Re: Updated C2N and CharToNum procedures

Hi Leif,

Where's the "atop" (is that ascii-to-packed?) function? I just checked IBM's
C Library Reference and ILE C Reference manuals and I don't see it.

TIA

Peter Dow
Dow Software Services, Inc.
909 425-0194 voice
909 425-0196 fax


----- Original Message -----
From: Leif Svalgaard <leif@leif.org>
To: <MIDRANGE-L@midrange.com>
Sent: Tuesday, July 04, 2000 7:34 AM
Subject: Re: Updated C2N and CharToNum procedures


> 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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