102 lines
1.7 KiB
C
102 lines
1.7 KiB
C
/*
|
|
* (c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
|
|
* See the copyright notice in the ACK home directory, in the file "Copyright".
|
|
*
|
|
* Author: Ceriel J.H. Jacobs
|
|
*/
|
|
|
|
/* $Header$ */
|
|
|
|
#define __NO_DEFS
|
|
#include <math.h>
|
|
|
|
#if __STDC__
|
|
#include <pc_math.h>
|
|
#endif
|
|
|
|
static double
|
|
sinus(x, cos_flag)
|
|
double x;
|
|
{
|
|
/* Algorithm and coefficients from:
|
|
"Software manual for the elementary functions"
|
|
by W.J. Cody and W. Waite, Prentice-Hall, 1980
|
|
*/
|
|
|
|
static double r[] = {
|
|
-0.16666666666666665052e+0,
|
|
0.83333333333331650314e-2,
|
|
-0.19841269841201840457e-3,
|
|
0.27557319210152756119e-5,
|
|
-0.25052106798274584544e-7,
|
|
0.16058936490371589114e-9,
|
|
-0.76429178068910467734e-12,
|
|
0.27204790957888846175e-14
|
|
};
|
|
|
|
double xsqr;
|
|
double y;
|
|
int neg = 0;
|
|
|
|
if (x < 0) {
|
|
x = -x;
|
|
neg = 1;
|
|
}
|
|
if (cos_flag) {
|
|
neg = 0;
|
|
y = M_PI_2 + x;
|
|
}
|
|
else y = x;
|
|
|
|
/* ??? avoid loss of significance, if y is too large, error ??? */
|
|
|
|
y = y * M_1_PI + 0.5;
|
|
|
|
/* Use extended precision to calculate reduced argument.
|
|
Here we used 12 bits of the mantissa for a1.
|
|
Also split x in integer part x1 and fraction part x2.
|
|
*/
|
|
#define A1 3.1416015625
|
|
#define A2 -8.908910206761537356617e-6
|
|
{
|
|
double x1, x2;
|
|
extern double _fif();
|
|
|
|
_fif(y, 1.0, &y);
|
|
if (_fif(y, 0.5, &x1)) neg = !neg;
|
|
if (cos_flag) y -= 0.5;
|
|
x2 = _fif(x, 1.0, &x1);
|
|
x = x1 - y * A1;
|
|
x += x2;
|
|
x -= y * A2;
|
|
#undef A1
|
|
#undef A2
|
|
}
|
|
|
|
if (x < 0) {
|
|
neg = !neg;
|
|
x = -x;
|
|
}
|
|
|
|
/* ??? avoid underflow ??? */
|
|
|
|
y = x * x;
|
|
x += x * y * POLYNOM7(y, r);
|
|
return neg ? -x : x;
|
|
}
|
|
|
|
double
|
|
_sin(x)
|
|
double x;
|
|
{
|
|
return sinus(x, 0);
|
|
}
|
|
|
|
double
|
|
_cos(x)
|
|
double x;
|
|
{
|
|
if (x < 0) x = -x;
|
|
return sinus(x, 1);
|
|
}
|