1 | /* $NetBSD: catan.c,v 1.1 2007/08/20 16:01:32 drochner Exp $ */ |
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2 | |
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3 | /*- |
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4 | * Copyright (c) 2007 The NetBSD Foundation, Inc. |
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5 | * All rights reserved. |
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6 | * |
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7 | * This code is derived from software written by Stephen L. Moshier. |
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8 | * It is redistributed by the NetBSD Foundation by permission of the author. |
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9 | * |
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10 | * Redistribution and use in source and binary forms, with or without |
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11 | * modification, are permitted provided that the following conditions |
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12 | * are met: |
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13 | * 1. Redistributions of source code must retain the above copyright |
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14 | * notice, this list of conditions and the following disclaimer. |
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15 | * 2. Redistributions in binary form must reproduce the above copyright |
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16 | * notice, this list of conditions and the following disclaimer in the |
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17 | * documentation and/or other materials provided with the distribution. |
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18 | * |
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19 | * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS |
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20 | * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
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21 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
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22 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS |
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23 | * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
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24 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
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25 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
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26 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
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27 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
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28 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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29 | * POSSIBILITY OF SUCH DAMAGE. |
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30 | * |
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31 | * imported and modified include for newlib 2010/10/03 |
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32 | * Marco Atzeri <marco_atzeri@yahoo.it> |
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33 | */ |
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34 | |
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35 | /* |
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36 | FUNCTION |
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37 | <<catan>>, <<catanf>>---complex arc tangent |
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38 | |
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39 | INDEX |
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40 | catan |
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41 | INDEX |
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42 | catanf |
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43 | |
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44 | SYNOPSIS |
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45 | #include <complex.h> |
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46 | double complex catan(double complex <[z]>); |
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47 | float complex catanf(float complex <[z]>); |
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48 | |
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49 | |
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50 | DESCRIPTION |
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51 | @ifnottex |
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52 | These functions compute the complex arc tangent of <[z]>, |
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53 | with branch cuts outside the interval [-i, +i] along the |
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54 | imaginary axis. |
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55 | @end ifnottex |
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56 | @tex |
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57 | These functions compute the complex arc tangent of <[z]>, |
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58 | with branch cuts outside the interval [$-i$, $+i$] along the |
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59 | imaginary axis. |
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60 | @end tex |
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61 | |
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62 | <<catanf>> is identical to <<catan>>, except that it performs |
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63 | its calculations on <<floats complex>>. |
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64 | |
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65 | RETURNS |
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66 | @ifnottex |
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67 | These functions return the complex arc tangent value, in the range |
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68 | of a strip mathematically unbounded along the imaginary axis |
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69 | and in the interval [-pi/2, +pi/2] along the real axis. |
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70 | @end ifnottex |
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71 | @tex |
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72 | These functions return the complex arc tangent, in the range |
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73 | of a strip mathematically unbounded along the imaginary axis |
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74 | and in the interval [$-\pi/2$, $+\pi/2$] along the real axis. |
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75 | @end tex |
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76 | |
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77 | PORTABILITY |
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78 | <<catan>> and <<catanf>> are ISO C99 |
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79 | |
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80 | QUICKREF |
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81 | <<catan>> and <<catanf>> are ISO C99 |
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82 | |
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83 | */ |
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84 | |
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85 | |
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86 | #include <complex.h> |
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87 | #include <math.h> |
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88 | #include "cephes_subr.h" |
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89 | |
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90 | #ifdef __weak_alias |
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91 | __weak_alias(catan, _catan) |
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92 | #endif |
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93 | |
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94 | double complex |
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95 | catan(double complex z) |
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96 | { |
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97 | double complex w; |
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98 | double a, t, x, x2, y; |
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99 | |
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100 | x = creal(z); |
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101 | y = cimag(z); |
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102 | |
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103 | if ((x == 0.0) && (y > 1.0)) |
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104 | goto ovrf; |
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105 | |
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106 | x2 = x * x; |
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107 | a = 1.0 - x2 - (y * y); |
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108 | if (a == 0.0) |
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109 | goto ovrf; |
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110 | |
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111 | t = 0.5 * atan2(2.0 * x, a); |
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112 | w = _redupi(t); |
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113 | |
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114 | t = y - 1.0; |
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115 | a = x2 + (t * t); |
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116 | if (a == 0.0) |
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117 | goto ovrf; |
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118 | |
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119 | t = y + 1.0; |
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120 | a = (x2 + (t * t))/a; |
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121 | w = w + (0.25 * log(a)) * I; |
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122 | return w; |
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123 | |
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124 | ovrf: |
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125 | #if 0 |
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126 | mtherr ("catan", OVERFLOW); |
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127 | #endif |
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128 | w = HUGE_VAL + HUGE_VAL * I; |
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129 | return w; |
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130 | } |
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