Re: Recursion in RPG

Isn't there a call stack limit for jobs that would prevent infinite recursion loops anyway?

I think there's a limit in SQL, but the shop where I currently work has has a standard that bans doing any recursion in SQL. I assume there is a similar standard for RPG, but haven't had occasion to ask, but I have never had a situation that seemed to need it. I can't help but think there would almost always an alternative involving a loop of some kind.

Where you have such a thing, seems to me you could handle it by "stacking" your state (or "deepness") to variables in storage, without having to call your same procedure. Recursion might simplify it but it never seemed "right" to me anyway. Even bills of materials is a matter in my opinion of indexing "stacks" of data, and looping up and down therein. Presumably that's the way compiled code handles recursive procedures anyway, including in object oriented program languages.

---Alan


On 2/14/13 5:24 PM, Rory Hewitt wrote:

I would assume that there *is* a recursion limit, even if it could never
realistically be reached - there has to be a variable somewhere in the
runtime process which keeps track of the current recursion number, and that
variable will eventually overflow. But by that point, chances are the total
memory limit would have been reached.

In one of my recursion processes where I was worried about limits, I set a
global MaxRecurse variable prior to calling the recursive procedure for the
first time, and the procedure increments a global CurrRecurse variable
(also initialized at the start), and compares to MaxRecurse and drops out
if it's gone 'too deep'... Not hard to do.


On Thu, Feb 14, 2013 at 2:32 PM, Buck Calabro <kc2hiz@xxxxxxxxx> wrote:

On 2/14/2013 5:27 PM, Scott Klement wrote:

Hmmm... well, why would there be a hard number? Seems to me, the nature
of a call stack would lend itself to something that doesn't have a hard
number of entries, but rather, a memory limit.

On 2/14/2013 4:21 PM, Buck Calabro wrote:

No wonder Chuck couldn't find a hard number. There does not appear to
be one. The same verbiage is in the 5.4 Reference as well as 7.1.
--buck

Good question! Similar to maximum CPU time used, or maximum DASD used,
an OS might choose to restrict a process to a maximum number of recursions.
--buck

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