Procedure pointers - can I do this??

[Igor.Beslic@xxxxxxxxxxxx]

I have some idea of creating RPG modul that will simulate something what 
is in object oriented programing known as an Interface object. The MODUL 
should implement parser for specific kind of markup language files 
(similar to SAX parser).
 
The idea is next:
Modul A has subProcedures initalize() - Exported, startProcess() - 
Exported and its global variables var1,var2...varN that are known at 
compile time and handleEvent(), errorRecover() that are referencing on 
some procPtrs which should be defined when subprocedure initalize() is 
called (run time). Code should look like this:
*------------------------------------MODUL A ________START
D initalize                PR
D  proc1Pointer     *  ProcPtr VALUE
D  proc2Pointer     *  ProcPtr VALUE

D startProcess      PR

D Var1
D Var2
D Var3
....
D VarN

D handleEvent     PR         ExtProc(PointerToMe1)
D errorRecover   PR         ExtProc(PointerToMe2)
.....
P initalize               B         Exported
D initalize               PI
D  proc1Pointer     *  ProcPtr VALUE
D  proc2Pointer     *  ProcPtr VALUE
/free
 PointerToMe1=proc1Pointer;
 PointerToMe2=proc2Pointer
 return;
/end-free
P initalize              E

P startProcess   B Exported
  //do something....
  dow 
        if exception;
                //call procedure but what will
                //it do will be known at run time
                errorRecover();
        EndIf;
        If dataReady;
                //call procedure but what will
                //it do with data will be known at run time
                handleEvent();
        EndIf; 

  EndDo
P startProcess   E
*---------------------------------------MODUL A_____________END



Modul B has subProcedures mainSubp(), supp1(), subp2() and two special 
subp myEventHandler(), myErrorHandler() whose proc pointers should be 
passed to modulA:
*----------------------------------------MODUL B_____________START
D mainSubP      PR
D subp1                 PR
D subp2 PR
D myEventHandler PR
D myErrorHandler   PR
....

P mainSubP      B
/free
//initalize MODUL A
 initalize(%PAddr('myEventHandler'):%PAddr('myErrorHandler'));
//prepare MODUL B
subp1();
subp2();
//start procession in MODUL A
startProcess();
/end-free
P mainSubP        E

....

P myEventHandler   B
   //here is implementation which will depend on END programers idea
P myEventHandler  E

P myErrorHandler B
   //here is error recovery
P myErrorHandler E

*----------------------------------------MODUL B_____________END


The Sourcers guide to RPG has just one trivial example with procedure 
pointers which couldn't give me all the answers.
Here is list of questions so if you know help me:

1. What is SCOPE  of myEventHandler and myErrorHandler??? I mean, can I 
manipulate with Var1, Var2 ... VarN from MODUL A if subp implementation is 
in ModulB

2. If I can't acess VAR1, VAR2... VarN has anyone any IDEA how to make 
them accessible??? EXPORT them (how can I do that???) or to define 
USERSPACE that will hold neaded data and would be visible in MODULE B and 
MODUL A???

3. If I want to write to PF named logPF in myEventHandler where should I 
define that file in MODUL A or MODUL B??? (My Idea is that file is defined 
in MODUL B so the interface could be more flexible)

4. Is there any literature/link/book/pdf which describes procedure 
pointers more detailed than Sourcers guide???



Thank you all!

Igor Bešlić, dipl. ing. rač. 
VOLKSBANK d.d.
OJ Informatika
Zelinska 2, 10000 Zagreb
tel: +385 1 6326422