1 | /* $NetBSD: cproj.c,v 1.3 2010/09/20 17:51:38 christos Exp $ */ |
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2 | |
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3 | /*- |
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4 | * Copyright (c) 2010 The NetBSD Foundation, Inc. |
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5 | * All rights reserved. |
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6 | * |
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7 | * Redistribution and use in source and binary forms, with or without |
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8 | * modification, are permitted provided that the following conditions |
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9 | * are met: |
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10 | * 1. Redistributions of source code must retain the above copyright |
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11 | * notice, this list of conditions and the following disclaimer. |
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12 | * 2. Redistributions in binary form must reproduce the above copyright |
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13 | * notice, this list of conditions and the following disclaimer in the |
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14 | * documentation and/or other materials provided with the distribution. |
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15 | * |
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16 | * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS |
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17 | * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
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18 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
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19 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS |
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20 | * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
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21 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
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22 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
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23 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
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24 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
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25 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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26 | * POSSIBILITY OF SUCH DAMAGE. |
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27 | * |
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28 | * imported and modified include for newlib 2010/10/03 |
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29 | * Marco Atzeri <marco_atzeri@yahoo.it> |
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30 | */ |
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31 | |
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32 | /* |
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33 | FUNCTION |
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34 | <<cproj>>, <<cprojf>>--- Riemann sphere projection |
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35 | |
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36 | INDEX |
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37 | cproj |
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38 | INDEX |
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39 | cprojf |
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40 | |
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41 | SYNOPSIS |
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42 | #include <complex.h> |
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43 | double complex cproj(double complex <[z]>); |
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44 | float complex cprojf(float complex <[z]>); |
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45 | |
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46 | |
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47 | DESCRIPTION |
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48 | These functions compute a projection of <[z]> onto the Riemann |
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49 | sphere: <[z]> projects to <[z]> except that all complex infinities |
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50 | (even those with one infinite part and one NaN part) project |
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51 | to positive infinity on the real axis. If <[z]> has an infinite part, |
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52 | then <<cproj>>(<[z]>) is equivalent to |
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53 | |
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54 | INFINITY + I * copysign(0.0, cimag(z)) |
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55 | |
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56 | <<cprojf>> is identical to <<cproj>>, except that it performs |
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57 | its calculations on <<floats complex>>. |
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58 | |
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59 | RETURNS |
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60 | The cproj functions return the value of the projection onto |
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61 | the Riemann sphere. |
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62 | |
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63 | PORTABILITY |
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64 | <<cproj>> and <<cprojf>> are ISO C99 |
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65 | |
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66 | QUICKREF |
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67 | <<cproj>> and <<cprojf>> are ISO C99 |
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68 | |
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69 | */ |
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70 | |
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71 | #include <sys/cdefs.h> |
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72 | /*__RCSID("$NetBSD: cproj.c,v 1.3 2010/09/20 17:51:38 christos Exp $"); */ |
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73 | |
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74 | #include <complex.h> |
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75 | #include <math.h> |
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76 | |
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77 | #include "../common/fdlibm.h" |
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78 | |
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79 | /* |
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80 | * cproj(double complex z) |
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81 | * |
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82 | * These functions return the value of the projection (not stereographic!) |
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83 | * onto the Riemann sphere. |
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84 | * |
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85 | * z projects to z, except that all complex infinities (even those with one |
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86 | * infinite part and one NaN part) project to positive infinity on the real axis. |
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87 | * If z has an infinite part, then cproj(z) shall be equivalent to: |
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88 | * |
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89 | * INFINITY + I * copysign(0.0, cimag(z)) |
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90 | */ |
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91 | double complex |
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92 | cproj(double complex z) |
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93 | { |
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94 | double_complex w = { .z = z }; |
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95 | |
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96 | if (isinf(creal(z)) || isinf(cimag(z))) { |
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97 | #ifdef __INFINITY |
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98 | REAL_PART(w) = __INFINITY; |
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99 | #else |
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100 | REAL_PART(w) = INFINITY; |
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101 | #endif |
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102 | IMAG_PART(w) = copysign(0.0, cimag(z)); |
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103 | } |
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104 | |
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105 | return (w.z); |
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106 | } |
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