| /* Compute complex base 10 logarithm. |
| Copyright (C) 1997-2018 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 LOG10_2 M_LIT (0.3010299956639811952137388947244930267682) |
| |
| /* pi * log10 (e). */ |
| #define PI_LOG10E M_LIT (1.364376353841841347485783625431355770210) |
| |
| CFLOAT |
| M_DECL_FUNC (__clog10) (CFLOAT x) |
| { |
| CFLOAT 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) ? PI_LOG10E : 0; |
| __imag__ result = M_COPYSIGN (__imag__ result, __imag__ x); |
| /* Yes, the following line raises an exception. */ |
| __real__ result = -1 / M_FABS (__real__ x); |
| } |
| else if (__glibc_likely (rcls != FP_NAN && icls != FP_NAN)) |
| { |
| /* Neither real nor imaginary part is NaN. */ |
| FLOAT absx = M_FABS (__real__ x), absy = M_FABS (__imag__ x); |
| int scale = 0; |
| |
| if (absx < absy) |
| { |
| FLOAT t = absx; |
| absx = absy; |
| absy = t; |
| } |
| |
| if (absx > M_MAX / 2) |
| { |
| scale = -1; |
| absx = M_SCALBN (absx, scale); |
| absy = (absy >= M_MIN * 2 ? M_SCALBN (absy, scale) : 0); |
| } |
| else if (absx < M_MIN && absy < M_MIN) |
| { |
| scale = M_MANT_DIG; |
| absx = M_SCALBN (absx, scale); |
| absy = M_SCALBN (absy, scale); |
| } |
| |
| if (absx == 1 && scale == 0) |
| { |
| __real__ result = (M_LOG1P (absy * absy) |
| * ((FLOAT) M_MLIT (M_LOG10E) / 2)); |
| math_check_force_underflow_nonneg (__real__ result); |
| } |
| else if (absx > 1 && absx < 2 && absy < 1 && scale == 0) |
| { |
| FLOAT d2m1 = (absx - 1) * (absx + 1); |
| if (absy >= M_EPSILON) |
| d2m1 += absy * absy; |
| __real__ result = M_LOG1P (d2m1) * ((FLOAT) M_MLIT (M_LOG10E) / 2); |
| } |
| else if (absx < 1 |
| && absx >= M_LIT (0.5) |
| && absy < M_EPSILON / 2 |
| && scale == 0) |
| { |
| FLOAT d2m1 = (absx - 1) * (absx + 1); |
| __real__ result = M_LOG1P (d2m1) * ((FLOAT) M_MLIT (M_LOG10E) / 2); |
| } |
| else if (absx < 1 |
| && absx >= M_LIT (0.5) |
| && scale == 0 |
| && absx * absx + absy * absy >= M_LIT (0.5)) |
| { |
| FLOAT d2m1 = M_SUF (__x2y2m1) (absx, absy); |
| __real__ result = M_LOG1P (d2m1) * ((FLOAT) M_MLIT (M_LOG10E) / 2); |
| } |
| else |
| { |
| FLOAT d = M_HYPOT (absx, absy); |
| __real__ result = M_SUF (__ieee754_log10) (d) - scale * LOG10_2; |
| } |
| |
| __imag__ result = M_MLIT (M_LOG10E) * M_ATAN2 (__imag__ x, __real__ x); |
| } |
| else |
| { |
| __imag__ result = M_NAN; |
| if (rcls == FP_INFINITE || icls == FP_INFINITE) |
| /* Real or imaginary part is infinite. */ |
| __real__ result = M_HUGE_VAL; |
| else |
| __real__ result = M_NAN; |
| } |
| |
| return result; |
| } |
| |
| declare_mgen_alias (__clog10, clog10) |