1/* Compute complex natural logarithm.
2 Copyright (C) 1997-2020 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 <https://www.gnu.org/licenses/>. */
19
20#include <complex.h>
21#include <math.h>
22#include <math_private.h>
23#include <math-underflow.h>
24#include <float.h>
25
26CFLOAT
27M_DECL_FUNC (__clog) (CFLOAT x)
28{
29 CFLOAT result;
30 int rcls = fpclassify (__real__ x);
31 int icls = fpclassify (__imag__ x);
32
33 if (__glibc_unlikely (rcls == FP_ZERO && icls == FP_ZERO))
34 {
35 /* Real and imaginary part are 0.0. */
36 __imag__ result = signbit (__real__ x) ? (FLOAT) M_MLIT (M_PI) : 0;
37 __imag__ result = M_COPYSIGN (__imag__ result, __imag__ x);
38 /* Yes, the following line raises an exception. */
39 __real__ result = -1 / M_FABS (__real__ x);
40 }
41 else if (__glibc_likely (rcls != FP_NAN && icls != FP_NAN))
42 {
43 /* Neither real nor imaginary part is NaN. */
44 FLOAT absx = M_FABS (__real__ x), absy = M_FABS (__imag__ x);
45 int scale = 0;
46
47 if (absx < absy)
48 {
49 FLOAT t = absx;
50 absx = absy;
51 absy = t;
52 }
53
54 if (absx > M_MAX / 2)
55 {
56 scale = -1;
57 absx = M_SCALBN (absx, scale);
58 absy = (absy >= M_MIN * 2 ? M_SCALBN (absy, scale) : 0);
59 }
60 else if (absx < M_MIN && absy < M_MIN)
61 {
62 scale = M_MANT_DIG;
63 absx = M_SCALBN (absx, scale);
64 absy = M_SCALBN (absy, scale);
65 }
66
67 if (absx == 1 && scale == 0)
68 {
69 __real__ result = M_LOG1P (absy * absy) / 2;
70 math_check_force_underflow_nonneg (__real__ result);
71 }
72 else if (absx > 1 && absx < 2 && absy < 1 && scale == 0)
73 {
74 FLOAT d2m1 = (absx - 1) * (absx + 1);
75 if (absy >= M_EPSILON)
76 d2m1 += absy * absy;
77 __real__ result = M_LOG1P (d2m1) / 2;
78 }
79 else if (absx < 1
80 && absx >= M_LIT (0.5)
81 && absy < M_EPSILON / 2
82 && scale == 0)
83 {
84 FLOAT d2m1 = (absx - 1) * (absx + 1);
85 __real__ result = M_LOG1P (d2m1) / 2;
86 }
87 else if (absx < 1
88 && absx >= M_LIT (0.5)
89 && scale == 0
90 && absx * absx + absy * absy >= M_LIT (0.5))
91 {
92 FLOAT d2m1 = M_SUF (__x2y2m1) (absx, absy);
93 __real__ result = M_LOG1P (d2m1) / 2;
94 }
95 else
96 {
97 FLOAT d = M_HYPOT (absx, absy);
98 __real__ result = M_LOG (d) - scale * (FLOAT) M_MLIT (M_LN2);
99 }
100
101 __imag__ result = M_ATAN2 (__imag__ x, __real__ x);
102 }
103 else
104 {
105 __imag__ result = M_NAN;
106 if (rcls == FP_INFINITE || icls == FP_INFINITE)
107 /* Real or imaginary part is infinite. */
108 __real__ result = M_HUGE_VAL;
109 else
110 __real__ result = M_NAN;
111 }
112
113 return result;
114}
115
116declare_mgen_alias (__clog, clog)
117