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/* @(#)z_sinef.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.
******************************************************************/
/******************************************************************
* sine generator
*
* Input:
* x - floating point value
* cosine - indicates cosine value
*
* Output:
* Sine of x.
*
* Description:
* This routine calculates sines and cosines.
*
*****************************************************************/
#include "fdlibm.h"
#include "zmath.h"
static const float HALF_PI = 1.570796326;
static const float ONE_OVER_PI = 0.318309886;
static const float r[] = { -0.1666665668,
0.8333025139e-02,
-0.1980741872e-03,
0.2601903036e-5 };
float
_DEFUN (sinef, (float, int),
float x _AND
int cosine)
{
int sgn, N;
float y, XN, g, R, res;
float YMAX = 210828714.0;
switch (numtestf (x))
{
case NAN:
errno = EDOM;
return (x);
case INF:
errno = EDOM;
return (z_notanum_f.f);
}
/* Use sin and cos properties to ease computations. */
if (cosine)
{
sgn = 1;
y = fabsf (x) + HALF_PI;
}
else
{
if (x < 0.0)
{
sgn = -1;
y = -x;
}
else
{
sgn = 1;
y = x;
}
}
/* Check for values of y that will overflow here. */
if (y > YMAX)
{
errno = ERANGE;
return (x);
}
/* Calculate the exponent. */
if (y < 0.0)
N = (int) (y * ONE_OVER_PI - 0.5);
else
N = (int) (y * ONE_OVER_PI + 0.5);
XN = (float) N;
if (N & 1)
sgn = -sgn;
if (cosine)
XN -= 0.5;
y = fabsf (x) - XN * __PI;
if (-z_rooteps_f < y && y < z_rooteps_f)
res = y;
else
{
g = y * y;
/* Calculate the Taylor series. */
R = (((r[3] * g + r[2]) * g + r[1]) * g + r[0]) * g;
/* Finally, compute the result. */
res = y + y * R;
}
res *= sgn;
return (res);
}
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