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glibc/math/s_clog10f.c
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/* Compute complex base 10 logarithm. | |
Copyright (C) 1997-2014 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_2f 0.3010299956639811952137388947244930267682f | |
/* pi * log10 (e). */ | |
#define M_PI_LOG10Ef 1.364376353841841347485783625431355770210f | |
__complex__ float | |
__clog10f (__complex__ float x) | |
{ | |
__complex__ float result; | |
int rcls = fpclassify (__real__ x); | |
int icls = fpclassify (__imag__ x); | |
if (__glibc_unlikely (rcls == FP_ZERO && icls == FP_ZERO)) | |
{ | |
/* Real and imaginary part are 0.0. */ | |
__imag__ result = signbit (__real__ x) ? M_PI_LOG10Ef : 0.0; | |
__imag__ result = __copysignf (__imag__ result, __imag__ x); | |
/* Yes, the following line raises an exception. */ | |
__real__ result = -1.0 / fabsf (__real__ x); | |
} | |
else if (__glibc_likely (rcls != FP_NAN && icls != FP_NAN)) | |
{ | |
/* Neither real nor imaginary part is NaN. */ | |
float absx = fabsf (__real__ x), absy = fabsf (__imag__ x); | |
int scale = 0; | |
if (absx < absy) | |
{ | |
float t = absx; | |
absx = absy; | |
absy = t; | |
} | |
if (absx > FLT_MAX / 2.0f) | |
{ | |
scale = -1; | |
absx = __scalbnf (absx, scale); | |
absy = (absy >= FLT_MIN * 2.0f ? __scalbnf (absy, scale) : 0.0f); | |
} | |
else if (absx < FLT_MIN && absy < FLT_MIN) | |
{ | |
scale = FLT_MANT_DIG; | |
absx = __scalbnf (absx, scale); | |
absy = __scalbnf (absy, scale); | |
} | |
if (absx == 1.0f && scale == 0) | |
{ | |
float absy2 = absy * absy; | |
if (absy2 <= FLT_MIN * 2.0f * (float) M_LN10) | |
{ | |
#if __FLT_EVAL_METHOD__ == 0 | |
__real__ result | |
= (absy2 / 2.0f - absy2 * absy2 / 4.0f) * (float) M_LOG10E; | |
#else | |
volatile float force_underflow = absy2 * absy2 / 4.0f; | |
__real__ result | |
= (absy2 / 2.0f - force_underflow) * (float) M_LOG10E; | |
#endif | |
} | |
else | |
__real__ result = __log1pf (absy2) * ((float) M_LOG10E / 2.0f); | |
} | |
else if (absx > 1.0f && absx < 2.0f && absy < 1.0f && scale == 0) | |
{ | |
float d2m1 = (absx - 1.0f) * (absx + 1.0f); | |
if (absy >= FLT_EPSILON) | |
d2m1 += absy * absy; | |
__real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f); | |
} | |
else if (absx < 1.0f | |
&& absx >= 0.75f | |
&& absy < FLT_EPSILON / 2.0f | |
&& scale == 0) | |
{ | |
float d2m1 = (absx - 1.0f) * (absx + 1.0f); | |
__real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f); | |
} | |
else if (absx < 1.0f && (absx >= 0.75f || absy >= 0.5f) && scale == 0) | |
{ | |
float d2m1 = __x2y2m1f (absx, absy); | |
__real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f); | |
} | |
else | |
{ | |
float d = __ieee754_hypotf (absx, absy); | |
__real__ result = __ieee754_log10f (d) - scale * M_LOG10_2f; | |
} | |
__imag__ result = M_LOG10E * __ieee754_atan2f (__imag__ x, __real__ x); | |
} | |
else | |
{ | |
__imag__ result = __nanf (""); | |
if (rcls == FP_INFINITE || icls == FP_INFINITE) | |
/* Real or imaginary part is infinite. */ | |
__real__ result = HUGE_VALF; | |
else | |
__real__ result = __nanf (""); | |
} | |
return result; | |
} | |
#ifndef __clog10f | |
weak_alias (__clog10f, clog10f) | |
#endif |