aboutsummaryrefslogtreecommitdiff
path: root/math/s_clog10l.c
blob: 8481e45d4ecb7faccc4c6f63e113462216a172ff (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
/* Compute complex base 10 logarithm.
   Copyright (C) 1997-2015 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>

/* To avoid spurious underflows, use this definition to treat IBM long
   double as approximating an IEEE-style format.  */
#if LDBL_MANT_DIG == 106
# undef LDBL_EPSILON
# define LDBL_EPSILON 0x1p-106L
#endif

/* log_10 (2).  */
#define M_LOG10_2l 0.3010299956639811952137388947244930267682L

/* pi * log10 (e).  */
#define M_PI_LOG10El 1.364376353841841347485783625431355770210L

__complex__ long double
__clog10l (__complex__ long double x)
{
  __complex__ long double 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_LOG10El : 0.0;
      __imag__ result = __copysignl (__imag__ result, __imag__ x);
      /* Yes, the following line raises an exception.  */
      __real__ result = -1.0 / fabsl (__real__ x);
    }
  else if (__glibc_likely (rcls != FP_NAN && icls != FP_NAN))
    {
      /* Neither real nor imaginary part is NaN.  */
      long double absx = fabsl (__real__ x), absy = fabsl (__imag__ x);
      int scale = 0;

      if (absx < absy)
	{
	  long double t = absx;
	  absx = absy;
	  absy = t;
	}

      if (absx > LDBL_MAX / 2.0L)
	{
	  scale = -1;
	  absx = __scalbnl (absx, scale);
	  absy = (absy >= LDBL_MIN * 2.0L ? __scalbnl (absy, scale) : 0.0L);
	}
      else if (absx < LDBL_MIN && absy < LDBL_MIN)
	{
	  scale = LDBL_MANT_DIG;
	  absx = __scalbnl (absx, scale);
	  absy = __scalbnl (absy, scale);
	}

      if (absx == 1.0L && scale == 0)
	{
	  long double absy2 = absy * absy;
	  if (absy2 <= LDBL_MIN * 2.0L * M_LN10l)
	    {
	      long double force_underflow = absy2 * absy2;
	      __real__ result = absy2 * (M_LOG10El / 2.0);
	      math_force_eval (force_underflow);
	    }
	  else
	    __real__ result = __log1pl (absy2) * (M_LOG10El / 2.0L);
	}
      else if (absx > 1.0L && absx < 2.0L && absy < 1.0L && scale == 0)
	{
	  long double d2m1 = (absx - 1.0L) * (absx + 1.0L);
	  if (absy >= LDBL_EPSILON)
	    d2m1 += absy * absy;
	  __real__ result = __log1pl (d2m1) * (M_LOG10El / 2.0L);
	}
      else if (absx < 1.0L
	       && absx >= 0.75L
	       && absy < LDBL_EPSILON / 2.0L
	       && scale == 0)
	{
	  long double d2m1 = (absx - 1.0L) * (absx + 1.0L);
	  __real__ result = __log1pl (d2m1) * (M_LOG10El / 2.0L);
	}
      else if (absx < 1.0L && (absx >= 0.75L || absy >= 0.5L) && scale == 0)
	{
	  long double d2m1 = __x2y2m1l (absx, absy);
	  __real__ result = __log1pl (d2m1) * (M_LOG10El / 2.0L);
	}
      else
	{
	  long double d = __ieee754_hypotl (absx, absy);
	  __real__ result = __ieee754_log10l (d) - scale * M_LOG10_2l;
	}

      __imag__ result = M_LOG10El * __ieee754_atan2l (__imag__ x, __real__ x);
    }
  else
    {
      __imag__ result = __nanl ("");
      if (rcls == FP_INFINITE || icls == FP_INFINITE)
	/* Real or imaginary part is infinite.  */
	__real__ result = HUGE_VALL;
      else
	__real__ result = __nanl ("");
    }

  return result;
}
weak_alias (__clog10l, clog10l)