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