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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="The macro used to generate the flag structures."><meta name="keywords" content="rust, rustlang, rust-lang, bitflags"><title>bitflags in bitflags - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../SourceCodePro-Semibold.ttf.woff2"><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="../ayu.css" disabled><link rel="stylesheet" type="text/css" href="../dark.css" disabled><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../storage.js"></script><script src="../crates.js"></script><script defer src="../main.js"></script>
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<noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../favicon.svg"></head><body class="rustdoc macro"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">☰</button><a class="sidebar-logo" href="../bitflags/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div>
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</a><h2 class="location"></h2>
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</nav>
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<nav class="sidebar"><a class="sidebar-logo" href="../bitflags/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div>
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</a><div class="sidebar-elems"><h2 class="location"><a href="index.html">In bitflags</a></h2><div id="sidebar-vars" data-name="bitflags" data-ty="macro" data-relpath=""></div><script defer src="sidebar-items.js"></script></div></nav><main><div class="width-limiter"><div class="sub-container"><a class="sub-logo-container" href="../bitflags/index.html"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></a><nav class="sub"><div class="theme-picker hidden"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu" title="themes"><img width="22" height="22" alt="Pick another theme!" src="../brush.svg"></button><div id="theme-choices" role="menu"></div></div><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><button type="button" id="help-button" title="help">?</button><a id="settings-menu" href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../wheel.svg"></a></div></form></nav></div><section id="main-content" class="content"><div class="main-heading">
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<h1 class="fqn"><span class="in-band">Macro <a href="index.html">bitflags</a>::<wbr><a class="macro" href="#">bitflags</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../clipboard.svg" width="19" height="18" alt="Copy item path"></button></span></h1><span class="out-of-band"><a class="srclink" href="../src/bitflags/lib.rs.html#350-382">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><div class="docblock item-decl"><div class="example-wrap"><pre class="rust macro"><code><span class="macro">macro_rules!</span> <span class="ident">bitflags</span> {
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(
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$(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">outer</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span>
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<span class="macro-nonterminal">$</span><span class="macro-nonterminal">vis</span>:<span class="ident">vis</span> <span class="kw">struct</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">BitFlags</span>:<span class="ident">ident</span>: <span class="macro-nonterminal">$</span><span class="macro-nonterminal">T</span>:<span class="ident">ty</span> {
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$(
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$(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">inner</span>:<span class="ident">ident</span> $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="kw-2">*</span>]</span>)<span class="op">*</span>
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<span class="kw">const</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">Flag</span>:<span class="ident">ident</span> <span class="op">=</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">value</span>:<span class="ident">expr</span>;
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)<span class="op">*</span>
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}
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$(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>:<span class="ident">tt</span>)<span class="op">*</span>
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) => { ... };
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() => { ... };
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}</code></pre></div>
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</div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>The macro used to generate the flag structures.</p>
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<p>See the <a href="../bitflags/index.html">crate level docs</a> for complete documentation.</p>
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<h2 id="example"><a href="#example">Example</a></h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">bitflags::bitflags</span>;
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<span class="macro">bitflags!</span> {
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<span class="kw">struct</span> <span class="ident">Flags</span>: <span class="ident">u32</span> {
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<span class="kw">const</span> <span class="ident">A</span> <span class="op">=</span> <span class="number">0b00000001</span>;
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<span class="kw">const</span> <span class="ident">B</span> <span class="op">=</span> <span class="number">0b00000010</span>;
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<span class="kw">const</span> <span class="ident">C</span> <span class="op">=</span> <span class="number">0b00000100</span>;
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<span class="kw">const</span> <span class="ident">ABC</span> <span class="op">=</span> <span class="ident"><span class="self">Self</span>::A</span>.<span class="ident">bits</span> <span class="op">|</span> <span class="ident"><span class="self">Self</span>::B</span>.<span class="ident">bits</span> <span class="op">|</span> <span class="ident"><span class="self">Self</span>::C</span>.<span class="ident">bits</span>;
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}
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}
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<span class="kw">fn</span> <span class="ident">main</span>() {
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<span class="kw">let</span> <span class="ident">e1</span> <span class="op">=</span> <span class="ident">Flags::A</span> <span class="op">|</span> <span class="ident">Flags::C</span>;
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<span class="kw">let</span> <span class="ident">e2</span> <span class="op">=</span> <span class="ident">Flags::B</span> <span class="op">|</span> <span class="ident">Flags::C</span>;
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<span class="macro">assert_eq!</span>((<span class="ident">e1</span> <span class="op">|</span> <span class="ident">e2</span>), <span class="ident">Flags::ABC</span>); <span class="comment">// union</span>
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<span class="macro">assert_eq!</span>((<span class="ident">e1</span> <span class="op">&</span> <span class="ident">e2</span>), <span class="ident">Flags::C</span>); <span class="comment">// intersection</span>
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<span class="macro">assert_eq!</span>((<span class="ident">e1</span> <span class="op">-</span> <span class="ident">e2</span>), <span class="ident">Flags::A</span>); <span class="comment">// set difference</span>
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<span class="macro">assert_eq!</span>(<span class="op">!</span><span class="ident">e2</span>, <span class="ident">Flags::A</span>); <span class="comment">// set complement</span>
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}</code></pre></div>
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<p>The generated <code>struct</code>s can also be extended with type and trait
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implementations:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use</span> <span class="ident">std::fmt</span>;
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<span class="kw">use</span> <span class="ident">bitflags::bitflags</span>;
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<span class="macro">bitflags!</span> {
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<span class="kw">struct</span> <span class="ident">Flags</span>: <span class="ident">u32</span> {
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<span class="kw">const</span> <span class="ident">A</span> <span class="op">=</span> <span class="number">0b00000001</span>;
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<span class="kw">const</span> <span class="ident">B</span> <span class="op">=</span> <span class="number">0b00000010</span>;
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}
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}
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<span class="kw">impl</span> <span class="ident">Flags</span> {
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<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">clear</span>(<span class="kw-2">&mut</span> <span class="self">self</span>) {
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<span class="self">self</span>.<span class="ident">bits</span> <span class="op">=</span> <span class="number">0</span>; <span class="comment">// The `bits` field can be accessed from within the</span>
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<span class="comment">// same module where the `bitflags!` macro was invoked.</span>
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}
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}
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<span class="kw">impl</span> <span class="ident">fmt::Display</span> <span class="kw">for</span> <span class="ident">Flags</span> {
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<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&mut</span> <span class="ident">fmt::Formatter</span>) -> <span class="ident">fmt::Result</span> {
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<span class="macro">write!</span>(<span class="ident">f</span>, <span class="string">"hi!"</span>)
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}
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}
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<span class="kw">fn</span> <span class="ident">main</span>() {
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">flags</span> <span class="op">=</span> <span class="ident">Flags::A</span> <span class="op">|</span> <span class="ident">Flags::B</span>;
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<span class="ident">flags</span>.<span class="ident">clear</span>();
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<span class="macro">assert!</span>(<span class="ident">flags</span>.<span class="ident">is_empty</span>());
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<span class="macro">assert_eq!</span>(<span class="macro">format!</span>(<span class="string">"{}"</span>, <span class="ident">flags</span>), <span class="string">"hi!"</span>);
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<span class="macro">assert_eq!</span>(<span class="macro">format!</span>(<span class="string">"{:?}"</span>, <span class="ident">Flags::A</span> <span class="op">|</span> <span class="ident">Flags::B</span>), <span class="string">"A | B"</span>);
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<span class="macro">assert_eq!</span>(<span class="macro">format!</span>(<span class="string">"{:?}"</span>, <span class="ident">Flags::B</span>), <span class="string">"B"</span>);
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}</code></pre></div>
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