1 | /* Compute complex base 10 logarithm. |
2 | Copyright (C) 1997-2016 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_2f 0.3010299956639811952137388947244930267682f |
27 | |
28 | /* pi * log10 (e). */ |
29 | #define M_PI_LOG10Ef 1.364376353841841347485783625431355770210f |
30 | |
31 | __complex__ float |
32 | __clog10f (__complex__ float x) |
33 | { |
34 | __complex__ float result; |
35 | int rcls = fpclassify (__real__ x); |
36 | int icls = fpclassify (__imag__ x); |
37 | |
38 | if (__glibc_unlikely (rcls == FP_ZERO && icls == FP_ZERO)) |
39 | { |
40 | /* Real and imaginary part are 0.0. */ |
41 | __imag__ result = signbit (__real__ x) ? M_PI_LOG10Ef : 0.0; |
42 | __imag__ result = __copysignf (__imag__ result, __imag__ x); |
43 | /* Yes, the following line raises an exception. */ |
44 | __real__ result = -1.0 / fabsf (__real__ x); |
45 | } |
46 | else if (__glibc_likely (rcls != FP_NAN && icls != FP_NAN)) |
47 | { |
48 | /* Neither real nor imaginary part is NaN. */ |
49 | float absx = fabsf (__real__ x), absy = fabsf (__imag__ x); |
50 | int scale = 0; |
51 | |
52 | if (absx < absy) |
53 | { |
54 | float t = absx; |
55 | absx = absy; |
56 | absy = t; |
57 | } |
58 | |
59 | if (absx > FLT_MAX / 2.0f) |
60 | { |
61 | scale = -1; |
62 | absx = __scalbnf (absx, scale); |
63 | absy = (absy >= FLT_MIN * 2.0f ? __scalbnf (absy, scale) : 0.0f); |
64 | } |
65 | else if (absx < FLT_MIN && absy < FLT_MIN) |
66 | { |
67 | scale = FLT_MANT_DIG; |
68 | absx = __scalbnf (absx, scale); |
69 | absy = __scalbnf (absy, scale); |
70 | } |
71 | |
72 | if (absx == 1.0f && scale == 0) |
73 | { |
74 | __real__ result = __log1pf (absy * absy) * ((float) M_LOG10E / 2.0f); |
75 | math_check_force_underflow_nonneg (__real__ result); |
76 | } |
77 | else if (absx > 1.0f && absx < 2.0f && absy < 1.0f && scale == 0) |
78 | { |
79 | float d2m1 = (absx - 1.0f) * (absx + 1.0f); |
80 | if (absy >= FLT_EPSILON) |
81 | d2m1 += absy * absy; |
82 | __real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f); |
83 | } |
84 | else if (absx < 1.0f |
85 | && absx >= 0.5f |
86 | && absy < FLT_EPSILON / 2.0f |
87 | && scale == 0) |
88 | { |
89 | float d2m1 = (absx - 1.0f) * (absx + 1.0f); |
90 | __real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f); |
91 | } |
92 | else if (absx < 1.0f |
93 | && absx >= 0.5f |
94 | && scale == 0 |
95 | && absx * absx + absy * absy >= 0.5f) |
96 | { |
97 | float d2m1 = __x2y2m1f (absx, absy); |
98 | __real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f); |
99 | } |
100 | else |
101 | { |
102 | float d = __ieee754_hypotf (absx, absy); |
103 | __real__ result = __ieee754_log10f (d) - scale * M_LOG10_2f; |
104 | } |
105 | |
106 | __imag__ result = M_LOG10E * __ieee754_atan2f (__imag__ x, __real__ x); |
107 | } |
108 | else |
109 | { |
110 | __imag__ result = __nanf ("" ); |
111 | if (rcls == FP_INFINITE || icls == FP_INFINITE) |
112 | /* Real or imaginary part is infinite. */ |
113 | __real__ result = HUGE_VALF; |
114 | else |
115 | __real__ result = __nanf ("" ); |
116 | } |
117 | |
118 | return result; |
119 | } |
120 | #ifndef __clog10f |
121 | weak_alias (__clog10f, clog10f) |
122 | #endif |
123 | |