math/s_clog10l.c

   1 /* Compute complex base 10 logarithm.
   2    Copyright (C) 1997-2012 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <complex.h>
  21 #include <math.h>
  22 #include <math_private.h>
  23 #include <float.h>
  24
  25 /* log_10 (2).  */
  26 #define M_LOG10_2l 0.3010299956639811952137388947244930267682L
  27
  28 __complex__ long double
  29 __clog10l (__complex__ long double x)
  30 {
  31   __complex__ long double result;
  32   int rcls = fpclassify (__real__ x);
  33   int icls = fpclassify (__imag__ x);
  34
  35   if (__builtin_expect (rcls == FP_ZERO && icls == FP_ZERO, 0))
  36     {
  37       /* Real and imaginary part are 0.0.  */
  38       __imag__ result = signbit (__real__ x) ? M_PIl : 0.0;
  39       __imag__ result = __copysignl (__imag__ result, __imag__ x);
  40       /* Yes, the following line raises an exception.  */
  41       __real__ result = -1.0 / fabsl (__real__ x);
  42     }
  43   else if (__builtin_expect (rcls != FP_NAN && icls != FP_NAN, 1))
  44     {
  45       /* Neither real nor imaginary part is NaN.  */
  46       long double absx = fabsl (__real__ x), absy = fabsl (__imag__ x);
  47       long double d;
  48       int scale = 0;
  49
  50       if (absx > LDBL_MAX / 2.0L)
  51         {
  52           scale = -1;
  53           absx = __scalbnl (absx, scale);
  54           absy = (absy >= LDBL_MIN * 2.0L ? __scalbnl (absy, scale) : 0.0L);
  55         }
  56       else if (absy > LDBL_MAX / 2.0L)
  57         {
  58           scale = -1;
  59           absx = (absx >= LDBL_MIN * 2.0L ? __scalbnl (absx, scale) : 0.0L);
  60           absy = __scalbnl (absy, scale);
  61         }
  62       else if (absx < LDBL_MIN && absy < LDBL_MIN)
  63         {
  64           scale = LDBL_MANT_DIG;
  65           absx = __scalbnl (absx, scale);
  66           absy = __scalbnl (absy, scale);
  67         }
  68
  69       d = __ieee754_hypotl (absx, absy);
  70
  71       __real__ result = __ieee754_log10l (d) - scale * M_LOG10_2l;
  72       __imag__ result = M_LOG10El * __ieee754_atan2l (__imag__ x, __real__ x);
  73     }
  74   else
  75     {
  76       __imag__ result = __nanl ("");
  77       if (rcls == FP_INFINITE || icls == FP_INFINITE)
  78         /* Real or imaginary part is infinite.  */
  79         __real__ result = HUGE_VALL;
  80       else
  81         __real__ result = __nanl ("");
  82     }
  83
  84   return result;
  85 }
  86 weak_alias (__clog10l, clog10l)