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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.

 * ====================================================

 */

/* __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 "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) return x;    /* x < 2^-57 */

        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;

}