mirror of https://github.com/tongzx/nt5src
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
59 lines
1.3 KiB
59 lines
1.3 KiB
/* _FExp function */
|
|
#include "wctype.h"
|
|
#include "xmath.h"
|
|
_STD_BEGIN
|
|
|
|
static const float p[] = { /* courtesy Dr. Tim Prince */
|
|
1.0F,
|
|
60.09114349F};
|
|
static const float q[] = { /* courtesy Dr. Tim Prince */
|
|
12.01517514F,
|
|
120.18228722F};
|
|
static const double c1 = 22713.0 / 32768.0;
|
|
static const double c2 = 1.428606820309417232e-6L;
|
|
static const float hugexp = FHUGE_EXP;
|
|
static const float invln2 = 1.4426950408889634074F;
|
|
|
|
_CRTIMP2 short __cdecl _FExp(float *px, float y, short eoff)
|
|
{ /* compute y*e^(*px), (*px) finite, |y| not huge */
|
|
if (*px < -hugexp || y == 0)
|
|
{ /* certain underflow */
|
|
*px = 0;
|
|
return (0);
|
|
}
|
|
else if (hugexp < *px)
|
|
{ /* certain overflow */
|
|
*px = _FInf._F;
|
|
return (INF);
|
|
}
|
|
else
|
|
{ /* xexp won't overflow */
|
|
float g = *px * invln2;
|
|
short xexp = g + (g < 0 ? - 0.5 : + 0.5);
|
|
|
|
g = xexp;
|
|
g = (*px - g * c1) - g * c2;
|
|
if (-_FEps._F < g && g < _FEps._F)
|
|
*px = y;
|
|
else
|
|
{ /* g*g worth computing */
|
|
const float z = g * g;
|
|
const float w = q[0] * z + q[1];
|
|
|
|
g *= z + p[1];
|
|
*px = (w + g) / (w - g) * 2 * y;
|
|
--xexp;
|
|
}
|
|
return (_FDscale(px, (long)xexp + eoff));
|
|
}
|
|
}
|
|
_STD_END
|
|
|
|
/*
|
|
* Copyright (c) 1994 by P.J. Plauger. ALL RIGHTS RESERVED.
|
|
* Consult your license regarding permissions and restrictions.
|
|
*/
|
|
|
|
/*
|
|
941029 pjp: added _STD machinery
|
|
*/
|