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Status Not under consideration
Workspace IBM i
Categories Languages - RPG
Created by Guest
Created on May 6, 2021

Count recursive calls (all/direct)

Requesting a built in function to recognize if a proc was called recursively with a parameter to recognize if it was called by itself. Ex:
dcl-proc chkRecursion;
dcl-pi chkRecursion end-pi;
count = %recursion();
countDirect = %recursion( *on );
if count > 9;
return;
elseIf count > *zero and %rem( count : 3 ) = *zero;
otherProc();
else;
chkRecursion();
endIf;
return;
end-proc;

I hope I made the code reasonable enough to understand my point.
Imagine otherProc calls chkRecursion, too.
On the second recursive call, both count and countDirect would be 2. On third recursive call after otherProc calls chkRecursion, then count should be 3 where countDirect would be zero.


Use Case:

Recognize recursive calls. At my company we have a proc that processes active issues against an entity. A decision was made to process resolved issues in the same manner, but only after active issues are checked. The new BIF would allow me to check if the the proc is on an initial run or recursive run and if it was called by itself. Also, while coding the changes I almost coded infinite recursion. Having the BIF return a count instead of a boolean value will help safeguard infinite runs.


Idea priority Low
  • Guest
    Reply
    |
    Aug 31, 2021

    IBM does not intend to provide a solution to this request at this time, so it is being closed.

    While IBM recognizes that this feature would be useful, it is not feasible to implement it reliably in all cases.

    Consider using one of the following mechanisms to implement this with current RPG coding:

    1. Call the QWVRCSTK API to check the program stack as suggested in the comments. Using this mechanism would allow you to detect whether the recursive call is a direct call.

    2. Add your own counter in the procedure, defined with the STATIC keyword so the same variable is used by all invocations of the procedure. Increment the counter when the procedure starts, and decrement it when the procedure ends. To ensure that the counter is always decremented, put the statement to decrement the counter into the ON-EXIT section for the procedure.

    dcl-proc p1;
    dcl-s active_calls inz(1) static;

    active_calls += 1;
    ...

    on-exit;
    active_calls -= 1;
    end-proc;

  • Guest
    Reply
    |
    May 8, 2021

    You can check this with the following API/SQL function; https://www.ibm.com/docs/api/v1/content/ssw_ibm_i_74/apis/qwvrcstk.htm