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b2dad0e372
2000-04-21 Benjamin Kosnik <bkoz@redhat.com> * libstdc++-v3: New directory. From-SVN: r33317
115 lines
3.2 KiB
C
115 lines
3.2 KiB
C
/* Complex square root of long double value. */
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/* Copyright (C) 1997-1999 Free Software Foundation, Inc.
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This file is part of the GNU ISO C++ Library. This library is free
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software; you can redistribute it and/or modify it under the
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terms of the GNU General Public License as published by the
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Free Software Foundation; either version 2, or (at your option)
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any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this library; see the file COPYING. If not, write to the Free
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Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
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USA.
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As a special exception, you may use this file as part of a free software
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library without restriction. Specifically, if other files instantiate
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templates or use macros or inline functions from this file, or you compile
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this file and link it with other files to produce an executable, this
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file does not by itself cause the resulting executable to be covered by
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the GNU General Public License. This exception does not however
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invalidate any other reasons why the executable file might be covered by
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the GNU General Public License. */
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#include <math.h>
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#include "mathconf.h"
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/* Thanks to SGI we have to trick here. At least Irix 6.2 provides hypotl,
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but it has a wrong prototype. Grrr. */
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extern long double local_hypotl (long double, long double) asm ("hypotl");
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__complex__ long double
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csqrtl (__complex__ long double x)
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{
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__complex__ long double res;
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if (!FINITEL_P (__real__ x) || !FINITEL_P (__imag__ x))
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{
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if (INFINITEL_P (__imag__ x))
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{
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__real__ res = HUGE_VALL;
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__imag__ res = __imag__ x;
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}
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else if (INFINITEL_P (__real__ x))
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{
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if (__real__ x < 0.0)
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{
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__real__ res = __imag__ x != __imag__ x ? NAN : 0;
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__imag__ res = copysignl (HUGE_VALL, __imag__ x);
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}
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else
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{
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__real__ res = __real__ x;
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__imag__ res = (__imag__ x != __imag__ x
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? NAN : copysignl (0.0, __imag__ x));
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}
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}
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else
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{
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__real__ res = NAN;
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__imag__ res = NAN;
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}
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}
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else
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{
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if (__imag__ x == 0.0)
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{
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if (__real__ x < 0.0)
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{
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__real__ res = 0.0;
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__imag__ res = copysignl (sqrtl (-__real__ x), __imag__ x);
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}
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else
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{
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__real__ res = fabsl (sqrtl (__real__ x));
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__imag__ res = copysignl (0.0, __imag__ x);
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}
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}
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else if (__real__ x == 0.0)
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{
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long double r = sqrtl (0.5 * fabsl (__imag__ x));
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__real__ res = copysignl (r, __imag__ x);
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__imag__ res = r;
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}
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else
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{
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__complex__ long double q;
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long double t, r;
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if (fabsl (__imag__ x) < 2.0e-4 * fabsl (__real__ x))
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t = 0.25 * __imag__ x * (__imag__ x / __real__ x);
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else
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t = 0.5 * (local_hypotl (__real__ x, __imag__ x) - __real__ x);
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r = sqrtl (t);
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__real__ q = __imag__ x / (2.0 * r);
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__imag__ q = r;
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/* Heron iteration in complex arithmetic. */
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res = 0.5 * (q + q / x);
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}
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}
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return res;
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}
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