110 lines
2.3 KiB
C
110 lines
2.3 KiB
C
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/* @(#)z_sinehf.c 1.0 98/08/13 */
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/******************************************************************
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* The following routines are coded directly from the algorithms
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* and coefficients given in "Software Manual for the Elementary
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* Functions" by William J. Cody, Jr. and William Waite, Prentice
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* Hall, 1980.
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******************************************************************/
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/******************************************************************
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* Hyperbolic Sine
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*
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* Input:
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* x - floating point value
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*
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* Output:
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* hyperbolic sine of x
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*
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* Description:
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* This routine calculates hyperbolic sines.
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*
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*****************************************************************/
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#include <float.h>
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#include "fdlibm.h"
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#include "zmath.h"
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static const float q[] = { -0.428277109e+2 };
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static const float p[] = { -0.713793159e+1,
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-0.190333399 };
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static const float LNV = 0.6931610107;
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static const float INV_V2 = 0.2499930850;
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static const float V_OVER2_MINUS1 = 0.1383027787e-4;
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float
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sinehf (float x,
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int cosineh)
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{
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float y, f, P, Q, R, res, z, w;
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int sgn = 1;
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float WBAR = 18.55;
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/* Check for special values. */
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switch (numtestf (x))
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{
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case NAN:
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errno = EDOM;
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return (x);
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case INF:
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errno = ERANGE;
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return (ispos (x) ? z_infinity_f.f : -z_infinity_f.f);
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}
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y = fabs (x);
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if (!cosineh && x < 0.0)
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sgn = -1;
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if ((y > 1.0 && !cosineh) || cosineh)
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{
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if (y > BIGX)
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{
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w = y - LNV;
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/* Check for w > maximum here. */
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if (w > BIGX)
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{
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errno = ERANGE;
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return (x);
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}
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z = exp (w);
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if (w > WBAR)
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res = z * (V_OVER2_MINUS1 + 1.0);
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}
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else
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{
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z = exp (y);
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if (cosineh)
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res = (z + 1 / z) / 2.0;
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else
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res = (z - 1 / z) / 2.0;
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}
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if (sgn < 0)
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res = -res;
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}
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else
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{
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/* Check for y being too small. */
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if (y < z_rooteps_f)
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{
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res = x;
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}
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/* Calculate the Taylor series. */
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else
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{
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f = x * x;
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Q = f + q[0];
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P = p[1] * f + p[0];
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R = f * (P / Q);
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res = x + x * R;
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}
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}
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return (res);
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}
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