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