Retro68/gcc/newlib/libm/complex/catan.c

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/* $NetBSD: catan.c,v 1.1 2007/08/20 16:01:32 drochner Exp $ */
/*-
* Copyright (c) 2007 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software written by Stephen L. Moshier.
* It is redistributed by the NetBSD Foundation by permission of the author.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* imported and modified include for newlib 2010/10/03
* Marco Atzeri <marco_atzeri@yahoo.it>
*/
/*
FUNCTION
<<catan>>, <<catanf>>---complex arc tangent
INDEX
catan
INDEX
catanf
ANSI_SYNOPSIS
#include <complex.h>
double complex catan(double complex <[z]>);
float complex catanf(float complex <[z]>);
DESCRIPTION
@ifnottex
These functions compute the complex arc tangent of <[z]>,
with branch cuts outside the interval [-i, +i] along the
imaginary axis.
@end ifnottex
@tex
These functions compute the complex arc tangent of <[z]>,
with branch cuts outside the interval [$-i$, $+i$] along the
imaginary axis.
@end tex
<<catanf>> is identical to <<catan>>, except that it performs
its calculations on <<floats complex>>.
RETURNS
@ifnottex
These functions return the complex arc tangent value, in the range
of a strip mathematically unbounded along the imaginary axis
and in the interval [-pi/2, +pi/2] along the real axis.
@end ifnottex
@tex
These functions return the complex arc tangent, in the range
of a strip mathematically unbounded along the imaginary axis
and in the interval [$-\pi/2$, $+\pi/2$] along the real axis.
@end tex
PORTABILITY
<<catan>> and <<catanf>> are ISO C99
QUICKREF
<<catan>> and <<catanf>> are ISO C99
*/
#include <complex.h>
#include <math.h>
#include "cephes_subr.h"
#ifdef __weak_alias
__weak_alias(catan, _catan)
#endif
double complex
catan(double complex z)
{
double complex w;
double a, t, x, x2, y;
x = creal(z);
y = cimag(z);
if ((x == 0.0) && (y > 1.0))
goto ovrf;
x2 = x * x;
a = 1.0 - x2 - (y * y);
if (a == 0.0)
goto ovrf;
t = 0.5 * atan2(2.0 * x, a);
w = _redupi(t);
t = y - 1.0;
a = x2 + (t * t);
if (a == 0.0)
goto ovrf;
t = y + 1.0;
a = (x2 + (t * t))/a;
w = w + (0.25 * log(a)) * I;
return w;
ovrf:
#if 0
mtherr ("catan", OVERFLOW);
#endif
w = HUGE_VAL + HUGE_VAL * I;
return w;
}