| <!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/libm-0.2.7/src/math/atan2.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>atan2.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="alternate icon" type="image/png" href="../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../favicon.svg"></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="../../../libm/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../libm/index.html"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="comment">/* origin: FreeBSD /usr/src/lib/msun/src/e_atan2.c */ |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunSoft, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| * |
| */ |
| /* atan2(y,x) |
| * Method : |
| * 1. Reduce y to positive by atan2(y,x)=-atan2(-y,x). |
| * 2. Reduce x to positive by (if x and y are unexceptional): |
| * ARG (x+iy) = arctan(y/x) ... if x > 0, |
| * ARG (x+iy) = pi - arctan[y/(-x)] ... if x < 0, |
| * |
| * Special cases: |
| * |
| * ATAN2((anything), NaN ) is NaN; |
| * ATAN2(NAN , (anything) ) is NaN; |
| * ATAN2(+-0, +(anything but NaN)) is +-0 ; |
| * ATAN2(+-0, -(anything but NaN)) is +-pi ; |
| * ATAN2(+-(anything but 0 and NaN), 0) is +-pi/2; |
| * ATAN2(+-(anything but INF and NaN), +INF) is +-0 ; |
| * ATAN2(+-(anything but INF and NaN), -INF) is +-pi; |
| * ATAN2(+-INF,+INF ) is +-pi/4 ; |
| * ATAN2(+-INF,-INF ) is +-3pi/4; |
| * ATAN2(+-INF, (anything but,0,NaN, and INF)) is +-pi/2; |
| * |
| * Constants: |
| * The hexadecimal values are the intended ones for the following |
| * constants. The decimal values may be used, provided that the |
| * compiler will convert from decimal to binary accurately enough |
| * to produce the hexadecimal values shown. |
| */ |
| |
| </span><span class="kw">use </span><span class="kw">super</span>::atan; |
| <span class="kw">use </span><span class="kw">super</span>::fabs; |
| |
| <span class="kw">const </span>PI: f64 = <span class="number">3.1415926535897931160E+00</span>; <span class="comment">/* 0x400921FB, 0x54442D18 */ |
| </span><span class="kw">const </span>PI_LO: f64 = <span class="number">1.2246467991473531772E-16</span>; <span class="comment">/* 0x3CA1A626, 0x33145C07 */ |
| |
| </span><span class="doccomment">/// Arctangent of y/x (f64) |
| /// |
| /// Computes the inverse tangent (arc tangent) of `y/x`. |
| /// Produces the correct result even for angles near pi/2 or -pi/2 (that is, when `x` is near 0). |
| /// Returns a value in radians, in the range of -pi to pi. |
| </span><span class="attribute">#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
| </span><span class="kw">pub fn </span>atan2(y: f64, x: f64) -> f64 { |
| <span class="kw">if </span>x.is_nan() || y.is_nan() { |
| <span class="kw">return </span>x + y; |
| } |
| <span class="kw">let </span><span class="kw-2">mut </span>ix = (x.to_bits() >> <span class="number">32</span>) <span class="kw">as </span>u32; |
| <span class="kw">let </span>lx = x.to_bits() <span class="kw">as </span>u32; |
| <span class="kw">let </span><span class="kw-2">mut </span>iy = (y.to_bits() >> <span class="number">32</span>) <span class="kw">as </span>u32; |
| <span class="kw">let </span>ly = y.to_bits() <span class="kw">as </span>u32; |
| <span class="kw">if </span>((ix.wrapping_sub(<span class="number">0x3ff00000</span>)) | lx) == <span class="number">0 </span>{ |
| <span class="comment">/* x = 1.0 */ |
| </span><span class="kw">return </span>atan(y); |
| } |
| <span class="kw">let </span>m = ((iy >> <span class="number">31</span>) & <span class="number">1</span>) | ((ix >> <span class="number">30</span>) & <span class="number">2</span>); <span class="comment">/* 2*sign(x)+sign(y) */ |
| </span>ix &= <span class="number">0x7fffffff</span>; |
| iy &= <span class="number">0x7fffffff</span>; |
| |
| <span class="comment">/* when y = 0 */ |
| </span><span class="kw">if </span>(iy | ly) == <span class="number">0 </span>{ |
| <span class="kw">return match </span>m { |
| <span class="number">0 </span>| <span class="number">1 </span>=> y, <span class="comment">/* atan(+-0,+anything)=+-0 */ |
| </span><span class="number">2 </span>=> PI, <span class="comment">/* atan(+0,-anything) = PI */ |
| </span><span class="kw">_ </span>=> -PI, <span class="comment">/* atan(-0,-anything) =-PI */ |
| </span>}; |
| } |
| <span class="comment">/* when x = 0 */ |
| </span><span class="kw">if </span>(ix | lx) == <span class="number">0 </span>{ |
| <span class="kw">return if </span>m & <span class="number">1 </span>!= <span class="number">0 </span>{ -PI / <span class="number">2.0 </span>} <span class="kw">else </span>{ PI / <span class="number">2.0 </span>}; |
| } |
| <span class="comment">/* when x is INF */ |
| </span><span class="kw">if </span>ix == <span class="number">0x7ff00000 </span>{ |
| <span class="kw">if </span>iy == <span class="number">0x7ff00000 </span>{ |
| <span class="kw">return match </span>m { |
| <span class="number">0 </span>=> PI / <span class="number">4.0</span>, <span class="comment">/* atan(+INF,+INF) */ |
| </span><span class="number">1 </span>=> -PI / <span class="number">4.0</span>, <span class="comment">/* atan(-INF,+INF) */ |
| </span><span class="number">2 </span>=> <span class="number">3.0 </span>* PI / <span class="number">4.0</span>, <span class="comment">/* atan(+INF,-INF) */ |
| </span><span class="kw">_ </span>=> -<span class="number">3.0 </span>* PI / <span class="number">4.0</span>, <span class="comment">/* atan(-INF,-INF) */ |
| </span>}; |
| } <span class="kw">else </span>{ |
| <span class="kw">return match </span>m { |
| <span class="number">0 </span>=> <span class="number">0.0</span>, <span class="comment">/* atan(+...,+INF) */ |
| </span><span class="number">1 </span>=> -<span class="number">0.0</span>, <span class="comment">/* atan(-...,+INF) */ |
| </span><span class="number">2 </span>=> PI, <span class="comment">/* atan(+...,-INF) */ |
| </span><span class="kw">_ </span>=> -PI, <span class="comment">/* atan(-...,-INF) */ |
| </span>}; |
| } |
| } |
| <span class="comment">/* |y/x| > 0x1p64 */ |
| </span><span class="kw">if </span>ix.wrapping_add(<span class="number">64 </span><< <span class="number">20</span>) < iy || iy == <span class="number">0x7ff00000 </span>{ |
| <span class="kw">return if </span>m & <span class="number">1 </span>!= <span class="number">0 </span>{ -PI / <span class="number">2.0 </span>} <span class="kw">else </span>{ PI / <span class="number">2.0 </span>}; |
| } |
| |
| <span class="comment">/* z = atan(|y/x|) without spurious underflow */ |
| </span><span class="kw">let </span>z = <span class="kw">if </span>(m & <span class="number">2 </span>!= <span class="number">0</span>) && iy.wrapping_add(<span class="number">64 </span><< <span class="number">20</span>) < ix { |
| <span class="comment">/* |y/x| < 0x1p-64, x<0 */ |
| </span><span class="number">0.0 |
| </span>} <span class="kw">else </span>{ |
| atan(fabs(y / x)) |
| }; |
| <span class="kw">match </span>m { |
| <span class="number">0 </span>=> z, <span class="comment">/* atan(+,+) */ |
| </span><span class="number">1 </span>=> -z, <span class="comment">/* atan(-,+) */ |
| </span><span class="number">2 </span>=> PI - (z - PI_LO), <span class="comment">/* atan(+,-) */ |
| </span><span class="kw">_ </span>=> (z - PI_LO) - PI, <span class="comment">/* atan(-,-) */ |
| </span>} |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>sanity_check() { |
| <span class="macro">assert_eq!</span>(atan2(<span class="number">0.0</span>, <span class="number">1.0</span>), <span class="number">0.0</span>); |
| <span class="macro">assert_eq!</span>(atan2(<span class="number">0.0</span>, -<span class="number">1.0</span>), PI); |
| <span class="macro">assert_eq!</span>(atan2(-<span class="number">0.0</span>, -<span class="number">1.0</span>), -PI); |
| <span class="macro">assert_eq!</span>(atan2(<span class="number">3.0</span>, <span class="number">2.0</span>), atan(<span class="number">3.0 </span>/ <span class="number">2.0</span>)); |
| <span class="macro">assert_eq!</span>(atan2(<span class="number">2.0</span>, -<span class="number">1.0</span>), atan(<span class="number">2.0 </span>/ -<span class="number">1.0</span>) + PI); |
| <span class="macro">assert_eq!</span>(atan2(-<span class="number">2.0</span>, -<span class="number">1.0</span>), atan(-<span class="number">2.0 </span>/ -<span class="number">1.0</span>) - PI); |
| } |
| </code></pre></div> |
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