1 /* Complex square root of long double value.
2 Copyright (C) 1997 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Based on an algorithm by Stephen L. Moshier <moshier@world.std.com>.
5 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Library General Public License as
9 published by the Free Software Foundation; either version 2 of the
10 License, or (at your option) any later version.
12 The GNU C Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Library General Public License for more details.
17 You should have received a copy of the GNU Library General Public
18 License along with the GNU C Library; see the file COPYING.LIB. If not,
19 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
25 #include "math_private.h"
28 __complex__ long double
29 __csqrtl (__complex__ long double x)
31 __complex__ long double res;
32 int rcls = fpclassify (__real__ x);
33 int icls = fpclassify (__imag__ x);
35 if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
37 if (icls == FP_INFINITE)
39 __real__ res = HUGE_VALL;
40 __imag__ res = __imag__ x;
42 else if (rcls == FP_INFINITE)
46 __real__ res = icls == FP_NAN ? __nanl ("") : 0;
47 __imag__ res = __copysignl (HUGE_VALL, __imag__ x);
51 __real__ res = __real__ x;
52 __imag__ res = (icls == FP_NAN
53 ? __nanl ("") : __copysignl (0.0, __imag__ x));
58 __real__ res = __nanl ("");
59 __imag__ res = __nanl ("");
69 __imag__ res = __copysignl (__ieee754_sqrtl (-__real__ x),
74 __real__ res = fabsl (__ieee754_sqrtl (__real__ x));
75 __imag__ res = __copysignl (0.0, __imag__ x);
78 else if (rcls == FP_ZERO)
80 long double r = __ieee754_sqrtl (0.5 * fabsl (__imag__ x));
82 __real__ res = __copysignl (r, __imag__ x);
87 __complex__ long double q;
90 if (fabsl (__imag__ x) < 2.0e-4 * fabsl (__real__ x))
91 t = 0.25 * __imag__ x * (__imag__ x / __real__ x);
93 t = 0.5 * (__ieee754_hypotl (__real__ x, __imag__ x) - __real__ x);
95 r = __ieee754_sqrtl (t);
97 __real__ q = __imag__ x / (2.0 * r);
100 /* Heron iteration in complex arithmetic. */
101 res = 0.5 * (q + q / x);
107 weak_alias (__csqrtl, csqrtl)