1 /* $NetBSD: cproj.c,v 1.3 2010/09/20 17:51:38 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 * imported and modified include for newlib 2010/10/03
29 * Marco Atzeri <marco_atzeri@yahoo.it>
30 */
31
32 /*
33 FUNCTION
34 <<cproj>>, <<cprojf>>--- Riemann sphere projection
35
36 INDEX
37 cproj
38 INDEX
39 cprojf
40
41 SYNOPSIS
42 #include <complex.h>
43 double complex cproj(double complex <[z]>);
44 float complex cprojf(float complex <[z]>);
45
46
47 DESCRIPTION
48 These functions compute a projection of <[z]> onto the Riemann
49 sphere: <[z]> projects to <[z]> except that all complex infinities
50 (even those with one infinite part and one NaN part) project
51 to positive infinity on the real axis. If <[z]> has an infinite part,
52 then <<cproj>>(<[z]>) is equivalent to
53
54 INFINITY + (double complex) I * copysign(0.0, cimag(z))
55
56 <<cprojf>> is identical to <<cproj>>, except that it performs
57 its calculations on <<floats complex>>.
58
59 RETURNS
60 The cproj functions return the value of the projection onto
61 the Riemann sphere.
62
63 PORTABILITY
64 <<cproj>> and <<cprojf>> are ISO C99
65
66 QUICKREF
67 <<cproj>> and <<cprojf>> are ISO C99
68
69 */
70
71 #include <sys/cdefs.h>
72 /*__RCSID("$NetBSD: cproj.c,v 1.3 2010/09/20 17:51:38 christos Exp $"); */
73
74 #include <complex.h>
75 #include <math.h>
76
77 #include "../common/fdlibm.h"
78
79 /*
80 * cproj(double complex z)
81 *
82 * These functions return the value of the projection (not stereographic!)
83 * onto the Riemann sphere.
84 *
85 * z projects to z, except that all complex infinities (even those with one
86 * infinite part and one NaN part) project to positive infinity on the real axis.
87 * If z has an infinite part, then cproj(z) shall be equivalent to:
88 *
89 * INFINITY + (double complex) I * copysign(0.0, cimag(z))
90 */
91 double complex
cproj(double complex z)92 cproj(double complex z)
93 {
94 double_complex w = { .z = z };
95
96 if (isinf(creal(z)) || isinf(cimag(z))) {
97 #ifdef __INFINITY
98 REAL_PART(w) = __INFINITY;
99 #else
100 REAL_PART(w) = (double) INFINITY;
101 #endif
102 IMAG_PART(w) = copysign(0.0, cimag(z));
103 }
104
105 return (w.z);
106 }
107
