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/* Copyright (C) 1991, 1992, 1994 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
#include <ansidecl.h>
#include <math.h>
#ifdef __GNUC__
__CONSTVALUE double
DEFUN(atan2, (y, x), double y AND double x)
{
static CONST double one = 1.0, zero = 0.0;
double signx, signy;
double pi, PIo4, PIo2;
if (__isnan(x))
return x;
if (__isnan(y))
return y;
signy = __copysign(one, y);
signx = __copysign(one, x);
asm("fmovecr%.x %1, %0" : "=f" (pi) : "i" (0));
PIo2 = pi / 2;
PIo4 = pi / 4;
if (y == zero)
return signx == one ? y : __copysign(pi, signy);
if (x == zero)
return __copysign(PIo2, signy);
if (__isinf(x))
{
if (__isinf(y))
return __copysign(signx == one ? PIo4 : 3 * PIo4, signy);
else
return __copysign(signx == one ? zero : pi, signy);
}
if (__isinf(y))
return __copysign(PIo2, signy);
y = fabs(y);
if (x < 0.0)
/* X is negative. */
return __copysign(pi - atan(y / -x), signy);
return __copysign(atan(y / x), signy);
}
#else
#include <sysdeps/generic/atan2.c>
#endif
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