libm: Properly end some comments before starting a new one.
[dragonfly.git] / lib / libm / src / s_asinh.c
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b34b60bc 1/* @(#)s_asinh.c 5.1 93/09/24 */
219be92a 2/* $FreeBSD: head/lib/msun/src/s_asinh.c 251599 2013-06-10 06:04:58Z das $ */
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3/*
4 * ====================================================
5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 *
7 * Developed at SunPro, a Sun Microsystems, Inc. business.
8 * Permission to use, copy, modify, and distribute this
9 * software is freely granted, provided that this notice
10 * is preserved.
11 * ====================================================
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12 */
13
14/* asinh(x)
15 * Method :
16 * Based on
17 * asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ]
18 * we have
19 * asinh(x) := x if 1+x*x=1,
20 * := sign(x)*(log(x)+ln2)) for large |x|, else
21 * := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x|>2, else
22 * := sign(x)*log1p(|x| + x^2/(1 + sqrt(1+x^2)))
23 */
24
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25#include <float.h>
26
6ff43c94 27#include "math.h"
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28#include "math_private.h"
29
30static const double
31one = 1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */
32ln2 = 6.93147180559945286227e-01, /* 0x3FE62E42, 0xFEFA39EF */
33huge= 1.00000000000000000000e+300;
34
35double
36asinh(double x)
37{
38 double t,w;
39 int32_t hx,ix;
40 GET_HIGH_WORD(hx,x);
41 ix = hx&0x7fffffff;
42 if(ix>=0x7ff00000) return x+x; /* x is inf or NaN */
43 if(ix< 0x3e300000) { /* |x|<2**-28 */
44 if(huge+x>one) return x; /* return x inexact except 0 */
45 }
46 if(ix>0x41b00000) { /* |x| > 2**28 */
6ff43c94 47 w = __ieee754_log(fabs(x))+ln2;
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48 } else if (ix>0x40000000) { /* 2**28 > |x| > 2.0 */
49 t = fabs(x);
6ff43c94 50 w = __ieee754_log(2.0*t+one/(__ieee754_sqrt(x*x+one)+t));
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51 } else { /* 2.0 > |x| > 2**-28 */
52 t = x*x;
6ff43c94 53 w =log1p(fabs(x)+t/(one+__ieee754_sqrt(one+t)));
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54 }
55 if(hx>0) return w; else return -w;
56}
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57
58#if LDBL_MANT_DIG == 53
59__weak_reference(asinh, asinhl);
60#endif