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      1 /*	$NetBSD: cproj.c,v 1.5 2011/11/02 02:34:56 christos Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2010 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 #include <sys/cdefs.h>
     29 __RCSID("$NetBSD: cproj.c,v 1.5 2011/11/02 02:34:56 christos Exp $");
     30 
     31 #include <complex.h>
     32 #include <math.h>
     33 
     34 #include "../src/math_private.h"
     35 
     36 /*
     37  * cproj(double complex z)
     38  *
     39  * These functions return the value of the projection (not stereographic!)
     40  * onto the Riemann sphere.
     41  *
     42  * z projects to z, except that all complex infinities (even those with one
     43  * infinite part and one NaN part) project to positive infinity on the real axis.
     44  * If z has an infinite part, then cproj(z) shall be equivalent to:
     45  *
     46  * INFINITY + I * copysign(0.0, cimag(z))
     47  */
     48 double complex
     49 cproj(double complex z)
     50 {
     51 	double_complex w = { .z = z };
     52 
     53 	/*CONSTCOND*/
     54 	if (isinf(creal(z)) || isinf(cimag(z))) {
     55 #ifdef __INFINITY
     56 		REAL_PART(w) = HUGE_VAL;
     57 #else
     58 		REAL_PART(w) = INFINITY;
     59 #endif
     60 		IMAG_PART(w) = copysign(0.0, cimag(z));
     61 	}
     62 
     63 	return (w.z);
     64 }
     65