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