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/* Calculate the hyperbolic arc tangent (atanh) for _Decimal32 type
Copyright (C) 2006 IBM Corporation.
Author(s): Pete Eberlein <eberlein@us.ibm.com>
The Decimal Floating Point C Library is free software; you can
redistribute it and/or modify it under the terms of the GNU Lesser
General Public License version 2.1.
The Decimal Floating Point 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 version 2.1 for more details.
You should have received a copy of the GNU Lesser General Public
License version 2.1 along with the Decimal Floating Point C Library;
if not, write to the Free Software Foundation, Inc., 59 Temple Place,
Suite 330, Boston, MA 02111-1307 USA.
Please see dfp/COPYING.txt for more information. */
#ifndef _DECIMAL_SIZE
# define _DECIMAL_SIZE 32
# include <decimal32.h>
#endif
#include <decContext.h>
#include <decNumber.h>
#include <math.h>
#include <errno.h>
#include <decNumberMath.h>
#define FUNCTION_NAME atanh
#include <dfpmacro.h>
DEC_TYPE
IEEE_FUNCTION_NAME (DEC_TYPE x)
{
decContext context;
decNumber dn_result;
DEC_TYPE result, one, temp;
decNumber dn_x, dn_temp, dn_one;
/* int comp;*/
one=DFP_CONSTANT(1.0);
FUNC_CONVERT_TO_DN (&one, &dn_one);
FUNC_CONVERT_TO_DN (&x, &dn_x);
/* Handle NaN and early exit for x==0 */
if (___decNumberIsNaN (&dn_x) || ___decNumberIsZero (&dn_x))
return x + x;
___decContextDefault (&context, DEFAULT_CONTEXT);
___decNumberAbs (&dn_temp, &dn_x, &context);
FUNC_CONVERT_FROM_DN (&dn_temp, &temp, &context);
if(temp==one) {
/* |x| == 1 -> Pole Error */
DFP_EXCEPT (FE_DIVBYZERO);
return ___decNumberIsNegative(&dn_x) ? -DFP_HUGE_VAL:DFP_HUGE_VAL;
} else if (temp>one) {
/* |x| > 1 -> Domain Error (this handles +-Inf too) */
DFP_EXCEPT (FE_INVALID);
return DFP_NAN;
}
// comp = ___decCompare (&dn_temp, &dn_one);
// switch (comp)
// {
// case 0: /* |x| == 1 -> Pole Error */
// DFP_EXCEPT (FE_DIVBYZERO);
// return ___decNumberIsNegative(&dn_x) ? -DFP_HUGE_VAL:DFP_HUGE_VAL;
// case 1: /* |x| > 1 -> Domain Error (this handles +-Inf too) */
// DFP_EXCEPT (FE_INVALID);
// return DFP_NAN;
// }
/* Using trig identity: atanh(x) = 1/2 * log((1+x)/(1-x)) */
___decNumberAdd (&dn_result, &dn_one, &dn_x, &context);
___decNumberSubtract (&dn_temp, &dn_one, &dn_x, &context);
___decNumberDivide (&dn_result, &dn_result, &dn_temp, &context);
___decNumberLn (&dn_result, &dn_result, &context);
___decNumberAdd (&dn_temp, &dn_one, &dn_one, &context); /* 2 */
___decNumberDivide (&dn_result, &dn_result, &dn_temp, &context);
FUNC_CONVERT_FROM_DN (&dn_result, &result, &context);
return result;
}
DEC_TYPE
INTERNAL_FUNCTION_NAME (DEC_TYPE x)
{
DEC_TYPE z = IEEE_FUNCTION_NAME (x);
#ifndef _IEEE_LIBDFP
if(_LIB_VERSION == _IEEE_) return z;
if (x < DFP_CONSTANT(-1.0) || x > DFP_CONSTANT(1.0))
DFP_ERRNO (EDOM);
/* The normal glibc ieee754 k_standard.c file does not follow c99 or POSIX
* with regard to atanh pole errors. atan(+-1.0) [the binary version] will
* set errno to EDOM. Hopefully this will get worked out soon. */
if (x == DFP_CONSTANT(-1.0) || x == DFP_CONSTANT(1.0))
DFP_ERRNO (ERANGE);
#endif
return z;
}
weak_alias (INTERNAL_FUNCTION_NAME, EXTERNAL_FUNCTION_NAME)
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