/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8   -*-│
│ vi: set noet ft=c ts=8 sw=8 fenc=utf-8                                   :vi │
╚──────────────────────────────────────────────────────────────────────────────╝
│                                                                              │
│  Musl Libc                                                                   │
│  Copyright © 2005-2014 Rich Felker, et al.                                   │
│                                                                              │
│  Permission is hereby granted, free of charge, to any person obtaining       │
│  a copy of this software and associated documentation files (the             │
│  "Software"), to deal in the Software without restriction, including         │
│  without limitation the rights to use, copy, modify, merge, publish,         │
│  distribute, sublicense, and/or sell copies of the Software, and to          │
│  permit persons to whom the Software is furnished to do so, subject to       │
│  the following conditions:                                                   │
│                                                                              │
│  The above copyright notice and this permission notice shall be              │
│  included in all copies or substantial portions of the Software.             │
│                                                                              │
│  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,             │
│  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF          │
│  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.      │
│  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY        │
│  CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,        │
│  TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE           │
│  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                      │
│                                                                              │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/math.h"
#include "libc/tinymath/feval.internal.h"
__static_yoink("musl_libc_notice");


/**
 * Returns hyperbolic tangent of 𝑥.
 */
double tanh(double x)
{
	union {double f; uint64_t i;} u = {.f = x};
	uint32_t w;
	int sign;
	double_t t;

	/* x = |x| */
	sign = u.i >> 63;
	u.i &= (uint64_t)-1/2;
	x = u.f;
	w = u.i >> 32;

	if (w > 0x3fe193ea) {
		/* |x| > log(3)/2 ~= 0.5493 or nan */
		if (w > 0x40340000) {
			/* |x| > 20 or nan */
			/* note: this branch avoids raising overflow */
			t = 1 - 0/x;
		} else {
			t = expm1(2*x);
			t = 1 - 2/(t+2);
		}
	} else if (w > 0x3fd058ae) {
		/* |x| > log(5/3)/2 ~= 0.2554 */
		t = expm1(2*x);
		t = t/(t+2);
	} else if (w >= 0x00100000) {
		/* |x| >= 0x1p-1022, up to 2ulp error in [0.1,0.2554] */
		t = expm1(-2*x);
		t = -t/(t+2);
	} else {
		/* |x| is subnormal */
		/* note: the branch above would not raise underflow in [0x1p-1023,0x1p-1022) */
		fevalf(x);
		t = x;
	}
	return sign ? -t : t;
}

#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
__weak_reference(tanh, tanhl);
#endif
