| 1 | /* Return arc tangent of complex double value. |
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| 2 | Copyright (C) 1997 Free Software Foundation, Inc. |
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| 3 | This file is part of the GNU C Library. |
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| 4 | Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997. |
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| 5 | |
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| 6 | The GNU C Library is free software; you can redistribute it and/or |
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| 7 | modify it under the terms of the GNU Lesser General Public |
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| 8 | License as published by the Free Software Foundation; either |
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| 9 | version 2.1 of the License, or (at your option) any later version. |
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| 10 | |
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| 11 | The GNU C Library is distributed in the hope that it will be useful, |
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| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 14 | Lesser General Public License for more details. |
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| 15 | |
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| 16 | You should have received a copy of the GNU Lesser General Public |
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| 17 | License along with the GNU C Library; if not, write to the Free |
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| 18 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
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| 19 | 02111-1307 USA. */ |
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| 20 | |
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| 21 | #include <complex.h> |
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| 22 | #include <math.h> |
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| 23 | |
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| 24 | #include "math_private.h" |
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| 25 | |
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| 26 | |
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| 27 | __complex__ double |
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| 28 | __catan (__complex__ double x) |
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| 29 | { |
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| 30 | __complex__ double res; |
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| 31 | int rcls = fpclassify (__real__ x); |
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| 32 | int icls = fpclassify (__imag__ x); |
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| 33 | |
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| 34 | if (rcls <= FP_INFINITE || icls <= FP_INFINITE) |
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| 35 | { |
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| 36 | if (rcls == FP_INFINITE) |
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| 37 | { |
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| 38 | __real__ res = __copysign (M_PI_2, __real__ x); |
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| 39 | __imag__ res = __copysign (0.0, __imag__ x); |
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| 40 | } |
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| 41 | else if (icls == FP_INFINITE) |
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| 42 | { |
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| 43 | if (rcls >= FP_ZERO) |
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| 44 | __real__ res = __copysign (M_PI_2, __real__ x); |
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| 45 | else |
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| 46 | __real__ res = __nan (""); |
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| 47 | __imag__ res = __copysign (0.0, __imag__ x); |
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| 48 | } |
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| 49 | else if (icls == FP_ZERO || icls == FP_INFINITE) |
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| 50 | { |
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| 51 | __real__ res = __nan (""); |
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| 52 | __imag__ res = __copysign (0.0, __imag__ x); |
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| 53 | } |
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| 54 | else |
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| 55 | { |
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| 56 | __real__ res = __nan (""); |
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| 57 | __imag__ res = __nan (""); |
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| 58 | } |
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| 59 | } |
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| 60 | else if (rcls == FP_ZERO && icls == FP_ZERO) |
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| 61 | { |
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| 62 | res = x; |
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| 63 | } |
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| 64 | else |
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| 65 | { |
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| 66 | double r2, num, den; |
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| 67 | |
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| 68 | r2 = __real__ x * __real__ x; |
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| 69 | |
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| 70 | den = 1 - r2 - __imag__ x * __imag__ x; |
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| 71 | |
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| 72 | __real__ res = 0.5 * __ieee754_atan2 (2.0 * __real__ x, den); |
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| 73 | |
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| 74 | num = __imag__ x + 1.0; |
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| 75 | num = r2 + num * num; |
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| 76 | |
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| 77 | den = __imag__ x - 1.0; |
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| 78 | den = r2 + den * den; |
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| 79 | |
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| 80 | __imag__ res = 0.25 * __ieee754_log (num / den); |
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| 81 | } |
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| 82 | |
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| 83 | return res; |
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| 84 | } |
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| 85 | weak_alias (__catan, catan) |
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| 86 | #ifdef NO_LONG_DOUBLE |
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| 87 | strong_alias (__catan, __catanl) |
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| 88 | weak_alias (__catan, catanl) |
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| 89 | #endif |
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