Re: Updated C2N and CharToNum procedures

["Leif Svalgaard" <leif@xxxxxxxx>]

Hans,
I missed the floating point detail. I guess I was thinking of the
"atop" function.

----- Original Message -----
From: <boldt@ca.ibm.com>
To: <MIDRANGE-L@midrange.com>
Sent: Tuesday, July 04, 2000 9:19 AM
Subject: Re: Updated C2N and CharToNum procedures


>
>
> Leif wrote:
> >>  >   **   NumVal = atof('1234.56') // result is NumVal=1234.56
> >> Bob:  I don't mean to nitpick, but the statement
> >> "NumVal = atof('1234.56')" returns the value 1234.55, not 1234.56.
> >
> >-----
> >You got to be kidding. Explain the rationale for that one.
>
> Not kidding.  Try it yourself.  The inaccuracies (and
> associated dangers) involved with floating point data
> type are well-known to those who use floating point.
>
> In this case, atof('1234.56') returns a long float
> value of +1.234559999999999E+003.  When this value is
> converted to packed decimal, you get 1234.55.
>
> If you want a more useful answer, use half-adjust when
> assigning the float value to a decimal variable.
>
> Also be aware that long float only gives you about 16
> digits of real precision.  If you want to move a large
> float value to a large packed variable with more than
> 16 digits, the lower-order digits in the packed
> variable cannot be trusted.
>
> The lesson is:  Be very careful when using float.  In
> particular, avoid float for monetary values.  Normally
> avoiding float is no big deal, but note that the **
> operator in RPG IV returns a float value.  Also, any
> time you introduce float data type in an expression,
> subsequent operations in that expression happen in
> float format.  Since ** is useful in certain monetary
> calculations, be careful how you structure your code.
>
> (Floating point is commonly used for scientific
> calculations (especially in physics) where you're
> doing good if you have 3 or 4 significant digits.)
>
> Cheers!  Hans
>
> Hans Boldt, ILE RPG Development, IBM Toronto Lab, boldt@ca.ibm.com
>
>
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