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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="github crates-io docs-rs"><meta name="keywords" content="rust, rustlang, rust-lang, ryu"><title>ryu - 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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</a><h2 class="location">Crate ryu</h2><div class="block version"><div class="narrow-helper"></div><p>Version 1.0.9</p></div><div class="sidebar-elems"><a id="all-types" href="all.html"><p>See all ryu's items</p></a><div class="block items"><ul><li><a href="#modules">Modules</a></li><li><a href="#structs">Structs</a></li><li><a href="#traits">Traits</a></li></ul></div><div id="sidebar-vars" data-name="ryu" data-ty="mod" 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="../ryu/index.html"><img class="rust-logo" src="../rust-logo.png" alt="logo"></a><nav class="sub"><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu" title="themes"><img width="18" height="18" alt="Pick another theme!" src="../brush.svg"></button><div id="theme-choices" role="menu"></div></div><form class="search-form"><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><button type="button" id="help-button" title="help">?</button><a id="settings-menu" href="../settings.html" title="settings"><img width="18" height="18" alt="Change settings" src="../wheel.svg"></a></div></form></nav></div><section id="main-content" class="content"><h1 class="fqn"><span class="in-band">Crate <a class="mod" href="#">ryu</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><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">−</span>]</a></span><a class="srclink" href="../src/ryu/lib.rs.html#1-123" title="goto source code">[src]</a></span></h1><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p><a href="https://github.com/dtolnay/ryu"><img src="https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github" alt="github" /></a> <a href="https://crates.io/crates/ryu"><img src="https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust" alt="crates-io" /></a> <a href="https://docs.rs/ryu"><img src="https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logoColor=white&logo=data:image/svg+xml;base64,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" alt="docs-rs" /></a></p>
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<br>
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<p>Pure Rust implementation of Ryū, an algorithm to quickly convert floating
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point numbers to decimal strings.</p>
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<p>The PLDI’18 paper <a href="https://dl.acm.org/citation.cfm?id=3192369"><em>Ryū: fast float-to-string conversion</em></a> by Ulf
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Adams includes a complete correctness proof of the algorithm. The paper is
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available under the creative commons CC-BY-SA license.</p>
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<p>This Rust implementation is a line-by-line port of Ulf Adams’ implementation
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in C, <a href="https://github.com/ulfjack/ryu">https://github.com/ulfjack/ryu</a>.</p>
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<h2 id="example" class="section-header"><a href="#example">Example</a></h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><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">buffer</span> <span class="op">=</span> <span class="ident">ryu::Buffer::new</span>();
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<span class="kw">let</span> <span class="ident">printed</span> <span class="op">=</span> <span class="ident">buffer</span>.<span class="ident">format</span>(<span class="number">1.234</span>);
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<span class="macro">assert_eq!</span>(<span class="ident">printed</span>, <span class="string">"1.234"</span>);
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}</code></pre></div>
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<h3 id="performance-lower-is-better" class="section-header"><a href="#performance-lower-is-better">Performance (lower is better)</a></h3>
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<p><img src="https://raw.githubusercontent.com/dtolnay/ryu/master/performance.png" alt="performance" /></p>
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<p>You can run upstream’s benchmarks with:</p>
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<div class="example-wrap"><pre class="language-console"><code>$ git clone https://github.com/ulfjack/ryu c-ryu
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$ cd c-ryu
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$ bazel run -c opt //ryu/benchmark</code></pre></div>
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<p>And the same benchmark against our implementation with:</p>
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<div class="example-wrap"><pre class="language-console"><code>$ git clone https://github.com/dtolnay/ryu rust-ryu
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$ cd rust-ryu
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$ cargo run --example upstream_benchmark --release</code></pre></div>
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<p>These benchmarks measure the average time to print a 32-bit float and average
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time to print a 64-bit float, where the inputs are distributed as uniform random
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bit patterns 32 and 64 bits wide.</p>
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<p>The upstream C code, the unsafe direct Rust port, and the safe pretty Rust API
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all perform the same, taking around 21 nanoseconds to format a 32-bit float and
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31 nanoseconds to format a 64-bit float.</p>
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<p>There is also a Rust-specific benchmark comparing this implementation to the
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standard library which you can run with:</p>
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<div class="example-wrap"><pre class="language-console"><code>$ cargo bench</code></pre></div>
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<p>The benchmark shows Ryū approximately 2-5x faster than the standard library
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across a range of f32 and f64 inputs. Measurements are in nanoseconds per
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iteration; smaller is better.</p>
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<h3 id="formatting" class="section-header"><a href="#formatting">Formatting</a></h3>
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<p>This library tends to produce more human-readable output than the standard
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library’s to_string, which never uses scientific notation. Here are two
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examples:</p>
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<ul>
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<li><em>ryu:</em> 1.23e40, <em>std:</em> 12300000000000000000000000000000000000000</li>
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<li><em>ryu:</em> 1.23e-40, <em>std:</em> 0.000000000000000000000000000000000000000123</li>
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</ul>
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<p>Both libraries print short decimals such as 0.0000123 without scientific
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notation.</p>
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</div></details><h2 id="modules" class="small-section-header"><a href="#modules">Modules</a></h2>
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<div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="mod" href="raw/index.html" title="ryu::raw mod">raw</a></div><div class="item-right docblock-short"><p>Unsafe functions that mirror the API of the C implementation of Ryū.</p>
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</div></div></div><h2 id="structs" class="small-section-header"><a href="#structs">Structs</a></h2>
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<div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="struct" href="struct.Buffer.html" title="ryu::Buffer struct">Buffer</a></div><div class="item-right docblock-short"><p>Safe API for formatting floating point numbers to text.</p>
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</div></div></div><h2 id="traits" class="small-section-header"><a href="#traits">Traits</a></h2>
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<div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="trait" href="trait.Float.html" title="ryu::Float trait">Float</a></div><div class="item-right docblock-short"><p>A floating point number, f32 or f64, that can be written into a
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<a href="struct.Buffer.html" title="Buffer"><code>ryu::Buffer</code></a>.</p>
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</div></div></div></section><section id="search" class="content hidden"></section></div></main><div id="rustdoc-vars" data-root-path="../" data-current-crate="ryu" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.59.0 (9d1b2106e 2022-02-23)" ></div>
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