1 /* Compute complex base 10 logarithm for complex __float128.
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 "quadmath-imp.h"
21
22
23 /* log_10 (2). */
24 #define M_LOG10_2q 0.3010299956639811952137388947244930267682Q
25
26
27 __complex128
clog10q(__complex128 x)28 clog10q (__complex128 x)
29 {
30 __complex128 result;
31 int rcls = fpclassifyq (__real__ x);
32 int icls = fpclassifyq (__imag__ x);
33
34 if (__builtin_expect (rcls == QUADFP_ZERO && icls == QUADFP_ZERO, 0))
35 {
36 /* Real and imaginary part are 0.0. */
37 __imag__ result = signbitq (__real__ x) ? M_PIq : 0.0Q;
38 __imag__ result = copysignq (__imag__ result, __imag__ x);
39 /* Yes, the following line raises an exception. */
40 __real__ result = -1.0Q / fabsq (__real__ x);
41 }
42 else if (__builtin_expect (rcls != QUADFP_NAN && icls != QUADFP_NAN, 1))
43 {
44 /* Neither real nor imaginary part is NaN. */
45 __float128 absx = fabsq (__real__ x), absy = fabsq (__imag__ x);
46 int scale = 0;
47
48 if (absx < absy)
49 {
50 __float128 t = absx;
51 absx = absy;
52 absy = t;
53 }
54
55 if (absx > FLT128_MAX / 2.0Q)
56 {
57 scale = -1;
58 absx = scalbnq (absx, scale);
59 absy = (absy >= FLT128_MIN * 2.0Q ? scalbnq (absy, scale) : 0.0Q);
60 }
61 else if (absx < FLT128_MIN && absy < FLT128_MIN)
62 {
63 scale = FLT128_MANT_DIG;
64 absx = scalbnq (absx, scale);
65 absy = scalbnq (absy, scale);
66 }
67
68 if (absx == 1.0Q && scale == 0)
69 {
70 __float128 absy2 = absy * absy;
71 if (absy2 <= FLT128_MIN * 2.0Q * M_LN10q)
72 __real__ result
73 = (absy2 / 2.0Q - absy2 * absy2 / 4.0Q) * M_LOG10Eq;
74 else
75 __real__ result = log1pq (absy2) * (M_LOG10Eq / 2.0Q);
76 }
77 else if (absx > 1.0Q && absx < 2.0Q && absy < 1.0Q && scale == 0)
78 {
79 __float128 d2m1 = (absx - 1.0Q) * (absx + 1.0Q);
80 if (absy >= FLT128_EPSILON)
81 d2m1 += absy * absy;
82 __real__ result = log1pq (d2m1) * (M_LOG10Eq / 2.0Q);
83 }
84 else if (absx < 1.0Q
85 && absx >= 0.75Q
86 && absy < FLT128_EPSILON / 2.0Q
87 && scale == 0)
88 {
89 __float128 d2m1 = (absx - 1.0Q) * (absx + 1.0Q);
90 __real__ result = log1pq (d2m1) * (M_LOG10Eq / 2.0Q);
91 }
92 else if (absx < 1.0Q && (absx >= 0.75Q || absy >= 0.5Q) && scale == 0)
93 {
94 __float128 d2m1 = __quadmath_x2y2m1q (absx, absy);
95 __real__ result = log1pq (d2m1) * (M_LOG10Eq / 2.0Q);
96 }
97 else
98 {
99 __float128 d = hypotq (absx, absy);
100 __real__ result = log10q (d) - scale * M_LOG10_2q;
101 }
102
103 __imag__ result = M_LOG10Eq * atan2q (__imag__ x, __real__ x);
104 }
105 else
106 {
107 __imag__ result = nanq ("");
108 if (rcls == QUADFP_INFINITE || icls == QUADFP_INFINITE)
109 /* Real or imaginary part is infinite. */
110 __real__ result = HUGE_VALQ;
111 else
112 __real__ result = nanq ("");
113 }
114
115 return result;
116 }
117