Re: Another ILE question : CONST vs VALUE

6 months later I've found an example to reply to Bob"s question and maybe someone can tell me what's happening.

I have my code like this :


READ MyFile
Proc1 ( DREFNO ) // DREFNO is a field in MyFile


Proc1 B
SRefNo LIKE(aField) CONST

/Free

READ MyFile // The same file

// SRefNo now has the same value as DREFNO from myFile and I have modified a parameter with CONST!


/end-free


* Subject: RE: Another ILE question : CONST vs VALUE
* From: "Bob Cozzi" <bob@xxxxxxxxxxxx>
* Date: Mon, 7 May 2007 11:43:01 -0500

David,

What does this mean?

That way, you can't change the parameter in your program.
YOU can't but your programme certainly can!.

If a parameter is const, the subprocedure can't change it. Certainly the caller
of the subprocedure can modify a field passed to a const parameter, but that's
normal and expected. The use of CONST isn't to prevent a subprocedure from
change the parameter value, but it does allow you to write subprocedure and have
the caller know that the subprocedure won't change the content of their field,
so they can safely pass anything they want without worry.

-Bob Cozzi
www.i5PodCast.com
Ask your manager to watch i5 TV



-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On
Behalf Of Glenn Gundermann
Sent: Monday, May 07, 2007 11:29 AM
To: RPG programming on the AS400 / iSeries
Subject: Re: Another ILE question : CONST vs VALUE

David,

I use CONST for read-only parms. This way I can pass in text (e.g. 'ABC')
without using an intermediate variable, as well as expressions. You must
use CONST in both the caller and called program and then it can't be
changed.

Hope this helps.

Glenn Gundermann
ggundermann@xxxxxx
(647) 272-3295

Here's another one I can't get my head round.

I understand the difference between passing parameters by reference and by
value.

When we started ILE, the powers that be imposed on us the keyword CONST
systematically for all parameters destined to be used as input parameters.

That way, you can't change the parameter in your program. YOU can't but
your programme certainly can!.

Anyone else had this problem? What's the point of using CONST instead of
VALUE apart from performance issues? I'd say that if I see VALUE on a
parameter I'm sure that it wasn't intended to be changed in the procedure.