RE: Free format question on D specs

I personally don't think we'll ever see a completely new version of RPG. I expected incremental improvements forever.



-----Original Message-----
From: John Yeung [mailto:gallium.arsenide@xxxxxxxxx]
Sent: Friday, February 01, 2019 8:53 AM
To: RPG programming on the IBM i (AS/400 and iSeries) <rpg400-l@xxxxxxxxxxxxxxxxxx>
Subject: Re: Free format question on D specs

On Thu, Jan 31, 2019 at 5:27 PM Barbara Morris <bmorris@xxxxxxxxxx> wrote:

The compiler code for scanning free-form definitions is almost all the
same as for fixed-form code, and there are a few things available in
fixed form columns that the compiler needs so it knows which direction
to take.

It's a fascinating glimpse into language design and compiler design.

Has there been any thought given to the idea of an RPG V? It would a great opportunity to completely exorcise fixed-form, and maybe rework some things so that the language is more maintainable and extensible.
(That latter thing is just a pure guess on my part. I have zero actual knowledge of RPG internals.)

The compiler takes completely different paths for externally-described
vs program-described data structures, so it needs to know right away
what it's dealing with.

Could the scanner not incorporate some amount of look-ahead (i.e., put off some decisions until more information has been scanned)? I mean, some keywords *can* be moved around, both in fixed and free, so....

Earlier you said the free-form scanner code is "almost the same" as the fixed-form scanner code. Why almost? Why isn't there a single codebase which serves both? If they are separate anyway, why couldn't the free-form scanner be made deliberately less similar? (And again, maybe this is something for RPG V.)

Please don't take this as grilling. It's more just musing. I have incredible respect for language designers and implementers, and in particular for those who have worked or are still working on RPG.

John Y.