Re: Recursion in RPG

Hi Phil,

The authors statement that you cite (about RETURN) doesn't make any sense. Just because you write it in an article doesn't mean you're right! (Lord knows I've made mistakes in articles!)

Anyway, whether or not he has a RETURN statement there will not make any difference at all. It will still go to the ENDIF line of the preceding call stack entry after the RETURN. And yes, that's the expected behavior. If it didn't work that way, I wouldn't call it recursive!

As for system limits -- the big one I've run into is the maximum amount of automatic storage allowed in the single-level storage model. You can only (approx) 16 mb of automatic storage for the entire call stack -- that's all procedures added together! This can be "solved" by using STGMDL(*TERASPACE)

I'm not aware of any other limits.

In my opinion, the article you cite does not provide a good example of recursion, or explain why you'd want to use it. Seems to me his example would make more sense if it was just run in a loop instead of run recursively. Recursion only comes up occasionally in business programming. Something like a bill of materials is an example where recursion makes sense... but aside from that, recursion is pretty rare in business programming.


On 2/14/2013 12:50 PM, ssc1478 wrote:

I recently read this article:
http://ibmsystemsmag.com/ibmi/developer/rpg/rpgle_recursion/

and was interested in this comment:
"Even though this procedure doesn’t return a value, it’s a good idea to
have a return statement on the end so the program can exit right away after
it reaches the end of MGACCM. Otherwise, it will unwind itself by going
from the Endif line to the end of the procedure for as many records as were
written."

What I've noticed is that each recursive call puts an entry on the call
stack, and at the end it "unwinds" down the call stack until it can exit
the subprocedure. I thought the author's comment above was addressing
that, but it made no impact on my test pgm.

Is that the expected behavior? I'm worried about a long-running job
running into a system limit. Does anyone know?

Thanks,
Phil