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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="Determines if a message logged at the specified level in that module will be logged."><meta name="keywords" content="rust, rustlang, rust-lang, log_enabled"><title>log_enabled in log - 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="icon" href="https://www.rust-lang.org/favicon.ico"></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="../log/index.html"><div class="logo-container"><img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png" 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="../log/index.html"><div class="logo-container">
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<img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png" alt="logo"></div>
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</a><div class="sidebar-elems"><h2 class="location"><a href="index.html">In log</a></h2><div id="sidebar-vars" data-name="log_enabled" 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="../log/index.html">
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<h1 class="fqn"><span class="in-band">Macro <a href="index.html">log</a>::<wbr><a class="macro" href="#">log_enabled</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/log/macros.rs.html#215-225">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">log_enabled</span> {
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(<span class="ident">target</span>: <span class="macro-nonterminal">$</span><span class="macro-nonterminal">target</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">lvl</span>:<span class="ident">expr</span>) => { ... };
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(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">lvl</span>:<span class="ident">expr</span>) => { ... };
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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>Determines if a message logged at the specified level in that module will
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be logged.</p>
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<p>This can be used to avoid expensive computation of log message arguments if
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the message would be ignored anyway.</p>
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<h2 id="examples"><a href="#examples">Examples</a></h2>
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<div class='information'><div class='tooltip edition' data-edition="2018">ⓘ</div></div><div class="example-wrap"><pre class="rust rust-example-rendered edition"><code><span class="kw">use</span> <span class="ident">log::Level::Debug</span>;
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<span class="kw">use</span> <span class="ident">log</span>::{<span class="ident">debug</span>, <span class="ident">log_enabled</span>};
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<span class="kw">if</span> <span class="macro">log_enabled!</span>(<span class="ident">Debug</span>) {
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<span class="kw">let</span> <span class="ident">data</span> <span class="op">=</span> <span class="ident">expensive_call</span>();
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<span class="macro">debug!</span>(<span class="string">"expensive debug data: {} {}"</span>, <span class="ident">data</span>.<span class="ident">x</span>, <span class="ident">data</span>.<span class="ident">y</span>);
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}
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<span class="kw">if</span> <span class="macro">log_enabled!</span>(<span class="ident">target</span>: <span class="string">"Global"</span>, <span class="ident">Debug</span>) {
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<span class="kw">let</span> <span class="ident">data</span> <span class="op">=</span> <span class="ident">expensive_call</span>();
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<span class="macro">debug!</span>(<span class="ident">target</span>: <span class="string">"Global"</span>, <span class="string">"expensive debug data: {} {}"</span>, <span class="ident">data</span>.<span class="ident">x</span>, <span class="ident">data</span>.<span class="ident">y</span>);
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}</code></pre></div>
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</div></details></section><section id="search" class="content hidden"></section></div></main><div id="rustdoc-vars" data-root-path="../" data-current-crate="log" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.62.0-nightly (1f7fb6413 2022-04-10)" ></div>
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