Sophie: rust-doc-1.35.0-1.mga7 armv7hl

rust-doc-1.35.0-1.mga7.armv7hl.rpm

<!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 `if` keyword in crate `std`."><meta name="keywords" content="rust, rustlang, rust-lang, if"><title>if - Rust</title><link rel="stylesheet" type="text/css" href="../normalize1.35.0.css"><link rel="stylesheet" type="text/css" href="../rustdoc1.35.0.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../dark1.35.0.css"><link rel="stylesheet" type="text/css" href="../light1.35.0.css" id="themeStyle"><script src="../storage1.35.0.js"></script><noscript><link rel="stylesheet" href="../noscript1.35.0.css"></noscript><link rel="shortcut icon" href="../favicon1.35.0.ico"><style type="text/css">#crate-search{background-image:url("../down-arrow1.35.0.svg");}</style></head><body class="rustdoc keyword"><!--[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='../std/index.html'><img src='../rust-logo1.35.0.png' alt='logo' width='100'></a><div class="sidebar-elems"><p class='location'><a href='index.html'>std</a></p><script>window.sidebarCurrent = {name: 'if', ty: 'keyword', 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="../brush1.35.0.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../theme1.35.0.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><a id="settings-menu" href="../settings.html"><img src="../wheel1.35.0.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='out-of-band'><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>&#x2212;</span>]</a></span></span><span class='in-band'>Keyword <a class="keyword" href=''>if</a></span></h1><div class='docblock'><p>If statements and expressions.</p>
<p><code>if</code> is a familiar construct to most programmers, and is the main way you'll often do logic in
your code. However, unlike in most languages, <code>if</code> blocks can also act as expressions.</p>

<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">if</span> <span class="number">1</span> <span class="op">==</span> <span class="number">2</span> {
    <span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;whoops, mathematics broke&quot;</span>);
} <span class="kw">else</span> {
    <span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;everything&#39;s fine!&quot;</span>);
}

<span class="kw">let</span> <span class="ident">greeting</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">rude</span> {
    <span class="string">&quot;sup nerd.&quot;</span>
} <span class="kw">else</span> {
    <span class="string">&quot;hello, friend!&quot;</span>
};

<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Ok</span>(<span class="ident">x</span>) <span class="op">=</span> <span class="string">&quot;123&quot;</span>.<span class="ident">parse</span>::<span class="op">&lt;</span><span class="ident">i32</span><span class="op">&gt;</span>() {
    <span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;{} double that and you get {}!&quot;</span>, <span class="ident">greeting</span>, <span class="ident">x</span> <span class="op">*</span> <span class="number">2</span>);
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20rude%20%3D%20true%3B%0Aif%201%20%3D%3D%202%20%7B%0A%20%20%20%20println!(%22whoops%2C%20mathematics%20broke%22)%3B%0A%7D%20else%20%7B%0A%20%20%20%20println!(%22everything's%20fine!%22)%3B%0A%7D%0A%0Alet%20greeting%20%3D%20if%20rude%20%7B%0A%20%20%20%20%22sup%20nerd.%22%0A%7D%20else%20%7B%0A%20%20%20%20%22hello%2C%20friend!%22%0A%7D%3B%0A%0Aif%20let%20Ok(x)%20%3D%20%22123%22.parse%3A%3A%3Ci32%3E()%20%7B%0A%20%20%20%20println!(%22%7B%7D%20double%20that%20and%20you%20get%20%7B%7D!%22%2C%20greeting%2C%20x%20*%202)%3B%0A%7D%0A%7D">Run</a></pre></div>
<p>Shown above are the three typical forms an <code>if</code> block comes in. First is the usual kind of
thing you'd see in many languages, with an optional <code>else</code> block. Second uses <code>if</code> as an
expression, which is only possible if all branches return the same type. An <code>if</code> expression can
be used everywhere you'd expect. The third kind of <code>if</code> block is an <code>if let</code> block, which
behaves similarly to using a <code>match</code> expression:</p>

<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">x</span>) <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">123</span>) {
    <span class="comment">// code</span>
} <span class="kw">else</span> {
    <span class="comment">// something else</span>
}

<span class="kw">match</span> <span class="prelude-val">Some</span>(<span class="number">123</span>) {
    <span class="prelude-val">Some</span>(<span class="ident">x</span>) <span class="op">=&gt;</span> {
        <span class="comment">// code</span>
    },
    <span class="kw">_</span> <span class="op">=&gt;</span> {
        <span class="comment">// something else</span>
    },
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Aif%20let%20Some(x)%20%3D%20Some(123)%20%7B%0A%20%20%20%20%2F%2F%20code%0Alet%20_%20%3D%20x%3B%0A%7D%20else%20%7B%0A%20%20%20%20%2F%2F%20something%20else%0A%7D%0A%0Amatch%20Some(123)%20%7B%0A%20%20%20%20Some(x)%20%3D%3E%20%7B%0A%20%20%20%20%20%20%20%20%2F%2F%20code%0Alet%20_%20%3D%20x%3B%0A%20%20%20%20%7D%2C%0A%20%20%20%20_%20%3D%3E%20%7B%0A%20%20%20%20%20%20%20%20%2F%2F%20something%20else%0A%20%20%20%20%7D%2C%0A%7D%0A%7D">Run</a></pre></div>
<p>Each kind of <code>if</code> expression can be mixed and matched as needed.</p>

<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">if</span> <span class="bool-val">true</span> <span class="op">==</span> <span class="bool-val">false</span> {
    <span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;oh no&quot;</span>);
} <span class="kw">else</span> <span class="kw">if</span> <span class="string">&quot;something&quot;</span> <span class="op">==</span> <span class="string">&quot;other thing&quot;</span> {
    <span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;oh dear&quot;</span>);
} <span class="kw">else</span> <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="number">200</span>) <span class="op">=</span> <span class="string">&quot;blarg&quot;</span>.<span class="ident">parse</span>::<span class="op">&lt;</span><span class="ident">i32</span><span class="op">&gt;</span>().<span class="ident">ok</span>() {
    <span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;uh oh&quot;</span>);
} <span class="kw">else</span> {
    <span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;phew, nothing&#39;s broken&quot;</span>);
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Aif%20true%20%3D%3D%20false%20%7B%0A%20%20%20%20println!(%22oh%20no%22)%3B%0A%7D%20else%20if%20%22something%22%20%3D%3D%20%22other%20thing%22%20%7B%0A%20%20%20%20println!(%22oh%20dear%22)%3B%0A%7D%20else%20if%20let%20Some(200)%20%3D%20%22blarg%22.parse%3A%3A%3Ci32%3E().ok()%20%7B%0A%20%20%20%20println!(%22uh%20oh%22)%3B%0A%7D%20else%20%7B%0A%20%20%20%20println!(%22phew%2C%20nothing's%20broken%22)%3B%0A%7D%0A%7D">Run</a></pre></div>
<p>The <code>if</code> keyword is used in one other place in Rust, namely as a part of pattern matching
itself, allowing patterns such as <code>Some(x) if x &gt; 200</code> to be used.</p>
<p>For more information on <code>if</code> expressions, see the <a href="https://doc.rust-lang.org/stable/book/2018-edition/ch03-05-control-flow.html#if-expressions">Rust book</a> or the <a href="https://doc.rust-lang.org/reference/expressions/if-expr.html">Reference</a>.</p>
</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 = "std";</script><script src="../aliases.js"></script><script src="../main1.35.0.js"></script><script defer src="../search-index.js"></script></body></html>