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 /* s_atanhl.c -- __float128 version of s_atan.c. * Conversion to __float128 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. * ==================================================== */ /* atanhq(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 "quadmath-imp.h" static const __float128 one = 1.0Q, huge = 1e4900Q; static const __float128 zero = 0.0Q; __float128 atanhq (__float128 x) { __float128 t; uint32_t jx, ix; ieee854_float128 u; u.value = x; jx = u.words32.w0; ix = jx & 0x7fffffff; u.words32.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) /* x < 2^-57 */ { math_check_force_underflow (x); return x; } if(ix<0x3ffe0000) { /* x < 0.5 */ t = u.value+u.value; t = 0.5*log1pq(t+t*u.value/(one-u.value)); } else t = 0.5*log1pq((u.value+u.value)/(one-u.value)); if(jx & 0x80000000) return -t; else return t; }