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86 lines
2.6 KiB
C
86 lines
2.6 KiB
C
/* Compute complex base 10 logarithm.
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Copyright (C) 1997-2012 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <complex.h>
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#include <math.h>
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#include <math_private.h>
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#include <float.h>
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/* log_10 (2). */
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#define M_LOG10_2 0.3010299956639811952137388947244930267682
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__complex__ double
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__clog10 (__complex__ double x)
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{
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__complex__ double result;
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int rcls = fpclassify (__real__ x);
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int icls = fpclassify (__imag__ x);
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if (__builtin_expect (rcls == FP_ZERO && icls == FP_ZERO, 0))
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{
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/* Real and imaginary part are 0.0. */
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__imag__ result = signbit (__real__ x) ? M_PI : 0.0;
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__imag__ result = __copysign (__imag__ result, __imag__ x);
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/* Yes, the following line raises an exception. */
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__real__ result = -1.0 / fabs (__real__ x);
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}
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else if (__builtin_expect (rcls != FP_NAN && icls != FP_NAN, 1))
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{
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/* Neither real nor imaginary part is NaN. */
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double d;
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int scale = 0;
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if (fabs (__real__ x) > DBL_MAX / 2.0
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|| fabs (__imag__ x) > DBL_MAX / 2.0)
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{
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scale = -1;
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__real__ x = __scalbn (__real__ x, scale);
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__imag__ x = __scalbn (__imag__ x, scale);
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}
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else if (fabs (__real__ x) < DBL_MIN
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&& fabs (__imag__ x) < DBL_MIN)
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{
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scale = DBL_MANT_DIG;
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__real__ x = __scalbn (__real__ x, scale);
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__imag__ x = __scalbn (__imag__ x, scale);
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}
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d = __ieee754_hypot (__real__ x, __imag__ x);
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__real__ result = __ieee754_log10 (d) - scale * M_LOG10_2;
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__imag__ result = M_LOG10E * __ieee754_atan2 (__imag__ x, __real__ x);
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}
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else
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{
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__imag__ result = __nan ("");
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if (rcls == FP_INFINITE || icls == FP_INFINITE)
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/* Real or imaginary part is infinite. */
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__real__ result = HUGE_VAL;
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else
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__real__ result = __nan ("");
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}
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return result;
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}
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weak_alias (__clog10, clog10)
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#ifdef NO_LONG_DOUBLE
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strong_alias (__clog10, __clog10l)
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weak_alias (__clog10, clog10l)
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#endif
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