90 lines
6.1 KiB
Plaintext
90 lines
6.1 KiB
Plaintext
/*
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* File......: D2E.PRG
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* Author....: Gary Baren
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* CIS ID....: 75470,1027
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*
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* This is an original work by Gary Baren and is hereby placed in the
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* public domain.
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*
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* Modification history:
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* ---------------------
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*
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* Rev 1.2 15 Aug 1991 23:05:02 GLENN
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* Forest Belt proofread/edited/cleaned up doc
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*
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* Rev 1.1 14 Jun 1991 19:51:24 GLENN
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* Minor edit to file header
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*
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* Rev 1.0 09 Jun 1991 00:27:06 GLENN
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* Initial revision.
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*
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*/
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/* $DOC$
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* $FUNCNAME$
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* FT_D2E()
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* $CATEGORY$
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* Conversion
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* $ONELINER$
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* Convert decimal to scientific notation
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* $SYNTAX$
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* FT_D2E( <nDec>, <nPrecision> ) -> <cNumE>
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* $ARGUMENTS$
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* <nDec> Decimal number to convert
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*
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* <nPrecision> Number of decimal places in result.
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* Defaults to 6 decimal places.
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* $RETURNS$
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* <cNumE> A string representing a number in
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* scientific notation
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* $DESCRIPTION$
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* Given a decimal number and the desired precision,
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* a string representing the equivalent in scientific
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* notation is returned.
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* $EXAMPLES$
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* ? FT_D2E( 12.345, 2 )
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* -> 1.23E1
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*
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* ? FT_D2E( -12.345, 3 )
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* -> -1.235E1
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*
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* ? FT_D2E( 0.00000543, 2 )
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* -> 5.43E-6
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* $SEEALSO$
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* FT_E2D()
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* $END$
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*/
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#define log10( num ) log( num ) / log( 10 )
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#define DEFAULT_PRECISION 6
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#command DEFAULT <p> TO <val> => <p> := iif( <p> == NIL, <val>, <p> )
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#ifdef FT_TEST
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function main( cNum, cPrec )
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DEFAULT cPrec TO str( DEFAULT_PRECISION )
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return qout( ft_d2e( val(cNum), val(cPrec) ) )
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#endif
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function ft_d2e( nDec, nPrecision )
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local nExp, sScn
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DEFAULT nPrecision TO DEFAULT_PRECISION
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if nDec == 0
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nExp := 0
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elseif abs( nDec ) < 1
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nExp := int( log10( nDec ) ) - 1
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else
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nExp := int( log10( abs(nDec)+0.00001 ) ) && 0.00001 == kludge
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endif && for imprecise logs
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nDec /= 10 ^ nExp
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if round( abs(nDec), nPrecision ) >= 10
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nDec /= 10
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nExp++
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endif another kludge for stuff like '999999999'
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sScn := ltrim( str( nDec, nPrecision + 3, nPrecision ) )
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return( sScn + 'E' + alltrim( str( nExp, 5, 0 ) ) )
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