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
84 lines
1.9 KiB
C
Executable File
84 lines
1.9 KiB
C
Executable File
/* void _ATanDec80Bit(pDst,pSrc)
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*
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* ARGUMENT
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* DEC *pDst;
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* DEC *pSrc;
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*
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* DESCRIPTION
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* Sets pDst = the arctangent (in radians) of pSrc,
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* which always lies between -pi/2 and pi/2.
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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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* None. (always successful)
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*
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* AUTHOR
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* Jared Levy Aug 7, 1987
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* Copyright (C) 1987-1990 Greenleaf Software Inc. All rights reserved.
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*
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* ALGORITHM
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* For x < 0, atan(x) = - atan(-x)
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* For x > 1 atan(x) = pi / 2 - acot(x) = pi / 2 - atan(1 / x)
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* atan(x) = pi / 6 + atan [ (x - 1/3^.5) / (1 + x/3^.5) ]
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* atan(x) = x - x^3/3 + x^5/5 - ...
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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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void _ATanDec80Bit(pDst,pSrc)
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DEC *pDst;
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DEC *pSrc;
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{
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int isn=0, isrecip=0;
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DEC *nsrc, dnsrc, *x, dx, *xsq, dxsq, *xpow, dxpow;
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DEC *term, dterm, *fact, dfact;
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DEC *num, dnum, *den, dden, *temp, dtemp;
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nsrc = &dnsrc;
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_MacDCopy(nsrc, pSrc);
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if (_MacIsDecN(nsrc)) {
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isn = 1;
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_MacDChgs(nsrc);
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}
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if (CompareDecimal(nsrc,&decOne) == 1) {
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isrecip = 1;
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(void) _DivRndDec80Bit(nsrc, &decOne, nsrc, 23);
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}
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(void) _SubDec80Bit(num = &dnum, nsrc, &decReciprocalOfSqrt3);
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(void) _MulDec80Bit(temp = &dtemp, &decReciprocalOfSqrt3, nsrc);
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(void) _AddDec80Bit(den = &dden, temp, &decOne);
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(void) _DivRndDec80Bit(x = &dx, num, den, 23);
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(void) _MulDec80Bit(xsq = &dxsq, x , x);
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(void) _MulDec80Bit(xpow = &dxpow, xsq, x);
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_MacDCopy(pDst, x);
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(void) ConvLongToDecimal(fact = &dfact, 3L);
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(void) _DivRndDec80Bit(term = &dterm, xpow, fact, 23);
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while (!_MacIsDecZ(term)) {
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if ((fact->dc.sl[0] % 4) == 1)
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(void) _AddDec80Bit(pDst, pDst, term);
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else
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(void) _SubDec80Bit(pDst, pDst, term);
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fact->dc.sl[0]+= 2;
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(void) _MulDec80Bit(xpow, xpow, xsq);
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(void) _DivRndDec80Bit(term, xpow, fact, 23);
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}
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(void) _AddDec80Bit(pDst, &decPiOver6, pDst);
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if (isrecip)
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(void) _SubDec80Bit(pDst, &decPiOver2, pDst);
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if (isn)
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_MacDChgs(pDst);
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}
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