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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"><title>ryu - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Italic-81dc35de.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-MediumItalic-ccf7e434.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2"href="../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../static.files/rustdoc-ca0dd0c4.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="1.93.1 (01f6ddf75 2026-02-11) (Arch Linux rust 1:1.93.1-1)" data-channel="1.93.1" data-search-js="search-9e2438ea.js" data-stringdex-js="stringdex-a3946164.js" data-settings-js="settings-c38705f0.js" ><script src="../static.files/storage-e2aeef58.js"></script><script defer src="../crates.js"></script><script defer src="../static.files/main-a410ff4d.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-263c88ec.css"></noscript><link rel="alternate icon" type="image/png" href="../static.files/favicon-32x32-eab170b8.png"><link rel="icon" type="image/svg+xml" href="../static.files/favicon-044be391.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]--><rustdoc-topbar><h2><a href="#">Crate ryu</a></h2></rustdoc-topbar><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../ryu/index.html">ryu</a><span class="version">1.0.23</span></h2></div><div class="sidebar-elems"><ul class="block"><li><a id="all-types" href="all.html">All Items</a></li></ul><section id="rustdoc-toc"><h3><a href="#">Sections</a></h3><ul class="block top-toc"><li><a href="#example" title="Example">Example</a><ul><li><a href="#performance" title="Performance">Performance</a></li><li><a href="#formatting" title="Formatting">Formatting</a></li></ul></li></ul><h3><a href="#modules">Crate Items</a></h3><ul class="block"><li><a href="#modules" title="Modules">Modules</a></li><li><a href="#structs" title="Structs">Structs</a></li><li><a href="#traits" title="Traits">Traits</a></li></ul></section><div id="rustdoc-modnav"></div></div></nav><div class="sidebar-resizer" title="Drag to resize sidebar"></div><main><div class="width-limiter"><section id="main-content" class="content"><div class="main-heading"><h1>Crate <span>ryu</span> <button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><rustdoc-toolbar></rustdoc-toolbar><span class="sub-heading"><a class="src" href="../src/ryu/lib.rs.html#1-134">Source</a> </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&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&logo=docs.rs" 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"><a class="doc-anchor" href="#example">§</a>Example</h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">fn </span>main() {
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<span class="kw">let </span><span class="kw-2">mut </span>buffer = ryu::Buffer::new();
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<span class="kw">let </span>printed = buffer.format(<span class="number">1.234</span>);
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<span class="macro">assert_eq!</span>(printed, <span class="string">"1.234"</span>);
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}</code></pre></div><h3 id="performance"><a class="doc-anchor" href="#performance">§</a>Performance</h3>
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<p>The <a href="https://github.com/dtolnay/dtoa-benchmark">dtoa-benchmark</a> compares this library and other Rust floating point
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formatting implementations across a range of precisions. The vertical axis
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in this chart shows nanoseconds taken by a single execution of
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<code>ryu::Buffer::new().format_finite(value)</code> so a lower result indicates a
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faster library.</p>
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<p><img src="https://raw.githubusercontent.com/dtolnay/ryu/master/dtoa-benchmark.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"><a class="doc-anchor" href="#formatting">§</a>Formatting</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="section-header">Modules<a href="#modules" class="anchor">§</a></h2><dl class="item-table"><dt><a class="mod" href="raw/index.html" title="mod ryu::raw">raw</a></dt><dd>Unsafe functions that mirror the API of the C implementation of Ryū.</dd></dl><h2 id="structs" class="section-header">Structs<a href="#structs" class="anchor">§</a></h2><dl class="item-table"><dt><a class="struct" href="struct.Buffer.html" title="struct ryu::Buffer">Buffer</a></dt><dd>Safe API for formatting floating point numbers to text.</dd></dl><h2 id="traits" class="section-header">Traits<a href="#traits" class="anchor">§</a></h2><dl class="item-table"><dt><a class="trait" href="trait.Float.html" title="trait ryu::Float">Float</a></dt><dd>A floating point number, f32 or f64, that can be written into a
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<a href="struct.Buffer.html" title="struct ryu::Buffer"><code>ryu::Buffer</code></a>.</dd></dl></section></div></main></body></html> |