Re: Why you shouldn't be afraid to use VARCHAR in RPGLE

Thanks Barbara. Nothing better than explanations coming from the creators
of the compiler. Of course you guys know what all that means and your
contributions will always be appreciated.

BTW, I have wondered a lot why you guys have not yet implemented the C-like
expression as:
boolVal = (a = b ? 0: 1);
This is not only necessary for modern RPG but it should have been provided
long time ago! :-)
JS

El mié, 10 dic 2025 a las 22:04, Barbara Morris (<bmorris@xxxxxxxxxx>)
escribió:

On 2025-12-10 12:25 p.m., James H. H. Lampert via RPG400-L wrote:

On 12/10/25 4:06 AM, Infodorado InfoDorado via RPG400-L wrote:

The RPG compiler is a single-pass compiler

No, it can't be pure single-pass. If it were, then a program in which a
variable is NOT defined in a D-spec, nor in the first C-spec in which it
appears, would not compile, much less run. And it's trivially simple to
construct an example of this (it took me about 2 minutes), and it
compiles and runs just fine. I'd quote the source here, but it would
likely be mangled beyond recognition.

It's a single pass through the source but it gathers information that it
can use multiple times.

The compiler usually allows forward-referencing, so you can code LIKE(x)
where x is defined later.

But for free-form definitions, the compiler requires the parameter for
the data-type keywords to be defined before the keyword is seen.

dcl-s x char(con1); // bad, con1 not defined yet
dcl-c con1 5;
dcl-s y char(con1); // ok, con1 is defined

Where it becomes extra fun is when you have a data structure that LOOKS
defined.

dcl-ds ds1;
subf char(10);
end-ds;
dcl-s x char(%size(ds1)); // %size(ds1) is not defined. WHAT???

RPG allows you to define the length of a data structure later, either
due to being on an I spec, possible an externally-described I spec, or
on a C spec.

C MOVE *blanks ds1 50

Almost certainly wrong columns, but you get what I mean. I'm defining
DS1 to have a length of 50 here, not the length of 10 that it looked
like it should have. Shenanigans? Yep, but upward-compatible R Us.

We have a H-spec/CTL-OPT keyword for that: DLCOPT(*NOCHGDSLEN). With
that keyword, the compiler doesn't allow you to change the length of the
data structure like that, so it's considered defined as soon as all the
subfields are defined.

--
Barbara

--
This is the RPG programming on IBM i (RPG400-L) mailing list
To post a message email: RPG400-L@xxxxxxxxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: https://lists.midrange.com/mailman/listinfo/rpg400-l
or email: RPG400-L-request@xxxxxxxxxxxxxxxxxx
Before posting, please take a moment to review the archives
at https://archive.midrange.com/rpg400-l.

Please contact support@xxxxxxxxxxxxxxxxxxxx for any subscription related
questions.