ba237a9d91
Files correlati : Ricompilazione Demo : [ ] Commento : Aggiunti i sorgenti per Greenleaf Math Library (gfm.dll) git-svn-id: svn://10.65.10.50/trunk@10079 c028cbd2-c16b-5b4b-a496-9718f37d4682
114 lines
2.2 KiB
C
Executable File
114 lines
2.2 KiB
C
Executable File
/* int _ExpDec80Bit(pDst,pSrc)
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*
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* ARGUMENT
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* DEC *pDst, *pSrc;
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*
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* DESCRIPTION
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* Calculates e^pSrc, stores result in pDst.
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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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* GM_SUCCESS if calculation is successful,
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* otherwise the error code (which could be underflow)
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*
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* ALGORITHM
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* pSrc = a * ln 2 + b |b| < (ln 2) / 2
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* e^pSrc = (2^a) * (e^b)
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* Using the Taylor series,
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* e^b = 1 + b + (b^2)/2! + (b^3)/3! + ...
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*
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* AUTHOR
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* Jared Levy April 7, 1987
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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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int _ExpDec80Bit(pDst,pSrc)
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DEC *pDst, *pSrc;
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{
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int a, i;
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DEC da, dpow2, db, dt, dfact, dterm;
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DEC *pow2, *b, *fact, *pt, *term;
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if (CompareDecimal(pSrc,&decMaxExp) == 1) {
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return(GM_OVERFLOW);
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}
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if (CompareDecimal(pSrc,&decMinExp) == -1) {
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_MacDZero(pDst);
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return(GM_UNDERFLOW);
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}
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/* calculate a = pSrc * (1/(ln 2)) */
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(void) _MulDec80Bit(&da, pSrc, &decReciprocalOfLn2);
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(void) _ScaleDec80Bit(&da,&da,0);
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a = ConvDecimalToInt(&da);
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/* calculate b = pSrc - a * ln 2 */
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b=&db;
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if (a == 0) {
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_MacDCopy(b,pSrc);
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}
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else {
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(void) _MulDec80Bit(&dt, &da, &decLn2);
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(void) _SubDec80Bit(b, pSrc, &dt);
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}
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/* calculate pSrc = (2^a) * (e^b) */
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fact = &dfact;
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pt = &decOne;
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term = &dterm;
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_MacDCopy(fact,pt);
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_MacDCopy(pDst,pt);
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_AddDec80Bit(pDst, pDst, b);
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_MacDCopy(term, b);
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do {
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/* calulate next term */
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fact->dc.sl[0]++;
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(void) _MulDec80Bit(term, b, term);
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(void) _DivRndDec80Bit(term, term, fact, 23);
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/* add term to series */
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(void) _AddDec80Bit(pDst, pDst, term);
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/* calc next factorial term in divisor */
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} while (!(_MacIsDecZ(term)));
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if (a>0) {
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pow2 = &dpow2;
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/*
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* I used to use the _MacDZero statement here, but Lattice C 6.0
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* pointed out that it had a single redundant line in the
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* macro, so I expanded it and remove the redundant line.
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* _MacDZero(pow2);
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*/
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pow2->dc.attr=0;
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pow2->ls.lsl[0]=0;
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pow2->ls.lsl[1]=0;
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pow2->dc.msd=0;
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pow2->dc.id = 0;
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pow2->dc.sl[a/16] = 1 << (a % 16);
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i =_MulDec80Bit(pDst, pDst, pow2);
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return(i);
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}
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while (a<0) {
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_HalveUnsArr(pDst->dc.sl, 5);
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a++;
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}
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if (_MacIsDecZ(pDst))
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return(GM_UNDERFLOW);
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return(GM_SUCCESS);
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}
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