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/* Compute complex base 10 logarithm.
Copyright (C) 1997-2012 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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 Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <complex.h>
#include <math.h>
#include <math_private.h>
#include <float.h>
/* log_10 (2). */
#define M_LOG10_2 0.3010299956639811952137388947244930267682
__complex__ double
__clog10 (__complex__ double x)
{
__complex__ double result;
int rcls = fpclassify (__real__ x);
int icls = fpclassify (__imag__ x);
if (__builtin_expect (rcls == FP_ZERO && icls == FP_ZERO, 0))
{
/* Real and imaginary part are 0.0. */
__imag__ result = signbit (__real__ x) ? M_PI : 0.0;
__imag__ result = __copysign (__imag__ result, __imag__ x);
/* Yes, the following line raises an exception. */
__real__ result = -1.0 / fabs (__real__ x);
}
else if (__builtin_expect (rcls != FP_NAN && icls != FP_NAN, 1))
{
/* Neither real nor imaginary part is NaN. */
double absx = fabs (__real__ x), absy = fabs (__imag__ x);
int scale = 0;
if (absx < absy)
{
double t = absx;
absx = absy;
absy = t;
}
if (absx > DBL_MAX / 2.0)
{
scale = -1;
absx = __scalbn (absx, scale);
absy = (absy >= DBL_MIN * 2.0 ? __scalbn (absy, scale) : 0.0);
}
else if (absx < DBL_MIN && absy < DBL_MIN)
{
scale = DBL_MANT_DIG;
absx = __scalbn (absx, scale);
absy = __scalbn (absy, scale);
}
if (absx == 1.0 && scale == 0)
{
double absy2 = absy * absy;
if (absy2 <= DBL_MIN * 2.0 * M_LN10)
{
#if __FLT_EVAL_METHOD__ == 0
__real__ result = (absy2 / 2.0 - absy2 * absy2 / 4.0) * M_LOG10E;
#else
volatile double force_underflow = absy2 * absy2 / 4.0;
__real__ result = (absy2 / 2.0 - force_underflow) * M_LOG10E;
#endif
}
else
__real__ result = __log1p (absy2) * (M_LOG10E / 2.0);
}
else if (absx > 1.0 && absx < 2.0 && absy < 1.0 && scale == 0)
{
double d2m1 = (absx - 1.0) * (absx + 1.0);
if (absy >= DBL_EPSILON)
d2m1 += absy * absy;
__real__ result = __log1p (d2m1) * (M_LOG10E / 2.0);
}
else
{
double d = __ieee754_hypot (absx, absy);
__real__ result = __ieee754_log10 (d) - scale * M_LOG10_2;
}
__imag__ result = M_LOG10E * __ieee754_atan2 (__imag__ x, __real__ x);
}
else
{
__imag__ result = __nan ("");
if (rcls == FP_INFINITE || icls == FP_INFINITE)
/* Real or imaginary part is infinite. */
__real__ result = HUGE_VAL;
else
__real__ result = __nan ("");
}
return result;
}
weak_alias (__clog10, clog10)
#ifdef NO_LONG_DOUBLE
strong_alias (__clog10, __clog10l)
weak_alias (__clog10, clog10l)
#endif
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