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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="API documentation for the Rust `Formatter` struct in crate `core`."><meta name="keywords" content="rust, rustlang, rust-lang, Formatter"><title>core::fmt::Formatter - Rust</title><link rel="stylesheet" type="text/css" href="../../normalize.css"><link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../dark.css"><link rel="stylesheet" type="text/css" href="../../light.css" id="themeStyle"><script src="../../storage.js"></script><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></head><body class="rustdoc struct"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">&#9776;</div><a href='../../core/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a><p class='location'>Struct Formatter</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#methods">Methods</a><div class="sidebar-links"><a href="#method.pad_integral">pad_integral</a><a href="#method.pad">pad</a><a href="#method.write_str">write_str</a><a href="#method.write_fmt">write_fmt</a><a href="#method.flags">flags</a><a href="#method.fill">fill</a><a href="#method.align">align</a><a href="#method.width">width</a><a href="#method.precision">precision</a><a href="#method.sign_plus">sign_plus</a><a href="#method.sign_minus">sign_minus</a><a href="#method.alternate">alternate</a><a href="#method.sign_aware_zero_pad">sign_aware_zero_pad</a><a href="#method.debug_struct">debug_struct</a><a href="#method.debug_tuple">debug_tuple</a><a href="#method.debug_list">debug_list</a><a href="#method.debug_set">debug_set</a><a href="#method.debug_map">debug_map</a></div><a class="sidebar-title" href="#implementations">Trait Implementations</a><div class="sidebar-links"><a href="#impl-Write">Write</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'>core</a>::<wbr><a href='index.html'>fmt</a></p><script>window.sidebarCurrent = {name: 'Formatter', ty: 'struct', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../../settings.html"><img src="../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='in-band'>Struct <a href='../index.html'>core</a>::<wbr><a href='index.html'>fmt</a>::<wbr><a class="struct" href=''>Formatter</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='../../src/core/fmt/mod.rs.html#251-261' title='goto source code'>[src]</a></span></h1><div class="docblock type-decl"><pre class='rust struct'>pub struct Formatter&lt;'a&gt; { /* fields omitted */ }</pre></div><div class='docblock'><p>A struct to represent both where to emit formatting strings to and how they
should be formatted. A mutable version of this is passed to all formatting
traits.</p>
</div>
                    <h2 id='methods' class='small-section-header'>
                      Methods<a href='#methods' class='anchor'></a>
                    </h2>
                <h3 id='impl' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;'a&gt; <a class="struct" href="../../core/fmt/struct.Formatter.html" title="struct core::fmt::Formatter">Formatter</a>&lt;'a&gt;</code><a href='#impl' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1063-1818' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.pad_integral' class="method"><span id='pad_integral.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.pad_integral' class='fnname'>pad_integral</a>(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;is_nonnegative: bool, <br>&nbsp;&nbsp;&nbsp;&nbsp;prefix: &amp;str, <br>&nbsp;&nbsp;&nbsp;&nbsp;buf: &amp;str<br>) -&gt; <a class="type" href="../../core/fmt/type.Result.html" title="type core::fmt::Result">Result</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1136-1193' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Performs the correct padding for an integer which has already been
emitted into a str. The str should <em>not</em> contain the sign for the
integer, that will be added by this method.</p>
<h1 id="arguments" class="section-header"><a href="#arguments">Arguments</a></h1>
<ul>
<li>is_nonnegative - whether the original integer was either positive or zero.</li>
<li>prefix - if the '#' character (Alternate) is provided, this
is the prefix to put in front of the number.</li>
<li>buf - the byte array that the number has been formatted into</li>
</ul>
<p>This function will correctly account for the flags provided as well as
the minimum width. It will not take precision into account.</p>
</div><h4 id='method.pad' class="method"><span id='pad.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.pad' class='fnname'>pad</a>(&amp;mut self, s: &amp;str) -&gt; <a class="type" href="../../core/fmt/type.Result.html" title="type core::fmt::Result">Result</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1224-1266' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>This function takes a string slice and emits it to the internal buffer
after applying the relevant formatting flags specified. The flags
recognized for generic strings are:</p>
<ul>
<li>width - the minimum width of what to emit</li>
<li>fill/align - what to emit and where to emit it if the string
provided needs to be padded</li>
<li>precision - the maximum length to emit, the string is truncated if it
is longer than this length</li>
</ul>
<p>Notably this function ignores the <code>flag</code> parameters.</p>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;

<span class="kw">struct</span> <span class="ident">Foo</span>;

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Display</span> <span class="kw">for</span> <span class="ident">Foo</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">formatter</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="ident">formatter</span>.<span class="ident">pad</span>(<span class="string">&quot;Foo&quot;</span>)
    }
}

<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:&lt;4}&quot;</span>, <span class="ident">Foo</span>), <span class="string">&quot;Foo &quot;</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:0&gt;4}&quot;</span>, <span class="ident">Foo</span>), <span class="string">&quot;0Foo&quot;</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0A%0Astruct%20Foo%3B%0A%0Aimpl%20fmt%3A%3ADisplay%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20formatter%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20formatter.pad(%22Foo%22)%0A%20%20%20%20%7D%0A%7D%0A%0Aassert_eq!(%26format!(%22%7B%3A%3C4%7D%22%2C%20Foo)%2C%20%22Foo%20%22)%3B%0Aassert_eq!(%26format!(%22%7B%3A0%3E4%7D%22%2C%20Foo)%2C%20%220Foo%22)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.write_str' class="method"><span id='write_str.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.write_str' class='fnname'>write_str</a>(&amp;mut self, data: &amp;str) -&gt; <a class="type" href="../../core/fmt/type.Result.html" title="type core::fmt::Result">Result</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1385-1387' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Writes some data to the underlying buffer contained within this
formatter.</p>
</div><h4 id='method.write_fmt' class="method"><span id='write_fmt.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.write_fmt' class='fnname'>write_fmt</a>(&amp;mut self, fmt: <a class="struct" href="../../core/fmt/struct.Arguments.html" title="struct core::fmt::Arguments">Arguments</a>) -&gt; <a class="type" href="../../core/fmt/type.Result.html" title="type core::fmt::Result">Result</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1391-1393' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Writes some formatted information into this instance.</p>
</div><h4 id='method.flags' class="method"><span id='flags.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.flags' class='fnname'>flags</a>(&amp;self) -&gt; u32</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1400' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='stability'><div class='stab deprecated'>Deprecated since 1.24.0<p>: use the <code>sign_plus</code>, <code>sign_minus</code>, <code>alternate</code>, or <code>sign_aware_zero_pad</code> methods instead</p>
</div></div><div class='docblock'><p>Flags for formatting</p>
</div><h4 id='method.fill' class="method"><span id='fill.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.fill' class='fnname'>fill</a>(&amp;self) -&gt; char</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.5.0'>1.5.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1430' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Character used as 'fill' whenever there is alignment.</p>
<h1 id="examples-1" class="section-header"><a href="#examples-1">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;

<span class="kw">struct</span> <span class="ident">Foo</span>;

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Display</span> <span class="kw">for</span> <span class="ident">Foo</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">formatter</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="kw">let</span> <span class="ident">c</span> <span class="op">=</span> <span class="ident">formatter</span>.<span class="ident">fill</span>();
        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">width</span>) <span class="op">=</span> <span class="ident">formatter</span>.<span class="ident">width</span>() {
            <span class="kw">for</span> <span class="kw">_</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">width</span> {
                <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>, <span class="string">&quot;{}&quot;</span>, <span class="ident">c</span>)<span class="question-mark">?</span>;
            }
            <span class="prelude-val">Ok</span>(())
        } <span class="kw">else</span> {
            <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>, <span class="string">&quot;{}&quot;</span>, <span class="ident">c</span>)
        }
    }
}

<span class="comment">// We set alignment to the left with &quot;&gt;&quot;.</span>
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:G&gt;3}&quot;</span>, <span class="ident">Foo</span>), <span class="string">&quot;GGG&quot;</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:t&gt;6}&quot;</span>, <span class="ident">Foo</span>), <span class="string">&quot;tttttt&quot;</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0A%0Astruct%20Foo%3B%0A%0Aimpl%20fmt%3A%3ADisplay%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20formatter%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20let%20c%20%3D%20formatter.fill()%3B%0A%20%20%20%20%20%20%20%20if%20let%20Some(width)%20%3D%20formatter.width()%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20for%20_%20in%200..width%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20write!(formatter%2C%20%22%7B%7D%22%2C%20c)%3F%3B%0A%20%20%20%20%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%20%20%20%20%20%20%20%20Ok(())%0A%20%20%20%20%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20write!(formatter%2C%20%22%7B%7D%22%2C%20c)%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%7D%0A%7D%0A%0A%2F%2F%20We%20set%20alignment%20to%20the%20left%20with%20%22%3E%22.%0Aassert_eq!(%26format!(%22%7B%3AG%3E3%7D%22%2C%20Foo)%2C%20%22GGG%22)%3B%0Aassert_eq!(%26format!(%22%7B%3At%3E6%7D%22%2C%20Foo)%2C%20%22tttttt%22)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.align' class="method"><span id='align.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.align' class='fnname'>align</a>(&amp;self) -&gt; <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a>&lt;<a class="enum" href="../../core/fmt/enum.Alignment.html" title="enum core::fmt::Alignment">Alignment</a>&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.28.0'>1.28.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1466-1473' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Flag indicating what form of alignment was requested.</p>
<h1 id="examples-2" class="section-header"><a href="#examples-2">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">core</span>;

<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>::{<span class="self">self</span>, <span class="ident">Alignment</span>};

<span class="kw">struct</span> <span class="ident">Foo</span>;

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Display</span> <span class="kw">for</span> <span class="ident">Foo</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">formatter</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">s</span>) <span class="op">=</span> <span class="ident">formatter</span>.<span class="ident">align</span>() {
            <span class="kw">match</span> <span class="ident">s</span> {
                <span class="ident">Alignment</span>::<span class="ident">Left</span>    <span class="op">=&gt;</span> <span class="string">&quot;left&quot;</span>,
                <span class="ident">Alignment</span>::<span class="ident">Right</span>   <span class="op">=&gt;</span> <span class="string">&quot;right&quot;</span>,
                <span class="ident">Alignment</span>::<span class="ident">Center</span>  <span class="op">=&gt;</span> <span class="string">&quot;center&quot;</span>,
            }
        } <span class="kw">else</span> {
            <span class="string">&quot;into the void&quot;</span>
        };
        <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>, <span class="string">&quot;{}&quot;</span>, <span class="ident">s</span>)
    }
}

<span class="kw">fn</span> <span class="ident">main</span>() {
    <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:&lt;}&quot;</span>, <span class="ident">Foo</span>), <span class="string">&quot;left&quot;</span>);
    <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:&gt;}&quot;</span>, <span class="ident">Foo</span>), <span class="string">&quot;right&quot;</span>);
    <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:^}&quot;</span>, <span class="ident">Foo</span>), <span class="string">&quot;center&quot;</span>);
    <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{}&quot;</span>, <span class="ident">Foo</span>), <span class="string">&quot;into the void&quot;</span>);
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Aextern%20crate%20core%3B%0A%0Ause%20std%3A%3Afmt%3A%3A%7Bself%2C%20Alignment%7D%3B%0A%0Astruct%20Foo%3B%0A%0Aimpl%20fmt%3A%3ADisplay%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20formatter%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20let%20s%20%3D%20if%20let%20Some(s)%20%3D%20formatter.align()%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20match%20s%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20Alignment%3A%3ALeft%20%20%20%20%3D%3E%20%22left%22%2C%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20Alignment%3A%3ARight%20%20%20%3D%3E%20%22right%22%2C%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20Alignment%3A%3ACenter%20%20%3D%3E%20%22center%22%2C%0A%20%20%20%20%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20%22into%20the%20void%22%0A%20%20%20%20%20%20%20%20%7D%3B%0A%20%20%20%20%20%20%20%20write!(formatter%2C%20%22%7B%7D%22%2C%20s)%0A%20%20%20%20%7D%0A%7D%0A%0Afn%20main()%20%7B%0A%20%20%20%20assert_eq!(%26format!(%22%7B%3A%3C%7D%22%2C%20Foo)%2C%20%22left%22)%3B%0A%20%20%20%20assert_eq!(%26format!(%22%7B%3A%3E%7D%22%2C%20Foo)%2C%20%22right%22)%3B%0A%20%20%20%20assert_eq!(%26format!(%22%7B%3A%5E%7D%22%2C%20Foo)%2C%20%22center%22)%3B%0A%20%20%20%20assert_eq!(%26format!(%22%7B%7D%22%2C%20Foo)%2C%20%22into%20the%20void%22)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.width' class="method"><span id='width.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.width' class='fnname'>width</a>(&amp;self) -&gt; <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a>&lt;usize&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.5.0'>1.5.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1500' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Optionally specified integer width that the output should be.</p>
<h1 id="examples-3" class="section-header"><a href="#examples-3">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;

<span class="kw">struct</span> <span class="ident">Foo</span>(<span class="ident">i32</span>);

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Display</span> <span class="kw">for</span> <span class="ident">Foo</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">formatter</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">width</span>) <span class="op">=</span> <span class="ident">formatter</span>.<span class="ident">width</span>() {
            <span class="comment">// If we received a width, we use it</span>
            <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>, <span class="string">&quot;{:width$}&quot;</span>, <span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;Foo({})&quot;</span>, <span class="self">self</span>.<span class="number">0</span>), <span class="ident">width</span> <span class="op">=</span> <span class="ident">width</span>)
        } <span class="kw">else</span> {
            <span class="comment">// Otherwise we do nothing special</span>
            <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>, <span class="string">&quot;Foo({})&quot;</span>, <span class="self">self</span>.<span class="number">0</span>)
        }
    }
}

<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:10}&quot;</span>, <span class="ident">Foo</span>(<span class="number">23</span>)), <span class="string">&quot;Foo(23)   &quot;</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{}&quot;</span>, <span class="ident">Foo</span>(<span class="number">23</span>)), <span class="string">&quot;Foo(23)&quot;</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0A%0Astruct%20Foo(i32)%3B%0A%0Aimpl%20fmt%3A%3ADisplay%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20formatter%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20if%20let%20Some(width)%20%3D%20formatter.width()%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20%2F%2F%20If%20we%20received%20a%20width%2C%20we%20use%20it%0A%20%20%20%20%20%20%20%20%20%20%20%20write!(formatter%2C%20%22%7B%3Awidth%24%7D%22%2C%20%26format!(%22Foo(%7B%7D)%22%2C%20self.0)%2C%20width%20%3D%20width)%0A%20%20%20%20%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20%2F%2F%20Otherwise%20we%20do%20nothing%20special%0A%20%20%20%20%20%20%20%20%20%20%20%20write!(formatter%2C%20%22Foo(%7B%7D)%22%2C%20self.0)%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%7D%0A%7D%0A%0Aassert_eq!(%26format!(%22%7B%3A10%7D%22%2C%20Foo(23))%2C%20%22Foo(23)%20%20%20%22)%3B%0Aassert_eq!(%26format!(%22%7B%7D%22%2C%20Foo(23))%2C%20%22Foo(23)%22)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.precision' class="method"><span id='precision.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.precision' class='fnname'>precision</a>(&amp;self) -&gt; <a class="enum" href="../../core/option/enum.Option.html" title="enum core::option::Option">Option</a>&lt;usize&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.5.0'>1.5.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1527' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Optionally specified precision for numeric types.</p>
<h1 id="examples-4" class="section-header"><a href="#examples-4">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;

<span class="kw">struct</span> <span class="ident">Foo</span>(<span class="ident">f32</span>);

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Display</span> <span class="kw">for</span> <span class="ident">Foo</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">formatter</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">precision</span>) <span class="op">=</span> <span class="ident">formatter</span>.<span class="ident">precision</span>() {
            <span class="comment">// If we received a precision, we use it.</span>
            <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>, <span class="string">&quot;Foo({1:.*})&quot;</span>, <span class="ident">precision</span>, <span class="self">self</span>.<span class="number">0</span>)
        } <span class="kw">else</span> {
            <span class="comment">// Otherwise we default to 2.</span>
            <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>, <span class="string">&quot;Foo({:.2})&quot;</span>, <span class="self">self</span>.<span class="number">0</span>)
        }
    }
}

<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:.4}&quot;</span>, <span class="ident">Foo</span>(<span class="number">23.2</span>)), <span class="string">&quot;Foo(23.2000)&quot;</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{}&quot;</span>, <span class="ident">Foo</span>(<span class="number">23.2</span>)), <span class="string">&quot;Foo(23.20)&quot;</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0A%0Astruct%20Foo(f32)%3B%0A%0Aimpl%20fmt%3A%3ADisplay%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20formatter%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20if%20let%20Some(precision)%20%3D%20formatter.precision()%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20%2F%2F%20If%20we%20received%20a%20precision%2C%20we%20use%20it.%0A%20%20%20%20%20%20%20%20%20%20%20%20write!(formatter%2C%20%22Foo(%7B1%3A.*%7D)%22%2C%20precision%2C%20self.0)%0A%20%20%20%20%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20%2F%2F%20Otherwise%20we%20default%20to%202.%0A%20%20%20%20%20%20%20%20%20%20%20%20write!(formatter%2C%20%22Foo(%7B%3A.2%7D)%22%2C%20self.0)%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%7D%0A%7D%0A%0Aassert_eq!(%26format!(%22%7B%3A.4%7D%22%2C%20Foo(23.2))%2C%20%22Foo(23.2000)%22)%3B%0Aassert_eq!(%26format!(%22%7B%7D%22%2C%20Foo(23.2))%2C%20%22Foo(23.20)%22)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.sign_plus' class="method"><span id='sign_plus.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.sign_plus' class='fnname'>sign_plus</a>(&amp;self) -&gt; bool</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.5.0'>1.5.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1555' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Determines if the <code>+</code> flag was specified.</p>
<h1 id="examples-5" class="section-header"><a href="#examples-5">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;

<span class="kw">struct</span> <span class="ident">Foo</span>(<span class="ident">i32</span>);

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Display</span> <span class="kw">for</span> <span class="ident">Foo</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">formatter</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="kw">if</span> <span class="ident">formatter</span>.<span class="ident">sign_plus</span>() {
            <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>,
                   <span class="string">&quot;Foo({}{})&quot;</span>,
                   <span class="kw">if</span> <span class="self">self</span>.<span class="number">0</span> <span class="op">&lt;</span> <span class="number">0</span> { <span class="string">&#39;-&#39;</span> } <span class="kw">else</span> { <span class="string">&#39;+&#39;</span> },
                   <span class="self">self</span>.<span class="number">0</span>)
        } <span class="kw">else</span> {
            <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>, <span class="string">&quot;Foo({})&quot;</span>, <span class="self">self</span>.<span class="number">0</span>)
        }
    }
}

<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:+}&quot;</span>, <span class="ident">Foo</span>(<span class="number">23</span>)), <span class="string">&quot;Foo(+23)&quot;</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{}&quot;</span>, <span class="ident">Foo</span>(<span class="number">23</span>)), <span class="string">&quot;Foo(23)&quot;</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0A%0Astruct%20Foo(i32)%3B%0A%0Aimpl%20fmt%3A%3ADisplay%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20formatter%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20if%20formatter.sign_plus()%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20write!(formatter%2C%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%22Foo(%7B%7D%7B%7D)%22%2C%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20if%20self.0%20%3C%200%20%7B%20'-'%20%7D%20else%20%7B%20'%2B'%20%7D%2C%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20self.0)%0A%20%20%20%20%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20write!(formatter%2C%20%22Foo(%7B%7D)%22%2C%20self.0)%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%7D%0A%7D%0A%0Aassert_eq!(%26format!(%22%7B%3A%2B%7D%22%2C%20Foo(23))%2C%20%22Foo(%2B23)%22)%3B%0Aassert_eq!(%26format!(%22%7B%7D%22%2C%20Foo(23))%2C%20%22Foo(23)%22)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.sign_minus' class="method"><span id='sign_minus.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.sign_minus' class='fnname'>sign_minus</a>(&amp;self) -&gt; bool</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.5.0'>1.5.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1581' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Determines if the <code>-</code> flag was specified.</p>
<h1 id="examples-6" class="section-header"><a href="#examples-6">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;

<span class="kw">struct</span> <span class="ident">Foo</span>(<span class="ident">i32</span>);

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Display</span> <span class="kw">for</span> <span class="ident">Foo</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">formatter</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="kw">if</span> <span class="ident">formatter</span>.<span class="ident">sign_minus</span>() {
            <span class="comment">// You want a minus sign? Have one!</span>
            <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>, <span class="string">&quot;-Foo({})&quot;</span>, <span class="self">self</span>.<span class="number">0</span>)
        } <span class="kw">else</span> {
            <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>, <span class="string">&quot;Foo({})&quot;</span>, <span class="self">self</span>.<span class="number">0</span>)
        }
    }
}

<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:-}&quot;</span>, <span class="ident">Foo</span>(<span class="number">23</span>)), <span class="string">&quot;-Foo(23)&quot;</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{}&quot;</span>, <span class="ident">Foo</span>(<span class="number">23</span>)), <span class="string">&quot;Foo(23)&quot;</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0A%0Astruct%20Foo(i32)%3B%0A%0Aimpl%20fmt%3A%3ADisplay%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20formatter%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20if%20formatter.sign_minus()%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20%2F%2F%20You%20want%20a%20minus%20sign%3F%20Have%20one!%0A%20%20%20%20%20%20%20%20%20%20%20%20write!(formatter%2C%20%22-Foo(%7B%7D)%22%2C%20self.0)%0A%20%20%20%20%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20write!(formatter%2C%20%22Foo(%7B%7D)%22%2C%20self.0)%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%7D%0A%7D%0A%0Aassert_eq!(%26format!(%22%7B%3A-%7D%22%2C%20Foo(23))%2C%20%22-Foo(23)%22)%3B%0Aassert_eq!(%26format!(%22%7B%7D%22%2C%20Foo(23))%2C%20%22Foo(23)%22)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.alternate' class="method"><span id='alternate.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.alternate' class='fnname'>alternate</a>(&amp;self) -&gt; bool</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.5.0'>1.5.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1606' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Determines if the <code>#</code> flag was specified.</p>
<h1 id="examples-7" class="section-header"><a href="#examples-7">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;

<span class="kw">struct</span> <span class="ident">Foo</span>(<span class="ident">i32</span>);

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Display</span> <span class="kw">for</span> <span class="ident">Foo</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">formatter</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="kw">if</span> <span class="ident">formatter</span>.<span class="ident">alternate</span>() {
            <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>, <span class="string">&quot;Foo({})&quot;</span>, <span class="self">self</span>.<span class="number">0</span>)
        } <span class="kw">else</span> {
            <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>, <span class="string">&quot;{}&quot;</span>, <span class="self">self</span>.<span class="number">0</span>)
        }
    }
}

<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:#}&quot;</span>, <span class="ident">Foo</span>(<span class="number">23</span>)), <span class="string">&quot;Foo(23)&quot;</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{}&quot;</span>, <span class="ident">Foo</span>(<span class="number">23</span>)), <span class="string">&quot;23&quot;</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0A%0Astruct%20Foo(i32)%3B%0A%0Aimpl%20fmt%3A%3ADisplay%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20formatter%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20if%20formatter.alternate()%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20write!(formatter%2C%20%22Foo(%7B%7D)%22%2C%20self.0)%0A%20%20%20%20%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20write!(formatter%2C%20%22%7B%7D%22%2C%20self.0)%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%7D%0A%7D%0A%0Aassert_eq!(%26format!(%22%7B%3A%23%7D%22%2C%20Foo(23))%2C%20%22Foo(23)%22)%3B%0Aassert_eq!(%26format!(%22%7B%7D%22%2C%20Foo(23))%2C%20%2223%22)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.sign_aware_zero_pad' class="method"><span id='sign_aware_zero_pad.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.sign_aware_zero_pad' class='fnname'>sign_aware_zero_pad</a>(&amp;self) -&gt; bool</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.5.0'>1.5.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1629-1631' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Determines if the <code>0</code> flag was specified.</p>
<h1 id="examples-8" class="section-header"><a href="#examples-8">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;

<span class="kw">struct</span> <span class="ident">Foo</span>(<span class="ident">i32</span>);

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Display</span> <span class="kw">for</span> <span class="ident">Foo</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">formatter</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="macro">assert</span><span class="macro">!</span>(<span class="ident">formatter</span>.<span class="ident">sign_aware_zero_pad</span>());
        <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">formatter</span>.<span class="ident">width</span>(), <span class="prelude-val">Some</span>(<span class="number">4</span>));
        <span class="comment">// We ignore the formatter&#39;s options.</span>
        <span class="macro">write</span><span class="macro">!</span>(<span class="ident">formatter</span>, <span class="string">&quot;{}&quot;</span>, <span class="self">self</span>.<span class="number">0</span>)
    }
}

<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:04}&quot;</span>, <span class="ident">Foo</span>(<span class="number">23</span>)), <span class="string">&quot;23&quot;</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0A%0Astruct%20Foo(i32)%3B%0A%0Aimpl%20fmt%3A%3ADisplay%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20formatter%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20assert!(formatter.sign_aware_zero_pad())%3B%0A%20%20%20%20%20%20%20%20assert_eq!(formatter.width()%2C%20Some(4))%3B%0A%20%20%20%20%20%20%20%20%2F%2F%20We%20ignore%20the%20formatter's%20options.%0A%20%20%20%20%20%20%20%20write!(formatter%2C%20%22%7B%7D%22%2C%20self.0)%0A%20%20%20%20%7D%0A%7D%0A%0Aassert_eq!(%26format!(%22%7B%3A04%7D%22%2C%20Foo(23))%2C%20%2223%22)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.debug_struct' class="method"><span id='debug_struct.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.debug_struct' class='fnname'>debug_struct</a>&lt;'b&gt;(&amp;'b mut self, name: &amp;str) -&gt; <a class="struct" href="../../core/fmt/struct.DebugStruct.html" title="struct core::fmt::DebugStruct">DebugStruct</a>&lt;'b, 'a&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.2.0'>1.2.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1677-1679' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Creates a <a href="../../std/fmt/struct.DebugStruct.html"><code>DebugStruct</code></a> builder designed to assist with creation of
<a href="../../std/fmt/trait.Debug.html"><code>fmt::Debug</code></a> implementations for structs.</p>
<h1 id="examples-9" class="section-header"><a href="#examples-9">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">net</span>::<span class="ident">Ipv4Addr</span>;

<span class="kw">struct</span> <span class="ident">Foo</span> {
    <span class="ident">bar</span>: <span class="ident">i32</span>,
    <span class="ident">baz</span>: <span class="ident">String</span>,
    <span class="ident">addr</span>: <span class="ident">Ipv4Addr</span>,
}

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Foo</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">fmt</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="ident">fmt</span>.<span class="ident">debug_struct</span>(<span class="string">&quot;Foo&quot;</span>)
            .<span class="ident">field</span>(<span class="string">&quot;bar&quot;</span>, <span class="kw-2">&amp;</span><span class="self">self</span>.<span class="ident">bar</span>)
            .<span class="ident">field</span>(<span class="string">&quot;baz&quot;</span>, <span class="kw-2">&amp;</span><span class="self">self</span>.<span class="ident">baz</span>)
            .<span class="ident">field</span>(<span class="string">&quot;addr&quot;</span>, <span class="kw-2">&amp;</span><span class="macro">format_args</span><span class="macro">!</span>(<span class="string">&quot;{}&quot;</span>, <span class="self">self</span>.<span class="ident">addr</span>))
            .<span class="ident">finish</span>()
    }
}

<span class="macro">assert_eq</span><span class="macro">!</span>(
    <span class="string">&quot;Foo { bar: 10, baz: \&quot;Hello World\&quot;, addr: 127.0.0.1 }&quot;</span>,
    <span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:?}&quot;</span>, <span class="ident">Foo</span> {
        <span class="ident">bar</span>: <span class="number">10</span>,
        <span class="ident">baz</span>: <span class="string">&quot;Hello World&quot;</span>.<span class="ident">to_string</span>(),
        <span class="ident">addr</span>: <span class="ident">Ipv4Addr</span>::<span class="ident">new</span>(<span class="number">127</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">1</span>),
    })
);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0Ause%20std%3A%3Anet%3A%3AIpv4Addr%3B%0A%0Astruct%20Foo%20%7B%0A%20%20%20%20bar%3A%20i32%2C%0A%20%20%20%20baz%3A%20String%2C%0A%20%20%20%20addr%3A%20Ipv4Addr%2C%0A%7D%0A%0Aimpl%20fmt%3A%3ADebug%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20fmt%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20fmt.debug_struct(%22Foo%22)%0A%20%20%20%20%20%20%20%20%20%20%20%20.field(%22bar%22%2C%20%26self.bar)%0A%20%20%20%20%20%20%20%20%20%20%20%20.field(%22baz%22%2C%20%26self.baz)%0A%20%20%20%20%20%20%20%20%20%20%20%20.field(%22addr%22%2C%20%26format_args!(%22%7B%7D%22%2C%20self.addr))%0A%20%20%20%20%20%20%20%20%20%20%20%20.finish()%0A%20%20%20%20%7D%0A%7D%0A%0Aassert_eq!(%0A%20%20%20%20%22Foo%20%7B%20bar%3A%2010%2C%20baz%3A%20%5C%22Hello%20World%5C%22%2C%20addr%3A%20127.0.0.1%20%7D%22%2C%0A%20%20%20%20format!(%22%7B%3A%3F%7D%22%2C%20Foo%20%7B%0A%20%20%20%20%20%20%20%20bar%3A%2010%2C%0A%20%20%20%20%20%20%20%20baz%3A%20%22Hello%20World%22.to_string()%2C%0A%20%20%20%20%20%20%20%20addr%3A%20Ipv4Addr%3A%3Anew(127%2C%200%2C%200%2C%201)%2C%0A%20%20%20%20%7D)%0A)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.debug_tuple' class="method"><span id='debug_tuple.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.debug_tuple' class='fnname'>debug_tuple</a>&lt;'b&gt;(&amp;'b mut self, name: &amp;str) -&gt; <a class="struct" href="../../core/fmt/struct.DebugTuple.html" title="struct core::fmt::DebugTuple">DebugTuple</a>&lt;'b, 'a&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.2.0'>1.2.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1708-1710' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Creates a <code>DebugTuple</code> builder designed to assist with creation of
<code>fmt::Debug</code> implementations for tuple structs.</p>
<h1 id="examples-10" class="section-header"><a href="#examples-10">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">marker</span>::<span class="ident">PhantomData</span>;

<span class="kw">struct</span> <span class="ident">Foo</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span>(<span class="ident">i32</span>, <span class="ident">String</span>, <span class="ident">PhantomData</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span>);

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Foo</span><span class="op">&lt;</span><span class="ident">T</span><span class="op">&gt;</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">fmt</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="ident">fmt</span>.<span class="ident">debug_tuple</span>(<span class="string">&quot;Foo&quot;</span>)
            .<span class="ident">field</span>(<span class="kw-2">&amp;</span><span class="self">self</span>.<span class="number">0</span>)
            .<span class="ident">field</span>(<span class="kw-2">&amp;</span><span class="self">self</span>.<span class="number">1</span>)
            .<span class="ident">field</span>(<span class="kw-2">&amp;</span><span class="macro">format_args</span><span class="macro">!</span>(<span class="string">&quot;_&quot;</span>))
            .<span class="ident">finish</span>()
    }
}

<span class="macro">assert_eq</span><span class="macro">!</span>(
    <span class="string">&quot;Foo(10, \&quot;Hello\&quot;, _)&quot;</span>,
    <span class="macro">format</span><span class="macro">!</span>(<span class="string">&quot;{:?}&quot;</span>, <span class="ident">Foo</span>(<span class="number">10</span>, <span class="string">&quot;Hello&quot;</span>.<span class="ident">to_string</span>(), <span class="ident">PhantomData</span>::<span class="op">&lt;</span><span class="ident">u8</span><span class="op">&gt;</span>))
);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0Ause%20std%3A%3Amarker%3A%3APhantomData%3B%0A%0Astruct%20Foo%3CT%3E(i32%2C%20String%2C%20PhantomData%3CT%3E)%3B%0A%0Aimpl%3CT%3E%20fmt%3A%3ADebug%20for%20Foo%3CT%3E%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20fmt%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20fmt.debug_tuple(%22Foo%22)%0A%20%20%20%20%20%20%20%20%20%20%20%20.field(%26self.0)%0A%20%20%20%20%20%20%20%20%20%20%20%20.field(%26self.1)%0A%20%20%20%20%20%20%20%20%20%20%20%20.field(%26format_args!(%22_%22))%0A%20%20%20%20%20%20%20%20%20%20%20%20.finish()%0A%20%20%20%20%7D%0A%7D%0A%0Aassert_eq!(%0A%20%20%20%20%22Foo(10%2C%20%5C%22Hello%5C%22%2C%20_)%22%2C%0A%20%20%20%20format!(%22%7B%3A%3F%7D%22%2C%20Foo(10%2C%20%22Hello%22.to_string()%2C%20PhantomData%3A%3A%3Cu8%3E))%0A)%3B%0A%7D">Run</a></pre>
</div><h4 id='method.debug_list' class="method"><span id='debug_list.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.debug_list' class='fnname'>debug_list</a>&lt;'b&gt;(&amp;'b mut self) -&gt; <a class="struct" href="../../core/fmt/struct.DebugList.html" title="struct core::fmt::DebugList">DebugList</a>&lt;'b, 'a&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.2.0'>1.2.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1732-1734' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Creates a <code>DebugList</code> builder designed to assist with creation of
<code>fmt::Debug</code> implementations for list-like structures.</p>
<h1 id="examples-11" class="section-header"><a href="#examples-11">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;

<span class="kw">struct</span> <span class="ident">Foo</span>(<span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">i32</span><span class="op">&gt;</span>);

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Foo</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">fmt</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="ident">fmt</span>.<span class="ident">debug_list</span>().<span class="ident">entries</span>(<span class="self">self</span>.<span class="number">0</span>.<span class="ident">iter</span>()).<span class="ident">finish</span>()
    }
}

<span class="comment">// prints &quot;[10, 11]&quot;</span>
<span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;{:?}&quot;</span>, <span class="ident">Foo</span>(<span class="macro">vec</span><span class="macro">!</span>[<span class="number">10</span>, <span class="number">11</span>]));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0A%0Astruct%20Foo(Vec%3Ci32%3E)%3B%0A%0Aimpl%20fmt%3A%3ADebug%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20fmt%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20fmt.debug_list().entries(self.0.iter()).finish()%0A%20%20%20%20%7D%0A%7D%0A%0A%2F%2F%20prints%20%22%5B10%2C%2011%5D%22%0Aprintln!(%22%7B%3A%3F%7D%22%2C%20Foo(vec!%5B10%2C%2011%5D))%3B%0A%7D">Run</a></pre>
</div><h4 id='method.debug_set' class="method"><span id='debug_set.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.debug_set' class='fnname'>debug_set</a>&lt;'b&gt;(&amp;'b mut self) -&gt; <a class="struct" href="../../core/fmt/struct.DebugSet.html" title="struct core::fmt::DebugSet">DebugSet</a>&lt;'b, 'a&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.2.0'>1.2.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1791-1793' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Creates a <code>DebugSet</code> builder designed to assist with creation of
<code>fmt::Debug</code> implementations for set-like structures.</p>
<h1 id="examples-12" class="section-header"><a href="#examples-12">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;

<span class="kw">struct</span> <span class="ident">Foo</span>(<span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">i32</span><span class="op">&gt;</span>);

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Foo</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">fmt</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="ident">fmt</span>.<span class="ident">debug_set</span>().<span class="ident">entries</span>(<span class="self">self</span>.<span class="number">0</span>.<span class="ident">iter</span>()).<span class="ident">finish</span>()
    }
}

<span class="comment">// prints &quot;{10, 11}&quot;</span>
<span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;{:?}&quot;</span>, <span class="ident">Foo</span>(<span class="macro">vec</span><span class="macro">!</span>[<span class="number">10</span>, <span class="number">11</span>]));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0A%0Astruct%20Foo(Vec%3Ci32%3E)%3B%0A%0Aimpl%20fmt%3A%3ADebug%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20fmt%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20fmt.debug_set().entries(self.0.iter()).finish()%0A%20%20%20%20%7D%0A%7D%0A%0A%2F%2F%20prints%20%22%7B10%2C%2011%7D%22%0Aprintln!(%22%7B%3A%3F%7D%22%2C%20Foo(vec!%5B10%2C%2011%5D))%3B%0A%7D">Run</a></pre>
<p>In this more complex example, we use <a href="../../std/macro.format_args.html"><code>format_args!</code></a> and <code>.debug_set()</code>
to build a list of match arms:</p>

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

<span class="kw">struct</span> <span class="ident">Arm</span><span class="op">&lt;</span><span class="lifetime">&#39;a</span>, <span class="ident">L</span>: <span class="lifetime">&#39;a</span>, <span class="ident">R</span>: <span class="lifetime">&#39;a</span><span class="op">&gt;</span>(<span class="kw-2">&amp;</span><span class="lifetime">&#39;a</span> (<span class="ident">L</span>, <span class="ident">R</span>));
<span class="kw">struct</span> <span class="ident">Table</span><span class="op">&lt;</span><span class="lifetime">&#39;a</span>, <span class="ident">K</span>: <span class="lifetime">&#39;a</span>, <span class="ident">V</span>: <span class="lifetime">&#39;a</span><span class="op">&gt;</span>(<span class="kw-2">&amp;</span><span class="lifetime">&#39;a</span> [(<span class="ident">K</span>, <span class="ident">V</span>)], <span class="ident">V</span>);

<span class="kw">impl</span><span class="op">&lt;</span><span class="lifetime">&#39;a</span>, <span class="ident">L</span>, <span class="ident">R</span><span class="op">&gt;</span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Arm</span><span class="op">&lt;</span><span class="lifetime">&#39;a</span>, <span class="ident">L</span>, <span class="ident">R</span><span class="op">&gt;</span>
<span class="kw">where</span>
    <span class="ident">L</span>: <span class="lifetime">&#39;a</span> <span class="op">+</span> <span class="ident">fmt</span>::<span class="ident">Debug</span>, <span class="ident">R</span>: <span class="lifetime">&#39;a</span> <span class="op">+</span> <span class="ident">fmt</span>::<span class="ident">Debug</span>
{
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">fmt</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="ident">L</span>::<span class="ident">fmt</span>(<span class="kw-2">&amp;</span>(<span class="self">self</span>.<span class="number">0</span>).<span class="number">0</span>, <span class="ident">fmt</span>)<span class="question-mark">?</span>;
        <span class="ident">fmt</span>.<span class="ident">write_str</span>(<span class="string">&quot; =&gt; &quot;</span>)<span class="question-mark">?</span>;
        <span class="ident">R</span>::<span class="ident">fmt</span>(<span class="kw-2">&amp;</span>(<span class="self">self</span>.<span class="number">0</span>).<span class="number">1</span>, <span class="ident">fmt</span>)
    }
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="lifetime">&#39;a</span>, <span class="ident">K</span>, <span class="ident">V</span><span class="op">&gt;</span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Table</span><span class="op">&lt;</span><span class="lifetime">&#39;a</span>, <span class="ident">K</span>, <span class="ident">V</span><span class="op">&gt;</span>
<span class="kw">where</span>
    <span class="ident">K</span>: <span class="lifetime">&#39;a</span> <span class="op">+</span> <span class="ident">fmt</span>::<span class="ident">Debug</span>, <span class="ident">V</span>: <span class="lifetime">&#39;a</span> <span class="op">+</span> <span class="ident">fmt</span>::<span class="ident">Debug</span>
{
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">fmt</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="ident">fmt</span>.<span class="ident">debug_set</span>()
        .<span class="ident">entries</span>(<span class="self">self</span>.<span class="number">0</span>.<span class="ident">iter</span>().<span class="ident">map</span>(<span class="ident">Arm</span>))
        .<span class="ident">entry</span>(<span class="kw-2">&amp;</span><span class="ident">Arm</span>(<span class="kw-2">&amp;</span>(<span class="macro">format_args</span><span class="macro">!</span>(<span class="string">&quot;_&quot;</span>), <span class="kw-2">&amp;</span><span class="self">self</span>.<span class="number">1</span>)))
        .<span class="ident">finish</span>()
    }
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0A%0Astruct%20Arm%3C'a%2C%20L%3A%20'a%2C%20R%3A%20'a%3E(%26'a%20(L%2C%20R))%3B%0Astruct%20Table%3C'a%2C%20K%3A%20'a%2C%20V%3A%20'a%3E(%26'a%20%5B(K%2C%20V)%5D%2C%20V)%3B%0A%0Aimpl%3C'a%2C%20L%2C%20R%3E%20fmt%3A%3ADebug%20for%20Arm%3C'a%2C%20L%2C%20R%3E%0Awhere%0A%20%20%20%20L%3A%20'a%20%2B%20fmt%3A%3ADebug%2C%20R%3A%20'a%20%2B%20fmt%3A%3ADebug%0A%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20fmt%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20L%3A%3Afmt(%26(self.0).0%2C%20fmt)%3F%3B%0A%20%20%20%20%20%20%20%20fmt.write_str(%22%20%3D%3E%20%22)%3F%3B%0A%20%20%20%20%20%20%20%20R%3A%3Afmt(%26(self.0).1%2C%20fmt)%0A%20%20%20%20%7D%0A%7D%0A%0Aimpl%3C'a%2C%20K%2C%20V%3E%20fmt%3A%3ADebug%20for%20Table%3C'a%2C%20K%2C%20V%3E%0Awhere%0A%20%20%20%20K%3A%20'a%20%2B%20fmt%3A%3ADebug%2C%20V%3A%20'a%20%2B%20fmt%3A%3ADebug%0A%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20fmt%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20fmt.debug_set()%0A%20%20%20%20%20%20%20%20.entries(self.0.iter().map(Arm))%0A%20%20%20%20%20%20%20%20.entry(%26Arm(%26(format_args!(%22_%22)%2C%20%26self.1)))%0A%20%20%20%20%20%20%20%20.finish()%0A%20%20%20%20%7D%0A%7D%0A%7D">Run</a></pre>
</div><h4 id='method.debug_map' class="method"><span id='debug_map.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.debug_map' class='fnname'>debug_map</a>&lt;'b&gt;(&amp;'b mut self) -&gt; <a class="struct" href="../../core/fmt/struct.DebugMap.html" title="struct core::fmt::DebugMap">DebugMap</a>&lt;'b, 'a&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.2.0'>1.2.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1815-1817' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Creates a <code>DebugMap</code> builder designed to assist with creation of
<code>fmt::Debug</code> implementations for map-like structures.</p>
<h1 id="examples-13" class="section-header"><a href="#examples-13">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</span>;

<span class="kw">struct</span> <span class="ident">Foo</span>(<span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">String</span>, <span class="ident">i32</span>)<span class="op">&gt;</span>);

<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Foo</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">fmt</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-&gt;</span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
        <span class="ident">fmt</span>.<span class="ident">debug_map</span>().<span class="ident">entries</span>(<span class="self">self</span>.<span class="number">0</span>.<span class="ident">iter</span>().<span class="ident">map</span>(<span class="op">|</span><span class="kw-2">&amp;</span>(<span class="kw-2">ref</span> <span class="ident">k</span>, <span class="kw-2">ref</span> <span class="ident">v</span>)<span class="op">|</span> (<span class="ident">k</span>, <span class="ident">v</span>))).<span class="ident">finish</span>()
    }
}

<span class="comment">// prints &quot;{&quot;A&quot;: 10, &quot;B&quot;: 11}&quot;</span>
<span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;{:?}&quot;</span>, <span class="ident">Foo</span>(<span class="macro">vec</span><span class="macro">!</span>[(<span class="string">&quot;A&quot;</span>.<span class="ident">to_string</span>(), <span class="number">10</span>), (<span class="string">&quot;B&quot;</span>.<span class="ident">to_string</span>(), <span class="number">11</span>)]));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Afmt%3B%0A%0Astruct%20Foo(Vec%3C(String%2C%20i32)%3E)%3B%0A%0Aimpl%20fmt%3A%3ADebug%20for%20Foo%20%7B%0A%20%20%20%20fn%20fmt(%26self%2C%20fmt%3A%20%26mut%20fmt%3A%3AFormatter)%20-%3E%20fmt%3A%3AResult%20%7B%0A%20%20%20%20%20%20%20%20fmt.debug_map().entries(self.0.iter().map(%7C%26(ref%20k%2C%20ref%20v)%7C%20(k%2C%20v))).finish()%0A%20%20%20%20%7D%0A%7D%0A%0A%2F%2F%20prints%20%22%7B%22A%22%3A%2010%2C%20%22B%22%3A%2011%7D%22%0Aprintln!(%22%7B%3A%3F%7D%22%2C%20Foo(vec!%5B(%22A%22.to_string()%2C%2010)%2C%20(%22B%22.to_string()%2C%2011)%5D))%3B%0A%7D">Run</a></pre>
</div></div>
                <h2 id='implementations' class='small-section-header'>
                  Trait Implementations<a href='#implementations' class='anchor'></a>
                </h2>
                <div id='implementations-list'><h3 id='impl-Write' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;'a&gt; <a class="trait" href="../../core/fmt/trait.Write.html" title="trait core::fmt::Write">Write</a> for <a class="struct" href="../../core/fmt/struct.Formatter.html" title="struct core::fmt::Formatter">Formatter</a>&lt;'a&gt;</code><a href='#impl-Write' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><div class='since' title='Stable since Rust version 1.2.0'>1.2.0</div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1821-1833' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.write_str-1' class="method"><span id='write_str.v-1' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../core/fmt/trait.Write.html#tymethod.write_str' class='fnname'>write_str</a>(&amp;mut self, s: &amp;str) -&gt; <a class="type" href="../../core/fmt/type.Result.html" title="type core::fmt::Result">Result</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1822-1824' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Writes a slice of bytes into this writer, returning whether the write succeeded. <a href="../../core/fmt/trait.Write.html#tymethod.write_str">Read more</a></p>
</div><h4 id='method.write_char' class="method"><span id='write_char.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../core/fmt/trait.Write.html#method.write_char' class='fnname'>write_char</a>(&amp;mut self, c: char) -&gt; <a class="type" href="../../core/fmt/type.Result.html" title="type core::fmt::Result">Result</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1826-1828' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Writes a [<code>char</code>] into this writer, returning whether the write succeeded. <a href="../../core/fmt/trait.Write.html#method.write_char">Read more</a></p>
</div><h4 id='method.write_fmt-1' class="method"><span id='write_fmt.v-1' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../core/fmt/trait.Write.html#method.write_fmt' class='fnname'>write_fmt</a>(&amp;mut self, args: <a class="struct" href="../../core/fmt/struct.Arguments.html" title="struct core::fmt::Arguments">Arguments</a>) -&gt; <a class="type" href="../../core/fmt/type.Result.html" title="type core::fmt::Result">Result</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/fmt/mod.rs.html#1830-1832' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Glue for usage of the [<code>write!</code>] macro with implementors of this trait. <a href="../../core/fmt/trait.Write.html#method.write_fmt">Read more</a></p>
</div></div></div>
                <h2 id='synthetic-implementations' class='small-section-header'>
                  Auto Trait Implementations<a href='#synthetic-implementations' class='anchor'></a>
                </h2>
                <div id='synthetic-implementations-list'>
            <h3 id='impl-Send' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;'a&gt; !<a class="trait" href="../../core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> for <a class="struct" href="../../core/fmt/struct.Formatter.html" title="struct core::fmt::Formatter">Formatter</a>&lt;'a&gt;</code><a href='#impl-Send' class='anchor'></a></span></td><td><span class='out-of-band'></span></td></tr></tbody></table></h3><div class='impl-items'></div><h3 id='impl-Sync' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl&lt;'a&gt; !<a class="trait" href="../../core/marker/trait.Sync.html" title="trait core::marker::Sync">Sync</a> for <a class="struct" href="../../core/fmt/struct.Formatter.html" title="struct core::fmt::Formatter">Formatter</a>&lt;'a&gt;</code><a href='#impl-Sync' class='anchor'></a></span></td><td><span class='out-of-band'></span></td></tr></tbody></table></h3><div class='impl-items'></div></div></section><section id="search" class="content hidden"></section><section class="footer"></section><aside id="help" class="hidden"><div><h1 class="hidden">Help</h1><div class="shortcuts"><h2>Keyboard Shortcuts</h2><dl><dt><kbd>?</kbd></dt><dd>Show this help dialog</dd><dt><kbd>S</kbd></dt><dd>Focus the search field</dd><dt><kbd>↑</kbd></dt><dd>Move up in search results</dd><dt><kbd>↓</kbd></dt><dd>Move down in search results</dd><dt><kbd>↹</kbd></dt><dd>Switch tab</dd><dt><kbd>&#9166;</kbd></dt><dd>Go to active search result</dd><dt><kbd>+</kbd></dt><dd>Expand all sections</dd><dt><kbd>-</kbd></dt><dd>Collapse all sections</dd></dl></div><div class="infos"><h2>Search Tricks</h2><p>Prefix searches with a type followed by a colon (e.g. <code>fn:</code>) to restrict the search to a given type.</p><p>Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>.</p><p>Search functions by type signature (e.g. <code>vec -> usize</code> or <code>* -> vec</code>)</p><p>Search multiple things at once by splitting your query with comma (e.g. <code>str,u8</code> or <code>String,struct:Vec,test</code>)</p></div></div></aside><script>window.rootPath = "../../";window.currentCrate = "core";</script><script src="../../aliases.js"></script><script src="../../main.js"></script><script defer src="../../search-index.js"></script></body></html>