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[glibc/history.git] / math / s_cproj.c
blob8e7ca41df86da3075150ff3f53261000c8d2dba0
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.
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.
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.
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. */
21 #include <complex.h>
22 #include <math.h>
25 __complex__ double
26 __cproj (__complex__ double x)
28 __complex__ double res;
30 if (isnan (__real__ x) && isnan (__imag__ x))
31 return x;
32 else if (!isfinite (__real__ x) || !isfinite (__imag__ x))
34 __real__ res = INFINITY;
35 __imag__ res = __copysign (0.0, __imag__ x);
37 else
39 double den = __real__ x * __real__ x + __imag__ x * __imag__ x + 1.0;
41 __real__ res = (2.0 * __real__ x) / den;
42 __imag__ res = (2.0 * __imag__ x) / den;
45 return res;
47 weak_alias (__cproj, cproj)
48 #ifdef NO_LONG_DOUBLE
49 strong_alias (__cproj, __cprojl)
50 weak_alias (__cproj, cprojl)
51 #endif