[BZ #4276]
[glibc/history.git] / math / s_catan.c
blob1d0673ad6a38df7b1cfca3d29c4bd16cb3ea7839
1 /* Return arc tangent of complex double value.
2 Copyright (C) 1997 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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.
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.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, write to the Free
18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
19 02111-1307 USA. */
21 #include <complex.h>
22 #include <math.h>
24 #include "math_private.h"
27 __complex__ double
28 __catan (__complex__ double x)
30 __complex__ double res;
31 int rcls = fpclassify (__real__ x);
32 int icls = fpclassify (__imag__ x);
34 if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
36 if (rcls == FP_INFINITE)
38 __real__ res = __copysign (M_PI_2, __real__ x);
39 __imag__ res = __copysign (0.0, __imag__ x);
41 else if (icls == FP_INFINITE)
43 if (rcls >= FP_ZERO)
44 __real__ res = __copysign (M_PI_2, __real__ x);
45 else
46 __real__ res = __nan ("");
47 __imag__ res = __copysign (0.0, __imag__ x);
49 else if (icls == FP_ZERO || icls == FP_INFINITE)
51 __real__ res = __nan ("");
52 __imag__ res = __copysign (0.0, __imag__ x);
54 else
56 __real__ res = __nan ("");
57 __imag__ res = __nan ("");
60 else if (rcls == FP_ZERO && icls == FP_ZERO)
62 res = x;
64 else
66 double r2, num, den;
68 r2 = __real__ x * __real__ x;
70 den = 1 - r2 - __imag__ x * __imag__ x;
72 __real__ res = 0.5 * __ieee754_atan2 (2.0 * __real__ x, den);
74 num = __imag__ x + 1.0;
75 num = r2 + num * num;
77 den = __imag__ x - 1.0;
78 den = r2 + den * den;
80 __imag__ res = 0.25 * __ieee754_log (num / den);
83 return res;
85 weak_alias (__catan, catan)
86 #ifdef NO_LONG_DOUBLE
87 strong_alias (__catan, __catanl)
88 weak_alias (__catan, catanl)
89 #endif