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/* __ieee754_atanhl(x)
18 * Method :
19 * 1.Reduced x to positive by atanh(-x) = -atanh(x)
20 * 2.For x>=0.5
21 * 1 2x x
22 * atanhl(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
23 * 2 1 - x 1 - x
24 *
25 * For x<0.5
26 * atanhl(x) = 0.5*log1pl(2x+2x*x/(1-x))
27 *
28 * Special cases:
29 * atanhl(x) is NaN if |x| > 1 with signal;
30 * atanhl(NaN) is that NaN with no signal;
31 * atanhl(+-1) is +-INF with signal.
32 *
33 */
34
35#include <float.h>
36#include <math.h>
37#include <math-barriers.h>
38#include <math_private.h>
39#include <math-underflow.h>
40#include <libm-alias-finite.h>
41
42static const long double one = 1.0, huge = 1e4900L;
43
44static const long double zero = 0.0;
45
46long double
47__ieee754_atanhl(long double x)
48{
49 long double t;
50 int32_t ix;
51 uint32_t se,i0,i1;
52 GET_LDOUBLE_WORDS(se,i0,i1,x);
53 ix = se&0x7fff;
54 if ((ix+((((i0&0x7fffffff)|i1)|(-((i0&0x7fffffff)|i1)))>>31))>0x3fff)
55 /* |x|>1 */
56 return (x-x)/(x-x);
57 if(ix==0x3fff)
58 return x/zero;
59 if(ix<0x3fdf) {
60 math_force_eval(huge+x);
61 math_check_force_underflow (x);
62 return x; /* x<2**-32 */
63 }
64 SET_LDOUBLE_EXP(x,ix);
65 if(ix<0x3ffe) { /* x < 0.5 */
66 t = x+x;
67 t = 0.5*__log1pl(t+t*x/(one-x));
68 } else
69 t = 0.5*__log1pl((x+x)/(one-x));
70 if(se<=0x7fff) return t; else return -t;
71}
72libm_alias_finite (__ieee754_atanhl, __atanhl)
73