<!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/atanf.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>atanf.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/s_atanf.c */
/*
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
*/
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
</span><span class="kw">use </span><span class="kw">super</span>::fabsf;
<span class="kw">const </span>ATAN_HI: [f32; <span class="number">4</span>] = [
<span class="number">4.6364760399e-01</span>, <span class="comment">/* atan(0.5)hi 0x3eed6338 */
</span><span class="number">7.8539812565e-01</span>, <span class="comment">/* atan(1.0)hi 0x3f490fda */
</span><span class="number">9.8279368877e-01</span>, <span class="comment">/* atan(1.5)hi 0x3f7b985e */
</span><span class="number">1.5707962513e+00</span>, <span class="comment">/* atan(inf)hi 0x3fc90fda */
</span>];
<span class="kw">const </span>ATAN_LO: [f32; <span class="number">4</span>] = [
<span class="number">5.0121582440e-09</span>, <span class="comment">/* atan(0.5)lo 0x31ac3769 */
</span><span class="number">3.7748947079e-08</span>, <span class="comment">/* atan(1.0)lo 0x33222168 */
</span><span class="number">3.4473217170e-08</span>, <span class="comment">/* atan(1.5)lo 0x33140fb4 */
</span><span class="number">7.5497894159e-08</span>, <span class="comment">/* atan(inf)lo 0x33a22168 */
</span>];
<span class="kw">const </span>A_T: [f32; <span class="number">5</span>] = [
<span class="number">3.3333328366e-01</span>,
-<span class="number">1.9999158382e-01</span>,
<span class="number">1.4253635705e-01</span>,
-<span class="number">1.0648017377e-01</span>,
<span class="number">6.1687607318e-02</span>,
];
<span class="doccomment">/// Arctangent (f32)
///
/// Computes the inverse tangent (arc tangent) of the input value.
/// Returns a value in radians, in the range of -pi/2 to pi/2.
</span><span class="attr">#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
</span><span class="kw">pub fn </span>atanf(<span class="kw-2">mut </span>x: f32) -> f32 {
<span class="kw">let </span>x1p_120 = f32::from_bits(<span class="number">0x03800000</span>); <span class="comment">// 0x1p-120 === 2 ^ (-120)
</span><span class="kw">let </span>z: f32;
<span class="kw">let </span><span class="kw-2">mut </span>ix = x.to_bits();
<span class="kw">let </span>sign = (ix >> <span class="number">31</span>) != <span class="number">0</span>;
ix &= <span class="number">0x7fffffff</span>;
<span class="kw">if </span>ix >= <span class="number">0x4c800000 </span>{
<span class="comment">/* if |x| >= 2**26 */
</span><span class="kw">if </span>x.is_nan() {
<span class="kw">return </span>x;
}
z = <span class="macro">i!</span>(ATAN_HI, <span class="number">3</span>) + x1p_120;
<span class="kw">return if </span>sign { -z } <span class="kw">else </span>{ z };
}
<span class="kw">let </span>id = <span class="kw">if </span>ix < <span class="number">0x3ee00000 </span>{
<span class="comment">/* |x| < 0.4375 */
</span><span class="kw">if </span>ix < <span class="number">0x39800000 </span>{
<span class="comment">/* |x| < 2**-12 */
</span><span class="kw">if </span>ix < <span class="number">0x00800000 </span>{
<span class="comment">/* raise underflow for subnormal x */
</span><span class="macro">force_eval!</span>(x * x);
}
<span class="kw">return </span>x;
}
-<span class="number">1
</span>} <span class="kw">else </span>{
x = fabsf(x);
<span class="kw">if </span>ix < <span class="number">0x3f980000 </span>{
<span class="comment">/* |x| < 1.1875 */
</span><span class="kw">if </span>ix < <span class="number">0x3f300000 </span>{
<span class="comment">/* 7/16 <= |x| < 11/16 */
</span>x = (<span class="number">2. </span>* x - <span class="number">1.</span>) / (<span class="number">2. </span>+ x);
<span class="number">0
</span>} <span class="kw">else </span>{
<span class="comment">/* 11/16 <= |x| < 19/16 */
</span>x = (x - <span class="number">1.</span>) / (x + <span class="number">1.</span>);
<span class="number">1
</span>}
} <span class="kw">else if </span>ix < <span class="number">0x401c0000 </span>{
<span class="comment">/* |x| < 2.4375 */
</span>x = (x - <span class="number">1.5</span>) / (<span class="number">1. </span>+ <span class="number">1.5 </span>* x);
<span class="number">2
</span>} <span class="kw">else </span>{
<span class="comment">/* 2.4375 <= |x| < 2**26 */
</span>x = -<span class="number">1. </span>/ x;
<span class="number">3
</span>}
};
<span class="comment">/* end of argument reduction */
</span>z = x * x;
<span class="kw">let </span>w = z * z;
<span class="comment">/* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
</span><span class="kw">let </span>s1 = z * (<span class="macro">i!</span>(A_T, <span class="number">0</span>) + w * (<span class="macro">i!</span>(A_T, <span class="number">2</span>) + w * <span class="macro">i!</span>(A_T, <span class="number">4</span>)));
<span class="kw">let </span>s2 = w * (<span class="macro">i!</span>(A_T, <span class="number">1</span>) + w * <span class="macro">i!</span>(A_T, <span class="number">3</span>));
<span class="kw">if </span>id < <span class="number">0 </span>{
<span class="kw">return </span>x - x * (s1 + s2);
}
<span class="kw">let </span>id = id <span class="kw">as </span>usize;
<span class="kw">let </span>z = <span class="macro">i!</span>(ATAN_HI, id) - ((x * (s1 + s2) - <span class="macro">i!</span>(ATAN_LO, id)) - x);
<span class="kw">if </span>sign {
-z
} <span class="kw">else </span>{
z
}
}
</code></pre></div>
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