| <!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="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/rand_distr-0.4.3/src/unit_circle.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>unit_circle.rs - source</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" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="icon" href="https://www.rust-lang.org/favicon.ico"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../rand_distr/index.html"><div class="logo-container"> |
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| </pre><pre class="rust"><code><span class="comment">// Copyright 2018 Developers of the Rand project. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| </span><span class="kw">use </span>num_traits::Float; |
| <span class="kw">use crate</span>::{uniform::SampleUniform, Distribution, Uniform}; |
| <span class="kw">use </span>rand::Rng; |
| |
| <span class="doccomment">/// Samples uniformly from the edge of the unit circle in two dimensions. |
| /// |
| /// Implemented via a method by von Neumann[^1]. |
| /// |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use rand_distr::{UnitCircle, Distribution}; |
| /// |
| /// let v: [f64; 2] = UnitCircle.sample(&mut rand::thread_rng()); |
| /// println!("{:?} is from the unit circle.", v) |
| /// ``` |
| /// |
| /// [^1]: von Neumann, J. (1951) [*Various Techniques Used in Connection with |
| /// Random Digits.*](https://mcnp.lanl.gov/pdf_files/nbs_vonneumann.pdf) |
| /// NBS Appl. Math. Ser., No. 12. Washington, DC: U.S. Government Printing |
| /// Office, pp. 36-38. |
| </span><span class="attribute">#[derive(Clone, Copy, Debug)] |
| #[cfg_attr(feature = <span class="string">"serde1"</span>, derive(serde::Serialize, serde::Deserialize))] |
| </span><span class="kw">pub struct </span>UnitCircle; |
| |
| <span class="kw">impl</span><F: Float + SampleUniform> Distribution<[F; <span class="number">2</span>]> <span class="kw">for </span>UnitCircle { |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>sample<R: Rng + <span class="question-mark">?</span>Sized>(<span class="kw-2">&</span><span class="self">self</span>, rng: <span class="kw-2">&mut </span>R) -> [F; <span class="number">2</span>] { |
| <span class="kw">let </span>uniform = Uniform::new(F::from(-<span class="number">1.</span>).unwrap(), F::from(<span class="number">1.</span>).unwrap()); |
| <span class="kw">let </span><span class="kw-2">mut </span>x1; |
| <span class="kw">let </span><span class="kw-2">mut </span>x2; |
| <span class="kw">let </span><span class="kw-2">mut </span>sum; |
| <span class="kw">loop </span>{ |
| x1 = uniform.sample(rng); |
| x2 = uniform.sample(rng); |
| sum = x1 * x1 + x2 * x2; |
| <span class="kw">if </span>sum < F::from(<span class="number">1.</span>).unwrap() { |
| <span class="kw">break</span>; |
| } |
| } |
| <span class="kw">let </span>diff = x1 * x1 - x2 * x2; |
| [diff / sum, F::from(<span class="number">2.</span>).unwrap() * x1 * x2 / sum] |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use </span><span class="kw">super</span>::UnitCircle; |
| <span class="kw">use </span><span class="kw">crate</span>::Distribution; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>norm() { |
| <span class="kw">let </span><span class="kw-2">mut </span>rng = <span class="kw">crate</span>::test::rng(<span class="number">1</span>); |
| <span class="kw">for _ in </span><span class="number">0</span>..<span class="number">1000 </span>{ |
| <span class="kw">let </span>x: [f64; <span class="number">2</span>] = UnitCircle.sample(<span class="kw-2">&mut </span>rng); |
| <span class="macro">assert_almost_eq!</span>(x[<span class="number">0</span>] * x[<span class="number">0</span>] + x[<span class="number">1</span>] * x[<span class="number">1</span>], <span class="number">1.</span>, <span class="number">1e-15</span>); |
| } |
| } |
| } |
| </code></pre></div> |
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