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/* Complex square root of double value.
Copyright (C) 1997, 1998 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Based on an algorithm by Stephen L. Moshier <moshier@world.std.com>.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <complex.h>
#include <math.h>
#include "math_private.h"
__complex__ double
__csqrt (__complex__ double x)
{
__complex__ double res;
int rcls = fpclassify (__real__ x);
int icls = fpclassify (__imag__ x);
if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
{
if (icls == FP_INFINITE)
{
__real__ res = HUGE_VAL;
__imag__ res = __imag__ x;
}
else if (rcls == FP_INFINITE)
{
if (__real__ x < 0.0)
{
__real__ res = icls == FP_NAN ? __nan ("") : 0;
__imag__ res = __copysign (HUGE_VAL, __imag__ x);
}
else
{
__real__ res = __real__ x;
__imag__ res = (icls == FP_NAN
? __nan ("") : __copysign (0.0, __imag__ x));
}
}
else
{
__real__ res = __nan ("");
__imag__ res = __nan ("");
}
}
else
{
if (icls == FP_ZERO)
{
if (__real__ x < 0.0)
{
__real__ res = 0.0;
__imag__ res = __copysign (__ieee754_sqrt (-__real__ x),
__imag__ x);
}
else
{
__real__ res = fabs (__ieee754_sqrt (__real__ x));
__imag__ res = __copysign (0.0, __imag__ x);
}
}
else if (rcls == FP_ZERO)
{
double r = __ieee754_sqrt (0.5 * fabs (__imag__ x));
__real__ res = __copysign (r, __imag__ x);
__imag__ res = r;
}
else
{
double d, r, s;
d = __ieee754_hypot (__real__ x, __imag__ x);
/* Use the identity 2 Re res Im res = Im x
to avoid cancellation error in d +/- Re x. */
if (__real__ x > 0)
{
r = __ieee754_sqrt (0.5 * d + 0.5 * __real__ x);
s = (0.5 * __imag__ x) / r;
}
else
{
s = __ieee754_sqrt (0.5 * d - 0.5 * __real__ x);
r = fabs ((0.5 * __imag__ x) / s);
}
__real__ res = r;
__imag__ res = __copysign (s, __imag__ x);
}
}
return res;
}
weak_alias (__csqrt, csqrt)
#ifdef NO_LONG_DOUBLE
strong_alias (__csqrt, __csqrtl)
weak_alias (__csqrt, csqrtl)
#endif
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