source: trunk/libs/newlib/src/newlib/libm/math/e_atanh.c @ 466

Last change on this file since 466 was 444, checked in by satin@…, 7 years ago

add newlib,libalmos-mkh, restructure shared_syscalls.h and mini-libc

File size: 1.7 KB
Line 
1
2/* @(#)e_atanh.c 5.1 93/09/24 */
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 * ====================================================
12 *
13 */
14
15/* __ieee754_atanh(x)
16 * Method :
17 *    1.Reduced x to positive by atanh(-x) = -atanh(x)
18 *    2.For x>=0.5
19 *                  1              2x                          x
20 *      atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
21 *                  2             1 - x                      1 - x
22 *     
23 *      For x<0.5
24 *      atanh(x) = 0.5*log1p(2x+2x*x/(1-x))
25 *
26 * Special cases:
27 *      atanh(x) is NaN if |x| > 1 with signal;
28 *      atanh(NaN) is that NaN with no signal;
29 *      atanh(+-1) is +-INF with signal.
30 *
31 */
32
33#include "fdlibm.h"
34
35#ifndef _DOUBLE_IS_32BITS
36
37#ifdef __STDC__
38static const double one = 1.0, huge = 1e300;
39#else
40static double one = 1.0, huge = 1e300;
41#endif
42
43#ifdef __STDC__
44static const double zero = 0.0;
45#else
46static double zero = 0.0;
47#endif
48
49#ifdef __STDC__
50        double __ieee754_atanh(double x)
51#else
52        double __ieee754_atanh(x)
53        double x;
54#endif
55{
56        double t;
57        __int32_t hx,ix;
58        __uint32_t lx;
59        EXTRACT_WORDS(hx,lx,x);
60        ix = hx&0x7fffffff;
61        if ((ix|((lx|(-lx))>>31))>0x3ff00000) /* |x|>1 */
62            return (x-x)/(x-x);
63        if(ix==0x3ff00000) 
64            return x/zero;
65        if(ix<0x3e300000&&(huge+x)>zero) return x;      /* x<2**-28 */
66        SET_HIGH_WORD(x,ix);
67        if(ix<0x3fe00000) {             /* x < 0.5 */
68            t = x+x;
69            t = 0.5*log1p(t+t*x/(one-x));
70        } else 
71            t = 0.5*log1p((x+x)/(one-x));
72        if(hx>=0) return t; else return -t;
73}
74
75#endif /* defined(_DOUBLE_IS_32BITS) */
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