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/* $NetBSD: cproj.c,v 1.3 2010/09/20 17:51:38 christos Exp $ */
/*-
* Copyright (c) 2010 The NetBSD Foundation, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* imported and modified include for newlib 2010/10/03
* Marco Atzeri <marco_atzeri@yahoo.it>
*/
/*
FUNCTION
<<cproj>>, <<cprojf>>--- Riemann sphere projection
INDEX
cproj
INDEX
cprojf
ANSI_SYNOPSIS
#include <complex.h>
double complex cproj(double complex <[z]>);
float complex cprojf(float complex <[z]>);
DESCRIPTION
These functions compute a projection of <[z]> onto the Riemann
sphere: <[z]> projects to <[z]> except that all complex infinities
(even those with one infinite part and one NaN part) project
to positive infinity on the real axis. If <[z]> has an infinite part,
then <<cproj>>(<[z]>) is equivalent to
INFINITY + I * copysign(0.0, cimag(z))
<<cprojf>> is identical to <<cproj>>, except that it performs
its calculations on <<floats complex>>.
RETURNS
The cproj functions return the value of the projection onto
the Riemann sphere.
PORTABILITY
<<cproj>> and <<cprojf>> are ISO C99
QUICKREF
<<cproj>> and <<cprojf>> are ISO C99
*/
/*__RCSID("$NetBSD: cproj.c,v 1.3 2010/09/20 17:51:38 christos Exp $"); */
#include <complex.h>
#include <math.h>
#include "fdlibm.h"
/*
* cproj(double complex z)
*
* These functions return the value of the projection (not stereographic!)
* onto the Riemann sphere.
*
* z projects to z, except that all complex infinities (even those with one
* infinite part and one NaN part) project to positive infinity on the real axis.
* If z has an infinite part, then cproj(z) shall be equivalent to:
*
* INFINITY + I * copysign(0.0, cimag(z))
*/
double complex
cproj(double complex z)
{
double_complex w = { .z = z };
if (isinf(creal(z)) || isinf(cimag(z))) {
#ifdef __INFINITY
REAL_PART(w) = __INFINITY;
#else
REAL_PART(w) = INFINITY;
#endif
IMAG_PART(w) = copysign(0.0, cimag(z));
}
return (w.z);
}
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