1 | |
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2 | /* @(#)z_sinehf.c 1.0 98/08/13 */ |
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3 | /****************************************************************** |
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4 | * The following routines are coded directly from the algorithms |
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5 | * and coefficients given in "Software Manual for the Elementary |
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6 | * Functions" by William J. Cody, Jr. and William Waite, Prentice |
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7 | * Hall, 1980. |
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8 | ******************************************************************/ |
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9 | /****************************************************************** |
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10 | * Hyperbolic Sine |
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11 | * |
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12 | * Input: |
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13 | * x - floating point value |
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14 | * |
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15 | * Output: |
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16 | * hyperbolic sine of x |
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17 | * |
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18 | * Description: |
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19 | * This routine calculates hyperbolic sines. |
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20 | * |
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21 | *****************************************************************/ |
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22 | |
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23 | #include <float.h> |
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24 | #include "fdlibm.h" |
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25 | #include "zmath.h" |
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26 | |
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27 | static const float q[] = { -0.428277109e+2 }; |
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28 | static const float p[] = { -0.713793159e+1, |
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29 | -0.190333399 }; |
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30 | static const float LNV = 0.6931610107; |
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31 | static const float INV_V2 = 0.2499930850; |
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32 | static const float V_OVER2_MINUS1 = 0.1383027787e-4; |
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33 | |
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34 | float |
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35 | sinehf (float x, |
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36 | int cosineh) |
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37 | { |
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38 | float y, f, P, Q, R, res, z, w; |
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39 | int sgn = 1; |
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40 | float WBAR = 18.55; |
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41 | |
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42 | /* Check for special values. */ |
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43 | switch (numtestf (x)) |
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44 | { |
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45 | case NAN: |
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46 | errno = EDOM; |
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47 | return (x); |
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48 | case INF: |
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49 | errno = ERANGE; |
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50 | return (ispos (x) ? z_infinity_f.f : -z_infinity_f.f); |
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51 | } |
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52 | |
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53 | y = fabs (x); |
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54 | |
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55 | if (!cosineh && x < 0.0) |
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56 | sgn = -1; |
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57 | |
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58 | if ((y > 1.0 && !cosineh) || cosineh) |
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59 | { |
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60 | if (y > BIGX) |
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61 | { |
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62 | w = y - LNV; |
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63 | |
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64 | /* Check for w > maximum here. */ |
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65 | if (w > BIGX) |
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66 | { |
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67 | errno = ERANGE; |
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68 | return (x); |
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69 | } |
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70 | |
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71 | z = exp (w); |
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72 | |
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73 | if (w > WBAR) |
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74 | res = z * (V_OVER2_MINUS1 + 1.0); |
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75 | } |
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76 | |
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77 | else |
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78 | { |
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79 | z = exp (y); |
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80 | if (cosineh) |
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81 | res = (z + 1 / z) / 2.0; |
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82 | else |
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83 | res = (z - 1 / z) / 2.0; |
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84 | } |
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85 | |
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86 | if (sgn < 0) |
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87 | res = -res; |
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88 | } |
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89 | else |
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90 | { |
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91 | /* Check for y being too small. */ |
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92 | if (y < z_rooteps_f) |
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93 | { |
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94 | res = x; |
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95 | } |
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96 | /* Calculate the Taylor series. */ |
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97 | else |
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98 | { |
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99 | f = x * x; |
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100 | Q = f + q[0]; |
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101 | P = p[1] * f + p[0]; |
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102 | R = f * (P / Q); |
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103 | |
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104 | res = x + x * R; |
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105 | } |
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106 | } |
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107 | |
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108 | return (res); |
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109 | } |
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