1/* s_atanhl.c -- long double version of s_atan.c.
2 * Conversion to long double by Ulrich Drepper,
3 * Cygnus Support, drepper@cygnus.com.
4 */
5
6/*
7 * ====================================================
8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 *
10 * Developed at SunPro, a Sun Microsystems, Inc. business.
11 * Permission to use, copy, modify, and distribute this
12 * software is freely granted, provided that this notice
13 * is preserved.
14 * ====================================================
15 */
16
17#if defined(LIBM_SCCS) && !defined(lint)
18static char rcsid[] = "$NetBSD: $";
19#endif
20
21/* __ieee754_atanhl(x)
22 * Method :
23 *    1.Reduced x to positive by atanh(-x) = -atanh(x)
24 *    2.For x>=0.5
25 *                   1              2x                          x
26 *	atanhl(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
27 *                   2             1 - x                      1 - x
28 *
29 * 	For x<0.5
30 *	atanhl(x) = 0.5*log1pl(2x+2x*x/(1-x))
31 *
32 * Special cases:
33 *	atanhl(x) is NaN if |x| > 1 with signal;
34 *	atanhl(NaN) is that NaN with no signal;
35 *	atanhl(+-1) is +-INF with signal.
36 *
37 */
38
39#include "math.h"
40#include "math_private.h"
41
42#ifdef __STDC__
43static const long double one = 1.0, huge = 1e4900L;
44#else
45static long double one = 1.0, huge = 1e4900L;
46#endif
47
48#ifdef __STDC__
49static const long double zero = 0.0;
50#else
51static double long zero = 0.0;
52#endif
53
54#ifdef __STDC__
55	long double __ieee754_atanhl(long double x)
56#else
57	long double __ieee754_atanhl(x)
58	long double x;
59#endif
60{
61	long double t;
62	int32_t ix;
63	u_int32_t se,i0,i1;
64	GET_LDOUBLE_WORDS(se,i0,i1,x);
65	ix = se&0x7fff;
66	if ((ix+((((i0&0x7fffffff)|i1)|(-((i0&0x7fffffff)|i1)))>>31))>0x3fff)
67	  /* |x|>1 */
68	    return (x-x)/(x-x);
69	if(ix==0x3fff)
70	    return x/zero;
71	if(ix<0x3fe3&&(huge+x)>zero) return x;	/* x<2**-28 */
72	SET_LDOUBLE_EXP(x,ix);
73	if(ix<0x3ffe) {		/* x < 0.5 */
74	    t = x+x;
75	    t = 0.5*__log1pl(t+t*x/(one-x));
76	} else
77	    t = 0.5*__log1pl((x+x)/(one-x));
78	if(se<=0x7fff) return t; else return -t;
79}
80