<!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 `/Users/erlendbasso/.cargo/registry/src/github.com-1ecc6299db9ec823/libm-0.2.6/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="../../../static.files/SourceSerif4-Regular-1f7d512b176f0f72.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/SourceSerif4-Bold-124a1ca42af929b6.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-6827029ac823cab7.css" id="mainThemeStyle"><link rel="stylesheet" id="themeStyle" href="../../../static.files/light-ebce58d0a40c3431.css"><link rel="stylesheet" disabled href="../../../static.files/dark-f23faae4a2daf9a6.css"><link rel="stylesheet" disabled href="../../../static.files/ayu-8af5e100b21cd173.css"><script id="default-settings" ></script><script src="../../../static.files/storage-d43fa987303ecbbb.js"></script><script defer src="../../../static.files/source-script-5cf2e01a42cc9858.js"></script><script defer src="../../../source-files.js"></script><script defer src="../../../static.files/main-c55e1eb52e1886b4.js"></script><noscript><link rel="stylesheet" href="../../../static.files/noscript-13285aec31fa243e.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 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"></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../libm/index.html"><img class="rust-logo" src="../../../static.files/rust-logo-151179464ae7ed46.svg" alt="logo"></a><form class="search-form"><span></span><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" 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="../../../static.files/wheel-5ec35bf9ca753509.svg"></a></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><a href="#1" id="1">1</a>
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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="attr">#[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="attr">#[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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