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glibc  2.9
s_cproj.c
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00001 /* Compute projection of complex double value to Riemann sphere.
00002    Copyright (C) 1997, 1999 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
00005 
00006    The GNU C Library is free software; you can redistribute it and/or
00007    modify it under the terms of the GNU Lesser General Public
00008    License as published by the Free Software Foundation; either
00009    version 2.1 of the License, or (at your option) any later version.
00010 
00011    The GNU C Library is distributed in the hope that it will be useful,
00012    but WITHOUT ANY WARRANTY; without even the implied warranty of
00013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014    Lesser General Public License for more details.
00015 
00016    You should have received a copy of the GNU Lesser General Public
00017    License along with the GNU C Library; if not, write to the Free
00018    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00019    02111-1307 USA.  */
00020 
00021 #include <complex.h>
00022 #include <math.h>
00023 
00024 
00025 __complex__ double
00026 __cproj (__complex__ double x)
00027 {
00028   __complex__ double res;
00029 
00030   if (isnan (__real__ x) && isnan (__imag__ x))
00031     return x;
00032   else if (!isfinite (__real__ x) || !isfinite (__imag__ x))
00033     {
00034       __real__ res = INFINITY;
00035       __imag__ res = __copysign (0.0, __imag__ x);
00036     }
00037   else
00038     {
00039       double den = __real__ x * __real__ x + __imag__ x * __imag__ x + 1.0;
00040 
00041       __real__ res = (2.0 * __real__ x) / den;
00042       __imag__ res = (2.0 * __imag__ x) / den;
00043     }
00044 
00045   return res;
00046 }
00047 weak_alias (__cproj, cproj)
00048 #ifdef NO_LONG_DOUBLE
00049 strong_alias (__cproj, __cprojl)
00050 weak_alias (__cproj, cprojl)
00051 #endif