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.
119 lines
2.0 KiB
119 lines
2.0 KiB
/***
|
|
*powhlp.c - pow() helper routines for handling special cases
|
|
*
|
|
* Copyright (c) 1991-2001, Microsoft Corporation. All rights reserved.
|
|
*
|
|
*Purpose:
|
|
* pow(x,y) helper routine. Handles +inf, -inf
|
|
*
|
|
*Revision History:
|
|
* 11-09-91 GDP
|
|
* 06-23-92 GDP adjusted return values according to the NCEG spec
|
|
* 02-06-95 JWM Mac merge
|
|
* 02-07-95 JWM powhlp() restored to Intel version.
|
|
*
|
|
*******************************************************************************/
|
|
#include <trans.h>
|
|
#include <float.h>
|
|
|
|
/***
|
|
*int _powhlp(double x, double y, double * result) - pow() helper
|
|
*
|
|
*Purpose:
|
|
* Calculate x^(sign)inf
|
|
*
|
|
*Entry:
|
|
* double x: the base
|
|
* int sign: the sign of the infinite exponent (0: pos, non-0: neg)
|
|
* double *result: pointer to the result
|
|
*
|
|
*Exit:
|
|
* 0: normal exit
|
|
* -1: indicates domain error for pow(x,inf)
|
|
*
|
|
*Exceptions:
|
|
*
|
|
***************************************************************************/
|
|
|
|
int _powhlp(double x, double y, double * result)
|
|
{
|
|
double absx;
|
|
int err = 0;
|
|
|
|
|
|
absx = ABS(x);
|
|
|
|
if (IS_D_INF(y)) {
|
|
if (absx > 1.0) {
|
|
*result = D_INF;
|
|
}
|
|
else if (absx < 1.0) {
|
|
*result = 0.0;
|
|
}
|
|
else {
|
|
*result = D_IND;
|
|
err = 1;
|
|
}
|
|
}
|
|
|
|
else if (IS_D_MINF(y)) {
|
|
if (absx > 1.0) {
|
|
*result = 0.0;
|
|
}
|
|
else if (absx < 1.0) {
|
|
*result = D_INF;
|
|
}
|
|
else {
|
|
*result = D_IND;
|
|
err = 1;
|
|
}
|
|
}
|
|
|
|
else if (IS_D_INF(x)) {
|
|
if (y > 0)
|
|
*result = D_INF;
|
|
else if (y < 0.0)
|
|
*result = 0.0;
|
|
else {
|
|
*result = 1.0;
|
|
}
|
|
}
|
|
|
|
else if (IS_D_MINF(x)) {
|
|
int type;
|
|
|
|
type = _d_inttype(y);
|
|
|
|
if (y > 0.0) {
|
|
*result = (type == _D_ODD ? -D_INF : D_INF);
|
|
}
|
|
else if (y < 0.0) {
|
|
*result = (type == _D_ODD ? D_MZERO : 0.0);
|
|
}
|
|
else {
|
|
*result = 1;
|
|
}
|
|
|
|
}
|
|
|
|
return err;
|
|
}
|
|
|
|
|
|
|
|
|
|
int _d_inttype(double y)
|
|
{
|
|
double rounded;
|
|
/* check if y is an integral value */
|
|
if (_fpclass(y) & (_FPCLASS_PD | _FPCLASS_ND))
|
|
return _D_NOINT;
|
|
rounded = _frnd(y);
|
|
if (rounded == y) {
|
|
if (_frnd(y/2.0) == y/2.0)
|
|
return _D_EVEN;
|
|
else
|
|
return _D_ODD;
|
|
}
|
|
return _D_NOINT;
|
|
}
|