[444] | 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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