1 /* Compute complex natural logarithm.
2 Copyright (C) 1997-2018 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 __complex128
clogq(__complex128 x)23 clogq (__complex128 x)
24 {
25 __complex128 result;
26 int rcls = fpclassifyq (__real__ x);
27 int icls = fpclassifyq (__imag__ x);
28
29 if (__glibc_unlikely (rcls == QUADFP_ZERO && icls == QUADFP_ZERO))
30 {
31 /* Real and imaginary part are 0.0. */
32 __imag__ result = signbitq (__real__ x) ? (__float128) M_PIq : 0;
33 __imag__ result = copysignq (__imag__ result, __imag__ x);
34 /* Yes, the following line raises an exception. */
35 __real__ result = -1 / fabsq (__real__ x);
36 }
37 else if (__glibc_likely (rcls != QUADFP_NAN && icls != QUADFP_NAN))
38 {
39 /* Neither real nor imaginary part is NaN. */
40 __float128 absx = fabsq (__real__ x), absy = fabsq (__imag__ x);
41 int scale = 0;
42
43 if (absx < absy)
44 {
45 __float128 t = absx;
46 absx = absy;
47 absy = t;
48 }
49
50 if (absx > FLT128_MAX / 2)
51 {
52 scale = -1;
53 absx = scalbnq (absx, scale);
54 absy = (absy >= FLT128_MIN * 2 ? scalbnq (absy, scale) : 0);
55 }
56 else if (absx < FLT128_MIN && absy < FLT128_MIN)
57 {
58 scale = FLT128_MANT_DIG;
59 absx = scalbnq (absx, scale);
60 absy = scalbnq (absy, scale);
61 }
62
63 if (absx == 1 && scale == 0)
64 {
65 __real__ result = log1pq (absy * absy) / 2;
66 math_check_force_underflow_nonneg (__real__ result);
67 }
68 else if (absx > 1 && absx < 2 && absy < 1 && scale == 0)
69 {
70 __float128 d2m1 = (absx - 1) * (absx + 1);
71 if (absy >= FLT128_EPSILON)
72 d2m1 += absy * absy;
73 __real__ result = log1pq (d2m1) / 2;
74 }
75 else if (absx < 1
76 && absx >= 0.5Q
77 && absy < FLT128_EPSILON / 2
78 && scale == 0)
79 {
80 __float128 d2m1 = (absx - 1) * (absx + 1);
81 __real__ result = log1pq (d2m1) / 2;
82 }
83 else if (absx < 1
84 && absx >= 0.5Q
85 && scale == 0
86 && absx * absx + absy * absy >= 0.5Q)
87 {
88 __float128 d2m1 = __quadmath_x2y2m1q (absx, absy);
89 __real__ result = log1pq (d2m1) / 2;
90 }
91 else
92 {
93 __float128 d = hypotq (absx, absy);
94 __real__ result = logq (d) - scale * (__float128) M_LN2q;
95 }
96
97 __imag__ result = atan2q (__imag__ x, __real__ x);
98 }
99 else
100 {
101 __imag__ result = nanq ("");
102 if (rcls == QUADFP_INFINITE || icls == QUADFP_INFINITE)
103 /* Real or imaginary part is infinite. */
104 __real__ result = HUGE_VALQ;
105 else
106 __real__ result = nanq ("");
107 }
108
109 return result;
110 }
111