RE: RPG - conversion vs re-write

["Hans Boldt" <hboldt@xxxxxxxxxxxx>]

Bob Cozzi <BobCozzi@ibm.net> wrote:
>We do NOT have null values in dates, or any other fields. There is a NULL
>INDICATOR, however.
>
>A really sucky implementation of nulls. You set ON a %NULLID(myDateFld)
>flag and then test if it's equal to ON. The date field can contain only
>valid dates, but the null indicator can be on or off.  I am very
>disappointed in this implementation. ;-(

Bob:  There's nothing wrong with the implementation of null-capable
fields in RPG.  I have my concerns about the design, but the
implementation is just fine!

Actually, my concern with the design is that we did not go far enough
in supporting the concept.  (And perhaps someday, we'll provide a full
support for null fields.)

But I suspect that that's not what you are complaining about.  Is it
that you don't like the whole concept of what a null-capable field really
is?  As you know (or should know), the "nullness" of a field is not a
value of the field, but rather, some sort of dynamic attribute of the
field.  It is an indication of the presence or absence of data within
that field.  That guided our design of %NULLIND in RPG.  We did not
want to "nullify" a null-capable field by allowing something like *NULL
to be assigned to it.  *NULL is a value, and not an attribute.  %NULLIND
emphasizes the point that nullness is an attribute, and is independent
of the actual data.

Cheers!  Hans

Hans Boldt, ILE RPG Development, IBM Toronto Lab, hboldt@vnet.ibm.com

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