<!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/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="../../../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_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="attr">#[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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