124 lines
2.0 KiB
C
124 lines
2.0 KiB
C
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/* DEC *PowerRational(pDst,pSrc1,m,n)
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*
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* ARGUMENT
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* DEC *pDst,*pSrc1;
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* int m,n;
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*
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* DESCRIPTION
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* Calculates pSrc1 to the power m/n and returns the answer in pDst.
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* This provides an x**(m/n) power function for DEC numbers.
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*
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* SIDE EFFECTS
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* None.
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*
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* RETURNS
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* Pointer to the result if no error, otherwise GM_NULL.
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*
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* ALGORITHM:
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* x**(m/n) = e**((m/n)*ln(x)). Therefore, call dlnx() to get the
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* natural log
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* and then multiply by the power of x. Finally, call dexx() to provide
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* e**z.
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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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* GM_IMAG
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* GM_PWR0
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* GM_DIV0
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*
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* AUTHOR
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* Andy Anderson 05-JAN-1987 17:30
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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 *PowerRational(pDst,pSrc,m,n)
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DEC *pDst, *pSrc;
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int m,n;
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{
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DEC temp, *pt, *nsrc, dnsrc, ddm, *dm=&ddm;
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int i, isn=0;
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_MacStart(GM_DPOWRAT);
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_MacInVarD(pSrc);
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_MacOutVarD(pDst);
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if (n == 0) {
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_MacErr(GM_DIV0);
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_MacRet(GM_NULL);
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}
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if (_MacIsDecZ(pSrc)) {
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if (!((m<0)^(n<0))&&(m!=0)) {
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_MacDZero(pDst);
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_MacRet(pDst);
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}
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else {
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_MacErr(GM_PWR0);
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_MacRet(GM_NULL);
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}
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}
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if (m == 0) {
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_MacDCopy(pDst,&decOne);
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_MacRet(pDst);
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}
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if (_MacIsDecN(pSrc)) {
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while ((m % 2) + (n % 2) == 0) {
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m=m/2;
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n=n/2;
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}
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if ((n % 2) == 0) {
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_MacErr(GM_IMAG);
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_MacRet(GM_NULL);
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}
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isn=m % 2;
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nsrc = &dnsrc;
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_MacDCopy(nsrc,pSrc);
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pSrc=nsrc;
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_MacDChgs(nsrc);
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}
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pt = &temp;
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(void) _LnDec80Bit(pt, pSrc);
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(void) ConvLongToDecimal(dm, (long) m);
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(void) _MulDec80Bit(pt, pt, dm);
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(void) ConvLongToDecimal(dm, (long) n);
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(void) _DivDec80Bit(pt, pt, dm);
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i = _ExpDec80Bit(pt, pt);
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if(i==GM_OVERFLOW) {
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_MacErr(i);
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_MacRet(GM_NULL);
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}
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i = _Sq5UnsTo4Uns(pt);
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if(i!=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(pt)) {
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_MacErr(GM_UNDERFLOW);
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}
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if (isn)
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_MacDChgs(pt);
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_MacDCopy(pDst,pt);
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_MacRet(pDst);
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}
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