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[glibc.git] / math / s_catan.c
blob1a458a3833003713d7590d185820ea4c11611bc8
1 /* Return arc tangent of complex double value.
2 Copyright (C) 1997, 2011 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>
23 #include <math_private.h>
26 __complex__ double
27 __catan (__complex__ double x)
29 __complex__ double res;
30 int rcls = fpclassify (__real__ x);
31 int icls = fpclassify (__imag__ x);
33 if (__builtin_expect (rcls <= FP_INFINITE || icls <= FP_INFINITE, 0))
35 if (rcls == FP_INFINITE)
37 __real__ res = __copysign (M_PI_2, __real__ x);
38 __imag__ res = __copysign (0.0, __imag__ x);
40 else if (icls == FP_INFINITE)
42 if (rcls >= FP_ZERO)
43 __real__ res = __copysign (M_PI_2, __real__ x);
44 else
45 __real__ res = __nan ("");
46 __imag__ res = __copysign (0.0, __imag__ x);
48 else if (icls == FP_ZERO || icls == FP_INFINITE)
50 __real__ res = __nan ("");
51 __imag__ res = __copysign (0.0, __imag__ x);
53 else
55 __real__ res = __nan ("");
56 __imag__ res = __nan ("");
59 else if (__builtin_expect (rcls == FP_ZERO && icls == FP_ZERO, 0))
61 res = x;
63 else
65 double r2, num, den;
67 r2 = __real__ x * __real__ x;
69 den = 1 - r2 - __imag__ x * __imag__ x;
71 __real__ res = 0.5 * __ieee754_atan2 (2.0 * __real__ x, den);
73 num = __imag__ x + 1.0;
74 num = r2 + num * num;
76 den = __imag__ x - 1.0;
77 den = r2 + den * den;
79 __imag__ res = 0.25 * __ieee754_log (num / den);
82 return res;
84 weak_alias (__catan, catan)
85 #ifdef NO_LONG_DOUBLE
86 strong_alias (__catan, __catanl)
87 weak_alias (__catan, catanl)
88 #endif