xref: /minix3/lib/libm/complex/cproj.c (revision 84d9c625bfea59e274550651111ae9edfdc40fbd)
1*84d9c625SLionel Sambuc /*	$NetBSD: cproj.c,v 1.5 2011/11/02 02:34:56 christos Exp $	*/
22fe8fb19SBen Gras 
32fe8fb19SBen Gras /*-
42fe8fb19SBen Gras  * Copyright (c) 2010 The NetBSD Foundation, Inc.
52fe8fb19SBen Gras  * All rights reserved.
62fe8fb19SBen Gras  *
72fe8fb19SBen Gras  * Redistribution and use in source and binary forms, with or without
82fe8fb19SBen Gras  * modification, are permitted provided that the following conditions
92fe8fb19SBen Gras  * are met:
102fe8fb19SBen Gras  * 1. Redistributions of source code must retain the above copyright
112fe8fb19SBen Gras  *    notice, this list of conditions and the following disclaimer.
122fe8fb19SBen Gras  * 2. Redistributions in binary form must reproduce the above copyright
132fe8fb19SBen Gras  *    notice, this list of conditions and the following disclaimer in the
142fe8fb19SBen Gras  *    documentation and/or other materials provided with the distribution.
152fe8fb19SBen Gras  *
162fe8fb19SBen Gras  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
172fe8fb19SBen Gras  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
182fe8fb19SBen Gras  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
192fe8fb19SBen Gras  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
202fe8fb19SBen Gras  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
212fe8fb19SBen Gras  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
222fe8fb19SBen Gras  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
232fe8fb19SBen Gras  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
242fe8fb19SBen Gras  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
252fe8fb19SBen Gras  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
262fe8fb19SBen Gras  * POSSIBILITY OF SUCH DAMAGE.
272fe8fb19SBen Gras  */
282fe8fb19SBen Gras #include <sys/cdefs.h>
29*84d9c625SLionel Sambuc __RCSID("$NetBSD: cproj.c,v 1.5 2011/11/02 02:34:56 christos Exp $");
302fe8fb19SBen Gras 
312fe8fb19SBen Gras #include <complex.h>
322fe8fb19SBen Gras #include <math.h>
332fe8fb19SBen Gras 
342fe8fb19SBen Gras #include "../src/math_private.h"
352fe8fb19SBen Gras 
362fe8fb19SBen Gras /*
372fe8fb19SBen Gras  * cproj(double complex z)
382fe8fb19SBen Gras  *
392fe8fb19SBen Gras  * These functions return the value of the projection (not stereographic!)
402fe8fb19SBen Gras  * onto the Riemann sphere.
412fe8fb19SBen Gras  *
422fe8fb19SBen Gras  * z projects to z, except that all complex infinities (even those with one
432fe8fb19SBen Gras  * infinite part and one NaN part) project to positive infinity on the real axis.
442fe8fb19SBen Gras  * If z has an infinite part, then cproj(z) shall be equivalent to:
452fe8fb19SBen Gras  *
462fe8fb19SBen Gras  * INFINITY + I * copysign(0.0, cimag(z))
472fe8fb19SBen Gras  */
482fe8fb19SBen Gras double complex
cproj(double complex z)492fe8fb19SBen Gras cproj(double complex z)
502fe8fb19SBen Gras {
512fe8fb19SBen Gras 	double_complex w = { .z = z };
522fe8fb19SBen Gras 
53*84d9c625SLionel Sambuc 	/*CONSTCOND*/
54*84d9c625SLionel Sambuc 	if (isinf(creal(z)) || isinf(cimag(z))) {
552fe8fb19SBen Gras #ifdef __INFINITY
56*84d9c625SLionel Sambuc 		REAL_PART(w) = HUGE_VAL;
572fe8fb19SBen Gras #else
582fe8fb19SBen Gras 		REAL_PART(w) = INFINITY;
592fe8fb19SBen Gras #endif
602fe8fb19SBen Gras 		IMAG_PART(w) = copysign(0.0, cimag(z));
612fe8fb19SBen Gras 	}
622fe8fb19SBen Gras 
632fe8fb19SBen Gras 	return (w.z);
642fe8fb19SBen Gras }
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