| <!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/log10f.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>log10f.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_log10f.c */ |
| /* |
| * ==================================================== |
| * 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. |
| * ==================================================== |
| */ |
| /* |
| * See comments in log10.c. |
| */ |
| |
| </span><span class="kw">use </span>core::f32; |
| |
| <span class="kw">const </span>IVLN10HI: f32 = <span class="number">4.3432617188e-01</span>; <span class="comment">/* 0x3ede6000 */ |
| </span><span class="kw">const </span>IVLN10LO: f32 = -<span class="number">3.1689971365e-05</span>; <span class="comment">/* 0xb804ead9 */ |
| </span><span class="kw">const </span>LOG10_2HI: f32 = <span class="number">3.0102920532e-01</span>; <span class="comment">/* 0x3e9a2080 */ |
| </span><span class="kw">const </span>LOG10_2LO: f32 = <span class="number">7.9034151668e-07</span>; <span class="comment">/* 0x355427db */ |
| /* |(log(1+s)-log(1-s))/s - Lg(s)| < 2**-34.24 (~[-4.95e-11, 4.97e-11]). */ |
| </span><span class="kw">const </span>LG1: f32 = <span class="number">0.66666662693</span>; <span class="comment">/* 0xaaaaaa.0p-24 */ |
| </span><span class="kw">const </span>LG2: f32 = <span class="number">0.40000972152</span>; <span class="comment">/* 0xccce13.0p-25 */ |
| </span><span class="kw">const </span>LG3: f32 = <span class="number">0.28498786688</span>; <span class="comment">/* 0x91e9ee.0p-25 */ |
| </span><span class="kw">const </span>LG4: f32 = <span class="number">0.24279078841</span>; <span class="comment">/* 0xf89e26.0p-26 */ |
| |
| </span><span class="attribute">#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
| </span><span class="kw">pub fn </span>log10f(<span class="kw-2">mut </span>x: f32) -> f32 { |
| <span class="kw">let </span>x1p25f = f32::from_bits(<span class="number">0x4c000000</span>); <span class="comment">// 0x1p25f === 2 ^ 25 |
| |
| </span><span class="kw">let </span><span class="kw-2">mut </span>ui: u32 = x.to_bits(); |
| <span class="kw">let </span>hfsq: f32; |
| <span class="kw">let </span>f: f32; |
| <span class="kw">let </span>s: f32; |
| <span class="kw">let </span>z: f32; |
| <span class="kw">let </span>r: f32; |
| <span class="kw">let </span>w: f32; |
| <span class="kw">let </span>t1: f32; |
| <span class="kw">let </span>t2: f32; |
| <span class="kw">let </span>dk: f32; |
| <span class="kw">let </span><span class="kw-2">mut </span>hi: f32; |
| <span class="kw">let </span>lo: f32; |
| <span class="kw">let </span><span class="kw-2">mut </span>ix: u32; |
| <span class="kw">let </span><span class="kw-2">mut </span>k: i32; |
| |
| ix = ui; |
| k = <span class="number">0</span>; |
| <span class="kw">if </span>ix < <span class="number">0x00800000 </span>|| (ix >> <span class="number">31</span>) > <span class="number">0 </span>{ |
| <span class="comment">/* x < 2**-126 */ |
| </span><span class="kw">if </span>ix << <span class="number">1 </span>== <span class="number">0 </span>{ |
| <span class="kw">return </span>-<span class="number">1. </span>/ (x * x); <span class="comment">/* log(+-0)=-inf */ |
| </span>} |
| <span class="kw">if </span>(ix >> <span class="number">31</span>) > <span class="number">0 </span>{ |
| <span class="kw">return </span>(x - x) / <span class="number">0.0</span>; <span class="comment">/* log(-#) = NaN */ |
| </span>} |
| <span class="comment">/* subnormal number, scale up x */ |
| </span>k -= <span class="number">25</span>; |
| x <span class="kw-2">*</span>= x1p25f; |
| ui = x.to_bits(); |
| ix = ui; |
| } <span class="kw">else if </span>ix >= <span class="number">0x7f800000 </span>{ |
| <span class="kw">return </span>x; |
| } <span class="kw">else if </span>ix == <span class="number">0x3f800000 </span>{ |
| <span class="kw">return </span><span class="number">0.</span>; |
| } |
| |
| <span class="comment">/* reduce x into [sqrt(2)/2, sqrt(2)] */ |
| </span>ix += <span class="number">0x3f800000 </span>- <span class="number">0x3f3504f3</span>; |
| k += (ix >> <span class="number">23</span>) <span class="kw">as </span>i32 - <span class="number">0x7f</span>; |
| ix = (ix & <span class="number">0x007fffff</span>) + <span class="number">0x3f3504f3</span>; |
| ui = ix; |
| x = f32::from_bits(ui); |
| |
| f = x - <span class="number">1.0</span>; |
| s = f / (<span class="number">2.0 </span>+ f); |
| z = s * s; |
| w = z * z; |
| t1 = w * (LG2 + w * LG4); |
| t2 = z * (LG1 + w * LG3); |
| r = t2 + t1; |
| hfsq = <span class="number">0.5 </span>* f * f; |
| |
| hi = f - hfsq; |
| ui = hi.to_bits(); |
| ui &= <span class="number">0xfffff000</span>; |
| hi = f32::from_bits(ui); |
| lo = f - hi - hfsq + s * (hfsq + r); |
| dk = k <span class="kw">as </span>f32; |
| dk * LOG10_2LO + (lo + hi) * IVLN10LO + lo * IVLN10HI + hi * IVLN10HI + dk * LOG10_2HI |
| } |
| </code></pre></div> |
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