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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="githubcrates-iodocs-rs"><title>ryu - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><link rel="stylesheet" href="../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../static.files/rustdoc-ac92e1bbe349e143.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="ryu" data-themes="" data-resource-suffix="" data-rustdoc-version="1.76.0 (07dca489a 2024-02-04)" data-channel="1.76.0" data-search-js="search-2b6ce74ff89ae146.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../static.files/storage-f2adc0d6ca4d09fb.js"></script><script defer src="../crates.js"></script><script defer src="../static.files/main-305769736d49e732.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-feafe1bb7466e4bd.css"></noscript><link rel="alternate icon" type="image/png" href="../static.files/favicon-16x16-8b506e7a72182f1c.png"><link rel="alternate icon" type="image/png" href="../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc mod crate"><!--[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">&#9776;</button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../ryu/index.html">ryu</a><span class="version">1.0.15</span></h2></div><div class="sidebar-elems"><ul class="block">
<li><a id="all-types" href="all.html">All Items</a></li></ul><section><ul class="block"><li><a href="#modules">Modules</a></li><li><a href="#structs">Structs</a></li><li><a href="#traits">Traits</a></li></ul></section></div></nav><div class="sidebar-resizer"></div>
<main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><div id="sidebar-button" tabindex="-1"><a href="../ryu/all.html" title="show sidebar"></a></div><input class="search-input" name="search" aria-label="Run search in the documentation" autocomplete="off" spellcheck="false" placeholder="Click or press S to search, ? for more options…" type="search"><div id="help-button" tabindex="-1"><a href="../help.html" title="help">?</a></div><div id="settings-menu" tabindex="-1"><a href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1>Crate <a class="mod" href="#">ryu</a><button id="copy-path" title="Copy item path to clipboard"><img src="../static.files/clipboard-7571035ce49a181d.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="src" href="../src/ryu/lib.rs.html#1-123">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>&#x2212;</span>]</button></span></div><details class="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&amp;labelColor=555555&amp;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&amp;labelColor=555555&amp;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&amp;labelColor=555555&amp;logo=docs.rs" alt="docs-rs" /></a></p>
<br>
<p>Pure Rust implementation of Ryū, an algorithm to quickly convert floating
point numbers to decimal strings.</p>
<p>The PLDI18 paper <a href="https://dl.acm.org/citation.cfm?id=3192369"><em>Ryū: fast float-to-string conversion</em></a> by Ulf
Adams includes a complete correctness proof of the algorithm. The paper is
available under the creative commons CC-BY-SA license.</p>
<p>This Rust implementation is a line-by-line port of Ulf Adams implementation
in C, <a href="https://github.com/ulfjack/ryu">https://github.com/ulfjack/ryu</a>.</p>
<h2 id="example"><a href="#example">Example</a></h2>
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">fn </span>main() {
<span class="kw">let </span><span class="kw-2">mut </span>buffer = ryu::Buffer::new();
<span class="kw">let </span>printed = buffer.format(<span class="number">1.234</span>);
<span class="macro">assert_eq!</span>(printed, <span class="string">"1.234"</span>);
}</code></pre></div>
<h3 id="performance-lower-is-better"><a href="#performance-lower-is-better">Performance (lower is better)</a></h3>
<p><img src="https://raw.githubusercontent.com/dtolnay/ryu/master/performance.png" alt="performance" /></p>
<p>You can run upstreams benchmarks with:</p>
<div class="example-wrap"><pre class="language-console"><code>$ git clone https://github.com/ulfjack/ryu c-ryu
$ cd c-ryu
$ bazel run -c opt //ryu/benchmark
</code></pre></div>
<p>And the same benchmark against our implementation with:</p>
<div class="example-wrap"><pre class="language-console"><code>$ git clone https://github.com/dtolnay/ryu rust-ryu
$ cd rust-ryu
$ cargo run --example upstream_benchmark --release
</code></pre></div>
<p>These benchmarks measure the average time to print a 32-bit float and average
time to print a 64-bit float, where the inputs are distributed as uniform random
bit patterns 32 and 64 bits wide.</p>
<p>The upstream C code, the unsafe direct Rust port, and the safe pretty Rust API
all perform the same, taking around 21 nanoseconds to format a 32-bit float and
31 nanoseconds to format a 64-bit float.</p>
<p>There is also a Rust-specific benchmark comparing this implementation to the
standard library which you can run with:</p>
<div class="example-wrap"><pre class="language-console"><code>$ cargo bench
</code></pre></div>
<p>The benchmark shows Ryū approximately 2-5x faster than the standard library
across a range of f32 and f64 inputs. Measurements are in nanoseconds per
iteration; smaller is better.</p>
<h3 id="formatting"><a href="#formatting">Formatting</a></h3>
<p>This library tends to produce more human-readable output than the standard
librarys to_string, which never uses scientific notation. Here are two
examples:</p>
<ul>
<li><em>ryu:</em> 1.23e40, <em>std:</em> 12300000000000000000000000000000000000000</li>
<li><em>ryu:</em> 1.23e-40, <em>std:</em> 0.000000000000000000000000000000000000000123</li>
</ul>
<p>Both libraries print short decimals such as 0.0000123 without scientific
notation.</p>
</div></details><h2 id="modules" class="section-header"><a href="#modules">Modules</a></h2><ul class="item-table"><li><div class="item-name"><a class="mod" href="raw/index.html" title="mod ryu::raw">raw</a></div><div class="desc docblock-short">Unsafe functions that mirror the API of the C implementation of Ryū.</div></li></ul><h2 id="structs" class="section-header"><a href="#structs">Structs</a></h2><ul class="item-table"><li><div class="item-name"><a class="struct" href="struct.Buffer.html" title="struct ryu::Buffer">Buffer</a></div><div class="desc docblock-short">Safe API for formatting floating point numbers to text.</div></li></ul><h2 id="traits" class="section-header"><a href="#traits">Traits</a></h2><ul class="item-table"><li><div class="item-name"><a class="trait" href="trait.Float.html" title="trait ryu::Float">Float</a></div><div class="desc docblock-short">A floating point number, f32 or f64, that can be written into a
<a href="struct.Buffer.html" title="struct ryu::Buffer"><code>ryu::Buffer</code></a>.</div></li></ul></section></div></main></body></html>