57 lines
1.0 KiB
C
57 lines
1.0 KiB
C
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/* void _CosDecSmall(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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* Sets pDst = cos(pSrc), where 0 <= pSrc < pi / 4.
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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.
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*
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* ALGORITHM
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* Using the Taylor series,
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* cos(x) = 1 - x^2/2! + x^4/4! - ...
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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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void _CosDecSmall(pDst,pSrc)
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DEC *pDst, *pSrc;
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{
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DEC *srcsq, dsrcsq, *term, dterm, *fact, dfact;
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SHORT i;
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srcsq = &dsrcsq;
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(void) _MulDec80Bit(srcsq, pSrc, pSrc);
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(void) ConvLongToDecimal(pDst, 1L);
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term = &dterm;
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(void) _MulDec80Bit(term, srcsq, &decPoint5);
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i = 2;
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fact = ConvLongToDecimal(&dfact, 6L);
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while (!(_MacIsDecZ(term))) {
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if ((i % 4) == 0)
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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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i+=2;
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_MulDec80Bit(term, term, srcsq);
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fact->dc.sl[0] = i * (i - 1);
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_DivRndDec80Bit(term, term, fact, 23);
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}
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}
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