83 lines
1.7 KiB
C
83 lines
1.7 KiB
C
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/* DEC *PowerInteger(pDst,pSrc,i)
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*
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* ARGUMENT
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* DEC *pDst,*pSrc;
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* int i;
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*
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* DESCRIPTION
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* Raises pSrc to the power 'i'. If i<0, raises pSrc to the |i|, then
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* takes the reciprocal(ie, if i<0, then x**i = 1/x**|i|). If x=0, then
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* if i=<0, then error (GM_NAN), else pDst is set to 1. If x<0, then if the
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* power is odd, the result will be negative, otherwise positive. The
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* absolute value cannot exceed 2**63 -1. Note we call dpoxi() because
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* other high-level functions need returns of 2**79 -1, which is what
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* this routine gets back and then sqeezes it back to 64-bits.
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*
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* SIDE EFFECTS
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* *pDst is indeterminate on overflow, underflow. It is undisturbed
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* on GM_NULLPOINTER.
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*
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* RETURNS
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* Ptr to pDst if no errors, otherwise GM_NULL.
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*
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* POSSIBLE ERROR CODES
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*
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* GM_NULLPOINTER
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* GM_OVERFLOW
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* GM_UNDERFLOW
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*
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* AUTHOR
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* Andy Anderson 08-05-87 1130
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* Copyright (C) 1987-1990 Greenleaf Software Inc. All rights reserved.
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*
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* MODIFICATIONS
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*
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*/
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#include <stdio.h>
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#include "gm.h"
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#include "gmsystem.h"
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DEC *PowerInteger(pDst,pSrc,i)
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DEC *pDst,*pSrc;
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int i;
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{
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int wRetVal;
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_MacStart(GM_DPOWI);
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_MacInVarD(pSrc);
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_MacOutVarD(pDst);
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if (_MacIsDecZ(pSrc) && (i<=0)) {
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_MacErr(GM_PWR0);
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_MacRet(GM_NULL);
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}
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if (_MacIsDecZ(pSrc)) {
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_MacDZero(pDst);
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_MacRet(pDst);
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}
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wRetVal=_IntPwrDec80Bit(pDst,pSrc,i);
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/* then see if success */
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if(wRetVal == GM_OVERFLOW) {
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_MacErr(wRetVal);
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_MacRet(GM_NULL);
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}
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/* then try to reduce to 64-bit */
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wRetVal = _Sq5UnsTo4Uns(pDst); /* places or it's an error */
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if(wRetVal != GM_SUCCESS) {
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_MacErr(GM_OVERFLOW);
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_MacRet(GM_NULL);
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}
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if (_MacIsDecZ(pDst)) {
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_MacErr(GM_UNDERFLOW);
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}
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_MacRet(pDst);
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}
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