<!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/tanh.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>tanh.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="kw">use </span><span class="kw">super</span>::expm1;
<span class="comment">/* tanh(x) = (exp(x) - exp(-x))/(exp(x) + exp(-x))
* = (exp(2*x) - 1)/(exp(2*x) - 1 + 2)
* = (1 - exp(-2*x))/(exp(-2*x) - 1 + 2)
*/
</span><span class="attr">#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
</span><span class="kw">pub fn </span>tanh(<span class="kw-2">mut </span>x: f64) -> f64 {
<span class="kw">let </span><span class="kw-2">mut </span>uf: f64 = x;
<span class="kw">let </span><span class="kw-2">mut </span>ui: u64 = f64::to_bits(uf);
<span class="kw">let </span>w: u32;
<span class="kw">let </span>sign: bool;
<span class="kw">let </span><span class="kw-2">mut </span>t: f64;
<span class="comment">/* x = |x| */
</span>sign = ui >> <span class="number">63 </span>!= <span class="number">0</span>;
ui &= !<span class="number">1 </span>/ <span class="number">2</span>;
uf = f64::from_bits(ui);
x = uf;
w = (ui >> <span class="number">32</span>) <span class="kw">as </span>u32;
<span class="kw">if </span>w > <span class="number">0x3fe193ea </span>{
<span class="comment">/* |x| > log(3)/2 ~= 0.5493 or nan */
</span><span class="kw">if </span>w > <span class="number">0x40340000 </span>{
<span class="comment">/* |x| > 20 or nan */
/* note: this branch avoids raising overflow */
</span>t = <span class="number">1.0 </span>- <span class="number">0.0 </span>/ x;
} <span class="kw">else </span>{
t = expm1(<span class="number">2.0 </span>* x);
t = <span class="number">1.0 </span>- <span class="number">2.0 </span>/ (t + <span class="number">2.0</span>);
}
} <span class="kw">else if </span>w > <span class="number">0x3fd058ae </span>{
<span class="comment">/* |x| > log(5/3)/2 ~= 0.2554 */
</span>t = expm1(<span class="number">2.0 </span>* x);
t = t / (t + <span class="number">2.0</span>);
} <span class="kw">else if </span>w >= <span class="number">0x00100000 </span>{
<span class="comment">/* |x| >= 0x1p-1022, up to 2ulp error in [0.1,0.2554] */
</span>t = expm1(-<span class="number">2.0 </span>* x);
t = -t / (t + <span class="number">2.0</span>);
} <span class="kw">else </span>{
<span class="comment">/* |x| is subnormal */
/* note: the branch above would not raise underflow in [0x1p-1023,0x1p-1022) */
</span><span class="macro">force_eval!</span>(x <span class="kw">as </span>f32);
t = x;
}
<span class="kw">if </span>sign {
-t
} <span class="kw">else </span>{
t
}
}
</code></pre></div>
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