RE: CL pgm and pointer variables -- RPG400-L

Apparently our e-mail system had a problem with a clogged queue.  Part of
the fallout was duplicate messages.  They tell me it's fixed now.

Sorry.

> -----Original Message-----
> From: Joel Fritz
> Sent: Thursday, November 21, 2002 9:13 AM
> To: 'rpg400-l@midrange.com'
> Subject: RE: CL pgm and pointer variables
>
>
> I was trained as a C programmer, although I haven't used it
> in almost ten
> years.  Pointers are necessary in C because there's no
> passing by reference,
> for support of dynamic memory allocation, and the way that arrays are
> defined.  There's a lot of cool things you can do with
> pointers like direct
> access to hardware if the OS permits it.  By allocating memory to a
> void--typeless--pointer and then type casting it, you can do
> darned near
> anything, just like an RPG pointer.   It's interesting that one of the
> features of C++ is reference variables.
>
> IMHO, there is very little need for pointers in business application
> programming in RPG.  There are some situations where dynamic memory
> allocation makes sense, and you may need them for some API
> calls.  Mind you,
> I'm willing to sacrifice some performance for
> maintainability.  I think
> they're nice to have, but should be used when they're the
> only reasonable
> option for solving a problem.
>
>
> > -----Original Message-----
> > From: Hans Boldt [mailto:boldt@ca.ibm.com]
> > Sent: Thursday, November 21, 2002 7:26 AM
> > To: rpg400-l@midrange.com
> > Subject: Re: CL pgm and pointer variables
> >
> >
> > Booth wrote:
> >  > Wouldn't an even easier solution to these inherent
> >  > problems with pointers be to just not use pointers?
> >
> > To which Rob answered:
> > > Wouldn't an easy solution to divide-by-zero errors
> >  > be to just not use division?
> >
> > Yes, that would in fact be acceptable. As those who've used division
> > in RPG expressions have learned (sometimes the hard way), it is
> > sometimes best to avoid division in expressions if at all possible.
> >
> > ;-)
> >
> > I do see your point, though. Why avoid something just because it is
> > potentially troublesome? The difference here is that when you have a
> > problem with division, you can normally easily locate the bug to the
> > appropriate expression.
> >
> > On the other hand, pointer bugs can often be very difficult to trace
> > down. For example, let's say you DEALLOC some piece of storage, but
> > somewhere else you still have a pointer pointing at that piece of
> > storage. Since that storage may then be returned on subsequent
> > %ALLOC operations, unpredictable results can happen when accessing
> > data through the original pointer, or worse, when the storage is
> > changed using the original pointer. Even worse, the problems can
> > often *seem* to disappear just by changing one seemingly unrelated
> > thing.
> >
> > I can attest to the problems you can have with pointers from my own
> > experience with the ILE RPG compiler, and that's using a language
> > with strong type checking of pointers! With untyped pointers (as in
> > RPG), the potential problems are much worse. At first glance,
> > debugging pointer problems can seem unsurmountable. Even at second
> > or third glance!
> >
> > Cheers!  Hans
> >
> >
> >
> > _______________________________________________
> > This is the RPG programming on the AS400 / iSeries (RPG400-L)
> > mailing list
> > To post a message email: RPG400-L@midrange.com
> > To subscribe, unsubscribe, or change list options,
> > visit: http://lists.midrange.com/cgi-bin/listinfo/rpg400-l
> > or email: RPG400-L-request@midrange.com
> > Before posting, please take a moment to review the archives
> > at http://archive.midrange.com/rpg400-l.
> >
> NOTICE:
> All e-mail sent to or from this e-mail address will be
> received or otherwise
> recorded by The Sharper Image corporate e-mail system and is
> subject to
> archival, monitoring, review by and/or disclosure to Sharper
> Image security
> and other management. This message is intended only for the use of the
> addressee and may contain information that is privileged and
> confidential.
> The contents of this message may contain personal views which
> are not the
> views of The Sharper Image. If you are not the intended recipient,
> dissemination of this communication is prohibited.
> _______________________________________________
> This is the RPG programming on the AS400 / iSeries (RPG400-L)
> mailing list
> To post a message email: RPG400-L@midrange.com
> To subscribe, unsubscribe, or change list options,
> visit: http://lists.midrange.com/cgi-bin/listinfo/rpg400-l
> or email: RPG400-L-request@midrange.com
> Before posting, please take a moment to review the archives
> at http://archive.midrange.com/rpg400-l.
>
NOTICE:
All e-mail sent to or from this e-mail address will be received or otherwise
recorded by The Sharper Image corporate e-mail system and is subject to
archival, monitoring, review by and/or disclosure to Sharper Image security
and other management. This message is intended only for the use of the
addressee and may contain information that is privileged and confidential.
The contents of this message may contain personal views which are not the
views of The Sharper Image. If you are not the intended recipient,
dissemination of this communication is prohibited.