125 lines
2.3 KiB
C
125 lines
2.3 KiB
C
|
|
/* @(#)z_powf.c 1.0 98/08/13 */
|
|
#include <float.h>
|
|
#include "fdlibm.h"
|
|
#include "zmath.h"
|
|
|
|
float powf (float x, float y)
|
|
{
|
|
float d, k, t, r = 1.0;
|
|
int n, sign, exponent_is_even_int = 0;
|
|
__int32_t px;
|
|
|
|
GET_FLOAT_WORD (px, x);
|
|
|
|
k = modff (y, &d);
|
|
|
|
if (k == 0.0)
|
|
{
|
|
/* Exponent y is an integer. */
|
|
if (modff (ldexpf (y, -1), &t))
|
|
{
|
|
/* y is odd. */
|
|
exponent_is_even_int = 0;
|
|
}
|
|
else
|
|
{
|
|
/* y is even. */
|
|
exponent_is_even_int = 1;
|
|
}
|
|
}
|
|
|
|
if (x == 0.0 && y <= 0.0)
|
|
{
|
|
errno = EDOM;
|
|
}
|
|
else if ((t = y * log (fabsf (x))) >= BIGX)
|
|
{
|
|
errno = ERANGE;
|
|
if (px & 0x80000000)
|
|
{
|
|
/* x is negative. */
|
|
if (k)
|
|
{
|
|
/* y is not an integer. */
|
|
errno = EDOM;
|
|
x = 0.0;
|
|
}
|
|
else if (exponent_is_even_int)
|
|
x = z_infinity_f.f;
|
|
else
|
|
x = -z_infinity_f.f;
|
|
}
|
|
else
|
|
{
|
|
x = z_infinity_f.f;
|
|
}
|
|
}
|
|
else if (t < SMALLX)
|
|
{
|
|
errno = ERANGE;
|
|
x = 0.0;
|
|
}
|
|
else
|
|
{
|
|
if ( !k && fabsf (d) <= 32767 )
|
|
{
|
|
n = (int) d;
|
|
|
|
if ((sign = (n < 0)))
|
|
n = -n;
|
|
|
|
while ( n > 0 )
|
|
{
|
|
if ((unsigned int) n % 2)
|
|
r *= x;
|
|
x *= x;
|
|
n = (unsigned int) n / 2;
|
|
}
|
|
|
|
if (sign)
|
|
r = 1.0 / r;
|
|
|
|
return r;
|
|
}
|
|
else
|
|
{
|
|
if ( px & 0x80000000 )
|
|
{
|
|
/* x is negative. */
|
|
if (k)
|
|
{
|
|
/* y is not an integer. */
|
|
errno = EDOM;
|
|
return 0.0;
|
|
}
|
|
}
|
|
|
|
x = exp (t);
|
|
|
|
if (!exponent_is_even_int)
|
|
{
|
|
if (px & 0x80000000)
|
|
{
|
|
/* y is an odd integer, and x is negative,
|
|
so the result is negative. */
|
|
GET_FLOAT_WORD (px, x);
|
|
px |= 0x80000000;
|
|
SET_FLOAT_WORD (x, px);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
return x;
|
|
}
|
|
|
|
#ifdef _DOUBLE_IS_32BITS
|
|
|
|
double pow (double x, double y)
|
|
{
|
|
return (double) powf ((float) x, (float) y);
|
|
}
|
|
|
|
#endif /* defined(_DOUBLE_IS_32BITS) */
|