mentat/either/macro.try_left.html
2018-08-22 17:04:13 +00:00

150 lines
No EOL
6.9 KiB
HTML
Raw Permalink Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

<!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 `try_left` macro in crate `either`.">
<meta name="keywords" content="rust, rustlang, rust-lang, try_left">
<title>either::try_left - 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="../main.css" id="themeStyle">
<script src="../storage.js"></script>
</head>
<body class="rustdoc macro">
<!--[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'><a href='index.html'>either</a></p><script>window.sidebarCurrent = {name: 'try_left', ty: 'macro', relpath: ''};</script><script defer src="sidebar-items.js"></script>
</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">
</div>
</form>
</nav>
<section id='main' class="content">
<h1 class='fqn'><span class='in-band'>Macro <a href='index.html'>either</a>::<wbr><a class="macro" href=''>try_left</a></span><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><a class='srclink' href='../src/either/lib.rs.html#84-91' title='goto source code'>[src]</a></span></h1>
<pre class="rust macro">
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">try_left</span> {
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">expr</span>:<span class="ident">expr</span>) <span class="op">=&gt;</span> { ... };
}</pre>
<div class='docblock'><p>Macro for unwrapping the left side of an <code>Either</code>, which fails early
with the opposite side. Can only be used in functions that return
<code>Either</code> because of the early return of <code>Right</code> that it provides.</p>
<p>See also <code>try_right!</code> for its dual, which applies the same just to the
right side.</p>
<h1 id="example" class="section-header"><a href="#example">Example</a></h1>
<pre class="rust rust-example-rendered">
<span class="attribute">#[<span class="ident">macro_use</span>]</span> <span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">either</span>;
<span class="kw">use</span> <span class="ident">either</span>::{<span class="ident">Either</span>, <span class="ident">Left</span>, <span class="ident">Right</span>};
<span class="kw">fn</span> <span class="ident">twice</span>(<span class="ident">wrapper</span>: <span class="ident">Either</span><span class="op">&lt;</span><span class="ident">u32</span>, <span class="kw-2">&amp;</span><span class="ident">str</span><span class="op">&gt;</span>) <span class="op">-&gt;</span> <span class="ident">Either</span><span class="op">&lt;</span><span class="ident">u32</span>, <span class="kw-2">&amp;</span><span class="ident">str</span><span class="op">&gt;</span> {
<span class="kw">let</span> <span class="ident">value</span> <span class="op">=</span> <span class="macro">try_left</span><span class="macro">!</span>(<span class="ident">wrapper</span>);
<span class="ident">Left</span>(<span class="ident">value</span> <span class="op">*</span> <span class="number">2</span>)
}
<span class="kw">fn</span> <span class="ident">main</span>() {
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">twice</span>(<span class="ident">Left</span>(<span class="number">2</span>)), <span class="ident">Left</span>(<span class="number">4</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">twice</span>(<span class="ident">Right</span>(<span class="string">&quot;ups&quot;</span>)), <span class="ident">Right</span>(<span class="string">&quot;ups&quot;</span>));
}</pre>
</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>
</div>
</div>
</aside>
<script>
window.rootPath = "../";
window.currentCrate = "either";
</script>
<script src="../main.js"></script>
<script defer src="../search-index.js"></script>
</body>
</html>