/* Copyright (C) 2011-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

/* __ieee754_atanh(x)

   Method :

      1.Reduced x to positive by atanh(-x) = -atanh(x)

      2.For x>=0.5

		    1              2x                          x

	atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)

		    2             1 - x                      1 - x

	For x<0.5

	atanh(x) = 0.5*log1p(2x+2x*x/(1-x))

   Special cases:

	atanh(x) is NaN if |x| > 1 with signal;

	atanh(NaN) is that NaN with no signal;

	atanh(+-1) is +-INF with signal.

 */

#include <float.h>

#include <inttypes.h>

#include <math.h>

#include <math-barriers.h>

#include <math_private.h>

#include <math-underflow.h>

static const float huge = 1e30;

float

__ieee754_atanhf (float x)

{

  float xa = fabsf (x);

  float t;

  if (isless (xa, 0.5f))

    {

      if (__glibc_unlikely (xa < 0x1.0p-28f))

	{

	  math_force_eval (huge + x);

	  math_check_force_underflow (x);

	  return x;

	}

      t = xa + xa;

      t = 0.5f * __log1pf (t + t * xa / (1.0f - xa));

    }

  else if (__glibc_likely (isless (xa, 1.0f)))

    t = 0.5f * __log1pf ((xa + xa) / (1.0f - xa));

  else

    {

      if (isgreater (xa, 1.0f))

	return (x - x) / (x - x);

      return x / 0.0f;

    }

  return __copysignf (t, x);

}

strong_alias (__ieee754_atanhf, __atanhf_finite)