| <!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/expf.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>expf.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_expf.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>::scalbnf; |
| |
| <span class="kw">const </span>HALF: [f32; <span class="number">2</span>] = [<span class="number">0.5</span>, -<span class="number">0.5</span>]; |
| <span class="kw">const </span>LN2_HI: f32 = <span class="number">6.9314575195e-01</span>; <span class="comment">/* 0x3f317200 */ |
| </span><span class="kw">const </span>LN2_LO: f32 = <span class="number">1.4286067653e-06</span>; <span class="comment">/* 0x35bfbe8e */ |
| </span><span class="kw">const </span>INV_LN2: f32 = <span class="number">1.4426950216e+00</span>; <span class="comment">/* 0x3fb8aa3b */ |
| /* |
| * Domain [-0.34568, 0.34568], range ~[-4.278e-9, 4.447e-9]: |
| * |x*(exp(x)+1)/(exp(x)-1) - p(x)| < 2**-27.74 |
| */ |
| </span><span class="kw">const </span>P1: f32 = <span class="number">1.6666625440e-1</span>; <span class="comment">/* 0xaaaa8f.0p-26 */ |
| </span><span class="kw">const </span>P2: f32 = -<span class="number">2.7667332906e-3</span>; <span class="comment">/* -0xb55215.0p-32 */ |
| |
| </span><span class="doccomment">/// Exponential, base *e* (f32) |
| /// |
| /// Calculate the exponential of `x`, that is, *e* raised to the power `x` |
| /// (where *e* is the base of the natural system of logarithms, approximately 2.71828). |
| </span><span class="attribute">#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
| </span><span class="kw">pub fn </span>expf(<span class="kw-2">mut </span>x: f32) -> f32 { |
| <span class="kw">let </span>x1p127 = f32::from_bits(<span class="number">0x7f000000</span>); <span class="comment">// 0x1p127f === 2 ^ 127 |
| </span><span class="kw">let </span>x1p_126 = f32::from_bits(<span class="number">0x800000</span>); <span class="comment">// 0x1p-126f === 2 ^ -126 /*original 0x1p-149f ??????????? */ |
| </span><span class="kw">let </span><span class="kw-2">mut </span>hx = x.to_bits(); |
| <span class="kw">let </span>sign = (hx >> <span class="number">31</span>) <span class="kw">as </span>i32; <span class="comment">/* sign bit of x */ |
| </span><span class="kw">let </span>signb: bool = sign != <span class="number">0</span>; |
| hx &= <span class="number">0x7fffffff</span>; <span class="comment">/* high word of |x| */ |
| |
| /* special cases */ |
| </span><span class="kw">if </span>hx >= <span class="number">0x42aeac50 </span>{ |
| <span class="comment">/* if |x| >= -87.33655f or NaN */ |
| </span><span class="kw">if </span>hx > <span class="number">0x7f800000 </span>{ |
| <span class="comment">/* NaN */ |
| </span><span class="kw">return </span>x; |
| } |
| <span class="kw">if </span>(hx >= <span class="number">0x42b17218</span>) && (!signb) { |
| <span class="comment">/* x >= 88.722839f */ |
| /* overflow */ |
| </span>x <span class="kw-2">*</span>= x1p127; |
| <span class="kw">return </span>x; |
| } |
| <span class="kw">if </span>signb { |
| <span class="comment">/* underflow */ |
| </span><span class="macro">force_eval!</span>(-x1p_126 / x); |
| <span class="kw">if </span>hx >= <span class="number">0x42cff1b5 </span>{ |
| <span class="comment">/* x <= -103.972084f */ |
| </span><span class="kw">return </span><span class="number">0.</span>; |
| } |
| } |
| } |
| |
| <span class="comment">/* argument reduction */ |
| </span><span class="kw">let </span>k: i32; |
| <span class="kw">let </span>hi: f32; |
| <span class="kw">let </span>lo: f32; |
| <span class="kw">if </span>hx > <span class="number">0x3eb17218 </span>{ |
| <span class="comment">/* if |x| > 0.5 ln2 */ |
| </span><span class="kw">if </span>hx > <span class="number">0x3f851592 </span>{ |
| <span class="comment">/* if |x| > 1.5 ln2 */ |
| </span>k = (INV_LN2 * x + <span class="macro">i!</span>(HALF, sign <span class="kw">as </span>usize)) <span class="kw">as </span>i32; |
| } <span class="kw">else </span>{ |
| k = <span class="number">1 </span>- sign - sign; |
| } |
| <span class="kw">let </span>kf = k <span class="kw">as </span>f32; |
| hi = x - kf * LN2_HI; <span class="comment">/* k*ln2hi is exact here */ |
| </span>lo = kf * LN2_LO; |
| x = hi - lo; |
| } <span class="kw">else if </span>hx > <span class="number">0x39000000 </span>{ |
| <span class="comment">/* |x| > 2**-14 */ |
| </span>k = <span class="number">0</span>; |
| hi = x; |
| lo = <span class="number">0.</span>; |
| } <span class="kw">else </span>{ |
| <span class="comment">/* raise inexact */ |
| </span><span class="macro">force_eval!</span>(x1p127 + x); |
| <span class="kw">return </span><span class="number">1. </span>+ x; |
| } |
| |
| <span class="comment">/* x is now in primary range */ |
| </span><span class="kw">let </span>xx = x * x; |
| <span class="kw">let </span>c = x - xx * (P1 + xx * P2); |
| <span class="kw">let </span>y = <span class="number">1. </span>+ (x * c / (<span class="number">2. </span>- c) - lo + hi); |
| <span class="kw">if </span>k == <span class="number">0 </span>{ |
| y |
| } <span class="kw">else </span>{ |
| scalbnf(y, k) |
| } |
| } |
| </code></pre></div> |
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