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/* Calculates the arc that has the given tangent for a _Decimal32 type
Copyright (C) 2006 IBM Corporation.
Copyright (C) 2007-2015 Free Software Foundation, Inc.
This file is part of the Decimal Floating Point C Library.
Author(s): Pete Eberlein <eberlein@us.ibm.com>
Joseph Kerian <jkerian@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 libdfp/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 <decNumberMath.h>
#define FUNCTION_NAME atan2
#include <dfpmacro.h>
DEC_TYPE
INTERNAL_FUNCTION_NAME (DEC_TYPE y, DEC_TYPE x)
{
/* This needs to be kept in the range of _Decimal32, and only added
* to fairly large numbers (sizeable fractions of pi) */
const DEC_TYPE generate_inexact = DFP_CONSTANT(1e-94);
decContext context;
decNumber dn_result, dn_temp;
DEC_TYPE result;
decNumber dn_x, dn_y;
FUNC_CONVERT_TO_DN (&x, &dn_x);
FUNC_CONVERT_TO_DN (&y, &dn_y);
/* If either argument is NaN, return NaN */
if (decNumberIsNaN (&dn_x) || decNumberIsNaN (&dn_y))
return x+y;
/* If x,y are both non-inf, non-NaN, non-zero, calculate as normal */
if (!decNumberIsInfinite (&dn_x) && !decNumberIsZero (&dn_y)
&& !decNumberIsInfinite (&dn_y) && !decNumberIsZero (&dn_x))
{
decContextDefault (&context, DEFAULT_CONTEXT);
decNumberDivide (&dn_temp, &dn_y, &dn_x, &context);
decNumberAtan (&dn_result, &dn_temp, &context);
FUNC_CONVERT_FROM_DN (&dn_result, &result, &context);
/* decNumberAtan doesn't quite return the values in the ranges we
* want for x < 0. So we need to do some correction */
if (decNumberIsNegative (&dn_x))
{
if (decNumberIsNegative (&dn_y))
return result - M_PIdl;
else
return result + M_PIdl;
}
else
return result;
}
/* If x and y are both inf, the result depends on the sign of x */
if (decNumberIsInfinite (&dn_y) && decNumberIsInfinite (&dn_x))
{
if (decNumberIsNegative (&dn_x) )
result = (DEC_TYPE)(3.0DL * M_PI_4dl) + generate_inexact;
else
result = (DEC_TYPE) M_PI_4dl + generate_inexact;
}
/* If y is non-zero and x is non-inf, the result is +-pi/2 */
else if (!decNumberIsZero (&dn_y) && !decNumberIsInfinite (&dn_x) )
result = (DEC_TYPE)M_PI_2dl;
else /* Otherwise it is +0 if x is positive, +pi if x is neg */
{
if (decNumberIsNegative (&dn_x))
result = ((DEC_TYPE) M_PIdl) - generate_inexact;
else
result = DFP_CONSTANT (0.0);
}
/* Atan2 will be negative if y<0 */
if (decNumberIsNegative (&dn_y))
return -result;
else
return result;
}
weak_alias (INTERNAL_FUNCTION_NAME, EXTERNAL_FUNCTION_NAME)
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