b2dad0e372
2000-04-21 Benjamin Kosnik <bkoz@redhat.com> * libstdc++-v3: New directory. From-SVN: r33317
111 lines
2.9 KiB
C
111 lines
2.9 KiB
C
/* Complex square root of double value. */
|
|
|
|
/* Copyright (C) 1997-1999 Free Software Foundation, Inc.
|
|
|
|
This file is part of the GNU ISO C++ Library. This library is free
|
|
software; you can redistribute it and/or modify it under the
|
|
terms of the GNU General Public License as published by the
|
|
Free Software Foundation; either version 2, or (at your option)
|
|
any later version.
|
|
|
|
This 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 General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License along
|
|
with this library; see the file COPYING. If not, write to the Free
|
|
Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
|
|
USA.
|
|
|
|
As a special exception, you may use this file as part of a free software
|
|
library without restriction. Specifically, if other files instantiate
|
|
templates or use macros or inline functions from this file, or you compile
|
|
this file and link it with other files to produce an executable, this
|
|
file does not by itself cause the resulting executable to be covered by
|
|
the GNU General Public License. This exception does not however
|
|
invalidate any other reasons why the executable file might be covered by
|
|
the GNU General Public License. */
|
|
|
|
|
|
#include <math.h>
|
|
#include "mathconf.h"
|
|
|
|
|
|
__complex__ double
|
|
csqrt (__complex__ double x)
|
|
{
|
|
__complex__ double res;
|
|
|
|
if (!FINITE_P (__real__ x) || !FINITE_P (__imag__ x))
|
|
{
|
|
if (INFINITE_P (__imag__ x))
|
|
{
|
|
__real__ res = HUGE_VAL;
|
|
__imag__ res = __imag__ x;
|
|
}
|
|
else if (INFINITE_P (__real__ x))
|
|
{
|
|
if (__real__ x < 0.0)
|
|
{
|
|
__real__ res = __imag__ x != __imag__ x ? NAN : 0;
|
|
__imag__ res = copysign (HUGE_VAL, __imag__ x);
|
|
}
|
|
else
|
|
{
|
|
__real__ res = __real__ x;
|
|
__imag__ res = (__imag__ x != __imag__ x
|
|
? NAN : copysign (0.0, __imag__ x));
|
|
}
|
|
}
|
|
else
|
|
{
|
|
__real__ res = NAN;
|
|
__imag__ res = NAN;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
if (__imag__ x == 0.0)
|
|
{
|
|
if (__real__ x < 0.0)
|
|
{
|
|
__real__ res = 0.0;
|
|
__imag__ res = copysign (sqrt (-__real__ x), __imag__ x);
|
|
}
|
|
else
|
|
{
|
|
__real__ res = fabs (sqrt (__real__ x));
|
|
__imag__ res = copysign (0.0, __imag__ x);
|
|
}
|
|
}
|
|
else if (__real__ x == 0.0)
|
|
{
|
|
double r = sqrt (0.5 * fabs (__imag__ x));
|
|
|
|
__real__ res = copysign (r, __imag__ x);
|
|
__imag__ res = r;
|
|
}
|
|
else
|
|
{
|
|
__complex__ double q;
|
|
double t, r;
|
|
|
|
if (fabs (__imag__ x) < 2.0e-4 * fabs (__real__ x))
|
|
t = 0.25 * __imag__ x * (__imag__ x / __real__ x);
|
|
else
|
|
t = 0.5 * (hypot (__real__ x, __imag__ x) - __real__ x);
|
|
|
|
r = sqrt (t);
|
|
|
|
__real__ q = __imag__ x / (2.0 * r);
|
|
__imag__ q = r;
|
|
|
|
/* Heron iteration in complex arithmetic. */
|
|
res = 0.5 * (q + q / x);
|
|
}
|
|
}
|
|
|
|
return res;
|
|
}
|