| /* s_atanhl.c -- long double version of s_atan.c. |
| * Conversion to long double by Ulrich Drepper, |
| * Cygnus Support, drepper@cygnus.com. |
| */ |
| |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| */ |
| |
| /* __ieee754_atanhl(x) |
| * Method : |
| * 1.Reduced x to positive by atanh(-x) = -atanh(x) |
| * 2.For x>=0.5 |
| * 1 2x x |
| * atanhl(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------) |
| * 2 1 - x 1 - x |
| * |
| * For x<0.5 |
| * atanhl(x) = 0.5*log1pl(2x+2x*x/(1-x)) |
| * |
| * Special cases: |
| * atanhl(x) is NaN if |x| > 1 with signal; |
| * atanhl(NaN) is that NaN with no signal; |
| * atanhl(+-1) is +-INF with signal. |
| * |
| */ |
| |
| #include <math.h> |
| #include <math_private.h> |
| |
| static const long double one = 1.0L, huge = 1e4900L; |
| |
| static const long double zero = 0.0L; |
| |
| long double |
| __ieee754_atanhl(long double x) |
| { |
| long double t; |
| u_int32_t jx, ix; |
| ieee854_long_double_shape_type u; |
| |
| u.value = x; |
| jx = u.parts32.w0; |
| ix = jx & 0x7fffffff; |
| u.parts32.w0 = ix; |
| if (ix >= 0x3fff0000) /* |x| >= 1.0 or infinity or NaN */ |
| { |
| if (u.value == one) |
| return x/zero; |
| else |
| return (x-x)/(x-x); |
| } |
| if(ix<0x3fc60000 && (huge+x)>zero) return x; /* x < 2^-57 */ |
| |
| if(ix<0x3ffe0000) { /* x < 0.5 */ |
| t = u.value+u.value; |
| t = 0.5*__log1pl(t+t*u.value/(one-u.value)); |
| } else |
| t = 0.5*__log1pl((u.value+u.value)/(one-u.value)); |
| if(jx & 0x80000000) return -t; else return t; |
| } |
| strong_alias (__ieee754_atanhl, __atanhl_finite) |
