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d5602ceb | 1 | /* Complex hyperbolic tangent for float types. |
2b778ceb | 2 | Copyright (C) 1997-2021 Free Software Foundation, Inc. |
f6d3a72e | 3 | This file is part of the GNU C Library. |
f6d3a72e PM |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, see | |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
f6d3a72e PM |
18 | |
19 | #include <complex.h> | |
20 | #include <fenv.h> | |
21 | #include <math.h> | |
22 | #include <math_private.h> | |
8f5b00d3 | 23 | #include <math-underflow.h> |
f6d3a72e PM |
24 | #include <float.h> |
25 | ||
d5602ceb PM |
26 | CFLOAT |
27 | M_DECL_FUNC (__ctanh) (CFLOAT x) | |
f6d3a72e | 28 | { |
d5602ceb | 29 | CFLOAT res; |
f6d3a72e PM |
30 | |
31 | if (__glibc_unlikely (!isfinite (__real__ x) || !isfinite (__imag__ x))) | |
32 | { | |
33 | if (isinf (__real__ x)) | |
34 | { | |
d5602ceb PM |
35 | __real__ res = M_COPYSIGN (1, __real__ x); |
36 | if (isfinite (__imag__ x) && M_FABS (__imag__ x) > 1) | |
f6d3a72e | 37 | { |
d5602ceb PM |
38 | FLOAT sinix, cosix; |
39 | M_SINCOS (__imag__ x, &sinix, &cosix); | |
40 | __imag__ res = M_COPYSIGN (0, sinix * cosix); | |
f6d3a72e PM |
41 | } |
42 | else | |
d5602ceb | 43 | __imag__ res = M_COPYSIGN (0, __imag__ x); |
f6d3a72e | 44 | } |
d5602ceb | 45 | else if (__imag__ x == 0) |
f6d3a72e PM |
46 | { |
47 | res = x; | |
48 | } | |
49 | else | |
50 | { | |
d15e83c5 JM |
51 | if (__real__ x == 0) |
52 | __real__ res = __real__ x; | |
53 | else | |
54 | __real__ res = M_NAN; | |
d5602ceb | 55 | __imag__ res = M_NAN; |
f6d3a72e PM |
56 | |
57 | if (isinf (__imag__ x)) | |
58 | feraiseexcept (FE_INVALID); | |
59 | } | |
60 | } | |
61 | else | |
62 | { | |
d5602ceb PM |
63 | FLOAT sinix, cosix; |
64 | FLOAT den; | |
65 | const int t = (int) ((M_MAX_EXP - 1) * M_MLIT (M_LN2) / 2); | |
f6d3a72e PM |
66 | |
67 | /* tanh(x+iy) = (sinh(2x) + i*sin(2y))/(cosh(2x) + cos(2y)) | |
68 | = (sinh(x)*cosh(x) + i*sin(y)*cos(y))/(sinh(x)^2 + cos(y)^2). */ | |
69 | ||
d5602ceb | 70 | if (__glibc_likely (M_FABS (__imag__ x) > M_MIN)) |
f6d3a72e | 71 | { |
d5602ceb | 72 | M_SINCOS (__imag__ x, &sinix, &cosix); |
f6d3a72e PM |
73 | } |
74 | else | |
75 | { | |
76 | sinix = __imag__ x; | |
d5602ceb | 77 | cosix = 1; |
f6d3a72e PM |
78 | } |
79 | ||
d5602ceb | 80 | if (M_FABS (__real__ x) > t) |
f6d3a72e PM |
81 | { |
82 | /* Avoid intermediate overflow when the imaginary part of | |
83 | the result may be subnormal. Ignoring negligible terms, | |
84 | the real part is +/- 1, the imaginary part is | |
85 | sin(y)*cos(y)/sinh(x)^2 = 4*sin(y)*cos(y)/exp(2x). */ | |
d5602ceb | 86 | FLOAT exp_2t = M_EXP (2 * t); |
f6d3a72e | 87 | |
d5602ceb | 88 | __real__ res = M_COPYSIGN (1, __real__ x); |
f6d3a72e | 89 | __imag__ res = 4 * sinix * cosix; |
d5602ceb | 90 | __real__ x = M_FABS (__real__ x); |
f6d3a72e PM |
91 | __real__ x -= t; |
92 | __imag__ res /= exp_2t; | |
93 | if (__real__ x > t) | |
94 | { | |
95 | /* Underflow (original real part of x has absolute value | |
96 | > 2t). */ | |
97 | __imag__ res /= exp_2t; | |
98 | } | |
99 | else | |
d5602ceb | 100 | __imag__ res /= M_EXP (2 * __real__ x); |
f6d3a72e PM |
101 | } |
102 | else | |
103 | { | |
d5602ceb PM |
104 | FLOAT sinhrx, coshrx; |
105 | if (M_FABS (__real__ x) > M_MIN) | |
f6d3a72e | 106 | { |
d5602ceb PM |
107 | sinhrx = M_SINH (__real__ x); |
108 | coshrx = M_COSH (__real__ x); | |
f6d3a72e PM |
109 | } |
110 | else | |
111 | { | |
112 | sinhrx = __real__ x; | |
d5602ceb | 113 | coshrx = 1; |
f6d3a72e PM |
114 | } |
115 | ||
d5602ceb | 116 | if (M_FABS (sinhrx) > M_FABS (cosix) * M_EPSILON) |
f6d3a72e PM |
117 | den = sinhrx * sinhrx + cosix * cosix; |
118 | else | |
119 | den = cosix * cosix; | |
120 | __real__ res = sinhrx * coshrx / den; | |
121 | __imag__ res = sinix * cosix / den; | |
122 | } | |
123 | math_check_force_underflow_complex (res); | |
124 | } | |
125 | ||
126 | return res; | |
127 | } | |
d5602ceb PM |
128 | |
129 | declare_mgen_alias (__ctanh, ctanh) |