

  370. <span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="string">&quot;string&quot;</span>);
    371. 

  371. <span class="kw">let</span> <span class="ident">v</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="ident">str</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">into_iter</span>().<span class="ident">collect</span>();
    372. 

  372. <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">v</span>, [<span class="string">&quot;string&quot;</span>]);
    373. 

  373. 

  374. <span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">None</span>;
    375. 

  375. <span class="kw">let</span> <span class="ident">v</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="ident">str</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">into_iter</span>().<span class="ident">collect</span>();
    376. 

  376. <span class="macro">assert</span><span class="macro">!</span>(<span class="ident">v</span>.<span class="ident">is_empty</span>());</pre>
    377. 

  377. </div></div><h3 id='impl-IntoIterator-1' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;'a, T&gt; <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 &amp;'a <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</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='https://doc.rust-lang.org/nightly/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-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 class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a </a>T</code></span></h4>
    378. 

  378. <div class='docblock'><p>The type of the elements being iterated over.</p>
    379. 

  379. </div><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>&lt;'a, T&gt;</code></span></h4>
    380. 

  380. <div class='docblock'><p>Which kind of iterator are we turning this into?</p>
    381. 

  381. </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="https://doc.rust-lang.org/nightly/core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a>&lt;'a, A&gt;</span></div><div class="content hidden"><h3 class="important">Important traits for <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a>&lt;'a, A&gt;</h3><code class="content"><span class="where fmt-newline">impl&lt;'a, A&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html" title="trait core::iter::iterator::Iterator">Iterator</a> for <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a>&lt;'a, A&gt;</span><span class="where fmt-newline">    type <a href='https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a </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='https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#tymethod.into_iter' class='fnname'>into_iter</a>(self) -&gt; <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.Iter.html" title="struct core::option::Iter">Iter</a>&lt;'a, T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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="https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#tymethod.into_iter">Read more</a></p>
    382. 

  382. </div></div><h3 id='impl-IntoIterator-2' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;'a, T&gt; <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 &amp;'a mut <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</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='https://doc.rust-lang.org/nightly/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-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 class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a mut </a>T</code></span></h4>
    383. 

  383. <div class='docblock'><p>The type of the elements being iterated over.</p>
    384. 

  384. </div><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>&lt;'a, T&gt;</code></span></h4>
    385. 

  385. <div class='docblock'><p>Which kind of iterator are we turning this into?</p>
    386. 

  386. </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="https://doc.rust-lang.org/nightly/core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a>&lt;'a, A&gt;</span></div><div class="content hidden"><h3 class="important">Important traits for <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a>&lt;'a, A&gt;</h3><code class="content"><span class="where fmt-newline">impl&lt;'a, A&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html" title="trait core::iter::iterator::Iterator">Iterator</a> for <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a>&lt;'a, A&gt;</span><span class="where fmt-newline">    type <a href='https://doc.rust-lang.org/nightly/core/iter/iterator/trait.Iterator.html#associatedtype.Item' class="type">Item</a> = <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;'a mut </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='https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#tymethod.into_iter' class='fnname'>into_iter</a>(self) -&gt; <a class="struct" href="https://doc.rust-lang.org/nightly/core/option/struct.IterMut.html" title="struct core::option::IterMut">IterMut</a>&lt;'a, T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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="https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html#tymethod.into_iter">Read more</a></p>
    387. 

  387. </div></div><h3 id='impl-Copy' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <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>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Copy.html" title="trait core::marker::Copy">Copy</a>,&nbsp;</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='https://doc.rust-lang.org/nightly/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-From%3CT%3E' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.From.html" title="trait core::convert::From">From</a>&lt;T&gt; for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</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='https://doc.rust-lang.org/nightly/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='https://doc.rust-lang.org/nightly/core/convert/trait.From.html#tymethod.from' class='fnname'>from</a>(val: T) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    388. 

  388. </div></div><h3 id='impl-Clone' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <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>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html" title="trait core::clone::Clone">Clone</a>,&nbsp;</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='https://doc.rust-lang.org/nightly/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='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#tymethod.clone' class='fnname'>clone</a>(&amp;self) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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="https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#tymethod.clone">Read more</a></p>
    389. 

  389. </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='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#method.clone_from' class='fnname'>clone_from</a>(&amp;mut self, source: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;</a>Self)</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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="https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#method.clone_from">Read more</a></p>
    390. 

  390. </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&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html" title="trait core::cmp::PartialOrd">PartialOrd</a>&lt;<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;&gt; for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html" title="trait core::cmp::PartialOrd">PartialOrd</a>&lt;T&gt;,&nbsp;</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='https://doc.rust-lang.org/nightly/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='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#tymethod.partial_cmp' class='fnname'>partial_cmp</a>(&amp;self, other: &amp;<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;<a class="enum" href="https://doc.rust-lang.org/nightly/core/cmp/enum.Ordering.html" title="enum core::cmp::Ordering">Ordering</a>&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#tymethod.partial_cmp">Read more</a></p>
    391. 

  391. </div><h4 id='method.lt' class="method"><span id='lt.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#method.lt' class='fnname'>lt</a>(&amp;self, other: &amp;<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>&lt;</code> operator. <a href="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#method.lt">Read more</a></p>
    392. 

  392. </div><h4 id='method.le' class="method"><span id='le.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#method.le' class='fnname'>le</a>(&amp;self, other: &amp;<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>&lt;=</code> operator. <a href="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#method.le">Read more</a></p>
    393. 

  393. </div><h4 id='method.gt' class="method"><span id='gt.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#method.gt' class='fnname'>gt</a>(&amp;self, other: &amp;<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>&gt;</code> operator. <a href="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#method.gt">Read more</a></p>
    394. 

  394. </div><h4 id='method.ge' class="method"><span id='ge.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#method.ge' class='fnname'>ge</a>(&amp;self, other: &amp;<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>&gt;=</code> operator. <a href="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialOrd.html#method.ge">Read more</a></p>
    395. 

  395. </div></div><h3 id='impl-Ord' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <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>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.Ord.html" title="trait core::cmp::Ord">Ord</a>,&nbsp;</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='https://doc.rust-lang.org/nightly/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='https://doc.rust-lang.org/nightly/core/cmp/trait.Ord.html#tymethod.cmp' class='fnname'>cmp</a>(&amp;self, other: &amp;<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/cmp/enum.Ordering.html" title="enum core::cmp::Ordering">Ordering</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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="https://doc.rust-lang.org/nightly/core/cmp/trait.Ord.html#tymethod.cmp">Read more</a></p>
    396. 

  396. </div><h4 id='method.max' class="method"><span id='max.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.Ord.html#method.max' class='fnname'>max</a>(self, other: Self) -&gt; 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='https://doc.rust-lang.org/nightly/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="https://doc.rust-lang.org/nightly/core/cmp/trait.Ord.html#method.max">Read more</a></p>
    397. 

  397. </div><h4 id='method.min' class="method"><span id='min.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.Ord.html#method.min' class='fnname'>min</a>(self, other: Self) -&gt; 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='https://doc.rust-lang.org/nightly/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="https://doc.rust-lang.org/nightly/core/cmp/trait.Ord.html#method.min">Read more</a></p>
    398. 

  398. </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&lt;A, V&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/traits/trait.FromIterator.html" title="trait core::iter::traits::FromIterator">FromIterator</a>&lt;<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;A&gt;&gt; for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;V&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;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>&lt;A&gt;,&nbsp;</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='https://doc.rust-lang.org/nightly/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='https://doc.rust-lang.org/nightly/core/iter/traits/trait.FromIterator.html#tymethod.from_iter' class='fnname'>from_iter</a>&lt;I&gt;(iter: I) -&gt; <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;V&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;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>&lt;Item = <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;A&gt;&gt;,&nbsp;</span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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
    399. 

  399. 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
    400. 

  400. container with the values of each <code>Option</code> is returned.</p>
    401. 

  401. <p>Here is an example which increments every integer in a vector,
    402. 

  402. checking for overflow:</p>
    403. 

  403. 

  404. <pre class="rust rust-example-rendered">
    405. 

  405. <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">u16</span>;
    406. 

  406. 

  407. <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>];
    408. 

  408. <span class="kw">let</span> <span class="ident">res</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">u16</span><span class="op">&gt;&gt;</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">&amp;</span><span class="ident">x</span>: <span class="kw-2">&amp;</span><span class="ident">u16</span><span class="op">|</span>
    409. 

  409.     <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> }
    410. 

  410.     <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>) }
    411. 

  411. ).<span class="ident">collect</span>();
    412. 

  412. <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>
    413. 

  413. </div></div><h3 id='impl-Eq' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <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>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.Eq.html" title="trait core::cmp::Eq">Eq</a>,&nbsp;</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='https://doc.rust-lang.org/nightly/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-PartialEq%3COption%3CT%3E%3E' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialEq.html" title="trait core::cmp::PartialEq">PartialEq</a>&lt;<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;&gt; for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialEq.html" title="trait core::cmp::PartialEq">PartialEq</a>&lt;T&gt;,&nbsp;</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='https://doc.rust-lang.org/nightly/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='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialEq.html#tymethod.eq' class='fnname'>eq</a>(&amp;self, other: &amp;<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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="https://doc.rust-lang.org/nightly/core/cmp/trait.PartialEq.html#tymethod.eq">Read more</a></p>
    414. 

  414. </div><h4 id='method.ne' class="method"><span id='ne.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/cmp/trait.PartialEq.html#method.ne' class='fnname'>ne</a>(&amp;self, other: &amp;<a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt;) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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>
    415. 

  415. </div></div><h3 id='impl-Hash' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <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>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/hash/trait.Hash.html" title="trait core::hash::Hash">Hash</a>,&nbsp;</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='https://doc.rust-lang.org/nightly/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='https://doc.rust-lang.org/nightly/core/hash/trait.Hash.html#tymethod.hash' class='fnname'>hash</a>&lt;__HT&gt;(&amp;self, state: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>__HT) <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;__HT: <a class="trait" href="https://doc.rust-lang.org/nightly/core/hash/trait.Hasher.html" title="trait core::hash::Hasher">Hasher</a>,&nbsp;</span></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='https://doc.rust-lang.org/nightly/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="https://doc.rust-lang.org/nightly/core/hash/trait.Hash.html#tymethod.hash">Read more</a></p>
    416. 

  416. </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='https://doc.rust-lang.org/nightly/core/hash/trait.Hash.html#method.hash_slice' class='fnname'>hash_slice</a>&lt;H&gt;(data: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.slice.html">&amp;[Self]</a>, state: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.reference.html">&amp;mut </a>H) <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;H: <a class="trait" href="https://doc.rust-lang.org/nightly/core/hash/trait.Hasher.html" title="trait core::hash::Hasher">Hasher</a>,&nbsp;</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='https://doc.rust-lang.org/nightly/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="https://doc.rust-lang.org/nightly/core/hash/trait.Hash.html#method.hash_slice">Read more</a></p>
    417. 

  417. </div></div></div>
    418. 

  418.                 <h2 id='synthetic-implementations' class='small-section-header'>
    419. 

  419.                   Auto Trait Implementations<a href='#synthetic-implementations' class='anchor'></a>
    420. 

  420.                 </h2>
    421. 

  421.                 <div id='synthetic-implementations-list'>
    422. 

  422.             <h3 id='impl-Send' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a>,&nbsp;</span></code><a href='#impl-Send' class='anchor'></a></span></td><td><span class='out-of-band'></span></td></tr></tbody></table></h3><div class='impl-items'></div><h3 id='impl-Sync' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sync.html" title="trait core::marker::Sync">Sync</a> for <a class="enum" href="../enum_primitive/enum.Option.html" title="enum enum_primitive::Option">Option</a>&lt;T&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sync.html" title="trait core::marker::Sync">Sync</a>,&nbsp;</span></code><a href='#impl-Sync' class='anchor'></a></span></td><td><span class='out-of-band'></span></td></tr></tbody></table></h3><div class='impl-items'></div></div></section><section id="search" class="content hidden"></section><section class="footer"></section><aside id="help" class="hidden"><div><h1 class="hidden">Help</h1><div class="shortcuts"><h2>Keyboard Shortcuts</h2><dl><dt><kbd>?</kbd></dt><dd>Show this help dialog</dd><dt><kbd>S</kbd></dt><dd>Focus the search field</dd><dt><kbd>↑</kbd></dt><dd>Move up in search results</dd><dt><kbd>↓</kbd></dt><dd>Move down in search results</dd><dt><kbd>↹</kbd></dt><dd>Switch tab</dd><dt><kbd>&#9166;</kbd></dt><dd>Go to active search result</dd><dt><kbd>+</kbd></dt><dd>Expand all sections</dd><dt><kbd>-</kbd></dt><dd>Collapse all sections</dd></dl></div><div class="infos"><h2>Search Tricks</h2><p>Prefix searches with a type followed by a colon (e.g. <code>fn:</code>) to restrict the search to a given type.</p><p>Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>.</p><p>Search functions by type signature (e.g. <code>vec -> usize</code> or <code>* -> vec</code>)</p><p>Search multiple things at once by splitting your query with comma (e.g. <code>str,u8</code> or <code>String,struct:Vec,test</code>)</p></div></div></aside><script>window.rootPath = "../";window.currentCrate = "enum_primitive";</script><script src="../aliases.js"></script><script src="../main.js"></script><script defer src="../search-index.js"></script></body></html>
    423.