1/* Compute projection of complex double value to Riemann sphere.
2   Copyright (C) 1997, 1999 Free Software Foundation, Inc.
3   This file is part of the GNU C Library.
4   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
5
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.
10
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.
15
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.  */
20
21#include <complex.h>
22#include <math.h>
23
24
25__complex__ double
26__cproj (__complex__ double x)
27{
28  __complex__ double res;
29
30  if (isnan (__real__ x) && isnan (__imag__ x))
31    return x;
32  else if (!isfinite (__real__ x) || !isfinite (__imag__ x))
33    {
34      __real__ res = INFINITY;
35      __imag__ res = copysign (0.0, __imag__ x);
36    }
37  else
38    {
39      double den = __real__ x * __real__ x + __imag__ x * __imag__ x + 1.0;
40
41      __real__ res = (2.0 * __real__ x) / den;
42      __imag__ res = (2.0 * __imag__ x) / den;
43    }
44
45  return res;
46}
47weak_alias (__cproj, cproj)
48#ifdef NO_LONG_DOUBLE
49strong_alias (__cproj, __cprojl)
50weak_alias (__cproj, cprojl)
51#endif
52