math/s_cprojl.c

   1 /* Compute projection of complex long 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__ long double
  26 __cprojl (__complex__ long double x)
  27 {
  28   __complex__ long 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 = __copysignl (0.0, __imag__ x);
  36     }
  37   else
  38     {
  39       long double den = (__real__ x * __real__ x + __imag__ x * __imag__ x
  40                          + 1.0);
  41
  42       __real__ res = (2.0 * __real__ x) / den;
  43       __imag__ res = (2.0 * __imag__ x) / den;
  44     }
  45
  46   return res;
  47 }
  48 weak_alias (__cprojl, cprojl)