Re: RFE for your consideration -- RPG400-L

Yes, I could, but that requires the Proc Pointer to be stored in the global space, and rather than using the pointer in my local procedure to execute the callback, I have to assign it to the global pointer. Obviously not onerous, just would be convenient to not have to do that, and you still have the issue that the Procedure interface on the callback can't use the prototype because a procedure can't be defined for a prototype when ExtProc is being used. The actual message is RNF1505 A procedure cannot be defined when the prototype specifies EXTPROC(variable) or EXTPGM. Maybe the real fix is to allow a procedure to be defined when the prototype specifies ExtProc(variable).

Mark Murphy
Atlas Data Systems
mmurphy@xxxxxxxxxxxxxxx

-----Jon Paris <jon.paris@xxxxxxxxxxxxxx> wrote: -----
To: Rpg400 Rpg400-L <rpg400-l@xxxxxxxxxxxx>
From: Jon Paris <jon.paris@xxxxxxxxxxxxxx>
Date: 12/15/2016 04:25PM
Subject: Re: RFE for your consideration

If there needs to be debate on this Mark we can continue over on the RFE site itself but ... the question that popped into my head was why not include a proc pointer definition in the /Copy for the proto?

Jon Paris

www.partner400.com
www.SystemiDeveloper.com

On Dec 15, 2016, at 3:36 PM, Mark Murphy/STAR BASE Consulting Inc. <mmurphy@xxxxxxxxxxxxxxx> wrote:

I added a new RFE to add procedure templates to RPG. Here is my justification:

When creating a prototype that references a procedure via Procedure pointer the prototype can not be used on both the caller and the callee side of the call. The caller needs a procedure pointer in the ExtProc keyword, and it must be in the same scope as the pointer or you will get compile errors. If you try to use the same prototype in the module with the procedure interface, the pointer does not exist, and you have compile issues. So when using procedure pointers, you have to have multiple definitions of the same prototype which introduces the opportunity for errors and mismatches. It would be nice if I could define a procedure template for these situations. The template could sit in the copybook containing my other prototypes, and then I could define local prototypes as necessary against it with something LikeProc. Or they could opt to remove ExtProc from the prototype or allow some sort of local override by defining a local prototype LikePR and allowing that prototype t

have the ExtProc with the procedure pointer. Now that I am thinking about it, that is probably the best option so a plain prototype sits in my copy book to be used by procedure interfaces or calls that do not need a procedure pointer, and a prototype that needs a procedure pointer is defined with LikePR and allows ExtProc() with a procedure pointer.

Why use procedure pointers in the first place? They are the key to the callback pattern. Since functions aren't first class objects in RPG, I need to pass a procedure pointer instead of a procedure if I want an abstraction that needs some local help in the form of a callback.

http://www.ibm.com/developerworks/rfe/execute?use_case=viewRfe&CR_ID=98662

Mark Murphy
Atlas Data Systems
mmurphy@xxxxxxxxxxxxxxx
--
This is the RPG programming on the IBM i (AS/400 and iSeries) (RPG400-L) mailing list
To post a message email: RPG400-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/mailman/listinfo/rpg400-l
or email: RPG400-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at http://archive.midrange.com/rpg400-l.

Please contact support@xxxxxxxxxxxx for any subscription related questions.

Help support midrange.com by shopping at amazon.com with our affiliate link: http://amzn.to/2dEadiD