Re: Procedure parameter with VALUE option

[boldt@xxxxxxxxxx]

John wrote:
>Two questions;
>1.
>My understanding is if passed by Value and the procedure Does modify the
>passed parameter
>the Caller doesn't see the change.    Is that correct?
>Is it also correct for CONST ?

I believe someone else answered this.  You can change the value
of a VALUE parameter within the procedure and the change will not
be reflected in the caller's code.  Indeed, since you can pass
literals as VALUE parameters, changing the value of the passed
parameter would not be a good idea.

CONST parameters cannot be changed within the procedure.  This
rule is enforced by the compiler, even to the extent that you
cannot save the address of a CONST parameter.  (Note:  As of
V5R1, you can test if the %ADDR() of a CONST parameter is *NULL,
but you just can't save that value.)

>2.
>Are you saying that in V5R1 my return variable can be defined
>(LIKEDS) like an Externally Defined D/S ?

Yes, you can define something LIKEDS an extdesc DS.

>
>So if I can now return (in essence) an Externally Defined D/S,
>Can I get the Ext D/S  covered in my DSPPGMREF command, can I huh ?
>Can I ?  Huh?

It's on the "proposed enhancements" list.

>
>Can you make sure that both Caller/Callee use the same D/S definition?

If a prototype definition includes something (parameter or return
value) defined LIKEDS some data structure, the DS definition should
be coded in the same /COPY member as the prototype.  Thus, when that
/COPY member is included in some source file, you know that both
will be in synch.  To indicate that the DS definition is a
"template", define it as BASED(@).  This is sort of like a
"typedef" in C.

Cheers!  Hans

Hans Boldt, ILE RPG Development, IBM Toronto Lab, boldt@ca.ibm.com